Molecular sieve abstract
A SAPO-11 silicoaluminopihosphate molecular sieve, its preparation
method, and a catalyst containing the same are disclosed. The X-ray
diffraction data of the molecular sieve before removing the template
by calcination are as listed in Table 1. The molar composition of
this molecular sieve after removing the template by calcination
expressed in anhydrous oxides is Al.sub.2 O.sub.3 : yP.sub.2 O.sub.5
: zSiO.sub.2 in which y has a value of 0.60-1.20 and z has a value
of 0.05-1.3 characterized in that after removing the template by
calcination, its X-ray diffraction data are as listed in Table 3
and that the crystal structures of the molecular sieve before and
after removing the template by calcination are substantially the
same. The catalyst is composed of 10-85% by weight of said SAPO-11
molecular sieve, 0.05-1.5% by weight of Pd or Pt, and the balance
is alumina. In comparison with similar catalysts in the prior art,
when the catalyst of this invention is applied in the reaction of
hydrocarbon hydroisomerization, both selectivity and product yield
for isomerization are remarkably increased.
Molecular sieve claims
What is claimed is:
1. A SAPO-11 silicoaluminophosphate molecular sieve, the molar
composition of which after removing the template by calcination
can be expressed in anhydrous oxides as Al.sub.2 O.sub.3 : yP.sub.2
O.sub.5 : zSiO.sub.2 in which y has a value of 0.60-1.20 and z
has a value of 0.05-1.3; characterized in that after removing the
template by calcination, said molecular sieve has the main X-ray
diffraction data as listed in Table 3.
2. The molecular sieve according to claim 1 wherein y has a value
of 0.75-1.05 and z has a value of 0.1-1.1.
3. The molecular sieve according to claim 1 the molar composition
of which before removing the template is xR: Al.sub.2 O.sub.3 :
yP.sub.2 O.sub.5 : zSiO.sub.2 when expressed in anhydrous oxides,
in which R is an organic template presented in the pore of the molecular
sieve, x has a value of 0.01-0.35 and the values of y and z are
as defined in claim 1.
4. The molecular sieve according to claim 3 wherein said organic
template is di-n-propylamine-or di-isopropylamine or the mixture
thereof.
5. The molecular sieve according to claim 3 wherein x has a value
of 0.03-0.25.
6. A method for synthesizing the molecular sieve according to claim
1 comprising mixing an aluminum source, a silicon source, a phosphorus
source, and an organic template, to make a gelatinous reaction mixture
with a molar ratio of aR: Al.sub.2 O.sub.3 : bP.sub.2 O.sub.5 :
cSiO.sub.2 : dH.sub.2 O, crystallizing the mixture by steam treating,
and filtering, washing, drying, and calcining the crystallized product,
characterized in that the gelation temperature is in a range of
25-60.degree. C., and said crystallization by steam treating is
carried out at the temperature of 140-190.degree. C. and under the
autogenous pressure for 4-60 hours, in which a has a value of 0.2-2.0
b has a value of 0.6-1.2 c has a value of 0.1-1.5 and d has a
value of 15-50.
7. The method according to claim 6 wherein said aluminum source
is aluminum hydroxide, hydrated alumina, aluminum isopropoxide,
or aluminum phosphate, said silicon source is solid silica gel or
silica sol, said phosphorus source, is phosphoric acid or aluminum
phosphate, and said organic template is di-n-propylamine, di-isopropylamine,
or the mixture thereof.
8. The method according to claim 7 wherein said aluminum source
is hydrated alumina or aluminum isopropoxide, and said phosphorus
source is phosphoric acid.
9. The method according to claim 6 wherein said calcination condition
is at 500-650.degree. C. for 2-10 hours.
10. The method according to claim 6 wherein said gelation temperature
is in the range of 28-42.degree. C.
11. The method according to claim 10 wherein said gelation temperature
is in the range of 30-40.degree. C.
12. The method according to claim 6 wherein said crystallization
temperature is in the range of 150-180.degree. C.
13. The method according to claim 6 wherein said crystallization
time is 10-40 hours.
14. The method according to claim 6 wherein a has a value of 0.3-1.5.
15. The method according to claim 14 wherein a has a value of
0.5-1.0.
16. The method according to claim 6 wherein b has a value of 0.8-1.1.
17. The method according to claim 6 wherein c has a value of 0.3-1.2.
18. The method according to claim 6 wherein d has a value of 20-40.
19. The method according to claim 18 wherein d has a value of
25-35.
20. A catalyst for hydrocarbon hydroisomerization which is composed
of 10-85 wt. % of the SAPO-11 molecular sieve in claim 1 0.05-1.5
wt. % of Pd or Pt, and alumina in balance.
21. The catalyst according to claim 20 which is composed of 20-80
wt. % of said SAPO-11 molecular sieve, 0.1-1.2 wt. % of Pd or Pt,
and alumina in balance.
22. The catalyst according to claim 21 wherein said SAPO-11 molecular
sieve has a molar composition of Al.sub.2 O.sub.3 : (0.75-1.05)
P2O.sub.5 : (0.1-1.1) SiO.sub.2.
23. The catalyst according to claim 20 wherein said alumina is
obtained by calcining its precursor at 400-700.degree. C. for 1-5
hours, and said precursor of alumina is at least one compounds selected
from the group consisting of aluminum hydroxide, pseudo-boehmite,
alumina trihydrate, and bayerite.
24. The catalyst according to claim 23 wherein said precursor
of alumina is pseudo-boehmite.
25. The catalyst according to claim 20 wherein said hydrocarbon
is lubricant oil with a boiling range of 350-580.degree. C.
26. The catalyst according to claim 20 wherein said hydrocarbon
is diesel oil with a boiling range of 160-400.degree. C.
27. A hydroisomerization process for depressing the freezing point
of diesel oil or lubricant oil comprising contacting the oil with
the catalyst according to claim 20.
