Molecular sieve abstract
The invention relates to a molecular sieve catalyst composition,
to a method of making or forming the molecular sieve catalyst composition,
and to a conversion process using the catalyst composition. In particular,
the invention is directed to a catalyst composition comprising a
molecular sieve having a framework including at least [AlO.sub.4]
and [PO.sub.4] tetrahedral units, at least one of a binder and a
matrix material and at least one phosphorus compound separate from
said molecular sieve wherein, after calcination at 760.degree. C.
for 3 hours, said catalyst composition has a microporous surface
area in excess of 20% of the microporous surface area of said molecular
sieve after calcination at 650.degree. C. in nitrogen for 2 hours.
The catalyst composition is particularly useful in a conversion
process for producing olefin(s), preferably ethylene and/or propylene,
from a feedstock, preferably an oxygenate containing feedstock.
Molecular sieve claims
We claim:
1. A catalyst composition comprising a molecular sieve having a
framework including at least [AlO.sub.4] and [PO.sub.4] tetrahedral
units, at least one of a binder and a matrix material and at least
one phosphorus compound separate from said molecular sieve wherein,
after calcination at 760.degree. C. for 3 hours, said catalyst composition
has a microporous surface area in excess of 20% of the microporous
surface area of said molecular sieve after calcination at 650.degree.
C. in nitrogen for 2 hours.
2. The catalyst composition of claim 1 wherein, after calcination
at 760.degree. C. for 3 hours, said catalyst composition has a microporous
surface area in excess of 50% of the microporous surface area of
said molecular sieve after calcination at 650.degree. C. in nitrogen
for 2 hours.
3. The catalyst composition of claim 1 wherein, after calcination
at 760.degree. C. for 3 hours, said catalyst composition has a microporous
surface area in excess of 100% of the microporous surface area of
said molecular sieve after calcination at 650.degree. C. in nitrogen
for 2 hours.
4. The catalyst composition of claim 1 wherein said phosphorus
compound is present in amount of between about 0.05 and about 15
wt %, expressed as P.sub.2O.sub.5 by weight of the catalyst composition.
5. The catalyst composition of claim 1 wherein said phosphorus
compound is present in amount of between about 0.1 and about 10
wt %, expressed as P.sub.2O.sub.5 by weight of the catalyst composition.
6. The catalyst composition of claim 1 wherein said phosphorus
compound is present in amount of between about 0.5 and about 6 wt
%, expressed as P.sub.2O.sub.5 by weight of the catalyst composition.
7. The catalyst composition of claim 1 wherein said phosphorus
compound is present in amount of between greater 1.0 and about 5
wt %, expressed as P.sub.2O.sub.5 by weight of the catalyst composition.
8. The catalyst composition of claim 1 and having an Attrition
Rate Index (ARI), of less than 3 wt % per hour.
9. The catalyst composition of claim 1 and having an Attrition
Rate Index (ARI), of less than 0.95 wt % per hour.
10. The catalyst composition of claim 1 and having an Attrition
Rate Index (ARI), of about 0.05 to about 0.8 wt % per hour.
11. The catalyst composition of claim 1 wherein, after hydrothermal
treatment at 800.degree. C. for 18 hours at a water vapor pressure
of 45 psig, said catalyst composition retains at least 15% of the
methanol conversion activity of the untreated catalyst composition.
12. The catalyst composition of claim 1 and including a binder
comprising alumina.
13. The catalyst composition of claim 12 and further including
a matrix material comprising a clay.
14. The catalyst composition of claim 1 wherein the molecular sieve
is selected from aluminophosphates, silicoaluminophosphates and
metal-containing derivatives thereof.
15. The catalyst composition of claim 14 wherein the molecular
sieve comprises a CHA framework-type molecular sieve.
16. The catalyst composition of claim 15 wherein the molecular
sieve further comprises an AEI framework-type molecular sieve.
17. A catalyst composition comprising a molecular sieve having
a framework including at least [AlO.sub.4] and [PO.sub.4] tetrahedral
units, at least one of a binder and a matrix material and at least
one phosphorus compound separate from said molecular sieve wherein,
after hydrothermal treatment at 800.degree. C. for 18 hours at a
water vapor pressure of 45 psig, said catalyst composition retains
at least 15% of the methanol conversion activity of the untreated
catalyst composition.
18. The catalyst composition of claim 17 wherein, after hydrothermal
treatment at 800.degree. C. for 18 hours at a water vapor pressure
of 45 psig, said catalyst composition retains at least 20% of the
methanol conversion activity of the untreated catalyst composition.
19. The catalyst composition of claim 17 wherein, after hydrothermal
treatment at 800.degree. C. for 18 hours at a water vapor pressure
of 45 psig, said catalyst composition retains at least 25% of the
methanol conversion activity of the untreated catalyst composition.
20. The catalyst composition of claim 17 wherein said phosphorus
compound is present in amount of between about 0.05 to about 15
wt %, expressed as P.sub.2O.sub.5 by weight of the catalyst composition.
21. The catalyst composition of claim 17 wherein said phosphorus
compound is present in amount of between about 0.1 to about 10 wt
%, expressed as P.sub.2O.sub.5 by weight of the catalyst composition.
22. The catalyst composition of claim 17 and having an Attrition
Rate Index (ARI), of less than 0.95 wt % per hour.
23. The catalyst composition of claim 17 and including a binder
comprising alumina.
24. The catalyst composition of claim 23 and further including
a matrix material comprising a clay.
25. The catalyst composition of claim 17 wherein the molecular
sieve is selected from aluminophosphates, silicoaluminophosphates
and metal-containing derivatives thereof.
26. The catalyst composition of claim 25 wherein the molecular
sieve comprises a CHA framework-type molecular sieve.
27. The catalyst composition of claim 26 wherein the molecular
sieve further comprises an AEI framework-type molecular sieve.
28. A method for making a catalyst composition, the method comprising
(a) forming a slurry comprising a binder or binder precursor and
a molecular sieve, the slurry being substantially free of any phosphorus
compounds except as may be present in said molecular sieve; (b)
mixing a phosphorus compound with said slurry to produce a phosphorus-containing
mixture; (c) adding a matrix to the phosphorus-containing mixture
to produce a catalyst precursor mixture, (d) spray drying the catalyst
precursor mixture to produce particles of said catalyst composition,
and then (e) calcining said catalyst composition particles.
29. The method of claim 28 wherein said phosphorus compound is
selected from phosphoric acid, ammonium phosphate, ammonium hydrogen
phosphate, ammonium dihydrogen phosphate, phosphorous acid, ammonium
hydrogen phosphite, ammonium phosphite; hyprophosphorous acid, ammonium
phosphinate, di- and polyacids of phosphorus and their ammonium
and ammonium hydrogen salts, pyrophosphates and their ammonium salts,
tripolyphosphates and their ammonium salts, metaphosphates and their
ammonium salts and mixtures thereof.
30. The method of claim 28 wherein the amount of said phosphorus
compound mixed in (b) is such that the catalyst composition contains
between about 0.05 to about 15 wt % of phosphorus, expressed as
P.sub.2O.sub.5 by weight of the catalyst composition.
31. The method of claim 28 wherein said slurry (a) is formed by
mixing said binder with an as-synthesized molecular sieve which
has not been fully dried.
32. The method of claim 30 wherein said as-synthesized molecular
sieve which has not been fully dried contains up to 70 wt % of water.
33. The method of claim 28 wherein said catalyst precursor mixture
contains in the range of from about 25 weight percent to about 55
weight percent solid particles.
34. The method of claim 28 wherein said catalyst precursor mixture
contains from about 20 to about 90 weight percent of the molecular
sieve, from about 3 to about 25 weight percent of the binder or
binder precursor and from about 5 to about 85 weight percent of
the matrix material.
35. The method of claim 28 wherein at least 90 percent by volume
of the solid particles in said catalyst precursor mixture have a
diameter of less than 20 .mu.m.
36. The method of claim 28 wherein said binder precursor is an
alumina sol.
37. The method of claim 28 wherein said matrix material is a clay.
38. The method of claim 28 wherein said molecular sieve has a framework
including at least [AlO.sub.4] and [PO.sub.4] tetrahedral units.
39. The catalyst composition of claim 28 wherein the molecular
sieve comprises a silicoaluminophosphate.
40. The catalyst composition of claim 39 wherein the molecular
sieve comprises a CHA framework-type molecular sieve.
41. The method of claim 28 wherein the calcining of (e) is conducted
at a temperature of 600 to 800.degree. C.
