Molecular sieve abstract
Disclosed is a method of protecting the loss of catalytic activity
of metalloaluminophosphate molecular sieve, particularly a SAPO
molecular sieve, from contact with moisture. The method involves
heating the metalloaluminophosphate molecular sieve so as to remove
template, and provide a molecular sieve in sufficiently dry form
for storage.
Molecular sieve claims
What is claimed is:
1. A method of protecting activated metalloaluminophosphate molecular
sieve from catalytic deactivation due to contact with water, the
method comprising the steps of: a) providing a metalloaluminophosphate
molecular sieve having a template therein; b) heating the metalloaluminophosphate
molecular sieve to remove the template and form an activated metalloaluminophosphate
molecular sieve baying a water content of not greater than 1.25
wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve.
2. The method of claim 1 wherein the provided metalloaluminophosphate
molecular sieve is heated to remove the template and form an activated
metalloaluminophosphate molecular sieve having a water content of
not greater than 1.0 wt %, based on total weight of the activated
metalloaluminophosphate molecular sieve.
3. The method of claim 2 wherein the provided metalloaluminophosphate
molecular sieve is heated to remove the template and form an activated
metalloaluminophosphate molecular sieve having a water content of
not greater than 0.8 wt %, based on total weight of the activated
metalloaluminophosphate molecular sieve.
4. The method of claim 3 wherein the provided metalloaluminophosphate
molecular sieve is heated to remove the template and form an activated
metalloaluminophosphate molecular sieve having a water content of
not greater than 0.5 wt %, based on total weight of the activated
metalloaluminophosphate molecular sieve.
5. The method of claim 1 wherein the provided metalloaluminophosphate
molecular sieve is heated by calcining and then cooled by contacting
with a gas in an environment having a temperature of at least 225.degree.
C.
6. The method of claim 5 wherein the provided metalloaluminophosphate
molecular sieve is heated by calcining and then cooled by contacting
with a gas in an environment having a temperature of at least 250.degree.
C.
7. The method of claim 6 wherein the provided metalloaluminophosphate
molecular sieve is heated by calcining and then cooled by contacting
with a gas in an environment having a temperature of at least 275.degree.
C.
8. The method of claim 7 wherein the provided metalloaluminophosphate
molecular sieve is heated by calcining and then cooled by contacting
with a gas in an environment having a temperature of at least 300.degree.
C.
9. The method of claim 8 wherein the provided metalloaluminophosphate
molecular sieve is heated by calcining and then cooled by contacting
with a gas in an environment having a temperature of at least 340.degree.
C.
10. The method of claim 5 6 7 8 or 9 wherein the gas is air,
nitrogen, helium, flue gas, or any combination thereof.
11. The method of claim 10 wherein the environment has a relative
water pressure of not greater than 0.075.
12. The method of claim 11 wherein the environment has a relative
water pressure of not greater than 0.05.
13. The method of claim 12 wherein the environment has a relative
water pressure of not greater than 0.025.
14. The method of claim 13 wherein the environment has a relative
water pressure of not greater than 0.001.
15. The method of claim 1 wherein the metalloaluminophosphate
molecular sieve is SAPO molecular sieve.
16. The method of claim 1 wherein heating the metalloaluminophosphate
molecular sieve to remove the template and activate the metalloaluminophosphate
molecular sieve is carried out in one or more vessels.
17. A method of activating and drying metalloaluminophosphate molecular
sieve, the method comprising the steps of: a) providing a metalloaluminophosphate
molecular sieve having a template therein; b) removing the template
from the metalloaluminophosphate molecular sieve to activate the
metalloaluminophosphate molecular sieve; and c) drying the activated
metalloaluminophosphate molecular sieve to form an activated metalloaluminophosphate
molecular sieve baying a water content of not greater than 1.25
wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve.
18. The method of claim 17 wherein the activated metalloaluminophosphate
molecular sieve is dried to form an activated metalloaluminophosphate
molecular sieve having a water content of not greater than 1.0 wt
%, based on total weight of the activated metalloaluminophosphate
molecular sieve.
19. The method of claim 18 wherein the activated metalloaluminophosphate
molecular sieve is dried to form an activated metalloaluminophosphate
molecular sieve having a water content of not greater than 0.8 wt
%, based on total weight of the activated metalloaluminophosphate
molecular sieve.
20. The method of claim 19 wherein the activated metalloaluminophosphate
molecular sieve is dried to form an activated metalloaluminophosphate
molecular sieve having a water content of not greater than 0.5 wt
%, based on total weight of the activated metalloaluminophosphate
molecular sieve.
21. The method of claim 17 wherein the template is removed from
the metalloaluminophosphate molecular sieve by contacting with a
gas containing water vapor.
22. The method of claim 17 wherein the metalloaluminophosphate
molecular sieve is SAPO molecular sieve.
23. The method of claim 17 wherein the template is selected from
the group consisting of tetraethyl ammonium salts, cyclopentylamine,
aminomethyl cyclohexane, piperidine, triethylamine, cyclohexylamine,
tri-ethyl hydroxyethylamine, morpholine, dipropylamine (DPA), pyridine,
isopropylamine, heated degraded forms thereof, and combinations
thereof.
24. The method of claim 17 wherein the activated metalloaluminophosphate
molecular sieve is dried by contacting with a gas in an environment
having a relative water pressure of not greater than 0.075.
25. The method of claim 24 wherein the activated metalloaluminophosphate
molecular sieve is dried by contacting with a gas in an environment
having a relative water pressure of not greater than 0.05.
26. The method of claim 25 wherein the activated metalloaluminophosphate
molecular sieve is dried by contacting with a gas in an environment
having a relative water pressure of not greater than 0.025.
27. The method of claim 26 wherein the activated metalloaluminophosphate
molecular sieve is dried by contacting with a gas in an environment
having a relative water pressure of not greater than 0.001.
28. The method of claim 17 wherein the template is removed by
calcining with steam and the activated metalloaluminophosphate molecular
sieve is dried by contacting with a gas at a temperature of at least
225.degree. C.
29. The method of claim 28 wherein the template is removed by
calcining with steam and the activated metalloaluminophosphate molecular
sieve is dried by contacting with a gas at a temperature of at least
250.degree. C.
30. The method of claim 29 wherein the template is removed by
calcining with steam and the activated metalloaluminophosphate molecular
sieve is dried by contacting with a gas at a temperature of at least
275.degree. C.
31. The method of claim 30 wherein the template is removed by
calcining with steam and the activated metalloaluminophosphate molecular
sieve is dried by contacting with a gas at a temperature of at least
300.degree. C.
32. The method of claim 31 wherein the template is removed by
calcining with steam and the activated metalloaluminophosphate molecular
sieve is dried by contacting with a gas at a temperature of at least
340.degree. C.
33. The method of claim 17 wherein removing the template from
the metalloaluminophosphate molecular sieve to activate the metalloaluminophosphate
molecular sieve, and drying the activated metalloaluminophosphate
molecular sieve is carried out in one or more vessels.
34. A method of activating and drying metalloaluminophosphate molecular
sieve, the method comprising the step of: a) providing a metalloaluminophosphate
molecular sieve having a template therein; b) heating the metalloaluminophosphate
molecular sieve with steam at a temperature effective to remove
the template and activate the metalloaluminophosphate molecular
sieve; and c) contacting the activated metalloaluminophosphate molecular
sieve with a gas in an environment at conditions effective to form
a metalloaluminophosphate molecular sieve having a water content
of not greater than 1.25 wt %, based on total weight of the metalloaluminophosphate
molecular sieve.
35. The method of claim 34 wherein the activated metalloaluminophosphate
molecular sieve is contacted with a gas in an environment at conditions
effective to form a metalloaluminophosphate molecular sieve having
a water content of not greater than 1.0 wt %, based on total weight
of the metalloaluminophosphate molecular sieve.
36. The method of claim 35 wherein the activated metalloaluminophosphate
molecular sieve is contacted with a gas in an environment at conditions
effective to form a metalloaluminophosphate molecular sieve having
a water content of not greater than 0.8 wt %, based on total weight
of the metalloaluminophosphate molecular sieve.
37. The method of claim 36 wherein the motivated metalloaluminophosphate
molecular sieve is contacted with a gas in an environment at conditions
effective to form a metalloaluminophosphate molecular sieve having
a water content of not greater than 0.5 wt %, based on total weight
of the metalloaluminophosphate molecular sieve.
38. The method of claim 34 wherein the metalloaluminophosphate
molecular sieve is SAPO molecular sieve.
39. The method of claim 34 wherein heating the metalloaluminophosphate
molecular sieve with steam to remove the template and activate the
metalloaluminophosphate molecular sieve, and contacting the activated
metalloaluminophosphate molecular sieve with a gas is carried out
in one or more vessels.
