Molecular sieve abstract
The invention relates to a conversion process of a feedstock, preferably
an oxygenated feedstock, into one or more olefin(s), preferably
ethylene and/or propylene, in the presence of a molecular sieve
catalyst composition that includes a molecular sieve and a Group
3 metal oxide and/or an oxide of a Lanthanide or Actinide series
element. The invention is also directed to methods of making and
formulating the molecular sieve catalyst composition useful in a
conversion process of a feedstock into one or more olefin(s).
Molecular sieve claims
We claim:
1. A process for converting a feedstock comprising contracting
one or more oxygenate(s) with one or more olefin(s) in the presence
of a molecular sieve catalyst composition comprising a molecular
sieve, a binder, a matrix material and a Group 3 metal oxide and/or
an oxide of the Lanthanide or Actinide series elements.
2. The process of claim 1 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, and
optionally in the presence of a templating agent.
3. The process of claim 1 wherein the metal of the Group 3 metal
oxide or the oxide of the Lanthanide or Actinide series elements
is selected from one of the group consisting of scandium, yttrium,
lanthanum, cerium, praseodymium and neodymium.
4. The process of claim 1 wherein the metal of Group 3 metal oxide
is yttrium.
5. The process of claim 1 wherein the Group 3 metal oxide or the
oxide of the Lanthanide or Actinide series element is selected from
one of the group consisting of lanthanum oxide, yttrium oxide, scandium
oxide, cerium oxide, praseodymium oxide and neodymium oxide, or
mixtures thereof.
6. The process of claim 1 wherein the molecular sieve catalyst
composition has a Lifetime Enhancement Index (LEI) greater than
1.1.
7. The process of claim 1 wherein the molecular sieve is a silicoaluminophosphate
molecular sieve and/or an aluminophosphate molecular sieve.
8. The process of claim 1 wherein the oxygenate(s) comprises methanol
and/or dimethylether.
9. The process of claim 1 wherein the olefins(s) include ethylene
and propylene, the molecular sieve is a silicoaluminophosphate molecular
sieve, the oxygenate(s) comprises methanol, the Group 3 metal oxide
is yttrium oxide, the binder is an alumina sol, and the matrix material
is a clay.
10. A process for producing one or more olefin(s), the process
comprising the steps of: (a) introducing a feedstock comprising
at least one oxygenate to a reactor system in the presence of a
molecular sieve catalyst composition comprising a molecular sieve,
a binder, a matrix material, and a Group 3 metal oxide and/or an
oxide of the Lanthanide or Actinide series elements; (b) withdrawing
from the reactor system an effluent stream; and (c) passing the
effluent stream through a recovery system; and (d) recovering at
least the one or more olefin(s).
11. The process of claim 10 wherein the binder is an alumina sol.
12. The process of claim 10 wherein the matrix material is a clay.
13. The process of claim 10 wherein the molecular sieve is a silicoaluminophosphate
molecular sieve and/or an aluminophosphate molecular sieve.
14. The process of claim 10 wherein the Group 3 metal oxide is
a lanthanum oxide or a yttrium oxide or a mixture thereof.
15. The process of claim 10 wherein the feedstock comprises methanol
and/or dimethylether.
16. The process of claim 10 wherein the LEI of the molecular sieve
catalyst composition is greater than that for the same molecular
sieve catalyst composition without the Group 3 metal oxide or the
oxide of the Lanthanide or Actinide series elements.
17. The process of claim 10 wherein the Group 3 metal oxide is
yttrium oxide.
18. The process of claim 10 wherein the molecular sieve catalyst
composition has a LEI greater than 1.5.
19. The process of claim 10 wherein the olefin(s) include ethylene
and propylene.
20. A process for converting a feedstock comprising contracting
one or more oxygenate(s) with one or more olefin(s) in the presence
of a molecular sieve catalyst composition prepared by a method for
making the molecular sieve catalyst composition, the method comprising
the steps of: (i) forming an active Group 3 metal oxide or an active
oxide of a Lanthanide or Actinide series element, (ii) synthesizing
a molecular sieve 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, and (iii)
introducing a binder, optionally with a matrix material.
21. A process for converting a feedstock comprising contracting
one or more oxygenate(s) with one or more olefin(s) in the presence
of a molecular sieve composition prepared by a method of making
the molecular sieve composition, the method comprising the steps
of: (i) synthesizing a molecular sieve by the method comprising
the steps of: (a) forming a first reaction mixture of at least one
templating agent and at least two of the group consisting of a silicon
source, a phosphorous source and an aluminum source; and (b) removing
the molecular sieve from the first reaction mixture; (ii) forming
an active metal oxide by the method comprising the steps of: (a)
forming a second reaction mixture comprising a Group 3 or Lanthanide
or Actinide series element metal oxide precursor and a precipitating
agent, (b) removing the active metal oxide from the second reaction
mixture; and (iii) combining the molecular sieve and the active
metal oxide.
22. An integrated process for making one or more olefin(s), the
integrated process comprising the steps of: (a) passing a hydrocarbon
feedstock to a syngas production zone to produce a synthesis gas
stream; (b) contacting the synthesis gas stream with a catalyst
to form an oxygenated feedstock; and (c) converting thin oxygenated
feedstock into the one or more olefin(s) in the presence of a molecular
sieve catalyst composition comprising a molecular sieve and an active
metal oxide, the metal selected from Group 3 or Lanthanide or Actinide
series elements of the Periodic Table of Elements.
23. The integrated process of claim 22 wherein the oxygenated feedstock
comprises methanol and the olefin(s) include ethylene and propylene.
24. The integrated process of claim 22 wherein the molecular sieve
is a silicoaluminophosphate molecular sieve.
