U.S. patent application number 10/348362 was filed with the patent office on 2003-07-24 for method for selectively producing propylene by catalytic cracking an olefinic hydrocarbon feedstock.
Invention is credited to Chen, Tan-Jen, Davis, S. Mark, Janssen, Marcel J. G., Martens, Luc R. M., Ruziska, Philip A..
Application Number | 20030139636 10/348362 |
Document ID | / |
Family ID | 22112014 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030139636 |
Kind Code |
A1 |
Chen, Tan-Jen ; et
al. |
July 24, 2003 |
Method for selectively producing propylene by catalytic cracking an
olefinic hydrocarbon feedstock
Abstract
The invention provides a method for converting an olefinic
hydrocarbon feedstock to propylene comprising: contacting a
hydrocarbon feedstock under catalytic cracking conditions with a
catalyst comprising a catalyst selected from the group consisting
of SAPO catalysts, MeAPO catalysts, MeASPO catalysts, ELAPO
catalysts, ELASPO catalysts, rare earth exchanged catalysts from
any of the preceding groups, and mixtures thereof, under cracking
conditions to selectively produce propylene. The invention further
provides a method for stabilizing a catalyst to steam from the
foregoing group by ion exchange with a rare earth metal. A catalyst
has enhanced stability as used herein when treated with a rare
earth metal or metals in a concentration effective to provide a
catalyst which exhibits a higher conversion of a hydrocarbon
feedstock to propylene than does an equal quantity of an untreated
sample of the same catalyst under the same conditions following
exposure of each catalyst to steam for a period of at least 10
hours.
Inventors: |
Chen, Tan-Jen; (Kingwood,
TX) ; Davis, S. Mark; (Baton Rouge, LA) ;
Martens, Luc R. M.; (Meise, BE) ; Janssen, Marcel J.
G.; (Leuven, BE) ; Ruziska, Philip A.;
(Kingwood, TX) |
Correspondence
Address: |
ExxonMobil Chemical Comapany
5200 Bayway Drive
P.O. Box 2149
Baytown
TX
77520
US
|
Family ID: |
22112014 |
Appl. No.: |
10/348362 |
Filed: |
January 21, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10348362 |
Jan 21, 2003 |
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10141248 |
May 8, 2002 |
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10141248 |
May 8, 2002 |
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09073148 |
May 5, 1998 |
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6429348 |
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Current U.S.
Class: |
585/653 ;
502/214; 585/648 |
Current CPC
Class: |
C07C 2529/85 20130101;
Y02P 20/52 20151101; B01J 29/85 20130101; C10G 2400/20 20130101;
C07C 4/06 20130101; C07C 2529/84 20130101 |
Class at
Publication: |
585/653 ;
502/214; 585/648 |
International
Class: |
B01J 027/182; C07C
004/06; C07C 004/02 |
Claims
We claim:
1. A method of converting an olefinic hydrocarbon feedstock to a
high propylene content product comprising: contacting a hydrocarbon
feedstock under catalytic cracking conditions with a catalyst
comprising a catalyst selected from the group consisting of SAPO
catalysts, MeAPO catalysts, MeASPO catalysts, ElAPO catalysts and
ElASPO catalysts, under cracking conditions to selectively produce
propylene.
2. The method of claim 1 wherein the selectivity produces a
propylene to butylene ratio of at least 2:1 or a propylene to
ethylene of at least 4:1.
3. The method of claim 1 wherein the olefinic hydrocarbon feedstock
consists essentially of hydrocarbons boiling within the range of
18.degree. to 220.degree. C. (65.degree. F. to 430.degree. F.).
4. The method of claim 1 wherein the olefinic hydrocarbon feedstock
consists essentially of hydrocarbons boiling in the range of
18.degree. to 148.degree. C. (65.degree. F. to 300.degree. F.).
5. The method of claim 1 wherein the olefinic hydrocarbon feedstock
comprises from about 10 wt % to about 70 wt % olefins.
6. The method of claim 1 wherein the olefinic hydrocarbon feedstock
comprises from 20 wt % to 70 wt % olefins.
7. The method of claim 1 wherein the olefinic hydrocarbon feedstock
comprises from about 5 wt % to about 35 wt % paraffins.
