Molecular sieve abstract
The invention relates to a catalyst composition, a method of making
the same and its use in the conversion of a feedstock, preferably
an oxygenated feedstock, into one or more olefin(s), preferably
ethylene and/or propylene. The catalyst composition comprises a
molecular sieve and at least one oxide of a metal from Group 4
optionally in combination with at least one metal from Groups 2
and 3 of the Periodic Table of Elements.
Molecular sieve claims
We claim:
1. A catalyst composition comprising a molecular sieve and at least
one oxide of a metal selected from Group 4 of the Periodic Table
of Elements, wherein said metal oxide has an uptake of carbon dioxide
at 100.degree. C. of at least 0.03 mg/m.sup.2 of the metal oxide.
2. The catalyst composition of claim 1 wherein said metal oxide
has an uptake of carbon dioxide at 100.degree. C. of at least 0.035
mg/m.sup.2 of the metal oxide.
3. The catalyst composition of claim 1 wherein said metal oxide
has an uptake of carbon dioxide at 100.degree. C. of less than 10
mg/m.sup.2 of the metal oxide.
4. The catalyst composition of claim 1 wherein said metal oxide
has an uptake of carbon dioxide at 100.degree. C. of less than 5
mg/m.sup.2 of the metal oxide.
5. The catalyst composition of claim 1 and also including at least
one of a binder and a matrix material different from said metal
oxide.
6. The catalyst composition of claim 1 wherein said metal oxide
has a surface area greater than 10 m.sup.2 /g.
7. The catalyst composition of claim 1 and also including a binder
and a matrix material each being different from one another and
from said metal oxide.
8. The catalyst composition of claim 7 wherein the binder is an
alumina sol and the matrix material is a clay.
9. The catalyst composition of claim 1 wherein said metal oxide
is selected from zirconium oxide and hafnium oxide.
10. The catalyst composition of claim 1 and also including an oxide
of a metal selected from Group 2 and Group 3 of the Periodic Table
of Elements.
11. The catalyst composition of claim 10 wherein the Group 4 metal
oxide comprises zirconium oxide and the Group 2 and/or Group 3 metal
oxide comprises one or more oxides selected from the group consisting
of calcium oxide, barium oxide, lanthanum oxide, yttrium oxide and
scandium oxide.
12. The catalyst composition of claim 1 wherein the molecular sieve
comprises a framework inciuding at least two tetrahedral units selected
from [SiO.sub.4 ], [AlO.sub.4 ] and [P0.sub.4 ] units.
13. The catalyst composition of claim 12 wherein the molecular
sieve comprises a silicoaluminophosphate.
14. The catalyst composition of claim 12 wherein the molecular
sieve comprises a CHA framework-type molecular sieve.
15. The catalyst composition of claim 14 wherein the molecular
sieve further comprises an AEI framework-type molecular sieve.
16. The catalyst composition of claim 1 wherein the weight ratio
of the molecular sieve to metal oxide is in the range of from 5
percent to 800 percent.
17. A molecular sieve catalyst composition comprising an active
Group 4 metal oxide and a Group 2 and/or a Group 3 metal oxide,
a binder, a matrix material, and a silicoaluminophosphate molecular
sieve.
18. A method for making a catalyst composition, the method comprising
physically mixing first particles comprising a molecular sieve with
second particles comprising a Group 4 metal oxide having an uptake
of carbon dioxide at 100.degree. C. of at least 0.03 mg/m.sup.2
of the metal oxide particles.
19. The method of claim 18 wherein said second particles have a
surface area greater than 10 m.sup.2 /g.
20. The method of claim 18 wherein said second particles have a
surface area greater than 15 m.sup.2 /g.
21. The method of claim 18 wherein said first particles comprise
a silicoaluminophosphate molecular sieve and/or an aluminophosphate
molecular sieve.
22. The method of claim 18 wherein at least one said first and
said second particles also include at least one of a binder and
a matrix material.
23. The method of claim 18 wherein said first particles comprise
a silicoaluminophosphate molecular sieve, a binder including an
alumina sol and a matrix material including a clay.
24. The method of claim 18 wherein said second particles also comprise
a Group 2 and/or Group 3 metal oxide.
25. The method of claim 18 wherein said second particles comprise
zirconium oxide and at least one of calcium oxide, barium oxide,
lanthanum oxide, yttrium oxide and scandium oxide.
26. A method of making a catalyst composition, the method comprising:
(i) synthesizing a molecular sieve from a reaction mixture comprising
at least one templating agent and at least two of a silicon source,
a phosphorus source and an aluminum source; and (ii) recovering
the molecular sieve synthesized in (i); (iii) forming a hydrated
precursor of a Group 4 metal oxide by precipitation from a solution
containing a source of Group 4 metal ions; (iv) recovering the hydrated
precursor formed in (iii); (v) calcining the hydrated precursor
recovered (iv) to form a calcined Group 4 metal oxide that has an
uptake of carbon dioxide at 100.degree. C. of at least 0.03 mg/m.sup.2
of the metal oxide; and (vi) physically mixing the molecular sieve
recovered in (i) and the calcined metal oxide produced in (v).
27. The method of claim 26 wherein the molecular sieve and/or the
Group 4 metal oxide is combined with a binder and/or a matrix material
prior to (vi).
28. The method of claim 26 wherein the weight ratio of the molecular
sieve to the calcined metal oxide is in the range of from 30 percent
to 400 percent.
29. The method of claim 26 wherein the calcined metal oxide has
a surface area greater than 10 m.sup.2 /g.
30. The method of claim 26 wherein the molecular sieve is spray
dried with a matrix material and a binder prior to (vi).
31. The method of claim 30 wherein the molecular sieve is a silicoaluminophosphate,
the binder is an alumina sol and the matrix material is a clay.
32. The method of claim 26 wherein a mixed metal oxide is produced
in (iii) by precipitation from at least one solution containing
a Group 4 metal oxide precursor and at least one of a Group 2 metal
oxide precursor and a Group 3 metal oxide precursor.
33. The method of claim 26 wherein said precipitation is conducted
at a pH above 7.
34. The method of claim 26 wherein (iii) also includes hydrothermally
treating the precipitate at a temperature of at least 80.degree.
C. for up to 10 days.
35. The method of claim 26 wherein (v) is conducted at a temperature
in the range of from about 400.degree. C. to about 900.degree. C.
Molecular sieve description
FIELD
The present invention relates to molecular sieve compositions and
catalysts containing the same, to the synthesis of such compositions
and catalysts and to the use of such compositions and catalysts
in conversion processes to produce olefin(s).
BACKGROUND
Olefins are traditionally produced from petroleum feedstocks 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 feedstocks. 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 or 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. Other known syngas production
processes 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 process for converting a
feedstock containing methanol into one or more olefin(s), primarily
ethylene and/or propylene, involves contacting the feedstock with
a molecular sieve catalyst composition.
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 sieve 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 the 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 aluminophosphate, often designated
AlPO.sub.4.
Some of the most useful molecular sieves for converting methanol
to olefin(s) are silicoaluminophosphate molecular sieves. Silicoaluminophosphate
(SAPO) molecular sieves contain a three-dimensional microporous
crystalline framework structure of [SiO.sub.4 ], [AlO.sub.4 ] and
[PO.sub.4 ] corner sharing tetrahedral units. SAPO synthesis is
described in U.S. Pat. No. 4440871 which is herein fully incorporated
by reference. SAPO molecular sieves are 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, are disclosed
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 the 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.