Molecular sieve description
FIELD OF THE INVENTION
The present invention relates to a conversion process utilizing
a molecular sieve composition or a molecular sieve catalyst composition
to form olefin(s). The invention is also directed to a method of
making the molecular sieve composition and the molecular sieve 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 conversion process converts
a feedstock containing methanol in the presence of a molecular sieve
catalyst composition to form one or more olefin(s), primarily ethylene
and/or propylene.
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. These 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. Binders and
matrix materials are typically metal oxides that have a very small
surface area such as less than ten square meters per gram (m.sup.2
/g), more likely less than one m.sup.2 /g of metal oxide. The use
of binders and matrix materials in the formation of molecular sieve
catalyst compositions is well known.
U.S. Pat. No. 4465889 describes a catalyst composition of a silicalite
molecular sieve impregnated with a thorium, zirconium, or a titanium
metal oxide for use in converting methanol, dimethyl ether, or a
mixture thereof into a hydrocarbon product rich in iso-C.sub.4 compounds.
U.S. Pat. No. 6180828 discusses the use of a modified molecular
sieve to produce methylamines from methanol and ammonia, where for
example, a silicoaluminophosphate molecular sieve is combined with
one of the modifiers, a zirconium oxide, a titanium oxide, a yttrium
oxide, montmorillonite or kaolinite.
U.S. Pat. No. 5417949 relates to a process of converting noxious
nitrogen oxides in an oxygen containing effluent into nitrogen and
water using a molecular sieve and a metal oxide binder, where the
preferred binder is titania and the molecular sieve is an aluminosilicate
molecular sieve.
Although the use of binders and matrix materials are known for
use with molecular sieves to form molecular sieve catalyst compositions,
and that these catalyst compositions are useful in a process for
converting oxygenates into olefin(s), these binders and matrix materials
typically only serve to provide desired physical characteristics
to the catalyst composition, and have little to no effect on conversion
and selectivity of the molecular sieve. It would therefore be desirable
to have an improved molecular sieve catalyst composition having
better conversion rates, olefin selectivity, longer lifetimes, and
commercially desirable operability and cost advantages.
SUMMARY OF THE INVENTION
This invention provides for a molecular sieve catalyst composition,
a method for making or formulating the molecular sieve catalyst
composition, and to their use in a conversion process for making
one or more olefin(s), particularly light olefin(s).
In one embodiment the invention is directed to a method for making
the molecular sieve composition of the invention by combining, contacting,
mixing, or the like, a molecular sieve and an active Group 3 metal
oxide or an active oxide of the Lanthanide or Actinide series of
elements. The preferred metal of the Group 3 metal oxide of the
invention are lanthanum, yttrium and scandium. The most preferred
active metal oxides are scandium oxide, lanthanum oxide and yttrium
oxide. More preferably the molecular sieve is synthesized from the
combination of two or more of a silicon source, an aluminum source,
and a phosphorous source, optionally in the presence of a templating
agent.
In another embodiment the invention relates to a method for making
a molecular sieve catalyst composition by combining, contacting,
mixing, or the like, a matrix material, a binder, and at least one
Group 3 metal oxide or at least one oxide of the Lanthanide or Actinide
series elements, wherein the active metal oxide is different from
the binder and/or the matrix material. Preferably the Group 3 metal
oxide is a lanthanum metal oxide, a yttrium metal oxide or a scandium
metal oxide, and the molecular sieve is synthesized from the combination
of two or more of a silicon source, an aluminum source, and a phosphorous
source, optionally in the presence of a templating agent. In a more
preferred embodiment, the molecular sieve, the binder and the matrix
material are made into a formulated molecular sieve catalyst composition
that is then contacted, mixed, combined, spray dried, or the like,
with a Group 3 metal oxide or an oxide of the Lanthanide or Actinide
series elements. In an alternative embodiment, the Group 3 metal
oxide or the oxide of the Lanthanide or Actinide series elements
is included in the spray drying of the formulated molecular sieve
catalyst composition.
In yet another preferred method of the invention, a molecular sieve
catalyst composition is made by a method comprising the steps of:
(i) synthesizing a molecular sieve by the method comprising the
steps of: (a) forming a first reaction mixture of at least one templating
agent and at least two of the group consisting of a silicon source,
a phosphorous source and an aluminum source; and (b) removing the
molecular sieve from the first reaction mixture; (ii) forming a
Group 3 metal oxide and/or an oxide of the Lanthanide or Actinide
series elements by the method comprising the steps of: (a) forming
a second reaction mixture comprising a Group 3 metal oxide precursor
and/or an oxide precursor of the Lanthanide or Actinide series elements
and a precipitating agent, (b) removing the Group 3 metal oxide
and/or the oxide of the Lanthanide or Actinide series elements from
the second reaction mixture; and (iii) combining the molecular sieve
and the active Group 3 metal oxide and/or the active oxide of the
Lanthanide or Actinide series elements.
In yet another embodiment, the invention is directed to a process
for producing olefin(s) in the presence of any of the above molecular
sieve compositions and/or molecular sieve or formulated molecular
sieve catalyst compositions. In particular, the process involves
producing olefin(s) in a process for converting a feedstock, preferably
a feedstock comprising an oxygenate, more preferably a feedstock
comprising an alcohol, and most preferably a feedstock comprising
methanol, in the presence of one or more of the molecular sieve
compositions, or catalyst compositions discussed above.
