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 a molecular sieve,
such as a silicoaluminophosphate and/or an aluminophosphate, hydrotalcite,
and optionally a rare earth metal component
Molecular sieve claims
What is claimed is:
1. A catalyst composition comprising a molecular sieve selected
from silicoaluminophosphates, aluminophosphates, metal-containing
forms thereof and mixtures, including intergrowths, thereof, hydrotalcite,
and a rare earth metal component.
2. The catalyst composition of claim 1 wherein the molecular sieve
is selected from silicoaluminophosphates, metal-containing forms
thereof and mixtures, including intergrowths, thereof.
3. The catalyst composition of claim 1 wherein the molecular sieve
is selected from 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 SAPO-47 SAPO-56 AlPO-5 AlPO-11 AlPO-18 AlPO-31
AlPO-34 AlPO-36 AlPO-37 AlPO-46 MCM-2 metal-containing forms
thereof, and mixtures, including intergrowths, thereof.
4. The catalyst composition of claim 1 wherein the molecular sieve
is selected from SAPO-18 SAPO-34 SAPO-35 SAPO-44 SAPO-47 ALPO-34
metal-containing forms thereof, and mixtures, including intergrowths,
thereof.
5. The catalyst composition of claim 1 wherein the molecular sieve
is SAPO-34 SAPO-18 an intergrowth of SAPO-34 and SAPO-18 GeAPO-34
GeAPO-18 or an intergrowth of GeAPO-34 and GeAPO-18.
6. The catalyst composition of claim 1 wherein the rare earth
metal is lanthanum.
7. The catalyst composition of claim 1 wherein the composition
comprises from 10 to 90 wt % of the molecular sieve, from 10 to
90 wt % of the hydrotalcite, and from 0.1 to 5 wt % of the rare
earth metal component, wherein the weight percents are based on
the total weight of the molecular sieve, the hydrotalcite, and the
rare earth metal component.
8. A catalyst composition comprising: (a) an aluminophosphate or
silicoaluminophosphate molecular sieve selected from 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 SAPO-47 SAPO-56
AlPO-5 AlPO-11 AlPO-18 AlPO-31 AlPO-34 AlPO-36 AlPO-37 AlPO-46
MCM-2 metal-containing forms thereof, and mixtures, including intergrowths,
thereof; and (b) hydrotalcite.
9. The catalyst composition of claim 8 wherein the molecular sieve
is selected from SAPO-18 SAPO-34 SAPO-35 SAPO-44 SAPO-47 ALPO-34
metal-containing forms thereof, and mixtures, including intergrowths,
thereof.
10. The catalyst composition of claim 8 wherein the molecular
sieve is SAPO-34 SAPO-18 an intergrowth of SAPO-34 and SAPO-18
GeAPO-34 GeAPO-18 or an intergrowth of GeAPO-34 and GeAPO-18.
11. The catalyst composition of claim 8 comprising the molecular
sieve in an amount of from 10 to 90 wt %, and the hydrotalcite in
an amount of from 10 to 90 wt %, wherein the weight percents are
based on the total weight of the molecular sieve and the hydrotalcite.
12. The catalyst composition of claim 8 further comprising a rare
earth metal component.
13. The catalyst composition of claim 12 comprising the molecular
sieve in an amount of from 10 to 90 wt %, the hydrotalcite in an
amount of from 10 to 90 wt %, and the rare earth metal component
in an amount of from 0.1 to 5 wt %, wherein the weight percents
are based on the total weight of the molecular sieve, the hydrotalcite
and the rare earth metal component.
14. The catalyst composition of claim 12 wherein the rare metal
component is lanthanum.
15. A process for producing a molecular sieve catalyst composition,
the process comprising: (a) providing a molecular sieve selected
from silicoaluminophosphates, aluminophosphates, metal-containing
forms thereof and mixtures, including intergrowths, thereof; (b)
providing a hydrotalcite composition comprising hydrotalcite and
a rare earth metal component; and (c) combining the molecular sieve
and the hydrotalcite composition to produce a molecular sieve catalyst
composition.
16. The process of claim 15 wherein the molecular sieve is selected
from silicoaluminophosphates, metal-containing forms thereof and
mixtures, including intergrowths, thereof.