Although it is known to use binders and matrix materials to form
molecular sieve catalyst compositions useful in 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 a better
conversion rate, improved olefin selectivity and a longer lifetime.
U.S. Pat. No. 4465889 describes a catalyst composition comprising
a silicalite molecular sieve impregnated with a thorium, zirconium,
or 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 or more modifiers, such as a zirconium oxide, a titanium oxide,
an yttrium oxide, montmorillonite or kaolinite.
U.S. Pat. No. 5417949 relates to a process for 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.
EP-A-312981 discloses a process for cracking vanadium-containing
hydrocarbon feed streams using a catalyst composition comprising
a physical mixture of a zeolite embedded in an inorganic refractory
matrix material and at least one oxide of beryllium, magnesium,
calcium, strontium, barium or lanthanum, preferably magnesium oxide,
on a silica-containing support material.
Kang and Inui, Effects of decrease in number of acid sites located
on the external surface of Ni-SAPO-34 crystalline catalyst by the
mechanochemical method, Catalysis Letters 53 pages 171-176 (1998)
disclose that the shape selectivity can be enhanced and the coke
formation mitigated in the conversion of methanol to ethylene over
Ni-SAPO-34 by milling the catalyst with MgO, CaO, BaO or Cs.sub.2
O on microspherical non-porous silica, with BaO being the most preferred.
International Publication No. WO 98/29370 discloses the conversion
of oxygenates to olefins over a small pore non-zeolitic molecular
sieve containing a metal selected from the group consisting of a
lanthanide, an actinide, scandium, yttrium, a Group 4 metal, a Group
5 metal or combinations thereof.
SUMMARY
In one aspect, the invention resides in a catalyst composition
comprising a molecular sieve and at least one oxide of a metal selected
from Group 4 of the Periodic Table of Elements, wherein said metal
oxide has an uptake of carbon dioxide at 100.degree. C. of at least
0.03 and typically at least 0.035 mg/m.sup.2 of the metal oxide.
The catalyst composition may also include at least one of a binder
and a matrix material different from said metal oxide.
The catalyst composition may also include an oxide of a metal selected
from Group 2 and Group 3 of the Periodic Table of Elements. In one
embodiment, the Group 4 metal oxide comprises zirconium oxide and
the Group 2 and/or Group 3 metal oxide comprises one or more oxides
selected from calcium oxide, barium oxide, lanthanum oxide, yttrium
oxide and scandium oxide.
The molecular sieve conveniently comprises a framework including
at least two tetrahedral units selected from [SiO.sub.4 ], [AlO.sub.4
] and [PO.sub.4 ] units, such as a silicoaluminophosphate.
In another aspect, the invention resides in a molecular sieve catalyst
composition comprising an active Group 4 metal oxide and a Group
2 and/or a Group 3 metal oxide, a binder, a matrix material, and
a silicoaluminophosphate molecular sieve.
In another aspect, the invention resides in a method for making
a catalyst composition, the method comprising the step of physically
mixing first particles comprising a molecular sieve with second
particles comprising a Group 4 metal oxide having an uptake of carbon
dioxide at 100.degree. C. of at least 0.03 mg/m.sup.2 of the metal
oxide particles.
In one embodiment, the molecular sieve, a binder and a matrix material
are made into a formulated molecular sieve catalyst composition
that is then contacted, mixed, combined, spray dried, or the like,
with an active Group 4 metal oxide, such as an active zirconium
metal oxide and/or an active hafnium metal oxide, optionally in
the presence of a Group 2 and/or a Group 3 metal oxide.
In another aspect, the invention resides in a method of making
a catalyst composition, the method comprising: (i) synthesizing
a molecular sieve from a reaction mixture comprising at least one
templating agent and at least two of a silicon source, a phosphorus
source and an aluminum source; and (ii) recovering the molecular
sieve synthesized in step (i); (iii) forming a hydrated precursor
to a Group 4 metal oxide by precipitation from a solution containing
a source of Group 4 metal metal ions; (iv) recovering the hydrated
precursor formed in step (iii); (v) calcining the hydrated precursor
recovered in step (iv) to form a calcined metal oxide that has an
uptake of carbon dioxide at 100.degree. C. of at least 0.03 mg/m.sup.2
of the metal oxide; and (vi) physically mixing the molecular sieve
recovered in step (i) and the calcined metal oxide of step (v).
In yet another aspect, the invention is directed to a process for
producing olefin(s) by converting a feedstock, such as an oxygenate,
conveniently an alcohol, for example methanol, in the presence of
any of the above molecular sieve compositions and/or molecular sieve
or formulated molecular sieve catalyst compositions.
In yet another aspect, the invention is directed to a process for
converting a feedstock into 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 mixture of metal oxides
different from the binder and the matrix material.
In one embodiment, the catalyst composition has a Lifetime Enhancement
Index (LEI) greater than 1 such as greater than 1.5. LEI is defined
herein as the ratio of the lifetime of the catalyst composition
to that of the same catalyst composition in the absence of an active
metal oxide.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Introduction
The invention is directed to a molecular sieve catalyst composition
and to its use in the conversion of hydrocarbon feedstocks, particularly
oxygenated feedstocks, into olefin(s). It has been found that combining
a molecular sieve with one or more active metal oxides results in
a catalyst composition with an enhanced olefin yield and/or a longer
lifetime when used in the conversion of feedstocks, such as oxygenates,
more particularly methanol, into olefin(s). In addition, the resultant
catalyst composition tends to be more propylene selective and to
yield lower amounts of unwanted ethane and propane, together with
other undesirable compounds, such as aldehydes and ketones, specifically
acetaldehyde.
The preferred active metal oxides are those having a Group 4 metal
(for example zirconium and hafnium) 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). In
some cases, it is found that improved results are obtained when
the catalyst composition also contains at least one oxide of a metal
selected from Group 2 and/or Group 3 of the Periodic Table of Elements.
Molecular Sieves
Molecular sieves have been classified by the Structure Commission
of the International Zeolite Association according to the rules
of the IUPAC Commission on Zeolite Nomenclature. According to this
classification, 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.
Crystalline molecular sieves all have a 3-dimensional, four-connected
framework structure of corner-sharing [TO.sub.4 ] tetrahedra, where
T is any tetrahedrally coordinated cation. 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).
Non-limiting examples of 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 preferred molecular sieves, particularly for converting an oxygenate
containing feedstock into olefin(s), include AEL, AFY, AEI, 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.