8. The method of claim 1 wherein the olefinic hydrocarbon feedstock
comprises from about 10 wt % to about 30 wt % paraffins.
9. The method of claim 1 wherein the olefinic hydrocarbon feedstock
comprises from about 10 wt % to about 25 wt % paraffins.
10. The method of claim 1 wherein the catalyst is contacted in the
range of 400.degree. C. to 700.degree..
11. The method of claim 1 wherein the catalyst is contacted at a
WHSV of 1 to 300 hr.sup.-1.
12. The method of claim 1 wherein the catalyst is contacted at a
pressure of 0.1 to 30 atm. absolute.
13. The method of claim 1 wherein the catalyst comprises a catalyst
selected from the group consisting of SAPO-11, SAPO-17, SAPO-31,
SAPO-34, SAPO-35, SAPO-41, SAPO-44, MeAPO-11, MeAPO-31, MeAPO-41,
MeAPSO-11, MeASPO-31, MeASPO-41, MeASPO-46, ElAPO-11, ElAPO-31,
ElAPO-41, ElAPSO-11, ElAPSO-31 and ElASPO-41.
14. The method of claim 1 wherein the catalyst is prepared by a
method which comprises ion exchanging the catalyst with a solution
comprising an alkaline earth metal ion or a rare earth metal
ion.
15. The method of claim 1 wherein the catalyst is exchanged against
a solution comprising a rare earth metal ion selected from the
group consisting of cerium, lanthanum, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, dysprosium,
holmium, erbium, thulium, ytterbium, lutetium and mixtures
thereof
16. The method of claim 9 wherein the rare earth metal ion
comprises lanthanum.
17. The method in claim 1 wherein the hydrocarbon feed is cracked
over the catalyst at reactor temperatures of from about
400-700.degree. C., pressures of from about 0.1 atmosphere to about
30 atmospheres absolute, and weight hourly space velocities of from
about 0.1 hr.sup.-1 to about 100 hr.sup.-1.
18. In a method for catalytic cracking of an olefinic hydrocarbon
feed to produce a light olefin containing product, the improvement
which comprises mixing a catalyst selected from the non zeolitic
catalyst group consisting of SAPO catalysts, MeAPO catalysts,
MeASPO catalysts, ElAPO catalysts and ElASPO catalysts with a
second cracking catalyst in a quantity sufficient to increase
propylene content in the light olefin product while decreasing
either ethylene or butylene when the product composition obtained
with the mixed catalyst is compared to the product composition
obtained with the second catalyst alone under the same reaction
conditions.
19. The method of claim 18 wherein the olefinic hydrocarbon
feedstock consists essentially of hydrocarbons boiling within the
range of 18.degree. to 220.degree. C. (65.degree. F. to 430.degree.
F.).
20. The method of claim 18 wherein the olefinic hydrocarbon
feedstock consists essentially of hydrocarbons boiling in the range
of 18.degree. to 148.degree. C. (65.degree. F. to 300.degree.
F.).
21. The method of claim 18 wherein the olefinic hydrocarbon
feedstock comprises from about 10 wt % to about 70 wt %
olefins.
22. The method of claim 18 wherein the olefinic hydrocarbon
feedstock comprises from 20 wt % to 70 wt % olefins.
23. The method of claim 18 wherein the olefinic hydrocarbon
feedstock comprises from about 5 wt % to about 35 wt %
paraffins.
24. The method of claim 18 wherein the olefinic hydrocarbon
feedstock comprises from about 10 wt % to about 30 wt %
paraffins.
25. The method of claim 18 wherein the olefinic hydrocarbon
feedstock comprises from about 10 wt % to about 25 wt %
paraffins.
26. The method of claim 18 wherein the selected catalyst comprises
a silicoaluminophosphate selected from the group consisting of
SAPO-11, SAPO-17, SAPO-31, SAPO-34, SAPO-35, SAPO-41, SAPO-44,
MeAPO-11, MeAPO-31, MeAPO-41, MeAPSO-11, MeAPSO-31, MeAPSO-41,
MeAPSO-46, ElAPO-11, ElAPO-31, ElAPO-41, ElAPSO-11, ElAPSO-31, and
ElAPSO-41.