42. A method of making a catalyst composition, the method comprising:
(i) synthesizing a molecular sieve from an aqueous reaction mixture
comprising at least one templating agent and at least two of a silicon
source, a phosphorus source and an aluminum source; and (ii) recovering
the molecular sieve synthesized in (i); (iii) mixing the molecular
sieve recovered in (ii) with a binder or binder precursor to form
a slurry; (iv) mixing a phosphorus compound with said slurry to
produce a phosphorus-containing mixture; (v) adding a matrix to
the phosphorus-containing mixture to produce a catalyst precursor,
(vi) spray drying the catalyst precursor to produce particles of
said catalyst composition, and then (vii) calcining said catalyst
composition particles
43. The method of claim 42 wherein the molecular sieve is mixed
with the binder or binder precursor before any drying the molecular
sieve recovered in (ii).
44. The method of claim 42 wherein the molecular sieve is mixed
with the binder or binder precursor before complete drying the molecular
sieve recovered in (ii).
45. The method of claim 42 wherein the molecular sieve mixed with
the binder or binder precursor in (iii) contains up to 70 wt % of
water.
46. The method of claim 42 wherein said catalyst precursor mixture
contains in the range of from about 25 weight percent to about 55
weight percent solid particles.
47. The method of claim 42 wherein said catalyst precursor mixture
contains from about 20 to about 90 weight percent of the molecular
sieve, from about 3 to about 25 weight percent of the binder or
binder precursor and from about 5 to about 85 weight percent of
the matrix material.
48. The method of claim 42 wherein at least 90 percent by volume
of the solid particles in said catalyst precursor mixture have a
diameter of less than 20 .mu.m.
49. The method of claim 42 wherein said binder precursor is an
alumina sol.
50. The method of claim 42 wherein said matrix material is a clay.
51. The method of claim 42 wherein said phosphorus compound is
selected from phosphoric acid, ammonium phosphate, ammonium hydrogen
phosphate, ammonium dihydrogen phosphate, phosphorous acid, ammonium
hydrogen phosphite, ammonium phosphite; hyprophosphorous acid, ammonium
phosphinate, di- and polyacids of phosphorus and their ammonium
and ammonium hydrogen salts, pyrophosphates and their ammonium salts,
tripolyphosphates and their ammonium salts, metaphosphates and their
ammonium salts and mixtures thereof.
52. The method of claim 42 wherein the amount of said phosphorus
compound mixed in (iv) is such that the catalyst composition contains
between about 0.05 to about 15 wt % of phosphorus, expressed as
P.sub.2O.sub.5 by weight of the catalyst composition.
53. The method of claim 42 wherein said molecular sieve has a framework
including at least [AlO.sub.4] and [PO.sub.4] tetrahedral units.
54. The catalyst composition of claim 42 wherein the molecular
sieve comprises a silicoaluminophosphate.
55. The catalyst composition of claim 54 wherein the molecular
sieve comprises a CHA framework-type molecular sieve.
56. The method of claim 42 wherein the calcining of (e) is conducted
at a temperature of 600 to 800.degree. C.
57. A process for converting a feedstock into one or more olefin(s)
in the presence of a catalyst composition comprising a molecular
sieve having a framework including at least [AlO.sub.4] and [PO.sub.4]
tetrahedral units, at least one of a binder and a matrix material
and at least one phosphorus compound separate from said molecular
sieve wherein, after calcination at 760.degree. C. for 3 hours,
said catalyst composition has a microporous surface area in excess
of 20% of the microporous surface area of said molecular sieve after
calcination at 650.degree. C. in nitrogen for 2 hours.
58. The process of claim 57 wherein said phosphorus compound is
present in amount of between about 0.05 to about 10 wt %, expressed
as P.sub.2O.sub.5 by weight of the catalyst composition.
59. The process of claim 57 wherein said phosphorus compound is
present in amount of between greater 1.0 to about 5 wt %, expressed
as P.sub.2O.sub.5 by weight of the catalyst composition.
60. The process of claim 57 wherein said catalyst composition includes
a binder comprising alumina.
61. The process of claim 57 wherein said catalyst composition includes
a matrix material comprising a clay.
62. The process of claim 57 wherein the molecular sieve is selected
from aluminophosphates, silicoaluminophosphates and metal-containing
derivatives thereof.
63. The process of claim 62 wherein the molecular sieve comprises
a CHA framework-type molecular sieve.
64. The process of claim 63 wherein the molecular sieve further
comprises an AEI framework-type molecular sieve.
65. The process of claim 57 wherein the feedstock comprises methanol
and, after hydrothermal treatment at 800.degree. C. for 18 hours
at a water vapor pressure of 45 psig, said catalyst composition
retains at least 15% of the methanol conversion activity of the
untreated catalyst composition.
66. A process for converting feedstock into one or more olefin(s)
in the presence of the catalyst composition prepared by the method
of claim 28.
67. A process for converting feedstock into one or more olefin(s)
in the presence of the catalyst composition prepared by the method
of claim 42.
68. An integrated process for making one or more olefin(s), the
integrated process comprising: (a) passing a hydrocarbon feedstock
to a syngas production zone to producing a synthesis gas stream;
(b) contacting the synthesis gas stream with a catalyst to form
an oxygenated feedstock; and (c) converting the oxygenated feedstock
into the one or more olefin(s) in the presence of a catalyst composition
comprising a molecular sieve having a framework including at least
[AlO.sub.4] and [PO.sub.4] tetrahedral units and at least one phosphorus
compound separate from said molecular sieve.
69. The integrated process of claim 68 wherein the process further
comprises (d) polymerizing the one or more olefin(s) in the presence
of a polymerization catalyst into a polyolefin.
70. The integrated process of claim 68 wherein the oxygenated feedstock
comprises methanol, the olefin(s) include ethylene and propylene,
and the molecular sieve catalyst composition is a silicoaluminophosphate
molecular sieve.
Molecular sieve description
FIELD
[0001] The present invention relates to a molecular sieve catalyst
composition, to a method of producing the catalyst composition,
and to the use of catalyst composition 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).
The preferred alcohol for light olefin production is methanol and
the preferred process for converting a methanol-containing feedstock
into light olefin(s), primarily ethylene and/or propylene, involves
contacting the feedstock with a molecular sieve catalyst composition.
[0004] There are many different types of molecular sieves well
known to convert a feedstock, especially an oxygenate containing
feedstock, into one or more olefin(s). For example, U.S. Pat. No.
5367100 describes the use of the well known zeolite, ZSM-5 to
convert methanol into olefin(s); U.S. Pat. No. 4062905 discusses
the conversion of methanol and other oxygenates to ethylene and
propylene using crystalline aluminosilicate zeolites, for example
Zeolite T, ZK5 erionite and chabazite; U.S. Pat. No. 4079095
describes the use of ZSM-34 to convert methanol to hydrocarbon products
such as ethylene and propylene; and U.S. Pat. No. 4310440 describes
producing light olefin(s) from an alcohol using a crystalline aluminophosphate.
[0005] One of the most useful molecular sieves for converting methanol
to olefin(s) are silicoaluminophosphate molecular sieves. Silicoaluminophosphate
(SAPO) molecular sieves contain a three-dimensional microporous
crystalline framework structure of [SiO.sub.2], [AlO.sub.2] and
[PO.sub.2] corner sharing tetrahedral units. SAPO synthesis is described
in U.S. Pat. No. 4440871 which is herein fully incorporated by
reference. SAPO 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, is shown
in U.S. Pat. Nos. 4499327 4677242 4677243 4873390 5095163
5714662 and 6166282 all of which are herein fully incorporated
by reference.
[0006] When used in the conversion of methanol to olefins, most
molecular sieves, including SAPO molecular sieves, undergo rapid
coking and hence require frequent regeneration, typically involving
exposure of the catalyst to high temperatures and steaming environments.
Moreover, these processes are typically conducted in a fluidized
bed reactor where the catalyst is continuously circulated between
a reaction zone and a regeneration zone. This continuous circulation
necessarily results in collisions between the catalyst composition
particles themselves and with the reactor walls which can cause
the particles to breakdown into smaller particles called fines.
This physical breakdown of catalyst particles is known as attrition
and is undesirable because the fines often exit the reactor in the
effluent stream resulting not only in catalyst losses but also in
problems in downstream recovery systems.
[0007] There is therefore a need for a molecular sieve catalyst
composition which can be used in the conversion of feedstocks, such
as oxygenates, to olefins and which exhibits both a high thermal
and hydrothermal stability and a high attrition resistance.
[0008] U.S. Pat. No. 6153552 discloses that the attrition resistance
of a SAPO catalyst can be enhanced by the addition of an external
phosphorus source in an amount between 0.1 and 25 wt %, preferably
between 1 and 20 wt %, of the finished catalyst. The external phosphorus
source is typically a phosphate and is added by mixing with the
molecular sieve, an inorganic oxide sol and a clay to form a slurry
which is then spray dried. However, the Examples show that, after
calcination at 760.degree. C. for 3 hours, the attrition resistance
of the catalyst decreases significantly and its surface area falls
dramatically.
