Molecular sieve abstract
The invention relates to a molecular sieve catalyst composition,
to a method of making or forming the molecular sieve catalyst composition,
and to a conversion process using the catalyst composition. In particular,
the invention is directed to making a formulated molecular sieve
catalyst composition from a slurry of formulation composition of
a synthesized molecular sieve that has not been fully dried, a binder
and an optional matrix material. In a more preferred embodiment,
the weight ratio of the binder to the molecular sieve and/or the
solid content of the slurry is controlled to provide an improved
attrition resistant catalyst composition, particularly useful in
a conversion process for producing olefin(s), preferably ethylene
and/or propylene, from a feedstock, preferably an oxygenate containing
feedstock.
Molecular sieve claims
We claim:
1. A method for formulating a molecular sieve catalyst composition,
the method comprising the steps of: (a) providing a synthesized
molecular sieve synthesized from the combination of at least two
of the group consisting of a silicon source, a phosphorous source
and an aluminum source, optionally in the presence of a templating
agent; (b) matting a slurry of the synthesized molecular sieve,
a binder, and optionally a matrix material, wherein 90 percent by
volume of the slurry contains particles having a diameter less than
20 .mu.m; and (c) forming the slurry to produce a formulated molecular
sieve catalyst composition.
2. The method of claim 1 wherein the slurry comprises in the range
of from 30 percent to 50 percent by weight solid particles.
3. The method of claim 1 wherein, the synthesized molecular sieve
is a silicoaluminophosphate molecular sieve.
4. The method of claim 1 wherein at least 90 percent by volume
of the slurry contains particles having a diameter of less than
10 .mu.m.
5. The method of claim 1 wherein the weight ratio of the binder
to the molecular sieve is in the range of from 0.1 to 0.5.
6. The method of claim 1 wherein the molecular sieve catalyst composition
has a micropore surface area (MSA) on a contained molecular sieve
basis of at least 70% of the MSA of the molecular sieve by itself.
7. The method of claim 1 wherein at least 90 percent by volume
of the slurry contains particles having a diameter of less than
5 .mu.m.
8. The method of claim 1 wherein the slurry in step (c) is formed
by spray drying.
9. The method of claim 1 wherein the method further comprises the
step (d) of calcining the formulated molecular sieve catalyst composition
after step (C).
10. A method for formulating a molecular sieve catalyst composition,
the method comprising the steps of: (a) making a shiny comprising
a solid portion and a liquid portion, the solid portion comprising
a synthesized molecular sieve, a binder, and optionally a matrix
material, and the slurry has a solid content of from about 30 percent
to about 50 percent based on the total weight of the slurry on a
calcined basis; (b) mixing the slurry until at least 90 percent
by volume of the solid portion comprises particles in the slurry
having a diameter less than 20 .mu.m; and, (c) forming the slurry
to produce a formulated molecular sieve catalyst composition.
11. The method of claim 10 wherein the slurry is mixed in step
(b) until at least 90 percent by volume of the solid particles in
the slurry have a diameter of about 5 .mu.m.
12. The method of claim 10 wherein the slurry has a solid content
of from about 35 percent to about 50 percent based on the total
weight of the slurry on a calcined basis.
13. The method of claim 10 wherein the method further comprises
step (d) calcining the formulated molecular sieve catalyst composition.
14. The method of claim 10 wherein the weight ratio of the binder
to the molecular sieve is in the range of from 0.1 to 0.5.
15. The method of claim 10 wherein the molecular sieve catalyst
composition has a micropore surface area (MSA) of at least 80% on
a contained molecular sieve basis of the MSA of the molecular sieve
by itself.
16. The method of claim 10 wherein the synthesized molecular sieve
has not been calcined.
17. The method of claim 10 wherein the weight ratio of to binder
to the molecular sieve is in the range of from 0.12 to 0.45.
18. The method of claim 10 wherein the weight ratio of the binder
to the molecular sieve is in the range of from 0.12 to 0.5 and the
slurry has a solid content of from about 35 percent to about 48
percent based on the total weight of to slurry on a calcined basis.
19. The method of claim 10 wherein the synthesized molecular sieve
is a silicoaluminophosphate.
20. A method for making a formulated molecular sieve catalyst composition,
the method comprising the steps of: (a) making a slurry comprising
a liquid portion and a solid portion, the solid portion comprising
a molecular sieve, a binder, and optionally a matrix material, wherein
the slurry has a solid content of from about 30 percent to about
50 percent based on the total weight of the slurry on a calcined
basis and the weight ratio of the binder to molecular sieve is in
the range of from 0.1 to 0.5; (b) mixing the slimy to form a formulation
composition; (c) forming the formulation composition to for a formulated
catalyst composition.
21. The method of claim 20 wherein in step (b) the slurry is mixed
until at least 90 percent by volume of the formulation composition
comprises solid particles having a diameter of less than 10 .mu.m.
22. The method of claim 20 wherein the slurry comprises in the
range of from 35 percent to 50 percent by weight solid particles.
23. The method of claim 20 wherein slurry is mixed in step (b)
by high shear-mixing.
24. The method of claim 20 wherein the synthesized molecular sieve
is a silicoaluminophosphate, an aluminophosphate and/or a chabazite
framework-type molecular sieve.
25. The method of claim 20 wherein the weight ratio of the binder
to molecular sieve is in the range of from about 0.11 to about 0.45.
26. A slurry comprising a formulation composition for making a
molecular sieve catalyst composition, the formulation composition
comprising: (i) a solid portion comprising solid particles, the
solid particles comprising: (a) a binder, optionally and a matrix
material; and (b) a synthesized molecular sieve; and wherein the
formulation composition has a solid content of from about 30 percent
to about 50 percent based on the total weight of the slurry on a
calcined basis; and (ii) a liquid portion; wherein at least 90 percent
by volume of the solid particles in the solid portion and the liquid
portion have a diameter of less than 20 .mu.m.
27. The slurry of claim 26 wherein the synthesized molecular sieve
has not been dehydrated.
28. The slurry of claim 26 wherein at least 90 percent by volume
the solid particles in the slurry have a diameter of less than 10
.mu.m.
29. The slurry of claim 26 wherein the weight ratio of the binder
to the molecular sieve is in the range of from 0.1 to 0.5.
30. The slurry of claim 26 wherein the molecular sieve catalyst
composition has a micropore surface area (MSA) of at least 80% on
a contained molecular sieve basis of the MSA of the molecular sieve
by itself.
31. The slurry of claim 26 wherein the slurry has a solid content
of from about 35 percent to about 50 percent based on the total
weight of the solid portion in the slurry on a calcined basis.
32. The slurry of claim 26 wherein the synthesized molecular sieve
is synthesized from the combination of at least two of the group
consisting of a silicon source, a phosphorous source and an aluminum
source, optionally in the presence of a templating agent.
33. The slurry of claim 26 wherein the synthesized molecular sieve
has an average particle size of from 0.1 microns to 2 microns.
34. The slurry of claim 26 wherein the formulated molecular sieve
catalyst composition is selected from one or more of the group consisting
of: silicoaluminophosphate, an aluminophosphate and/or a chabazite
framework-type molecular sieve.
35. A formulated molecular sieve catalyst composition made by the
method comprising the steps of (a) forming a formulation composition,
the formulation composition comprising a liquid medium, a binder,
a matrix material and a synthesized molecular sieve, wherein at
least 90 percent by volume of the formulation composition composes
solid particles having a diameter of less than 10 .mu.m; b) spray
drying the formulation composition to form a formulated molecular
sieve catalyst composition; and (c) calcining the formulated molecular
sieve catalyst composition to form the calcined formulated molecular
sieve catalyst composition, wherein the ARI of the formulated molecular
sieve catalyst is in the range of from about 0.01 to 0.5 weight
percent per hour.
36. The formulated molecular sieve catalyst composition of claim
35 wherein the molecular sieve is synthesized from the combination
from at least two of the group consisting of a silicon source, a
phosphorous source and an aluminum source, optionally in the presence
of a templating agent.
37. The formulated molecular sieve catalyst composition of claim
35 wherein the weight ratio of the binder to the molecular sieve
is in the range of from 0.12 to loss than 0.30 and binder is aluminum
chlorhydrol.
Molecular sieve description
FIELD OF THE INVENTION
The present invention relates to a molecular sieve catalyst composition,
to a method of making or forming the molecular sieve catalyst composition,
and to a conversion process using the catalyst composition.
BACKGROUND OF THE INVENTION
Olefins are traditionally produced from petroleum feedstock by
catalytic or steam cracking processes. These cracking processes,
especially steam cracking, produce light olefin(s) such as ethylene
and/or propylene from a variety of hydrocarbon feedstock. Ethylene
and propylene are important commodity petrochemicals useful in a
variety of processes for making plastics and other chemical compounds.
The petrochemical industry has known for some time that oxygenates,
especially alcohols, are convertible into light olefin(s). There
are numerous technologies available for producing oxygenates including
fermentation or reaction of synthesis gas derived from natural gas,
petroleum liquids, carbonaceous materials including coal, recycled
plastics, municipal waste or any other organic material. Generally,
the production of synthesis gas involves a combustion reaction of
natural gas, mostly methane, and an oxygen source into hydrogen,
carbon monoxide and/or carbon dioxide. Syngas production processes
are well known, and include conventional steam reforming, autothermal
reforming, or a combination thereof.
Methanol, the preferred alcohol for light olefin production, is
typically synthesized from the catalytic reaction of hydrogen, carbon
monoxide and/or carbon dioxide in a methanol reactor in the presence
of a heterogeneous catalyst. For example, in one synthesis process
methanol is produced using a copper/zinc oxide catalyst in a water-cooled
tubular methanol reactor. The preferred methanol conversion process
is generally referred to as a methanol-to-olefin(s) process, where
methanol is converted to primarily ethylene and/or propylene in
the presence of a molecular sieve.
Molecular sieves are porous solids having pores of different sizes
such as zeolites or zeolite-type molecular sieves, carbons and oxides.
The most commercially useful molecular sieves for the petroleum
and petrochemical industries are known as zeolites, for example
aluminosilicate molecular sieves. Zeolites in general have a one-,
two- or three-dimensional crystalline pore structure having uniformly
sized pores of molecular dimensions that selectively adsorb molecules
that can enter the pores, and exclude those molecules that are too
large.
There are many different types of molecular sieves well known to
convert a feedstock, especially an oxygenate containing feedstock,
into one or more olefin(s). For example, U.S. Pat. No. 5367100
describes the use of a well known zeolite, ZSM-5 to convert methanol
into olefin(s); U.S. Pat. No. 4062905 discusses the conversion
of methanol and other oxygenates to ethylene and propylene using
crystalline aluminosilicate zeolites, for example Zeolite T, ZK5
erionite and chabazite; U.S. Pat. No. 4079095 describes the use
of ZSM-34 to convert methanol to hydrocarbon products such as ethylene
and propylene; and U.S. Pat. No. 4310440 describes producing light
olefin(s) from an alcohol using a crystalline aluminophosphates,
often represented by ALPO.sub.4.
One of the most useful molecular sieves for converting methanol
to olefin(s) is a silicoaluminophosphate molecular sieves. Silicoaluminophosphate
(SAPO) molecular sieves contain a three-dimensional microporous
crystalline framework structure of [SiO.sub.2 ], [AlO.sub.2 ] and
[PO.sub.2 ] corner sharing tetrahedral units. SAPO synthesis is
described in U.S. Pat. No. 4440871 which is herein fully incorporated
by reference. SAPO is generally synthesized by the hydrothermal
crystallization of a reaction mixture of silicon-, aluminum- and
phosphorus-sources and at least one templating agent. Synthesis
of a SAPO molecular sieve, its formulation into a SAPO catalyst,
and its use in converting a hydrocarbon feedstock into olefin(s),
particularly where the feedstock is methanol, is shown in U.S. Pat.