40. A method of making activated metalloaluminophosphate molecular
sieve, the method comprising the steps of: a) providing a metalloaluminophosphate
molecular sieve having a template therein; b) contacting the metalloaluminophosphate
molecular sieve with a gas at conditions effective to remove the
template and activate the metalloaluminophosphate molecular sieve;
a) cooling the activated metalloaluminophosphate molecular sieve
to a temperature lower than that of the gas used to contact the
metalloaluminophosphate molecular sieve in step b), with the temperature
effective to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 1.25 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
41. The method of claim 40 wherein the temperature is effective
to form an activated metalloaluminophosphate molecular sieve having
a water content of not greater than 1.0 wt %, based on total weight
of the activated metalloaluminophosphate molecular sieve.
42. The method of claim 41 wherein the temperature is effective
to form an activated metalloaluminophosphate molecular sieve having
a water content of not greater than 0.8 wt %, based on total weight
of the activated metalloaluminophosphate molecular sieve.
43. The method of claim 42 wherein the temperature is effective
to form an activated metalloaluminophosphate molecular sieve having
a water content of not greater than 0.5 wt %, based on total weight
of the activated metalloaluminophosphate molecular sieve.
44. The method of claim 40 wherein the activated metalloaluminophosphate
molecular sieve is cooled to a temperature that is at least 50.degree.
C. lower than th used to contact the metalloaluminophosphate molecular
sieve in step b).
45. The method of claim 44 wherein the activated metalloaluminophosphate
molecular sieve is cooled to a temperature that is at least 100.degree.
C. lower than that of the gas used to contact the metalloaluminophosphate
molecular sieve in step b).
46. The method of claim 45 wherein the activated metalloaluminophosphate
molecular sieve is cooled to a temperature that is at least 150.degree.
C. lower than that of the gas used to contact the metalloaluminophosphate
molecular sieve in step b).
47. The method of claim 46 wherein the activated metalloaluminophosphate
molecular sieve is cooled to a temperature that is at least 200.degree.
C. lower than that of the gas used to contact the metalloaluminophosphate
molecular sieve in step b).
48. The method of claim 40 wherein the metalloaluminophosphate
molecular sieve is SAPO molecular sieve.
49. The method of claim 40 wherein contacting the metalloaluminophosphate
molecular sieve with a gas to remove the template and activate the
metalloaluminophosphate molecular sieve, and cooling the activated
metalloaluminophosphate molecular sieve is carried out in one or
more vessels.
50. A method of making a formulated metalloaluminophosphate molecular
sieve catalyst, the method comprising the steps of: a) mixing together
metalloaluminophosphate molecular sieve, matrix material, and a
binder to form a slurry b) removing water from the slurry to form
a preformed metalloaluminophosphate molecular sieve catalyst; c)
contacting the preformed metalloaluminophosphate molecular sieve
catalyst with a gas to form an activated metalloaluminophosphate
molecular sieve catalyst; and d) drying the activated metalloaluminophosphate
molecular sieve catalyst to a water content of not greater than
1.25 wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve catalyst.
51. The method of claim 50 wherein the activated metalloaluminophosphate
molecular sieve catalyst is dried to form an activated metalloaluminophosphate
molecular sieve catalyst having a water content of not greater than
1.0 wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve catalyst.
52. The method of claim 51 wherein the activated metalloaluminophosphate
molecular sieve catalyst is dried to form an activated metalloaluminophosphate
molecular sieve catalyst having a water content of not greater than
0.8 wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve catalyst.
53. The method of claim 52 wherein the activated metalloaluminophosphate
molecular sieve catalyst is dried to form an activated metalloaluminophosphate
molecular sieve catalyst having a water content of not greater than
0.5 wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve catalyst.
54. The method of claim 50 wherein the metalloaluminophosphate
molecular sieve is SAPO molecular sieve.
55. The method of claim 50 wherein the contacting of the preformed
metalloaluminophosphate molecular sieve catalyst and the drying
of the activated metalloaluminophosphate molecular sieve catalyst
is carried out in one or more vessels.
56. A method of storing activated metalloaluminophosphate molecular
sieve, the method comprising the steps of: a) providing a metalloaluminophosphate
molecular sieve having template therein; b) contacting the metalloaluminophosphate
molecular sieve with a gas containing water vapor at conditions
effective to remove the template and activate the metalloaluminophosphate
molecular sieve; and c) contacting the activated metalloaluminophosphate
molecular sieve with a gas at conditions effective to form an activated
catalyst having a water content of not greater than 1.25 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve; and d) storing the contacted metalloaluminophosphate molecular
sieve of step c) in an anhydrous environment.
57. The method of claim 56 wherein the activated metalloaluminophosphate
molecular sieve of step c) is contacted with a gas at conditions
effective to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 1.0 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
58. The method of claim 57 wherein the activated metalloaluminophosphate
molecular sieve of step c) is contacted with a gas at conditions
effective to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 0.8 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
59. The method of claim 58 wherein the activated metalloaluminophosphate
molecular sieve of step c) is contacted with a gas at conditions
effective to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 0.5 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
60. The method of claim 56 wherein the metalloaluminophosphate
molecular sieve is SAPO molecular sieve.
61. The method of claim 56 wherein the contacting of the activated
metalloaluminophosphate molecular sieve catalyst with a gas is carried
out in one or more vessels.
62. A method of storing activated metalloaluminophosphate molecular
sieve, the method comprising the steps of: a) providing a metalloaluminophosphate
molecular sieve having template therein; b) contacting the metalloaluminophosphate
molecular sieve with a gas containing water vapor at conditions
effective to remove the template and activate the metalloaluminophosphate
molecular sieve; and c) contacting the activated metalloaluminophosphate
molecular sieve with a gas at conditions effective to form an activated
catalyst having a water content of not greater than 1.25 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve; and d) storing the contacted activated metalloaluminophosphate
molecular sieve of step c) at a temperature of at least 150.degree.
C.
63. The method of claim 62 wherein the activated metalloaluminophosphate
molecular sieve of step c) is contacted with a gas at conditions
effective to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 1.0 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
64. The method of claim 63 wherein the activated metalloaluminophosphate
molecular sieve of step c) is contacted with a gas at conditions
effective to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 0.8 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
65. The method of claim 64 wherein the activated metalloaluminophosphate
molecular sieve of step c) is contacted with a gas at conditions
effective to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 0.5 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
66. The method of claim 62 wherein the metalloaluminophosphate
molecular sieve is SAPO molecular sieve.
67. The method of claim 62 wherein contacting the activated metalloaluminophosphate
molecular sieve with a gas is carried out in one or more vessels.
68. The method of claim 34 wherein the contacting step of c) occurs
in an environment having a relative water pressure not greater than
about 0.075.
69. The method of claim 40 wherein the cooling step of c) occurs
in an environment having a relative water pressure not greater than
about 0.075.
70. The method of claim 56 wherein the contacting step of c) occurs
in an environment having a relative water pressure not greater than
about 0.075.
71. The method of claim 62 wherein the contacting step of c) occurs
in an environment having a relative water pressure not greater than
about 0.075.
72. The method of claim 50 wherein the gas comprises air, steam,
or any combination thereof.
73. The method of claim 50 wherein the activated metalloaluminophosphate
molecular sieve catalyst is cooled by contacting with a dry gas
in an environment having a temperature of at least 225.degree. C.
74. The method of claim 73 wherein the dry gas is air, nitrogen,
helium, flue gas, or any combination thereof.
75. The method of claim 74 wherein the environment has a relative
water pressure of not greater than 0.075.
Molecular sieve description
FIELD OF THE INVENTION
This invention relates to a method of protecting the catalytic
activity of a metalloaluminophosphate molecular sieve. In particular,
this invention relates to a method of protecting the catalytic activity
of a SAPO molecular sieve by appropriately activating the molecular
sieve, preferably during the manufacturing process.
BACKGROUND OF THE INVENTION
Metalloaluminophosphate molecular sieves contain a pore system
that is essentially a network of uniform pores and empty cavities
connected to one another inside a crystalline or semi-crystalline
molecular structure. These pores and cavities catch molecules within
the molecular structure. The molecules that are caught have a size
equal to or less than the size of the pores and cavities. Molecules
of a larger size cannot physically enter into the molecular structure.
The pores and cavities of metalloaluminophosphate molecular sieves
are formed as a result of using template materials in the molecular
sieve manufacturing process. During the formation of the molecular
sieves themselves, a lattice type chemical structure is formed from
the alumina, silica or phosphorous components that are used in making
the metalloaluminophosphate molecular sieves. This lattice type
structure essentially wraps around the template material, with the
template material acting as a means of forming the pore structure
within the molecular sieve. The resulting molecular sieve may be
combined with other components for the benefit of adjusting various
properties of the molecular sieve or to form larger particles.
To make the molecular sieve suitable for use, the template must
be removed so that the pores and cavities are open to catch molecules,
either for the purpose of adsorbing the molecules from the environment
or to react the molecules to form a desired product. The reaction
occurs when the molecules come into contact with catalytic sites
located within the pore system, particularly within one or more
of the empty cavities or cages as sometimes called.