Molecular sieve description
FIELD OF THE INVENTION
This invention relates to a silicoaluminophosphate molecular sieve
(SAPO-11) with AEL-type structure, its synthetic method, and a catalyst
containing the same, especially a catalyst for hydrocarbon hydroisomerization.
DESCRIPTION OF THE PRIOR ART
Aluminophosphate molecular sieves are molecular sieves of a new
generation developed by UCC of the United States of America in early
1980's (U.S. Pat. No. 4310440) following the aluminosilicate molecular
sieves. The typical character of this class of molecular sieve is
that their framework is constructed by alternative connection of
phosphorus-oxygen tetrahedrons and aluminum-oxygen tetrahedrons,
and since the framework of the molecular sieves appears electrically
neutralized, they have no capability for carrying out cation exchange
and catalytic reaction.
The aluminophosphate (AlPO.sub.4 - 11) molecular sieve with AEL-type
structure is a member of the aluminophosphate molecular sieve family,
which belongs to the orthorhombic crystal system with a space group
of Ima2. Its crystal unit cell parameters are a=18.7 .ANG., b=13.4
.ANG., and c=8.4 .ANG., and the one dimensional pore size of its
10-member ring is 3.9.times.6.3 .ANG.. Its typical X-ray diffraction
data are listed in Table 1. After removing amine by calcination,
it still belongs to the orthorhombic system, but its symmetry is
changed and the space group turns to Pna2.sub.1 with the crystal
unit cell parameters of a=18.1 .ANG.A, b=13.8 .ANG., and c=8.1 .ANG..
Its X-ray diffraction pattern is apparently different from that
before calcination, and the data of a typical X-ray diffraction
pattern is listed in Table 2.
TABLE 1 2 .theta. d 100 .times. I/I.sub.0 8.05-8.15 10.97-10.84
w-m 9.40-9.50 9.40-9.30 m 13.10-13.25 6.75-6.68 m 15.65-15.85 5.66-5.59
m 20.35-20.55 4.36-4.32 m 21.00-21.20 4.23-4.19 vs 22.10-22.25 4.02-3.99
m 22.50-22.90 3.95-3.88 m (doublet) 23.10-23.35 3.85-3.81 m-s *w-m:
<20; m: 20-70; s: 70-90; vs: 90-100
TABLE 2 2 .theta. d 100 .times. I/I.sub.0 8.00-8.15 11.04-10.84
w-m 9.70-9.85 9.11-8.97 m 12.70-12.90 6.96-6.86 w-m 15.95-16.10
5.55-5.50 m 21.80-21.95 4.07-4.05 vs 22.05-22.15 4.03-4.01 m 22.35-22.50
3.97-3.95 m 23.25-23.55 3.82-3.77 m (doublet) *w-m: <20; m: 20-70;
s: 70-90; vs: 90-100
Silicoaluminophosphate molecular sieves, i.e. SAPO molecular sieve
series are formed when silicon is incorporated into the framework
of aluminophosphate molecular sieves (UCC of USA, U.S. Pat. No.
4440871). Their framework is constructed with phosphorus-oxygen
tetrahedrons, aluminum-oxygen tetrahedrons, and silicon-oxygen tetrahedrons,
and since their framework carries negative charge, they have non-framework
cations in balance and the capability of cation exchange. If the
non-framework cations are H.sup.+, they have acidic catalytic capability
since they have acidic centers.
The aluminophosphate molecular sieve with AEL structure containing
silicon (SAPO-11) has the same structure and XRD pattern as that
containing no silicon (AlPO.sub.4 -11), but after removing amine
by calcination, the structure of a molecular sieve has different
states. According to the results reported in U.S. Pat. No. 4440871
the typical data of the X-ray diffraction pattern of a synthesized
silicoaluminophosphate molecular sieve with AEL structure are the
same as listed in Table 1. After removing amine by calcination,
the data of the X-ray diffraction patterns are different depending
on the raw materials adopted. When the molecular sieve is synthesized
using phosphoric acid as a phosphorus source, aluminum isopropoxide
as an aluminum source, fuming silica gel as a silicon source, and
di-n-propylamine as a template, its data of X-ray diffraction pattern
after removing amine by calcination is partly changed with the appearance
of the diffraction peaks at 2.theta.=12.8 16.1 and 21.9.degree.,
etc, and the newly appearing peaks are substantially the same as
the data of the X-ray diffraction pattern of the aluminophosphate
having AEL structure and containing no silicon (AlPO.sub.4 -11)
after removing amine by calcination, showing that the crystal structure
of the molecular sieve synthesized by this method is partly changed
after removing amine by calcination. When the molecular sieve is
synthesized by using phosphoric acid, aluminum isopropoxide, silica
sol and di-n-propylamine as the raw materials, the data of the X-ray
diffraction pattern are remarkably changed with the appearance of
the diffraction peaks at 2.theta.=9.85 12.8 16.1 and 21.95.degree.,
and the thorough disappearance of the peaks at 2.theta.=9.4 13.1
15.65 and 21.1.degree. at the same time. These data are the same
as the data of the X-ray diffraction pattern of the aluminophosphate
molecular sieve containing no silicon (AlPO.sub.4 -11) after removing
amine by calcination. These results suggest that the structure of
the molecular sieve with AEL structure after calcination is different
depending on its composition and synthetic method.
U.S. Pat. Nos. 4943424 and 5208005 also disclose a molecular
sieve with AEL structure (SM-3) and its synthetic method. The data
of the X-ray diffraction pattern of said molecular sieve are substantially
the same as those of the molecular sieve disclosed in U.S. Pat.
No. 4440871. After removing amine by calcination, however, its
X-ray diffraction data are completely the same as those of the molecular
sieve with AEL structure containing no silicon after removing amine
by calcination, indicating that the structure of the molecular sieve
is also changed after removing amine by calcination. The other feature
of the molecular sieve emphasized by the two patents is the enriched
silicon on the surface of the molecular sieves derived by their
synthetic method.