Nos. 4499327 4677242 4677243 4873390 5095163 5714662
and 6166282 all of which are herein fully incorporated by reference.
Typically, molecular sieves are formed into molecular sieve catalyst
compositions to improve their durability in commercial conversion
processes. The collisions within a commercial process between catalyst
composition particles themselves, the reactor walls, and other reactor
systems cause the particles to breakdown into smaller particles
called fines. The physical breakdown of the molecular sieve catalyst
composition particles is known as attrition. Fines often exit the
reactor in the effluent stream resulting in problems in recovery
systems. Catalyst compositions having a higher resistance to attrition
generate fewer fines, less catalyst composition is required for
conversion, and longer life times result in lower operating costs.
Molecular sieve catalyst compositions are formed by combining a
molecular sieve and a matrix material usually in the presence of
a binder. The purpose of the binder is hold the matrix material,
often a clay, to the molecular sieve. The use of binders and matrix
materials in the formation of molecular sieve catalyst compositions
is well known for a variety of commercial processes. It is also
known that the way in which the molecular sieve catalyst composition
is made or formulated affects catalyst composition attrition.
Example of methods of making catalyst compositions include: U.S.
Pat. No. 5126298 discusses a method for making a cracking catalyst
having high attrition resistance by combining two different clay
particles in separate slurries with a zeolite slurry and a source
of phosphorous, and spray drying a mixture of the slurries having
a pH below 3; U.S. Pat. Nos. 4987110 and 5298153 relates to
a catalytic cracking process using a spray dried attrition resistant
catalyst containing greater than 25 weight percent molecular sieve
dispersed in a clay matrix with a synthetic silica-alumina component;
U.S. Pat. Nos. 5194412 and 5286369 discloses forming a catalytic
cracking catalyst of a molecular sieve and a crystalline aluminum
phosphate binder having a surface area less than 20 m.sup.2 /g and
a total pore volume less than 0.1 cc/g; U.S. Pat. No. 4542118
relates to forming a particulate inorganic oxide composite of a
zeolite and aluminum chlorhydrol that is reacted with ammonia to
form a cohesive binder; U.S. Pat. No. 6153552 claims a method
of making a catalyst, by drying a slurry of a SAPO molecular sieve,
an inorganic oxide sol, and an external phosphorous source; U.S.
Pat. No. 5110776 illustrates the formation of a zeolite containing
catalytic catalyst by modifying the zeolite with a phosphate containing
solution; U.S. Pat. No. 5348643 relates to spray drying a zeolite
slurry with a clay and source of phosphorous at a pH of below 3;
U.S. Pat. No. 4973792 is directed to a conversion process using
a formulated molecular sieve catalyst composition, however, there
is no mention of the solid content of the slurry spray dried, nor
any discussion of the amount of liquid medium in the SAPO-34 added
to the slurry; U.S. patent application Ser. No. 09/891674 filed
Jun. 25 2001 discusses a method for steaming a molecular sieve
to remove halogen; U.S. Pat. No. 5248647 illustrates spray drying
a SAPO-34 molecular sieve admixed with kaolin and a silica sol;
U.S. Pat. No. 5346875 discloses a method for making a catalytic
cracking catalyst by matching the isoelectric point of each component
of the framework structure to the pH of the inorganic oxide sol;
Maurer, et al, Aggregation and Peptization Behavior of Zeolite Crystals
in Sols and Suspensions, Ind. Eng. Chem. Vol. 40 pages 2573-2579
2001 discusses zeolite aggregation at or near the isoelectric point;
Woltermann, et.al, Chapter 4 Commercial Preparation and Characterization
of FCC Catalysts from page 105 from Fluid Catalytic Cracking: Science
and Technology, Volume 76 Studies in Surface Sciences and Catalysis,
Elsevier Science Publishers, B.V., 1993 discusses influence of milling
a slurry of containing a FCC catalyst to reduce particle size that
is shown to reduce relative FCC attrition, however, the viscosity
and temperature of the slurry is increased requiring the use of
surfactants and cooling the slurry: there is no mention of the solids
content of the slurry; PCT Publication WO 99/21651 describes making
a catalyst by drying a mixture of an alumina sol and a SAPO molecular
sieve, however, there is no mention of the particle size of the
solids in the mixture; PCT Publication WO 02/05950 describes making
a catalyst composition of a molecular sieve containing attrition
particles with fresh molecular sieve; and WO 02/05952 discloses
a crystalline metallo-aluminophosphate molecular sieve and a matrix
material of an inorganic oxide binder and filler where the molecular
sieve is present in an amount less than 40 weight percent relative
to the catalyst weight and a preferable weight ratio of the binder
to molecular sieve close to 1.
Although these molecular sieve catalyst compositions described
above are useful in hydrocarbon conversion processes, it would be
desirable to have an improved molecular sieve catalyst composition
having better attrition resistance and commercially desirable operability
and cost advantages.
SUMMARY OF THE INVENTION
This invention provides for a method of making or formulating a
molecular sieve catalyst composition and to its use in a conversion
process for converting a feedstock into one or more olefin(s).
In one embodiment the invention is directed to a method for formulating
a molecular sieve catalyst composition, the method comprising the
steps of: (a) providing a synthesized molecular sieve; (b) making
a slurry of the synthesized molecular sieve, a binder, and optionally
a matrix material, wherein 90 percent by volume of the slurry contains
particles having a diameter less than 20 .mu.m, preferably less
than 15 .mu.m, more preferably less than 10 .mu.m, and most preferably
about 5 .mu.m and (c) forming the slurry to produce a formulated
molecular sieve catalyst composition. In a preferred embodiment,
the synthesized molecular sieve is synthesized from the combination
of at least two of the group consisting of a silicon source, a phosphorous
source and an aluminum source, optionally in the presence of a templating
agent. In a most preferred embodiment, the slurry in step (c) is
formed by spray drying. In another preferred embodiment, the weight
ratio of binder to molecular sieve in the slurry in step (c) is
greater than 0.12 to about 0.45. In yet another embodiment, the
slurry contains a solid content of from about 20 percent to about
80 percent based on the total weight of the slurry on a calcined
basis. The solids include the molecular sieve, the binder, and optionally
the matrix material. In still another embodiment of any of the above,
the synthesized molecular sieve is not calcined.
In an embodiment, the invention is directed to a method for formulating
a molecular sieve catalyst composition, the method comprising the
steps of: (a) making a slurry comprising a solid portion and a liquid
portion, the solid portion comprising a synthesized molecular sieve,
a binder, and optionally a matrix material, and the slurry has a
solid content of from about 30 percent to about 50 percent based
on the total weight of the solid portion in the slurry on a calcined
basis; (b) mixing the slurry until at least 90 percent by volume
of the solid portion comprises particles in the slurry having a
diameter less than 20 .mu.m; and, (c) forming the slurry to produce
a formulated molecular sieve catalyst composition. In another preferred
embodiment, in step (b) the slurry is mixed until at least 90 percent
by volume of solid portion comprises particles having a diameter
less than less than 10 .mu.m, more preferably less than about 5
.mu.m. Preferably the synthesized molecular sieve is a silicoaluminophosphate,
an aluminophosphate and/or a chabazite (CHA) framework-type molecular
sieve. In yet another embodiment, the weight ratio of the binder
to the molecular sieve is greater than 0.12 to less than 0.45 wherein
the binder is an alumina and the molecular sieve is a silicoaluminophosphate.
In yet another embodiment, the slurry contains a solid content of
from about 30 percent to about 50 percent, preferably about 35 percent
to about 50 percent, and more preferably from about 40 to about
50 percent, based on the total weight of the slurry on a calcined
basis. In still yet another embodiment of any of the above, the
synthesized molecular sieve that has not been dehydrated.
In another preferred embodiment, the invention relates to a method
for making a formulated molecular sieve catalyst composition, the
method comprising the steps of: (a) making a slurry comprising a
liquid portion and a solid portion, the solid portion comprising
a molecular sieve, a binder, and optionally a matrix material, wherein
the slurry has a solid content of from about 30 percent to about
50 percent based on the total weight of the slurry on a calcined
basis and the weight ratio of the binder to molecular sieve is in
the range of from 0.1 to 0.5; (b) mixing the slurry to form a formulation
composition; (c) forming the formulation composition to for a formulated
catalyst composition. In another preferred embodiment, the method
further comprises a step (d) in which the formulated molecular sieve
catalyst composition is calcined. In another embodiment, the weight
ratio of the binder to the molecular sieve is in the range of greater
than 0.1 to less than 0.5 preferably in the range greater than
0.12 to 0.45 and most preferably in the range of from 0.13 to about
0.40. In still another embodiment, the slurry is mixed in step (b)
until at least 90 percent by volume of particles in the solid portion
have a diameter less than 20 .mu.m, preferably less than 10 .mu.m,
more preferably less than about 5 .mu.m, and most preferably in
the range of from about 5 .mu.m to about 10 .mu.m.
In yet another embodiment, the invention is directed to a process
for producing olefin(s) in the presence of any of the above formulated
molecular sieve catalyst compositions. In particular, the process
involves producing olefin(s) in a process for converting a feedstock,
preferably a feedstock containing an oxygenate, more preferably
a feedstock containing an alcohol, and most preferably a feedstock
containing methanol in the presence of one or more of the formulated
molecular sieve catalyst compositions discussed above.
DETAILED DESCRIPTION OF THE INVENTION
Introduction
The invention is directed toward a molecular sieve catalyst composition,
its making, and to its use in the conversion of a hydrocarbon feedstock
into one or more olefin(s). Typically, a formulated molecular sieve
catalyst composition formed from a slurry of the combination of
a molecular sieve, a binder, and optionally, most preferably, a
matrix material. It has been discovered that the amount of solids,
the molecular sieve, the binder and the optional matrix material,
present in the slurry is important, particular for use in a spray
drying process. When the solids content of the slurry is too low
or too high the attrition resistance property of the formulated
molecular sieve catalyst composition is reduced.
In addition it has also been discovered that it is important that
the solid particles in the slurry are of a particular size, more
particularly, that at least 90 percent by volume of particles in
the solid portion of the slurry have a diameter less than 20 .mu.m,
preferably less than 15 .mu.m, more preferably less than 10 .mu.m,
and most preferably about 51 .mu.m. In yet another embodiment, the
solid particles in the slurry are of a particular size, more particularly,
that at least 90 percent by volume of particles in the solid portion
of the slurry have a diameter in the range of from less than 20
.mu.m to greater than 2 .mu.m, and preferably in the range of from
greater than 4 .mu.m to about 10 .mu.m. One way in which this slurry
characteristic, otherwise termed the d.sub.90 of the solid particles
in the slurry, is achieved is by mixing the slurry, preferably where
the mixing is high-shear mixing. This important finding alone or
combination with the above provides for a method of making a attrition
resistant formulated molecular sieve catalyst composition.
It has been known in the art that varying the weight percent of
the molecular sieve in the total catalyst composition is important.