17. The process of claim 15 wherein the molecular sieve is selected
from 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 SAP-47 SAPO-56 AlPO-5 AlPO-11 AlPO-18 AlPO-31 AlPO-34
AlPO-36 AlPO-37 AlPO-46 MCM-2 metal-containing forms thereof,
and mixtures, including intergrowths, thereof.
18. The process of claim 15 wherein the molecular sieve is selected
from SAPO-18 SAPO-34 SAPO-35 SAPO-44 SAPO-47 ALPO-34 metal-containing
forms thereof, and mixtures, including intergrowths, thereof.
19. The process of claim 15 wherein the molecular sieve is SAPO-34
an intergrowth of SAPO-34 and SAPO-18 or GeAPO-34.
20. The process of claim 15 wherein the rare earth metal component
is lanthanum.
21. The process of claim 15 wherein the molecular sieve catalyst
composition comprises from 10 to 90 wt % of the molecular sieve,
from 10 to 90 wt % of the hydrotalcite, and from 0.1 to 5 wt % of
the rare earth metal component, wherein the weight percents are
based on the total weight of the molecular sieve, the hydrotalcite,
and the rare earth metal component.
22. The process of claim 15 wherein the step of providing a hydrotalcite
composition comprises: (i) providing a solution of a rare earth
metal compound; (ii) treating hydrotalcite with said solution; and
(iii) drying the treated hydrotalcite to form a dried hydrotalcite
composition.
23. The process of claim 22 wherein the rare earth metal compound
is selected from halides, oxides, oxyhalides, hydroxides, sulfides,
sulfonates, borides, borates, carbonates, nitrates, carboxylates
and mixtures thereof.
24. The process of claim 22 wherein the solution is an aqueous
solution.
25. The process of claim 22 further comprising (iv) calcining
the dried hydrotalcite composition.
26. The process of claim 15 wherein the step of combining comprises:
(i) forming a slurry comprising the molecular sieve and the hydrotalcite
composition; and (ii) drying the slurry to form a dried, formulated
molecular sieve catalyst composition.
27. The process of claim 26 wherein the slurry comprises a liquid,
molecular sieve, hydrotalcite and a rare earth metal compound.
28. The process of claim 27 wherein the rare earth metal compound
is selected from halides, oxides, oxyhalides, hydroxides, sulfides,
sulfonates, borides, borates, carbonates, nitrates, carboxylates
and mixtures thereof.
29. The process of claim 27 wherein the rare earth metal compound
is soluble in the liquid.
30. The process of claim 27 wherein the rare earth compound and
the hydrotalcite are pre-contacted to form the hydrotalcite composition.
31. The process of claim 30 wherein the step of pre-contacting
comprises: (i) providing a solution of a rare earth metal compound;
(ii) treating hydrotalcite with said solution; and (iii) drying
the treated hydrotalcite to form a dried hydrotalcite composition.
32. The process of claim 27 wherein the liquid comprises at least
one of water, an alcohol, a ketone, an aldehyde, or an ester.
33. The process of claim 26 wherein the step of drying comprises
spray drying.
Molecular sieve description
FIELD
The present invention relates to molecular sieve catalyst compositions,
to the production of such compositions and to the use of such compositions
in conversion processes, particularly 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.
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
AlPO4.
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 [SiO4], [AlO4] 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 with a matrix material and/or a
binder, which typically are metal oxides. However, 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. 4889615 discloses a process for the catalytic cracking
of high metals content feeds, including resids, in which the feed
is cracked in the presence of a catalyst comprising a zeolite, such
as zeolite Y, and an additive comprising a dehydrated magnesium-aluminum
hydrotalcite which acts as a trap for vanadium as well as an agent
for reducing the content of sulfur oxides in the regenerator flue
gas.
U.S. Pat. No. 6010619 discloses a fluid catalytic cracking process
for converting hydrocarbon feed stocks containing heavy metal compounds,
in which the catalyst employed comprises a zeolite or silicophosphoaluminate
treated with particles of a carbonated strontium-substituted hydrotalcite.
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.
EP-A-3 12981 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 Cs2O 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.