The template is conventionally removed from the molecular sieve
by calcining or burning out the template. An elution process can
also be used to remove the template, although calcination is preferred.
Once the template is removed, the molecular sieve is considered
to be activated or ready for use. The activated molecular sieve
has its pore system, including the empty cavities or cages open
to the immediate environment, and ready for use.
Activated metalloaluminophosphate molecular sieves, particularly
silicoaluminophosphate (SAPO) molecular sieves, that have catalytic
sites within their microporous structure have been found to be especially
sensitive to moisture. In general, significant exposure of the activated
molecular sieves to moisture has been found to deactivate the catalytic
activity of SAPO molecular sieves. Unfortunately, methods of protecting
activated SAPO molecular sieves against the harmful effects of moisture
are limited.
U.S. Pat. No. 6316683 B1 (Janssen et al.) discloses a method
of protecting catalytic activity of a SAPO molecular sieve by shielding
the internal active sites of the molecular sieve from contact with
moisture. The template itself can serve as the shield, or an anhydrous
blanket can serve as a shield for an activated sieve that does not
include template. It is desirable to shield the active sites, because
activated SAPO molecular sieves will exhibit a loss of catalytic
activity when exposed to moisture.
U.S. Pat. No. 4764269 (Edwards et al.) discloses a method of
protecting SAPO-37 catalyst from deactivating as a result of contact
with moisture. The catalyst is maintained under storage conditions
such that the organic template component of the molecular sieve
is retained in the SAPO-37 molecular sieve, until such time as the
catalyst is placed into a catalytic cracking unit. When the catalyst
is exposed to the FCC reaction conditions, wherein the reactor is
operated at 400.degree. to 600.degree. C. and the regenerator operated
at about 600.degree. to 850.degree. C., the organic template is
removed from the molecular sieve pore structure, and the catalyst
becomes activated for the cracking of hydrocarbons. According to
this procedure, there is little if any contact with moisture.
Mees et al., "Improvement of the Hydrothermal Stability of
SAPO-34" Chem. Commun., 2003 (1), 44-45 first published
as an advance article on the web Nov. 22 2002 discloses a method
of protecting SAPO-34 molecular sieve, based on a reversible reaction
of NH.sub.3 with acid sites of the sieve. The method transforms
a H.sup.+ -SAPO-34 into an NH.sub.4.sup.+ -SAPO-34 in reversible
way. The NH.sub.4.sup.+ -SAPO-34 is said to be able to withstand
severe steaming for an extended period of time without loss of structural
integrity and acidity.
As new large scale, commercial production facilities that use metalloaluminophosphate
molecular sieves in the production process continue to be implemented,
protecting the molecular sieves from loss of catalytic activity
as a result of contact with moisture continues to become an even
greater challenge. Such challenge is particularly of interest in
large scale commercial catalytic reaction systems, where the amount
of molecular sieve material that is used is several orders of magnitude
larger than typical pilot scale facilities. Such large scale systems
will typically require at least 10 tons, and up to as much as 500
tons, of molecular sieve to operate efficiently. Accordingly, additional
methods of protecting metalloaluminophosphate molecular sieves against
loss of catalytic activity are desired.
SUMMARY OF THE INVENTION
In one aspect, this invention provides methods, which assist in
the protection of metalloaluminophosphate molecular sieves against
loss of catalytic activity. These methods are particularly effective
as they are directed toward very early stages of where problems
start. In particular, the methods of this invention are particularly
useful in that they can be implemented at the manufacturing stage
of the molecular sieves. The molecular sieves themselves can be
activated for catalytic use, and protected for storing or transporting
prior to use. Alternatively, the molecular sieves can be formulated
into a preformed catalyst. The preformed catalyst can be activated
to form an activated catalyst, and activated catalyst is protected
from catalytic deactivation. The activated catalyst form is a preferred
embodiment, since it generally provides the most effective particle
size and hardness for commercial scale equipment.
In one embodiment, the invention provides a method of protecting
activated metalloaluminophosphate molecular sieve from catalytic
deactivation due to contact with water. The method includes providing
a metalloaluminophosphate molecular sieve having a template therein.
The metalloaluminophosphate molecular sieve is heated to remove
the template and form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than 1.25 wt %, based
on total weight of the activated metalloaluminophosphate molecular
sieve.
In another embodiment, there is provided a method of activating
and drying metalloaluminophosphate molecular sieve. Template is
removed from the metalloaluminophosphate molecular sieve to activate
the metalloaluminophosphate molecular sieve, and the activated metalloaluminophosphate
molecular sieve is dried to form an activated metalloaluminophosphate
molecular sieve. The dried sieve preferably has a water content
of not greater than 1.25 wt %, based on total weight of the activated
metalloaluminophosphate molecular sieve.
In yet another embodiment, a metalloaluminophosphate molecular
sieve having a template therein is heated with steam at a temperature
effective to remove the template and activate the metalloaluminophosphate
molecular sieve. The activated metalloaluminophosphate molecular
sieve is contacted with a gas in an environment at conditions effective
to form a metalloaluminophosphate molecular sieve having a very
low water content, preferably not greater than 1.25 wt %, based
on total weight of the metalloaluminophosphate molecular sieve.
Also provided in this invention is a method of making activated
metalloaluminophosphate molecular sieve. In one embodiment, a metalloaluminophosphate
molecular sieve having a template therein is provided. The metalloaluminophosphate
molecular sieve is contacted with a gas at conditions effective
to remove the template and activate the metalloaluminophosphate
molecular sieve. The activated metalloaluminophosphate molecular
sieve is then cooled to a temperature lower than that of the gas
used to contact the metalloaluminophosphate molecular sieve and
remove the template. The temperature at which the activate molecular
sieve is cooled is also effective to form an activated metalloaluminophosphate
molecular sieve having a water content of not greater than 1.25
wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve.
In another aspect of the invention, there is provided a method
of making a formulated metalloaluminophosphate molecular sieve catalyst.
In a preferred embodiment, a SAPO molecular sieve, matrix material,
and a binder are mixed together to form a slurry. Water is then
removed from the slurry to form a preformed metalloaluminophosphate
molecular sieve catalyst. The preformed metalloaluminophosphate
molecular sieve catalyst is contacted a gas, a gas containing steam,
or steam to form an activated metalloaluminophosphate molecular
sieve catalyst. The activated metalloaluminophosphate molecular
sieve catalyst is dried to a water content of not greater than 1.25
wt %, based on total weight of the activated metalloaluminophosphate
molecular sieve catalyst.
Also provided in this invention is a method of storing activated
metalloaluminophosphate molecular sieve. In one embodiment a metalloaluminophosphate
molecular sieve having template therein is contacted with a gas
containing water vapor at conditions effective to remove the template
and activate the metalloaluminophosphate molecular sieve. The activated
metalloaluminophosphate molecular sieve is contacted with a gas
at conditions effective to form an activated catalyst having a water
content of not greater than 1.25 wt %, based on total weight of
the activated metalloaluminophosphate molecular sieve, and the activated
metalloaluminophosphate molecular sieve is stored in an anhydrous
environment. In another embodiment of the invention, the activate
SAPO molecular sieve is stored at a temperature of at least 150.degree.
C. At such temperature, an anhydrous storage environment is not
necessary.
In the various embodiments of the invention, the heating and/or
activating of the molecular sieve or the formulated molecular sieve
and the cooling and/or drying of the activated sieve are carried
out in one or more vessels. Preferably, activating and cooling and/or
drying of the activated sieve are carried out in the same vessel.
BRIEF DESCRIPTION OF THE DRAWING
One embodiment of invention is shown in the attached FIGURE, which
shows the effect of temperature on removing water from a molecular
sieve.
DETAILED DESCRIPTION OF THE INVENTION
I. Minimizing Water Content of Activated Molecular Sieves
As noted above in the Background of the Invention, molecular sieves
are activated by removing template material from the pore structure
of the molecular sieves. Once activated, molecules can enter the
pore structure. If the activated molecular sieves contain active
catalyst sites within the pore structure, the catalyst sites are
available to come into contact with molecules entering the pore
structure and catalytically convert the molecules to a chemical
product. If the molecules entering the pore structure are water
molecules, and the molecular sieves are metalloaluminophosphate
molecular sieves, then the molecular sieves are likely to undergo
catalytic deactivation.
This invention provides methods that minimize the amount of water
molecules likely to enter into or remain in an activated metalloaluminophosphate
molecular sieve, thereby causing a significant loss of catalytic
activity. The methods of this invention can be applied during making,
storing and using activated metalloaluminophosphate molecular sieve
so as to protect against loss of catalyst activity. The methods
are particularly effective in protecting silicoaluminophosphate
(SAPO) molecular sieves from loss of catalytic activity due to contact
with moisture or water.
The methods of this invention are particularly beneficial, for
example, when incorporated into methods of activating the molecular
sieve so as to be ready for catalytic use. According to the methods
of this invention, molecular sieve appropriately activated, preferably
by heating, will contain only a minimal amount of water content,
and will remain in a catalytically active state for extended periods
of time.