The invention is also directed to a composition of matter of any
one of the molecular sieve compositions and/or molecular sieve catalyst
compositions described above. The invention is further directed
to the use of a Group 3 metal oxide and/or an oxide of the Lanthanide
or Actinide series elements in combination with a formulated molecular
sieve catalyst composition comprising a matrix material and/or a
binder, a molecular sieve, and where the Group 3 metal oxide and/or
the oxide of the Lanthanide or Actinide series elements is different
from the matrix material and/or the binder, for use in converting
an oxygenated feedstock into one or more olefin(s).
DETAILED DESCRIPTION OF THE INVENTION
Introduction
The invention is directed toward a molecular sieve composition,
to a catalyst composition thereof, and to their use in the conversion
of hydrocarbon feedstocks, particularly oxygenated feedstocks, into
olefin(s). It has been found that combining a molecular sieve with
a Group 3 metal oxide and/or an oxide of the Lanthanide or Actinide
series elements results in a molecular sieve composition or molecular
sieve catalyst composition capable of converting more hydrocarbons,
preferably oxygenates, more particularly methanol, preferably into
one or more olefin(s) per gram of composition. The preferred metal
oxides are those having a Group 3 metal (for example yttrium, scandium
and lanthanum) and the Lanthanide or Actinide series elements (for
example, cerium, neodymium, praseodymium and thorium) from the Periodic
Table of Elements using the IUPAC format described in the CRC Handbook
of Chemistry and Physics, 78th Edition, CRC Press, Boca Raton, Fla.
(1997). Also, surprisingly, the molecular sieve compositions and
catalyst compositions thereof have longer lifetimes because they
are less susceptible to coke formation, which is well known to reduce
conversion of hydrocarbons, preferably oxygenates, into olefin(s).
It has also been discovered that the molecular sieve compositions
and catalyst compositions thereof are more selective to olefin(s)
such as propylene. In this regard, in particular in the conversion
of an oxygenate to at least ethylene and propylene, the amount of
unwanted ethane and propane made is reduced along with other problematic
compounds such as aldehydes and ketones, specifically acetaldehyde.
Lastly, without being bound to any particular theory, it is believed
that because the molecular sieve composition and catalyst compositions
thereof are of a higher density, they tend not to exit a typical
conversion process reactor via the exiting effluent stream or from
the top of a regenerator often utilized to remove coke from a catalyst
composition. The higher density compositions are believed to improve
operability in the overall process and lower, for example, catalyst
composition losses thereby lowering overall conversion costs.
Molecular Sieves
Molecular sieves have various chemical, physical, and 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 topology and connectivity of the tetrahedrally
coordinated atoms constituting the framework, and makes 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 topology or a CHA topology, or a combination
thereof, most preferably a CHA topology.
Crystalline molecular sieve materials all have 3-dimensional, four-connected
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, 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 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 include those 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 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 Al, P and M as tetrahedral
oxides, where M is a metal selected from one of Group IA, IIA, IB,
IIIB, IVB, VB, VIIB, 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 as determined by the DIFFaX method disclosed
in U.S. patent application Ser. No. 09/924106 filed Aug. 7 2001
which is fully incorporated herein by reference.
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
material is formed, and then recovered by filtration, centrifugation
and/or decanting.
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, one or more organic templating
agent, preferably nitrogen containing organic templating agent(s),
and one or more active metal oxides. This particularly preferred
embodiment results in the synthesis of a SAPO crystalline material
that is then isolated by filtration, centrifugation and/or decanting.
Non-limiting examples of silicon sources include a 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 15 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
15 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 compounds including salts thereof,
and tetrabutylammonium compounds 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, 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 TEAOH 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 two or more of a silicon-,
aluminum-, and phosphorous-source.
Generally, the synthesis mixture described above 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.,
preferably from about 100.degree. C. to about 250.degree. C., more
preferably from about 125.degree. C. to about 225.degree. C., even
more preferably from about 150.degree. C. to about 180.degree. C.
In yet another embodiment, the crystallization temperature is increased
gradually or stepwise during synthesis, preferably the crystallization
temperature is maintained constant, for a period of time effective
to form a crystalline product. 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. In one embodiment, the crystalline
product is formed under heating from about 30 minutes to around
2 weeks, preferably from about 45 minutes to about 240 hours, and
more preferably from about 1 hour to about 120 hours.
In one embodiment, the synthesis of a molecular sieve is aided
by seeds from another or the same framework type molecular sieve.
The hydrothermal crystallization is carried out with or without
agitation or stirring, for example stirring or tumbling. The stirring
or agitation during the crystallization period may be continuous
or intermittent, preferably continuous agitation. 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. The isolated
or separated crystalline product, in an embodiment, is washed, typically,
using a liquid such as water, from one to many times. The washed
crystalline product is then optionally dried, preferably in air.
One method for crystallization involves subjecting an aqueous reaction
mixture containing an excess amount of a templating agent, subjecting
the mixture to crystallization under hydrothermal conditions, establishing
an equilibrium between molecular sieve formation and dissolution,
and then, removing some of the excess templating agent and/or organic
base to inhibit dissolution of the molecular sieve. See for example
U.S. Pat. No. 5296208 which is herein fully incorporated by reference.
Other methods for synthesizing molecular sieves or modifying molecular
sieves are described in U.S. Pat. No. 5879655 (controlling the
ratio of the templating agent to phosphorous), U.S. Pat. No. 6005155
(use of a modifier without a salt), U.S. Pat. No. 5475182 (acid
extraction), U.S. Pat. No. 5962762 (treatment with transition
metal), U.S. Pat. Nos. 5925586 and 6153552 (phosphorous modified),
U.S. Pat. No. 5925800 (monolith supported), U.S. Pat. No. 5932512
(fluorine treated), U.S. Pat. No. 6046373 (electromagnetic wave
treated or modified), U.S. Pat. No. 6051746 (polynuclear aromatic
modifier), U.S. Pat. No. 6225254 (heating template), PCT WO 01/36329
published May 25 2001 (surfactant synthesis), PCT WO 01/25151 published
Apr. 12 2001 (staged acid addition), PCT WO 01/60746 published
Aug. 23 2001 (silicon oil), U.S. patent application Ser. No. 09/929949
filed Aug. 15 2001 (cooling molecular sieve), U.S. patent application
Ser. No. 09/615526 filed Jul. 13 2000 (metal impregnation including
copper), U.S. patent application Ser. No. 09/672469 filed Sep.