27. The method of claim 18 wherein the mixed catalyst is contacted
in the range of 400.degree. C. to 700.degree. C.
28. The method of claim 18 wherein the catalyst is contacted at a
WHSV of 1 hr.sup.-1 to 300 hr.sup.-1.
29. The method of claim 18 wherein the catalyst is contacted at a
pressure of 0.1 to 30 atm.
30. The method of claim 18 wherein the selected catalyst is
prepared by a method which comprises ion exchanging the catalyst
with an aqueous solution comprising an alkaline earth metal ion or
a rare earth metal ion.
31. The method of claim 30 wherein the selected catalyst is
exchanged against a solution comprising a rare earth metal ion
selected from the group consisting of cerium, lanthanum,
praseodymium, neodymium, promethium, samarium, europium,
gadolinium, terbium, dysprosium, holmium, erbium, thulium,
ytterbium, lutetium and mixtures thereof.
32. The method of claim 30 wherein the rare earth metal ion
comprises lanthanum.
33. The method in claim 18 wherein the hydrocarbon feed is cracked
over the catalyst at reactor temperatures of from about
400-700.degree. C., pressures of from about 0.1 atmosphere to about
30 atmospheres absolute, and weight hourly space velocities of from
about 0.1 hr.sup.-1 about 100 hr.sup.-1.
34. A method for enhancing the stability of a
silicoaluminophosphate catalyst in propylene production which
comprises ion exchanging the selected catalyst with a solution
which comprises a rare earth metal.
35. The method of claim 34 wherein the ion exchange is with an
aqueous solution comprising a rare earth metal ion.
36. The method of claim 34 wherein the selected catalyst is
exchanged against a solution comprising a rare earth metal ion
selected from the group consisting of cerium, lanthanum,
praseodymium, neodymium, promethium, samarium, europium,
gadolinium, terbium, dysprosium, holmium, erbium, thulium,
ytterbium, lutetium and mixtures thereof.
37. The method of claim 34 wherein the rare earth metal ion
comprises lanthanum.
38. The method of claim 22 wherein the catalyst is selected from
the group consisting of SAPO catalysts, MeAPO catalysts, MeASPO
catalysts, ElAPO catalysts and ElASPO catalysts and mixtures
thereof.
39. A method for producing propylene in a cracking process while
minimizing production of butylene which comprises contacting an
olefinic hydrocarbon feed with a non-zeolitic
silicoaluminophosphate containing catalyst under cracking
conditions to produce at least 2 times as much propylene as
butylenes.
40. A method according to claim 39 wherein the process produces at
least 4 times as much propylene as ethylene.
41. A method according to claim 39 wherein the catalyst is selected
from the group consisting of SAPO catalysts, MeAPO catalysts,
MeASPO catalysts, ElAPO catalysts and ElASPO catalysts and mixtures
thereof.
42. A method according to claim 41 wherein the catalyst is a SAPO
selected from the group consisting of SAPO-11, SAPO-17, SAPO-31,
SAPO-34, SAPO-35, SAPO-41, SAPO-44.
43. A method according to claim 39 wherein at least 2.5 times as
much propylene as butylenes is produced.
44. A method according to claim 39 wherein at least 3 times as much
propylene as butylenes is produced.
45. A method for producing propylene in a cracking process while
minimizing production of ethylene which comprises contacting an
olefinic hydrocarbon feed with a non-zeolitic
silicoaluminophosphate containing catalyst under cracking
conditions to produce at least 2 times as much propylene as
ethylene.
46. A method according to claim 45 wherein the process produces at
least 4 times as much propylene as ethylene.
47. A method according to claim 45 wherein the catalyst is selected
from the group consisting of SAPO catalysts, MeAPO catalysts,
MeASPO catalysts, ElAPO catalysts and ElASPO catalysts and mixtures
thereof.
48. A method according to claim 45 wherein the catalyst is a SAPO
selected from the group consisting of SAPO-11, SAPO-17, SAPO-31,
SAPO-34, SAPO-35, SAPO-41, SAPO-44.
49. A method according to claim 45 herein at least 2 times as much
propylene as butylenes is produced.
50. A method according to claim 45 wherein at least 3 times as much
propylene as butylenes is produced.