According to one embodiment of this invention, a metalloaluminophosphate
molecular sieve, having template therein, is heated to remove the
template so as to form an activated metalloaluminophosphate molecular
sieve having a water content of not greater than about 1.25 wt %,
based on dry weight of the activated metalloaluminophosphate molecular
sieve. Preferably, the metalloaluminophosphate molecular sieve is
heated to remove the template so as to form an activated metalloaluminophosphate
molecular sieve having a water content of not greater than about
1.0 wt %, more preferably not greater than about 0.8 wt %, and most
preferably not greater than about 0.5 wt %, based on total weight
of the activated metalloaluminophosphate molecular sieve.
The water content of the activated material is preferably determined
by taking about a 40 mg sample of activated material and heating
the activated material by contacting with dry air at a temperature
of 600.degree. C. for at least one hour. The water content is calculated
as: ##EQU1##
where W is the weight of the activated material before drying,
and W.sub.s is the weight of the water removed after drying.
In one embodiment, the activated metalloaluminophosphate molecular
sieve is dried to a desirable moisture limit by contacting with
a gas in an environment in which the environment is at a temperature
of at least 225.degree. C. This drying or contacting step can be
performed as a cooling step, which follows a step to activate the
catalyst. Preferably the activated metalloaluminophosphate molecular
sieve is contacted with a gas in an environment having a temperature
of at least 250.degree. C., more preferably a temperature of at
least 275.degree. C., most preferably a temperature of at least
300.degree. C., and particularly a temperature of at least 340.degree.
C.
In another embodiment of the invention, drying of the activated
metalloaluminophosphate molecular sieve is carried out by cooling
with a dry gas. This cooling follows a conventional calcination
step. The calcination is carried out at conventional calcination
temperatures to remove template and activate the catalyst. Preferably,
calcination is carried out in the presence of water vapor, i.e.,
steam.
The drying or cooling step is desirably carried out at a temperature
that is at least about 50.degree. C. below that of the calcination
or activation step. Preferably, the drying or cooling step is carried
out at a temperature that is at least about 100.degree. C. below
that of the calcination or activation step; more preferably at least
about 150.degree. C. below that of the calcination or activation
step, and most preferably at least about 200.degree. C. below that
of the calcination or activation step.
In one embodiment this invention, the activated molecular sieve
is obtained in a relatively dry state by contacting with a gas in
a relatively dry environment. The gas is preferably selected from
the group consisting of air, nitrogen, helium, flue gas, and any
combination thereof, and the environment in which the gas contacts
the activated metalloaluminophosphate molecular sieve is substantially
low in water content. The water content of the environment preferably
has a relative water pressure that is sufficiently low so that little
water adsorption occurs. Relative water pressure (P.sub.r) in this
invention is defined as actual partial pressure of the water (P)
divided by saturated water pressure (P.sub.0) at a given temperature
below the critical temperature of water (374.degree. C.). The relative
water pressure is a measure of the wetness of the environment in
which the activated molecular sieve is dried or cooled. For example,
a P.sub.r =1 means 100% water saturation, and a P.sub.r =0 means
that it is completely dry.
In one embodiment of the invention, the activated molecular sieve
is obtained in a relatively dry state by contacting with a gas in
an environment in which the environment has a relative water pressure
of not greater than about 0.075. Preferably, the activated molecular
sieve is heated by contacting with a gas in an environment at a
relative water pressure of not greater than about 0.05 more preferably
not greater than about 0.025 and most preferably not greater than
about 0.001. It is also preferable that the step of contacting the
molecular sieve with a gas in the low water pressure environment
is carried out as part of the drying process, and in particular
prior to loading the activated catalyst into a storage or transport
container.
In another embodiment of the invention, the activated molecular
sieve is obtained in a relatively dry state by contacting with a
dry gas. The dry gas used in the drying or cooling step can be any
gas conventionally used to dry molecular sieves. Examples of such
dry gases include air, nitrogen, helium, flue gas (i.e., a combustion
product gas low in moisture content), or any combination thereof.
Dry air is preferred. In particular, dry gases having a relative
water pressure of not greater than about 0.075 are desired, preferably
not greater than about 0.05 more preferably not greater than about
0.025 and most preferably not greater than about 0.001.
In another embodiment of the invention, a metalloaluminophosphate
molecular sieve is activated so as to obtain a hardened, activated
molecular sieve catalyst that is acceptably dry. Hardness of the
catalyst can be determined by measuring attrition resistance using
any conventional method. One such method is the well known Jet Cup
Attrition Method. This is also commonly referred to as the Davison
Attrition Index or Davison Index (DI). See, e.g., U.S. Pat. Nos.
5547564 and 5364516. The molecular sieve or catalyst composition
of this invention is desirably hard enough to provide protection
against physical damage during transportation or storing, and preferably
hard enough to be introduced into a process unit to provide protection
against physical damage during operation.
In one aspect, the invention provides heating the metalloaluminophosphate
molecular sieve under conditions effective to obtain a hardened,
activated molecular sieve catalyst having a Davison Index of not
greater than 15. Preferably, the metalloaluminophosphate molecular
sieve is heated under conditions effective to obtain a hardened,
activated molecular sieve catalyst having a Davison Index of not
greater than 10 more preferably not greater than 5 and most preferably
not greater than 3.
In general, the lower the Davison Index, the harder the composition.
In this invention, the Davison Index is determined as follows:
A sample of molecular sieve with binder material is analyzed to
determine the average diameter in microns. The sample is then subjected
to a standard 20 minute test in a Fluid Catalyst Attrition Apparatus
using a hardened steel jet cup having a precision bored orifice,
using an air flow of 18 liters per minute. Hardness is determined
as a result of the amount of catalyst particles that are broken
apart during the test. The greater the number of particles that
are broken apart during the test, the less hard the catalyst. The
Davison Index is calculated as ##EQU2##
II. Types of Molecular Sieves
This invention is effective in protecting any molecular sieve containing
active catalytic sites from deactivating due to contact with water
molecules. 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.
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).
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.
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..
Molecular sieves used herein are preferably metalloaluminophosphate
molecular sieves that have a molecular framework that include [AlO.sub.4
] and [PO.sub.4 ] tetrahedral units, such as metal containing aluminophosphates
(AlPO). In one embodiment, the metalloaluminophosphate molecular
sieves include [AlO.sub.4 ], [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 (MnAPSO),
U.S. Pat. Nos. 5345011 and 6156931 (MnAPO), U.S. Pat. No. 4737353
(BeAPSO), U.S. Pat. No. 4940570 (BeAPO), U.S. Pat. Nos. 4801309
4684617 and 4880520 (TiAPSO), U.S. Pat. Nos. 4500651 4551236
and 4605492 (TiAPO), U.S. Pat. Nos. 4824554 4744970 (CoAPSO),
U.S. Pat. No. 4735806 (GaAPSO) EP-A-0 293 937 (QAPSO, where Q
is framework oxide unit [QO.sub.2 ]), as well as U.S. Pat. Nos.
4567029 4686093 4781814 4793984 4801364 4853197
4917876 4952384 4956164 4956165 4973785 5241093
5493066 and 5675050 all of which are herein fully incorporated
by reference.
Other molecular sieves include those described in R. Szostak, Handbook
of Molecular Sieves, Van Nostrand Reinhold, New York, N.Y. (1992),
which is herein fully incorporated by reference.
The more preferred molecular sieves 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, VIIB, 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.
In one embodiment, the metalloaluminophosphate molecular sieve
is represented, on an anhydrous basis, by the formula:
wherein R represents at least one templating agent, preferably
an organic templating agent; m is the number of moles of R per mole
of (M.sub.x Al.sub.y P.sub.z)O.sub.2 and 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 the group consisting of
Group IA, IIA, IB, IIIB, IVB, VB, VIIB, VIIB, VIIIB and Lanthanide's
of the Periodic Table of Elements. Preferably M is one or more metals
selected from 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.
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.
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 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 AlPO-34 and metal containing
derivatives thereof, such as one or a combination of SAPO-18 SAPO-34
AlPO-34 AlPO-18 and metal containing derivatives thereof, and
especially one or a combination of SAPO-34 AlPO-18 and metal containing
derivatives thereof.
In an embodiment, the molecular sieve is an intergrowth material
having two or more distinct crystalline phases within one molecular
sieve composition. In particular, intergrowth molecular sieves are
described in 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.
III. Methods of Making Molecular Sieve Crystals and Formulated
Molecular Sieve Catalyst
A. Making Molecular Sieve Crystals
Generally, molecular sieves (i.e., molecular sieve crystals) 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 one or more templating
agents, is placed in a sealed pressure vessel. The vessel is 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.
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.
Non-limiting examples of aluminum sources include aluminum alkoxides,
for example aluminum isopropoxide, aluminum phosphate, aluminum
hydroxide, sodium aluminate, pseudo-boehmite, gibbsite and aluminum
trichloride, or any combination thereof. A convenient source of
aluminum is pseudo-boehmite, particularly when producing a silicoaluminophosphate
molecular sieve.