In our co-pending U.S. patent application Ser. No. 10/364156 filed
Feb. 10 2003 there is described catalyst composition which exhibits
enhanced lifetime when used in the conversion of oxygenates to olefins
and which comprises a molecular sieve and at least one metal oxide
having an uptake of carbon dioxide at 100.degree. C. of at least
0.03 mg/m2 of the metal oxide. The metal oxide is selected from
an oxide of Group 4 of the Periodic Table of Elements, either alone
or in combination with an oxide selected from Group 2 of the Periodic
Table of Elements and/or an oxide selected from Group 3 of the Periodic
Table of Elements, including the Lanthanide series of elements and
the Actinide series of elements.
SUMMARY
In one embodiment, the invention provides a catalyst composition
including a molecular sieve, hydrotalcite, and a rare earth metal
component. In one aspect of this embodiment, the molecular sieve
is selected from an aluminophosphate, a silicoaluminophosphate and
metal-containing forms thereof. In a particular aspect of this embodiment,
the rare earth metal is lanthanum.
Conveniently, the molecular sieve is selected from SAPO-5 SAPO-8
SAPO-11 SAPO-16 SAPO-17 SAPO-18 SAPO-20 SAPO-3 1 SAPO-34
SAPO-35 SAPO-36 SAPO-37 SAPO-40 SAPO-41 SAPO-42 SAPO-44 SAPO-47
SAPO-56 AlPO-5 AlPO-11 AlPO-18 AlPO-31 AlPO-34 AlPO-36 AlPO-37
AlPO-46 MCM-2 metal-containing forms thereof and mixtures, including
intergrowths, thereof. Particularly useful molecular sieves include
SAPO-18 SAPO-34 SAPO-35 SAPO-44 SAPO-47 AlPO-34 metal-containing
forms thereof, and mixtures, including intergrowths, thereof, especially
SAPO-34 intergrowths of SAPO-34 and SAPO-1 8 and intergrowths
of GeAPO-34 and GeAPO-18.
In another embodiment, the invention provides a catalyst composition
including an aluminophosphate or silicoaluminophosphate molecular
sieve selected from 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 SAPO-47 SAPO-56 AlPO-5 AlPO-11 AlPO-18 AlPO-31
AlPO-34 AlPO-36 AlPO-37 AlPO-46 MCM-2 metal-containing forms
thereof, and mixtures, including intergrowths, thereof and hydrotalcite.
Optionally, the composition can further include a rare earth metal
component, such as lanthanum.
Conveniently, the aluminophosphate and metallcoaluminophosphate
molecular sieves are selected from AlPO-5 AlPO-11 AlPO-18 AlPO-31
AlPO-34 AlPO-36 AlPO-37 AlPO-46 metal-containing forms thereof
and mixtures, including intergrowths, thereof.
In yet another embodiment, the invention provides a process for
formulating a molecular sieve catalyst composition, the process
including providing a molecular sieve; providing a hydrotalcite
composition including hydrotalcite and rare earth metal component;
and combining the molecular sieve and the hydrotalcite composition
to produce a formulated molecular sieve catalyst composition.
Conveniently, the step of providing a hydrotalcite composition
is carried out by providing a solution of a rare earth metal compound;
mixing the solution with hydrotalcite to form a slurry; and drying
the slurry to form a dried hydrotalcite composition. By way of example,
the rare earth metal compound may be a halide, an oxide, an oxyhalide,
a hydroxide, a sulfide, a sulfonate, a boride, a borate, a carbonate,
a nitrate, a carboxylate or a mixture thereof.
Conveniently, the step of combining the molecular sieve and the
hydrotalcite composition is carried out by forming a slurry of the
molecular sieve and the hydrotalcite composition; and drying the
slurry to form a dried, formulated molecular sieve catalyst composition.
In further embodiment, the invention provides a process for converting
a hydrocarbon oxygenate feedstock to olefins, the process comprising
contacting the feedstock with a catalyst composition comprising:
(a) molecular sieve; and (b) hydrotalcite;
under catalytic conversion conditions, to form a product mixture
comprising olefins.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Introduction
The invention is directed to a molecular sieve catalyst composition,
its production and its use in the conversion of hydrocarbon feedstocks,
particularly oxygenated feedstocks, into olefin(s). It has been
found that combining a molecular sieve with hydrotalcite, optionally
together with a rare earth metal, results in a catalyst composition
with 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 than the same molecular sieve without the hydrotalcite
additive.