[0009] U.S. Pat. No. 5110776 discloses a method of preparing
a catalytic cracking catalyst comprising treating a zeolite, such
as REY, with an aqueous phosphate solution, combining the resultant
aqueous mixture with a matrix precursor, such as alumina, and then
spray drying the resultant slurry. The catalyst is reported to have
improved attrition resistance and octane when used in catalytic
cracking.
[0010] U.S. Pat. No. 4987110 discloses that an attrition resistant
catalytic cracking catalyst can be prepared by spray drying a slurry
formed by combining a molecular sieve, which can be a zeolite or
a SAPO, with a clay, a silica sol and aluminum chlorohydroxide.
[0011] U.S. Patent Application Publication No. 2002/0049133 discloses
that an attrition resistant catalytic cracking catalyst can be prepared
by forming a slurry of a zeolite having a constraint index of 1
to 12 such as ZSM-5 a phosphorus-containing compound and alumina
in an amount less than 10 wt % of the slurry and then spray drying
and calcining the slurry.
SUMMARY
[0012] In one aspect, the present invention resides in a catalyst
composition comprising a molecular sieve having a framework including
at least [AlO.sub.4] and [PO.sub.4] tetrahedral units, at least
one of a binder and a matrix material and at least one phosphorus
compound separate from said molecular sieve wherein, after calcination
at 760.degree. C. in nitrogen for 3 hours, said catalyst composition
has a microporous surface area in excess of 20%, such as in excess
of 50%, of the microporous surface area of said molecular sieve
after calcination at 650.degree. C. in nitrogen for 2 hours.
[0013] Conveniently, said phosphorus compound is present in amount
of between about 0.05 and about 15 wt %, for example between about
0.1 and about 10 wt %, such as between greater 1.0 and about 5 wt
%, expressed as P.sub.2O.sub.5 by weight of the catalyst composition.
[0014] In one embodiment, the catalyst composition has an Attrition
Rate Index (ARI), of less than 3 wt % per hour, such as less than
0.95 wt % per hour, for example about 0.05 to about 0.8 wt % per
hour.
[0015] Conveniently, the catalyst composition includes a binder,
such as an alumina sol, and a matrix material, such as a clay.
[0016] Typically, the molecular sieve is an aluminophosphate or
a silicoaluminophosphate.
[0017] In another aspect, the invention resides in a catalyst composition
comprising a molecular sieve having a framework including at least
[AlO.sub.4] and [PO.sub.4] tetrahedral units, at least one of a
binder and a matrix material and at least one phosphorus compound
separate from said molecular sieve wherein, after hydrothermal treatment
at 800.degree. C. for 18 hours at a water vapor pressure of 45 psig,
said catalyst composition retains at least 15% of the methanol conversion
activity of the untreated catalyst composition.
[0018] In a further aspect, the invention resides in a method for
making a catalyst composition, the method comprising
[0019] (a) forming a slurry comprising a binder or binder precursor
and a molecular sieve in a liquid medium, the slurry being substantially
free of any phosphorus compounds except as may be present in said
molecular sieve;
[0020] (b) mixing a phosphorus compound with said slurry to produce
a phosphorus-containing mixture;
[0021] (c) adding a matrix to the phosphorus-containing mixture
to produce a catalyst precursor mixture,
[0022] (d) spray drying the catalyst precursor mixture to produce
particles of said catalyst composition, and then
[0023] (e) calcining said catalyst composition particles
[0024] Conveniently, said phosphorus compound is an inorganic phosphorus
compound and typically is selected from phosphoric acid, ammonium
phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate,
phosphorous acid, ammonium hydrogen phosphite, ammonium phosphite;
hyprophosphorous acid, ammonium phosphinate, di- and polyacids of
phosphorus and their ammonium and ammonium hydrogen salts, pyrophosphates
and their ammonium salts, tripolyphosphates and their ammonium salts,
metaphosphates and their ammonium salts and mixtures thereof.
[0025] In one embodiment, the slurry (a) is formed by mixing said
binder with an as-synthesized molecular sieve which has not been
fully dried.
[0026] In yet a further aspect, the invention resides in a method
of making a catalyst composition, the method comprising:
[0027] (i) synthesizing a molecular sieve from an aqueous reaction
mixture comprising at least one templating agent and at least two
of a silicon source, a phosphorus source and an aluminum source;
and
[0028] (ii) recovering the molecular sieve synthesized in (i);
[0029] (iii) mixing the molecular sieve recovered in (ii) with
a binder or binder precursor and a liquid medium to form a slurry;
[0030] (iv) mixing a phosphorus compound with said slurry to produce
a phosphorus-containing mixture;
[0031] (v) adding a matrix to the phosphorus-containing mixture
to produce a catalyst precursor mixture,
[0032] (vi) spray drying the catalyst precursor mixture to produce
particles of said catalyst composition, and then
[0033] (vii) calcining said catalyst composition particles
[0034] In one embodiment, the molecular sieve recovered in (ii)
is mixed with the binder or binder precursor without being fully
dried.
[0035] In still a further aspect, the invention resides in a process
for converting a feedstock, preferably a feedstock containing an
oxygenate, more preferably a feedstock containing an alcohol, and
most preferably a feedstock containing methanol, into one or more
olefin(s) in the presence of a catalyst composition as described
above or as produced by the methods described above.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Introduction
[0036] The invention is directed to a catalyst composition comprising
a molecular sieve having a framework including at least [AlO.sub.4]
and [PO.sub.4] tetrahedral units, such as an aluminophosphate or
a silicoaluminophosphate, to a method of making such a catalyst
composition and to the use of such a catalyst composition in the
conversion of hydrocarbon feedstocks, particularly oxygenated feedstocks,
into olefin(s). It has been found that the addition of a small amount
of an external phosphorus compound, typically an inorganic phosphorus
compound, during formulation of such a catalyst composition can
enhance both the hydrothermal stability and the attrition resistance
of the catalyst composition, particularly when used in the conversion
of hydrocarbon feedstocks, particularly oxygenated feedstocks, into
olefin(s). Moreover, it has been found that these improvements in
hydrothermal stability and attrition resistance can be achieved
without the dramatic decrease in the surface area of catalyst composition
reported in U.S. Pat. No. 6153552.
[0037] Thus, in one embodiment, in a test involving calcination
of the catalyst composition at 760.degree. C. in nitrogen at atmospheric
pressure for 3 hours, the present catalyst composition has a microporous
surface area in excess of 20%, such as in excess of 50%, conveniently
in excess of 75%, and even in excess of 100%, of the microporous
surface area of said molecular sieve after calcination at 650.degree.
C. in nitrogen at atmospheric pressure for 2 hours.
[0038] In another embodiment, after hydrothermal treatment at 800.degree.
C. for 18 hours at a water vapor pressure of 45 psig, the catalyst
composition retains at least 15% of the methanol conversion activity
of the untreated catalyst composition.
[0039] In yet another embodiment, the catalyst composition has
an attrition rate, as defined by its Attrition Rate Index (ARI),
of less than 3 wt % per hour, such as less than 0.95 wt % per hour,
for example about 0.05 to about 0.8 wt % per hour.
[0040] In addition it has been found that addition of the phosphorus
compound can allow a reduction the amount of binder used in formulating
the catalyst composition; which is desirable since high binder loadings
may result in reduced access to the micropores of the molecular
sieve.
[0041] The phosphorus compound is introduced into the catalyst
composition during formulation by making a slurry of the molecular
sieve and a binder or binder precursor, such as aluminum chlorohydrate,
in a liquid medium, such as water, and then adding the phosphorus
compound to the slurry. After addition of the phosphorus compound,
a matrix material, such as a clay, may be added to the slurry and
the resultant mixture can then be formed into the desired catalyst
particles, such as by spray drying. The resultant catalyst composition
can then be calcined.
[0042] In one embodiment, phosphorus compound is added to a slurry
of a binder or binder precursor and an as-synthesized molecular
sieve which has not been fully dried, such as the wet filter cake
obtained when an as-synthesized molecular sieve is separated by
filtration from the crystallization medium used in synthesizing
the sieve.
[0043] Molecular Sieve
[0044] Molecular sieves have various chemical, physical, and framework
characteristics. Molecular sieves have been well classified by the
Structure Commission of the International Zeolite Association according
to the rules of the IUPAC Commission on Zeolite Nomenclature. A
framework-type describes the topology and connectivity of the tetrahedrally
coordinated atoms constituting the framework, and makes an abstraction
of the specific properties for those materials. Framework-type zeolite
and zeolite-type molecular sieves for which a structure has been
established, are assigned a three letter code and are described
in the Atlas of Zeolite Framework Types, 5th edition, Elsevier,
London, England (2001), which is herein fully incorporated by reference.