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
and an average pore size in the range of from about 3 .ANG. to 15
.ANG.. In a more preferred embodiment, the molecular sieves, preferably
silicoaluminophosphate molecular sieves, have 8-rings and an average
pore size less than about 5 .ANG., such as in the range of from
3 .ANG. to about 5 .ANG., for example from 3 .ANG. to about 4.5
.ANG., and particularly 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 phosphorus based
molecular sieves and metal containing derivatives thereof 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 molecular sieves include aluminophosphate (AlPO)
molecular sieves and silicoaluminophosphate (SAPO) molecular sieves
and substituted, preferably metal substituted, AlPO and SAPO molecular
sieves. The most preferred molecular sieves are SAPO molecular sieves,
and metal substituted SAPO molecular sieves. In an embodiment, the
metal is an alkali metal of Group 1 of the Periodic Table of Elements,
an alkaline earth metal of Group 2 of the Periodic Table of Elements,
a rare earth metal of Group 3 of the Periodic Table of Elements,
including the Lanthanides: lanthanum, cerium, praseodymium, neodymium,
samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,
thulium, ytterbium and lutetium; and scandium or yttrium, a transition
metal of Groups 4 to 12 of the Periodic Table of Elements, or mixtures
of any of these metal species. In one preferred embodiment, the
metal is selected from the group consisting of Co, Cr, Cu, Fe, Ga,
Ge, Mg, Mn, Ni, Sn, Ti, Zn and Zr, and mixtures thereof. In another
preferred embodiment, these metal atoms discussed above are inserted
into the framework of a molecular sieve through a tetrahedral unit,
such as [MeO.sub.2 ], and carry a net charge depending on the valence
state of the metal substituent. For example, in one embodiment,
when the metal substituent has a valence state of +2 +3 +4 +5
or +6 the net charge of the tetrahedral unit is between -2 and
+2.
In one embodiment, the molecular sieve, as described in many of
the U.S. patents mentioned above, is represented by the empirical
formula, on an anhydrous basis:
wherein R represents at least one templating agent, preferably
an organic templating agent; m is the number of moles of R per mole
of (M.sub.x Al.sub.y P.sub.z)O.sub.2 and 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 Groups 1 2 3 4 5 6
7 8 9 10 11 12 13 14 and Lanthanide's of the Periodic Table
of Elements, preferably M is selected from one of the group consisting
of Si, 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 useful
herein 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.
Of these, particularly useful molecular sieves are one or a combination
of SAPO-18 SAPO-34 SAPO-35 SAPO-44 SAPO-56 AlPO-18 and AlPO-34
and metal containing derivatives thereof, such as one or a combination
of SAPO-18 SAPO-34 AlPO-34 and AlPO-18 and metal containing derivatives
thereof, and especially one or a combination of SAPO-34 and AlPO-18
and metal containing derivatives thereof.
In an embodiment, the molecular sieve is an intergrowth material
having two or more distinct crystalline phases 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 International Publication No. 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. Thus the molecular sieve used
herein may comprise at least one intergrowth phase of AEI and CHA
framework-types, especially where the ratio of CHA framework-type
to AEI framework-type, as determined by the DIFFaX method disclosed
in U.S. patent application Ser. No. 09/924106 filed Aug. 7 2001
is greater than 1:1.
Molecular Sieve Synthesis
The synthesis of molecular sieves is described in many of the references
discussed above. Generally, molecular sieves are synthesized by
the hydrothermal crystallization of one or more of a source of aluminum,
a source of phosphorus, a source of silicon and a templating agent,
such as a nitrogen containing organic compound. Typically, a combination
of sources of silicon, aluminum and phosphorus, optionally with
one or more templating agents, is 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.
Non-limiting examples of silicon sources include silicates, fumed
silica, for example, Aerosil-200 available from Degussa Inc., New
York, N.Y., and CAB-O-SIL M-5 organosilicon 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 or any combination thereof.
Non-limiting examples of aluminum sources include aluminum alkoxides,
for example aluminum isopropoxide, aluminum phosphate, aluminum
hydroxide, sodium aluminate, pseudo-boehmite, gibbsite and aluminum
trichloride, or any combination thereof. A convenient source of
aluminum is pseudo-boehmite, particularly when producing a silicoaluminophosphate
molecular sieve.
Non-limiting examples of phosphorus sources, which may also include
aluminum-containing phosphorus compositions, include phosphoric
acid, organic phosphates such as triethyl phosphate, and crystalline
or amorphous aluminophosphates such as AlPO.sub.4 phosphorus salts,
or combinations thereof. A convenient source of phosphorus 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. Typical templating agents also
contain at least one alkyl or aryl group, such as an alkyl or aryl
group having from 1 to 10 carbon atoms, for example from 1 to 8
carbon atoms. Preferred templating agents are often nitrogen-containing
compounds, such as amines, quaternary ammonium compounds and combinations
thereof. Suitable quaternary ammonium compounds 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.
Non-limiting examples of templating agents include tetraalkyl ammonium
compounds including salts thereof, such as tetramethyl ammonium
compounds, tetraethyl ammonium compounds, tetrapropyl ammonium compounds,
and tetrabutylammonium compounds, 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 pH of the synthesis mixture containing at a minimum a silicon-,
aluminum-, and/or phosphorus-composition, and a templating agent,
is generally in the range of from 2 to 10 such as from 4 to 9
for example from 5 to 8.
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.,
such as from about 100.degree. C. to about 250.degree. C., for example
from about 125.degree. C. to about 225.degree. C., such as from
about 150.degree. C. to about 180.degree. C.
In one embodiment, the synthesis of a molecular sieve is aided
by seeds from another or the same framework type molecular sieve.
The time required to form the crystalline product is usually dependent
on the temperature and can vary from immediately up to several weeks.
Typically the crystallization time is from about 30 minutes to around
2 weeks, such as from about 45 minutes to about 240 hours, for example
from about 1 hour to about 120 hours. The hydrothermal crystallization
may be carried out with or without agitation or stirring.
Once the crystalline molecular sieve product is formed, usually
in a slurry state, it may be recovered by any standard technique
well known in the art, for example, by centrifugation or filtration.
The recovered crystalline product may then be washed, such as with
water, and then dried, such as in air.
One method for crystallization involves producing 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 phosphorus), 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 (phosphorus 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.
Where a templating agent is used in the synthesis of the molecular
sieve, any templating agent retained in the product may be removed
after crystallization by numerous well known techniques, for example,
by 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 remove the templating
agent.
Aluminosilicate and silicoaluminophosphate molecular sieves have
either a high silicon (Si) to aluminum (Al) ratio or a low silicon
to aluminum ratio, however, a low Si/Al ratio is preferred for SAPO
synthesis. In one embodiment, the molecular sieve has a Si/Al ratio
less than 0.65 such as less than 0.40 for example less than 0.32
and particularly 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 such as from about 0.40 to about 0.10 for example from about
0.32 to about 0.10 and particularly from about 0.32 to about 0.15.
Active Metal Oxides
Active metal oxides useful herein 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 4 metal, such as zirconium and/or hafnium,
either alone or in combination with a Group 2 (for example magnesium,
calcium, strontium and barium) and/or a Group 3 metal (including
the Lanthanides and Actinides) oxide (for example yttrium, scandium
and lanthanum). The most preferred active Group 4 metal oxide is
an active zirconium metal oxide, either alone or in combination
with calcium oxide, barium oxide, lanthanum oxide and/or yttrium
oxide. In general, oxides of silicon, aluminum, and combinations
thereof are not preferred.
In one embodiment, active metal oxides are those metal oxides,
different from typical binders and/or matrix materials that, when
used in combination with a molecular sieve in a catalyst composition,
are effective in extending of the useful life of the catalyst composition.
Quantification of the extension in catalyst 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, in
the same process under the same conditions, 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%. 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. Thus active metal
oxides 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 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.
