Molecular sieve abstract
The invention relates to a process for producing alkylated aromatic
hydrocarbons, preferably with an oxygen or sulfur containing alkylating
agent, in the presence of a multi-component molecular sieve catalyst
composition that includes a molecular sieve and an active metal
oxide. The invention is also directed to methods of making and formulating
the multi-component molecular sieve catalyst composition useful
in producing alkylated aromatics.
Molecular sieve claims
We claim:
1. A process for alkylating an aromatic compound by contacting
the aromatic compound with an alkylating agent under alkylation
conditions in the presence of a multi-component molecular sieve
catalyst composition comprising a molecular sieve physically mixed
with one or more active metal oxides.
2. The process of claim 1 wherein the one or more active metal
oxides comprises a non-acidic metal oxide.
3. The process of claim 1 wherein any of the one or more active
metal oxides, tested individually or as a mixture, has a CO.sub.2/NH.sub.3
chemisorption molar ratio greater than about 0.75.
4. The process of claim 1 wherein any of the one or more active
metal oxides, tested individually or as a mixture, has a CO.sub.2/NH.sub.3
chemisorption molar ratio greater than about 1.0.
5. The process of claim 1 wherein the one or more active metal
oxides comprises one or more metal oxides selected from the group
consisting of Group 2 Group 3 Group 4 Lanthanide Series, and
Actinide Series metal oxides.
6. The process of claim 1 wherein the one or more active metal
oxides comprises a Group 4 metal oxide and at least one additional
metal oxide selected from the group consisting of Group 2 Group
3 Lanthanide Series, and Actinide Series metal oxides.
7. The process of claim 1 wherein the one or more active metal
oxides comprises a zirconium or hafnium oxide in combination with
a lanthanum oxide.
8. The process of claim 1 wherein the one or more active metal
oxides comprises yttrium oxide.
9. The process of claim 1 wherein said one or more active metal
oxides comprises at least one combination of one or more metal oxides
where said combination was prepared by co-precipitation of said
one or more metal oxides and said combination is itself active.
10. The process of claim 1 wherein said one or more active metal
oxides comprises at least one active metal oxide which has been
calcined.
11. The process of claim 1 wherein the weight ratio of active metal
oxide to molecular sieve, excluding any binders or matrix material,
is in the range of about 1:100 to about 2:1.
12. The process of claim 1 wherein the weight ratio of active metal
oxide to molecular sieve, excluding any binders or matrix material,
is in the range of about 1:50 to about 1:1.
13. The process of claim 1 wherein the multi-component molecular
sieve catalyst composition has a Half-life Enhancement Index (HLEI)
greater than about 2.
14. The process of claim 1 wherein the multi-component molecular
sieve catalyst composition has an HLEI greater than about 10.
15. The process of claim 1 wherein the multi-component molecular
sieve catalyst composition has an HLEI greater than about 20.
16. The process of claim 1 wherein the molecular sieve is a crystalline
metallosilicate.
17. The process of claim 1 wherein the molecular sieve is an aluminosilicate.
18. The process of claim 1 wherein the molecular sieve comprises
at least one intermediate pore molecular sieve.
19. The process of claim 1 wherein the molecular sieve comprises
crystals with a framework type selected from the group consisting
of MFI, MTT, and MWW.
20. The process of claim 1 wherein the molecular sieve comprises
steamed ZSM-5.
21. The process of claim 1 wherein the molecular sieve comprises
at least one molecular sieve selected from the group consisting
of ITQ-13 MCM-22 ZSM-5 ZSM-23 and ZSM-48.
22. The process of claim 1 wherein the multi-component molecular
sieve catalyst composition further comprises a binder or a matrix
material or both, said binder and matrix material each being different
from each active metal oxide contained in the multi-component molecular
sieve catalyst composition.
23. The process of claim 1 wherein the alkylating agent comprises
an oxygenate.
24. The process of claim 1 wherein a diluent is present during
the step of contacting the aromatic compound with an alkylating
agent.
25. The process of claim 1 wherein the alkylating agent comprises
methanol or methanol precursors.
26. The process of claim 25 wherein a diluent comprising hydrogen,
water, or both hydrogen and water is present during the step of
contacting the aromatic compound with an alkylating agent.
27. The process of claim 26 wherein said diluent is present in
a molar ratio of hydrogen and water combined between about 1:1 and
about 5:1 with respect to total moles of reactants.
28. The process of claim 1 wherein the alkylation occurs in a fixed-bed
reactor.
29. A process for alkylating aromatic hydrocarbons, said process
comprising contacting said aromatic hydrocarbons with a multi-component
molecular sieve catalyst composition comprising crystals of molecular
sieve and particulates of one or more active metal oxides, said
contacting occurring under conversion conditions and in the presence
of an alkylating agent.
30. The process of claim 29 wherein the particulates of one or
more active metal oxides comprise a non-acidic metal oxide.
31. The process of claim 29 wherein said particulates of one or
more active metal oxides, tested as a mixture, have a CO.sub.2/NH.sub.3
chemisorption molar ratio greater than about 0.75.
32. The process of claim 29 wherein said particulates of one or
more active metal oxides, tested as a mixture, have a CO.sub.2/NH.sub.3
chemisorption molar ratio greater than about 1.0.
33. The process of claim 29 wherein the particulates of one or
more active metal oxides comprise one or more metal oxides selected
from the group consisting of Group 2 Group 3 Group 4 Lanthanide
Series, and Actinide Series metal oxides.
34. The process of claim 29 wherein the particulates of one or
more active metal oxides comprise an active Group 4 metal oxide
and at least one additional active metal oxide selected from the
group consisting of Group 2 Group 3 Lanthanide Series, and Actinide
Series metal oxides.
35. The process of claim 29 wherein the particulates of one or
more active metal oxides comprise a zirconium or hafnium oxide in
combination with a lanthanum oxide.
36. The process of claim 29 wherein the particulates of one or
more active metal oxides comprise yttrium oxide.
37. The process of claim 29 wherein said particulates of one or
more active metal oxides comprise at least one combination of one
or more metal oxides where said combination was prepared by co-precipitation
of said one or more metal oxides and said combination is itself
active.
38. The process of claim 29 wherein said particulates of one or
more active metal oxides comprise at least one active metal oxide
which has been calcined.
39. The process of claim 29 wherein the weight ratio of the particulates
of active metal oxide to the crystals of molecular sieve, excluding
any binders or matrix material, is in the range of about 1:100 to
about 2:1.
40. The process of claim 29 wherein the weight ratio of the particulates
of active metal oxide to the crystals of molecular sieve, excluding
any binders or matrix material, is in the range of about 1:50 to
about 1:2.
41. The process of claim 29 wherein the crystals of molecular sieve
comprise crystalline aluminosilicate.
42. The process of claim 1 wherein the crystals of molecular sieve
comprise intermediate or large pore molecular sieves.
43. The process of claim 29 wherein the crystals of molecular sieve
comprise crystals with a framework type selected from the group
consisting of MFI, MTT, and MWW.
44. The process of claim 29 wherein the crystals of molecular sieve
comprise crystals of at least one molecular sieve selected from
the group consisting of ITQ-13 MCM-22 ZSM-5 ZSM-23 and ZSM-48.
45. The process of claim 29 wherein the multi-component molecular
sieve catalyst composition further comprises a binder or a matrix
material or both, combined in any order with the crystals of molecular
sieve and the particulates of active metal oxide.
46. The process of claim 29 wherein the multi-component molecular
sieve catalyst composition has a Half-life Enhancement Index (HLEI)
greater than about 2.
47. The process of claim 29 wherein the multi-component molecular
sieve catalyst composition has an HLEI greater than about 10.
48. The process of claim 29 wherein the multi-component molecular
sieve catalyst composition has an HLEI greater than about 20.
49. The process of claim 29 wherein the aromatic hydrocarbons comprise
at least one of toluene and naphthalene.
50. The process of claim 29 wherein the alkylating agent comprises
an oxygenate.
51. The process of claim 29 wherein a diluent is present during
the step of contacting the aromatic hydrocarbons with an alkylating
agent.
52. The process of claim 29 wherein the alkylating agent comprises
methanol or methanol precursors.
53. The process of claim 52 wherein a diluent comprising hydrogen,
water, or both hydrogen and water is present during the step of
contacting the aromatic hydrocarbons with an alkylating agent.
54. The process of claim 53 wherein said diluent is present in
a molar ratio of hydrogen and water combined between about 1:1 and
about 5:1 with respect to total moles of reactants.
55. A process for producing one or more alkylated aromatics, the
process comprising the steps of: (a) introducing to a reactor system
a feedstock comprising at least one alkylatable aromatic and at
least one oxygen- or sulfur-containing alkylation agent, said reactor
system containing a multi-component molecular sieve catalyst composition
comprising a molecular sieve catalyst and at least one active metal
oxide; (b) withdrawing from the reactor system an effluent stream;
and (c) recovering one or more alkylated aromatics from the effluent
stream.
56. The process of claim 55 wherein the at least one active metal
oxide comprises one or more metal oxides selected from the group
consisting of Group 2 Group 3 Group 4 Lanthanide Series, and
Actinide Series metal oxides.
57. The process of claim 55 wherein the at least one active metal
oxide comprises at least one of an active zirconium metal oxide
or an active hafnium metal oxide.
58. The process of claim 55 wherein said at least one active metal
oxide comprises at least one of an active yttrium metal oxide, an
active lanthanum metal oxide, or an active scandium metal oxide.
59. The process of claim 55 wherein the molecular sieve catalyst
comprises an aluminosilicate molecular sieve or a silicoaluminophosphate
molecular sieve or both.
60. The process of claim 55 wherein said at least one alkylatable
aromatic comprises at least one of toluene or naphthalene.
61. The process of claim 55 wherein the alkylating agent comprises
at least one of methanol or dimethylether.
62. The process of claim 55 wherein a diluent comprising hydrogen,
water, or both hydrogen and water is present during the step of
contacting the aromatic compound with an alkylating agent.