[0045] Crystalline molecular sieve materials all have a 3-dimensional,
four-connected framework structure of corner-sharing TO.sub.4 tetrahedra,
where T is any tetrahedrally coordinated cation. Molecular sieves
are typically described in terms of the size of the ring that defines
a pore, where the size is based on the number of T atoms in the
ring. Other framework-type characteristics include the arrangement
of rings that form a cage, and when present, the dimension of channels,
and the spaces between the cages. See van Bekkum, et al., Introduction
to Zeolite Science and Practice, Second Completely Revised and Expanded
Edition, Volume 137 pages 1-67 Elsevier Science, B.V., Amsterdam,
Netherlands (2001).
[0046] 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, 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.
[0047] The small, medium and large pore molecular sieves have from
a 4-ring to a 12-ring or greater framework-type. Typically, the
molecular sieves employed herein have 8-, 10- or 12-ring structures
and an average pore size in the range of from about 3 .ANG. to 15
.ANG.. More typically, the molecular sieves, preferably silicoaluminophosphate
molecular sieves, have 8-rings and an average pore size less than
about 5 .ANG., such as in the range of from 3 .ANG. to about 5 .ANG.,
for example from 3 .ANG. to about 4.5 .ANG., and particularly from
3.5 .ANG. to about 4.2 .ANG..
[0048] Molecular sieves used herein have a molecular framework
including at least [AlO.sub.4] and [PO.sub.4] tetrahedral units,
such as aluminophosphates (AlPO), and typically including at least
[AlO.sub.4] and [PO.sub.4] and [SiO.sub.4] tetrahedral units, such
as silicoaluminophosphates (SAPO). These silicon, aluminum, and
phosphorus based molecular sieves and metal-containing derivatives
thereof have been described in detail in numerous publications including
for example, U.S. Pat. No. 4567029 (MeAPO where Me is Mg, Mn,
Zn, or Co), U.S. Pat. No. 4440871 (SAPO), European Patent Application
EP-A-0 159 624 (ELAPSO where El is As, Be, B, Cr, Co, Ga, Ge, Fe,
Li, Mg, Mn, Ti or Zn), U.S. Pat. No. 4554143 (FeAPO), U.S. Pat.
Nos. 4822478 4683217 4744885 (FeAPSO), EP-A-0 158 975 and
U.S. Pat. No. 4935216 (ZnAPSO, EP-A-0 161 489 (CoAPSO), EP-A-0
158 976 (ELAPO, where EL is Co, Fe, Mg, Mn, Ti or Zn), U.S. Pat.
No. 4310440 (AlPO.sub.4), EP-A-0 158 350 (SENAPSO), U.S. Pat.
No. 4973460 (LiAPSO), U.S. Pat. No. 4789535 (LiAPO), U.S. Pat.
No. 4992250 (GeAPSO), U.S. Pat. No. 4888167 (GeAPO), U.S. Pat.
No. 5057295 (BAPSO), U.S. Pat. No. 4738837 (CrAPSO), U.S. Pat.
Nos. 4759919 and 4851106 (CrAPO), U.S. Pat. Nos. 4758419
4882038 5434326 and 5478787 (MgAPSO), U.S. Pat. No. 4554143
(FeAPO), U.S. Pat. No. 4894213 (AsAPSO), U.S. Pat. No. 4913888
(AsAPO), U.S. Pat. Nos. 4686092 4846956 and 4793833 (MaAPSO),
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. No. 4824554 4744970 (CoAPSO),
U.S. Pat. No. 4735806 (GaAPSO) EP-A-0 293 937 (QAPSO, where Q
is framework oxide unit [QO.sub.2]), as well as U.S. Pat. Nos. 4567029
4686093 4781814 4793984 4801364 4853197 4917876
4952384 4956164 4956165 4973785 5241093 5493066
and 5675050 all of which are herein fully incorporated by reference.
[0049] 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.
[0050] The more preferred molecular sieves are SAPO molecular sieves,
and metal-substituted SAPO molecular sieves. Suitable metal substituents
are alkali metals of Group IA of the Periodic Table of Elements,
an alkaline earth metals of Group IIA of the Periodic Table of Elements,
a rare earth metals of Group IIIB, including the Lanthanides: lanthanum,
cerium, praseodymium, neodymium, samarium, europium, gadolinium,
terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium;
and scandium or yttrium of the Periodic Table of Elements, transition
metals of Groups IVB, VB, VIB, VIIB, VIIIB, and IB of the Periodic
Table of Elements and mixtures of any of these metal species. In
one 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 metal atoms may be inserted into the framework of a
molecular sieve through a tetrahedral unit, such as [MeO.sub.2],
and carry a net charge depending on the valence state of the metal
substituent. For example, in one embodiment, when the metal substituent
has a valence state of +2 +3 +4 +5 or +6 the net charge of
the tetrahedral unit is between -2 and +2.
[0051] 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
[0052] 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 m has a value from 0 to 1
preferably 0 to 0.5 and most preferably from 0 to 0.3; x, y, and
z represent the mole fraction of Al, P and M as tetrahedral oxides,
where M is a metal selected from one of Group IA, IIA, IB, IIIB,
IVB, VB, VIB, VIIB, VIIIB and Lanthanide's of the Periodic Table
of Elements. Preferably M is selected from one of the group consisting
of Si, Co, Cr, Cu, Fe, Ga, Ge, Mg, Mn, Ni, Sn, Ti, Zn and Zr. In
an embodiment, m is greater than or equal to 0.2 and x, y and z
are greater than or equal to 0.01. In another embodiment, m is greater
than 0.1 to about 1 x is greater than 0 to about 0.25 y is in
the range of from 0.4 to 0.5 and z is in the range of from 0.25
to 0.5 more preferably m is from 0.15 to 0.7 x is from 0.01 to
0.2 y is from 0.4 to 0.5 and z is from 0.3 to 0.5.
[0053] Where the molecular sieve is a silicoaluminophosphate or
metal-containing silicoaluminophosphate, the SAPO typically 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 one 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.
[0054] Non-limiting examples of SAPO and AlPO molecular sieves
useful herein include one or a combination of SAPO-5 SAPO-8 SAPO-11
SAPO-16 SAPO-17 SAPO-18 SAPO-20 SAPO-31 SAPO-34 SAPO-35 SAPO-36
SAPO-37 SAPO-40 SAPO-41 SAPO-42 SAPO-44 (U.S. Pat. No. 6162415),
SAPO-47 SAPO-56 AlPO-5 AlPO-11 AlPO-18 AlPO-31 AlPO-34 AlPO-36
AlPO-37 AlPO-46 and metal containing molecular sieves thereof.
Of these, particularly useful molecular sieves are one or a combination
of SAPO-18 SAPO-34 SAPO-35 SAPO-44 SAPO-56 AlPO-18 and AlPO-34
and metal containing derivatives thereof, such as one or a combination
of SAPO-18 SAPO-34 AlPO-34 and AlPO-18 and metal containing derivatives
thereof, and especially one or a combination of SAPO-34 and AlPO-18
and metal containing derivatives thereof.
[0055] 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 U.S. Patent Application Publication No.
2002-0165089 and International Publication No. WO 98/15496 published
Apr. 16 1998 both of which are herein fully incorporated by reference.
For example, SAPO-18 AlPO-18 and RUW-18 have an AEI framework-type,
and SAPO-34 has a CHA framework-type. Thus the molecular sieve used
herein may comprise at least one intergrowth phase of AEI and CHA
framework-types, especially where the ratio of CHA framework-type
to AEI framework-type, as determined by the DIFFaX method disclosed
in U.S. Patent Application Publication No. 2002-0165089 is greater
than 1:1.
[0056] Molecular Sieve Synthesis
[0057] 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,
water and a templating agent, such as a nitrogen containing organic
compound. Typically, a combination of sources of silicon and aluminum
or silicon, aluminum and phosphorus, water and optionally 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, which can then recovered by filtration,
centrifugation and/or decanting.
[0058] 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 tetraalkylorthosilicates, for example, tetramethylorthosilicate
(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.
[0059] 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.
[0060] Non-limiting examples of phosphorus sources, which may also
include aluminum-containing phosphorus compositions, include phosphoric
acid, organic phosphates such as triethyl phosphate, and crystalline
or amorphous aluminophosphates such as AlPO.sub.4 phosphorus salts,
or combinations thereof. A convenient source of phosphorus is phosphoric
acid, particularly when producing a silicoaluminophosphate.