28 2000 (conductive microfilter), and U.S. patent application Ser.
No. 09/754812 filed Jan. 4 2001(freeze drying the molecular sieve),
which are all herein fully incorporated by reference.
In one preferred embodiment, when a templating agent is used in
the synthesis of a molecular sieve, it is preferred that the templating
agent is substantially, preferably completely, removed after crystallization
by numerous well known techniques, for example, heat treatments
such as calcination. Calcination involves contacting the molecular
sieve containing the templating agent with a gas, preferably containing
oxygen, at any desired concentration at an elevated temperature
sufficient to either partially or completely decompose and oxidize
the templating agent.
Molecular sieve 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.
The pH of a reaction mixture containing at a minimum a silicon-,
aluminum-, and/or phosphorous-composition, and a templating agent,
should be 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.
Group 3 Metal Oxides and Oxides of the Lanthanide or Actinide Series
The Group 3 metal oxides and oxides of the Lanthanide or Actinide
series of the invention are those metal oxides, different from typical
binders and/or matrix materials, that, when used in combination
with a molecular sieve, provide benefits in catalytic conversion
processes. Preferred active metal oxides are those metal oxides
having a Group 3 metal, such as scandium, yttrium and lanthanum,
or a metal from the Lanthanide or Actinide series, such as cerium,
praseodymium, neodymium, samarium, europium, gadolinium, terbium,
dysprosium, holmium, erbium, thulium, ytterbium, lutetium and thorium.
The most preferred active metal oxides are scandium oxide, lanthanum
oxide, yttrium oxide, cerium oxide, praseodymium oxide, neodymium
oxide or mixtures thereof.
While there are many different benefits in catalytic conversion
processes, one of the most desirable is an extension of the catalyst
composition life. Quantification of the extension in the catalyst
composition life is determined by the Lifetime Enhancement Index
(LEI) as defined by the following equation: ##EQU1##
where the lifetime of the catalyst or catalyst composition, is
measured in the same process under the same conditions, and is the
cumulative amount of feedstock processed per gram of catalyst composition
until the conversion of feedstock by the catalyst composition falls
below some defined level, for example 10%. A mixture containing
an inactive metal oxide will have little to no effect on the lifetime
of the catalyst composition, or will shorten the lifetime of the
catalyst composition, and will therefore have a LEI less than or
equal to 1. Active metal oxides of the invention are those Group
3 metal oxides, including oxides of the Lanthanide and Actinide
series that when used in combination with a molecular sieve, provide
a molecular sieve catalyst composition that has a LEI greater than
1. By definition, a molecular sieve catalyst composition that has
not been combined with an active metal oxide will have a LEI equal
to 1.0.
In one embodiment, the active Group 3 metal oxide and/or the active
oxides of the Lanthanide and Actinide series when combined with
a molecular sieve enhances the lifetime of the molecular sieve in
a conversion process of a feedstock comprising methanol, preferably
into one or more olefin(s). In another embodiment, the molecular
sieve composition, molecular sieve catalyst composition, and formulated
molecular sieve catalyst composition of the invention, each containing
an active metal oxide, will have a LEI greater than 1. In a preferred
embodiment, the LEI of the molecular sieve composition, molecular
sieve catalyst composition, or formulated molecular sieve catalyst
composition, all containing one or more Group 3 metal oxides and/or
one or more active oxides of the Lanthanide and Actinide series
is greater than 1.1 preferably greater than 1.3 more preferably
greater than 1.5 even more preferably greater than 1.7 and most
preferably greater than 2. In an alternative embodiment, the LEI
of the molecular sieve composition, molecular sieve catalyst composition,
or formulated molecular sieve catalyst composition, all containing
at least one active Group 3 metal oxide and/or at least one active
oxide of the Lanthanide and Actinide series is in the range of from
greater than 1 to 30 more preferably in the range of from about
1.2 to 25 and most preferably in the range of from about 1.5 to
about 20.
In one embodiment, the active Group 3 metal oxides of the invention,
including oxides of the Lanthanide and Actinide series elements,
are non-acidic or basic metal oxides.
In another embodiment, when combining more than one metal oxide
of the invention with a molecular sieve, the metal oxides are each
made separately and then contacted together, or pre-combined, with
the molecular sieve, or alternatively, each metal oxide is contacted
sequentially with the molecular sieve. In an embodiment, the metal
oxides of the invention are mixed together in a slurry or hydrated
state or in a substantially dry or dried state, preferably the metal
oxides are contacted in a hydrated state.
The metal oxides of the invention are prepared using a variety
of methods. It is preferable that the metal oxide is made from metal
oxide precursors, such as metal salts. Other suitable sources of
the metal oxides include compounds that form these metal oxides
during calcination, such as oxychlorides and nitrates. Alkoxides
are also sources of the metal oxides of the invention, for example
yttrium n-propoxide.
In one embodiment, a preferred Group 3 metal oxide or oxide of
the Lanthanide or Actinide series is hydrothermally treated under
conditions that include a temperature of at least 80.degree. C.,
preferably at least 100.degree. C. The hydrothermal treatment typically
takes place in a sealed vessel at greater than atmospheric pressure.