Regarding the method for synthesizing the aluminophosphate and
silicoaluminophosphate molecular sieves with AEL structure, the
synthetic method described in U.S. Pat. No. 4310440 comprises:
taking phosphoric acid as a phosphorus source, hydrated alumina
(pseudo-boehmite) as an aluminum source, di-n-propylamine or di-isopropylamine,
ethylbutylamine, di-n-butylamine, di-n-pentylamine, as an organic
template, adding hydrated alumina into the aqueous solution of phosphoric
acid in a ratio of 1.0R: P.sub.2 O.sub.5 : Al.sub.2 O.sub.3 : 40H.sub.2
O, stirring to uniformity, adding the organic template after stirring
to uniformity, sealing the mixture into a stainless steel autoclave
lined with Teflon after stirring to uniformity, crystallizing at
200.degree. C. for 24-48 hours, and then filtering, washing, and
drying, to yield the molecular sieve product.
In the method provided in U.S. Pat. No. 4440871 for synthesizing
a silicoaluminophosphate molecular sieve with AEL structure, the
phosphorus source used is phosphoric acid, the aluminum source is
aluminum isopropoxide or hydrated alumina, the silicon source is
fuming silica gel or silica sol, and the organic template is di-n-propylamine
or di-isopropylamine. When aluminum isopropoxide is used as the
aluminum source, phosphoric acid was first added into the mixture
of aluminum isopropoxide and water, and after stirring to uniformity,
fuming silica gel is added. Then di-n-propylamine is added after
stirring and the stirring is continued until the mixture becomes
uniform. The mixture is sealed into a stainless steel autoclave
lined with Teflon, and crystallized at 150-200C. to obtain the molecular
sieves. When hydrated alumina (pseudo-boehmite) is used as the aluminum
source, the hydrated alumina was added into the aqueous solution
of phosphoric acid, and after stirring to uniformity, the mixture
of fuming silica gel and tetrabutylammonium hydroxide is added.
The mixture is stirred to uniformity, and the template di-n-propylamine
is added. Then crystallization is carried out after stirring to
uniformity to obtain the molecular sieve product. When aluminum
isopropoxide is used as the aluminum source, and silica sol is used
as the silicon source, the structure of the obtained molecular sieve
is thoroughly changed after removing amine by calcination. It is
worthy to note that, in the method provided in the aforesaid patents,
the influence of the gelation temperature has not been mentioned.
In the method provided by U.S. Pat. Nos. 4943424 and 5208005
for synthesizing a silicoaluminophosphate molecular sieve with AEL
structure, phosphoric acid, aluminum isopropoxide, fuming silica
gel and di-n-propylamine are used as the raw materials. Under the
ice bath condition, aluminum isopropoxide is added into the aqueous
solution of phosphoric acid, and fuming silica gel or a mixture
of fuming silica gel and water is added after mixing to uniformity.
Then di-n-propylamine is added, and after mixing or grinding, the
mixture was charged in a stainless steel vessel for crystallization,
and the molecular sieve product is obtained. This method emphasis
that the pH value after gelation should be adjusted to 6.0-8.0
and the optimum crystallization temperature is in the range of 170-240.degree.
C. The crystal structure of the product obtained is changed after
removing amine by calcination.
The technology of the shape selective isomerization of hydrocarbon
oil is well known. Generally, this technology is applied to treat
wax oil for reducing the content of normal paraffins. In order to
improve the performance of the oil products, normal paraffins, especially
long chain normal paraffins presented in the oil products should
be removed as much as possible. For example, the octane number of
the gasoline fraction can be boosted by removing the straight chain
paraffins through shape selective cracking or converting them into
branched paraffins by isomerization. For diesel oil or lubricant
oil, their freezing point or pouring point can be lowered by removing
the straight chain paraffins to improve their low temperature performance.
Another key problem is the yield of the target product in the above
reaction process. Since the reactant can be converted to lower hydrocarbons
with smaller molecules by cracking, the yield of the target product
may be lowered. Therefore, the isomerization reaction should be
enhanced as much as possible, and the cracking reaction should be
reduced as much as possible at the same time.
In view of the thermodynamic point, cracking reaction needs relatively
strong acidic centers in the catalyst and relatively high reaction
temperatures, and relatively weak acidic centers in the catalyst
and relatively low reaction temperature are beneficial to the isomerization
reaction. However, in order to increase the reaction activity and
overcome the shortcomings of low reaction efficiency caused by low
activity of the catalyst with weak acid centers and low reaction
temperature, it is needed to load active metal components with hydrogenation
and dehydrogenation functions for preparing bifunctional catalysts.
Isomerization catalysts with silicoaluminophosphate molecular sieves
as an acidic active component are described in U.S. Pat. Nos. 4710485
and 5087347.
U.S. Pat. No. 4710485 discloses a technology using a silicoaluminophosphate
molecular sieve as an isomerization catalyst. The silicoaluminophosphate
molecular sieves are selected from mesopore molecular sieves such
as SAPO-11or SAPO-41. SAPO-11 and SAPO-41 molecular sieves are synthesized
according the method disclosed in U.S. Pat. No. 4440871. Their
properties are also the same as those of the molecular sieves disclosed
in U.S. Pat. No. 4440871 especially the SAPO-11 molecular sieve.
Its characteristic peaks of the X-ray diffraction pattern are the
same as those of the molecular sieve disclosed in U.S. Pat. No.
4440871 which is changed to a certain extent after calcination
at high temperature, i.e., the characteristic of the SAPO-11 molecular
sieve used in the technology disclosed in U.S. Pat. No. 4710485
which uses silicoaluminophosphate molecular sieves as the isomerization
catalyst is that the structure of the molecular sieves is partly
or completely changed after high temperature calcination.