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, crystalline 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 [TO4] 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 one embodiment, the molecular
sieves used herein 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 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 including one, or preferably,
two or more corner-sharing [TO4] tetrahedral units, and more preferably,
two or more [SiO4], [AlO4] and/or [PO4] tetrahedral units. Typically,
the molecular sieves used herein are aluminophosphate (AlPO) molecular
sieves, silicoaluminophosphate (SAPO) molecular sieves, metal-containing
AlPO and SAPO molecular sieves and intergowths of such sieves.
In the case of metal-containing molecular sieves, the metal atoms
can be inserted into the framework of the molecular sieve through
a tetrahedral unit, such as [MeO2], 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.
Examples of suitable metals for use in the metal-containing molecular
sieves used herein are alkali metals of Group 1 of the Periodic
Table of Elements, alkaline earth metals of Group 2 of the Periodic
Table of Elements, 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, transition metals of Groups 4 to 12 of the Periodic Table
of Elements, and 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. The Periodic Table of Elements referred to herein is the
IUPAC format described in the CRC Handbook of Chemistry and Physics,
78th Edition, CRC Press, Boca Raton, Fla. (1997).
Aluminophosphate molecular sieves, silicoaluminophosphate 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 (AlPO4), 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 [QO2]), 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.
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 an element 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 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-3 1 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 MCM-2 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, such as GeAPO-34 and GeAPO-18.
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 Publication No. 2002/0165089
and International Patent Publication No. WO 98/15496 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
Publication No. 2002/0165089 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 AlPO4 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 R4N+, 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-butylamine, 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.
Hydrotalcite Additive
Naturally occurring hydrotalcite is a mineral found in relatively
small quantities in a limited number of geographical areas, principally,
in Norway and in the Ural Mountains. Natural hydrotalcite has a
variable composition depending on the location of the source. Natural
hydrotalcite is a hydrated magnesium, aluminum and carbonate-containing
composition, which has been found to have the typical composition,
represented as Mg6Al2(OH)16CO3.4H2O. Natural hydrotalcite deposits
are generally found intermeshed with spinel and other minerals,
such as penninite and muscovite, from which it is difficult to separate
the natural hydrotalcite.
Synthetically produced hydrotalcite can be made to have the same
composition as natural hydrotalcite, or, because of flexibility
in the synthesis, it can be made to have a different composition
by replacing the carbonate anion with other anions, such as phosphate
ion. In addition, the Mg/Al ratio can be varied to control the basic
properties of the hydrotalcite.
A phosphate-modified synthetic hydrotalcite and a process for its
synthesis are disclosed in U.S. Pat. No. 4883533. U.S. Pat. No.
3539306 discloses a process for preparing hydrotalcite which involves
mixing an aluminum-containing compound with a magnesium-containing
compound in an aqueous medium in the presence of carbonate ion at
a pH of at least 8. U.S. Pat. No. 4656156 discloses a process
for producing synthetic hydrotalcite by heating a magnesium compound
to a temperature of about 500 to 900.degree. C. to form activated
magnesia, adding the activated magnesia to an aqueous solution containing
aluminate, carbonate and hydroxyl ions, and then agitating the resultant
mixture at a temperature of about 80 to 100.degree. C. for 20 to
120 minutes to form a low density, high porosity hydrotalcite. A
similar process is disclosed in U.S. Pat. No. 4904457. The entire
disclosure of each of the above references is incorporated herein
by reference.
Hydrotalcite compositions containing pillaring organic, inorganic
and mixed organic/inorganic anions are disclosed in U.S. Pat. No.
