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
34. A process for converting a hydrocarbon oxygenate feedstock
to olefins, the process comprising contacting the feedstock with
a catalyst composition comprising: (a) a molecular sieve; and (b)
hydrotalcite; under catalytic conversion conditions, to form a product
mixture comprising olefins.
35. The process of claim 34 wherein the molecular sieve is selected
from silicoaluminophosphates, aluminophosphates, metal-containing
forms thereof and mixtures, including intergrowths, thereof.
36. The process of claim 34 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.
37. The process of claim 34 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.
38. The process of claim 34 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
39. The process of claim 34 wherein the catalyst composition comprises
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.
40. The process of claim 34 wherein the catalyst composition further
comprises a rare earth metal component.
41. The process of claim 40 wherein the catalyst composition comprises
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.
42. The process of claim 40 wherein the rare earth metal component
is lanthanum.
43. The process of claim 34 wherein the feedstock comprises methanol
and product mixture comprises ethylene and propylene.
Molecular sieve description
FIELD
[0001] 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
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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] and
[PO4] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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
[0015] 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.
[0016] Conveniently, 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. 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-18 and intergrowths of
GeAPO-34 and GeAPO-18.
[0017] 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.
[0018] Conveniently, the aluminophosphate and metalloaluminophosphate
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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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:
[0023] (a) molecular sieve; and
[0024] (b) hydrotalcite;
[0025] under catalytic conversion conditions, to form a product
mixture comprising olefins.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0026] Introduction
[0027] 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.
[0028] Molecular Sieves
[0029] 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.
[0030] 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).
[0031] 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.
[0032] 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..
[0033] 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.
[0034] 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.
[0035] 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).
[0036] 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.
[0037] 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.
[0038] 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:
mR:(M.sub.xAl.sub.yP.sub.z)O.sub.2
[0039] 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.xAl.sub.yP.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.
[0040] 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 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.
[0041] 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.
[0042] Molecular Sieve Synthesis
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] In one embodiment, the synthesis of a molecular sieve is
aided by seeds from another or the same framework type molecular
sieve.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] Hydrotalcite Additive
[0059] 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)16CO3.4H.sub.2O. 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.
[0060] 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.
[0061] 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.
[0062] 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:
[Mg.sub.2xAl.sub.2(OH).sub.4x+4]Y.sub.2/n.sup.n-.ZH.sub.2O
[0063] 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.
[0064] 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.
[0065] Synthetic hydrotalcite is commercially available and can,
for example, be obtained from Sasol North America Inc. as Condea
Pural MG70.
[0066] 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.
[0067] Rare Earth Metal Component
[0068] 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.
[0069] 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.
[0070] Catalyst Composition
[0071] 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.
[0072] 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.
[0073] In addition, the catalysts composition can contain a binder
and/or matrix material to enhance the physical characteristics of
the catalyst.
[0074] 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.
[0075] Aluminum chlorhydrol, a hydroxylated aluminum based sol
containing a chloride counter ion, has the general formula of AlmOn(OH)oClp.x(H.sub.2O)
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)24C17.12(H.sub.2O)
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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] Method of Making the Catalyst Composition
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] Process for Using the Molecular Sieve Catalyst Compositions
[0086] 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.
[0087] 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 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.
[0088] 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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.
[0093] 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.
[0094] 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.
[0095] 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.
[0096] 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.
[0097] 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.
[0098] 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.
[0099] 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.
[0100] 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.
[0101] 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.
[0102] 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.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] 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.
[0108] 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.
[0109] 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.
[0110] Non-limiting examples of suitable regeneration media include
one or more of oxygen, O3 SO3 N20 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 (172 kPaa) to about 150 psia (1034 kpaa), and conveniently
from about 30 psia (207 kpaa) to about 60 psia (414 kpaa).
[0111] 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.
[0112] 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.
[0113] 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).
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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.
[0118] 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.
[0119] 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.
[0120] 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.
[0121] 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
[0122] 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.
[0123] 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
[0124] 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.
[0125] 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.
1 TABLE 1 EMM-2 + Catalyst EMM-2 La/Hydrotalcite C2.dbd. (wt %
of product) 35.3 32.3 C3.dbd. (wt % of product) 41.0 43.7 C.sub.2.dbd.
+ C.sub.3.dbd. (wt % of product) 76.3 76.0 Catalyst Life 20.7 72.3
[0126] 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
[0127] 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-AP034/18 with La/Hydrotalcite
[0128] 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.
[0129] 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).
2TABLE 2 GeAPO- GeAPO-34/18 + GeAPO-34/18 + Catalyst 34/18 Hydrotalcite
La/Hydrotalcite C.sub.2.dbd. (wt % of 31.5 29.4 27.9 product) C.sub.3.dbd.
(wt % of 43.6 44.3 46.3 product) C.sub.2.dbd. + C.sub.3.dbd. (wt
% of 75.0 73.7 74.2 product) Catalyst Life 38.9 82.0 107.9
[0130] 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%.
[0131] 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. |