U.S. Pat. No.5087347 discloses a technology using a silicoaluminophosphate
molecular sieves as the isomerization catalyst, in which the silicoaluminophosphate
molecular sieve is selected from mesopore molecular sieve SM-3.
Molecular sieve SM-3 has identical X-ray diffraction pattern with
SAPO-11 molecular sieve disclosed in U.S. Pat. No. 4440871 but
the surface composition of the SM-3 molecular sieve is different
from that of the SAPO-11 molecular sieve, in particular, the surface
is silicon enriched. When the isomerization catalyst with the SM-3
molecular as an acidic component is used in the n-octane conversion
reaction, its activity is enhanced. When the SM-3 molecular sieve
is calcined at a high temperature, its XRD spectra have the features
of the characteristic peaks shown in Table 2 that is, its structure
changes completely.
The crystal structures of all the molecular sieves reported in
the prior art are changed after removing template by calcination,
and therefore it is taken for granted that the crystal structure
of the SAPS-11 molecular sieve should be changed after removing
template by calcination. But the inventors of this invention have
found that by controlling certain synthetic conditions, the structure
of the SAPO-11 molecular sieve can be stabilized, that is, after
removing template by calcination, the structure of the molecular
sieve remains substantially unchanged. Further more, when the SAPO-11
molecular sieve having a stable crystal structure is used as an
acidic component in the catalyst for paraffin hydroisomerization,
the isomerization selectivity and isomerization product yield can
be significantly increased.
OBJECTIVES OF THE INVENTION
Based on the above description, the objective of this invention
is to provide a silicoaluminophosphate molecular sieve with AEL
structure (SAPO-11), the data of the X-ray diffraction pattern of
which is substantially unchanged after removing template by calcination
in comparison with those before removing the template by calcination.
This means that the molecular sieve has superior structure stability.
Another objective of this invention is to provide a method for
preparing said molecular sieve.
A further objective of this invention is to provide a catalyst
containing said SAPO-11 molecular sieve and noble metals. When this
catalyst is used in hydrocarbon hydroisomerization, both isomerization
selectivity and isomerization product yield are significantly increased.
SUMMARY OF THE INVENTION
A SAPO-11 silicoaluminophosphate molecular sieve, its preparation
method, and a catalyst containing the same are provided in this
invention. The X-ray diffraction data of said molecular sieve before
removing the template by calcination are as shown in Table 1 its
molar composition after removing the template by calcination expressed
in anhydrous oxides is Al.sub.2 O.sub.3 :yP.sub.2 O.sub.5 :zSiO.sub.2
in which y has a value of 0.60-1.20 and z has a value of 0.05-1.3
characterized in that after removing the template by calcination,
said molecular sieve has the main X-ray diffraction data as listed
in Table 3 and the crystal structures of the molecular sieve before
and after removing the template by calcination are substantially
the same. Said catalyst is composed of 10-85% by weight of said
SAPO-11 molecular sieve, 0.05-1.5% by weight of Pd or Pt, and alumina
in balance. In comparison with similar catalysts in the prior art,
both isomerization selectivity and product yield are significantly
increased when the catalyst of this invention is applied in hydrocarbon
hydroisomerization reaction.
DETAILED DESCRIPTION OF THE INVENTION
The major X-ray diffraction peaks of the silicoaluminophosphate
molecular sieve with AEL structure (SAPO-11) provided in this invention
before removing the template by calcination are as listed in Table
1. Its molar composition after removing the template by calcination
expressed in anhydrous oxides is Al.sub.2 O.sub.3 :yP.sub.2 O.sub.5
:zSiO.sub.2 in which y has a value of 0.60-1.20 z has a value
of 0.05-1.3 characterized in that its X-ray diffraction data after
removing the template by calcination are as listed in Table 3 in
which the conditions of said calcination are the conventional conditions
used in the prior art for removing the template in this class of
molecular sieves. The molar composition of the silicoaluminophosphate
molecular sieve with AEL structure (SAPO-11) provided in this invention
before removing the template by calcination expressed in anhydrous
oxides is xR:Al.sub.2 O.sub.3 :yP.sub.2 O.sub.5 :zSiO.sub.2 wherein
R is the organic template presented in the channels of the molecular
sieve, and may be an organic template conventionally used in the
prior art, with di-n-propylamine or di-isopropylamine or their mixture
being preferred; x has a value of 0.01-0.35 preferably 0.03-0.25;
y has a value of 0.60-1.20 preferably 0.75-1.05; and has a value
of 0.05-1.3 preferably 0.1-1.1.
The positions of the XRD peaks of the silicoaluminophosphate molecular
sieve provided in this invention before calcination are the same
as those of the aluminophosphate molecular sieve with AEL structure
(its main diffraction peaks are as listed in Table 1), indicating
that it has AEL crystal structure. From the data of Table 3 it
can be seen that the XRD peaks of the molecular sieve after calcination
have substantially the same positions as those of the molecular
sieve before calcination, though the intensities of the XRD peaks
are slightly different. This indicates that the crystal structure
of the molecular sieve provided in this invention is very stable,
its crystal structures are substantially the same before and after
calcination.
TABLE 3 2.theta. d 100 .times. I/I.sub.0 8.00-8.10 11.04-10.91
s 9.45-9.60 9.35-9.21 s 13.05-13.15 6.78-6.73 m 15.70-15.90 5.64-5.57
m 20.20-20.40 4.39-4.35 m 21.15-21.65 4.20-4.10 vs 22.23-22.39 (doublet)
3.99-3.97 m 22.73-22.90 (doublet) 3.91-3.88 m 23.28-23.31 3.82-3.81
m *m: 20-70 s: 70-90 vs: 90-100
The method provided in this invention for synthesizing silicoaluminophosphate
molecular sieves with AEL structure comprises: mixing an aluminum
source, a silicon source, a phosphorus source, and an organic template
to make a gelatinous reaction mixture with a molar composition of
aR: Al.sub.2 O.sub.3 : bP.sub.2 O.sub.5 : cSiO.sub.2 : dH.sub.2
O, then crystallizing the mixture by steam treating, and filtering,
washing, drying, and calcining the crystallized product, characterized
in that said gelation temperature is in a range of 25-60.degree.