[0061] Templating agents are generally compounds that contain elements
of Group 15 of the Periodic Table of Elements, particularly nitrogen,
phosphorus, arsenic and antimony. Typical templating agents also
contain at least one alkyl or aryl group, such as an alkyl or aryl
group having from 1 to 10 carbon atoms, for example from 1 to 8
carbon atoms. Preferred templating agents are often nitrogen-containing
compounds, such as amines, quaternary ammonium compounds and combinations
thereof. Suitable quaternary ammonium compounds are represented
by the general formula R.sub.4N.sup.+, where each R is hydrogen
or a hydrocarbyl or substituted hydrocarbyl group, preferably an
alkyl group or an aryl group having from 1 to 10 carbon atoms.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] In one embodiment, the synthesis of a molecular sieve is
aided by seeds from another or the same framework type molecular
sieve.
[0066] 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.
[0067] One method for crystallization involves subjecting an aqueous
reaction mixture containing an excess amount of a templating agent,
subjecting the mixture to crystallization under hydrothermal conditions,
establishing an equilibrium between molecular sieve formation and
dissolution, and then, removing some of the excess templating agent
and/or organic base to inhibit dissolution of the molecular sieve.
See for example U.S. Pat. No. 5296208 which is herein fully incorporated
by reference.
[0068] 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.
[0069] 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, normally termed the "wet
filter cake", may then be washed, such as with water, and then
dried, such as in air, before being formulated into a catalyst composition.
Alternatively, as will be discussed in more detail below, in the
present catalyst formulation method, the wet filter cake may be
formulated into a catalyst composition directly, that is without
any drying, or after only partial drying.
[0070] 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.
[0071] Phosphorus Compound
[0072] The catalyst composition employed herein contains a phosphorus
compound separate from any phosphorus contained by said molecular
sieve. The phosphorus source may be an organic phosphorus compound,
but is preferably an inorganic phosphorus compound and more preferably
is soluble in water. Suitable phosphorus compounds include acids
and their derivative salts such as (1) higher (P.sup.5+ and P.sup.3+)
acids and salts, for example phosphoric acid (H.sub.3PO.sub.4),
ammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen
phosphate and phosphorus acid (H.sub.3PO.sub.3), which is bifunctional,
forming salts such as ammonium hydrogen phosphite and ammonium phosphite;
(2) lower acids and salts, for example, hyprophosphorous acid (H.sub.3PO.sub.2)
and ammonium phosphinate; (3) di- and polyacids and salts, for example,
H.sub.4P.sub.2O.sub.4 H.sub.4P.sub.2O.sub.5 H.sub.4P.sub.2O.sub.6
H.sub.5P.sub.3O.sub.8 and their ammonium and ammonium hydrogen salts;
(4) condensed phosphates, for example, pyrophosphates (M.sup.I.sub.4P.sub.2O.-
sub.7), tripolyphosphates (M.sup.I.sub.4P.sub.3O.sub.10) and metaphosphates
(M.sup.I.sub.3P.sub.3O.sub.9 and M.sup.I.sub.4P.sub.4O.sub- .2).
Description of the preparation and properties of these phosphorus
compounds can be found in "Advanced Inorganic Chemistry",
by F. A. Cotton, G. Wilkinson, 5th Edition, pp. 421-427 John Wiley
& Sons, New York, 1988 the entire disclosure of which is fully
incorporated herein by reference.
[0073] Other phosphorus salts can also be used as long as the cations
introduced do not interfere the oxygenate to olefin reaction of
the molecular sieve, for instance, use of alkali and alkaline salts
in high levels will lead to reduction of number of acid sites of
the catalyst unless these cations introduced are removed using addition
ion exchange steps, e.g., ion exchange with ammonium salt solution
or acid solution.
[0074] As will discussed in more detail below, the phosphorus compound
is added during formulation of the catalyst composition and, in
particular, to a slurry of the molecular sieve and a binder or binder
precursor.
[0075] The amount of phosphorus compound added during formulation
of the catalyst composition is typically such that the final catalyst
composition contains between about 0.05 and about 15 wt %, for example
between about 0.1 and about 10 wt %, such as between about 0.5 and
about 6 wt %, and conveniently between greater 1.0 and about 5 wt
%, of phosphorus expressed as P.sub.2O.sub.5 by weight of the catalyst
composition.
[0076] Binder and/or Matrix Material
[0077] In producing a catalyst composition, the molecular sieve
and phosphorus compound described above are combined with a binder
or binder precursor and typically also with a matrix material. The
resulting combination can then be formed into particles of the desired
size and shape by well-known techniques such as spray drying, pelletizing,
extrusion, and the like.
[0078] 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 chlorohydrate. 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.
[0079] Aluminum chlorohydrate, a hydroxylated aluminum based sol
containing a chloride counter ion, has the general formula of Al.sub.mO.sub.n(OH).sub.oCl.sub.p.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 Al.sub.13O.sub.4(OH).sub.24Cl.sub.7.12(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.
[0080] 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.
[0081] In one embodiment, the weight ratio of the binder to the
molecular sieve is in the range of from about 0.1 to 0.5 such as
in the range of from 0.1 to less than 0.5 for example in the range
of from 0.11 to 0.48 conveniently from 0.12 to about 0.45 typically
from 0.13 to less than 0.45 and particularly in the range of from
0.15 to about 0.4. In another embodiment, the weight ratio of the
binder to the molecular sieve is in the range of from 0.11 to 0.45
such as in the range of from about 0.12 to less than 0.40 for example
in the range of from 0.15 to about 0.35 and conveniently in the
range of from 0.2 to about 0.3.
[0082] Where the catalyst composition contains a matrix material,
this is preferably different from the active metal oxide and any
binder. Matrix materials are typically effective in reducing overall
catalyst cost, acting as thermal sinks to assist in shielding heat
from the catalyst composition for example during regeneration, densifying
the catalyst composition, and increasing catalyst strength such
as crush strength and attrition resistance.
[0083] Non-limiting examples of matrix materials include one or
more of rare earth metal oxides, non-active metal oxides including
magnesia, thoria, 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.
[0084] In a preferred embodiment, the matrix material is a clay
or a clay-type composition, particularly having a low iron or titania
content, and most preferably is kaolin. Kaolin has been found to
form a pumpable, high solids content slurry, to have a low fresh
surface area, and to pack together easily due to its platelet structure.
A preferred average particle size of the matrix material, most preferably
kaolin, is from about 0.1 .mu.m to about 0.6 .mu.m with a D.sub.90
particle size distribution of less than about 1 .mu.m.
[0085] Where the catalyst composition contains a binder and a matrix
material, the weight ratio of the binder to the matrix material
is typically from 1:15 to 1:5 such as from 1:10 to 1:4 and particularly
from 1:6 to 1:5. The amount of binder is typically from about 2%
by weight to about 30% by weight, such as from about 5% by weight
to about 20% by weight, and particularly from about 7% by weight
to about 15% by weight, based on the total weight of the binder,
the molecular sieve and matrix material. It has been found that
a higher sieve content and lower matrix content increases the molecular
sieve catalyst composition performance, whereas a lower sieve content
and higher matrix content improves the attrition resistance of the
composition.
[0086] In general, the amount of binder and/or matrix material
is such that the formulated molecular sieve catalyst composition
contains from about 1% to about 99%, such as from about 10% to about
90%, such as from about 10% to about 80%, for example from about
20% to about 70%, and conveniently from about 25% to about 60% by
weight of the molecular sieve based on the total weight of the molecular
sieve catalyst composition.
[0087] Method of Making The Catalyst Composition
[0088] In making the catalyst composition of the invention, a molecular
sieve as described above is formed into a slurry with a binder or
binder precursor and a liquid medium, such as water, and then the
phosphorus compound is added to the slurry. After addition of the
phosphorus compound, a matrix material may be added to the slurry
and the resultant mixture can then be formed into the desired catalyst
particles, such as by spray drying. The resultant catalyst composition
can then be calcined.
[0089] In one embodiment, the molecular sieve used to form the
slurry with the binder or binder precursor is in its as-synthesized
state and has not been fully dried. As used herein, the term "not
fully dried" is defined to include no drying up to not calcining
the crystalline molecular sieve material. In addition, the term
"partially dried" is used herein to include drying the
crystalline molecular sieve material to a level wherein after drying
the amount of templating agent associated with the molecular sieve
is in the range of from about 50 such as from about 60 for example
from about 70 and preferably from about 80 weight percent to 100
weight percent of the original amount of templating agent used to
form the molecular sieve originally.
[0090] For example, the molecular sieve used to form the slurry
with the binder or binder precursor can be the wet filter cake resulting
from separation of the as-synthesized molecular sieve from the liquid,
normally aqueous, crystallization medium. The wet filter cake can
be used directly, without any intermediate washing and/or dehydration.