However, it has also been surprisingly found that the weight ratio
of the binder to the molecular sieve, especially where the molecular
sieve is partially dried as discussed above, is important to making
or forming an attrition resistance catalyst composition. Without
being bound to any particular theory it is believed that when the
weight ratio of the binder to molecular sieve is too high then the
surface area of the catalyst composition decreases resulting in
lower conversion rates, and when the weight ratio of the binder
to molecular sieve is too low then the catalyst composition will
break apart into fines more easily. Therefore, in addition to the
solids content in the slurry and/or the d.sub.90 of the particles
in the slurry discussed above, using the appropriate binder to molecular
sieve ratio, an enhanced attrition resistance formulated molecular
sieve catalyst composition is formed.
In addition, alone, preferably in combination with one or more
of the above advantages, it has been further surprisingly found
that using a molecular sieve that has not been fully dried that
is combined with a binder and/or a matrix material an improved formulated
molecular sieve catalyst composition is made. In particular, using
a partially dried molecular sieve with a binder and/or a matrix
material results in making a formulated molecular sieve catalyst
composition having improved resistance to attrition. This results
in an improved catalyst composition more resistant to breaking apart
in a conversion process, and therefore having an extended catalyst
life. Additionally, not calcining the molecular sieve after its
synthesis also reduces the cost associated with the synthesis and
also improves its susceptibility to deactivation especially in its
storage or transportation.
Molecular Sieves and Catalysts Thereof
Molecular sieves have various chemical and physical, framework,
characteristics. Molecular sieves have been well classified by the
Structure Commission of the International Zeolite Association according
to the rules of the IUPAC Commission on Zeolite Nomenclature. A
framework-type describes the connectivity, topology, of the tetrahedrally
coordinated atoms constituting the framework, and making an abstraction
of the specific properties for those materials. Framework-type zeolite
and zeolite-type molecular sieves for which a structure has been
established, are assigned a three letter code and are described
in the Atlas of Zeolite Framework Types, 5th edition, Elsevier,
London, England (2001), which is herein fully incorporated by reference.
Non-limiting examples of these molecular sieves are the small pore
molecular sieves, AEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA,
CHI, DAC, DDR, EDI, ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI,
RHO, ROG, THO, and substituted forms thereof, the medium pore molecular
sieves, AFO, AEL, EUO, HEU, FER, MEL, MFI, MTW, MTT, TON, and substituted
forms thereof; and the large pore molecular sieves, EMT, FAU, and
substituted forms thereof. Other molecular sieves include ANA, BEA,
CFI, CLO, DON, GIS, LTL, MER, MOR, MWW and SOD. Non-limiting examples
of the preferred molecular sieves, particularly for converting an
oxygenate containing feedstock into olefin(s), include AEL, AFY,
BEA, CHA, EDI, FAU, FER, GIS, LTA, LTL, MER, MFI, MOR, MTT, MWW,
TAM and TON. In one preferred embodiment, the molecular sieve of
the invention has an AEI framework-type or a CHA framework-type,
or a combination thereof, most preferably a CHA framework-type.
Molecular sieve materials all have 3-dimensional framework structure
of corner-sharing TO.sub.4 tetrahedra, where T is any tetrahedrally
coordinated cation. These molecular sieves are typically described
in terms of the size of the ring that defines a pore, where the
size is based on the number of T atoms in the ring. Other framework-type
characteristics include the arrangement of rings that form a cage,
and when present, the dimension of channels, and the spaces between
the cages. See van Bekkum, et al., Introduction to Zeolite Science
and Practice, Second Completely Revised and Expanded Edition, Volume
137 pages 1-67 Elsevier Science, B.V., Amsterdam, Netherlands
(2001).
The small, medium and large pore molecular sieves have from a 4-ring
to a 12-ring or greater framework-type. In a preferred embodiment,
the zeolitic molecular sieves have 8-, 10- or 12-ring structures
or larger and an average pore size in the range of from about 3
.ANG. to 15 .ANG.. In the most preferred embodiment, the molecular
sieves of the invention, preferably silicoaluminophosphate molecular
sieves have 8-rings and an average pore size less than about 5 .ANG.,
preferably in the range of from 3 .ANG. to about 5 .ANG., more preferably
from 3 .ANG. to about 4.5 .ANG., and most preferably from 3.5 .ANG.
to about 4.2 .ANG..
Molecular sieves, particularly zeolitic and zeolitic-type molecular
sieves, preferably have a molecular framework of one, preferably
two or more corner-sharing [TO.sub.4 ] tetrahedral units, more preferably,
two or more [SiO.sub.4 ], [AlO.sub.4 ] and/or [PO.sub.4 ] tetrahedral
units, and most preferably [SiO.sub.4 ], [AlO.sub.4 ] and [PO.sub.4
] tetrahedral units. These silicon, aluminum, and phosphorous based
molecular sieves and metal containing silicon, aluminum and phosphorous
based molecular sieves have been described in detail in numerous
publications including for example, U.S. Pat. No. 4567029 (MeAPO
where Me is Mg, Mn, Zn, or Co), U.S. Pat. No. 4440871 (SAPO),
European Patent Application EP-A-0 159 624 (ELAPSO where El is As,
Be, B, Cr, Co, Ga, Ge, Fe, Li, Mg, Mn, Ti or Zn), U.S. Pat. No.
4554143 (FeAPO), U.S. Pat. Nos. 4822478 4683217 4744885
(FeAPSO), EP-A-0 158 975 and U.S. Pat. No. 4935216 (ZNAPSO, EP-A-0
161 489 (CoAPSO), EP-A-0 158 976 (ELAPO, where EL is Co, Fe, Mg,
Mn, Ti or Zn), U.S. Pat. No. 4310440 (AlPO.sub.4), EP-A-0 158
350 (SENAPSO), U.S. Pat. No. 4973460 (LiAPSO), U.S. Pat. No. 4789535
(LiAPO), U.S. Pat. No. 4992250 (GeAPSO), U.S. Pat. No. 4888167
(GeAPO), U.S. Pat. No. 5057295 (BAPSO), U.S. Pat. No. 4738837
(CrAPSO), U.S. Pat. Nos. 4759919 and 4851106 (CrAPO), U.S.
Pat. Nos. 4758419 4882038 5434326 and 5478787 (MgAPSO),
U.S. Pat. No. 4554143 (FeAPO), U.S. Pat. No. 4894213 (AsAPSO),
U.S. Pat. No. 4913888 (AsAPO), U.S. Pat. Nos. 4686092 4846956
and 4793833 (MnAPSO), U.S. Pat. Nos. 5345011 and 6156931 (MnAPO),
U.S. Pat. No. 4737353 (BeAPSO), U.S. Pat. No. 4940570 (BeAPO),
U.S. Pat. Nos. 4801309 4684617 and 4880520 (TiAPSO), U.S.
Pat. Nos. 4500651 4551236 and 4605492 (TiAPO), U.S. Pat.
Nos. 4824554 4744970 (CoAPSO), U.S. Pat. No. 4735806 (GaAPSO)
EP-A-0 293 937 (QAPSO, where Q is framework oxide unit [QO.sub.2
]), as well as U.S. Pat. Nos. 4567029 4686093 4781814 4793984
4801364 4853197 4917876 4952384 4956164 4956165
4973785 5241093 5493066 and 5675050 all of which are
herein fully incorporated by reference. Other molecular sieves are
described in R. Szostak, Handbook of Molecular Sieves, Van Nostrand
Reinhold, New York, N.Y. (1992), which is herein fully incorporated
by reference.
The more preferred silicon, aluminum and/or phosphorous containing
molecular sieves, and aluminum, phosphorous, and optionally silicon,
containing molecular sieves include aluminophosphate (ALPO) molecular
sieves and silicoaluminophosphate (SAPO) molecular sieves and substituted,
preferably metal substituted, ALPO and SAPO molecular sieves. The
most preferred molecular sieves are SAPO molecular sieves, and metal
substituted SAPO molecular sieves. In an embodiment, the metal is
an alkali metal of Group IA of the Periodic Table of Elements, an
alkaline earth metal of Group IIA of the Periodic Table of Elements,
a rare earth metal of Group IIIB, including the Lanthanides: lanthanum,
cerium, praseodymium, neodymium, samarium, europium, gadolinium,
terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium;
and scandium or yttrium of the Periodic Table of Elements, a transition
metal of Groups IVB, VB, VIB, VIIB, VIIIB, and IB of the Periodic
Table of Elements, or mixtures of any of these metal species. In
one preferred embodiment, the metal is selected from the group consisting
of Co, Cr, Cu, Fe, Ga, Ge, Mg, Mn, Ni, Sn, Ti, Zn and Zr, and mixtures
thereof. In another preferred embodiment, these metal atoms discussed
above are inserted into the framework of a molecular sieve through
a tetrahedral unit, such as [MeO.sub.2 ], and carry a net charge
depending on the valence state of the metal substituent. For example,
in one embodiment, when the metal substituent has a valence state
of +2 +3 +4 +5 or +6 the net charge of the tetrahedral unit
is between -2 and +2.
In one embodiment, the molecular sieve, as described in many of
the U.S. patents mentioned above, is represented by the empirical
formula, on an anhydrous basis:
wherein R represents at least one templating agent, preferably
an organic templating agent; m is the number of moles of R per mole
of (M.sub.x Al.sub.y P.sub.z)O.sub.2 and m has a value from 0 to
1 preferably 0 to 0.5 and most preferably from 0 to 0.3; x, y,
and z represent the mole fraction of M, Al and P as tetrahedral
oxides, where M is a metal selected from one of Group IA, IIA, IB,
IIIB, IVB, VB, VIB, VIIB, VIIIB and Lanthanide's of the Periodic
Table of Elements, preferably M is selected from one of the group
consisting of Co, Cr, Cu, Fe, Ga, Ge, Mg, Mn, Ni, Sn, Ti, Zn and
Zr. In an embodiment, m is greater than or equal to 0.2 and x,
y and z are greater than or equal to 0.01. In another embodiment,
m is greater than 0.1 to about 1 x is greater than 0 to about 0.25
y is in the range of from 0.4 to 0.5 and z is in the range of from
0.25 to 0.5 more preferably m is from 0.15 to 0.7 x is from 0.01
to 0.2 y is from 0.4 to 0.5 and z is from 0.3 to 0.5.
Non-limiting examples of SAPO and ALPO molecular sieves of the
invention include one or a combination of SAPO-5 SAPO-8 SAPO-11
SAPO-16 SAPO-17 SAPO-18 SAPO-20 SAPO-31 SAPO-34 SAPO-35 SAPO-36
SAPO-37 SAPO-40 SAPO-41 SAPO-42 SAPO-44 (U.S. Pat. No. 6162415),
SAPO-47 SAPO-56 ALPO-5 ALPO-11 ALPO-18 ALPO-31 ALPO-34 ALPO-36
ALPO-37 ALPO-46 and metal containing molecular sieves thereof.
The more preferred zeolite-type molecular sieves include one or
a combination of SAPO-18 SAPO-34 SAPO-35 SAPO-44 SAPO-56 ALPO-18
and ALPO-34 even more preferably one or a combination of SAPO-18
SAPO-34 ALPO-34 and ALPO-18 and metal containing molecular sieves
thereof, and most preferably one or a combination of SAPO-34 and
ALPO-18 and metal containing molecular sieves thereof.