It is found that, by including an active metal oxide in combination
with a molecular sieve, a catalyst composition can be produced having
an LEI in the range of from greater than 1 to 20 such as from about
1.5 to about 10. Typically catalyst compositions according to the
invention exhibit LEI values greater than 1.1 for example in the
range of from about 1.2 to 15 and more particularly greater than
1.3 such as greater than 1.5 such as greater than 1.7 such as
greater than 2.
In one embodiment, the active metal oxide when combined with a
molecular sieve in a catalyst composition enhances the lifetime
of the catalyst composition in the conversion of a feedstock comprising
methanol, preferably into one or more olefin(s).
In particular, the metal oxides useful herein have an uptake of
carbon dioxide at 100.degree. C. of at least 0.03 mg/m.sup.2 of
the metal oxide, such as at least 0.035 mg/m.sup.2 of the metal
oxide. Although the upper limit on the carbon dioxide uptake of
the metal oxide is not critical, in general the metal oxides useful
herein will have a carbon dioxide at 100.degree. C. of less than
10 mg/m.sup.2 of the metal oxide, such as less than 5 mg/m.sup.2
of the metal oxide. Typically, the metal oxides useful herein have
a carbon dioxide uptake of 0.04 to 0.2 mg/m.sup.2 of the metal oxide.
In order to determine the carbon dioxide uptake of a metal oxide,
the following procedure is adopted. A sample of the metal oxide
is dehydrated by heating the sample to about 200.degree. C. to 500.degree.
C. in flowing air until a constant weight, the "dry weight",
is obtained. The temperature of the sample is then reduced to 100.degree.
C. and carbon dioxide is passed over the sample, either continuously
or in pulses, again until constant weight is obtained. The increase
in weight of the sample in terms of mg/mg of the sample based on
the dry weight of the sample is the amount of adsorbed carbon dioxide.
In the Examples reported below, the carbon dioxide adsorption is
measured using a Mettler TGA/SDTA 851 thermogravimetric analysis
system under ambient pressure. The metal oxide sample is dehydrated
in flowing air to about 500.degree. C. for one hour. The temperature
of the sample is then reduced in flowing helium to 100.degree. C.
After the sample has equilibrated at the desired adsorption temperature
in flowing helium, the sample is subjected to 20 separate pulses
(about 12 seconds/pulse) of a gaseous mixture comprising 10-weight
% carbon dioxide with the remainder being helium. After each pulse
of the adsorbing gas the metal oxide sample is flushed with flowing
helium for 3 minutes. The increase in weight of the sample in terms
of mg/mg adsorbent based on the adsorbent weight after treatment
at 500.degree. C. is the amount of adsorbed carbon dioxide. The
surface area of the sample is measured in accordance with the method
of Brunauer, Emmett, and Teller (BET) published as ASTM D 3663 to
provide the carbon dioxide uptake in terms of mg carbon dioxide/m.sup.2
of the metal oxide.
In one embodiment, the active metal oxide(s) has a BET surface
area of greater than 10 m.sup.2 /g, such as greater than 10 m.sup.2
/g to about 300 m.sup.2 /g. In another embodiment, the active metal
oxide(s) has a BET surface area greater than 20 m.sup.2 /g, such
as from 20 m.sup.2 /g to 250 m.sup.2 /g. In yet another embodiment,
the active metal oxide(s) has a BET surface area greater than 25
m.sup.2 /g, such as from 25 m.sup.2 /g to about 200 m.sup.2 /g.
In a preferred embodiment, the active metal oxide(s) includes a
zirconium oxide having a BET surface area greater than 20 m.sup.2
/g, such as greater than 25 m.sup.2 /g and particularly greater
than 30 m.sup.2 /g
The active metal oxide(s) used herein can be prepared using a variety
of methods. It is preferable that the active metal oxide is made
from an active metal oxide precursor, such as a metal salt, such
as a halide, nitrate sulfate or acetate. Other suitable sources
of the metal oxide include compounds that form the metal oxide during
calcination, such as oxychlorides and nitrates. Alkoxides are also
suitable sources of the Group 4 metal oxide, for example zirconium
n-propoxide. A preferred source of the Group 4 metal oxide is hydrated
zirconia. The expression, hydrated zirconia, is intended to connote
a material comprising zirconium atoms covalently linked to other
zirconium atoms via bridging oxygen atoms, and further comprising
available hydroxyl groups.
In one embodiment, the hydrated zirconia 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 hydrated
Group 4 metal oxide in a liquid medium, for example, by the action
of refluxing liquid and/or stirring, promotes the effective interaction
of the hydrated oxide with the liquid medium. The duration of the
contact of the hydrated oxide with the liquid medium is conveniently
at least 1 hour, such as at least 8 hours. The liquid medium for
this treatment typically has a pH of about 6 or greater, such as
8 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 another embodiment, the active metal oxide is prepared, for
example, by subjecting a liquid solution, such as an aqueous solution,
comprising a source of ions of a Group 4 metal to conditions sufficient
to cause precipitation of a hydrated precursor of the solid oxide
material, such as by the addition of a precipitating reagent to
the solution. Conveniently, the precipitation is conducted at a
pH above 7. For example, the precipitating agent may be a base such
as sodium hydroxide or ammonium hydroxide.
When a mixture of a Group 4 metal oxide with a Group 2 and/or 3
metal oxide is to be prepared, a first liquid solution comprising
a source of ions of a Group 4 metal can be combined with a second
liquid solution comprising a source of ions of a Group 2 and/or
Group 3 metal. This combination of two solutions can take place
under conditions sufficient to cause co-precipitation of the mixed
oxide material as a solid from the liquid medium. Alternatively,
the source of ions of the Group 4 metal and the source of ions of
the Group 2 and/or Group 3 metal may be combined into a single solution.
This solution may then be subjected to conditions sufficient to
cause co-precipitation of a hydrated precursor of the solid mixed
oxide material, such as by the addition of a precipitating reagent
to the solution.
The temperature at which the liquid medium is maintained during
the precipitation is generally less than about 200.degree. C., such
as in the range of from about 0.degree. C. to about 200.degree.
C. 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 vessel at atmospheric pressure.
The gel, in one embodiment, is hydrothermally treated for up to
10 days, such as up to 5 days, for example up to 3 days.
The hydrated precursor to the metal oxide(s) is then recovered,
for example by filtration or centrifugation, and washed and dried.
The resulting material can then be calcined, such as in an oxidizing
atmosphere, at a temperature of at least 400.degree. C., such as
at least 500.degree. C., for example from about 600.degree. C. to
about 900.degree. C., and particularly from about 650.degree. C.
to about 800.degree. C., to form the active metal oxide or active
mixed metal oxide. The calcination time is typically up to 48 hours,
such as for about 0.5 to 24 hours, for example for about 1.0 to
10 hours. In one embodiment, calcination is carried out at about
700.degree. C. for about 1 to about 3 hours.
In another embodiment, the Group 4 metal oxide and the Group 2
and/or Group 3 metal oxide are made separately and then contacted
together to form the mixed metal oxide that is then contacted with
the molecular sieve. For example, the Group 4 metal oxide can be
contacted with the molecular sieve prior to introducing the Group
2 and/or Group 3 metal oxide or alternatively, the Group 2 and/or
Group 3 metal oxide can be contacted with the molecular sieve prior
to introducing the Group 4 metal oxide.