[0091] Alternatively, the as-synthesized molecular sieve, without
or without previous washing, can be dried, preferably in air, to
a level such that the amount of liquid medium, usually water, contained
by the molecular sieve is in the range of from about 0 weight percent
to about 80 weight percent liquid, such as in the range of from
greater than 5 weight percent to about 70 weight percent, for example
from about 10 weight percent to about 70 weight percent, and conveniently
from about 20 weight percent to about 60 weight percent based on
the total weight of the synthesized molecular sieve and liquid.
[0092] Determination of the percentage of liquid medium and the
percentage of template for purposes of this specification uses a
Thermal Gravimetric Analysis (TGA) technique as follows. An amount
the molecular sieve material, the sample, is loaded into a sample
pan of a Cahn TG-121 Microbalance, available from Cahn Instrument,
Inc., Cerritos, Calif. During the TGA technique, a flow of 114 cc/min
(STP) air is used. The sample is then heated from 25.degree. C.
to 180.degree. C. at 30.degree. C./min and held at 180.degree. C.
for 3 hours or until the weight of the sample becomes constant.
The weight loss of the sample expressed as a percentage of the original
sample weight is then treated as the percentage of the liquid medium.
Subsequently, the sample is heated at 30.degree. C./min from 180.degree.
C. to 650.degree. C. and held at 650.degree. C. for 2 hours. The
additional weight loss expressed as a percentage of the original
sample weight is regarded as the weight loss of the templating agent.
The total weight loss during the entire TGA treatment expressed
as a percentage of the original sample weight is defined as Loss-On-Ignition
(LOI).
[0093] In formulating the catalyst composition, the binder or binder
precursor and the molecular sieve are initially combined in the
presence of a liquid to form a slurry typically containing in the
range of from about 25 weight percent to about 55 weight percent,
such as from about 30 weight percent to 50 weight percent, solid
particles, of which from about 20 weight percent to about 90 weight
percent, such as from about 25 weight percent to about 85 weight
percent, comprise the molecular sieve. The liquid used to form the
slurry can, for example, be one or a combination of water, an alcohol,
a ketone, an aldehyde, and/or an ester, but normally will be water.
[0094] The slurry is milled to form a substantially homogeneous
mixture and then a phosphorus compound as described above, either
in solid form or as a liquid solution, is added to the slurry. The
resultant mixture is further milled to ensure even dispersion of
the phosphorus compound and then a matrix material is added to the
mixture, typically such that the matrix-containing mixture contains
in the range of from about 25 weight percent to about 55 weight
percent, such as from about 30 weight percent to 50 weight percent,
solid particles.
[0095] The matrix-containing mixture is milled to form a substantially
homogeneous catalyst precursor mixture having the desired particle
size distribution, for example such that at least 90 percent of
the solid particles having a diameter less than 20 .mu.m, preferably
less than 10 .mu.m. Typically the catalyst precursor mixture contains
in the range of from about 25 weight percent to about 55 weight
percent, such as from about 30 weight percent to 50 weight percent,
solid particles. In addition, the catalyst precursor mixture contains
from about 20 to about 90 weight percent, such as from about 25
to about 85 weight percent, of the molecular sieve, from about 2
to about 25 weight percent, such as from about 3 to about 23 weight
percent, of the binder or binder precursor, from about 5 to about
85 weight percent, such as from about 10 to about 80 weight percent,
of the matrix material, and from about 0.05 to about 15 weight percent,
such as from about 0.1 to about 10 weight percent, of the phosphorus
compound.
[0096] The catalyst precursor mixture is then fed to a forming
unit that produces the molecular sieve catalyst composition. In
a preferred embodiment, the forming unit is spray dryer. Typically,
the forming unit is maintained at a temperature sufficient to remove
most of the liquid from the precursor mixture, and from the resulting
molecular sieve catalyst composition. The resulting catalyst composition
when formed in this way takes the form of microspheres.
[0097] When a spray drier is used as the forming unit, typically,
the precursor mixture is fed to the spray drying volume with a drying
gas with an average inlet temperature ranging from 100.degree. C.
to 550.degree. C., and a combined outlet temperature ranging from
50.degree. C. to about 225.degree. C. In an embodiment, the average
diameter of the spray dried formed catalyst composition is from
about 30 .mu.m to about 300 .mu.m, such as from about 40 .mu.m to
about 250 .mu.m, for example from about 50 .mu.m to about 200 .mu.m,
and conveniently from about 55 .mu.m to about 100 .mu.m.
[0098] For example, the catalyst precursor mixture may be directed
onto the perimeter of a spinning wheel that distributes the mixture
into small droplets, the size of which is controlled by many factors
including mixture viscosity, surface tension, flow rate, pressure,
the temperature of the slurry, the shape and dimension of the nozzle(s),
and the spinning rate of the wheel. These droplets are then dried
in a co-current or counter-current flow of air passing through a
spray drier to form a substantially dried or dried molecular sieve
catalyst composition, more specifically a molecular sieve composition
in a powder or a microsphere form.
[0099] Other methods for forming a molecular sieve catalyst composition
are described in U.S. patent application Ser. No. 09/617714 filed
Jul. 17 2000 (spray drying using a recycled molecular sieve catalyst
composition), which is herein incorporated by reference.
[0100] 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 850.degree. C., such as from about 600.degree. C. to about
800.degree. C. The calcination environment is not critical and typically
can include air (which may contain a small amount of water vapor),
nitrogen, helium, flue gas (combustion product lean in oxygen),
or any combination thereof. For example, although calcination in
nitrogen may be employed in various tests used in the present specification,
it should be understood that calcination in nitrogen is not essential
in producing the catalyst composition of the invention.
[0101] In one practical embodiment, the catalyst composition is
heated in nitrogen at a temperature of from about 700.degree. C.
to about 800.degree. C. Heating is carried out for a period of time
typically from 30 minutes to 15 hours, such as from 1 hour to about
10 hours, for example from about 1 hour to about 5 hours, and particularly
from about 2 hours to about 4 hours.
[0102] The resultant molecular sieve catalyst composition typically
has a micropore surface area (MSA) in the range of from about 400
m.sup.2/g-molecular sieve to about 600 m.sup.2/g-molecular sieve,
for example in the range of from 425 m.sup.2/g-molecular sieve to
about 550 m.sup.2/g-molecular sieve, and conveniently in the range
of from about 450 m.sup.2/g-molecular sieve to about 550 m.sup.2/g-molecular
sieve. Moreover, the catalyst composition exhibits a high degree
of thermal stability such that in a test involving calcination in
nitrogen at 760.degree. C. and atmospheric pressure for 3 hours,
the catalyst composition has an MSA in excess of 20%, such as in
excess of 50%, conveniently in excess of 75%, and even in excess
of 100%, of the MSA of said molecular sieve after calcination at
650.degree. C. in nitrogen at atmospheric pressure for 2 hours.
[0103] The catalyst composition also exhibits improved hydrothermal
stability as evidenced by, for example, the retention of its activity
for converting methanol to olefins after high temperature hydrothermal
treatment such as would be experienced during regeneration. Thus
in one embodiment, after hydrothermal treatment at 800.degree. C.
for 18 hours at a water vapor pressure of 45 psig, the present catalyst
composition retains at least 15%, such as at least 20%, and generally
at least 25% of the methanol conversion activity of the untreated
catalyst composition.
[0104] In addition, the molecular sieve catalyst composition has
improved attrition resistance as determined by its Attrition Rate
Index (ARI), which measures the weight percent catalyst composition
attrited per hour in a standardized attrition test. In particular,
ARI is measured by adding 6.0 g of catalyst composition having a
particle size ranging from 53 microns to 125 microns to a hardened
steel attrition cup. Approximately 23700 cc/min of nitrogen gas
is bubbled through a water-containing bubbler to humidify the nitrogen.
The wet nitrogen passes through the attrition cup, and exits the
attrition apparatus through a porous fiber thimble. The flowing
nitrogen removes the finer particles, with the larger particles
being retained in the cup. The porous fiber thimble separates the
fine catalyst particles from the nitrogen that exits through the
thimble. The fine particles remaining in the thimble represent the
catalyst composition that has broken apart through attrition. The
nitrogen flow passing through the attrition cup is maintained for
1 hour and the fines collected in the thimble are removed from the
unit. A new thimble is then installed and the catalyst left in the
attrition unit is attrited for an additional 3 hours, under the
same gas flow and moisture levels. The fines collected in the thimble
are recovered. The collection of fine catalyst particles separated
by the thimble after the first hour are weighed.