63. A process for producing para-xylene, the process comprising
the steps of combining in a reactor at least one of an oxygen-containing
alkylation agent or a sulfur-containing alkylation agent with a
feedstock containing at least some toluene or benzene or both, said
reactor containing a multi-component molecular sieve catalyst composition
comprising a molecular sieve and one or more active metal oxides.
64. The process of claim 63 wherein the multi-component molecular
sieve catalyst composition further comprises a binder or a matrix
material or both, combined in any order with any or all of the other
components of the multi-component molecular sieve catalyst composition.
65. The process of claim 63 wherein the multi-component molecular
sieve catalyst composition has an HLEI greater than 20.
66. The process of claim 63 wherein a diluent comprising hydrogen,
water, or both hydrogen and water is present during the step of
contacting the aromatic compound with an alkylating agent.
67. The process of claim 66 wherein said diluent is present in
a molar ratio of hydrogen and water combined between about 1:1 and
about 5:1 with respect to total moles of reactants.
68. The process of claim 63 wherein the para-xylene selectivity
of the multi-component molecular sieve catalyst composition exceeds
about 60% for a period exceeding 150 hours at commercial operating
conditions.
69. A method for making a multi-component molecular sieve catalyst
composition, the method comprising the step of combining a) at least
one active metal oxide, b) a molecular sieve synthesized from the
combination of at least two of the group consisting of a silicon
source, a phosphorous source, and an aluminum source, optionally
in the presence of a templating agent, and c) a binder or a matrix
material or both.
70. The method of claim 69 wherein the at least one active metal
oxide comprises a non-acidic metal oxide.
71. The process of claim 69 wherein the at least one active metal
oxide comprises at least one metal oxide selected from the group
consisting of Group 2 Group 3 Group 4 Lanthanide Series, and
Actinide Series metal oxides.
72. The method of claim 69 wherein the at least one active metal
oxide comprises at least one of an active yttrium metal oxide, an
active lanthanum metal oxide, or an active scandium metal oxide.
73. The method of claim 70 wherein the at least one active metal
oxide comprises a zirconium or hafnium oxide combined with a lanthanum
oxide.
74. The method of claim 69 wherein the at least one active metal
oxide comprises at least one combination of one or more metal oxides
where said combination was prepared by co-precipitation of said
one or more metal oxides and said combination is itself active.
75. The method of claim 69 wherein the at least one active metal
oxide comprises at least one active metal oxide which has been calcined
prior to the step of combining.
76. The method of claim 70 wherein the multi-component molecular
sieve catalyst composition has a Half-life Enhancement Index (HLEI)
greater than about 2.
77. The method of claim 69 wherein the multi-component molecular
sieve catalyst composition has an HLEI greater than about 10.
78. The method of claim 69 wherein the multi-component molecular
sieve catalyst composition has an HLEI greater than about 20.
79. The method of claim 69 wherein the molecular sieve comprises
crystals with a framework-type selected from the group consisting
of MFI, MTT, and MWW; and the binder, if any, and the matrix material,
if any, are different from each active metal oxide contained in
the multi-component molecular sieve catalyst composition.
80. The method of claim 69 wherein the multi-component molecular
sieve catalyst composition further comprises a binder or a matrix
material or both, combined in any order with the other components
of the multi-component molecular sieve catalyst composition.
81. The method of claim 69 wherein the weight ratio of all active
metal oxides contained in the multi-component molecular sieve catalyst
composition to the molecular sieve contained in the multi-component
molecular sieve catalyst composition, excluding any binders or matrix
material, is in the range of about 1:100 to about 2:1
82. The method of claim 69 wherein the weight ratio of all active
metal oxides contained in the multi-component molecular sieve catalyst
composition to the molecular sieve contained in the multi-component
molecular sieve catalyst composition, excluding any binders or matrix
material, is in the range of about 1:50 to about 1:2.
83. The method of claim 69 wherein the molecular sieve, binder,
and matrix material are combined prior to combining the at least
one active metal oxide.
84. A method of making a multi-component molecular sieve catalyst
composition, the method comprising the steps of: (a) synthesizing
a molecular sieve by the method comprising the steps of: (i) forming
a first reaction mixture of at least two of the group consisting
of a silicon source, a phosphorous source, and an aluminum source;
and (ii) removing the molecular sieve from the first reaction mixture;
(b) forming an active metal oxide by the method comprising the steps
of: (i) forming a second reaction mixture of at least one metal
oxide precursor and a precipitating agent; (ii) removing the active
metal oxide from the second reaction mixture; and (c) combining
the molecular sieve and the active metal oxide.
85. The method of claim 84 wherein the active metal oxide has been
calcined prior to step (c).
86. The method of claim 84 wherein the molecular sieve and the
active metal oxide are combined with a binder or a matrix material
or both to form a multi-component molecular sieve catalyst composition.
87. The method of claim 84 wherein the molecular sieve is combined
with a matrix material or a binder or both to form a molecular sieve
catalyst composition which is then combined with the active metal
oxide.
88. The method of claim 84 wherein the molecular sieve catalyst
composition and the active metal oxide are further combined with
a matrix material or a binder or both.
89. The method of claim 84 wherein the weight ratio of the active
metal oxide to the molecular sieve, excluding any binders or matrix
material, is in the range of about 1:100 to about 2:1.
90. The method of claim 84 wherein the weight ratio of the active
metal oxide to the molecular sieve, excluding any binders or matrix
material, is in the range of about 1:50 to about 1:2.
91. A process for alkylating an aromatic compound in the presence
of the molecular sieve catalyst composition prepared by the method
of claim 69.
92. A process for alkylating an aromatic compound in the presence
of the molecular sieve catalyst composition prepared by the method
of claim 84.
93. A multi-component molecular sieve catalyst composition comprising:
(a) at least one active non-acidic metal oxide selected from the
group consisting of Group 2 Group 3 Group 4 Lanthanide Series,
and Actinide Series metal oxides; (b) a binder or a matrix material
or both; and (c) a metallosilicate molecular sieve.
Molecular sieve description
FIELD OF THE INVENTION
[0001] The present invention relates to a conversion process utilizing
a multi-component molecular sieve catalyst composition to alkylate
aromatics. The invention is also directed to a method of making
the molecular sieve catalyst composition by physically mixing solids
or particulates comprising at least one active metal oxide with
one or more molecular sieve materials.
BACKGROUND OF THE INVENTION
[0002] A variety of processes for alkylating aromatics using conventional
aluminosilicate molecular sieve catalysts are commercially available.
Various aromatic compounds are either naturally present in or are
traditionally produced from petroleum feedstock by catalytic reforming
processes.
[0003] Aromatics alkylation is an important procedure for producing
many useful chemical products. For example, para-xylene, which can
be produced by alkylating toluene with methanol, constitutes an
important starting material for manufacturing synthetic polyester
fibers, films, and resins. These polyester materials have many practical,
well known uses, such as in fabrics, carpets, and apparel. Other
alkylated aromatics have similar roles.
[0004] Methanol, the preferred alcohol for para-xylene production
from a toluene feedstock, 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.
[0005] Molecular sieves are porous solids having pores of different
sizes including crystalline molecular sieves such as zeolites, as
well as carbons and oxides. The most commercially useful molecular
sieves for the petroleum and petrochemical industries are crystalline
molecular sieves. Crystalline molecular sieves in general have a
one-, two-, or three-dimensional crystalline pore structure having
uniformly sized pores of molecular scale within each dimension.
These pores selectively adsorb molecules that can enter the pores
and exclude those molecules that are too large.
[0006] Examples of some potentially useful molecular sieves for
aromatics alkylation include aluminosilicate molecular sieves as
described in co-pending U.S. patent application Ser. No. 09/866907
(ITQ-13) and in U.S. Pat. No. 3702886 (ZSM-5), U.S. Pat. No. 4076842
(ZSM-23), U.S. Pat. No. 4397827 (ZSM-48), and U.S. Pat. No. 4954325
(MCM-22), all of which are herein fully incorporated by reference.
Aluminosilicate molecular sieves, also known as zeolites, contain
a three-dimensional microporous crystalline framework structure
of [SiO.sub.4] and [AlO.sub.4] corner sharing tetrahedral units.
Zeolites are generally synthesized by the hydrothermal crystallization
of a reaction mixture of silicon and aluminum sources. Other metallosilicate
molecular sieves with various metals (such as, for example, gallium,
iron, and/or boron) substituted for aluminum in some portion of
the crystalline framework are also known in the art.
[0007] Aluminum and phosphorus containing molecular sieve crystals
(for example, ALPO and SAPO) can be produced by the hydrothermal
crystallization of a reaction mixture of silicon, aluminum, and
phosphorus sources along with at least one templating agent as described,
for example, in U.S. Pat. No. 4440871 which is herein fully incorporated
by reference.
[0008] Molecular sieves are often formed into molecular sieve catalyst
compositions to improve their durability and to facilitate handling
in commercial conversion processes. These molecular sieve catalyst
compositions are formed by combining a molecular sieve with a matrix
material and/or a binder. Although the use of binders and matrix
materials are known for use with molecular sieves to form molecular
sieve catalyst compositions useful in alkylating aromatics, 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.
[0009] Many of the toluene alkylation processes use catalytic materials
which are prone to rapid catalyst deactivation, usually due to coke
formation, under typical reaction conditions and, therefore, require
constant regeneration. This regeneration requirement usually necessitates
the use of higher cost technology such as fluid bed reactors wherein
the catalyst is continuously regenerated.
[0010] Although a variety of treatments have been disclosed for
improving conversion, improving product selectivity, and/or reducing
coke formation, there is still a significant problem with rapid
catalyst de-activation due to coke formation at the reaction conditions
required for alkylation of aromatics. It would therefore be desirable
to have an improved molecular sieve catalyst composition having
longer lifetimes and, preferably, also having better conversion
rates, product selectivity, and commercially desirable operability
and cost advantages.
SUMMARY OF THE INVENTION
[0011] This invention provides for a multi-component molecular
sieve catalyst composition, a method for making or formulating the
multi-component molecular sieve catalyst composition, and a process
for using the multi-component molecular sieve catalyst composition
to produce one or more alkylated aromatics.