C., preferably 28-42.degree. C., more preferably 30-40.degree.C.,
said crystallization conditions are a temperature range of 140-190.degree.
C., preferably 150-180.degree. C., more preferably 160-175.degree.
C., a autogenous pressure, and a duration of 4-60 hours, preferably
10-40 hours; a has a value of 0.2-2.0 preferably 0.3-1.5 more
preferably 0.5-1.0; b has a val of 0.6-1.2 preferably 0.8-1.1;
c has a value of 0.1-1.5 preferable 0.3-1.2; d has a value of 15-50
preferably 20-40 more preferably 25-35.
Said sources of aluminum, silicon and phosphorus, and organic template
in the method provided in this invention are the corresponding raw
materials typically used in the prior art. Said aluminum source
includes aluminum hydroxide, hydrated alumina, aluminum isopropoxide
or aluminum phosphate; said silicon source includes solid silica
gel or silica sol; said phosphorus source includes phosphoric acid
or aluminum phosphate; and said organic template includes di-n-propylamine,
di-isopropylamine or their mixture.
In the method provided by this invention, said calcination conditions
are the conditions typically used in the prior art, in which the
preferred conditions are at 500-650.degree. C. for 2-10 hours.
The key of the method provided in this invention is that the gelation
temperature of the raw materials is controlled at an adequate range
slightly higher than the room temperature, and at the same time,
the crystallization temperature is controlled at a relatively low
temperature range. If the gelation temperature exceeds the range
provided in this invention, or the crystallization temperature is
higher than 200.degree. C., the structure stabilized SAPO-11 of
this invention can not be obtained.
The molecular sieve provided in this invention can be used as a
component of the catalysts for hydrocarbon isomerization, catalytic
dewaxing, freezing point depression of diesel oil or lubricant oil,
etc, especially can be used as a catalyst for hydrocarbon hydroisomerization
after supporting noble metals. In order to make the molecular sieve
into a metal containing bifunctional catalyst, the molecular sieve
can be firstly calcined to remove template, and then impregnated
with metal components, or firstly impregnated with metal components,
and then calcined to remove template. The noble metal can be Pt,
Pd, or the mixture thereof.
The silicoaluminophosphate molecular sieve with AEL structure provided
in this invention or obtained by the method provided in this invention
has superior structural stability, that is, after removing the template
by calcination, its XRD pattern data are substantially unchanged
in comparison with those before removing the template by calcination.
In comparison with the catalysts containing molecular sieves obtained
with the prior art, when this molecular sieve is impregnated with
palladium or platinum components and used for hydrocarbon hydroisomerization
reaction, the isomerization selectivity and product yield are significantly
increased.
The hydrocarbon hydroisomerization catalyst provided by this invention
is comprised of 10-85 wt. % of silicoaluminophosphate molecular
sieve with AEL structure (SAPO-11), 0.05-1.5 wt. % of Pd or Pt,
and alumina in balance, wherein the molar composition of said SAPO-11
molecular sieve expressed in anhydrous oxides is Al.sub.2 O.sub.3
: (0.60-1.20) P.sub.2 O.sub.5 : (0.05-1.3) SiO.sub.2 and characterized
in that the main X-ray diffraction pattern data of said SAPO-11
molecular after removing the template by calcination are as listed
in Table 3. Said calcination conditions are the conventional conditions
in the prior art for removing the organic template in the same class
of molecular sieves.
The preferred catalyst provided in this invention is composed of
20-80 wt. % of said SAPO-11 molecular sieve, 0.1-1.2 wt. % Pd or
Pt, and a balanced amount of alumina.
The method provided in this invention for preparing the catalyst
is the conventional impregnation method in the prior art, which
comprises: mixing, kneading, and molding said SAPO-11 molecular
sieve, a precursor of alumina, deionized water, and nitric acid;
drying and calcining the formed product; supporting a compound of
Pd or Pt or their mixture by impregnation; drying and calcining
the impregnated support to yield the catalyst of this invention,
wherein said precursor of alumina may be a precursor commonly used
in the prior art, which converts to .gamma.-Al.sub.2 O.sub.3 after
calcination, no other limitation being placed on by this invention.
The precursor can be one or several compounds selected from the
group consisting of amorphous aluminum hydroxide, pseudo-beohmite,
alumina tri-hydrate and bayerite, wherein pseudo-beolimite is preferred.
Said alumina in this invention is the alumina obtained by calcining
the above precursors at 400-700.degree. C. for 1-5 hours.
Said SAPO-11 molecular sieve can be calcined to remove the organic
template either before, or after said catalyst is molded by extruding.
No matter the calcination proceeds before or after extruding, the
molecular sieves in the catalysts of this invention can all keep
the stable crystal structure. Said calcination conditions for removing
the template are those typically used in the prior art, in which
the preferred conditions are keeping consistent at 500-650.degree.
C. for 2-10 hours.
The catalyst provided in this invention can be used for isomerization,
catalytic dewaxing of hydrocarbon, freezing point hydro-depression
of diesel oil or lubricant oil, etc., especially for hydroisomerization
of the lubricant oil with a boiling range of 350-580.degree. C.
and the diesel oil with a boiling range of 160-400.degree. C. In
order to make the molecular sieve into a metal containing to bifunctional
catalyst, the molecular sieve can be firstly calcined to remove
template, and then impregnated with a metal component, or firstly
impregnated with a metal component, and then calcined to remove
the template.