[0105] The amount in grams of fine particles divided by the original
amount of catalyst charged to the attrition cup expressed on per
hour basis is the ARI, in weight percent per hour. ARI is represented
by the formula: ARI=C/(B+C)/D multiplied by 100%, wherein B is weight
of catalyst composition left in the cup after the attrition test,
C is the weight of collected fine catalyst particles after the first
hour of attrition treatment, and D is the duration of treatment
in hours after the first hour attrition treatment.
[0106] Typically, the molecular sieve catalyst composition has
an ARI less than 5 weight percent per hour, such as less than 3
weight percent per hour, such as less than 1 weight percent per
hour, and for example less than 0.95 weight percent per hour. In
one embodiment, the molecular sieve catalyst composition has an
ARI in the range of from 0.05 weight percent per hour to less than
3 weight percent per hour, such as from about 0.05 weight percent
per hour to less than 0.95 weight percent per hour, and for example
from about 0.05 weight percent per hour to 0.8 weight percent per
hour.
[0107] In one practical embodiment of the invention, the molecular
sieve catalyst composition comprises a molecular sieve in an amount
of from 25 weight percent to 85 weight percent, a phosphorus compound
in an amount of from 0.5 to 6 weight percent expressed as P.sub.2O.sub.5
a binder in an amount of from 3 to 23 weight percent, and a matrix
material in an amount of from 5 to 85 weight percent, based on the
total weight of the catalyst composition, after calcination, has
an MSA from 450 m.sup.2/g-molecular sieve to 550 m.sup.2/g-molecular
sieve, and an ARI less than 0.95 weight percent per hour.
[0108] Process For Using the Molecular Sieve Catalyst Compositions
[0109] The catalyst compositions described above are useful in
a variety of processes including cracking, of for example a naphtha
feed to light olefin(s) (U.S. Pat. No. 6300537) or higher molecular
weight (MW) hydrocarbons to lower MW hydrocarbons; hydrocracking,
of for example heavy petroleum and/or cyclic feedstock; isomerization,
of for example aromatics such as xylene; polymerization, of for
example one or more olefin(s) to produce a polymer product; reforming;
hydrogenation; dehydrogenation; dewaxing, of for example hydrocarbons
to remove straight chain paraffins; absorption, of for example alkyl
aromatic compounds for separating out isomers thereof; alkylation,
of for example aromatic hydrocarbons such as benzene and alkyl benzene,
optionally with propylene to produce cumene or with long chain olefins;
transalkylation, of for example a combination of aromatic and polyalkylaromatic
hydrocarbons; dealkylation; hydrodecyclization; disproportionation,
of for example toluene to make benzene and paraxylene; oligomerization,
of for example straight and branched chain olefin(s); and dehydrocyclization.
[0110] Preferred processes include processes for converting naphtha
to highly aromatic mixtures; converting light olefin(s) to gasoline,
distillates and lubricants; converting oxygenates to olefin(s);
converting light paraffins to olefins and/or aromatics; and converting
unsaturated hydrocarbons (ethylene and/or acetylene) to aldehydes
for conversion into alcohols, acids and esters.
[0111] The most preferred process of the invention is a process
directed to the conversion of a feedstock to one or more olefin(s).
Typically, the feedstock contains one or more aliphatic-containing
compounds such that the aliphatic moiety contains from 1 to about
50 carbon atoms, such as from 1 to 20 carbon atoms, for example
from 1 to 10 carbon atoms, and particularly from 1 to 4 carbon atoms.
[0112] 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.
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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.
[0118] Using the catalyst composition of the invention for the
conversion of a feedstock, preferably a feedstock containing one
or more oxygenates, the amount of olefin(s) produced based on the
total weight of hydrocarbon produced is greater than 50 weight percent,
typically greater than 60 weight percent, such as greater than 70
weight percent, and preferably greater than 75 weight percent. In
one embodiment, the amount of ethylene and/or propylene produced
based on the total weight of hydrocarbon product produced is greater
than 65 weight percent, such as greater than 70 weight percent,
for example greater than 75 weight percent, and preferably greater
than 78 weight percent. Typically, the amount ethylene produced
in weight percent based on the total weight of hydrocarbon product
produced, is greater than 30 weight percent, such as greater than
35 weight percent, for example greater than 40 weight percent. In
addition, the amount of propylene produced in weight percent based
on the total weight of hydrocarbon product produced is greater than
20 weight percent, such as greater than 25 weight percent, for example
greater than 30 weight percent, and preferably greater than 35 weight
percent.
[0119] 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.
[0120] 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.
[0121] 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.
[0122] 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.
[0123] 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.sup.-1 to about 5000 hr.sup.-1 such as from about
2 hr.sup.-1 to about 3000 hr.sup.-1 for example from about 5 hr.sup.-1
to about 1500 hr.sup.-1 and conveniently from about 10 hr.sup.-1
to about 1000 hr.sup.-1. In one embodiment, the WHSV is greater
than 20 hr.sup.-1 and, where feedstock contains methanol and/or
dimethyl ether, is in the range of from about 20 hr.sup.-1 to about
300 hr.sup.-1.
[0124] 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.
[0125] 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.
[0126] 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.
[0127] 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.
[0128] 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.
[0129] In such a process the reactor system conveniently includes
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.
[0130] 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.
[0131] 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.
[0132] 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.
[0133] 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.
[0134] Non-limiting examples of suitable regeneration media include
one or more of oxygen, O.sub.3 SO.sub.3 N.sub.2O, NO, NO.sub.2
N.sub.2O.sub.5 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).
[0135] 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.
[0136] 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 in
disclosed U.S. Pat. No. 6290916 (controlling moisture), which
is herein fully incorporated by reference.
[0137] The regenerated catalyst composition withdrawn from the
regeneration system, preferably from the catalyst cooler, is combined
with a fresh molecular sieve catalyst composition and/or re-circulated
molecular sieve catalyst composition and/or feedstock and/or fresh
gas or liquids, and returned to the riser reactor(s). In 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).
[0138] 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.
[0139] 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.
[0140] 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.
[0141] Non-limiting examples of these towers, columns, splitters
or trains used alone or in combination include one or more of a
demethanizer, preferably a high temperature demethanizer, a dethanizer,
a depropanizer, a wash tower often referred to as a caustic wash
tower and/or quench tower, absorbers, adsorbers, membranes, ethylene
(C2) splitter, propylene (C3) splitter and butene (C4) splitter.
[0142] Various recovery systems useful for recovering 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.
[0143] Other recovery systems that include purification systems,
for example for the purification of olefin(s), are described in
Kirk-Othmer Encyclopedia of Chemical Technology, 4th Edition, Volume
9 John Wiley & Sons, 1996 pages 249-271 and 894-899 which
is herein incorporated by reference. Purification systems are also
described in for example, U.S. Pat. No. 6271428 (purification
of a diolefin hydrocarbon stream), U.S. Pat. No. 6293999 (separating
propylene from propane), and U.S. patent application Ser. No. 09/689363
filed Oct. 20 2000 (purge stream using hydrating catalyst), which
are herein incorporated by reference.
[0144] Generally accompanying most recovery systems is the production,
generation or accumulation of additional products, by-products and/or
contaminants along with the preferred prime products. The preferred
prime products, the light olefins, such as ethylene and propylene,
are typically purified for use in derivative manufacturing processes
such as polymerization processes. Therefore, in the most preferred
embodiment of the recovery system, the recovery system also includes
a purification system. For example, the light olefin(s) produced
particularly in a MTO process are passed through a purification
system that removes low levels of by-products or contaminants.
[0145] Non-limiting examples of contaminants and by-products include
generally polar compounds such as water, alcohols, carboxylic acids,
ethers, carbon oxides, sulfur compounds such as hydrogen sulfide,
carbonyl sulfides and mercaptans, ammonia and other nitrogen compounds,
arsine, phosphine and chlorides. Other contaminants or by-products
include hydrogen and hydrocarbons such as acetylene, methyl acetylene,
propadiene, butadiene and butyne.
[0146] Typically, in converting one or more oxygenates to olefin(s)
having 2 or 3 carbon atoms, a minor amount hydrocarbons, particularly
olefin(s), having 4 or more carbon atoms is also produced. The amount
of C.sub.4+ hydrocarbons is normally less than 20 weight percent,
such as less than 10 weight percent, for example less than 5 weight
percent, and particularly less than 2 weight percent, based on the
total weight of the effluent gas withdrawn from the process, excluding
water. Typically, therefore the recovery system may include one
or more reaction systems for converting the C.sub.4+ impurities
to useful products.