Where the catalyst composition comprises a Group 4 metal oxide
and a Group 3 metal oxide, the mole ratio of the Group 4 metal oxide
to the Group 3 metal oxide may be in the range of from 1000:1 to
1:1 such as from about 500:1 to 2:1 such as from about 100:1 to
about 3:1 such as from about 75:1 to about 5:1 based on the total
moles of the Group 4 and Group 3 metal oxides. In addition, the
catalyst composition can contain from 1 to 25%, such as from 1 to
20%, such as from 1 to 15%, by weight of Group 3 metal based on
the total weight of the mixed metal oxide, particularly where the
Group 3 metal oxide is a lanthanum or yttrium metal oxide and the
Group 4 metal oxide is a zirconium metal oxide.
Where the catalyst composition comprises a Group 4 metal oxide
and a Group 2 metal oxide, the mole ratio of the Group 4 metal oxide
to the Group 2 metal oxide may be in the range of from 1000:1 to
1:2 such as from about 500:1 to 2:3 such as from about 100:1 to
about 1:1 such as from about 50:1 to about 2:1 based on the total
moles of the Group 4 and Group 2 metal oxides. In addition, the
catalyst composition can contain from 1 to 25%, such as from 1 to
20%, such as from 1 to 15%, by weight of Group 2 metal based on
the total weight of the mixed metal oxide, particularly where the
Group 2 metal oxide is calcium oxide and the Group 4 metal oxide
is a zirconium metal oxide.
Catalyst Composition
The catalyst composition of the invention includes any one of the
molecular sieves previously described and one or more of the active
metal oxides described above, optionally with a binder and/or matrix
material different from the active metal oxide(s). Typically, the
weight ratio of the molecular sieve to the active metal oxide(s)
in the catalyst composition is in the range of from 5 weight percent
to 800 weight percent, such as from 10 weight percent to 600 weight
percent, particularly from 20 weight percent to 500 weight percent,
and more particularly from 30 weight percent to 400 weight percent.
There are many different binders that are useful in forming catalyst
compositions. Non-limiting examples of binders that are useful alone
or in combination include various types of hydrated alumina, silicas,
and/or other inorganic oxide sols. One preferred alumina containing
sol is aluminum chlorhydrol. 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 binder component. For example,
an alumina sol will convert to an aluminum oxide binder following
heat treatment.
Aluminum chlorhydrol, 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.cndot.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.cndot.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 binder is an alumina sol, predominantly
comprising aluminum oxide, optionally including some silicon. In
yet another embodiment, the binder is peptized alumina made by treating
an alumina hydrate, such as pseudobohemite, with an acid, preferably
an acid that does not contain a halogen, to prepare a sol or aluminum
ion solution. Non-limiting examples of commercially available colloidal
alumina sols include Nalco 8676 available from Nalco Chemical Co.,
Naperville, Ill., and Nyacol AL20DW available from Nyacol Nano Technologies,
Inc., Ashland, Mass.
Where the catalyst composition contains a matrix material, this
is preferably different from the active metal oxide and any binder.
Matrix materials are typically effective in reducing overall catalyst
cost, acting as thermal sinks to assist 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 non-active
metal oxides including 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 subbentonites 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. The matrix material, such
as a clay, may be subjected to well known modification processes
such as calcination and/or acid treatment and/or chemical treatment.
In a preferred embodiment, the matrix material is a clay or a clay-type
composition, particularly a 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 solids
content slurry, to have a low fresh surface area, and to pack together
easily due to its platelet structure. A preferred average particle
size of the matrix material, most preferably kaolin, is from about
0.1 .mu.m to about 0.6 .mu.m with a D.sub.90 particle size distribution
of less than about 1 .mu.m.
Where the catalyst composition contains a binder or matrix material,
the catalyst composition typically contains from about 1% to about
80%, such as from about 5% to about 60%, and particularly from about
5% to about 50%, by weight of the molecular sieve based on the total
weight of the catalyst composition.
Where the catalyst composition contains a binder and a matrix material,
the weight ratio of the binder to the matrix material is typically
from 1:15 to 1:5 such as from 1:10 to 1:4 and particularly from
1:6 to 1:5. The amount of binder is typically from about 2% by weight
to about 30% by weight, such as from about 5% by weight to about
20% by weight, and particularly from about 7% by weight to about
15% by weight, based on the total weight of the binder, the molecular
sieve and matrix material. It has been found that a higher sieve
content and lower matrix content increases the molecular sieve catalyst
composition performance, whereas a lower sieve content and higher
matrix content improves the attrition resistance of the composition.
The catalyst composition typically has a density in the range of
from 0.5 g/cc to 5 g/cc, such as from 0.6 g/cc to 5 g/cc, for example
from 0.7 g/cc to 4 g/cc, particularly in the range of from 0.8 g/cc
to 3 g/cc.
Method of Making the Catalyst Composition
In making the catalyst composition, the molecular sieve is first
formed and is then physically mixed with the active metal oxide,
preferably in a substantially dry, dried, or calcined state. Most
preferably the molecular sieve and active metal oxides are physically
mixed in their calcined state. Without being bound by any particular
theory, it is believed that intimate mixing of the molecular sieve
and one or more active metal oxides improves conversion processes
using the molecular sieve composition and catalyst composition of
the invention. Intimate mixing can 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. Chemical reaction between the molecular
sieve and the metal oxide(s) is unnecessary and, in general, is
not preferred.
Where the catalyst composition contains a matrix and/or binder,
the molecular sieve is conveniently initially formulated into a
catalyst precursor with the matrix and/or binder and the active
metal oxide is then combined with the formulated precursor. The
active metal oxide can be added as unsupported particles or can
be added in combination with a support, such as a binder or matrix
material. The resultant catalyst composition can then be formed
into useful shaped and sized particles by well-known techniques
such as spray drying, pelletizing, extrusion, and the like.
In one embodiment, the molecular sieve composition and the matrix
material, optionally with a binder, are combined with a liquid to
form a slurry and then mixed, preferably rigorously mixed, 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, can be combined in the same or different liquids, and can
be 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, such as from about 50
.mu.m to about 250 .mu.m, for example from about 50 .mu.m to about
200 .mu.m, and conveniently from about 65 .mu.m to about 90 .mu.m.
Other methods for forming a molecular sieve catalyst composition
are 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.
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. Typical calcination temperatures
are in the range from about 400.degree. C. to about 1000.degree.
C., such as from about 500.degree. C. to about 800.degree. C., such
as from about 550.degree. C. to about 700.degree. C. Typical calcination
environments are air (which may include a small amount of water
vapor), nitrogen, helium, flue gas (combustion product lean in oxygen),
or any combination thereof.
In a preferred embodiment, the 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, such as from 1 hour to about 10 hours,
for example from about 1 hour to about 5 hours, and particularly
from about 2 hours to about 4 hours.
Process for Using the Molecular Sieve Catalyst Compositions
The 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 cumene 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 include processes for converting naphtha to
highly aromatic mixtures; converting light olefin(s) to gasoline,
distillates and lubricants; converting oxygenates to olefin(s);
converting light paraffins to olefins and/or aromatics; and converting
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 to one or more olefin(s). Typically,
the feedstock contains one or more aliphatic-containing compounds
such that the aliphatic moiety contains from 1 to about 50 carbon
atoms, such as from 1 to 20 carbon atoms, for example from 1 to
10 carbon atoms, and particularly 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, alkylamines such as methylamine, 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) 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 are ethylene and/or propylene.