Since the silicoaluminophosphate molecular sieve with AEL structure
provided by this invention has superior structure stability, which
is shown by its substantially unchanged data of the XRD pattern
after removing the template by calcination in comparison with those
before removing the-template by calcination. Compared with the catalysts
in the prior art, the catalyst displays higher isomerization selectivity
and isomerization product yield when used in hydroisomerization
of hydrocarbon.
This invention will further be illustrated by the following examples.
The compositions of the molecular sieves in the examples and comparative
examples are detected by X-ray fluorescence spectroscopy.
ILLUSTRATION BY EXAMPLES
Example 1-2
145.3 g of phosphoric acid (containing 85 wt % of H.sub.3 PO.sub.4
the same below) and 217.6 g of deionized water were added into a
gelation autoclave in a water-bath at 35.degree. C. and mixed by
stirring to uniformity, and after stirring for 30 min, 99.2 g of
hydrated alumina (i.e., pseudo-boehmite containing 72 wt % Al.sub.2
O.sub.3 a commodity of the Catalyst Plant of Baling Petrochemical
Corporation, China, the same below) was added and mixed by stirring
for 2 hour. Subsequently, 14.17 g of di-n-propylamine (chemically
pure, the same below ) and 21.25 g of di-isopropylamine (chemically
pure, the same below) were added into the aforesaid gelation autoclave
after mixing to uniformity, and mixed again by continuous stirring
for 2 hours. Finally, 64.62 g of silica sol (containing 26 wt %
of SiO.sub.2 a commodity of the Changhong Chemical Plant, Beijing,
the same below) was added and stirred thoroughly for 2 hours, and
thus a reaction mixture was prepared. A part of the mixture was
sealed in a stainless steel crystallization autoclave, then crystallized
at 160.degree. C. and the autogenous pressure for 24 hours. The
crystallized product was then filtered, washed, and dried at 100-110.degree.
C. to obtain a molecular sieve product as raw powder. A part of
the crystallized product was detected by X-ray powder diffraction
(the apparatus is a Bruker D5005 model, Germany), and the results
are coincident with the data listed in Table 1. This denotes that
the synthesized molecular sieve by the method of this invention
is a molecular sieve having AEL structure.
A part of the molecular sieve sample as raw powder was heated in
a muffle furnace to a temperature of 550.degree. C. and kept constant
for 3 hours, then cooled automatically in air to the room temperature.
The calcined sample was detected by X-ray powder diffraction, and
the resulting data are listed in Table 4. This result proves that
the structure of the unit cell of the molecular sieve remains substantially
unchanged after calcination. The molar composition of the molecular
sieve after calcination is Al.sub.2 O.sub.3 : 0.85P.sub.2O.sub.5
: 0.55SiO.sub.2.
Said molecular sieve as raw powder obtained above was mixed with
hydrated alumina (the same as above) in a weight ratio of molecular
sieve: hydrated alumina=70:30 (dry basis), then the mixture was
molded by extrusion into cylinders with a diameter of 1.50 mm. Then,
the cxtrudate was dried at 120.degree. C. for 6 hours, and calcined
in a calcining furnace at 550.degree. C. for 6 hours. Said calcined
cylinders were impregnated by saturated impregnation with a Pd[NH.sub.3
].sub.4 Cl.sub.2 solution as an impregnation solution in an amount
of 0.6 wt % of Pd. The product obtained was dried at 120.degree.
C. for 6 hours, and calcined in flowing air at 600.degree. C. for
3 hours. Finally, the cata was crushed to 20-40 mesh particles for
catalyst evaluation. The obtained catalyst is denoted as A.
Another catalyst was also prepared according to the above method,
except that the Pd[NH.sub.3 ].sub.4 Cl.sub.2 solution was replaced
by a H.sub.2 PtCL.sub.6 solution as an impregnation solution. A
catalyst with a Pt content of 0.50 wt % was obtained, which is denoted
as B.
TABLE 4 2 .theta. d 100 .times. I/I.sub.0 8.08 10.93 78.3 9.50
9.30 76.4 13.09 6.76 38.2 13.79 6.42 14.3 15.76 5.62 61.1 20.29
4.372 39.0 21.22 4.183 100.0 22.24 3.994 54.3 (doublet) 22.89 3.881
46.0 (doublet) 23.31 3.813 55.7 24.48 3.364 13.6 24.99 3.560 13.8
26.46 3.366 24.0 28.90 3.087 9.8 29.56 3.020 12.8
Example 3
46.1 g of phosphoric acid and 75.7 g of deionized water were added
into a gelation autoclave in a water bath at 30.degree. C. and mixed
by stirring to uniformity, and after stirring for 30 min, 28.3 g
of hydrated alumina was added and mixed by stirring for 2 hours.
Subsequently, 14.17 g of di-n-propylamine was added into the gelation
autoclave, and 13.85 g of silica sol was added immediately after
the completion of the addition of di-n-propylamine. This mixture
was stirred thoroughly for 2 hours to make a reaction mixture, and
the prepared reaction mixture was sealed into a stainless steel
crystallization autoclave and crystallized at 175.degree. C. and
the autogenous pressure for 24 hours. After that, the crystallized
product was filtered, washed, and dried at 100-110.degree. C. to
obtain a molecular sieve product as raw powder. A part of the product
as raw powder was detected by X-ray powder diffraction, and the
result coincides with the data listed in Table 1. This denotes that
the molecular sieve synthesized by this method is a molecular sieve
with AEL structure.
A part of the above molecular sieve as raw powder was calcined
in a muffle furnace at 550.degree. C. for 3 hours, then cooled in
air automatically to the room temperature. The calcined sample was
detected by X-ray powder diffraction, and the result data coincide
with the data listed in Table 3. This proves that the structure
of the unit cell of the molecular sieve remains substantially unchanged
after calcination. The molar composition of the molecular sieve
after calcination is Al.sub.2 O.sub.3 : 0.92P.sub.2O.sub.5 : 0.40SiO.sub.2.