Description
FIELD OF THE INVENTION
[0001] The invention relates to catalytic cracking of hydrocarbons.
Particularly the invention relates to a method providing improved
selectivity for cracking hydrocarbon feedstocks to propylene by
contacting the hydrocarbon under cracking conditions with a
catalyst selected from the non-zeolitic molecular sieves consisting
of silicoaluminophosphates ("SAPO"), metal aluminophosphates
("MeAPO"), metal aluminosilicophoshates ("MeASPO"), elemental
aluminophosphates ("ElAPO") and elemental aluminosilcophosphates
("ElASPO") where the metals include divalent Co, Fe, Mg, Mn, and Zn
and trivalent Fe and the elements include Li, Be, B, Ga, Ge, As,
and Ti.
BACKGROUND OF THE INVENTION
[0002] Thermal and catalytic conversion of hydrocarbons to olefins
is an important industrial process producing millions of pounds of
olefins each year. Because of the large volume of production, small
improvements in operating efficiency translate into significant
profits. Catalysts play an important role in more selective
conversion of hydrocarbons to olefins.
[0003] While important catalysts are found among the natural and
synthetic zeolites, it has also been recognized that non-zeolitic
molecular sieves such as silicoaluminophosphates (SAPO) including
those described in U.S. Pat. No. 4,440,871 also provide excellent
catalysts for cracking to selectively produce light hydrocarbons
and olefins. The SAPO molecular sieve has a network of AlO.sub.4,
SiO.sub.4, and PO.sub.4 tetrahedra linked by oxygen atoms. The
negative charge in the network is balanced by the inclusion of
exchangeable protons or cations such as alkali or alkaline earth
metal ions. The interstitial spaces or channels formed by the
crystalline network enables SAPOs to be used as molecular sieves in
separation processes and in catalysis. There are a large number of
known SAPO structures. The synthesis and catalytic activity of the
SAPO catalysts are disclosed in U.S. Pat. No. 4,440,871.
[0004] In other crystalline microporous solids belonging to the
class of aluminophosphates the framework is normally neutral (Al
(III):P (V) atomic ratio=1). This framework can be made negative
and thereby gives these materials advantageous properties such as
adsorption, cation exchange or catalytic activity by replacing P(V)
or the pair Al (III), P(V) with a tetravalent element such as
silicon, converting to the closely related SAPO structure discussed
above, or by replacing Al (III) with a metal, especially a divalent
metal such as zinc or cobalt, the materials obtained being denoted
by the acronym MeAPO where Me is the metal, or else by combining
these two types of substitution, the materials obtained being
denoted by the acronym MeAPSO. A group of such materials is
described in U.S. Pat. No. 5,675,050.
[0005] In the International Application WO 91/18851 the exchange of
cations to provide Lewis acid sites in zeolite and SAPO catalytic
structures in isomerization catalysts is disclosed. SAPO-11 is
disclosed as being particularly effective in this system. The
application focuses on skeletal isomerization of n-olefins. There
is no teaching of enhanced selectivity or stability under catalytic
cracking conditions. Nor is there any discussion of increased
stability in rare earth exchanged SAPO.
[0006] SAPO catalysts mixed with zeolites (including rare earth
exchanged zeolites) are known to be useful in cracking of gasoils
(U.S. Pat. No. 5,318,696). U.S. Pat. Nos. 5,456,821 and 5,366,948
describe cracking catalysts with enhanced propylene selectivity
which are mixtures of phosphorus treated zeolites with a second
catalyst which may be a SAPO or a rare earth exchanged zeolite.
Rare earth treated zeolite catalysts useful in catalytic cracking
are disclosed in U.S. Pat. Nos. 5,380,690, 5,358,918, 5,326,465,
5232,675 and 4,980,053. The use of SAPO catalysts for cracking
crude oil feed or "carbon-hydrogen fragmentation compounds"
(materials with 5 or less carbons) is disclosed in U.S. Pat. Nos.
4,666,875 and 4,842,714 (SAPO-37 preferred for cracking gas oils).