The catalyst composition of the invention is particularly useful
in the process that is generally referred to as the gas-to-olefins
(GTO) process or alternatively, the methanol-to-olefins (MTO) process.
In this process, an oxygenated feedstock, most preferably a methanol-containing
feedstock, is converted in the presence of a molecular sieve catalyst
composition into one or more olefin(s), preferably and predominantly,
ethylene and/or propylene.
Using the catalyst composition of the invention for the 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, typically greater than
60 weight percent, such as greater than 70 weight percent, and preferably
greater than 80 weight percent. Moreover, the amount of ethylene
and/or propylene produced based on the total weight of hydrocarbon
product produced is greater than 40 weight percent, typically greater
than 50 weight percent, for example greater than 65 weight percent,
and preferably greater than 78 weight percent. Typically, the amount
ethylene produced in weight percent based on the total weight of
hydrocarbon product produced, is greater than 20 weight percent,
such as greater than 30 weight percent, for example greater than
40 weight percent. In addition, the amount of propylene produced
in weight percent based on the total weight of hydrocarbon product
produced is typically greater than 20 weight percent, such as greater
than 25 weight percent, for example greater than 30 weight percent,
and preferably greater than 35 weight percent.
Using the catalyst composition of the invention for the conversion
of a feedstock comprising methanol and dimethylether to ethylene
and propylene, it is found that the production of ethane and propane
is reduced by greater than 10%, such as greater than 20%, for example
greater than 30%, and particularly in the range of from about 30%
to 40% compared to a similar catalyst composition at the same conversion
conditions but without the active metal oxide component(s).
In addition to the oxygenate component, such as methanol, the feedstock
may contains one or more diluent(s), which are generally non-reactive
to the feedstock or molecular sieve catalyst composition and are
typically used to reduce the concentration of the feedstock. 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, for example water, may be used either in a liquid
or a vapor form, or a combination thereof. The diluent may be either
added directly to the feedstock entering a reactor or added directly
to the reactor, or added with the molecular sieve catalyst composition.
The present process can be conducted over a wide range of temperatures,
such as in the range of from about 200.degree. C. to about 1000.degree.
C., for example from about 250.degree. C. to about 800.degree. C.,
including from about 250.degree. C. to about 750.degree. C., conveniently
from about 300.degree. C. to about 650.degree. C., typically from
about 350.degree. C. to about 600.degree. C. and particularly from
about 350.degree. C. to about 550.degree. C.
Similarly, the present process can be conducted over a wide range
of pressures including autogenous pressure. Typically the partial
pressure of the feedstock exclusive of any diluent therein employed
in the process is in the range of from about 0.1 kPaa to about 5
MPaa, such as from about 5 kPaa to about 1 MPaa, and conveniently
from about 20 kPaa to about 500 kPaa.
The weight hourly space velocity (WHSV), defined as the total weight
of feedstock excluding any diluents per hour per weight of molecular
sieve in the catalyst composition, typically ranges from about 1
hr-1 to about 5000 hr-1 such as from about 2 hr-1 to about 3000
hr-1 for example from about 5 hr-1 to about 1500 hr-1 and conveniently
from about 10 hr-1 to about 1000 hr-1. In one embodiment, the WHSV
is greater than 20 hr-1 and, where feedstock contains methanol and/or
dimethyl ether, is in the range of from about 20 hr-1 to about 300
hr-1.
Where the process is conducted in a fluidized bed, the superficial
gas velocity (SGV) of the feedstock including diluent and reaction
products within the reactor system, and particularly within a riser
reactor(s), is at least 0.1 meter per second (m/sec), such as greater
than 0.5 m/sec, such as greater than 1 m/sec, for example greater
than 2 m/sec, conveniently greater than 3 m/sec, and typically 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 process of the invention is conveniently conducted as a fixed
bed process, or more typically as a fluidized bed process (including
a turbulent bed process), such as a continuous fluidized bed process,
and particularly a continuous high velocity fluidized bed process.
The process 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 types 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 one practical embodiment, the process is conducted as a fluidized
bed process or high velocity fluidized bed process utilizing a reactor
system, a regeneration system and a recovery system.
In such a process the reactor system would conveniently include
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, typically comprising one or more cyclones.
In one embodiment, the one or more riser reactor(s) and disengaging
vessel are 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) into
which a molecular sieve catalyst composition or coked version thereof
is introduced. In one embodiment, prior to being introduced to the
riser reactor(s), the molecular sieve catalyst composition or coked
version thereof is contacted with a liquid, preferably water or
methanol, and/or a gas, for example, an inert gas such as nitrogen.
In an embodiment, the amount of fresh feedstock fed as a liquid
and/or a vapor to the reactor system is in the range of from 0.1
weight percent to about 85 weight percent, such as from about 1
weight percent to about 75 weight percent, more typically 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 may be the same composition, or may contain
varying proportions of the same or different feedstocks with the
same or different diluents.
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 the coked catalyst
composition. In the preferred embodiment, cyclone(s) are provided
within the disengaging vessel to separate the coked catalyst composition
from the gaseous effluent containing one or more olefin(s) within
the disengaging vessel. Although cyclones are preferred, gravity
effects within the disengaging vessel can also be used to separate
the catalyst composition from the gaseous effluent. Other methods
for separating the catalyst composition from the gaseous effluent
include the use of plates, caps, elbows, and the like.
In one embodiment, the disengaging vessel includes a stripping
zone, typically in a lower portion of the disengaging vessel. In
the stripping zone the coked 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
catalyst composition that is then introduced to the regeneration
system.
The coked 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 conventional regeneration conditions of temperature,
pressure and residence time.
Non-limiting examples of suitable regeneration media include one
or more of oxygen, O3 SO3 N2O, NO, NO2 N2O5 air, air diluted
with nitrogen or carbon dioxide, oxygen and water (U.S. Pat. No.
6245703), carbon monoxide and/or hydrogen. Suitable 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. For example, the regeneration
temperature may be in the range of from about 200.degree. C. to
about 1500.degree. C., such as from about 300.degree. C. to about
1000.degree. C., for example from about 450.degree. C. to about
750.degree. C., and conveniently from about 550.degree. C. to 700.degree.
C. The regeneration pressure may be in the range of from about 15
psia (103 kPaa) to about 500 psia (3448 kPaa), such as from about
20 psia (138 kPaa) to about 250 psia (1724 kPaa), including from
about 25 psia (172kPaa) to about 150 psia (1034 kPaa), and conveniently
from about 30 psia (207 kPaa) to about 60 psia (414 kPaa).
The residence time of the catalyst composition in the regenerator
may be in the range of from about one minute to several hours, such
as from about one minute to 100 minutes, and the volume of oxygen
in the regeneration gas may be in the range of from about 0.01 mole
percent to about 5 mole percent based on the total volume of the
gas.
The burning of coke in the regeneration step 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 catalyst
composition from the regeneration system and passing it through
a catalyst cooler to form a cooled regenerated 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 disclosed
in U.S. Pat. No. 6290916 (controlling moisture), which is herein
fully incorporated by reference.