However, a preferred mode of treatment involves the use of an open
vessel under reflux conditions. Agitation of the Group 3 metal oxide
or the oxide of the Lanthanide or Actinide series in the liquid
medium, for example, by the action of refluxing liquid and/or stirring,
promotes the effective interaction of the oxide with the liquid
medium. The duration of the contact of the oxide with the liquid
medium is preferably at least 1 hour, preferably at least 8 hours.
The liquid medium for this treatment preferably has a pH of about
7 or greater, preferably 9 or greater. Non-limiting examples of
suitable liquid media include water, hydroxide solutions (including
hydroxides of NH.sub.4.sup.+, Na.sup.+, K.sup.+, Mg.sup.2+, and
Ca.sup.2+), carbonate and bicarbonate solutions (including carbonates
and bicarbonates of NH.sub.4.sup.+, Na.sup.+, K.sup.+, Mg.sup.2+,
and Ca.sup.2+), pyridine and its derivatives, and alkyl/hydroxyl
amines.
In yet another embodiment, the active Group 3 metal oxide or the
active oxide of the Lanthanide or Actinide series is prepared, for
example, by first preparing a liquid solution comprising a source
of a Group 3 metal or combination of Group 3 metals or one or more
elements of the Lanthanide or Actinide series of elements. Suitable
sources for the Group 3 metal or the Lanthanide or Actinide series
element include, but are not limited to, salts containing a Group
3 metal or Lanthanide or Actinide element, such as nitrates, sulfates
and halides.
This solution containing a source of a Group 3 metal or a source
of a Lanthanide or Actinide series element, or combinations thereof
is then subjected to conditions sufficient to cause precipitation
of the solid metal oxide, such as by the addition of a precipitating
reagent to the solution. For example, the precipitating agent(s)
preferably is a base such as sodium hydroxide or ammonium hydroxide.
Water is a preferred solvent for these solutions. The temperature
at which the liquid medium(s) is maintained during the precipitation
is preferably less than about 200.degree. C., preferably in the
range of from about 0.degree. C. to about 200.degree. C. This liquid
medium(s) is preferably maintained at an ambient temperature, for
example room temperature or the liquid is cooled or heated. A particular
range of temperatures for precipitation is from about 20.degree.
C. to about 100.degree. C. The resulting gel is preferably then
hydrothermally treated at temperatures of at least 80.degree. C.,
preferably at least 100.degree. C. The hydrothermal treatment typically
takes place in a sealed vessel at greater than atmospheric pressure.
The gel, in one embodiment, is hydrothermally treated for up to
10 days, preferably up to 5 days, most preferably up to 3 days.
The resulting material is then recovered, for example by filtration
or centrifugation, and washed and dried. The resulting material
is preferably then calcined, preferably in an oxidizing atmosphere,
at a temperature of at least 400.degree. C., preferably at least
500.degree. C., and more preferably from about 600.degree. C. to
about 900.degree. C., and most preferably from about 600.degree.
C. to about 800.degree. C. The calcination time is preferably up
to 48 hours, preferably for about 0.5 to 24 hours, and more preferably
for about 1.0 to 10 hours.
Molecular Sieve Composition
The molecular sieve composition of the invention includes any one
of the molecular sieves previously described and one or more of
the Group 3 metal oxides and/or one or more oxide(s) of a Lanthanide
or Actinide series element described above. Most preferably, the
molecular sieves are those resulting from the synthesis mixture
of phosphorous-, aluminum-, and/or silicon-containing components,
preferably while stirring and/or agitation and/or seeding with a
crystalline material, optionally in the presence of an alkali metal,
in a solvent such as water, and one or more templating agents, to
form a synthesis mixture that is then heated under crystallization
conditions of pressure and temperature as described in U.S. Pat.
Nos. 4440871 4861743 5096684 and 5126308 which are all
herein fully incorporated by reference.
In the more preferred embodiment, the molecular sieve is first
formed and is then combined with an active Group 3 metal oxide or
an active oxide of a Lanthanide or Actinide series element, preferably
in a substantially dry, dried, or calcined state, most preferably
the molecular sieve and active Group 3 metal oxide or active oxide
of a Lanthanide or Actinide series element are physically mixed
in their calcined state to form the preferred molecular sieve composition
of the invention. Without being bound by any particular theory,
it is believed that intimate mixing of the molecular sieve and the
active Group 3 metal oxide or the active oxide of a Lanthanide or
Actinide series element improve conversion processes using the molecular
sieve composition and catalyst composition of the invention. Intimate
mixing may be achieved by any method known in the art, such as mixing
with a mixer muller, drum mixer, ribbon/paddle blender, kneader,
or the like.
In one embodiment, the molecular sieve composition or molecular
sieve catalyst composition has a weight ratio of the molecular sieve
to the active Group 3 metal oxide or the active oxide of a Lanthanide
or Actinide series element in the range of from 5 weight percent
to 800 weight percent, particularly in the range from 10 weight
percent to 600 weight percent, more particularly from 20 weight
percent to 500 weight percent, and most preferably from 30 weight
percent to 400 weight percent.