Although these patents disclose the use of rare earth exchanged
SAPO catalysts, they state: "At present the presence of rare earth
cations with the SAPO molecular sieves has not been observed to be
beneficial to the activity of the SAPO component. The exact nature
of the relationship of multi-valent cations and SAPO catalysts is
not clearly understood at present, although in some instances their
presence may be beneficial." (U.S. Pat. No. 4,666,875 at Col. 4
Lines 39-44, U.S. Pat. No. 4,842,714 Col. 11, Lines 29-34.)
[0007] The art has not previously recognized the highly selective
conversion of hydrocarbon, especially naphtha feedstocks to
propylene promoted by SAPO and related catalysts nor the improved
stability obtained by rare earth exchanging such catalysts.
SUMMARY OF THE INVENTION
[0008] The invention provides a method for converting an olefinic
hydrocarbon feedstock to propylene comprising: contacting a
hydrocarbon feedstock under catalytic cracking conditions with a
catalyst comprising a nonzeolitic catalyst selected from the group
consisting of SAPO catalysts, MeAPO catalysts, MeASPO catalysts,
ElAPO catalysts, ElASPO catalysts, rare earth exchanged catalysts
from any of the preceding groups, and mixtures thereof, under
cracking conditions to selectively produce propylene. Preferably
the method is carried out to produce propylene in a propylene to
ethylene ratio of at least 4:1 and a propylene to butylene ration
of at least 2:1. The invention further provides an method for
stabilizing a catalyst from the foregoing group by ion exchange
with a rare earth metal. A catalyst has enhanced stability as used
herein when treated with a rare earth metal or metals in a
concentration effective to provide a catalyst which exhibits a
higher conversion of a hydrocarbon feedstock to propylene than does
an equal quantity of an untreated sample of the same catalyst under
the same conditions following exposure of each catalyst to steam
for a period of at least 10 hours. The invention also provides an
improvement in methods for catalytic cracking of an olefinic
hydrocarbon feedstock to produce a light olefin containing product
wherein it is desired to improve the propylene content of the
product mixture. The improvement comprises mixing a catalyst
selected from the non zeolitic catalyst group consisting of SAPO
catalysts, MeAPO catalysts, MeASPO catalysts, ElAPO catalysts and
ElASPO catalysts with a second cracking catalyst in a quantity
sufficient to increase propylene content in the light olefin
product while decreasing either ethylene or butylene when the
product composition obtained with the mixed catalyst is compared to
the product composition obtained with the second catalyst alone
under the same reaction conditions.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The silicoaluminophosphate (SAPO) catalysts useful in the
present invention have a three-dimensional microporous crystal
framework structure of PO.sub.2.sup.+, AlO.sub.2.sup.- and
SiO.sub.2 tetrahedral units, and whose essential empirical chemical
composition on an anhydrous basis is: m R:(Si[x]Al[y]P[z])O[2]
wherein "R" represents at least one organic templating agent
present in the intracrystalline pore system: "m" represents the
moles of "R" present per mole of (Si[x]Al[y]P[z])O2 and has a value
of from zero to 0.3, the maximum value in each case depending upon
the molecular dimensions of the templating agent and the available
void volume of the pore system of the particular
silicoaluminophosphate species involved, "x", "y" and "z" represent
the mole fractions of silicon, aluminum and phosphorus,
respectively, present as tetrahedral oxides, representing the
following values for "x", "y" and "z".
1 Mole Fraction x y z 0.01 0.47 0.52 0.94 0.01 0.05 0.98 0.01 0.01
0.39 0.60 0.01 0.01 0.60 0.39
[0010] When synthesized in accordance with the process disclosed in
U.S. Pat. No. 4,440,871, the minimum value of "m" in the formula
above is 0.02. In a preferred sub-class of the SAPOs useful in this
invention, the values of "x", "y" and "z" in the formula above are
set out in the following table:
2 Mole Fraction x y z 0.02 0.49 0.49 0.25 0.37 0.38 0.25 0.48 0.27
0.13 0.60 0.27 0.02 0.60 0.38
[0011] Preferred SAPO catalysts include SAPO-11, SAPO-17, SAPO-31,
SAPO-34, SAPO-35, SAPO-41, and SAPO-44.