4774212 the entire disclosure of which is incorporated herein
by reference. The compositions are anionic magnesium aluminum hydrotalcite
clays having large inorganic and/or organic anions located interstitially
between positively charged layers of metal hydroxides. The compositions
are of the formula:
where Y is a large organic anion selected from the group consisting
of lauryl sulfate, p-toluenesulfonate, terephthalate, 25-dihydroxy-14-benzenedisulfonate,
and 15-naphthalenedisulfonate or where Y is an anionic polyoxometalate
of vanadium, tungsten or molybdenum. In the above cases, x is from
1.5 to 2.5 n is 1 or 2 and Z is from 0 to 3 except that when Y
is polyoxometalate, n is 6.
An aggregated synthetic hydrotalcite having a substantially spheroidal
shape and an average spherical diameter of up to about 60 .mu.m,
composed of individual platy particles, is disclosed in U.S. Pat.
No. 5364828 the entire disclosure of which is incorporated herein
by reference. This form of hydrotalcite is prepared from aqueous
solutions of soluble magnesium and aluminum salts, which are mixed
in a molar ratio of from about 2.5:1 to 4:1 together with a basic
solution containing at least a two-fold excess of carbonate and
a sufficient amount of a base to maintain a pH of the reaction mixture
in the range of from about 8.5 to about 9.5.
Synthetic hydrotalcite is commercially available and can, for example,
be obtained from Sasol North America Inc. as Condea Pural MG70.
Prior to use in the catalyst composition of the invention, it may
be desirable to calcine the hydrotalcite to remove the water inherently
contained by the material. Suitable calcination conditions include
a temperature of from about 300.degree. C. to about 800.degree.
C., such as from about 400.degree. C. to about 600.degree. C. for
about 1 to about 16 hours, such as for about 3 to about 8 hours.
Rare Earth Metal Component
In addition to the hydrotalcite additive, the molecular sieve catalyst
composition of the invention can also include a rare earth metal
component. Suitable rare earth metals include yttrium and elements
of the Lanthanide or Actinide series metals, including lanthanum,
cerium, praseodymium, neodymium, samarium, europium, gadolinium,
terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium,
thorium and mixtures thereof. Typically the rare earth metal will
be selected from lanthanum, yttrium, cerium and mixtures thereof,
especially lanthanum.
The rare earth metal component can be present in the final catalyst
composition as the elemental rare earth metal or more preferably,
as an oxide of the metal.
Catalyst Composition
The catalyst composition of the invention includes any one of the
molecular sieves previously described, hydrotalcite and optionally
a rare earth metal component. Typically, the catalyst composition
contains in the range of from about 10 wt % to about 90 wt %, such
as from about 40 wt % to about 60 wt %, of the molecular sieve and
in the range of from about 10 wt % to about 90 wt %, such as from
about 40 wt % to about 60 wt %, of the hydrotalcite based on the
total weight of the molecular sieve, the hydrotalcite, and any rare
earth metal component present.
Moreover, where the catalyst composition contains a rare earth
metal component, said rare earth metal component is typically present
in the range of from about 0.1 wt % to about 5 wt %, such as from
about 1 wt % to about 3 wt %, based on the total weight of the molecular
sieve, the hydrotalcite, and rare earth metal component.
In addition, the catalysts composition can contain a binder and/or
matrix material to enhance the physical characteristics of the catalyst.
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 AlmOn(OH)oClp.x(H2O)
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 Al13O4(OH)24Cl7.12(H2O)
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.
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.
Where the catalyst composition contains a binder and/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.
Method of Making the Catalyst Composition
The catalyst composition used herein can be prepared using a variety
of methods. In general, however, making the catalyst composition
comprises initially synthesizing the molecular sieve and then combining
the molecular sieve with a hydrotalcite composition comprising the
hydrotalcite and, where desired, a rare earth metal component. Combining
the molecular sieve with a hydrotalcite composition is conveniently
achieved by forming a slurry of the molecular sieve and the hydrotalcite
composition in a liquid, mixing the slurry, for example by colloid
milling, to produce a substantially homogeneous mixture and then
drying the mixture. 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.
Where the hydrotalcite composition contains a rare earth metal
component, it is conveniently produced by dissolving a rare earth
compound in a solvent, such as water, combining the resultant solution
with the hydrotalcite either by impregnation or slurry mixing and
then drying the resultant mixture. Suitable rare earth metal compounds
include acetates, halides, oxides, oxyhalides, hydroxides, sulfides,
sulfonates, borides, borates, carbonates, nitrates, carboxylates
and mixtures thereof.