The molecular sieve as raw powder obtained in Example 3 was prepared
into a catalyst according to the same method as in Example 1 except
that the Pd content of the catalyst was 0.50 wt. %. The obtained
catalyst is denoted as C.
Example 4-5
46.1 g of phosphoric acid and 58.6 g of deionized water were added
into a gelation autoclave in a water bath at 30.degree. C. and mixed
by stirring to uniformity, and after stirring for 30 min, 28.3 g
of hydrated alumina was added and mixed with stirring for 2 hours.
Subsequently, 14.17 g of di-n-propylamine was added into the gelation
autoclave, and 36.92 g of silica sol was added immediately after
the completion of the addition of di-n-propylamine. This mixture
was stirred thoroughly for 2 hours to make a reaction mixture, and
the prepared reaction mixture was sealed into a stainless steel
crystallization autoclave and crystallized at 175.degree. C. and
the autogenous pressure for 24 hours. After that, the crystallized
product was filtered, washed, and dried at 100-110.degree. C. to
obtain the molecular sieve product as raw powder. A part of the
crystallized product was detected by X-ray powder diffraction, and
the result coincides with the data listed in Table 1. This denotes
that the molecular sieve synthesized by this method is a molecular
sieve with AEL structure.
A part of the above molecular sieve as raw powder was calcined
in a muffle furnace at 550.degree. C. for 3 hours, then cooled in
air automatically to the room temperature. The calcined sample was
detected by X-ray powder diffraction, and the result data coincide
with the data listed in Table 3. This proves that the structure
of the unit cell of the molecular sieve remains substantially unchanged
after calcination. The molar composition of the molecular sieve
after calcination is Al.sub.2 O.sub.3 : 0.90P.sub.2O.sub.5 : 1.02SiO.sub.2.
The molecular sieve as raw powder obtained in Example 4 was prepared
into a catalyst according to the same method as in Example 1 except
that the Pd content of the catalyst is 0.30 wt. %. The obtained
catalyst is denoted as D.
The molecular sieve as raw powder obtained in Example 4 was prepared
into a catalyst again according to the same method as in Example
1 except that the Pd content of the catalyst was 1.00 wt. %. The
obtained catalyst is denoted as E.
Example 6
46.1 g of phosphoric acid and 83.6 g of deionized water were added
into a gelation autoclave in a water bath at 30.degree. C. and mixed
by stirring to uniformity, and after stirring for 30 min., 81.7
g of aluminum isopropoxide (analytically pure, a commodity of Donghuan
Combined Chemical Plant, Beijing) was added and mixed by stirring
for 2 hours. Subsequently, 14.17 g of di-n-propylamine was added
into the gelation autoclave, and 13.85 g of silica sol was added
immediately after the completion of the addition of di-n-propylamine.
This mixture was stirred thoroughly for 2 hours to make a reaction
mixture, and the prepared reaction mixture was sealed into a stainless
steel crystallization autoclave and crystallized at 175.degree.
C. and the autogenous pressure for 24 hours. After that, the crystallized
product was filtered, washed, and dried at 100-110.degree. C. to
obtain the molecular sieve product as raw powder. A part of the
product as raw powder was detected by X-ray powder diffraction,
and the result coincides with the data listed in Table 1. This denotes
that the molecular sieve synthesized by this method is a molecular
sieve with AEL structure.
A part of the above molecular sieve as raw powder was calcined
in a muffle furnace at 550.degree. C. for 3 hours, then cooled in
air automatically to the room temperature. The calcined sample was
detected by X-ray powder diffraction, and the result data coincide
with the data listed in Table 3. This proves that the structure
of the unit cell of the molecular sieve remains substantially unchanged
after calcination. The molar composition of the molecular sieve
after calcination is Al.sub.2 O.sub.3 : 0.90P.sub.2 O.sub.5 : 0.43SiO.sub.2.
The molecular sieve as raw powder obtained in Example 6 was prepared
into a catalyst according to the same method as in Example 1 except
that the weight ratio of the molecular sieve to alumina was 30:70
by dry basis, and that the Pd content of the catalyst was 0.50 wt.
%. The obtained catalyst is denoted as F.
Example 7
41.5 g of phosphoric acid and 55.4 g of deionized water were added
into a gelation autoclave in a water bath at 38.degree. C. and mixed
by stirring to uniformity, and after stirring for 30 min., 28.3
g of hydrated alumina was added and mixed by stirring for 2 hours.
Subsequently, a mixture of 6.07 g of di-n-propylamine and 4.05 g
of di-isopropylamine was added after mixing to uniformity and, 27.69
g of silica sol was added immediately after the completion of the
addition of the organic amines. Thus derived mixture was stirred
thoroughly for 2 hours to make a reaction mixture, and the prepared
reaction mixture was sealed into a stainless steel crystallization
autoclave and crystallized at 160.degree. C. and the autogenous
pressure for 24 hours. After that, the crystallized product was
filtered, washed, and dried at 100-110.degree. C. to obtain the
molecular sieve product as raw powder. A part of the product as
raw powder was detected by X-ray powder diffraction, and the result
coincides with the data listed in Table 1. This denotes that the
molecular sieve synthesized by this method is a molecular sieve
with AEL structure. A part of the above molecular sieve as raw powder
was calcined in a muffle furnace at 550.degree. C. for 3 hours,
then cooled in air automatically to the room temperature. The calcined
sample was detected by X-ray powder diffraction, and the result
coincides with the data listed in Table 3. This proves that the
structure of the unit cell of the molecular sieve remains substantially
unchanged after calcination. The molar composition of the molecular
sieve after calcination is Al.sub.2 O.sub.3 : 0.91P.sub.2 O.sub.5
: 0.73SiO.sub.2.
The molecular sieve as raw powder obtained in Example 7 was prepared
into a catalyst according to the same method as in Example 1 except
that the weight ratio of the molecular sieve to alumina was 50:50
by dry basis, and that the Pd content was 1.00 wt. %. The obtained
catalyst is denoted as G.