[0147] Non-limiting examples of such reaction systems are described
in U.S. Pat. No. 5955640 (converting a four carbon product into
butene-1), U.S. Pat. No. 4774375 (isobutane and butene-2 oligomerized
to an alkylate gasoline), U.S. Pat. No. 6049017 (dimerization
of n-butylene), U.S. Pat. Nos. 4287369 and 5763678 (carbonylation
or hydroformulation of higher olefins with carbon dioxide and hydrogen
making carbonyl compounds), U.S. Pat. No. 4542252 (multistage
adiabatic process), U.S. Pat. No. 5634354 (olefin-hydrogen recovery),
and Cosyns, J. et al., Process for Upgrading C3 C4 and C5 Olefinic
Streams, Pet. & Coal, Vol. 37 No. 4 (1995) (dimerizing or oligomerizing
propylene, butylene and pentylene), which are all fully herein incorporated
by reference.
[0148] The preferred light olefin(s) produced by any one of the
processes described above are high purity prime olefin(s) products
that contain a single carbon number olefin in an amount greater
than 80 percent, such as greater than 90 weight percent, such as
greater than 95 weight percent, for example at least about 99 weight
percent, based on the total weight of the olefin.
[0149] In one practical embodiment, the process of the invention
forms part of an integrated process for producing light olefin(s)
from a hydrocarbon feedstock, preferably a gaseous hydrocarbon feedstock,
particularly methane and/or ethane. The first step in the process
is passing the gaseous feedstock, preferably in combination with
a water stream, to a syngas production zone to produce a synthesis
gas (syngas) stream, typically comprising carbon dioxide, carbon
monoxide and hydrogen. Syngas production is well known, and typical
syngas temperatures are in the range of from about 700.degree. C.
to about 1200.degree. C. and syngas pressures are in the range of
from about 2 MPa to about 100 MPa. Synthesis gas streams are produced
from natural gas, petroleum liquids, and carbonaceous materials
such as coal, recycled plastic, municipal waste or any other organic
material. Preferably synthesis gas stream is produced via steam
reforming of natural gas.
[0150] The next step in the process involves contacting the synthesis
gas stream generally with a heterogeneous catalyst, typically a
copper based catalyst, to produce an oxygenate containing stream,
often in combination with water. In one embodiment, the contacting
step is conducted at temperature in the range of from about 150.degree.
C. to about 450.degree. C. and a pressure in the range of from about
5 MPa to about 10 MPa.
[0151] This oxygenate containing stream, or crude methanol, typically
contains the alcohol product and various other components such as
ethers, particularly dimethyl ether, ketones, aldehydes, dissolved
gases such as hydrogen methane, carbon oxide and nitrogen, and fuel
oil. The oxygenate containing stream, crude methanol, in the preferred
embodiment is passed through a well known purification processes,
distillation, separation and fractionation, resulting in a purified
oxygenate containing stream, for example, commercial Grade A and
AA methanol.
[0152] The oxygenate containing stream or purified oxygenate containing
stream, optionally with one or more diluents, can then be used as
a feedstock in a process to produce light olefin(s), such as ethylene
and/or propylene. Non-limiting examples of this integrated process
are described in EP-B-0 933 345 which is herein fully incorporated
by reference.
[0153] In another more fully integrated process, that optionally
is combined with the integrated processes described above, the olefin(s)
produced are directed to, in one embodiment, one or more polymerization
processes for producing various polyolefins. (See for example U.S.
patent application Ser. No. 09/615376 filed Jul. 13 2000 which
is herein fully incorporated by reference.)
[0154] Polymerization processes include solution, gas phase, slurry
phase and a high pressure processes, or a combination thereof. Particularly
preferred is a gas phase or a slurry phase polymerization of one
or more olefin(s) at least one of which is ethylene or propylene.
These polymerization processes utilize a polymerization catalyst
that can include any one or a combination of the molecular sieve
catalysts discussed above. However, the preferred polymerization
catalysts are the Ziegler-Natta, Phillips-type, metallocene, metallocene-type
and advanced polymerization catalysts, and mixtures thereof.
[0155] In a preferred embodiment, the integrated process comprises
a process for polymerizing one or more olefin(s) in the presence
of a polymerization catalyst system in a polymerization reactor
to produce one or more polymer products, wherein the one or more
olefin(s) have been made by converting an alcohol, particularly
methanol, using a molecular sieve catalyst composition as described
above. The preferred polymerization process is a gas phase polymerization
process and at least one of the olefins(s) is either ethylene or
propylene, and preferably the polymerization catalyst system is
a supported metallocene catalyst system. In this embodiment, the
supported metallocene catalyst system comprises a support, a metallocene
or metallocene-type compound and an activator, preferably the activator
is a non-coordinating anion or alumoxane, or combination thereof,
and most preferably the activator is alumoxane.
[0156] The polymers produced by the polymerization processes described
above include linear low density polyethylene, elastomers, plastomers,
high density polyethylene, low density polyethylene, polypropylene
and polypropylene copolymers. The propylene based polymers produced
by the polymerization processes include atactic polypropylene, isotactic
polypropylene, syndiotactic polypropylene, and propylene random,
block or impact copolymers.
EXAMPLES
[0157] In order to provide a better understanding of the present
invention including representative advantages thereof, the following
examples are offered.
[0158] Constituents of a mixture used for formulating catalysts
will generally contain volatile components, including, but not limited
to, water and, in the case of molecular sieve, organic template.
It is common practice to describe the amount or proportion of these
constituents as being on a "calcined basis". On a "calcined
basis" is defined herein as the amount or fraction of each
component remaining after it has been mathematically reduced to
account for losses in weight expected to occur if the component
had been calcined. Thus, 10 grams of a component containing 25%
template would be described as "7.5 g on a calcined basis".
[0159] Synthesis of a SAPO-34 molecular sieve is well known, and
in the Examples below has a MSA of about 450 m.sup.2/g to 550 m.sup.2/g-molecular
sieve. Micropore surface area (MSA) is a measurement of the amount
of micropores present in a porous material. MSA is the difference
between the total surface area (BET surface area), determined from
relative pressures that give a linear plot, and the external surface
area, calculated from the slope of the linear region of the t-plot
with a small correction to put it on the same basis as the BET surface
area. This approach has been used for determining the amount of
zeolite in cracking catalysts by Johnson [M. F. L. Johnson, J. Catal.,
52 425-431 (1978)]. The t-plot is a transformation of the adsorption
isotherm in which relative pressure is replaced by t, the statistical
thickness of the adsorbed layer on nonporous material at the corresponding
relative pressure; see Lippens and de Boer for determining various
characteristics of pore systems, such as pore shapes [B. C. Lippens,
and J. H. de Boer, J. Catal., 4 319 (1965)]. Sing [K. S. W. Sing,
Chem. Ind., 829 (1967)] has introduced that the extrapolation of
a linear t-plot to t=0 can yield the volume of micropores.
[0160] MSA is determined using a MICROMERITICS Gemini 2375 from
Micromeritics Instrument Corporation, Norcross, Ga. The procedure
involves loading an amount, 0.15 g to 0.6 g, of a sample into the
sample cell for degassing at 300.degree. C. for a minimum of 2 hours.
During the analysis, the Evacuation Time is 1.0 minute, no free
space is used, and the sample density is 1.0 g/cc. Thirteen (13)
adsorption data points are collected with adsorption targets of:
1 Adsorption Data Adsorption Data Point Target (p/p.sub.0) Point
Target (p/p.sub.0) 1 0.00500 8 0.25000 2 0.07500 9 0.30000 3 0.01000
10 0.40000 4 0.05000 11 0.60000 5 0.10000 12 0.75000 6 0.15000 13
0.95000 7 0.20000
[0161] The correction factor used in the t-plot is 0.975. No de-sorption
points are collected. Other analysis parameters include, Analysis
Mode: Equilibrate; Equilibration Time: 5 second; Scan Rate: 10 seconds.
A t-plot from 0.00000 to 0.90000 is constructed using the ASTM certified
form of the Harkins and Jura equation (H-J Model): t(p)=(13.99/(0.034-log(p/p.sub.o))).sup.0.5.
It is shown by Cape and Kibby [J. A. Cape and C. L. Kibby, J. Colloids
and Interface Science, 138 516-520 (1990)] that the conventional
BET surface area of a microporous material can be decomposed quantitatively
into the external area and the micropore volume, as expressed by
equation given below: S.sub.micro=S.sub.tot-S.sub.ext=.nu..sub.m/d.sub.j,
where .nu..sub.m is the micropore volume, S.sub.mciro is the micropore
area calculated from S.sub.tot and S.sub.ext. S.sub.tot is given
by the conventional BET method, and S.sub.ext is the external area
taken from the t-plot. The proportionality factor, d.sub.j is a
nonphysical length the value of which depends on the pressure used
in the ex |