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 hydrotalcite
composition is then combined with the formulated precursor. 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, such as by colloid milling, 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.
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.
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.
Process for Using the Molecular Sieve Catalyst Compositions
The catalyst compositions described above are useful in a variety
of processes including the conversion of a feedstock containing
one of more aliphatic compounds, preferably oxygenates, to olefins
and the conversion of a feedstock including one or more oxygenates
and ammonia into alkyl amines, in particular methylamines.
The most preferred process of the invention is a process directed
to the conversion of an aliphatic feedstock to one or more olefin(s).
Typically, the feedstock contains one or more aliphatic-containing
compounds such that the aliphatic moiety contains form 1 to about
50 carbon atoms, such as form 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, fornaldehydes, 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 typically greater than 50 weight percent, for example
greater than 60 weight percent, such as greater than 70 weight percent.
Moreover, the amount of ethylene and/or propylene produced based
on the total weight of hydrocarbon product produced is typically
greater than 40 weight percent, such as greater than 50 weight percent,
for example greater than 65 weight percent. Typically, the amount
ethylene produced in weight percent based on the total weight of
hydrocarbon product produced, is typically greater than 20 weight
percent, such as greater than 30 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
30 weight percent, such as greater than 40 weight percent.
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. Nos. 4076796
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) arc 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.
Using the catalyst composition of the invention for the conversion
of a feedstock containing one or more oxygenates into olefin(s),
it is found that the life of the catalyst is improved as compared
with a similar catalyst without the hydrotalcite additive. Typically,
the improvement is such that the life of the catalyst of the invention
is at least 50%, such as at least 100%, for example at least 200%,
greater than that of the catalyst without the hydrotalcite additive.
The catalyst composition described herein can also be used in the
manufacture of alkylamines, using a feedstock including ammonia
in addition to oxygenates. Examples of suitable processes are described
in EP 0 993 867 A1 and in U.S. Pat. No. 6153798.
The invention will now be more particularly described with reference
to the Examples, in which all parts are by weight.
EXAMPLE 1
Synthesis of EMM-2
To 165.5 parts of demineralized water were added 228.4 parts of
an 85% solution of H3PO4. 103 parts of water were used to rinse
the container. To this diluted solution were added 14.9 parts of
Ludox AS40 and 2.1 parts of water were used to rinse the container.
Then 416.7 parts of a 35% solution of TEAOH (tetraethylammonium
hydroxide) were added and 24.8 parts of rinse water were used to
rinse the container. Finally 133.2 parts of Condea Pural SB were
added and mixed until a homogeneous mixture was obtained, whereafter
the container was rinsed with 4.1 parts of water.
The resultant homogeneous mixture was crystallized in a stirred
autoclave with stirring rate of 50 rpm. The autoclave was heated
in 12.5 hours to 175.degree. C. and was kept at that temperature
for 50 hours to effect the crystallization. The resultant EMM-2
crystals were recovered by washing and drying. After drying the
material overnight at 120.degree. C., 21.3 wt % (based on the initial
intake) of solids were recovered. The resultant material was then
calcined first in nitrogen at 650.degree. C. for 5 hours, followed
by air calcination for 3 hours at 650.degree. C.
EXAMPLE 2
EMM-2 with La/Hydrotalcite
0.23 gram of lanthanum acetate was dissolved in 1.9 ml of de-ionized
water and the resulting solution was added drop-wise to 2.015 gram
of hydrotalcite as supplied by Sasol North America Inc. as Condea
Pural MG70 (specific surface area of 180 m2/gram). The treated hydrotalcite
was dried at 50.degree. C. for 1 hour under vacuum and then calcined
in air at 550.degree. C. for 3 hours.
0.2 gram of the La-impregnated hydrotalcite was mixed with 0.36
gram of the calcined EMM-2 from Example 1 and the resultant catalyst
was evaluated in the conversion of methanol to olefins in a fixed
bed reactor equipped with an on-line gas chromatograph for product
analysis. The test conditions were 450.degree. C., 25 psig (273
kPaa) and 25 WHSV. The results of the test are summarized in Table
1 which also shows the results obtained with a comparative test
using 0.36 gram of EMM-2 alone under the same conditions.