[0012] In one embodiment the invention is directed to a method
for making the multi-component molecular sieve composition of the
invention by combining, contacting, mixing, or the like, a molecular
sieve and at least one active metal oxide, preferably a non-acidic
metal oxide. Preferably the molecular sieve is synthesized from
the combination of two or more of a silicon source, an aluminum
source, and a phosphorous source, optionally in the presence of
a templating agent, and the active metal oxide is an oxide of a
Group 2 Group 3 Group 4 Lanthanide Series, or Actinide Series
metal. More preferred active metal oxides are combinations of a
Group 4 metal oxide with one or more selected from Group 2 Group
3 Lanthanide Series, or Actinide Series metal oxides. Even more
preferred are i) zirconium and/or hafnium oxides combined with a
Group 3 metal oxide such as scandium, lanthanum, or yttrium metal
oxide or ii) yttrium oxide. More preferably, the molecular sieve
is an intermediate pore size aluminosilicate molecular sieve and
the metal oxide is a zirconium and/or hafnium metal oxide co-precipitated
with lanthanum oxide. Even more preferably, the active metal oxide
is a co-precipitated combination of zirconium and lanthanum oxides,
and the molecular sieve composition is a ZSM-5 catalyst modified
as described U.S. Pat. No. 6423879 which is herein fully incorporated
by reference.
[0013] In another embodiment the invention relates to a method
for making a multi-component molecular sieve catalyst composition
by combining, contacting, mixing, or the like, a molecular sieve,
a matrix material, a binder, and at least one active metal oxide,
wherein the active metal oxide is different from both the binder
and the matrix material. Preferably, the active metal oxide is a
non-acidic oxide of a Group 2 Group 3 Group 4 Lanthanide Series,
or Actinide Series metal, and the molecular sieve is synthesized
from the combination of two or more of a silicon source, an aluminum
source, and a phosphorous source, optionally in the presence of
a templating agent. In a more preferred embodiment, the molecular
sieve and the binder and/or matrix material are made into a formulated
molecular sieve catalyst composition that is then contacted, mixed,
combined, spray dried, or the like, with at least one active metal
oxide, preferably an active non-acidic Group 2 Group 3 Group 4
Lanthanide Series, and/or Actinide Series metal oxide, and more
preferably a Group 4 metal oxide such as hafnium or zirconium metal
oxide combined with a Group 2 Group 3 Lanthanide Series, or Actinide
Series metal oxide.
[0014] In one more embodiment, the multi-component molecular sieve
catalyst composition, formulated with a binder and/or matrix or
otherwise, of the invention, discussed above, has a Half-life Enhancement
Index (HLEI) significantly greater than catalyst compositions without
an active metal oxide, that have, by definition, a HLEI of 1. HLEI
is the ratio of the half-life of the multi-component molecular sieve
catalyst composition described herein to that of the molecular sieve
or molecular sieve catalyst composition in the absence of an active
metal oxide. Determination of HLEI is discussed later in this patent
specification.
[0015] In still another embodiment of the invention, a multi-component
molecular sieve catalyst composition is made by a method comprising
the steps of: (i) synthesizing a molecular sieve by the method comprising
the steps of: (a) forming a first reaction mixture of at least two
of the group consisting of a silicon source, a phosphorous source,
and an aluminum source, optionally containing one or more templating
agents, and (b) removing the molecular sieve from the first reaction
mixture; (ii) producing an active metal oxide by the method comprising
the steps of: (a) forming a second reaction mixture of at least
one active metal oxide precursor, (b) removing an active metal oxide
from the second reaction mixture, and (iii) combining the molecular
sieve and the active metal oxide. Preferably the active metal oxide
is calcined prior to combining the molecular sieve and the active
metal oxide.
[0016] In yet another embodiment, the invention is directed to
a process for alkylating aromatics in the presence of any of the
above multi-component molecular sieve catalyst compositions. In
particular, the process involves alkylating aromatics, preferably
toluene, with an alkylating agent, preferably an oxygen- or a sulfur
containing alkylating agent, more preferably an alkylating agent
comprising an alcohol, and most preferably an alkylating agent comprising
methanol, in the presence of one or more of the multi-component
molecular sieve catalyst compositions discussed above.
[0017] The invention is also directed to a composition of matter
of any one of the multi-component molecular sieve catalyst compositions
described above. The invention is further directed to a multi-component
molecular sieve catalyst composition comprising the use of at least
one active metal oxide in combination with a molecular sieve, optionally
including a matrix material and/or a binder, in which the active
metal oxides are different from the matrix material and/or the binder,
for use in alkylating aromatics using an oxygen- or sulfur-containing
alkylating agent.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Introduction
[0019] This invention is directed toward a multi-component molecular
sieve catalyst composition, a method for making or formulating the
multi-component molecular sieve catalyst composition, and a process
for alkylating aromatics using the multi-component molecular sieve
catalyst composition. It has been found that combining a molecular
sieve with an active metal oxide results in a multi-component molecular
sieve catalyst composition capable of alkylating one or more aromatics
preferably in the presence of oxygenates, more particularly methanol,
with a longer half-life than the molecular sieve alone. The preferred
active metal oxides are those having a Group 2 (for example calcium
and magnesium), Group 3 (for example scandium, yttrium, and lanthanum),
Group 4 (for example zirconium and hafnium), Lanthanide Series (for
example cerium, praseodymium, and neodymium), and/or Actinide Series
(for example thorium and protactinium) metal from the Periodic Table
of Elements using the IUPAC format described in the CRC Handbook
of Chemistry and Physics, 79th Edition, CRC Press, Boca Raton, Fla.
(1998). Also, surprisingly, the multi-component molecular sieve
catalyst compositions have longer lifetimes, at least in part because
they are less susceptible to coke formation which is well known
to reduce catalyst activity. It has also been discovered that the
multi-component molecular sieve catalyst compositions are often
more selective to para-xylene when toluene is used as the feedstock.
In this regard, in particular in the conversion of toluene to at
least para-xylene, the production of less desirable ortho- and meta-xylene
is reduced.
[0020] Molecular Sieves
[0021] Molecular sieves have various chemical, physical, and framework
characteristics. 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. A framework-type
describes the topology and connectivity of the tetrahedrally coordinated
atoms constituting the framework and makes an abstraction of the
specific properties for those materials. 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.
[0022] Non-limiting examples of these molecular sieves include
intermediate pore size molecular sieves having a pore size in at
least one dimension from about 5 .ANG. to about 7 .ANG., including,
for example, AEL, EUO, FER, HEU, MEI, MEL, MFI, MFS, MTT, MTW, MWW,
and TON structure type molecular sieves. Non-limiting examples of
specific intermediate pore size molecular sieves include ITQ-13
(not yet assigned a structure type), MCM-22 ZSM-5 ZSM-11 ZSM-12
ZSM-22 ZSM-23 ZSM-34 ZSM-35 ZSM-38 ZSM48 ZSM-50 and ZSM-57.
Examples of large pore molecular sieves include molecular sieves
having a pore size of at least about 7 .ANG. such as AET, AFI, BEA,
EMT, FAU, LTL, MAZ, MEI, MOR, OFF, and VFI structure type molecular
sieves. Non-limiting examples of large pore molecular sieves include
for example mazzite, offretite, Zeolite L, VPI-5 Zeolite Y, Zeolite
X, omega, Beta, ZSM-3 ZSM-4 ZSM-18 ZSM-20 and SAPO-37. Non-limiting
examples of the preferred molecular sieves, particularly for methylating
a toluene containing feedstock into xylenes, include AEL, BEA, FAU,
FER, LTL, MFI, MOR, MTT, MTW, MWW, and TON structure types. For
a naphthalene feedstock, preferred molecular sieve configurations
would include, but not be limited to, BEA, FAU, MOR, and MWW structure
types. In one preferred embodiment, the molecular sieve of the invention
has an MFI topology (such as ZSM-5) or an MTT topology (such as
ZSM-23), or a combination thereof, most preferably an MFI topology.
[0023] Preferred molecular sieves include intermediate and large
pore configurations, preferably having an average pore diameter
in the range of about 3.5 .ANG. to about 15 .ANG., more preferably
in the range from about 5 .ANG. to about 7 .ANG..
[0024] Aluminosilicate molecular sieves have been described in
detail in numerous publications, including, for example, co-pending
U.S. patent application Ser. No. 09/866907 (ITQ-13) and U.S. Pat.
No. 3702886 (ZSM-5), U.S. Pat. No. 4076842 (ZSM-23), U.S. Pat.
Nos. 4397827 and 4358397 (ZSM-48), and U.S. Pat. No. 4954325
(MCM-22). Silicon, aluminum, and phosphorous based molecular sieves
and metal containing silicon, aluminum, and phosphorous based molecular
sieves are also known in the art. 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.
[0025] The synthesis of molecular sieves is described in many of
the references known to those skilled in the art. Generally, molecular
sieves are synthesized by the hydrothermal crystallization of one
or more of a source of aluminum, a source of phosphorous, a source
of silicon, a templating agent, and a metal containing compound.
Typically, a combination of sources of silicon, aluminum, and/or
phosphorous, optionally with one or more templating agents and/or
one or more metal containing compounds are placed in a sealed pressure
vessel, optionally lined with an inert plastic such as polytetrafluoroethylene,
and heated under a crystallization pressure and temperature until
a crystalline material is formed, which is then recovered by filtration,
centrifugation, and/or decanting.
[0026] Aluminosilicate molecular sieves can be crystallized over
a wide range of silicon (Si) to aluminum (Al) ratios. This Si/Al.sub.2
ratio is one factor that dictates the level of acidity or acid activity
a particular molecular sieve will exhibit. Normally, the higher
the Si/Al.sub.2 ratio, the less acidic an aluminosilicate molecular
sieve will be and usually less prone to coking. The crystal size
and the dimensions of the channel system are also important variables
affecting coke formation. A high Si/Al.sub.2 ratio is generally
preferred for alkylation processes using aluminosilicates. In one
embodiment, the molecular sieve, as synthesized, is an aluminosilicate
molecular sieve having a Si/Al.sub.2 ratio greater than 12 preferably
between 40 and 1000 and most preferably between 100 and 500 all
as measured prior to any treatment of the molecular sieve to reduce
its diffusivity. Different constraints and preferences will apply
to molecular sieves containing phosphorous; for example in SAPOs,
lower silica content correlates to lower acidity.