[0012] The catalysts suitable for use in the present invention
include, in addition to the SAPO catalysts, the metal integrated
aluminophosphates (MeAPO and ELAPO) and metal integrated
silicoaluminophosphates (MeAPSO and ElAPSO). The MeAPO, MeAPSO,
ElAPO, and ElAPSO families have additional elements included in
their framework. For example, Me represents the elements Co, Fe,
Mg, Mn, or Zn, and El represents the elements Li, Be, Ga, Ge, As,
or Ti. Preferred catalysts include MeAPO-11, MeAPO-31, MeAPO-41,
MeAPSO-11, MeAPSO-31, and MeAPSO-41, MeAPSO-46, ElAPO-11, ElAPO-31,
ElAPO-41, ElAPSO-11, ElAPSO-31, and ElAPSO-41.
[0013] The non-zeolitic SAPO, MeAPO, MeAPSO, ElAPO and ElAPSO
classes of microporus materials are further described in the "Atlas
of Zeolite Structure Types" by W. M. Meier, D. H. Olson and C.
Baerlocher (4th ed., Butterworths/Intl. Zeolite Assoc. (1996) and
"Introduction to Zeolite Science and Practice", H. Van Bekkum, E.
M. Flanigen and J. C. Jansen Eds., Elsevier, New York,
(1991).).
[0014] The selected catalysts may also include cations selected
from the group consisting of cations of Group IIA, Group IIIA,
Groups IIIB to VIIBB and rare earth cations selected from the group
consisting of cerium, lanthanum, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, dysprosium,
holmium, erbium, thulium, ytterbium, lutetium and mixtures
thereof.
[0015] Preferred olefinic hydrocarbon feedstocks are nathphas in
the boiling range of 18.degree. to 220.degree. C. (65.degree. F. to
430.degree. F.). The naphthas may be thermally cracked naphthas or
catalytically cracked naphthas. The feed should contain from at
least 10 wt % to about 70 wt % olefins, preferably 20 wt % to 70 wt
%, and may also include naphthenes and aromatics. The naphthas may
contain paraffins in the range of 5 wt % to 35 wt %, preferably 10
wt % to 30 wt %, most preferably 10 wt % to 25 wt %. For example,
the naphtha may be derived from fluid catalytic cracking ("FCC") of
gas oils and resids, or from delayed or fluid coking of resids. The
preferred naphtha streams are derived from FCC gas oils or resids
which are typically rich in olefins and diolefins and relatively
lean in paraffins.
[0016] Catalytic cracking conditions means a catalyst contacting
temperature in the range of about 400.degree. C. to 750.degree. C.,
more preferably in the range of 450.degree. C. to 700.degree. C.,
most preferably in the range of 500.degree. C. to 650.degree. C.
The catalyst contacting process is preferably carried out at a
weight hourly space velocity (WHSV) in the range of about 0.1
Hr.sup.-1 to about 300 Hr.sup.-1, more preferably in the range of
about 1.0 Hr.sup.-1 to about 250 Hr.sup.-1, and most preferably in
the range of about 10 Hr.sup.-1 to about 100 Hr.sup.-1. Pressure in
the contact zone may be from 0.1 to 30 atm. absolute, preferably 1
to 3 atm. absolute, most preferably about 1 atm. absolute. The
catalyst may be contacted in any reaction zone such as a fixed bed,
a moving bed, a slurry, a transfer line, a riser reactor or a
fluidized bed.
[0017] Test Conditions
[0018] A series of runs in a small bench reactor was conducted on
hexene as a model compound. Comparison runs with a ZSM-5 zeolite
catalyst commercially available from Intercat. Inc., of Sea Girt,
N.J. were conducted over a fixed bed of catalyst. The effluent
stream was analyzed by on-line gas chromatography. A column having
a length of 60 m packed with fused silica was used for the
analysis. The gas chromatograph was a dual flame ionization
detector equipped Hewlett-Packard Model 5880. All tabulated data is
in weight percent unless otherwise indicated.
EXAMPLE 1
[0019] Constant Reactor Conditions
[0020] The hexene model compound was cracked over ZSM-5, SAPO-11
and SAPO-34 catalysts at 650.degree. C., 12 hr.sup.-1 WHSV, 1.6
nitrogen dilution, 12 psig.