TABLE 1 EMM-2 + Catalyst EMM-2 La/Hydrotalcite C.sub.2 = (wt %
of product) 35.3 32.3 C.sub.3 = (wt % of product) 41.0 43.7 C.sub.2
= +C.sub.3 = (wt % of product) 76.3 76.0 Catalyst Life 20.7 72.3
It is clear from Table 1 that the addition of the La/hydrotalcite
to the EMM-2 increased the life of the catalyst and also increased
its propylene selectivity at the expense of its ethylene selectivity.
The total ethylene plus propylene selectivity was substantially
unaffected. The catalyst life is defined as the total amount of
methanol converted in grams per gram of EMM-2.
EXAMPLE 3
Synthesis of Ge APO-34/18 Intergrowth
21.8 grams of H3PO4 (85%) were diluted with 22.1 grams of de-ionized
water and to this solution were added 3.6 grams of Ge-ethoxide.
After mixing this solution, 40.1 grams of TEAOH (35%) were added
dropwise to the solution, whereafter 12.8 grams of Condea Pural
SB were added and mixed until a homogeneous mixture was obtained.
85.8 grams of this mixture was transferred to a 150 ml stainless
steel autoclave and mounted on an axis inside a oven. The autoclave
was rotated at 60 rpm while the oven was heated in 8 hours from
room temperature to 175.degree. C. and then kept at this temperature
for 48 hours. After crystallization, the resultant GeAPO-34/18 intergrowth
product was washed and dried. 18.9 wt % of solid yield was recovered
after drying overnight at 120.degree. C. The AEI/CHA of ratio of
the recovered intergrowth material was 90:10. The final product
was calcined first in nitrogen at 650.degree. C. for 5 hours, followed
by air calcination for 3 hours at 650.degree. C.
EXAMPLE 4
Ge-APO34/18 with La/Hydrotalcite
0.61 gram of lanthanum chloride was dissolved in 4.72 ml of de-ionized
water and the resulting solution was added drop-wise to 5.00 gram
of hydrotalcite as supplied by Sasol North America Inc. as Condea
Pural MG70 (specific surface area of 180 m2/gram). The treated hydrotalcite
was dried at 50.degree. C. for 1 hour under vacuum and then calcined
in air at 550.degree. C. for 3 hours.
0.2 gram of the La-impregnated hydrotalcite produced above was
mixed with 0.36 gram of the calcined GeAPO-34/18 of Example 3 and
the resultant catalyst was evaluated in the conversion of methanol
to olefins in a fixed bed reactor equipped with an on-line gas chromatograph
for product analysis. The test conditions were 450.degree. C., 25
psig (273 kPaa) and 25 WHSV. The results of the test are summarized
in Table 2 which also shows the results obtained under the same
conditions with (a) a catalyst consisting solely of 0.36 gram of
GeAPO-34/18 and (b) a catalyst comprising 0.36 gram of GeAPO-34/18
and 0.2 gram of calcined hydrotalcite (no La impregnation).
TABLE 2 GeAPO- GeAPO- GeAPO- 34/18 + 34/18 + Catalyst 34/18 Hydrotalcite
La/Hydrotalcite C.sub.2 = (wt % of product) 31.5 29.4 27.9 C.sub.3
= (wt % of product) 43.6 44.3 46.3 C.sub.2 = +C.sub.3 = (wt % of
product) 75.0 73.7 74.2 Catalyst Life 38.9 82.0 107.9
It is clear from Table 2 that the addition of the hydrotalcite
to the GeAPO-34/18 increased the life of the catalyst by over 100%,
whereas the addition of La/hydrotalcite increased the life of the
catalyst by over 170%.
While the present invention has been described and illustrated
by reference to particular embodiments, those of ordinary skill
in the art will appreciate that the invention lends itself to variations
not necessarily illustrated herein. For example, it is contemplated
that the catalyst compositions described herein are useful in other
processes, such as catalytic cracking. For this reason, reference
should be made solely to the appended claims for purposes of determining
the true scope of the present invention. |