Method for Making Molecular Sieve Catalyst Compositions
Once the molecular sieve is synthesized or the molecular sieve
composition is made, depending on the requirements of the particular
conversion process, the molecular sieve or the molecular sieve composition
is then formulated into a molecular sieve catalyst composition,
particularly for commercial use. A molecular sieve catalyst composition
is made or formulated by combining a molecular sieve synthesized
above or a molecular sieve composition above, with a binder and/or
a matrix material. In one embodiment, where the molecular sieve
synthesized above is formulated into a molecular sieve catalyst
composition, the active Group 3 metal oxide or the active oxide
of a Lanthanide or Actinide series element is then combined with
the formulated molecular sieve catalyst composition. It is also
an embodiment of the invention that a first formulated molecular
sieve catalyst is combined with an active Group 3 metal oxide or
an active oxide of a Lanthanide or Actinide series element that
is then formulated together into a second formulated molecular sieve
catalyst composition. These formulated molecular sieve catalyst
composition are then formed into useful shape and sized particles
by well-known techniques such as spray drying, pelletizing, extrusion,
and the like.
There are many different binders that are useful in forming molecular
sieve catalyst compositions or formulated molecular sieve catalyst
compositions. In one preferred embodiment, the binder is different
from at least one of, most preferably any, of the Group 3 metal
oxides or the oxides of a Lanthanide or Actinide series element
discussed above. 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 chlorhydrol or 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 available from
The PQ Corporation, Valley Forge, Pa.
Preferably, the molecular sieve compositions described above are
combined with one or more matrix material(s). In the preferred embodiment,
the matrix material is different from the Group 3 metal oxide or
the oxide of a Lanthanide or Actinide series element. 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,
and increasing catalyst strength such as crush strength and attrition
resistance.
Non-limiting examples of matrix materials include one or more of:
non-active metal oxides including magnesia, 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 D90 particle size
distribution of less than about 1 .mu.m.
In one embodiment, the binder, the molecular sieve composition
and the matrix material are combined in the presence of a liquid
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 (after calcination).
In another embodiment, the weight ratio of the binder to the matrix
material used in the formation of the molecular sieve catalyst composition
is from 0:1 to 1:15 preferably 1:15 to 1:5 more preferably 1:10
to 1:4 and most preferably 1:6 to 1:5. It has been found that a
higher sieve content, lower matrix content, increases the molecular
sieve catalyst composition performance, however, lower sieve content,
higher matrix material, improves the attrition resistance of the
composition.
Upon combining the molecular sieve composition 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 molecular sieve composition.
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 molecular sieve composition 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 composition, matrix material,
and optional binder, are combined in a liquid as solids, substantially
dry or in a dried form, or as slurries, together or separately.
If solids are added together as dry or substantially dried solids,
it is preferable to add a limited and/or controlled amount of liquid.
In one embodiment, the slurry of the molecular sieve composition,
binder and matrix materials is mixed or milled to achieve a sufficiently
uniform slurry of sub-particles of the molecular sieve catalyst
composition that is then fed to a forming unit that produces the
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, the
slurry of the molecular sieve composition and matrix material, and
optionally a binder, is co-fed to the spray drying volume 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.
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 molecular sieve catalyst composition
or formulated molecular sieve catalyst composition contains from
about 1% to about 80%, more preferably from about 5% to about 60%,
and most preferably from about 5% to about 50%, by weight of the
molecular sieve based on the total weight of the molecular sieve
catalyst composition or formulated molecular sieve catalyst composition.
In another embodiment, the weight percent of binder in or on the
spray dried molecular sieve catalyst composition based on the total
weight of the binder, molecular sieve composition, matrix material
and active Group 3 metal oxide(s) 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.
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 usually 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 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 30 minutes to 15 hours, preferably from 1 hour
to about 10 hours, more preferably from about 1 hour to about 5
hours, and most preferably from about 2 hours to about 4 hours.
In one embodiment, the molecular sieve catalyst composition or
formulated molecular sieve catalyst composition of the invention
has a density in the range of from 0.5 g/cc to 5 g/cc, preferably
from in the range of from 0.6 g/cc to 5 g/cc, more preferably in
the range of from 0.7 g/cc to 4 g/cc, and most preferably in the
range of from 0.8 g/cc to 3 g/cc.
Process for Using the Molecular Sieve Catalyst Compositions
The molecular sieve compositions and 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 compositions and molecular sieve catalyst compositions
and formulated versions thereof 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 and/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 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 MTO process,
typically an oxygenated feedstock, most preferably a methanol containing
feedstock, is converted in the presence of a molecular sieve composition
or 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.
In the most preferred embodiments, the molecular sieve catalyst
composition comprises a silicoaluminophosphate and an active Group
3 metal oxide or oxide of the Lanthanide or Actinide series elements
and the oxygenates include methanol and/or dimethyl ether.
In another embodiment, in a process for conversion an oxygenate
comprising methanol and dimethylether to ethylene and propylene
in the presence of a molecular sieve and an active metal oxide,
preferably a molecular sieve composition of the two, most preferably
a molecular sieve catalyst composition of the two, the production
of ethane and propane is reduced by greater than 10%, preferably
greater than 20%, more preferably greater than 30%, and most preferably
in the range of from about 30% to 50% compared to the molecular
sieve alone or its catalyst composition at the same conversion conditions.
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.
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 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.
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.
The coked molecular sieve catalyst composition is withdrawn from
the disengaging vessel 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 an embodiment, a portion of the 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. 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, preferably 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).
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, the optimum
level of coke on the molecular sieve catalyst composition entering
the reactor is maintained. 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.
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.
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,
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.
The effluent gas removed from a conversion process, particularly
a MTO process, typically has a minor amount of hydrocarbons having
4 or more carbon atoms. The amount of hydrocarbons having 4 or more
carbon atoms is typically in an amount less than 20 weight percent,
preferably less than 10 weight percent, more preferably less than
5 weight percent, and most preferably less than 2 weight percent,
based on the total weight of the effluent gas withdrawn from a MTO
process, excluding water. In particular with a conversion process
of oxygenates into olefin(s) utilizing a molecular sieve catalyst
composition the resulting effluent gas typically comprises a majority
of ethylene and/or propylene and a minor amount of four carbon and
higher carbon number products and other by-products, excluding water.