3 TABLE 1 Catalyst ZSM-5 SAPO-34 SAPO-11 Conversion 95.4 63.6 88.8
Key Results Ethylene 24.5 11.0 8.4 Propylene 35.8 30.3 54.8
Butylenes 12.8 11.2 11.8 Aromatics 12.8 2.7 8.5 Light Saturates 9.5
8.5 5.4 Selectivity (% of Conversion) Ethylene 25.7 17.3 9.5
Propylene 37.5 47.6 61.7 Butylene 13.4 17.6 13.3 Propylene/ethylene
1.5 2.8 6.5 Propylene/butylene 2.8 2.7 4.7
[0021] As can be seen from Table 1, the SAPO-11 catalyst was
slightly less active than the comparison ZSM-5 in terms of
conversion. The data show that SAPO-11 was more selective for
propylene over ethylene and butylene as ZSM-5, and SAPO-34 also
shows significantly increased production of propylene over both
ethylene and butylene.
EXAMPLE 2
[0022] Constant Conversion
[0023] In this example the conditions are the same as in Example 1
except the weight hourly space velocity was adjusted to make
conversion equal for the control ZSM-5 and SAPO-11.
4 TABLE 2 Catalyst ZSM-5 SAPO-11 WHSV, Hr.sup.-1 40 12 Conversion
89.0 88.8 Key Results Ethylene 13.1 8.4 Propylene 47.6 54.8
Butylene 14.9 11.8 Aromatics 7.4 8.5 Light Saturates 6.1 5.4
Selectivity Ethylene 14.7 9.5 Propylene 53.3 61.7 Butylene 16.7
13.3 Propylene/Ethylene Ratio 3.6 6.5 Propylene/Butylene Ratio 3.2
4.7
[0024] As can be seen from Table 2, SAPO-11 produced significantly
more propylene and less ethylene and butylenes than ZSM-5
catalyst.
EXAMPLE 3
[0025] Effect of Temperature and Throughput
[0026] In this example SAPO-11 extrudate catalyst was tested with
the hexene model compound in the apparatus of Example 1 under the
conditions indicated in Table 3.
5 TABLE 3 Temperature, .degree. C. 650 600 600 WHSV, Hr.sup.-1 12
12 8 Conversion 88.8 75.9 87.9 Key Results Ethylene 8.4 3.6 3.9
Propylene/ 54.8 60.6 69.7 Butylene 11.8 7.1 7.4 Aromatics 8.5 2.7
5.0 Light Saturates 5.4 1.8 2.0 Selectivity, % Ethylene 9.5 4.7 4.4
Propylene 61.7 79.8 79.3 Butylene 13.3 9.4 8.4 Propylene/Ethylene
Ratio 6.5 16.8 17.9 Propylene/Butylene Ratio 4.7 8.5 9.4
[0027] As the data above indicate, selectivity is improved by
reducing the temperature and by maintaining high conversion by
decreasing throughput thus increasing the average time the
feedstock is in contact with the catalyst. The propylene/ethylene
ratio approaching 18:1 is exceptional, as is the propylene/butylene
ratio at 9.4:1. With ZSM-5 catalysts lowering the temperature
typically results in increasing butylene selectivity, while the
SAPO catalysts display the opposite tread which is unexpected. It
has been found that the selectivity of the catalysts can be
maintained over a wide range of conversion levels so long as
cracking conditions are maintained.
EXAMPLE 4
[0028] Selectivity in Cracking of a Typical Refinery Feedstock
[0029] A typical refinery feedstock, Baton Rouge Light Cat.
Naphtha, (LCN) was contacted with fresh and steamed SAPO-11 at
600.degree. C., 6 Hr.sup.-1 WHSV, 1.6 N.sub.2 dilution, and 12
psig. The results are listed in Table 4.