In an embodiment, the molecular sieve is an intergrowth material
having two or more distinct phases of crystalline structures within
one molecular sieve composition. In particular, intergrowth molecular
sieves are described in the U.S. patent application Ser. No. 09/924016
filed Aug. 7 2001 and PCT WO 98/15496 published Apr. 16 1998
both of which are herein fully incorporated by reference. For example,
SAPO-18 ALPO-18 and RUW-18 have an AEI framework-type, and SAPO-34
has a CHA framework-type. In another embodiment, the molecular sieve
comprises at least one intergrown phase of AEI and CHA framework-types,
preferably the molecular sieve has a greater amount of CHA framework-type
to AEI framework-type, and more preferably the ratio of CHA to AEI
is greater than 1:1.
Molecular Sieve Synthesis
The synthesis of molecular sieves is described in many of the references
discussed above. Generally, molecular sieves are synthesized by
the hydrothermal crystallization of one or more of a source of aluminum,
a source of phosphorous, a source of silicon, a templating agent,
and a metal containing compound. Typically, a combination of sources
of silicon, aluminum and phosphorous, optionally with one or more
templating agents and/or one or more metal containing compounds
are placed in a sealed pressure vessel, optionally lined with an
inert plastic such as polytetrafluoroethylene, and heated, under
a crystallization pressure and temperature, until a crystalline
molecular sieve material is formed, and then recovered by filtration,
centrifugation and/or decanting.
For purposes of this patent application and appended claims, the
term "not being fully dried" is defined to include no
drying up to not calcining the crystalline molecular sieve material
or the synthesized molecular sieve.
For purposes of this patent application and appended claims, the
term "partially dried" is defined to include drying the
crystalline molecular sieve material or the synthesized molecular
sieve to a level wherein after drying the amount of templating agent
with the crystalline molecular sieve material or the synthesized
molecular sieve is in the range of from about 50 weight percent,
preferably about 60 weight percent, more preferably about 70 weight
percent, and most preferably about 80 percent to 100 weight percent
of the original amount of templating agent used to form the crystalline
molecular sieve material or the synthesized molecular sieve originally.
In another preferred embodiment, the crystalline molecular sieve
material or synthesized molecular sieve is wet, preferably with
water, when used in the formulation of a molecular sieve catalyst
composition and is termed a "wet filtercake".
In one particular embodiment, the crystalline molecular sieve material
or the synthesized molecular sieve is optionally dried, preferably
in air, to a level such that the synthesized molecular sieve has
in the range of from about 0 weight percent to about 80 weight percent
liquid, preferably where the liquid is water, based on the total
weight of the synthesized molecular sieve and liquid, preferably
the range is from greater than 5 weight percent to about 70 weight
percent, more preferably from about 10 weight percent to about 70
weight percent, and most preferably from about 20 weight percent
to about 60 weight percent.
Determination of the percentage of liquid or liquid medium and
the percentage of template for purposes of this patent specification
and appended claims uses a Thermal Gravimetric Analysis (TGA) technique
as follows: An amount a SAPO-34 molecular sieve material, the sample,
is loaded into a sample pan of a Cahn TG-121 Microbalance, available
from Cahn Instrument, Inc., Cerritos, Calif. During the TGA technique,
a flow of 114 cc/min (STP) air was used. The sample is then heated
from 25.degree. C. to 180.degree. C. at 30.degree. C./min, held
at 180.degree. C. for 3 hours or until the weight of this sample
becomes constant. The weight loss the percentage to the starting
SAPO-34 molecular sieve material is then treated as the percentage
of the liquid or liquid medium. Subsequently, the sample is heated
at 30.degree. C./min from 180.degree. C. to 650.degree. C. and held
at 650.degree. C. for 2 hours. This weight loss as a percentage
of the original sample weight during this treatment is regarded
as the weight loss of the templating agent. The total weight loss
as a percentage in terms of the original first sample weight during
this entire TGA treatment is defined as Loss-On-Ignition (LOI).
In a preferred embodiment, the crystalline molecular sieve or synthesized
molecular sieve is used directly without dehydration after synthesis,
and then forming the slurry of the crystalline molecular sieve or
synthesized molecular sieve, binder, and optional matrix material,
and then formulate the slurry into the molecular sieve catalyst
composition of the invention.
In a preferred embodiment the molecular sieves are synthesized
by forming a reaction product of a source of silicon, a source of
aluminum, a source of phosphorous, an organic templating agent,
preferably a nitrogen containing organic templating agent. This
particularly preferred embodiment results in the synthesis of a
silicoaluminophosphate crystalline material that is then isolated
by filtration, centrifugation and/or decanting.
Non-limiting examples of silicon sources include silicates, fumed
silica, for example, Aerosil-200 available from Degussa Inc., New
York, N.Y., and CAB-O-SIL M-5 silicon compounds such as tetraalkyl
orthosilicates, for example, tetramethyl orthosilicate (TMOS) and
tetraethylorthosilicate (TEOS), colloidal silicas or aqueous suspensions
thereof, for example Ludox-HS-40 sol available from E. I. du Pont
de Nemours, Wilmington, Del., silicic acid, alkali-metal silicate,
or any combination thereof. The preferred source of silicon is a
silica sol.
Non-limiting examples of aluminum sources include aluminum-containing
compositions such as aluminum alkoxides, for example aluminum isopropoxide,
aluminum phosphate, aluminum hydroxide, sodium aluminate, pseudo-boehmite,
gibbsite and aluminum trichloride, or any combinations thereof.
A preferred source of aluminum is pseudo-boehmite, particularly
when producing a silicoaluminophosphate molecular sieve.
Non-limiting examples of phosphorous sources, which may also include
aluminum-containing phosphorous compositions, include phosphorous-containing,
inorganic or organic, compositions such as phosphoric acid, organic
phosphates such as triethyl phosphate, and crystalline or amorphous
aluminophosphates such as ALPO.sub.4 phosphorous salts, or combinations
thereof. The preferred source of phosphorous is phosphoric acid,
particularly when producing a silicoaluminophosphate.
Templating agents are generally compounds that contain elements
of Group VA of the Periodic Table of Elements, particularly nitrogen,
phosphorus, arsenic and antimony, more preferably nitrogen or phosphorous,
and most preferably nitrogen. Typical templating agents of Group
VA of the Periodic Table of elements also contain at least one alkyl
or aryl group, preferably an alkyl or aryl group having from 1 to
10 carbon atoms, and more preferably from 1 to 8 carbon atoms. The
preferred templating agents are nitrogen-containing compounds such
as amines and quaternary ammonium compounds.
The quaternary ammonium compounds, in one embodiment, are represented
by the general formula R.sub.4 N.sup.+, where each R is hydrogen
or a hydrocarbyl or substituted hydrocarbyl group, preferably an
alkyl group or an aryl group having from 1 to 10 carbon atoms. In
one embodiment, the templating agents include a combination of one
or more quaternary ammonium compound(s) and one or more of a mono-,
di- or tri-amine.
Non-limiting examples of templating agents include tetraalkyl ammonium
compounds including salts thereof such as tetramethyl ammonium compounds
including salts thereof, tetraethyl ammonium compounds including
salts thereof, tetrapropyl ammonium including salts thereof, and
tetrabutylammonium including salts thereof, cyclohexylamine, morpholine,
di-n-propylamine (DPA), tripropylamine, triethylamine (TEA), triethanolamine,
piperidine, cyclohexylamine, 2-methylpyridine, N,N-dimethylbenzylamine,
N,N-diethylethanolamine, dicyclohexylamine, N,N-dimethylethanolamine,
choline, N,N'-dimethylpiperazine, 14-diazabicyclo(222)octane,
N',N',N,N-tetramethyl-(16)hexanediamine, N-methyldiethanolamine,
N-methyl-ethanolamine, N-methyl piperidine, 3-methyl-piperidine,
N-methylcyclohexylamine, 3-methylpyridine, 4-methyl-pyridine, quinuclidine,
N,N'-dimethyl-14-diazabicyclo(222) octane ion; di-n-butylamine,
neopentylamine, di-n-pentylamine, isopropylamine, t-butyl-amine,
ethylenediamine, pyrrolidine, polyethylenimine and 2-imidazolidone.
The preferred templating agent or template is a tetraethylammonium
compound, such as tetraethyl ammonium hydroxide (TEAOH), tetraethyl
ammonium phosphate, tetraethyl ammonium fluoride, tetraethyl ammonium
bromide, tetraethyl ammonium chloride and tetraethyl ammonium acetate.
The most preferred templating agent is tetraethyl ammonium hydroxide
and salts thereof, particularly when producing a silicoaluminophosphate
molecular sieve. In one embodiment, a combination of two or more
of any of the above templating agents is used in combination with
one or more of a silicon-, aluminum-, and phosphorous-source.
A synthesis mixture containing at a minimum a silicon-, aluminum-,
and/or phosphorous-composition, and a templating agent, should have
a pH in the range of from 2 to 10 preferably in the range of from
4 to 9 and most preferably in the range of from 5 to 8. Generally,
the synthesis mixture is sealed in a vessel and heated, preferably
under autogenous pressure, to a temperature in the range of from
about 80.degree. C. to about 250.degree. C., and more preferably
from about 150.degree. C. to about 180.degree. C. The time required
to form the crystalline product is typically from immediately up
to several weeks, the duration of which is usually dependent on
the temperature; the higher the temperature the shorter the duration.
Typically, the crystalline molecular sieve product is formed, usually
in a slurry state, and is recovered by any standard technique well
known in the art, for example centrifugation or filtration.
In a preferred embodiment, the isolated or separated crystalline
product, the synthesized molecular sieve, is washed, typically using
a liquid such as water, from one to many times, or in a semi-continuous
or continuous way for variable lengths of time. The washed crystalline
product is then optionally dried, preferably in air to a level such
that the crystalline product or synthesized molecular sieve has
in the range of from about 0 weight percent to about 80 weight percent
liquid, preferably were the liquid is water, based on the total
weight of the crystalline product or synthesized molecular sieve
and liquid medium, preferably the range is from about greater than
1 weight percent to about 80 weight percent, more preferably from
about 10 weight percent to about 70 weight percent, even more preferably
from about 20 to about 60 weight percent, and most preferably from
about 40 weight percent to about 60 weight percent. This liquid
containing crystalline product, synthesized molecular sieve or wet
filtercake, is then used below in the formulation of the molecular
sieve catalyst composition of the invention.
In one embodiment, where the synthesized molecular sieve is partially
dried, for example by heating, the temperature and time period is
sufficient to maintain a major of the templating agent, where more
than 50% of the templating agent is retained. In addition a preferred
temperature for heating the synthesized molecular sieve is typically
about 180.degree. C., preferably less than 150.degree. C., even
more preferably less than 120.degree. C. for about 3 hours or less.
Molecular sieves have either a high silicon (Si) to aluminum (Al)
ratio or a low silicon to aluminum ratio, however, a low Si/Al ratio
is preferred for SAPO synthesis. In one embodiment, the molecular
sieve has a Si/Al ratio less than 0.65 preferably less than 0.40
more preferably less than 0.32 and most preferably less than 0.20.
In another embodiment the molecular sieve has a Si/Al ratio in the
range of from about 0.65 to about 0.10 preferably from about 0.40
to about 0.10 more preferably from about 0.32 to about 0.10 and
more preferably from about 0.32 to about 0.15.
Method for Making Molecular Sieve Catalyst Compositions
Once the molecular sieve is synthesized as described above, depending
on the requirements of the particular conversion process, the molecular
sieve is then formulated into a molecular sieve catalyst composition,
particularly for commercial use. The molecular sieves synthesized
above are made or formulated into molecular sieve catalyst compositions
by combining the synthesized molecular sieve(s) with a binder and
optionally, but preferably, a matrix material to form a formulation
composition. This formulation composition is formed into useful
shape and sized particles by well-known techniques such as spray
drying, pelletizing, extrusion, and the like, spray drying being
the most preferred. It is also preferred that after spray drying
for example that the formulation composition is then calcined.