Non-limiting examples of reaction systems include U.S. Pat. No.
5955640 (converting a four carbon product into butene-1), U.S.
Pat. No. 4774375 (isobutane and butene-2 oligomerized to an alkylate
gasoline), U.S. Pat. No. 6049017 (dimerization of n-butylene),
U.S. Pat. Nos. 4287369 and 5763678 (carbonylation or hydroformulation
of higher olefins with carbon dioxide and hydrogen making carbonyl
compounds), U.S. Pat. No. 4542252 (multistage adiabatic process),
U.S. Pat. No. 5634354 (olefin-hydrogen recovery), and Cosyns,
J. et al., Process for Upgrading C3 C4 and C5 Olefinic Streams,
Pet. & Coal, Vol. 37 No. 4 (1995) (dimerizing or oligomerizing
propylene, butylene and pentylene), which are all herein fully incorporated
by reference.
The preferred light olefin(s) produced by any one of the processes
described above, preferably conversion processes, are high purity
prime olefin(s) products that contains a single carbon number olefin
in an amount greater than 80 percent, preferably greater than 90
weight percent, more preferably greater than 95 weight percent,
and most preferably no less than about 99 weight percent, based
on the total weight of the olefin.
In one embodiment, high purity prime olefin(s) are produced in
the process of the invention at rate of greater than 5 kg per day,
preferably greater than 10 kg per day, more preferably greater than
20 kg per day, and most preferably greater than 50 kg per day. In
another embodiment, high purity ethylene and/or high purity propylene
is produced by the process of the invention at a rate greater than
4500 kg per day, preferably greater than 100000 kg per day, more
preferably greater than 500000 kg per day, even more preferably
greater than 1000000 kg per day, yet even more preferably greater
than 1500000 kg per day, still even more preferably greater than
2000000 kg per day, and most preferably greater than 2500000
kg per day.
In an embodiment, an integrated process is directed to producing
light olefin(s) from a hydrocarbon feedstock, preferably a hydrocarbon
gas feedstock, more preferably methane and/or ethane. The first
step in the process is passing the gaseous feedstock, preferably
in combination with a water stream, to a syngas production zone
to produce a synthesis gas (syngas) stream. Syngas production is
well known, and typical syngas temperatures are in the range of
from about 700.degree. C. to about 1200.degree. C. and syngas pressures
are in the range of from about 2 MPa to about 100 MPa. Synthesis
gas streams are produced from natural gas, petroleum liquids, and
carbonaceous materials such as coal, recycled plastic, municipal
waste or any other organic material, preferably synthesis gas stream
is produced via steam reforming of natural gas.
Generally, a heterogeneous catalyst, typically a copper based catalyst,
is contacted with a synthesis gas stream, typically carbon dioxide
and carbon monoxide and hydrogen to produce an alcohol, preferably
methanol, often in combination with water. In one embodiment, the
synthesis gas stream at a synthesis temperature in the range of
from about 150.degree. C. to about 450.degree. C. and at a synthesis
pressure in the range of from about 5 MPa to about 10 MPa is passed
through a carbon oxide conversion zone to produce an oxygenate containing
stream.
This oxygenate containing stream, or crude methanol, typically
contains the alcohol product and various other components such as
ethers, particularly dimethyl ether, ketones, aldehydes, dissolved
gases such as hydrogen methane, carbon oxide and nitrogen, and fuel
oil. The oxygenate containing stream, crude methanol, in the preferred
embodiment is passed through a well known purification processes,
distillation, separation and fractionation, resulting in a purified
oxygenate containing stream, for example, commercial Grade A and
AA methanol.
The oxygenate containing stream or purified oxygenate containing
stream, optionally with one or more diluents, is contacted with
one or more molecular sieve catalyst composition described above
in any one of the processes described above to produce a variety
of prime products, particularly light olefin(s), ethylene and/or
propylene. Non-limiting examples of this integrated process is described
in EP-B-0 933 345 which is herein fully incorporated by reference.
In another more fully integrated process, optionally with the integrated
processes described above, olefin(s) produced are directed to, in
one embodiment, one or more polymerization processes for producing
various polyolefins. (See for example U.S. patent application Ser.
No. 09/615376 filed Jul. 13 2000 which is herein fully incorporated
by reference.)
Polymerization processes include solution, gas phase, slurry phase
and a high pressure processes, or a combination thereof. Particularly
preferred is a gas phase or a slurry phase polymerization of one
or more olefin(s) at least one of which is ethylene or propylene.
These polymerization processes utilize a polymerization catalyst
that can include any one or a combination of the molecular sieve
catalysts discussed above, however, the preferred polymerization
catalysts are those Ziegler-Natta, Phillips-type, metallocene, metallocene-type
and advanced polymerization catalysts, and mixtures thereof.
In preferred embodiment, the integrated process comprises a polymerizing
process of one or more olefin(s) in the presence of a polymerization
catalyst system in a polymerization reactor to produce one or more
polymer products, wherein the one or more olefin(s) having been
made by converting an alcohol, particularly methanol, using a molecular
sieve catalyst composition. The preferred polymerization process
is a gas phase polymerization process and at least one of the olefins(s)
is either ethylene or propylene, and preferably the polymerization
catalyst system is a supported metallocene catalyst system. In this
embodiment, the supported metallocene catalyst system comprises
a support, a metallocene or metallocene-type compound and an activator,
preferably the activator is a non-coordinating anion or alumoxane,
or combination thereof, and most preferably the activator is alumoxane.