The regenerated catalyst composition withdrawn from the regeneration
system, preferably from a 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 one embodiment,
the regenerated catalyst composition withdrawn from the regeneration
system is returned to the riser reactor(s) directly, preferably
after passing through a catalyst cooler. A carrier, such as an inert
gas, feedstock vapor, steam or the like, may be used, semi-continuously
or continuously, to facilitate the introduction of the regenerated
catalyst composition to the reactor system, preferably to the one
or more riser reactor(s).
By controlling the flow of the regenerated catalyst composition
or cooled regenerated 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 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 catalyst composition are measured by withdrawing
the catalyst composition from the conversion process and determining
its carbon content. Typical levels of coke on the molecular sieve
catalyst composition, after regeneration, are in the range of from
0.01 weight percent to about 15 weight percent, such as from about
0.1 weight percent to about 10 weight percent, for example from
about 0.2 weight percent to about 5 weight percent, and conveniently
from about 0.3 weight percent to about 2 weight percent based on
the weight of the molecular sieve.
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 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 de-ethanizer, 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 predominantly olefin(s),
preferably 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.
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 are
herein 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.
Typically, in converting one or more oxygenates to olefin(s) having
2 or 3 carbon atoms, a minor amount hydrocarbons, particularly olefin(s),
having 4 or more carbon atoms is also produced. The amount of C4+
hydrocarbons is normally less than 20 weight percent, such as less
than 10 weight percent, for example less than 5 weight percent,
and particularly less than 2 weight percent, based on the total
weight of the effluent gas withdrawn from the process, excluding
water. Typically, therefore the recovery system may include one
or more reaction systems for converting the C4+ impurities to useful
products.
Non-limiting examples of such reaction systems are described in
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 are high purity prime olefin(s) products that contain
a single carbon number olefin in an amount greater than 80 percent,
such as greater than 90 weight percent, such as greater than 95
weight percent, for example at least about 99 weight percent, based
on the total weight of the olefin.
In one practical embodiment, the process of the invention forms
part of an integrated process for producing light olefin(s) from
a hydrocarbon feedstock, preferably a gaseous hydrocarbon feedstock,
particularly 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, typically comprising carbon dioxide, carbon
monoxide and hydrogen. 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.
The next step in the process involves contacting the synthesis
gas stream generally with a heterogeneous catalyst, typically a
copper based catalyst, to produce an oxygenate containing stream,
often in combination with water. In one embodiment, the contacting
step is conducted at temperature in the range of from about 150.degree.
C. to about 450.degree. C. and a pressure in the range of from about
5 MPa to about 10 MPa.
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, can then be used as
a feedstock in a process to produce light olefin(s), such as ethylene
and/or propylene. Non-limiting examples of this integrated process
are described in EP-B-0 933 345 which is herein fully incorporated
by reference.
In another more fully integrated process, that optionally is combined
with the integrated processes described above, the 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 the Ziegler-Natta, Phillips-type, metallocene, metallocene-type
and advanced polymerization catalysts, and mixtures thereof.
In a preferred embodiment, the integrated process comprises a process
for polymerizing 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) have been made
by converting an alcohol, particularly methanol, using a molecular
sieve catalyst composition as described above. 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.
In the Examples, LEI is defined as the ratio of the lifetime of
a molecular sieve catalyst composition containing an active metal
oxide(s) compared to that of the same molecular sieve in the absence
of a metal oxide, defined as having an LEI of 1. For the purpose
of determining LEI, lifetime is defined as the cumulative amount
of oxygenate converted, preferably into one or more olefin(s), per
gram of molecular sieve, until the conversion rate drops to about
10% of its initial value. If the conversion has not fallen to 10%
of its initial value 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-1.
"Prime Olefin" is the sum of the selectivity to ethylene
and propylene. The ratio "C2=/C3=" is the ratio of the
ethylene to propylene selectivity weighted over the run. The "C3
Purity" is calculated by dividing the propylene selectivity
by the sum of the propylene and propane selectivities. The selectivities
for methane, ethylene, ethane, propylene, propane, C4's and C5+'s
are average selectivities weighted over the run. Note that the C5+'s
consist only of C5's, C6's and C7's. 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 Molecular Sieve
A silicoaluminophosphate molecular sieve, SAPO-34 designated as
MSA, was crystallized in the presence of tetraethyl ammonium hydroxide
(R1) and dipropylamine (R2) as the organic structure directing agents
or templating agents. A mixture of the following mole ratio composition:
was prepared by initially mixing an amount of Condea Pural SB 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. The molecular sieve crystals were then mixed with a
binder and matrix material and formed into particles by spray drying.
Example B
Conversion Process
All catalytic or conversion data presented was obtained using a
microflow reactor consisting of a stainless steel reactor (1/4 inch
(0.64 cm) outer diameter) located in a furnace to which vaporized
methanol was fed. The reactor was maintained at a temperature of
475.degree. C. and a pressure of 25 psig (172.4 kPag) The flow rate
of the methanol was 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-1. Product gases exiting the reactor
were collected and analyzed using gas chromatography. The catalyst
load in each experiment 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, a physical mixture
of the MSA molecular sieve of Example A and the active metal oxide(s)
was used. The total catalyst composition load remained 50 mg, and
the methanol flow rate was adjusted as the amount of molecular sieve
in the reactor bed was reduced by the addition of the mixed metal
oxide such that the methanol WHSV was 100 h-1 based on the amount
of molecular sieve in the reactor bed.
Example 1
One thousand grams of ZrOCl2.8H2O was dissolved with stirring in
3.0 liters of distilled water. Another solution containing 400 grams
of concentrated NH4OH and 3.0 liters of distilled water was prepared.
Both solutions were heated to 60.degree. C. These two heated solutions
were combined at a rate of 50ml/min using nozzle mixing. The pH
of the final composite was adjusted to approximately 9 by the addition
of concentrated ammonium hydroxide. This slurry was then put in
polypropylene bottles and placed in a steambox (100.degree. C.)
for 72 hours. The product formed was recovered by filtration, washed
with excess water, and dried overnight at 85.degree. C. A portion
of this product was calcined to 700.degree. C. in flowing air for
3 hours to produce an active zirconium oxide material.
Example 2
Five hundred grams of ZrOCl2.8H2O and 84 grams of La(NO3)3.6H2O
were dissolved with stirring in 3.0 liters of distilled water. Another
solution containing 260 grams of concentrated NH4OH and 3.0 liters
of distilled water was prepared. Both solutions were heated to 60.degree.
C. and then combined at the rate of 50 ml/min using nozzle mixing
to form the final mixture, a slurry. The pH of the final mixture
was adjusted to approximately 9 by the addition of concentrated
ammonium hydroxide. This slurry was then put in a polypropylene
bottle and placed in a steam box (100.degree. C.) for 72 hours.
The resulting product formed was recovered by filtration, washed
with excess water, and dried overnight at 85.degree. C. A portion
of this product, was calcined to 700.degree. C. in flowing air for
3 hours to produce an active mixed metal oxide containing a nominal
10 weight percent La (lanthanum) based on the final weight of the
mixed metal oxide.