In one embodiment, the weight ratio of the binder to the molecular
sieve is in the range of from about 0.1 to 0.5 preferably in the
range of from 0.1 to less than 0.5 more preferably in the range
of from 0.11 to 0.48 even more preferably from 0.12 to about 0.45
yet even more preferably from 0.13 to less than 0.45 and most preferably
in the range of from 0.15 to about 0.4. In another embodiment, the
weight ratio of the binder to the molecular sieve is in the range
of from 0.11 to 0.45 preferably in the range of from about 0.12
to less than 0.40 more preferably in the range of from 0.15 to
about 0.35 and most preferably in the range of from 0.2 to about
0.3. All values between these ranges are included in this patent
specification.
In another embodiment, the molecular sieve catalyst composition
or formulated molecular sieve catalyst composition has a micropore
surface area (MSA) measured in m.sup.2 /g-molecular sieve that is
about 70 percent, preferably about 75 percent, more preferably 80
percent, even more preferably 85 percent, and most preferably about
90 percent of the MSA of the molecular sieve itself. The term "MSA
on a contained sieve basis of the molecular sieve by itself"
or the term "MSA of X m.sup.2 /g-molecular sieve" means
that the calculated MSA of a molecular sieve catalyst composite
is the measured MSA divided by the contained fraction of the molecular
sieve. For example, a molecular sieve catalyst composite with a
measured MSA of 200 m.sup.2 /g and containing 40% molecular sieve
would be calculated to have an "MSA on a contained sieve basis
of the molecular sieve by itself" of 200 m.sup.2 /g/0.4=500
m.sup.2 /g-contained molecular sieve.
In one embodiment, the catalyst composition has a MSA on a contained
molecular sieve basis of the molecular sieve by itself in the range
of from 400 m.sup.2 /g-molecular sieve to about 600 m.sup.2 /g-molecular
sieve, preferably an MSA in the range of from 425 m.sup.2 /g-molecular
sieve to about 575 m.sup.2 /g-molecular, more preferably in the
range of from 425 m.sup.2 /g-molecular sieve to about 550 m.sup.2
/g-molecular sieve, and most preferably in the range of from about
450 m.sup.2 /g-molecular sieve to about 550 m.sup.2 /g-molecular
sieve.
There are many different binders that are useful in forming the
molecular sieve catalyst composition. Non-limiting examples of binders
that are useful alone or in combination include various types of
hydrated alumina, silicas, and/or other inorganic oxide sol. One
preferred alumina containing sol is aluminum chlorhydrate. The inorganic
oxide sol acts like glue binding the synthesized molecular sieves
and other materials such as the matrix together, particularly after
thermal treatment. Upon heating, the inorganic oxide sol, preferably
having a low viscosity, is converted into an inorganic oxide matrix
component. For example, an alumina sol will convert to an aluminum
oxide matrix following heat treatment.
Aluminum chlorhydrate, a hydroxylated aluminum based sol containing
a chloride counter ion, has the general formula of Al.sub.m O.sub.n
(OH).sub.o Cl.sub.p.x(H.sub.2 O) wherein m is 1 to 20 n is 1 to
8 o is 5 to 40 p is 2 to 15 and x is 0 to 30. In one embodiment,
the binder is Al.sub.13 O.sub.4 (OH).sub.24 Cl.sub.7.12(H.sub.2
O) as is described in G. M. Wolterman, et al., Stud. Surf. Sci.
and Catal., 76 pages 105-144 (1993), which is herein incorporated
by reference. In another embodiment, one or more binders are combined
with one or more other non-limiting examples of alumina materials
such as aluminum oxyhydroxide, .gamma.-alumina, boehmite, diaspore,
and transitional aluminas such as .alpha.-alumina, .beta.-alumina,
.gamma.-alumina, .delta.-alumina, .epsilon.-alumina, .kappa.-alumina,
and .rho.-alumina, aluminum trihydroxide, such as gibbsite, bayerite,
nordstrandite, doyelite, and mixtures thereof.
In another embodiment, the binders are alumina sols, predominantly
comprising aluminum oxide, optionally including some silicon. In
yet another embodiment, the binders are peptized alumina made by
treating alumina hydrates such as pseudobohemite, with an acid,
preferably an acid that does not contain a halogen, to prepare sols
or aluminum ion solutions. Non-limiting examples of commercially
available colloidal alumina sols include Nalco 8676 available from
Nalco Chemical Co., Naperville, Ill., and Nyacol AL20DW, available
from Nyacol Nano Technologies, Inc., Ashland, Mass.
The synthesized molecular sieves described above, in a preferred
embodiment, is combined with a binder and one or more matrix material(s).
Matrix materials are typically effective in reducing overall catalyst
cost, act as thermal sinks assisting in shielding heat from the
catalyst composition for example during regeneration, densifying
the catalyst composition, increasing catalyst strength such as crush
strength and attrition resistance, and to control the rate of conversion
in a particular process.
Non-limiting examples of matrix materials include one or more of:
rare earth metals, non-active, metal oxides including titania, zirconia,
magnesia, thoria, beryllia, quartz, silica or sols, and mixtures
thereof, for example silica-magnesia, silica-zirconia, silica-titania,
silica-alumina and silica-alumina-thoria. In an embodiment, matrix
materials are natural clays such as those from the families of montmorillonite
and kaolin. These natural clays include sabbentonites and those
kaolins known as, for example, Dixie, McNamee, Georgia and Florida
clays. Non-limiting examples of other matrix materials include:
haloysite, kaolinite, dickite, nacrite, or anauxite. In one embodiment,
the matrix material, preferably any of the clays, are subjected
to well known modification processes such as calcination and/or
acid treatment and/or chemical treatment.
In one preferred embodiment, the matrix material is a clay or a
clay-type composition, preferably the clay or clay-type composition
having a low iron or titania content, and most preferably the matrix
material is kaolin. Kaolin has been found to form a pumpable, high
solid content slurry, it has a low fresh surface area, and it packs
together easily due to its platelet structure. A preferred average
particle size of the matrix material, most preferably kaolin, is
from about 0.1 .mu.m to about 0.6 .mu.m with a d.sub.90 particle
size distribution of less than about 1 .mu.m.
In one embodiment, the binder, the synthesized molecular sieve
and the matrix material are combined in the presence of a liquid
such as water to form a molecular sieve catalyst composition, where
the amount of binder is from about 2% by weight to about 30% by
weight, preferably from about 5% by weight to about 20% by weight,
and more preferably from about 7% by weight to about 15% by weight,
based on the total weight of the binder, the molecular sieve and
matrix material, excluding the liquid.
Upon combining the synthesized molecular sieve and the matrix material,
optionally with a binder, in a liquid to form a slurry, mixing,
preferably rigorous mixing is needed to produce a substantially
homogeneous mixture containing the synthesized molecular sieve.
Non-limiting examples of suitable liquids include one or a combination
of water, alcohol, ketones, aldehydes, and/or esters. The most preferred
liquid is water. In one embodiment, the slurry is colloid-milled
for a period of time sufficient to produce the desired slurry texture,
sub-particle size, and/or sub-particle size distribution.
The liquid containing synthesized molecular sieve and matrix material,
and the optional binder, are in the same or different liquid, and
are combined in any order, together, simultaneously, sequentially,
or a combination thereof. In the preferred embodiment, the same
liquid, preferably water is used.
The molecular sieve catalyst composition in a preferred embodiment
is made by preparing a slurry containing a molecular sieve, a binder,
and, optionally while preferably, a matrix material. The solids
content of the preferred slurry includes about 20% to about 50%
by weight of the molecular sieve, preferably from about 30% to about
48% by weight of the molecular sieve, more preferably from about
40% to about 48% by weight molecular sieve, about 5% to about 20%,
preferably from about 8% to about 15%, by weight of the binder,
and about 30% to about 80%, preferably about 40% to about 60%, by
weight of the matrix material.
In another most preferred embodiment, the solids content in a slurry
comprising a molecular sieve, a binder, and optionally a matrix
material, and a liquid medium is in the range of from about 20 weight
percent to about 80 weight percent, more preferably in the range
of from 30 weight percent to about 70 weight percent, even more
preferably in the range of from 35 weight percent to 60 weight percent,
still even more preferably from about 36 weight percent to about
50 weight percent, yet even more preferably in the range of from
37 weight percent to about 45 weight percent, and most preferably
in the range of from 38 weight percent to about 45 weight percent.
As the slurry is mixed, the solids in the slurry aggregate preferably
to a point where the slurry contains solid molecular sieve catalyst
composition particles. It is preferable that these particles are
small and have a uniform size distribution such that the d.sub.90
diameter of these particles is less than 20 .mu.m, preferably less
than 15 .mu.m, more preferably less than 10 .mu.m, and most preferably
about 5 .mu.m. The d.sub.90 for purposes of this patent application
and appended claims means that 90 percent by volume of the particles
in the slurry have a particle diameter lower than the d.sub.90 value.
For the purposes of this definition, the particle size distribution
used to define the d.sub.90 is measured using well known laser scattering
techniques using a Honeywell (Microtrac Model 3000 particle size
analyzer from Microtrac, Inc., Clearwater, Fla.). In one embodiment,
the slurry of the invention contains at least 90 percent by volume
of the molecular sieve catalyst composition particles comprising
the molecular sieve, binder, and optional matrix material, have
a diameter of less than 20 .mu.m, preferably less than 15 .mu.m,
more preferably less than 10 .mu.m, and most preferably less than
about 5 .mu.m.
In one preferred embodiment the slurry comprising a liquid portion
and solid portion, wherein the solid portion comprises solid particles,
the solid particles comprising a molecular sieve, a binder and/or
a matrix material; wherein the slurry contains in the range of from
about 30 weight percent to about 50 weight percent solid particles,
preferably from about 35 weight percent to 45 weight percent, and
at least 90 percent of the solid particles having a diameter less
than 20 .mu.m, preferably less than 10 .mu.m.
The molecular sieve catalyst composition particles contains some
water, templating agent or other liquid components, therefore, the
weight percents that describe the solid content in the slurry are
preferably measured, preferably exclusive of the amount of water,
templating agent and/or other liquid contained within the particle.
In the most preferred condition for measuring solids content is
on a calcined basis. Thus, the weight of the solid content in the
slurry is equal to or very similar to the weight of the calcined
molecular sieve catalyst composition. On a calcined basis, the solid
content in the slurry, more specifically, the molecular sieve catalyst
composition particles in the slurry, are from about 20 percent by
weight to 45 percent by weight molecular sieve, 5 percent by weight
to 20 percent by weight binder, and from about 30 percent by weight
to 80 percent by weight matrix material.
In one embodiment, the slurry of the synthesized molecular sieve,
binder and matrix material is mixed or milled to achieve a sufficiently
uniform slurry of sub-particles of the molecular sieve catalyst
composition to form a formulation composition that is then fed to
a forming unit that produces the molecular sieve catalyst composition
or formulated molecular sieve catalyst composition. In a preferred
embodiment, the forming unit is spray dryer. Typically, the forming
unit is maintained at a temperature sufficient to remove most of
the liquid from the slurry, and from the resulting molecular sieve
catalyst composition. The resulting catalyst composition when formed
in this way takes the form of microspheres.