Non-limiting examples of phosphorus sources, which may also include
aluminum-containing phosphorus compositions, include phosphoric
acid, organic phosphates such as triethyl phosphate, and crystalline
or amorphous aluminophosphates such as AlPO.sub.4 phosphorus salts,
or combinations thereof. A convenient source of phosphorus is phosphoric
acid, particularly when producing a silicoaluminophosphate.
In general, templating agents or templates include compounds that
contain elements of Group 15 of the Periodic Table of Elements,
particularly nitrogen, phosphorus, arsenic and antimony. Typical
templates 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 templates are nitrogen-containing
compounds, such as amines, quaternary ammonium compounds and combinations
thereof. Suitable quaternary ammonium compounds are represented
by the general formula R.sub.4 N.sup.+, where each R is hydrogen
or a hydrocarbyl or substituted hydrocarbyl group, preferably an
alkyl group or an aryl group having from 1 to 10 carbon atoms.
Non-limiting examples of templates 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.
Preferred templates are selected from the group consisting of tetraethyl
ammonium salts, cyclopentylamine, aminomethyl cyclohexane, piperidine,
triethylamine, cyclohexylamine, tri-ethyl hydroxyethylamine, morpholine,
dipropylamine (DPA), pyridine, isopropylamine, heated degraded forms
thereof, and combinations thereof.
The pH of the synthesis mixture containing at a minimum a silicon,
aluminum, optionally a phosphorus composition, and a templating
agent, is generally in the range of from 2 to 10 such as from 4
to 9 for example from 5 to 8.
Generally, the synthesis mixture described above is sealed in a
vessel and heated, preferably under autogenous pressure, to a temperature
in the range of from about 80.degree. C. to about 250.degree. C.,
such as from about 100.degree. C. to about 250.degree. C., for example
from about 125.degree. C. to about 225.degree. C., such as from
about 150.degree. C. to about 180.degree. C.
In one embodiment, the synthesis of molecular sieve crystalline
particles is aided by seeds from another or the same framework type
molecular sieve.
The time required to form the crystalline particles 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.
One method for crystallization involves subjecting an aqueous reaction
mixture containing an excess amount of a templating agent to crystallization
under hydrothermal conditions, establishing an equilibrium between
molecular sieve formation and dissolution, and then, removing some
of the excess templating agent and/or organic base to inhibit dissolution
of the molecular sieve. See, for example, U.S. Pat. No. 5296208
which is herein fully incorporated by reference.
Other methods for synthesizing molecular sieves or modifying molecular
sieves are described in U.S. Pat. No. 5879655 (controlling the
ratio of the templating agent to phosphorus), U.S. Pat. No. 6005155
(use of a modifier without a salt), U.S. Pat. No. 5475182 (acid
extraction), U.S. Pat. No. 5962762 (treatment with transition
metal), U.S. Pat. Nos. 5925586 and 6153552 (phosphorus modified),
U.S. Pat. No. 5925800 (monolith supported), U.S. Pat. No. 5932512
(fluorine treated), U.S. Pat. No. 6046373 (electromagnetic wave
treated or modified), U.S. Pat. No. 6051746 (polynuclear aromatic
modifier), U.S. Pat. No. 6225254 (heating template), PCT WO 01/36329
published May 25 2001 (surfactant synthesis), PCT WO 01/25151 published
Apr. 12 2001 (staged acid addition), PCT WO 01/60746 published
Aug. 23 2001 (silicon oil), U.S. patent application Ser. No. 09/929949
filed Aug. 15 2001 (cooling molecular sieve), U.S. patent application
Ser. No. 09/615526 filed Jul. 13 2000 (metal impregnation including
copper), U.S. patent application Ser. No. 09/672469 filed Sep.
28 2000 (conductive microfilter), and U.S. patent application Ser.
No. 09/754812 filed Jan. 4 2001(freeze drying the molecular sieve),
which are all herein fully incorporated by reference.
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 particle 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, the wet filter cake may be formulated
into a catalyst composition directly, that is without any drying,
or after only partial drying.
B. Making Formulated Molecular Sieve Catalyst
1. Components of Formulated Molecular Sieve Catalyst
Molecular sieve catalyst, which contains molecular sieve crystal
product, and typically binder and matrix materials, is also referred
to as a formulated catalyst. It is made by mixing together molecular
sieve crystals (which includes template) and a liquid, optionally
with matrix material and/or binder, to form a slurry. The slurry
is then dried (i.e., liquid is removed), without completely removing
the template from the molecular sieve. Since this dried molecular
sieve catalyst includes template, it has not been activated, and
is considered a preformed catalyst. The catalyst in this form is
resistant to catalytic loss by contact with moisture or water. However,
the preformed catalyst must be activated before use, and this invention
provides appropriate methods of activating, preferably by further
heat treatment, to maintain a low water content within the activated
catalyst.
The liquid used to form the slurry can be any liquid conventionally
used in formulating molecular sieve catalysts. Non-limiting examples
of suitable liquids include water, alcohol, ketones, aldehydes,
esters, or a combination thereof. Water is a preferred liquid.
Matrix materials are optionally included in the slurry used to
make the formulated molecular sieve catalyst of this invention.
Such materials are typically effective as thermal sinks assisting
in shielding heat from the catalyst composition, for example, during
regeneration. They can further act to densify the catalyst composition,
increase catalyst strength such as crush strength and attrition
resistance, and to control the rate of conversion in a particular
process. Non-limiting examples of matrix materials include one or
more of: rare earth metals, metal oxides including titania, zirconia,
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 one embodiment, matrix materials are natural clays, such as
those from the families of montmorillonite and kaolin. These natural
clays include kaolins known as, for example, Dixie, McNamee, Georgia
and Florida clays. Non-limiting examples of other matrix materials
include: halloysite, kaolinite, dickite, nacrite, or anauxite. Optionally,
the matrix material, preferably any of the clays, are calcined,
acid treated, and/or chemical treated before being used as a slurry
component. Under the optional calcination treatment, the matrix
material will still be considered virgin material as long as the
material has not been previously used in a catalyst formulation.
In a particular embodiment, the matrix material is a clay or a
clay-type composition, preferably a clay or clay-type composition
having a low iron or titania content, and most preferably the matrix
material is kaolin. Kaolin has been found to form a pumpable, high
solid content slurry; it has a low fresh surface area, and it packs
together easily due to its platelet structure.
Preferably, the matrix material, particularly clay, and preferably
kaolin, has an average particle size of from about 0.05 .mu.m to
about 0.75 .mu.m; more preferably from about 0.1 .mu.m to about
0.6 .mu.m. It is also desirable that the matrix material have a
d.sub.90 particle size distribution of less than about 1.5 .mu.m,
preferably less than about 1 .mu.m.
Binders are also optionally included in the slurry used to make
the formulated molecular sieve catalysts of this invention. Such
materials act like glue, binding together the molecular sieve crystals
and other materials, to form a formulated catalyst composition.
Non-limiting examples of binders include various types of inorganic
oxide sols such as hydrated aluminas, silicas, and/or other inorganic
oxide sols. In one embodiment of the invention, the binder is an
alumina-containing sol, preferably aluminium chlorohydrate. Upon
calcining, the inorganic oxide sol, is converted into an inorganic
oxide matrix component, which is particularly effective in forming
a hardened molecular sieve catalyst composition. For example, an
alumina sol will convert to an aluminium oxide matrix following
heat treatment.
Aluminium chlorohydrate, a hydroxylated aluminium based sol containing
a chloride counter ion, also known as aluminium chlorohydrol, has
the general formula
wherein m is 1 to 20 n is 1 to 8 o is 5 to 40 p is 2 to 15
and x is 0 to 30. In one embodiment, the binder is Al.sub.13 O.sub.4
(OH).sub.24 Cl.sub.7.multidot.12(H.sub.2 O) as is described in G.
M. Wolterman, et al., Stud. Surf. Sci. and Catal., 76 pages 105-144
Elsevier, Amsterdam, 1993 which is herein incorporated by reference.
In another embodiment, one or more binders are present in combination
with one or more other non-limiting examples of alumina materials
such as aluminium oxyhydroxide, .gamma.-alumina, boehmite and transitional
aluminas such as .alpha.-alumina, .beta.-alumina, .gamma.-alumina,
.delta.-alumina, .epsilon.-alumina, .kappa.-alumina, and .rho.-alumina,
aluminium trihydroxide, such as gibbsite, bayerite, nordstrandite,
doyelite, and mixtures thereof.
In another embodiment, the binders are alumina sols, predominantly
comprising aluminium oxide, optionally including silicon. In yet
another embodiment, the binders are peptised alumina made by treating
alumina hydrates such as pseudobohemite, with an acid, preferably
a non-halogen acid, to prepare sols or aluminium ion solutions.