[0027] Method for Making Molecular Sieve Catalyst Compositions
[0028] The crystals of molecular sieve can be formed into a wide
variety of forms. Generally speaking, the particles can be in the
form of a powder, a granule, or a molded product, such as an extrudate
having particle size sufficient to pass through a 2 mesh (Tyler)
screen and be retained on a 400 mesh (Tyler) screen. In cases where
the catalyst is molded, such as by extrusion, the crystals can be
extruded before drying or partially dried and then extruded or the
crystals can be calcined to remove organic template and then extruded.
All of these forms will be referred to herein as "crystals."
[0029] In the case of many catalysts, it is desirable that crystalline
molecular sieves be incorporated with binder material resistant
to the temperature and other conditions employed in organic conversion
processes. Such binder materials include synthetic or naturally
occurring substances as well as inorganic materials such as clay,
silica, and/or metal oxides. The latter may be either naturally
occurring or in the form of gelatinous precipitates or gels including
mixtures of silica and metal oxides. Naturally occurring clays which
can be composited with the zeolite include those of the montmorillonite
and kaolin families, which families include the sub-bentonites and
the kaolins commonly known as Dixie, McNamee-Georgia and Florida
clays or others in which the main mineral constituent is halloysite,
kaolinite, dickite, nacrite, or anauxite. Such clays can be used
in the raw state as originally mined or initially subjected to calcination,
acid treatment, or chemical modification. In one embodiment, the
binder is different from the active metal oxide.
[0030] In addition to the foregoing materials, the molecular sieves
may be composited with a porous matrix material, such as alumina,
silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,
silica-beryllia, and silica-titania, as well as ternary compositions,
such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia,
and silica-magnesia-zirconia. The molecular sieve may also be composited
with materials such as the zeolitic materials which are disclosed
in U.S. Pat. No. 5993642 which is herein fully incorporated by
reference. In one embodiment, the matrix material is different from
the active metal oxide.
[0031] The relative proportions between the molecular sieve component
and the binder and/or matrix material will vary widely with the
molecular sieve content ranging from about 1 to about 99 percent
by weight, more preferably in the range of about 10 to about 70
percent by weight of molecular sieve component, and still more preferably
from about 20 to about 50 percent.
[0032] In one embodiment, the binder, the molecular sieve, and
the matrix material are combined in the presence of a liquid to
form a molecular sieve catalyst composition. The combination is
then subjected to calcination.
[0033] Upon combining the molecular sieve and the matrix material,
optionally with a binder, in a liquid to form a slurry, mixing,
preferably rigorous mixing is needed to produce a substantially
homogeneous mixture containing the 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.
[0034] The molecular sieve composition, the matrix material, and
the optional binder are in the same or different liquid and are
combined in any order, together, simultaneously, sequentially, or
a combination thereof. In a preferred embodiment, the same liquid,
preferably water, is used. The molecular sieve composition, matrix
material, and optional binder are combined in a liquid as solids,
substantially dry or in a dried form, or as slurries, together or
separately. If solids are added together as dry or substantially
dried solids, it is preferable to add a limited and/or controlled
amount of liquid.
[0035] In one embodiment, the uniform slurry of the molecular sieve,
binder, and matrix materials is fed to a forming unit that produces
the formed molecular sieve catalyst composition. The forming unit
may be a spray dryer maintained at a temperature sufficient to remove
most of the liquid from the slurry and from the resulting molecular
sieve catalyst composition. The resulting catalyst composition when
formed in this way takes the form of microspheres. In an alternative
embodiment, the molecular sieve catalyst composition may be formed
into tablets, pellets, granules, beads or the like through a process
such as auger extrusion. To facilitate such an extrusion process,
extrusion aids such as polymers, for example poly vinyl acetate
(PVA), or cellulose derivatives may be added to the formulation
during mixing.
[0036] Once the molecular sieve catalyst composition is formed
in a substantially dry or dried state, to further harden and/or
activate the formed molecular sieve catalyst composition, a heat
treatment such as calcination, at an elevated temperature is usually
performed. A conventional calcination environment is air that typically
includes a small amount of water vapor. Typical calcination temperatures
are in the range from about 400.degree. C. to about 1000.degree.
C., preferably from about 500.degree. C. to about 800.degree. C.,
and most preferably from about 550.degree. C. to about 700.degree.
C., preferably in a calcination environment such as air, nitrogen,
helium, flue gas (combustion product lean in oxygen), or any combination
thereof.
[0037] In a preferred embodiment, the molecular sieve catalyst
or molecular sieve catalyst composition is heated in air from room
temperature to about 540.degree. C., at a heating rate of about
5.degree. C./min and then the temperature is maintained at about
540.degree. C. for about 4 hours to about 6 hours.
[0038] The molecular sieves and molecular sieve catalyst compositions
prepared by the process of the present invention may be further
ion exchanged before or after calcination either to replace at least
in part the original alkali metal present in the zeolite with a
different cation, e.g. a metal such as nickel, copper, zinc, palladium,
platinum, calcium, or rare earth metal, or to provide a more acidic
form of the molecular sieve by exchange of alkali metal with intermediate
ammonium, followed by calcination of the ammonium form to provide
the acidic hydrogen form. The acidic form of the molecular sieve
may be readily prepared by ion exchange using a suitable acidic
reagent such as ammonium nitrate. The molecular sieve may then be
calcined at a temperature of about 400.degree. C. to about 550.degree.
C. to remove ammonia and create the hydrogen form. Particularly
preferred cations will depend on the use of the zeolite and include
hydrogen, rare earth metals, and metals of Groups 2 3 4 8 9
10 11 12 13 and 14 of the Periodic Table of the Elements.
[0039] In another preferred embodiment, the molecular sieve catalyst
or molecular sieve catalyst composition is first selectivated with
a selectivating agent prior to use in the alkylation process. The
term "selectivating agent" is used herein to indicate
substances that will increase the shape-selectivity (e.g., paraselectivity)
of the molecular sieve catalyst. Some non-limiting examples of selectivation
include treating the molecular sieve with phosphorus and/or boron
oxide, coke, or various silicon-containing compounds.
[0040] Selectivation may also be accomplished by exposing the catalyst
in a reactor bed to a thermally decomposable organic compound, e.g.,
toluene, at a temperature in excess of the decomposition temperature
of said compound, e.g., from about 480.degree. C. to about 650.degree.
C., more preferably 540.degree. C. to 650.degree. C.; at a weight
hourly space velocity (WHSV) in the range of from about 0.1 to 20
kg of feed per kg of catalyst per hour; at a pressure in the range
of from about 1 to 100 atmospheres; and in the presence of 0 to
about 2 moles of hydrogen per mole of organic compound, more preferably
from about 0.1 to about 2 moles of hydrogen per mole of organic
compound; and optionally in the presence of 0 to 10 moles of nitrogen
or another inert gas per mole of organic compound. This process
is conducted for a period of time until the desired quantity of
coke has deposited on the catalyst surface.
[0041] Furthermore, selectivation may be accomplished using organosilicon
compounds as selectivating agents. The organosilicon compounds used
in one embodiment comprise polysiloxane, including silicone and
siloxanes, and a silane including disilanes and alkoxysilanes. Organosilicon
compounds include siloxanes as represented by the general formula:
1
[0042] wherein R.sub.1 is hydrogen or a halogen, hydroxyl, alkyl,
halogenated alkyl, aryl aralkyl, halogenated aralkyl, alkaryl, or
halogenated alkaryl group. The hydrocarbon substituents generally
contain from 1 to about 10 carbon atoms, preferably methyl, ethyl,
or phenyl groups. R.sub.2 is selected from the same group as R.sub.1
and n is an integer of at least 2 and generally in the range of
3 to about 1000. The molecular weight of the organosilicon compound
employed is generally about 80 to about 20000 and preferably about
150 to about 10000. Examples of organosilicon compounds include,
but are not limited to, dimethyl silicone, diethyl silicone, phenylmethyl
silicone, methylhydrogen silicone, ethylhydrogen silicone, phenylhydrogen
silicone, methylethyl silicone, phenylethyl silicone, diphenyl silicone,
methyltrifluoropropyl silicone, ethyltrifluoropropyl silicone, polydimethyl
silicone, tetrachlorophenylmcthyl silicone, tetrachlorophenylethyl
silicone, tetrachlorophenylphenyl silicone, methylvinyl silicone,
and ethylvinyl silicone. The silicone compound need not be linear
but may be cyclic as for example hexamethyl cyclotrisiloxane, octamethyl
cyclotetrasiloxane, hexaphenyl cyclotrisiloxane, and octaphenyl
cyclotetrasiloxane. Mixtures of these compounds are also useful
as are silicones with other functional groups.
[0043] Other organosilicon compounds, including silanes and alkoxy
silanes, such as tetramethoxy silane, can also be utilized as selectivating
agents. These useful silicon-containing selectivating agents include
silanes characterized by the general formula: 2
[0044] wherein R, R.sub.1 R.sub.2 and R.sub.3 are independently
selected from the group consisting of hydrogen, hydroxyl, halogen,
alkyl, halogenated alkyl, alkoxy, aryl, and halogenated alkaryl
groups. Mixtures of these compounds are also useful.
[0045] Preferred silicon-containing selectivating agents include
dimethylphenylmethyl polysiloxane (e.g., Dow-550) and phenylmethyl
polysiloxane (e.g., Dow-710), both available from Dow Chemical Co.
in Midland, Mich.
[0046] Examples of suitable carriers for the selectivating agents,
preferably silicon compounds, include linear, branched, and cyclic
alkanes having five or more carbons. In the methods of the present
invention it is preferred that the carrier be a linear, branched,
or cyclic alkane having a boiling point greater than about 70.degree.