When a spray drier is used as the forming unit, typically, any
one or a combination of the slurries described above, more particularly
a slurry of the synthesized molecular sieve, matrix material, and
binder, is co-fed to the spray dryer with a drying gas with an average
inlet temperature ranging from 200.degree. C. to 550.degree. C.,
and a combined outlet temperature ranging from 100.degree. C. to
about 225.degree. C. In an embodiment, the average diameter of the
spray dried formed catalyst composition is from about 40 .mu.m to
about 300 .mu.m, preferably from about 50 .mu.m to about 250 .mu.m,
more preferably from about 50 .mu.m to about 200 .mu.m, and most
preferably from about 65 .mu.m to about 90 .mu.m.
During spray drying, the slurry is passed through a nozzle distributing
the slurry into small droplets, resembling an aerosol spray into
a drying chamber. Atomization is achieved by forcing the slurry
through a single nozzle or multiple nozzles with a pressure drop
in the range of from 100 psia to 11000 psia (690 kPaa to 6895 kPaa).
In another embodiment, the slurry is co-fed through a single nozzle
or multiple nozzles along with an atomization fluid such as air,
steam, flue gas, or any other suitable gas.
In yet another embodiment, the slurry described above is directed
to the perimeter of a spinning wheel that distributes the slurry
into small droplets, the size of which is controlled by many factors
including slurry viscosity, surface tension, flow rate, pressure,
and temperature of the slurry, the shape and dimension of the nozzle(s),
or the spinning rate of the wheel. These droplets are then dried
in a co-current or counter-current flow of air passing through a
spray drier to form a substantially dried or dried molecular sieve
catalyst composition, more specifically a molecular sieve composition
in a powder or a microsphere form.
Generally, the size of the microspheres is controlled to some extent
by the solids content of the slurry. However, control of the size
of the catalyst composition and its spherical characteristics are
controllable by varying the slurry feed properties and conditions
of atomization.
Other methods for forming a molecular sieve catalyst composition
is described in U.S. patent application Ser. No. 09/617714 filed
Jul. 17 2000 (spray drying using a recycled molecular sieve catalyst
composition), which is herein incorporated by reference.
In another embodiment, the formulated molecular sieve catalyst
composition contains from about 1% to about 99%, preferably from
about 10% to about 90%, more preferably from about 10% to about
80%, even more preferably from about 20% to about 70%, and most
preferably from about 25% to about 60% by weight of the molecular
sieve based on the total weight of the molecular sieve catalyst
composition.
Once the molecular sieve catalyst composition is formed in a substantially
dry or dried state, to further harden and/or activate the formed
catalyst composition, a heat treatment such as calcination, at an
elevated temperature is preferably performed. A conventional calcination
environment is air that typically includes a small amount of water
vapor. Typical calcination temperatures are in the range from about
400.degree. C. to about 1000.degree. C., preferably from about
500.degree. C. to about 800.degree. C., and most preferably from
about 550.degree. C. to about 700.degree. C., preferably in a calcination
environment such as air, nitrogen, helium, flue gas (combustion
product lean in oxygen), or any combination thereof. In one embodiment,
calcination of the formulated molecular sieve catalyst composition
is carried out in any number of well known devices including rotary
calciners, fluid bed calciners, batch ovens, and the like. Calcination
time is typically dependent on the degree of hardening of the molecular
sieve catalyst composition and the temperature ranges from about
15 minutes to about 20 hours. In a preferred embodiment, the molecular
sieve catalyst composition is heated in nitrogen at a temperature
of from about 600.degree. C. to about 700.degree. C. Heating is
carried out for a period of time typically from 15 minutes to 15
hours, preferably from 30 minutes to about 10 hours, more preferably
from about 30 minutes to about 5 hours
In one embodiment, the attrition resistance of a molecular sieve
catalyst composition is measured using an Attrition Rate Index (ARI),
measured in weight percent catalyst composition attrited per hour.
ARI is measured by adding 6.0 g of catalyst composition having a
particles size ranging from 53 microns to 125 microns to a hardened
steel attrition cup. Approximately 23700 cc/min of nitrogen gas
is bubbled through a water-containing bubbler to humidify the nitrogen.
The wet nitrogen passes through the attrition cup, and exits the
attrition apparatus through a porous fiber thimble. The flowing
nitrogen removes the finer particles, with the larger particles
being retained in the cup. The porous fiber thimble separates the
fine catalyst particles from the nitrogen that exits through the
thimble. The fine particles remaining in the thimble represent the
catalyst composition that has broken apart through attrition. The
nitrogen flow passing through the attrition cup is maintained for
1 hour. The fines collected in the thimble are removed from the
unit. A new thimble is then installed. The catalyst left in the
attrition unit is attrited for an additional 3 hours, under the
same gas flow and moisture levels. The fines collected in the thimble
are recovered. The collection of fine catalyst particles separated
by the thimble after the first hour are weighed. The amount in grams
of fine particles divided by the original amount of catalyst charged
to the attrition cup expressed on per hour basis is the ARI, in
weight percent per hour (wt. %/hr). ARI is represented by the formula:
ARI=C/(B+C)/D multiplied by 100%, wherein B is weight of catalyst
composition left in the cup after the attrition test, C is the weight
of collected fine catalyst particles after the first hour of attrition
treatment, and D is the duration of treatment in hours after the
first hour attrition treatment.
In one embodiment, the molecular sieve catalyst composition or
formulated molecular sieve catalyst composition has an ARI less
than 15 weight percent per hour, preferably less than 10 weight
percent per hour, more preferably less than 5 weight percent per
hour, and even more preferably less than 2 weight percent per hour,
and most preferably less than 1 weight percent per hour. In one
embodiment, the molecular sieve catalyst composition or formulated
molecular sieve catalyst composition has an ARI in the range of
from 0 weight percent per hour to less than 5 weight percent per
hour, more preferably from about 0.05 weight percent per hour to
less than 3 weight percent per hour, and most preferably from about
0.01 weight percent per hour to less than 2 weight percent per hour.
In one preferred embodiment of the invention, the molecular sieve
catalyst composition or formulated molecular sieve catalyst composition
comprises a synthesized molecular sieve in an amount of from 20
weight percent to 60 weight percent, a binder in an amount of from
5 to 50 weight percent, and a matrix material in an amount of from
0 to 78 weight percent based on the total weight of the catalyst
composition, upon calcination, and the catalyst composition having
weight ratio of binder to sieve of from 0.1 to less than 0.5. In
addition, the catalyst composition of this embodiment has an MSA
on a contained sieve basis of the molecular sieve by itself from
450 m.sup.2 /g-molecular sieve to 550 m.sup.2 /g-molecular sieve,
and/or an ARI less than 2 weight percent per hour.
Process for Using the Molecular Sieve Catalyst Compositions
The molecular sieve catalyst compositions or formulated molecular
sieve catalyst compositions described above are useful in a variety
of processes including: cracking, of for example a naphtha feed
to light olefin(s) (U.S. Pat. No. 6300537) or higher molecular
weight (MW) hydrocarbons to lower MW hydrocarbons; hydrocracking,
of for example heavy petroleum and/or cyclic feedstock; isomerization,
of for example aromatics such as xylene, polymerization, of for
example one or more olefin(s) to produce a polymer product; reforming;
hydrogenation; dehydrogenation; dewaxing, of for example hydrocarbons
to remove straight chain paraffins; absorption, of for example alkyl
aromatic compounds for separating out isomers thereof, alkylation,
of for example aromatic hydrocarbons such as benzene and alkyl benzene,
optionally with propylene to produce cumeme or with long chain olefins;
transalkylation, of for example a combination of aromatic and polyalkylaromatic
hydrocarbons; dealkylation; hydrodecylization; disproportionation,
of for example toluene to make benzene and paraxylene; oligomerization,
of for example straight and branched chain olefin(s); and dehydrocyclization.
Preferred processes are conversion processes including: naphtha
to highly aromatic mixtures; light olefin(s) to gasoline, distillates
and lubricants; oxygenates to olefin(s); light paraffins to olefins
and/or aromatics; and unsaturated hydrocarbons (ethylene and/or
acetylene) to aldehydes for conversion into alcohols, acids and
esters. The most preferred process of the invention is a process
directed to the conversion of a feedstock comprising one or more
oxygenates to one or more olefin(s).
The molecular sieve catalyst compositions described above are particularly
useful in conversion processes of different feedstock. Typically,
the feedstock contains one or more aliphatic-containing compounds
that include alcohols, amines, carbonyl compounds for example aldehydes,
ketones and carboxylic acids, ethers, halides, mercaptans, sulfides,
and the like, and mixtures thereof. The aliphatic moiety of the
aliphatic-containing compounds typically contains from 1 to about
50 carbon atoms, preferably from 1 to 20 carbon atoms, more preferably
from 1 to 10 carbon atoms, and most preferably from 1 to 4 carbon
atoms.
Non-limiting examples of aliphatic-containing compounds include:
alcohols such as methanol and ethanol, alkyl-mercaptans such as
methyl mercaptan and ethyl mercaptan, alkyl-sulfides such as methyl
sulfide, alkyl-amines such as methyl amine, alkyl-ethers such as
dimethyl ether, diethyl ether and methylethyl ether, alkyl-halides
such as methyl chloride and ethyl chloride, alkyl ketones such as
dimethyl ketone, formaldehydes, and various acids such as acetic
acid.
In a preferred embodiment of the process of the invention, the
feedstock contains one or more oxygenates, more specifically, one
or more organic compound(s) containing at least one oxygen atom.
In the most preferred embodiment of the process of invention, the
oxygenate in the feedstock is one or more alcohol(s), preferably
aliphatic alcohol(s) where the aliphatic moiety of the alcohol(s)
has from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms,
and most preferably from 1 to 4 carbon atoms. The alcohols useful
as feedstock in the process of the invention include lower straight
and branched chain aliphatic alcohols and their unsaturated counterparts.
Non-limiting examples of oxygenates include methanol, ethanol,
n-propanol, isopropanol, methyl ethyl ether, dimethyl ether, diethyl
ether, di-isopropyl ether, formaldehyde, dimethyl carbonate, dimethyl
ketone, acetic acid, and mixtures thereof. In the most preferred
embodiment, the feedstock is selected from one or more of methanol,
ethanol, dimethyl ether, diethyl ether or a combination thereof,
more preferably methanol and dimethyl ether, and most preferably
methanol.
The various feedstocks discussed above, particularly a feedstock
containing an oxygenate, more particularly a feedstock containing
an alcohol, is converted primarily into one or more olefin(s). The
olefin(s) or olefin monomer(s) produced from the feedstock typically
have from 2 to 30 carbon atoms, preferably 2 to 8 carbon atoms,
more preferably 2 to 6 carbon atoms, still more preferably 2 to
4 carbons atoms, and most preferably ethylene an/or propylene. Non-limiting
examples of olefin monomer(s) include ethylene, propylene, butene-1
pentene-14-methyl-pentene-1 hexene-1 octene-1 and decene-1 preferably
ethylene, propylene, butene-1 pentene-14-methyl-pentene-1 hexene-1
octene-1 and isomers thereof. Other olefin monomer(s) include unsaturated
monomers, diolefins having 4 to 18 carbon atoms, conjugated or nonconjugated
dienes, polyenes, vinyl monomers and cyclic olefins.