Non-limiting examples of commercially available colloidal alumina
sols include Nalco 8676 available from Nalco Chemical Co., Naperville,
Ill., and Nyacol available from the Nyacol Nano Technology Inc.,
Boston, Mass.
If binder is not used in making the molecular sieve catalyst, the
catalyst is considered a binderless catalyst. If binder is used,
the amount of binder used to prepare the molecular sieve catalyst
ranges from about 2% by weight to about 30% by weight, based on
the total weight of the binder, the molecular sieve, and optionally
included matrix material, excluding the liquid (i.e., after drying).
Preferably the amount of binder used to prepare the molecular sieve
catalyst ranges from about 5% by weight to about 20% by weight,
more preferably from about 7% by weight to about 15% by weight,
based on the total weight of the binder, the molecular sieve, and
optionally included matrix material, excluding the liquid (i.e.,
after drying).
2. Making a Slurry with Molecular Sieve Crystals
The molecular sieve crystals are mixed with liquid, and the optional
matrix material and/or binder, using conventional techniques to
form a slurry. The components can be mixed in any order, and the
mixture is thoroughly stirred to form the slurry. The more thorough
the stirring, the better the consistency of the slurry.
The mixing of the slurry is preferably sufficient to break any
aggregates or large particles into smaller, more uniform particles.
In general, the more vigorous the mixing, the smaller the catalyst
particles formed in the slurry. Mixing using high-shear mixers is
preferred. In general, high-shear mixers are capable of rotating
at speeds of at least about 3000 rpm laboratory scale equivalent.
Solids particle size of the slurry can be indirectly determined
by measuring the viscosity of the slurry. In general, the higher
the viscosity, the smaller the solids particle size in the slurry.
The viscosity of the slurry should not be too high, so that mixing
is not effective in breaking apart large particles, or too low,
so that drying will not produce acceptable particle formation.
In one embodiment, the slurry has a viscosity of from about 100
cP (0.1 Pa/sec) to about 9500 cP (9.5 Pa/sec), as measured using
a Brookfield LV-DVE viscometer with a No. 3 spindle at 10 rpm. Preferably,
the slurry has a viscosity of from about 200 cP (0.2 Pa/sec) to
about 8500 cP (8.5 Pa/sec), and more preferably from about 350
cP (0.375 Pa/sec) to about 8000 cP (8 Pa/sec), as measured using
a Brookfield LV-DVE viscometer with a No. 3 spindle at 10 rpm.
In another embodiment, the slurry has a solids content of from
about 10 wt % to about 75 wt %, based on total weight of the slurry.
Preferably the slurry has a solids content of from about 15 wt %
to about 70 wt %, more preferably from about 20 wt % to about 65
wt %, based on the total weight of the slurry. The solids content
can be measured using any conventional means. However, a CEM MAS
700 microwave muffle furnace is particularly preferred to give results
consistent with the values recited herein.
In one embodiment, the slurry used to make the formulated molecular
sieve catalyst contains binder and matrix material at a weight ratio
of from 0:1 to 1:1. Preferably, the slurry used to make the molecular
sieve catalyst contains binder and matrix material at a weight ratio
of from 1:15 to 1:2 more preferably 1:10 to 1:2 and most preferably
1:6 to 1:1. In case where binders are not used, the molecular sieve
component itself acts as a binder.
3. Making a Preformed Catalyst
Water is removed from the slurry containing the molecular sieve
crystals to form a preformed molecular sieve catalyst. Preferably,
the slurry is fed to a forming unit that produces the preformed
molecular sieve catalyst composition. The forming unit may be any
conventional unit, such as a spray dryer, pelletizer, extruder,
etc. In a preferred embodiment, the forming unit is spray dryer,
which removes water from the slurry by a heating or drying process.
Preferably, the forming unit is maintained at a temperature sufficient
to remove a majority of the liquid from the slurry.
When a spray dryer is used as the forming (or drying) unit, typically,
the slurry of the molecular sieve particles, and optional matrix
material and/or binder, is fed to the spray drying unit along with
a drying gas. The drying gas contacts the slurry and acts to remove
water to form the preformed molecular sieve catalyst. Conventional
drying conditions can be used. Such conditions include an average
inlet temperature ranging from about 150.degree. C. to about 550.degree.
C., and an average outlet temperature ranging from about 100.degree.
C. to about 250.degree. C.
During spray drying, the slurry is passed through a nozzle distributing
the slurry into small droplets, resembling an aerosol spray, into
a drying chamber where atomization occurs. Atomization is achieved
by forcing the slurry through a single nozzle or multiple nozzles
with a pressure drop in the range of from about 100 psia to about
1000 psia (about 690 kPaa to about 6895 kPaa). In another embodiment,
the slurry is fed through a single nozzle or multiple nozzles along
with an atomization or contacting fluid such as air, steam, flue
gas, or any other suitable gas.
In yet another embodiment, the slurry that is used to make the
preformed catalyst is directed to the perimeter of a spinning wheel
that distributes the slurry into small droplets. The size of the
droplets is controlled by one or more factors including slurry viscosity,
surface tension, flow rate, pressure, and temperature of the slurry;
the shape and dimension of the nozzle(s); or 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 preformed molecular
sieve catalyst composition. An example of a conventional spray drying
process is described in U.S. Pat. No. 4946814 which is incorporated
herein by reference.
C. Protecting Molecular Sieve and Catalyst from Deactivation
The molecular sieve material of this invention is protected by
appropriate activation to remove template from the molecular sieve
and minimize water content in the activated material. The molecular
sieve crystals themselves can be activated for catalytic use or
for storing or transporting prior to use. However, it is preferred
that the molecular sieves be formulated into a preformed catalyst,
then activated, since the sieves are typically most useful as a
formulated product. The formulated product generally provides the
most effective particle size and hardness for commercial scale equipment.
The activated molecular sieve material is protected from catalytic
deactivation by maintaining the activated material at a low moisture
content, preferably a water content of not greater than 1.25 wt
%, based on total weight of the material, as described above (e.g.,
preferably not greater than 1.0 wt %, more preferably not greater
than 0.8 wt %, and most preferably not greater than 0.5 wt %). This
is achieved by limiting or preventing water from contacting the
activated molecular sieve material at a temperature lower than the
critical temperature of water.
In one embodiment of the invention, the molecular sieve material
is activated by removing the template by heat. In a preferred embodiment,
the heat is sufficient to remove water that is formed as a result
of the combustion of the template. Preferably, the molecular sieve
material is heated at a temperature greater than the critical temperature
of water. At this temperature water formed during the combustion
process will not condense or be retained by the molecular sieve.
Preferably, the template is removed by contacting with steam at
a temperature greater than the critical temperature of water.
Heating to remove template and activate the molecular sieve is
generally referred to in this invention as calcination. Conventional
calcination devices can be used. Such devices include rotary calciners,
fluid bed calciners, batch ovens, and the like. Calcination time
is typically dependent on the degree of hardening of the molecular
sieve catalyst composition and the temperature.
Conventional calcination temperatures are effective to remove template
materials and to activate the molecular sieve catalyst of this invention.
Such temperatures are generally in the range from about 400.degree.
C. to about 1000.degree. C., preferably from about 500.degree.
C. to about 800.degree. C., and most preferably from about 550.degree.
C. to about 700.degree. C.
Following heat activation by calcining for example, the activated
molecular sieve is cooled, since it will generally be at a temperature
that is too high for immediately loading into a container. In a
preferred embodiment, the activated molecular sieve is cooled by
contacting with a gas, preferably a dry gas, so that water is prevented
from entering the pores of the molecular sieve. Preferably, the
gas is a dry gas, more preferably a dry, inert gas conventionally
used to dry molecular sieves as described above (e.g., air, nitrogen,
helium, flue gas, or a combination thereof at a relative water pressure
of not greater than about 0.075 preferably not greater than about
0.05 more preferably not greater than about 0.025 and most preferably
not greater than about 0.001). As also described above, it is preferable
that the activated be cooled by contacting the gas in an environment
at a temperature of at least about 225.degree. C. (e.g., desirably
at least 250.degree. C., preferably at least 275.degree. C., more
preferably at least 300.degree. C., and most preferably at least
340.degree. C.). This activation and subsequent cooling or drying
of the molecular sieve can be carried out in separate heating units
or in the same heating unit, though in different regions of that
unit.
The method of protecting activated molecular sieve, i.e., metalloaluminophosphate
molecular sieve, from catalytic deactivation due to contact with
water can be effectively incorporated into methods for making and
activating molecular sieve particles, as well as methods for making
and activating formulated molecular sieve catalysts. In a preferred
embodiment, the method of protecting activated molecular sieves
is incorporated into methods for making and activating formulated
molecular sieve catalysts.
In one embodiment, formulated catalyst is made by mixing together
metalloaluminophosphate molecular sieve, matrix material, and a
binder to form a slurry. Water is removed from the slurry to form
a preformed molecular sieve catalyst. If desired, the preformed
catalyst can be stored until a later date, when activation is to
occur. In the preformed state, the catalyst is generally protected
against deactivation as a result of contact with moisture.