C. and most preferably containing 6 or more carbons. Optionally,
mixtures of low volatility organic compounds, such as hydrocracker
recycle oil, can be employed as carriers. The most preferred low
volatility hydrocarbon carriers of selectivating agents are decane
and dodecane.
[0047] The catalyst can be selectivated by single or multiple treatments
with a liquid organosilicon compound in a liquid carrier followed
by calcination of the treated material in an oxygen containing atmosphere.
The catalyst can also be selectivated with both silica and coke.
Other techniques such as steaming and impregnation with various
compounds have also been found to alter the properties (e.g. activity,
selectivity, and/or stability) of the molecular sieve structure.
[0048] Active Metal Oxides
[0049] Active metal oxides of the invention are those metal oxides,
different from typical binders and/or matrix materials, that, when
used in combination with a molecular sieve, provide benefits in
catalytic conversion processes. Preferred metal oxides are those
metal oxides having a Group 2 Group 3 Group 4 Lanthanide Series,
and/or Actinide Series metal from the Periodic Table of Elements
using the IUPAC format described in the CRC Handbook of Chemistry
and Physics, 79th Edition, CRC Press, Boca Raton, Fla. (1998). More
preferred active metal oxides are Group 3 (preferably yttrium or
lanthanum) oxides alone or Group 4 metal oxides such as zirconium
and/or hafnium oxide in combination with a Group 2 and/or Group
3 metal oxide. In one embodiment, the most preferred active metal
oxide is an active yttrium oxide. In another embodiment, the preferred
active metal oxide is a zirconium and/or hafnium metal oxide mixed
with lanthanum oxide. In yet another embodiment, the preferred active
metal oxide is non-acidic or basic. Active metal oxides of this
invention include other oxides such as MgO and hydrotalcite-derived
mixed magnesium-aluminum non-acidic oxides.
[0050] While there are many different benefits in catalytic conversion
processes, one of the most desirable is an extension of the catalyst
composition life. Quantification of the extension in the molecular
sieve catalyst composition life can be determined using the Half-life
Enhancement Index (HLEI) as defined by the following equation: 1
HLEI = Half - life of Catalyst in Combination with Active Metal
Oxide Half - life of Catalyst
[0051] where the half-life of the catalyst is the processing time
until the conversion of feedstock by the catalyst falls below 50%
of the initial conversion rate for that feedstock. Similarly the
half-life of the catalyst in combination with active metal oxide,
the multi-component molecular sieve catalyst composition, is the
processing time under the same test conditions and using the same
weight of molecular sieve until the conversion of feedstock falls
below 50% of the initial conversion rate for that feedstock. HLEI
is measured at conditions closely approximating the reaction conditions
under which either the molecular sieve catalyst composition or the
multi-component molecular sieve catalyst composition would commercially
be used, provided that reaction conditions for both tests will be
held constant, the weight hourly space velocity (WHSV) will be held
constant based on the quantity of molecular sieve present in each
test, and that quantity of molecular sieve will also be held constant.
Initial conversion percentage will be the conversion percentage
measured at some point within the first four hours of reaction runtime,
preferably within the first hour, and measured at the same time
on-stream for each of the molecular sieve catalyst composition and
the multi-component molecular sieve catalyst composition being compared.
All reaction conditions including WHSV with respect to the molecular
sieve, not the multi-component molecular sieve catalyst composition,
must be held constant for the individual half-life determinations
to get a meaningful HLEI comparison between the molecular sieve
or molecular sieve composition and the multi-component molecular
sieve composition.
[0052] A metal oxide that is not active will have little or no
effect on the lifetime of the catalyst composition, or will shorten
the lifetime of the catalyst composition, and will therefore have
an HLEI less than or approximately equal to 1. Active metal oxides
of the invention are those metal oxides, different from typical
binders and/or matrix materials, that, when used in combination
with a molecular sieve, provide a multi-component molecular sieve
catalyst composition that has an HLEI greater than 1. By definition,
a molecular sieve catalyst composition that has not been combined
with an active metal oxide will have an HLEI equal to 1.0.
[0053] In one embodiment, the active metal oxide, when combined
with a molecular sieve, enhances the HLEI of the molecular sieve
in an alkylation of toluene to produce xylenes, particularly para-xylene.
In another embodiment, the multi-component molecular sieve catalyst
composition of the invention, containing one or more active metal
oxides has an HLEI greater than 1. In a preferred embodiment, the
HLEI of the multi-component molecular sieve catalyst composition
containing one or more active metal oxides is preferably greater
than about 2 more preferably greater than about 10 even more preferably
greater than about 20 and most preferably greater than about 100.
In another preferred embodiment, the half-life of the multi-component
molecular sieve composition under typical reactor conditions is
preferably greater than 1 day, more preferably greater than 10 days,
and most preferably greater than 2 months.
[0054] In one embodiment, the active metal oxide of the invention
may not consist solely or substantially of oxides of silicon, aluminum,
phosphorus, or combinations thereof.
[0055] In yet another embodiment, the active metal oxides of the
invention are non-acidic or basic metal oxides as determined by
the molar ratio of chemisorption of CO.sub.2 and NH.sub.3 over these
metal oxide materials. CO.sub.2 a mild acid, is used to titrate
the basic sites present on the metal oxide being tested. Likewise,
NH.sub.3 a strong base, is titrated to indicate the acidic sites
on the material. Many factors determine the actual amount of chemisorption
such as surface area of the material (often significantly affected
by the metal oxide preparation method), the temperature at which
the chemisorption is tested, and the pressure at which the chemisorption
is tested. For the purposes of this invention, a "non-acidic"
oxide is defined as an oxide having a molar ratio of chemisorption
of CO.sub.2 per gram of metal oxide to the chemisorption of NH.sub.3
per gram of metal oxide greater than about 0.5 when tested as described
below.
[0056] Testing to determine the molar ratio of chemisorption of
CO.sub.2 per gram of metal oxide to the chemisorption of NH.sub.3
per gram of metal oxide was conducted using a Mettler TGA/SDTA 851
thermogravimetric analysis system at ambient pressure. The metal
oxide sample was calcined in flowing air to about 700.degree. C.
(except as noted in Table 1) for about three hours, at least until
a constant sample weight was obtained. The temperature of the sample
was then reduced in flowing air (helium could also be used) to the
desired temperature of chemisorption. Next, the sample was allowed
to equilibrate at the desired temperature in flowing helium and
weighed. Chemisorption of carbon dioxide was measured at 100.degree.
C., and chemisorption of ammonia was measured at 250.degree. C.
After being weighed, the sample was subjected to a number of pulses
(about 12 seconds/pulse) of a gaseous mixture containing helium
and either carbon dioxide or ammonia until a constant weight was
obtained. The gas mixtures contained about 10 weight percent carbon
dioxide or ammonia with the remainder being helium. After each pulse
of the gas mixture being tested, the metal oxide sample was flushed
with flowing helium for about 3 minutes. About 20 separate pulses
of the gas mixture was used in each test. The increase in weight
of the sample in terms of mg/g metal oxide based on the metal oxide
sample weight after calcination was used to determine the moles
of CO.sub.2 or NH.sub.3 adsorbed per gram of metal oxide.
[0057] Molar ratios of chemisorption of CO.sub.2 per gram of metal
oxide to the chemisorption of NH.sub.3 per gram of metal oxide for
some examples of metal oxide materials tested are shown in Table
1. Preferred molar ratios of CO.sub.2/NH.sub.3 chemisorption, tested
as described above, are greater than about 0.5 more preferred ratios
are greater than about 0.75 and the most preferred ratios are greater
than about 1.0.
1 TABLE 1 Calcination CO.sub.2/NH.sub.3 Chemisorption Material
Tested Temperature, .degree. C. Molar Ratio TiO.sub.2 700 0.33 2%
CeO.sub.x/ZrO.sub.2 700 0.33 5% CeO.sub.x/ZrO.sub.2 700 0.41 La.sub.2O.sub.3
700 0.86 La.sub.2O.sub.3 600 1.21 10% Y.sub.xO.sub.y/ZrO.sub.2 700
1.88 ZrO.sub.2 700 1.95 ZrO.sub.2 500 2.00 5% Y.sub.xO.sub.y/ZrO.sub.2
700 3.13 5% CaO.sub.x/ZrO.sub.2 700 3.77 5% La.sub.xO.sub.y/ZrO.sub.2
700 4.86 MgO 700 11.47 CeO.sub.2 700 12.27 Y.sub.2O.sub.3 700 14.95
[0058] The active metal oxides are prepared using a variety of
methods. It is preferable that the active metal oxide is made from
an active metal oxide precursor, such as a metal salt. Other suitable
sources of active metal oxides include compounds that form these
metal oxides during calcination, such as oxychlorides and nitrates.
A further suitable source of metal oxides includes salts containing
the cation of the desired metal, such as halides, nitrates, and
acetates. Alkoxides are also sources of metal oxides, for example
zirconium n-propoxide.
[0059] In one embodiment, the active metal oxide is hydrothermally
treated under conditions that include a temperature of at least
80.degree. C., preferably at least 100.degree. C. The hydrothermal
treatment typically takes place in a sealed vessel at greater than
atmospheric pressure, however, a preferred mode of treatment involves
the use of an open vessel under reflux conditions. Agitation of
the active metal oxide in the liquid medium, for example, by the
action of refluxing liquid and/or stirring, promotes the effective
interaction of the oxide with the liquid medium. The duration of
the contact of the oxide with the liquid medium is preferably at
least 1 hour, preferably at least 8 hours. The liquid medium for
this treatment preferably has a pH of about 7 or greater, preferably
9 or greater. Non-limiting examples of suitable liquid media include
water, hydroxide solutions (including hydroxides of NH.sub.4+, Na.sup.+,
K.sup.+, Mg.sup.2+, and Ca.sup.2+), carbonate and bicarbonate solutions
(including carbonates and bicarbonates of NH.sub.4.sup.+, Na.sup.+,
K.sup.+, Mg.sup.2+, and Ca.sup.2+), pyridine and its derivatives,
and alkyl/hydroxylamines.