In the most preferred embodiment, the feedstock, preferably of
one or more oxygenates, is converted in the presence of a molecular
sieve catalyst composition of the invention into olefin(s) having
2 to 6 carbons atoms, preferably 2 to 4 carbon atoms. Most preferably,
the olefin(s), alone or combination, are converted from a feedstock
containing an oxygenate, preferably an alcohol, most preferably
methanol, to the preferred olefin(s) ethylene and/or propylene.
The are many processes used to convert feedstock into olefin(s)
including various cracking processes such as steam cracking, thermal
regenerative cracking, fluidized bed cracking, fluid catalytic cracking,
deep catalytic cracking, and visbreaking. The most preferred process
is generally referred to as gas-to-olefins (GTO) or alternatively,
methanol-to-olefins (MTO). In a GTO process, typically natural gas
is converted into a synthesis gas that is converted into an oxygenated
feedstock, preferably containing methanol, where the oxygenated
feedstock is converted in the presence of a molecular sieve catalyst
composition into one or more olefin(s), preferably ethylene and/or
propylene. In a MTO process, typically an oxygenated feedstock,
most preferably a methanol containing feedstock, is converted in
the presence of a molecular sieve catalyst composition thereof into
one or more olefin(s), preferably and predominantly, ethylene and/or
propylene, often referred to as light olefin(s).
In one embodiment of the process for conversion of a feedstock,
preferably a feedstock containing one or more oxygenates, the amount
of olefin(s) produced based on the total weight of hydrocarbon produced
is greater than 50 weight percent, preferably greater than 60 weight
percent, more preferably greater than 70 weight percent, and most
preferably greater than 75 weight percent. In another embodiment
of the process for conversion of one or more oxygenates to one or
more olefin(s), the amount of ethylene and/or propylene produced
based on the total weight of hydrocarbon product produced is greater
than 65 weight percent, preferably greater than 70 weight percent,
more preferably greater than 75 weight percent, and most preferably
greater than 78 weight percent.
In another embodiment of the process for conversion of one or more
oxygenates to one or more olefin(s), the amount ethylene produced
in weight percent based on the total weight of hydrocarbon product
produced, is greater than 30 weight percent, more preferably greater
than 35 weight percent, and most preferably greater than 40 weight
percent. In yet another embodiment of the process for conversion
of one or more oxygenates to one or more olefin(s), the amount of
propylene produced in weight percent based on the total weight of
hydrocarbon product produced is greater than 20 weight percent,
preferably greater than 25 weight percent, more preferably greater
than 30 weight percent, and most preferably greater than 35 weight
percent.
The feedstock, in one embodiment, contains one or more diluent(s),
typically used to reduce the concentration of the feedstock, and
are generally non-reactive to the feedstock or molecular sieve catalyst
composition. Non-limiting examples of diluents include helium, argon,
nitrogen, carbon monoxide, carbon dioxide, water, essentially non-reactive
paraffins (especially alkanes such as methane, ethane, and propane),
essentially non-reactive aromatic compounds, and mixtures thereof.
The most preferred diluents are water and nitrogen, with water being
particularly preferred.
The diluent, water, is used either in a liquid or a vapor form,
or a combination thereof. The diluent is either added directly to
a feedstock entering into a reactor or added directly into a reactor,
or added with a molecular sieve catalyst composition. In one embodiment,
the amount of diluent in the feedstock is in the range of from about
1 to about 99 mole percent based on the total number of moles of
the feedstock and diluent, preferably from about 1 to 80 mole percent,
more preferably from about 5 to about 50 and most preferably from
about 5 to about 25.
In one embodiment, other hydrocarbons are added to a feedstock
either directly or indirectly, and include olefin(s), paraffin(s),
aromatic(s) (see for example U.S. Pat. No. 4677242 addition of
aromatics) or mixtures thereof, preferably propylene, butylene,
pentylene, and other hydrocarbons having 4 or more carbon atoms,
or mixtures thereof.
The process for converting a feedstock, especially a feedstock
containing one or more oxygenates, in the presence of a molecular
sieve catalyst composition of the invention, is carried out in a
reaction process in a reactor, where the process is a fixed bed
process, a fluidized bed process (includes a turbulent bed process),
preferably a continuous fluidized bed process, and most preferably
a continuous high velocity fluidized bed process.
The reaction processes can take place in a variety of catalytic
reactors such as hybrid reactors that have a dense bed or fixed
bed reaction zones and/or fast fluidized bed reaction zones coupled
together, circulating fluidized bed reactors, riser reactors, and
the like. Suitable conventional reactor types are described in for
example U.S. Pat. No. 4076796 U.S. Pat. No. 6287522 (dual riser),
and Fluidization Engineering, D. Kunii and O. Levenspiel, Robert
E. Krieger Publishing Company, New York, N.Y. 1977 which are all
herein fully incorporated by reference. The preferred reactor type
are riser reactors generally described in Riser Reactor, Fluidization
and Fluid-Particle Systems, pages 48 to 59 F. A. Zenz and D. F.
Othmo, Reinhold Publishing Corporation, New York, 1960 and U.S.
Pat. No. 6166282 (fast-fluidized bed reactor), and U.S. patent
application Ser. No. 09/564613 filed May 4 2000 (multiple riser
reactor), which are all herein fully incorporated by reference.
In the preferred embodiment, a fluidized bed process or high velocity
fluidized bed process includes a reactor system, a regeneration
system and a recovery system.
The reactor system preferably is a fluid bed reactor system having
a first reaction zone within one or more riser reactor(s) and a
second reaction zone within at least one disengaging vessel, preferably
comprising one or more cyclones. In one embodiment, the one or more
riser reactor(s) and disengaging vessel is contained within a single
reactor vessel. Fresh feedstock, preferably containing one or more
oxygenates, optionally with one or more diluent(s), is fed to the
one or more riser reactor(s) in which a molecular sieve catalyst
composition or coked version thereof is introduced. In one embodiment,
the molecular sieve catalyst composition or coked version thereof
is contacted with a liquid or gas, or combination thereof, prior
to being introduced to the riser reactor(s), preferably the liquid
is water or methanol, and the gas is an inert gas such as nitrogen.
In an embodiment, the amount of fresh feedstock fed separately
or jointly with a vapor feedstock, to a reactor system is in the
range of from 0.1 weight percent to about 85 weight percent, preferably
from about 1 weight percent to about 75 weight percent, more preferably
from about 5 weight percent to about 65 weight percent based on
the total weight of the feedstock including any diluent contained
therein. The liquid and vapor feedstocks are preferably of similar
or the same composition, or contain varying proportions of the same
or different feedstock with the same or different diluent.
The feedstock entering the reactor system is preferably converted,
partially or fully, in the first reactor zone into a gaseous effluent
that enters the disengaging vessel along with a coked molecular
sieve catalyst composition. In the preferred embodiment, cyclone(s)
within the disengaging vessel are designed to separate the molecular
sieve catalyst composition, preferably a coked molecular sieve catalyst
composition, from the gaseous effluent containing one or more olefin(s)
within the disengaging zone. Cyclones are preferred, however, gravity
effects within the disengaging vessel will also separate the catalyst
compositions from the gaseous effluent. Other methods for separating
the catalyst compositions from the gaseous effluent include the
use of plates, caps, elbows, and the like.
In one embodiment of the disengaging system, the disengaging system
includes a disengaging vessel, typically a lower portion of the
disengaging vessel is a stripping zone. In the stripping zone the
coked molecular sieve catalyst composition is contacted with a gas,
preferably one or a combination of steam, methane, carbon dioxide,
carbon monoxide, hydrogen, or an inert gas such as argon, preferably
steam, to recover adsorbed hydrocarbons from the coked molecular
sieve catalyst composition that is then introduced to the regeneration
system. In another embodiment, the stripping zone is in a separate
vessel from the disengaging vessel and the gas is passed at a gas
hourly superficial velocity (GHSV) of from 1 hr.sup.-1 to about
20000 hr.sup.-1 based on the volume of gas to volume of coked molecular
sieve catalyst composition, preferably at an elevated temperature
from 250.degree. C. to about 750.degree. C., preferably from about
350.degree. C. to 650.degree. C., over the coked molecular sieve
catalyst composition.
The conversion temperature employed in the conversion process,
specifically within the reactor system, is in the range of from
about 200.degree. C. to about 1000.degree. C., preferably from about
250.degree. C. to about 800.degree. C., more preferably from about
250.degree. C. to about 750.degree. C., yet more preferably from
about 300.degree. C. to about 650.degree. C., yet even more preferably
from about 350.degree. C. to about 600.degree. C. most preferably
from about 350.degree. C. to about 550.degree. C.
The conversion pressure employed in the conversion process, specifically
within the reactor system, varies over a wide range including autogenous
pressure. The conversion pressure is based on the partial pressure
of the feedstock exclusive of any diluent therein. Typically the
conversion pressure employed in the process is in the range of from
about 0.1 kPaa to about 5 MPaa, preferably from about 5 kPaa to
about 1 MPaa, and most preferably from about 20 kPaa to about 500
kPaa.
The weight hourly space velocity (WHSV), particularly in a process
for converting a feedstock containing one or more oxygenates in
the presence of a molecular sieve catalyst composition within a
reaction zone, is defined as the total weight of the feedstock excluding
any diluents to the reaction zone per hour per weight of molecular
sieve in the molecular sieve catalyst composition in the reaction
zone. The WHSV is maintained at a level sufficient to keep the catalyst
composition in a fluidized state within a reactor.
Typically, the WHSV ranges from about 1 hr.sup.-1 to about 5000
hr.sup.-1 preferably from about 2 hr.sup.-1 to about 3000 hr.sup.-1
more preferably from about 5 hr.sup.-1 to about 1500 hr.sup.-1
and most preferably from about 10 hr.sup.-1 to about 1000 hr.sup.-1.
In one preferred embodiment, the WHSV is greater than 20 hr.sup.-1
preferably the WHSV for conversion of a feedstock containing methanol
and dimethyl ether is in the range of from about 20 hr.sup.-1 to
about 300 hr.sup.-1.
The superficial gas velocity (SGV) of the feedstock including diluent
and reaction products within the reactor system is preferably sufficient
to fluidize the molecular sieve catalyst composition within a reaction
zone in the reactor. The SGV in the process, particularly within
the reactor system, more particularly within the riser reactor(s),
is at least 0.1 meter per second (m/sec), preferably greater than
0.5 m/sec, more preferably greater than 1 m/sec, even more preferably
greater than 2 m/sec, yet even more preferably greater than 3 m/sec,
and most preferably greater than 4 m/sec. See for example U.S. patent
application Ser. No. 09/708753 filed Nov. 8 2000 which is herein
incorporated by reference.
In one preferred embodiment of the process for converting an oxygenate
to olefin(s) using a silicoaluminophosphate molecular sieve catalyst
composition, the process is operated at a WHSV of at least 20 hr.sup.-1
and a Temperature Corrected Normalized Methane Selectivity (TCNMS)
of less than 0.016 preferably less than or equal to 0.01. See for
example U.S. Pat. No. 5952538 which is herein fully incorporated
by reference. In another embodiment of the processes for converting
an oxygenate such as methanol to one or more olefin(s) using a molecular
sieve catalyst composition, the WHSV is from 0.01 hr.sup.-1 to about
100 hr.sup.-1 at a temperature of from about 350.degree. C. to
550.degree. C., and silica to Me.sub.2 O.sub.3 (Me is a Group IIIA
or VIII element from the Periodic Table of Elements) molar ratio
of from 300 to 2500. See for example EP-0 642 485 B1 which is herein
fully incorporated by reference. Other processes for converting
an oxygenate such as methanol to one or more olefin(s) using a molecular
sieve catalyst composition are described in PCT WO 01/23500 published
Apr. 5 2001 (propane reduction at an average catalyst feedstock
exposure of at least 1.0), which is herein incorporated by reference.