In one embodiment, the preformed catalyst is activated by contacting
with air or air and steam to remove template material. In order
to protect the activated catalyst from deactivation, it is dried
or cooled in a manner so that no significant amount of water is
retained by the activated catalyst. The activated catalyst can then
be appropriately stored for an extended period of time, if desired.
Preferably, the preformed catalyst is activated by contacting with
an air composition comprising at least about 1 wt % steam, more
preferably at least about 5 wt %, and most preferably at least about
10 wt % steam, based on total weight of the air composition.
IV. Storing the Molecular Sieves or Formulated Molecular Sieve
Catalyst
The activated molecular sieve is stored so that there is not a
substantial loss in catalytic activity. Catalytic activity according
to this invention is defined by a methanol uptake index. The methanol
uptake index is defined as the ratio of the methanol adsorption
capacity (wt %) of an activated metalloaluminophosphate molecular
sieve at the time of measurement to the maximum methanol adsorption
capacity (wt %) of the activated molecular sieve (i.e., the initial
methanol adsorption capacity after activation). For example, this
means that an activated molecular sieve that has no loss in catalytic
activity will have a methanol uptake index of 1 whereas an activated
molecular sieve that has little to no catalytic activity will have
a methanol uptake index of 0.
Techniques for measuring methanol adsorption capacity are known
to those of ordinary skill in the art. In a preferred technique,
about 5 mg of sample is introduced into a thermogravimetric analyzer
(TGA). The sample is subjected to a heat treatment process, which
includes: (1) heating from room temperature to 450.degree. C., with
a heat up rate of 20.degree. C./min. in air; (2) holding at 450.degree.
C. for 40 min. in air; and cooling to 30.degree. C. in air. After
the sample has reached 30.degree. C., the air flow is switched to
a methanol containing nitrogen flow with a methanol partial pressure
of 0.09 atm. The sample is contacted with this nitrogen/methanol
mixture for 180 minutes. The methanol adsorption capacity is the
weight percent weight increase after the 180 minutes contact with
the methanol vapor.
In one embodiment of the invention, the activated molecular sieve
material is loaded into a container before the catalytic activity
is significantly lost. Desirably, the molecular sieve material that
is loaded into the container has a methanol uptake index of at least
0.15. Preferably, the molecular sieve material that is loaded into
the container has a methanol uptake index of at least 0.4 more
preferably at least 0.6 and most preferably at least 0.8.
In another embodiment of the invention, the activated molecular
sieve material that is low in water content is loaded into a container
at a temperature of at least 225.degree. C. Preferably the catalyst
is loaded into a container at a temperature of at least 250.degree.
C., more preferably at a temperature of at least 275.degree. C.,
most preferably at a temperature of at least 300.degree. C., and
particularly at a temperature of at least 340.degree. C.
In yet another embodiment of the invention, the container provides
an anhydrous environment. Such an environment can be provided by
covering the sieve loaded into a container with a gas or liquid
blanket under anhydrous conditions. As provided herein, the anhydrous
gas or liquid blanket will have no more than a limited amount of
water. The anhydrous gas blanket can be provided under vacuum conditions
or under atmospheric or greater pressure conditions, and will desirably
have not greater than about 1.2 volume percent water, preferably
not greater than about 0.2 volume percent water, and more preferably
not greater than about 0.02 volume percent water. The anhydrous
liquid blanket will desirably have not greater than about 200 ppm
water, preferably not greater than about 100 ppm water, and more
preferably not greater than about 50 ppm water. The anhydrous environment
can be applied during storage, transport or loading of the activated
material.
The anhydrous gas blanket is a gas under standard temperature and
pressure conditions and does not react to any significant degree
with the molecular sieve structure. The gas is preferably selected
from the group consisting of nitrogen, helium, CO, CO.sub.2 H.sub.2
argon, O.sub.2 light alkanes (especially C.sub.1 -C.sub.4 alkanes,
particularly methane and ethane), cyclo-alkanes and mixtures thereof,
e.g. air. Air is a preferred gas. The gas blanket can be maintained
at any pressure, including under vacuum or at pressures above standard,
even if the gas becomes liquid at pressures above standard, as long
as the conditions remain anhydrous.
The anhydrous liquid blanket is a liquid under standard temperature
and pressure conditions, and does not react to any significant degree
with the molecular sieve structure. The liquid is preferably selected
from the group consisting of alkanes, cyclo-alkanes, C.sub.6 -C.sub.30
aromatics, alcohols, particularly C.sub.4 + branched alcohols.
V. Uses of the Molecular Sieves
The molecular sieves 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.
Preferred processes include processes for converting naphtha to
highly aromatic mixtures; converting light olefin(s) to gasoline,
distillates and lubricants; converting oxygenates to olefin(s);
converting light paraffins to olefins and/or aromatics; and converting
unsaturated hydrocarbons (ethylene and/or acetylene) to aldehydes
for conversion into alcohols, acids and esters.
The most preferred process of the invention is a process directed
to the conversion of a feedstock to one or more olefin(s). Typically,
the feedstock contains one or more aliphatic-containing compounds
such that the aliphatic moiety contains from 1 to about 50 carbon
atoms, such as from 1 to 20 carbon atoms, for example from 1 to
10 carbon atoms, and particularly from 1 to 4 carbon atoms.
Non-limiting examples of aliphatic-containing compounds include
alcohols such as methanol and ethanol, alkyl mercaptans such as
methyl mercaptan and ethyl mercaptan, alkyl sulfides such as methyl
sulfide, alkylamines such as methylamine, alkyl ethers such as dimethyl
ether, diethyl ether and methylethyl ether, alkyl halides such as
methyl chloride and ethyl chloride, alkyl ketones such as dimethyl
ketone, formaldehydes, and various acids such as acetic acid.
In a preferred embodiment of the process of the invention, the
feedstock contains one or more oxygenates, more specifically, one
or more organic compound(s) containing at least one oxygen atom.
In the most preferred embodiment of the process of invention, the
oxygenate in the feedstock is one or more alcohol(s), preferably
aliphatic alcohol(s) where the aliphatic moiety of the alcohol(s)
has from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms,
and most preferably from 1 to 4 carbon atoms. The alcohols useful
as feedstock in the process of the invention include lower straight
and branched chain aliphatic alcohols and their unsaturated counterparts.
Non-limiting examples of oxygenates include methanol, ethanol,
n-propanol, isopropanol, methyl ethyl ether, dimethyl ether, diethyl
ether, di-isopropyl ether, formaldehyde, dimethyl carbonate, dimethyl
ketone, acetic acid, and mixtures thereof.
In the most preferred embodiment, the feedstock is selected from
one or more of methanol, ethanol, dimethyl ether, diethyl ether
or a combination thereof, more preferably methanol and dimethyl
ether, and most preferably methanol.
The various feedstocks discussed above, particularly a feedstock
containing an oxygenate, more particularly a feedstock containing
an alcohol, is converted primarily into one or more olefin(s). The
olefin(s) produced from the feedstock typically have from 2 to 30
carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2
to 6 carbon atoms, still more preferably 2 to 4 carbons atoms, and
most preferably are ethylene and/or propylene.
The catalyst composition of the invention is particularly useful
in the process that is generally referred to as the gas-to-olefins
(GTO) process or, alternatively, the methanol-to-olefins (MTO) process.
In this process, an oxygenated feedstock, most preferably a methanol-containing
feedstock, is converted in the presence of a molecular sieve catalyst
composition into one or more olefin(s), preferably and predominantly,
ethylene and/or propylene.
Using the catalyst composition of the invention for the conversion
of a feedstock, preferably a feedstock containing one or more oxygenates,
the amount of olefin(s) produced based on the total weight of hydrocarbon
produced is greater than 50 weight percent, typically greater than
60 weight percent, such as greater than 70 weight percent, and preferably
greater than 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.
In addition to the oxygenate component, such as methanol, the feedstock
may contains one or more diluent(s), which are generally non-reactive
to the feedstock or molecular sieve catalyst composition and are
typically used to reduce the concentration of the feedstock. Non-limiting
examples of diluents include helium, argon, nitrogen, carbon monoxide,
carbon dioxide, water, essentially non-reactive paraffins (especially
alkanes such as methane, ethane, and propane), essentially non-reactive
aromatic compounds, and mixtures thereof. The most preferred diluents
are water and nitrogen, with water being particularly preferred.
The diluent, for example water, may be used either in a liquid
or a vapor form, or a combination thereof. The diluent may be either
added directly to the feedstock entering a reactor or added directly
to the reactor, or added with the molecular sieve catalyst composition.
The present process can be conducted over a wide range of temperatures,
such as in the range of from about 200.degree. C. to about 1000.degree.
C., for example from about 250.degree. C. to about 800.degree. C.,
including from about 250.degree. C. to about 750.degree. C., conveniently
from about 300.degree. C. to about 650.degree. C., typically from
about 350.degree. C. to about 600.degree. C. and particularly from
about 350.degree. C. to about 550.degree. C.