Example 3
Fifty grams of ZrOCl2.8H2O were dissolved with stirring in 300
ml of distilled water. Another solution containing 4.2 grams of
La(NO3)3.6H2O and 300 ml of distill water was prepared. These two
solutions were combined with stirring to form a final mixture. The
pH of the final mixture, a slurry, was adjusted to approximately
9 by the addition of concentrated ammonium hydroxide (28.9 grams).
This slurry was then put in a polypropylene bottle and placed in
a steam box (100.degree. C.) for 72 hours. The resulting product
formed was recovered by filtration, washed with excess water, and
dried overnight at 85.degree. C. A portion of this resulting product
was calcined to 700.degree. C. in flowing air for 3 hours to produce
an active mixed metal oxide containing a nominal 5 weight percent
La based on the final weight of the mixed metal oxide.
Example 4
Five hundred grams of ZrOCl2.8H2O and 70 grams of Y(NO3)3.5H2O
were dissolved with stirring in 3.0 liters of distilled water. Another
solution containing 260 grams of concentrated NH4OH and 3.0 liters
of distilled water was prepared. Both solutions were heated to 60.degree.
C. and then combined at the rate of 50 ml/min using nozzle mixing
to form a final mixture. The pH of the final mixture, a slurry,
was adjusted to approximately 9 by the addition of concentrated
ammonium hydroxide. This slurry was then put in a polypropylene
bottle and placed in a steam box (100.degree. C.) for 72 hours.
The resulting product formed was recovered by filtration, washed
with excess water, and dried overnight at 85.degree. C. A portion
of the resulting product was calcined to 700.degree. C. in flowing
air for 3 hours to produce an active mixed metal oxide containing
a nominal 10 weight percent Y (yttrium) based on the final weight
of the mixed metal oxide.
Example 5
Five hundred grams of ZrOCl2.8H2O and 56 grams of Ca(NO3)2.4H2O
were dissolved with stirring in 3000 ml of distilled water. Another
solution containing 260 grams of NH4OH and 3000 ml of distilled
water was prepared. These two solutions were combined with stirring.
The pH of the final composite was adjusted to approximately 9 by
the addition of concentrated ammonium hydroxide (160 grams). This
slurry was then put in polypropylene bottles and placed in a steambox
(100.degree. C.) for 72 hours. The resulting product formed was
recovered by filtration, washed with excess water, and dried overnight
at 85.degree. C. A portion of this product was calcined to 700.degree.
C. in flowing air for 3 hours to produce an active mixed metal oxide
containing a nominal 5 weight percent Ca (calcium) based on the
final weight of the mixed metal oxide.
Example 6
Seventy grams of TiOSO.sub.4.multidot.xH.sub.2 SO.sub.4.multidot.xH.sub.2
O (x=1) were dissolved with stirring in 400 ml of distilled water.
Another solution containing 12.8 grams of CeSO.sub.4 and 300 ml
of distilled water was prepared. These two solutions were combined
with stirring. The pH of the final composite was adjusted to approximately
8 by the addition of concentrated ammonium hydroxide (64.3 grams).
This slurry was then put in polypropylene bottles and placed in
a steambox (100.degree. C.) for 72 hours. The product formed was
recovered by filtration, washed with excess water, and dried overnight
at 85.degree. C. A portion of this product was calcined to 700.degree.
C. in flowing air for 3 hours to produce an active mixed metal oxide
containing a nominal 5 weight percent Ce based on the final weight
of the mixed metal oxide.
Example 7
Five grams of HfOCl.sub.2.multidot.xH.sub.2 O was dissolved with
stirring in 100 ml of distilled water. The pH of the final composite
was adjusted to approximately 9 by the addition of concentrated
ammonium hydroxide (4.5 grams). This slurry was then put in a polypropylene
bottle and placed in a steambox (100.degree. C.) for 72 hours. The
product formed was recovered by filtration, washed with excess water,
and dried overnight at 85.degree. C. A portion of this catalyst
was calcined to 700.degree. C. in flowing air for 3 hours to produce
an active hafnium oxide.
Example 8
Five grams of HfOCl.sub.2.multidot.xH.sub.2 O and 0.62 grams of
La(NO.sub.3).sub.3.multidot.6H.sub.2 O were dissolved with stirring
in 100 ml of distilled water. The pH of the final composite was
adjusted to approximately 9 by the addition of concentrated ammonium
hydroxide (3.5 grams). This slurry was then put in a polypropylene
bottle and placed in a steambox (100.degree. C.) for 72 hours. The
product formed was recovered by filtration, washed with excess water,
and dried overnight at 85.degree. C. A portion of this catalyst
was calcined to 700.degree. C. in flowing air for 3 hours to produce
an active mixed metal oxide containing a nominal 5 weight % La based
on the final weight of the mixed metal oxide.
Example 9
The carbon dioxide uptake of the oxides of Examples 1 through 8
were measured using a Mettler TGA/SDTA 851 thermogravimetric analysis
system under ambient pressure. The metal oxide samples were first
dehydrated in flowing air to about 500.degree. C. for one hour after
which the uptake of carbon dioxide was measured at 100.degree. C.
The surface area of the samples were measured in accordance with
the method of Brunauer, Emmett, and Teller (BET) to provide the
carbon dioxide uptake in terms of mg carbon dioxide/m.sup.2 of the
metal oxide presented in Table 1.
TABLE 1 Catalyst Dry Surface Area CO.sub.2 Uptake Example Weight
(mg) mg of CO.sub.2 (m.sup.2 /g) (mg of CO.sub.2 /m.sup.2) 1 76
0.0980 29 0.045 2 115 0.7781 80 0.085 3 73 0.4243 89 0.065 4 97
0.3808 100 0.039 5 78 0.5399 85 0.081 6 43 0.1035 50 0.048 7 158
0.3704 25 0.094 8 164 0.7359 60 0.075
Example 10 (Comparative)
The performance of the control, the molecular sieve of Example
A, MSA, using a 50 mg load in the reactor and under the conditions
discussed above in Example B is reported in Tables 2 and 3.
Example 11
In this Example, the catalyst composition consisted of 40 mg MSA
of Example A and 10 mg of the active zirconium oxide of Example
1. The catalyst composition and active mixed metal oxide were well
mixed, and then diluted with quartz to form the reactor bed. The
results of testing this catalyst composition in the process of Example
B are shown in Tables 2 and 3. The results indicate that the addition
of the active zirconium oxide to the catalyst bed increased the
lifetime of the molecular sieve composition significantly, and decreased
the amounts of undesired ethane and propane.
Example 12
In this Example, the catalyst composition consisted of 40 mg MSA
of Example A and 10 mg of the active mixed metal oxide containing
10 weight percent La, described in Example 2. The catalyst composition
and active mixed metal oxide were well mixed, and then diluted with
quartz to form the reactor bed. The results of testing this catalyst
composition in the process of Example B are shown in Tables 2 and
3. The data in Tables 2 and 3 illustrate that by constituting 20%
of the catalyst composition load with the active mixed metal oxide
containing 10 weight percent La, the lifetime of the molecular sieve
doubled, as indicated by its LEI value of 2. In addition, there
was a net gain of 1.7% in prime olefins on an absolute basis, with
most of this gain being due to an increase in propylene of 2.76%,
offsetting a small decrease in ethylene of 1.07%. Selectivity to
ethane decreased by 39% and selectivity to propane decreased by
37% suggesting that hydrogen transf |