[0060] In yet another embodiment, the active metal oxide is prepared
by first preparing a liquid solution comprising a source of an active
metal oxide, such as a salt of the metal. Suitable sources include,
but are not limited to, salts or mixtures of salts containing a
Group 2 Group 3 Group 4 Lanthanide Series, or Actinide Series
metal, such as nitrates, sulfates, and halides. This solution containing
a source of an active metal oxide is then subjected to conditions
sufficient to cause precipitation of the solid oxide material, such
as by the addition of a precipitating reagent to the solution, preferably
a base such as sodium hydroxide or ammonium hydroxide. Water is
a preferred solvent for these solutions. The temperature at which
the liquid medium is maintained during the precipitation is preferably
less than about 200.degree. C., more preferably in the range of
from about 0.degree. C. to about 200.degree. C. This liquid medium
is preferably maintained at an ambient temperature, for example
room temperature, or the liquid is cooled or heated. A preferred
range of temperatures for precipitation is from about 20.degree.
C. to about 100.degree. C. The resulting gel is preferably then
hydrothermally treated at temperatures of at least 80.degree. C.,
preferably at least 100.degree. C. The hydrothermal treatment typically
takes place in a sealed vessel at greater than atmospheric pressure
or at ambient pressures. The gel, in one embodiment, is hydrothermally
treated for up to 10 days, preferably up to 5 days, most preferably
up to 3 days. The resulting material is then recovered, for example
by filtration or centrifugation, washed, and dried. The resulting
particulate material is preferably then calcined, preferably in
an oxidizing atmosphere, at a temperature of at least 400.degree.
C., preferably at least 500.degree. C., more preferably from about
600.degree. C. to about 900.degree. C., and most preferably from
about 650.degree. C. to about 800.degree. C. The calcination time
is preferably up to 48 hours, more preferably for about 0.5 hours
to about 24 hours, and most preferably for about 1 hour to about
10 hours. In a most preferred embodiment, calcination is carried
out at about 700.degree. C. for about 1 hour to about 3 hours.
[0061] Although preferred methods of preparing metal oxides are
described above, other methods for preparing the active metal oxides
are known in the art and may be used within the scope of this invention.
[0062] In an embodiment, it is preferred to utilize two or more
active metal oxides, preferably one Group 4 metal oxide and one
or more selected from Group 2 Group 3 Lanthanide Series, and Actinide
Series metal oxides. When two or more metal oxides are used, they
may either be co-precipitated or precipitated separately and combined
with each other at any later stage of processing including as calcined
solid particles. When two or more metal oxides are used, the metal
oxides may be combined with each other before or after any one or
more metal oxides have been combined with the molecular sieve, including
any combination which also includes a binder and/or matrix material.
Any method of combining the active metal oxides with each other,
such as impregnation, regardless of whether or not other materials
are also combined with the metal oxides before, after, or at the
time of combining the metal oxides, is within the scope of this
invention.
[0063] In another embodiment, the metal oxides are combined in
slurry or hydrated state or in a substantially dry or dried state,
preferably the metal oxides are combined in a hydrated state. In
a preferred embodiment, the mixture of metal oxides can be considered
as having atomic level mixing of the two or more metals within the
oxide, in which such atomic level mixing is achieved during synthesis
of the mixed metal oxide. Such a mixed metal oxide will be considered
to be an active metal oxide if the mixed metal oxide, when used
in combination with a molecular sieve, provides an HLEI greater
than 1.0 in catalytic conversion processes, regardless of whether
or not all of the metal oxides incorporated into the mixed metal
oxide are individually active.
[0064] In an embodiment where two or more metal oxides are combined,
they may be combined in any proportion. Mole percent of any one
metal oxide as compared to the total moles of metal oxides used
in preparing the active metal oxide may range from about 0% to about
100%, preferably from about 1% to about 99%, more preferably from
about 3% to about 97%, and most preferably from about 5% to about
95%.
[0065] In an embodiment, where the active metal oxide contains
one or more Group 4 metal oxides and a second metal oxide consisting
of any combination of one or more metal oxides selected from Group
2 Group 3 Lanthanide Series, and Actinide Series metal oxides,
the mole ratio of the Group 4 metal oxides to the second metal oxide,
taken as a group, is in the range of from 1000:1 to 1:1000 based
on the total moles of the Group 4 and second metal oxides, preferably
the mole ratio is in the range of from about 500:1 to about 1:2
more preferably from about 100:1 to about 1:1 and most preferably
from about 50:1 to about 2:1.
[0066] In yet another embodiment, the active metal oxide, preferably
containing a Group 4 metal oxide and a second metal oxide consisting
of any combination of one or more metal oxides selected from Group
2 Group 3 Lanthanide Series, or Actinide Series metal oxides,
has 1 percent to 25 percent by weight of the second metal oxide
combination based on the total weight of the active metal oxide,
more preferably from about 1 percent to about 20 percent, and most
preferably from about 1 percent to about 15 percent.
[0067] Some preferred combinations of metal oxides include a zirconium
and/or hafnium metal oxide from Group 4 with either a Group 2 calcium
oxide or a Group 3 lanthanum and/or yttrium oxide.
[0068] In a preferred embodiment the metal oxides are calcined
either before or after being combined.
[0069] Multi-Component Molecular Sieve Composition
[0070] The multi-component molecular sieve composition of the invention
includes any one of the molecular sieves and/or molecular sieve
compositions previously described mixed with any one or more of
the active metal oxides described above. In one embodiment, more
than one type of molecular sieve is used in the multi-component
molecular sieve catalyst composition. Preferably, the molecular
sieves are those resulting from the synthesis mixture of phosphorous-,
aluminum-, and/or silicon-containing components, preferably while
stirring and/or agitating and/or seeding with a crystalline material,
optionally with an alkali metal, in a solvent such as water, and
optionally with one or more templating agents, to form a synthesis
mixture that is then heated under crystallization conditions of
pressure and temperature as are known in the art. More preferably,
the molecular sieve is an intermediate pore size metallosilicate
molecular sieve, and most preferably an intermediate pore size aluminosilicate
molecular sieve. Even more preferably, the active metal oxide is
a co-precipitated combination of zirconium and lanthanum oxides,
and the molecular sieve composition is a ZSM-5 catalyst modified
as described U.S. Pat. No. 6423879 hereafter referred to as "steamed
ZSM-5."
[0071] In one embodiment, the crystals of molecular sieve are first
formed and are then combined with the active metal oxide, preferably
in a substantially dry, dried, or calcined state, most preferably
the crystals of molecular sieve and solid particles of active metal
oxide are physically mixed in their calcined state to form the multi-component
molecular sieve catalyst composition of the invention. In another
embodiment, one or more active metal oxides or their precursors
are added to the synthesis mixture for making a molecular sieve
as described above and co-precipitated with the molecular sieve.
Alternatively the crystals of molecular sieve and active metal oxides
are mixed before drying.
[0072] Without being bound by any particular theory, it is believed
that intimate mixing of the molecular sieve, either as crystals
or as a molecular sieve catalyst composition, and one or more active
metal oxides improve conversion processes using the multi-component
molecular sieve catalyst composition of the invention. Intimate
mixing may be achieved by any method known in the art, such as mixing
with a mixer muller, drum mixer, ribbon/paddle blender, kneader,
or the like.
[0073] In one embodiment, the multi-component molecular sieve catalyst
composition has a weight ratio of the active metal oxide to the
molecular sieve in the range of from about 1:1000 to about 8:1
preferably in the range from about 1:100 to about 2:1 and more
preferably from about 1:50 to about 1:1.
[0074] In one embodiment, where the molecular sieve synthesized
above is formulated into a molecular sieve catalyst composition,
the active metal oxide is then combined with the formulated molecular
sieve catalyst composition. It is also an embodiment of the invention
that a first formulated molecular sieve catalyst composition is
combined with an active metal oxide, and the resulting multi-component
molecular sieve catalyst composition is then itself mixed with a
binder and/or matrix material which could then be formed into desired
shape and sized particles by well-known techniques such as spray
drying, pelletizing, extrusion, and the like.
[0075] Without being bound by any particular theory, the addition
of active metal oxides appears to have the effect of intercepting
coke precursors, thereby interrupting the coke formation process.
This effect is expected to allow the use of catalysts that may not
have previously been commercially viable for use in aromatics alkylation.
[0076] The beneficial effect of active metal oxides in extending
the lifetime of various catalyst compositions is expected to extend
to all microporous materials including, but not limited to, metal-containing
microporous materials, as well as to non-microporous materials such
as silica-alumina and amorphous acid catalysts.
[0077] Process For Using the Multi-Component Molecular Sieve Catalyst
Compositions
[0078] The molecular sieve compositions and catalyst compositions
described above are useful in a variety of processes including:
cracking, of for example a naphtha feed to one or more light olefins
or higher molecular weight (MW) hydrocarbons to lower MW hydrocarbons;
hydrocracking, of for example heavy petroleum and/or cyclic feedstock;
isomerization, of for example aromatics such as xylene; polymerization,
of for example one or more olefins to produce a polymer product;
reforming; hydrogenation; dehydrogenation; dewaxing, of for example
hydrocarbons to remove straight chain paraffins; absorption, of
for example alkyl aromatic compounds for separating out isomers
thereof; alkylation, of for example aromatic hydrocarbons such as
benzene and alkyl benzene, optionally with propylene to produce
cumene or with long chain olefins; transalkylation, of for example
a combination of aromatic and polyalkylaromatic hydrocarbons; dealkylation;
hydrodecylization; disproportionation, of for example toluene to
make benzene and para-xylene; oligomerization, of for example straight
and branched chain olefins; and dehydrocyclization.
[0079] The preferred process of the invention is a process directed
to the alkylation of a feedstock comprising one or more aromatic
hydrocarbons to one or more alkyl aromatics in the presence of an
alkylating agent. The most preferred process of the invention is
a process directed to the alkylation of a feedstock comprising toluene
to one or more xylene isomers, preferably predominantly para-xylene.