6TABLE 4 Catalyst ZSM-5 SAPO-11 SAPO-11 Presteaming Conditions
816.degree. C./40 Hr. Fresh 593.degree. C./16 Hr. Conversion 40.7
33.9 33.2 Key Results Ethylene 5.1 3.2 2.6 Propylene 24.7 24.9 25.3
Butylene 9.5 4.2 3.8 Aromatics 4.5 5.5 4.4 Light Saturates 1.4 1.6
1.5 Selectivity, % Ethylene 12.5 9.4 7.8 Propylene 60.7 73.5 76.2
Butylenes 23.3 12.4 11.4 Propylene/Ethylene Ratio 4.8 7.8 9.7
Propylene/Butylene Ratio 2.6 5.9 6.6
[0030] The selectivity observed with the model compound is
maintained with the refinery feedstock. Selectivity appears to
improve when the catalyst is pre-steamed.
EXAMPLE 5
[0031] Performance of Calcium exchanged SAPO-11
[0032] To 10 g SAPO-11 was added 1000 ml of a 10 wt %
Ca(NO.sub.3).sub.2 solution. This solution was stirred for 16 hrs
at 65.degree. C. After washing, the sample was dried overnight at
90.degree. C., followed by air calcination for 16 hrs at
525.degree. C. The procedure was repeated twice to obtain the
finished catalyst. The calcium exchanged SAPO-11 was contacted with
the hexene model compound at 600.degree. C., and 2 Hr.sup.-1. The
nitrogen diluent to hydrocarbon ratio was 5:1. The results are
shown in Table 5.
7 TABLE 5 Catalyst ZSM-5 SAPO-11 Conversion 99.3 89.8 Key Results
Ethylene 20.4 4.3 Propylene 22.6 57.5 Butylenes 8.3 11.8 Aromatics
25.0 1.4 Selectivity, % Ethylene 20.5 4.8 Propylene 22.8 64.0
Butylenes 8.4 13.1 Propylene/Ethylene Ratio 1.1 13.4
Propylene/Butylene Ratio 2.7 2.9
[0033] As demonstrated by the data above Ca SAPO-11 was found to be
very selective for propylene with a propylene selectivity of 64%
and low production of both ethylene and butylenes. An additional
benefit is the low aromatics production of only 1.4%
EXAMPLE 6
[0034] Improved Stability with Rare Earth Treated Nonzeolitic
Catalyst
[0035] SAPO-11 treated with a rare earth (lanthanum) resists loss
of activity when subjected to prolonged exposure to steam. Most
zeolite and other molecular sieve catalysts display a
characteristic loss of activity when exposed to steam over a
prolonged period. As the data below demonstrate rare earth
treatment of catalyst (SAPO-11) produces a catalyst with 60-70%
improvement in catalyst activity relative to non-treated SAPO-11
while retaining the outstanding selectivity for propylene over both
ethylene and butylene observed in the examples above. A sample of
SAPO-11 was ion-exchanged with a lanthanum solution by suspending
10 grams of SAPO-11 in 100 grams of water and 5 grams of
LaCl.sub.3.6 H.sub.2O were added. The mixture was refluxed at
100.degree. C. for 4 hrs, then dried and calcined.
[0036] The exchanged catalyst was contacted with Baton Rouge Light
Cat Naphtha, at 500.degree. C., 1/1 steam to hydrocarbon weight
ratio, at 5 Hr.sup.-1, 12 psig in the apparatus of Example 1. The
steamed catalysts were treated at 760.degree. C. with 100% steam
for 16 hours prior to the cracking test. The results are shown in
Table 6 below.
8TABLE 6 Catalyst Fresh Steamed Steamed SAPO-11 SAPO-11 LaSAPO-11
Conversion 27.5 12.0 20.2 Key Results Ethylene 1.5 0.4 0.9
Propylene 23.1 10.0 17.0 Butylene 2.7 1.5 2.1 Aromatics 2.9 2.1 2.7
Light Saturates Selectivity, % Ethylene 5.5 3.3 4.4 Propylene 84.0
83.1 84.0 Butylene 9.8 12.5 10.4 Propylene/Ethylene Ratio 15.2 25.2
19.1 Propylene/Butylenes Ratio 8.5 6.6 8.1
[0037] The preceding data show a positive result of rare earth
treatment of a SAPO catalyst. The improved resistance to loss of
activity on exposure to steam allows prolonged use of the catalyst.
The foregoing results are provided to illustrate the operation of
the invention in some of its embodiments. The examples are provided
by way of illustration and not as limitations on the scope or
practice of the invention, which is defined and limited by the
following claims.
* * * * *