Similarly, the present process can be conducted over a wide range
of pressures including autogenous pressure. Typically the partial
pressure of the feedstock exclusive of any diluent therein employed
in the process is in the range of from about 0.1 kPaa to about 5
MPaa, such as from about 5 kpaa to about 1 MPaa, and conveniently
from about 20 kPaa to about 500 kPaa.
The weight hourly space velocity (WHSV), defined as the total weight
of feedstock excluding any diluents per hour per weight of molecular
sieve in the catalyst composition, typically ranges from about 1
hr.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.
Where the process is conducted in a fluidized bed, the superficial
gas velocity (SGV) of the feedstock including diluent and reaction
products within the reactor system, and particularly within a riser
reactor(s), is at least 0.1 meter per second (m/sec), such as greater
than 0.5 m/sec, such as greater than 1 m/sec, for example greater
than 2 m/sec, conveniently greater than 3 m/sec, and typically greater
than 4 m/sec. See for example U.S. patent application Ser. No. 09/708753
filed Nov. 8 2000 which is herein incorporated by reference.
The process of the invention is conveniently conducted as a fixed
bed process, or more typically as a fluidized bed process. (including
a turbulent bed process), such as a continuous fluidized bed process,
and particularly a continuous high velocity fluidized bed process.
The process can take place in a variety of catalytic reactors such
as hybrid reactors that have a dense bed or fixed bed reaction zones
and/or fast fluidized bed reaction zones coupled together, circulating
fluidized bed reactors, riser reactors, and the like. Suitable conventional
reactor types are described in for example U.S. Pat. No. 4076796
U.S. Pat. No. 6287522 (dual riser), and Fluidization Engineering,
D. Kunii and O. Levenspiel, Robert E. Krieger Publishing Company,
New York, N.Y. 1977 which are all herein fully incorporated by
reference.
The preferred reactor types are riser reactors generally described
in Riser Reactor, Fluidization and Fluid-Particle Systems, pages
48 to 59 F. A. Zenz and D. F. Othmo, Reinhold Publishing Corporation,
New York, 1960 and U.S. Pat. No. 6166282 (fast-fluidized bed
reactor), and U.S. patent application Ser. No. 09/564613 filed
May 4 2000 (multiple riser reactor), which are all herein fully
incorporated by reference.
In one practical embodiment, the process is conducted as a fluidized
bed process or high velocity fluidized bed process utilizing a reactor
system, a regeneration system and a recovery system.
In such a process the reactor system 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.
In an embodiment, the amount of fresh feedstock fed as a liquid
and/or a vapor to the reactor system is in the range of from 0.1
weight percent to about 85 weight percent, such as from about 1
weight percent to about 75 weight percent, more typically from about
5 weight percent to about 65 weight percent based on the total weight
of the feedstock including any diluent contained therein. The liquid
and vapor feedstocks may be the same composition, or may contain
varying proportions of the same or different feedstocks with the
same or different diluents.
The feedstock entering the reactor system is preferably converted,
partially or fully, in the first reactor zone into a gaseous effluent
that enters the disengaging vessel along with the coked catalyst
composition. In the preferred embodiment, cyclone(s) are provided
within the disengaging vessel to separate the coked catalyst composition
from the gaseous effluent containing one or more olefin(s) within
the disengaging vessel. Although cyclones are preferred, gravity
effects within the disengaging vessel can also be used to separate
the catalyst composition from the gaseous effluent. Other methods
for separating the catalyst composition from the gaseous effluent
include the use of plates, caps, elbows, and the like.
In one embodiment, the disengaging vessel includes a stripping
zone, typically in a lower portion of the disengaging vessel. In
the stripping zone the coked catalyst composition is contacted with
a gas, preferably one or a combination of steam, methane, carbon
dioxide, carbon monoxide, hydrogen, or an inert gas such as argon,
preferably steam, to recover adsorbed hydrocarbons from the coked
catalyst composition that is then introduced to the regeneration
system.
The coked catalyst composition is withdrawn from the disengaging
vessel and introduced to the regeneration system. The regeneration
system comprises a regenerator where the coked catalyst composition
is contacted with a regeneration medium, preferably a gas containing
oxygen, under conventional regeneration conditions of temperature,
pressure and residence time.
Non-limiting examples of suitable regeneration media include one
or more of oxygen, O.sub.3 SO.sub.3 N.sub.2 O, NO, NO.sub.2 N.sub.2
O.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
45.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).
The residence time of the catalyst composition in the regenerator
may be in the range of from about one minute to several hours, such
as from about one minute to 100 minutes, and the volume of oxygen
in the regeneration gas may be in the range of from about 0.01 mole
percent to about 5 mole percent based on the total volume of the
gas.
The burning of coke in the regeneration step is an exothermic reaction,
and in an embodiment, the temperature within the regeneration system
is controlled by various techniques in the art including feeding
a cooled gas to the regenerator vessel, operated either in a batch,
continuous, or semi-continuous mode, or a combination thereof. A
preferred technique involves withdrawing the regenerated catalyst
composition from the regeneration system and passing it through
a catalyst cooler to form a cooled regenerated catalyst composition.
The catalyst cooler, in an embodiment, is a heat exchanger that
is located either internal or external to the regeneration system.
Other methods for operating a regeneration system are in disclosed
U.S. Pat. No. 6290916 (controlling moisture), which is herein
fully incorporated by reference.
The regenerated catalyst composition withdrawn from the regeneration
system, preferably from 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).
By controlling the flow of the regenerated catalyst composition
or cooled regenerated catalyst composition from the regeneration
system to the reactor system, the optimum level of coke on the molecular
sieve catalyst composition entering the reactor is maintained. There
are many techniques for controlling the flow of a catalyst composition
described in Michael Louge, Experimental Techniques, Circulating
Fluidized Beds, Grace, Avidan and Knowlton, eds., Blackie, 1997
(336-337), which is herein incorporated by reference.
Coke levels on the catalyst composition are measured by withdrawing
the catalyst composition from the conversion process and determining
its carbon content. Typical levels of coke on the molecular sieve
catalyst composition, after regeneration, are in the range of from
0.01 weight percent to about 15 weight percent, such as from about
0.1 weight percent to about 10 weight percent, for example from
about 0.2 weight percent to about 5 weight percent, and conveniently
from about 0.3 weight percent to about 2 weight percent based on
the weight of the molecular sieve.
The gaseous effluent is withdrawn from the disengaging system and
is passed through a recovery system. There are many well known recovery
systems, techniques and sequences that are useful in separating
olefin(s) and purifying olefin(s) from the gaseous effluent. Recovery
systems generally comprise one or more or a combination of various
separation, fractionation and/or distillation towers, columns, splitters,
or trains, reaction systems such as ethylbenzene manufacture (U.S.
Pat. No. 5476978) and other derivative processes such as aldehydes,
ketones and ester manufacture (U.S. Pat. No. 5675041), and other
associated equipment, for example various condensers, heat exchangers,
refrigeration systems or chill trains, compressors, knock-out drums
or pots, pumps, and the like.
Non-limiting examples of these towers, columns, splitters or trains
used alone or in combination include one or more of a demethanizer,
preferably a high temperature demethanizer, a 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.
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.
Other recovery systems that include purification systems, for example
for the purification of olefin(s), are described in Kirk-Othmer
Encyclopedia of Chemical Technology, 4th Edition, Volume 9 John
Wiley & Sons, 1996 pages 249-271 and 894-899 which is herein
incorporated by reference. Purification systems are also described
in for example, U.S. Pat. No. 6271428 (purification of a diolefin
hydrocarbon stream), U.S. Pat. No. 6293999 (separating propylene
from propane), and U.S. patent application Ser. No. 09/689363 filed
Oct. 20 2000 (purge stream using hydrating catalyst), which are
herein incorporated by reference.
Generally accompanying most recovery systems is the production,
generation or accumulation of additional products, by-products and/or
contaminants along with the preferred prime products. The preferred
prime products, the light olefins, such as ethylene and propylene,
are typically purified for use in derivative manufacturing processes
such as polymerization processes. Therefore, in the most preferred
embodiment of the recovery system, the recovery system also includes
a purification system. For example, the light olefin(s) produced
particularly in a MTO process are passed through a purification
system that removes low levels of by-products or contaminants.
Non-limiting examples of contaminants and by-products include generally
polar compounds such as water, alcohols, carboxylic acids, ethers,
carbon oxides, sulfur compounds such as hydrogen sulfide, carbonyl
sulfides and mercaptans, ammonia and other nitrogen compounds, arsine,
phosphine and chlorides. Other contaminants or by-products include
hydrogen and hydrocarbons such as acetylene, methyl acetylene, propadiene,
butadiene and butyne.
Typically, in converting one or more oxygenates to olefin(s) having
2 or 3 carbon atoms, a minor amount hydrocarbons, particularly olefin(s),
having 4 or more carbon atoms is also produced. The amount of 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 efflu |