[0080] The term "aromatic" in reference to the alkylatable
compounds which are useful herein is to be understood in accordance
with its art-recognized scope which includes alkyl substituted and
unsubstituted mono- and polynuclear compounds. Compounds of an aromatic
character which possess a hetero atom are also useful provided they
do not act as catalyst poisons under the reaction conditions selected.
[0081] Substituted aromatic compounds which can be alkylated herein
must possess at least one hydrogen atom directly bonded to the aromatic
nucleus. The aromatic rings can be substituted with one or more
alkyl, aryl, alkaryl, alkoxy, aryloxy, cycloalkyl, halide, nitro,
sulfono, and/or other groups which do not interfere with the alkylation
reaction.
[0082] Suitable aromatic hydrocarbons include, but are not limited
to, benzene, toluene, xylene, naphthalene, anthracene, naphthacene,
perylene, coronene, and phenanthrene.
[0083] Generally the alkyl groups which can be present as substituents
on the aromatic compound contain from one to about 22 carbon atoms,
preferably from one to about eight carbon atoms, and most preferably
from one to about four carbon atoms.
[0084] Suitable alkyl substituted aromatic compounds include toluene,
xylene, isopropylbenzene, normal propylbenzene, alpha-methylnaphthalene,
ethylbenzene, cumene, mesitylene, durene, p-cyxene, butylbenzene,
pseudocumene, o-diethylbenzene, m-diethylbenzene, p-diethylbenzene,
isoamylbenzene, isohexylbenzene, pentaethylbenzene, pentamethylbenzene;
1234-tetraethylbenzene; 1235-tetramethylbenzene; 124-triethylbenzene;
123-trimethylbenzene, m-butyltoluene; p-butyltoluene; 35-diethyltoluene;
oethyltoluene; p-ethyltoluene; m-propyltoluene; 4-ethyl-m-xylene;
dimethylnaphthalenes; ethylnaphthalene; 23-dimethylanthracene;
9-ethylanthracene; 2-methylanthracene; o-methylanthracene; 910-dimethylphenanthrene;
and 3-methyl-phenanthrene. Higher molecular weight alkylaromatic
hydrocarbons can also be used as starting materials and include
aromatic bydrocarbons such as are produced by the alkylation of
aromatic hydrocarbons with olefin oligomers. Such products are frequently
referred to in the art as alkylate and include hexylbenzene, nonylbenzene,
dodecylbenzene, pentadecyclbenzene, hexyltoluene, nonyltoluene,
dodecyltoluene, pentadecytoluene, to name a few. Very often alkylate
is obtained as a high boiling fraction in which the alkyl group
attached to the aromatic nucleus varies in size from about C.sub.6
to about C.sub.12.
[0085] Reformate containing substantial quantities of benzene,
toluene, xylene and/or other alkylatable aromatic compounds also
constitutes a useful feed for the alkylation process of this invention.
[0086] The multi-component molecular sieve catalyst compositions
described above are particularly useful in alkylation processes
using oxygen and/or sulfur-containing alkylating agents. Suitable
alkylating agents include, but are not limited to, alcohols (such
as methanol, ethanol, and isopropanol), alcohol precursors (such
as syngas, preferably in combination with an alcohol synthesis catalyst),
ethers (such as dimethyl ether), esters, and carbonates (such as
dimethyl carbonate). Typically, an alkylating agent stream might
contain one or more aliphatic-containing compounds that include
alcohols, amines, carbonyl compounds (for example aldehydes, ketones,
and carboxylic acids), ethers, halides, mercaptans, sulfides, and
the like, and mixtures thereof. The aliphatic moiety of the aliphatic-containing
compounds typically contains from 1 to about 50 carbon atoms, preferably
from 1 to 20 carbon atoms, more preferably from 1 to 10 carbon atoms,
and most preferably from 1 to 4 carbon atoms. Non-limiting examples
of aliphatic-containing compounds include alcohols such as methanol
and ethanol; alkyl-mercaptans such as methyl mercaptan and ethyl
mercaptan; alkyl-sulfides such as methyl sulfide; alkyl-amines such
as methyl amine; alkylethers 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.
[0087] In a preferred embodiment of the process of the invention,
the alkylating agent contains one or more oxygenates, more specifically
one or more organic compounds containing at least one oxygen atom.
In the most preferred embodiment of the process of invention, the
oxygenate in the alkylating agent is one or more alcohols, preferably
aliphatic alcohols where the aliphatic moiety of the alcohols 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 alkylating agents in the process of the invention include lower
straight and branched chain aliphatic alcohols and their unsaturated
counterparts.
[0088] Non-limiting examples of oxygenates include methanol, ethanol,
n-propanol, isopropanol, methyl ethyl ether, dimethyl ether, diethyl
ether, diisopropyl ether, formaldehyde, dimethyl carbonate, dimethyl
ketone, acetic acid, and mixtures thereof. In a preferred embodiment,
the alkylating agent is selected from one or more of methanol, ethanol,
dimethyl ether, diethyl ether, or a combination thereof; more preferably
methanol and/or dimethyl ether; and most preferably methanol.
[0089] Non-limiting examples of alkylated aromatic hydrocarbons
include toluene, xylenes, ethylbenzene, propylbenzenes, butylbenzenes,
ethyltoluenes, diethylbenzenes, methylnapthlalenes, and dimethylnaphthalenes.
[0090] In one preferred embodiment, the molecular sieve is an aluminosilicate;
the active metal oxide is an active Group 4 metal oxide that has
been modified by a Group 2 Group 3 Lanthanide Series, and/or Actinide
Series metal oxide; and the alkylating agent is methanol. In a more
preferred embodiment, the molecular sieve is steamed ZSM-5 and the
active metal oxide is yttrium oxide or a co-precipitated combination
of lanthanum oxide with zirconium and/or hafnium oxide.
[0091] The feedstock, in one embodiment, contains one or more diluents,
typically used to reduce the concentration of the feedstock, which
are generally non-reactive to the feedstock or multi-component molecular
sieve catalyst composition. Non-limiting examples of diluents include
helium, argon, hydrogen, 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 diluent is used either in a
liquid or a vapor form, or a combination thereof and may be either
added directly to a feedstock entering into a reactor or added directly
into a reactor, either at the front end or in staged additions down
the length of the bed. The preferred diluents are hydrogen and water,
with hydrogen and water together being more preferred, and a homogenous
gas phase mixture of water and hydrogen being most preferred. Hydrogen
gas used as a diluent also acts as an anti-coking agent. Surprisingly,
the addition of water as a diluent in the reactor further enhances
the HLEI benefits seen with the use of multi-component molecular
sieve catalyst compositions. Preferably, hydrogen and/or added water
are present in a molar ratio between about 1:100 and about 10:1
with respect to total moles of the aromatic compound(s) and the
alkylating agent(s) combined (hereafter together referred to as
"reactants") and more preferably, hydrogen and water combined
are present in a molar ratio between about 1:1 and about 5:1 with
respect to the total moles of the reactants.
[0092] An alternative embodiment would include hydrogen and carbon
monoxide in the feedstock mixture and at least one component in
the catalyst that is capable of forming an alkylating agent, such
as methanol, from hydrogen and carbon monoxide. For the purposes
of this invention, the term "alkylating agent" will be
understood to include alkylating agents formed in such parallel
reactions whether or not the alkylating agent itself is part of
the feed to the reactor, and any hydrogen added for the purpose
of forming the alkylating agent would not be counted in the preferred
molar ratios of hydrogen to reactants as described above.
[0093] The process for alkylating aromatics, especially using an
alkylating agent comprising one or more oxygenates, in the presence
of a multi-component molecular sieve catalyst composition of the
invention, is carried out in a reactor system operating at conversion
conditions and containing at least one reactor, where the reactor
is a fixed bed reactor or a fluidized bed reactor (including a turbulent
bed reactor), preferably a fixed bed reactor. In a preferred embodiment,
a feedstock containing the alkylatable aromatic and an oxygen- or
sulfur-containing alkylation agent are introduced to a reactor system
containing a multi-component molecular sieve catalyst composition
and one or more alkylated aromatics are recovered from the effluent
exiting the reactor system.
[0094] This invention is applicable to a broad range of aromatic
alkylation processes, preferably those in which methanol reacts
with an aromatic compound, or mixture of aromatics, to add methyl
groups. The conversion of benzene to toluene, xylenes, and/or C.sub.9+
aromatics and the conversion of toluene to xylenes and/or C.sub.9+
aromatics are examples of aromatic methylation. In one embodiment,
the aromatic compound is a relatively pure compound, and in another
embodiment, the aromatic compound is contained in a mixture of aromatics
and non-aromatics, such as reformate. In the fuels area, methylation
of reformats or other C.sub.6-C.sub.7 streams could lower benzene
content as well as increase fuel yields and octane values. For fuels,
high selectivity to the para-isomer is not crucial, but para-selectivity
is desirable for chemicals applications.
[0095] It will be recognized by those skilled in the art that the
longer half-life of the multi-component molecular sieve catalyst
composition would generally either allow its use in existing reactors,
perhaps operating under modified reaction conditions, or allow the
use of less complex reactor designs for new equipment. Reactor design
is beyond the scope of this invention, but it will be recognized
by those skilled in the art that this multi-component molecular
sieve catalyst composition will allow a greater range of choices
in the design and/or retrofit of reactors to be used for aromatics
alkylation processes, and this invention is not limited to any particular
reactor configuration. For example, it is contemplated that plug
flow, fixed bed, or fluidized bed processes are used in combination,
particularly in different reaction zones within a single or multiple
reactor system.
[0096] The reaction temperature employed in the alkylation process,
specifically within the reactor system, is generally in the range
of from about 200.degree. C. to about 1000.degree. C., preferably
from about 250.degree. C. to about 700.degree. C., more preferably
from about 300.degree. C. to about 700.degree. C., yet more preferably
from about 350.degree. C. to about 650.degree. C., yet even more
preferably from about 400.degree. C. to about 600.degree. C., and
most preferably from about 500.degree. C. to about 580.degree. C.