The polymers produced by the polymerization processes described
above include linear low density polyethylene, elastomers, plastomers,
high density polyethylene, low density polyethylene, polypropylene
and polypropylene copolymers. The propylene based polymers produced
by the polymerization processes include atactic polypropylene, isotactic
polypropylene, syndiotactic polypropylene, and propylene random,
block or impact copolymers.
EXAMPLES
In order to provide a better understanding of the present invention
including representative advantages thereof, the following examples
are offered.
LEI is defined as the ratio of the lifetime of the molecular sieve
composition, or the catalyst composition described below, to that
of the molecular sieve in the absence of a metal oxide as discussed
above. For the purpose of determining LEI, lifetime is defined as
the cumulative oxygenate converted, preferably into one or more
olefin(s) per gram of molecular sieve, wherein the conversion rate
drops to about 10%. If the conversion has not reached 10% by the
end of the experiment, lifetime is estimated by linear extrapolation
based on the rate of decrease in conversion over the last two data
points in the experiment. For the purposes of determining the LEI
for the following examples in a preferred oxygenate conversion process,
methanol is converted to one or more olefin(s) at 475.degree. C.,
25 psig (172 kPag) and a methanol weight hourly space velocity of
100 h.sup.-1.
In Table 1 "Prime Olefin" is the sum of the selectivity
to ethylene and propylene. The ratio "C.sub.2.sup..dbd. /C.sub.3.sup..dbd.
" is the ratio of the ethylene to propylene selectivity weighted
over the run. The "C.sub.3 Purity" is calculated by dividing
the propylene selectivity by the sum of the propylene and propane
selectivity. In Table 2 the selectivity for methane, ethylene,
ethane, propylene, propane, C.sub.4 's and C.sub.5 +'s are average
selectivity weighted over the run. Note that the C.sub.5 +'s consist
only of C.sub.5 's, C.sub.6 's and C.sub.7 's. The terms "C.sub.4
's, C.sub.5 +, etc." refer to the number of carbons in the
hydrocarbon. The selectivity values do not sum to 100% in the Tables
because they have been corrected for coke as is well known.
Example A
Preparation of a Molecular Sieve
There are numerous methods well known for making molecular sieves.
The following is an example preparation of a molecular sieve, particularly
a silicoaluminophosphate molecular sieve, more particularly a SAPO-34
used in the compositions in these Examples, and referenced as MSA.
The MSA, SAPO-34 molecular sieve, was crystallized in the presence
of tetraethyl ammonium hydroxide (R1) and dipropyl amine (R2) as
the organic structure directing agents or templating agents. A mixture
of the following mole ratio composition was prepared:
An amount of Condea Pural SB was mixed with deionised water, to
form a slurry. To this slurry was added an amount of phosphoric
acid (85%). These additions were made with stirring to form a homogeneous
mixture. To this homogeneous mixture Ludox AS40 (40% of SiO2) was
added, followed by the addition of R1 with mixing to form a homogeneous
mixture. To this homogeneous mixture R2 was added. This homogeneous
mixture was then crystallized with agitation in a stainless steel
autoclave by heating to 170.degree. C. for 40 hours. This provided
a slurry of the crystalline molecular sieve. The crystals were then
separated from the mother liquor by filtration.
Formulation of a Molecular Sieve
There are a variety of methods for making or formulating a molecular
sieve, a matrix material and a binder into a molecular sieve catalyst
composition. The following is an example of making a molecular sieve
catalyst composition. The crystalline molecular sieve prepared above
was thoroughly mixed with water to form a molecular sieve slurry
(A1). This slurry (A1) was then added to another slurry (A2) of
a binder (for example, preferably aluminum chlorhydrol) and water,
and was then again mixed thoroughly. As a final step in the formulation
process, a matrix material (A3) (for example, a clay material) was
then added to the mixture of A1 and A2 mixed well to form a homogeneous
mixture (A4). This mixture (A4) was then fed to a drier, preferably
a spray drier, under conditions sufficient to produce a formulated
molecular sieve catalyst composition composed of particles having
the desired size and dryness. Spray drying is well known, and is
further discussed in this patent specification. The molecular sieve
catalyst composition produced is then calcined at an elevated temperature
sufficient to further dry and harden the spray dried molecular sieve
catalyst composition or formulated molecular sieve catalyst composition.
The catalyst composition is then packaged under a dry atmosphere
for use, storage or shipment.
Example B
Conversion Process
All catalytic or conversion data presented was obtained using a
microflow reactor. The microflow reactor consists of a stainless
steel reactor (1/4 inch (0.64 cm) outer diameter) located in a furnace
to which vaporized methanol is fed. The reactor is maintained at
a temperature of 475.degree. C. and a pressure of 25 psig (172.4
kPag). The flow rate of the methanol is such that the flow rate
of methanol on weight basis per gram of molecular sieve, also known
as the weight hourly space velocity (WHSV) was 100 h.sup.-1. Product
gases exiting the reactor are collected and analyzed using gas chromatography.
The molecular sieve alone or the molecular sieve composition load
was 50 mg and the reactor bed was diluted with quartz to minimize
hot spots in the reactor. In particular, for the catalyst composition
of the invention, the molecular sieve and active Group 3 metal oxide
or oxide of the Lanthanide or Actinide series elements, a physical
mixture of the MSA molecular sieve of Example A and the active metal
oxide was used. The total catalyst composition load remained 50
mg, 40 mg of the molecular sieve catalyst composition and 10 mg
of the Group 3 metal oxide, and the methanol flow rate was adjusted
as the amount of molecular sieve in the reactor bed was changed
by the addition of the active metal oxide such that the methanol
WHSV was 100 h.sup.-1 based on the amount of molecular sieve in
the reactor bed. |