The coked molecular sieve catalyst composition is withdrawn from
the disengaging vessel, preferably by one or more cyclones(s), and
introduced to the regeneration system. The regeneration system comprises
a regenerator where the coked catalyst composition is contacted
with a regeneration medium, preferably a gas containing oxygen,
under general regeneration conditions of temperature, pressure and
residence time. Non-limiting examples of the regeneration medium
include one or more of oxygen, O.sub.3 SO.sub.3 N.sub.2 O, NO,
NO.sub.2 N.sub.2 O.sub.5 air, air diluted with nitrogen or carbon
dioxide, oxygen and water (U.S. Pat. No. 6245703), carbon monoxide
and/or hydrogen. The regeneration conditions are those capable of
burning coke from the coked catalyst composition, preferably to
a level less than 0.5 weight percent based on the total weight of
the coked molecular sieve catalyst composition entering the regeneration
system. The coked molecular sieve catalyst composition withdrawn
from the regenerator forms a regenerated molecular sieve catalyst
composition.
The regeneration temperature is in the range of from about 200.degree.
C. to about 1500.degree. C., preferably from about 300.degree. C.
to about 1000.degree. C., more preferably from about 450.degree.
C. to about 750.degree. C., and most preferably from about 550.degree.
C. to 700.degree. C. The regeneration pressure is in the range of
from about 15 psia (103 kPaa) to about 500 psia (3448 kPaa), preferably
from about 20 psia (138 kPaa) to about 250 psia (1724 kPaa), more
preferably from about 25 psia (172 kPaa) to about 150 psia (1034
kPaa), and most preferably from about 30 psia (207 kPaa) to about
60 psia (414 kPaa). The preferred residence time of the molecular
sieve catalyst composition in the regenerator is in the range of
from about one minute to several hours, most preferably about one
minute to 100 minutes, and the preferred volume of oxygen in the
gas is in the range of from about 0.01 mole percent to about 5 mole
percent based on the total volume of the gas.
In one embodiment, regeneration promoters, typically metal containing
compounds such as platinum, palladium and the like, are added to
the regenerator directly, or indirectly, for example with the coked
catalyst composition. Also, in another embodiment, a fresh molecular
sieve catalyst composition is added to the regenerator containing
a regeneration medium of oxygen and water as described in U.S. Pat.
No. 6245703 which is herein fully incorporated by reference.
In yet another embodiment, a portion of the coked molecular sieve
catalyst composition from the regenerator is returned directly to
the one or more riser reactor(s), or indirectly, by pre-contacting
with the feedstock, or contacting with fresh molecular sieve catalyst
composition, or contacting with a regenerated molecular sieve catalyst
composition or a cooled regenerated molecular sieve catalyst composition
described below.
The burning of coke is an exothermic reaction, and in an embodiment,
the temperature within the regeneration system is controlled by
various techniques in the art including feeding a cooled gas to
the regenerator vessel, operated either in a batch, continuous,
or semi-continuous mode, or a combination thereof. A preferred technique
involves withdrawing the regenerated molecular sieve catalyst composition
from the regeneration system and passing the regenerated molecular
sieve catalyst composition through a catalyst cooler that forms
a cooled regenerated molecular sieve catalyst composition. The catalyst
cooler, in an embodiment, is a heat exchanger that is located either
internal or external to the regeneration system. In one embodiment,
the cooler regenerated molecular sieve catalyst composition is returned
to the regenerator in a continuous cycle, alternatively, (see U.S.
patent application Ser. No. 09/587766 filed Jun. 6 2000) a portion
of the cooled regenerated molecular sieve catalyst composition is
returned to the regenerator vessel in a continuous cycle, and another
portion of the cooled molecular sieve regenerated molecular sieve
catalyst composition is returned to the riser reactor(s), directly
or indirectly, or a portion of the regenerated molecular sieve catalyst
composition or cooled regenerated molecular sieve catalyst composition
is contacted with by-products within the gaseous effluent (PCT WO
00/49106 published Aug. 24 2000), which are all herein fully incorporated
by reference. In another embodiment, a regenerated molecular sieve
catalyst composition contacted with an alcohol, preferably ethanol,
1-propnaol, 1-butanol or mixture thereof, is introduced to the reactor
system, as described in U.S. patent application Ser. No. 09/785122
filed Feb. 16 2001 which is herein fully incorporated by reference.
Other methods for operating a regeneration system are in disclosed
U.S. Pat. No. 6290916 (controlling moisture), which is herein
fully incorporated by reference.
The regenerated molecular sieve catalyst composition withdrawn
from the regeneration system, preferably from the catalyst cooler,
is combined with a fresh molecular sieve catalyst composition and/or
re-circulated molecular sieve catalyst composition and/or feedstock
and/or fresh gas or liquids, and returned to the riser reactor(s).
In another embodiment, the regenerated molecular sieve catalyst
composition withdrawn from the regeneration system is returned to
the riser reactor(s) directly, optionally after passing through
a catalyst cooler. In one embodiment, a carrier, such as an inert
gas, feedstock vapor, steam or the like, semi-continuously or continuously,
facilitates the introduction of the regenerated molecular sieve
catalyst composition to the reactor system, preferably to the one
or more riser reactor(s).
In one embodiment, the optimum level of coke on the molecular sieve
catalyst composition in the reaction zone is maintained by controlling
the flow of the regenerated molecular sieve catalyst composition
or cooled regenerated molecular sieve catalyst composition from
the regeneration system to the reactor system, a complete regeneration.
There are many techniques for controlling the flow of a molecular
sieve catalyst composition described in Michael Louge, Experimental
Techniques, Circulating Fluidized Beds, Grace, Avidan and Knowlton,
eds., Blackie, 1997 (336-337), which is herein incorporated by reference.
In another embodiment, the optimum level of coke on the molecular
sieve catalyst composition in the reaction zone is maintained by
controlling the flow rate of oxygen containing gas flowing to the
regenerator, a partial regeneration. Coke levels on the molecular
sieve catalyst composition is measured by withdrawing from the conversion
process the molecular sieve catalyst composition at a point in the
process and determining its carbon content. Typical levels of coke
on the molecular sieve catalyst composition, after regeneration
is in the range of from 0.01 weight percent to about 15 weight percent,
preferably from about 0.1 weight percent to about 10 weight percent,
more preferably from about 0.2 weight percent to about 5 weight
percent, and most preferably from about 0.3 weight percent to about
2 weight percent based on the total weight of the molecular sieve
and not the total weight of the molecular sieve catalyst composition.
In one preferred embodiment, the mixture of fresh molecular sieve
catalyst composition and/or regenerated molecular sieve catalyst
composition and/or cooled regenerated molecular sieve catalyst composition
in the reaction zone contains in the range of from about 1 to 50
weight percent, preferably from about 2 to 30 weight percent, more
preferably from about 2 to about 20 weight percent, and most preferably
from about 2 to about 10 coke or carbonaceous deposit based on the
total weight of the mixture of molecular sieve catalyst compositions.
See for example U.S. Pat. No. 6023005 which is herein fully incorporated
by reference. It is recognized that the molecular sieve catalyst
composition in the reaction zone is made up of a mixture of regenerated
and fresh molecular sieve catalyst composition that have varying
levels of carbon and carbon-like deposits, coke. The measured level
of these deposits, specifically coke, represents an average of the
levels on individual molecular sieve catalyst composition particles.
The gaseous effluent is withdrawn from the disengaging system and
is passed through a recovery system. There are many well known recovery
systems, techniques and sequences that are useful in separating
olefin(s) and purifying olefin(s) from the gaseous effluent. Recovery
systems generally comprise one or more or a combination of a various
separation, fractionation and/or distillation towers, columns, splitters,
or trains, reaction systems such as ethylbenzene manufacture (U.S.
Pat. No. 5476978) and other derivative processes such as aldehydes,
ketones and ester manufacture (U.S. Pat. No. 5675041), and other
associated equipment for example various condensers, heat exchangers,
refrigeration systems or chill trains, compressors, knock-out drums
or pots, pumps, and the like. Non-limiting examples of these towers,
columns, splitters or trains used alone or in combination include
one or more of a demethanizer, preferably a high temperature demethanizer,
a dethanizer, a depropanizer, preferably a wet depropanizer, a wash
tower often referred to as a caustic wash tower and/or quench tower,
absorbers, adsorbers, membranes, ethylene (C2) splitter, propylene
(C3) splitter, butene (C4) splitter, and the like.
Various recovery systems useful for recovering predominately olefin(s),
preferably prime or light olefin(s) such as ethylene, propylene
and/or butene are described in U.S. Pat. No. 5960643 (secondary
rich ethylene stream), U.S. Pat. Nos. 5019143 5452581 and 5082481
(membrane separations), U.S. Pat. No. 5672197 (pressure dependent
adsorbents), U.S. Pat. No. 6069288 (hydrogen removal), U.S. Pat.
No. 5904880 (recovered methanol to hydrogen and carbon dioxide
in one step), U.S. Pat. No. 5927063 (recovered methanol to gas
turbine power plant), and U.S. Pat. No. 6121504 (direct product
quench), U.S. Pat. No. 6121503 (high purity olefins without superfractionation),
and U.S. Pat. No. 6293998 (pressure swing adsorption), which are
all herein fully incorporated by reference.
Generally accompanying most recovery systems is the production,
generation or accumulation of additional products, by-products and/or
contaminants along with the preferred prime products. The preferred
prime products, the light olefins, such as ethylene and propylene,
are typically purified for use in derivative manufacturing processes
such as polymerization processes. Therefore, in the most preferred
embodiment of the recovery system, the recovery system also includes
a purification system. For example, the light olefin(s) produced
particularly in a MTO process are passed through a purification
system that removes low levels of by-products or contaminants. Non-limiting
examples of contaminants and by-products include generally polar
compounds such as water, alcohols, carboxylic acids, ethers, carbon
oxides, sulfur compounds such as hydrogen sulfide, carbonyl sulfides
and mercaptans, ammonia and other nitrogen compounds, arsine, phosphine
and chlorides. Other contaminants or by-products include hydrogen
and hydrocarbons such as acetylene, methyl acetylene, propadiene,
butadiene and butyne.
Other recovery systems that include purification systems, for example
for the purification of olefin(s), are described in Kirk-Othmer
Encyclopedia of Chemical Technology, 4th Edition, Volume 9 John
Wiley & Sons, 1996 pages 249-271 and 894-899 which is herein
incorporated by reference. Purification systems are also described
in for example, U.S. Pat. No. 6271428 (purification of a diolefin
hydrocarbon stream), U.S. Pat. No. 6293999 (separating propylene
from propane), and U.S. patent application Ser. No. 09/689363 filed
Oct. 20 2000 (purge stream using hydrating catalyst), which is
herein incorporated by reference.
Typically, in converting one or more oxygenates to olefin(s) having
2 or 3 carbon atoms, an amount of hydrocarbons, particularly olefin(s),
especially olefin(s) having 4 or more carbon atoms, and other by-products
are formed or produced. Included in the recovery systems of the
invention are reaction systems for converting the products contained
within the effluent gas withdrawn from the reactor or converting
those products produced as a result of the recovery system utilized.
In one embodiment, the effluent gas withdrawn fro |