[0097] The reaction pressure employed in the alkylation process,
specifically within the reactor system, varies over a wide range
including autogenous pressure. The conversion pressure is based
on the partial pressure of the feedstock exclusive of any diluent
therein. Typically the conversion pressure employed in the process
is in the range of from about 30 kPa to about 7 MPa, preferably
from about 100 kPa to about 3.5 MPa, and most preferably from about
150 kPa to about 900 kPa.
[0098] When the multi-component molecular sieve catalyst composition
does become coked, it can be regenerated using any regeneration
technique suitable for the materials included in the multi-component
molecular sieve catalyst as will be known to those skilled in the
art.
EXAMPLES
[0099] In order to provide a better understanding of the present
invention including representative advantages thereof, the following
examples are offered. Example 1 will describe the synthesis of the
mixed metal oxide for the multi-component catalysts. Example 2 (Comparative)
will demonstrate the performance of a ZSM-23 molecular sieve catalyst
composition and Example 3 will demonstrate the performance of the
multi-component molecular sieve catalyst composition containing
the ZSM-23 molecular sieve catalyst composition. Examples 4 and
5 6 and 7 and 9 and 10 respectively, will similarly provide comparisons
between molecular sieve catalyst compositions without an active
metal oxide and multi-component molecular sieve catalyst compositions
using the same type of molecular sieve catalyst composition physically
mixed by stirring with particles of an active metal oxide mixture.
Example 1
Preparation of Active Metal Oxide
[0100] Fifty grams of ZrOCl.sub.2.8H.sub.2O were dissolved with
stirring in 300 ml of distilled water. Another solution containing
4.2 grams of La(NO.sub.3).sub.3.6H.sub.2O and 300 ml of distilled
water was prepared. These two solutions were combined with stirring.
The pH of the final mixture was adjusted to approximately 9 by the
addition of concentrated ammonium hydroxide (28.9 grams). This slurry
was then put in polypropylene bottles and placed in a steam box
(100.degree. C.) for 72 hours. The product formed was recovered
by filtration, washed with excess water, and dried overnight at
85.degree. C. A portion of this product was calcined to 700.degree.
C. in flowing air for 3 hours to produce a mixed metal oxide (La.sub.xO.sub.y/ZrO.sub.2)
containing a nominal 5 weight percent lanthanum based on the final
weight of the mixed metal oxide.
[0101] For Examples 2 through 10 catalyst performance data were
obtained using a downflow fixed-bed reactor with the following operating
conditions, unless otherwise noted:
[0102] Temperature=500.degree. C.
[0103] Pressure=100 kPa
[0104] H.sub.2 to reactants molar ratio=0.8
[0105] Pure methanol and toluene feeds at 1:3 molar ratio
[0106] WHSV=3.9 h.sup.-1 based on molecular sieve catalyst composition
[0107] Catalyst load=2.0 g of molecular sieve catalyst composition
for all tests
[0108] For the 1:3 molar feed mixture, the maximum toluene conversion
expected from reaction with methanol would be about 33%. Methanol
utilization is reported as (moles of methanol converted)/(moles
of xylene formed--moles of benzene formed). Benzene is subtracted
to account for any xylene formed by the disproportionation of toluene
to xylene plus benzene.
[0109] For the multi-component molecular sieve catalyst compositions,
a physical mixture of 2.0 g of the molecular sieve catalyst composition
and 0.4 g of the mixed metal oxide was used. The toluene and methanol
weight hourly space velocities were kept constant relative to the
amount of molecular sieve catalyst composition in the bed.
[0110] Example 2 (Comparative)
[0111] The reaction described above was run using a molecular sieve
catalyst composition containing 65 weight percent ZSM-23 molecular
sieve (further described in U.S. Pat. No. 4076842) with a Si/Al.sub.2
ratio about 100 which had been bound with an alumina-rich binder
constituting 35 weight percent of the composition. The catalyst
load was 2.0 g. The resulting toluene conversion, para-xylene selectivity,
and methanol utilization at 2 20 40 60 and 80 hours are shown
in Table 2.
Example 3
[0112] This example used the same reaction conditions as Example
2 but 0.4 g of the La.sub.xO.sub.y/ZrO.sub.2 product from Example
1 was added to 2.0 g of the ZSM-23 molecular sieve catalyst composition
(as described in Example 2) as a physical mixture of particles to
form a multi-component molecular sieve catalyst composition. The
catalytic performance of the multi-component molecular sieve catalyst
composition (ZSM-23 with La.sub.xO.sub.y/ZrO.sub.2) at 2 20 40
and 170 hours is also shown in Table 2.
[0113] The data show that addition of La.sub.xO.sub.y/ZrO.sub.2
to the aluminosilicate catalyst bed improved the catalyst activity,
selectivity to para-xylene (which increased steadily with time to
about 68% at the end of the test), and the catalyst life. The multi-component
molecular sieve catalyst composition containing La.sub.xO.sub.y/ZrO.sub.2
maintained approximately constant toluene conversion activity for
170 hrs, while the molecular sieve catalyst composition activity
in Example 2 dropped to approximately half the initial toluene conversion
after 27 hours and approximately zero at 80 hours. The HLEI in this
test was greater than 6.3 and has not been extrapolated to the
time at which toluene conversion by the multi-component molecular
sieve composition would have dropped to half of its initial value.
Example 4 (Comparative)
[0114] An alumina-bound ZSM-5 catalyst composition that had been
treated with silicone three times, with calcination after each silicone
treatment, and steamed for 24 hours at 10001.degree. F. was tested
at the same conditions as Example 2 to provide a comparison case
for this molecular sieve catalyst composition.
Example 5
[0115] Two grams of the same catalyst composition as described
in Example 4 was mixed with 0.4 grams of the La.sub.xO.sub.y/ZrO.sub.2
of Example 1 and tested at the same conditions as Example 3. The
results for Examples 4 and 5 at 2 20 60 and 106 hours are shown
in Table 2. The toluene conversion for the molecular sieve catalyst
composition in Example 4 (silicone-treated ZSM-5) dropped to approximately
half of the initial conversion rate after about 63 hours, while
the toluene conversion for the multi-component molecular sieve catalyst
composition stayed roughly constant at about 15% for over 106 hours,
indicating that the HLEI in this comparison is greater than 1.7.
Methanol utilization and para-xylene selectivity were also higher
for the multi-component molecular sieve catalyst composition.
Example 6 (Comparative)
[0116] A molecular sieve catalyst composition with 25 weight percent
ZSM-5 molecular sieve crystals having a Si/Al.sub.2 ratio of 450
was spray dried with 5 weight percent phosphorus and clay and then
steamed at 1090.degree. C. to produce steamed ZSM-5. This molecular
sieve catalyst composition was run in a fixed bed downflow reactor
at a temperature of 585.degree. C., a pressure of 280 kPa, an H.sub.2
to reactants molar ratio of 2:1 with pure methanol and toluene
feeds at a 1:2 molar ratio, an H.sub.2O to reactants molar ratio
of 2:1 and a WHSV of 8 h.sup.-1. The catalyst load was 2.0 g. Catalyst
performance data for 2 10 20 and 30 hours are shown in Table
2.
Example 7
[0117] The same temperature, pressure, and flow rates were maintained
as in Example 6 but 0.4 g of the La.sub.xO.sub.y/ZrO.sub.2 material
of Example 1 was added to 2.0 g of the comparison molecular sieve
catalyst composition described in Example 6 as a physical mixture
of particles. The catalytic performance of the molecular sieve catalyst
composition comparative sample and of the multi-component molecular
sieve catalyst composition are shown in Table 2.
[0118] The data show that addition of La.sub.xO.sub.y/ZrO.sub.2
to the aluminosilicate catalyst bed improved toluene conversion,
methanol utilization, and catalyst life. The multi component molecular
sieve catalyst composition containing La.sub.xO.sub.y/ZrO.sub.2
maintained approximately constant toluene conversion for 170 hours,
at which point the H.sub.2O co-feed was discontinued in an effort
to cause the catalyst to require regeneration. Even so, the toluene
conversion had not yet dropped to 50% of the initial conversion
rate at 300 hours. In contrast, the performance of the molecular
sieve catalyst composition alone (Example 6) dropped to very low
toluene conversion over a period of 30 hours, reaching 50% of the
initial toluene conversion at approximately 7.5 hours. Again, not
extrapolating the half-life of the multi-component molecular sieve
catalyst composition beyond the time tested, the HLEI is greater
than 22.7. It should be noted that although the initial data points
for these two examples were reported for different times, the HLEI
would by inspection still have been 20 or more had those data points
been taken at the same run time.
Example 8
[0119] The multi-component molecular sieve catalyst composition
used in Example 7 was run for 380 hours, with the water pump shut
down at 170 hours to speed de-activation, then regenerated in-situ
at 530.degree. C. with air flow of 100 cc/min for 10 hours. The
regenerated multi-component molecular sieve catalyst composition's
performance at the same reaction conditions as were used in Examples
6 and 7 shows that this multi-component molecular sieve catalyst
composition is regenerable After 280 hours on-stream the toluene
conversion was 20%, methanol utilization was 50%, and para-xylene
selectivity was 91%.
Example 9 (Comparative)
[0120] An alumina-bound ZSM-48 catalyst which had been treated
with silicone three times, with calcination after each silicone
treatment, and steamed for 24 hrs at 1000.degree. F., was run at
the same conditions as Example 2 to provide a comparison case for
this catalyst composition.
Example 10
[0121] Two grams of the catalyst described in Example 9 were mixed
with 0.4 grams of the La.sub.xO.sub.y/ZrO.sub.2 of Example 1 and
run at the same conditions as Example 3. The results for Examples
9 and 10 are shown in Table 2. The toluene conversion for the silicone-treated
ZSM-48 dropped below 50% of its initial rate at about 12 hours on
stream, while for the mixed catalyst toluene conversion was approaching
50% of its initial rate when the test ended at 60 hours, resulting
in a HLEI greater than 5.0. |