Comparative Example 1
This present comparative example illustrates the effect of the
SAPO-11 molecular sieve and catalyst prepared by the method of the
prior art.
According to the same method and steps described in Example 18
of U.S. Pat. No. 4440871 a comparative molecular sieve sample
was synthesized (with a gelation temperature of 200C). This comparative
sample was examined by X-ray powder diffraction before and after
calcination, the result is coincident with the data listed in Table
1 and Table 2 respectively, showing that the structure of the molecular
sieve is apparently changed after calcination. The molar composition
of the molecular sieve after calcination was Al.sub.2 O.sub.3 :
0.88P.sub.2 O.sub.5 : 0.36SiO.sub.2.
The molecular sieve as raw powder of this comparative example was
prepared into a catalyst before calcination according to the same
method in Example 1 the catalyst obtained is denoted as Comparative
Cat.-1.
Comparative Example 2
This present comparative example illustrates the effect of the
molecular sieve synthesized according to the method of the prior
art.
92.2 g of phosphoric acid and 144.6 g of deionized water were added
into a gelation autoclave in a water bath at 20.degree. C. and mixed
by stirring to uniformity, and after stirring for 30 min, 56.7 g
of hydrated alumina was added and mixed by stirring for 2 hours.
Then 36.92 g of silica sol was added and thoroughly stirred for
2 hours. Finally, a mixture of 14.17 g of di-n-propylamine and 14.17
g of di-isopropylamine was added into the gelation autoclave after
mixing to uniformity. The derived mixture was continually stirred
for 2 hours to make a reaction mixture, and a part of the reaction
mixture was sealed into a stainless steel crystallization autoclave
and crystallized at 200.degree. C. and the autogenous pressure for
24 hours. After that, the crystallized product was filtered, washed,
and dried at 100-110.degree. C. to obtain the comparative molecular
sieve product as raw powder. A part of the product as raw powder
was detected by X-ray powder diffraction, and the result coincides
with the data listed in Table 1. This denotes that the molecular
sieve synthesized by this method is a molecular sieve with AEL structure.
A part of the above molecular sieve as raw powder was calcined
in a muffle furnace at 550.degree. C. for 3 hours, then cooled in
air automatically to the room temperature. The calcined sample was
detected by X-ray powder diffraction, and the result proves that
the sample is a mixture of the molecular sieves with space groups
of Ima2 and Pna2.sub.1 rather than a pure molecular sieve sample
of space group Ima2. The molar composition of the molecular sieve
after calcination is Al.sub.2 O.sub.5 : 0.83P.sub.2 O.sub.5 : 0.50SiO.sub.2.
The present comparative sample as raw powder was prepared into
a catalyst before calcination according to the same method as in
Example 1 and the obtained catalyst is denoted as Comparative Cat.-2.
Example 8
This example is for illustrating the effects of the catalysts of
the present invention and the comparative catalysts when used in
paraffin hydroisornerization.
The catalyst evaluation was carried out on a pulse micro-reactor.
The parameters of the experiment were: catalyst loading was 0.10
g; the particle size of the catalyst was 20-40 mesh; the reactant
was n-octane (C.sub.8.sup.0); the amount of a reactant pulse was
0.5 .mu.l; the carrier gas was hydrogen, and the flow rate of the
carrier gas was 30 m/min. The reaction product was analyzed with
an on-line gas chromatograph. The catalyst was firstly reduced with
hydrogen before reaction evaluation. The reduction conditions were
that the temperature was raised to 500.degree. C. in a rate of 5.degree.
C./min. by temperature programmed heating and kept constant at 500.degree.
C. for 2 hours. The reaction temperature was 360.degree. C.
The target products were the isomerization products of C.sub.8.sup.0
(i-C.sub.8.sup.0). The evaluation results are listed in Table 5.
TABLE 5 Reaction temperature: 360.degree. C. Content of Metal and
iC.sub.8 iC.sub.8 Catalyst Molecular its loading Conversion Selectivity
Yield No. Sieve % % % % % A 70 0.60% Pd 50.50 91.09 46.00 B 70 0.50%
Pt 52.95 78.87 41.76 C 70 0.50% Pd 55.55 85.02 47.23 D 70 0.30%
Pd 53.65 81.60 43.78 E 70 1.00% Pd 55.59 78.70 43.75 F 30 0.50%
Pd 36.80 89.36 32.88 G 50 1.00% Pd 54.10 84.70 45.82 Comp. Cat.-1
70 0.60% Pd 50.45 62.08 31.32 Comp. Cat.-2 70 0.60% Pd 53.44 72.09
38.52
It can be seen apparently from the evaluation results in Table
5 that, compared with the molecular sieves in the prior art, wherein
the crystal structure is changed before and after calcination, the
bifunctional catalysts with the molecular sieves of the present
invention as acidic active components have significantly higher
selectivity and higher yields for the isomerization products.
Example 9
This example is for illustrating the effect of the catalyst of
the present invention when used in luboil hydroisomerization.
The reaction evaluation was carried out on a pressurized fixed-bed
micro-reactor. The loading of Catalyst C was 20 ml with a particle
size of 20-40 mesh. The feed oil was a tail oil of hydrocracking
having a boiling range of 350-545.degree. C, a pouring point of
30.degree. C., and a viscosity index of 125. The reaction conditions
used were as following: reaction temperature 360.degree. C., reaction
pressure 5.0 MPa, liquid hourly space velocity 1.5 h.sup.-1 hydrogen
flow rate 180 ml/min. The catalyst was firstly reduced with hydrogen
before reaction evaluation. The reduction conditions were that the
temperature was raised in a rate of 5C./min. to 500.degree. C. by
temperature programmed heating and hold for 2 hours, then lowered
to the reaction temperature to proceed the evaluation. The reaction
product was cooled, collected, and fractionated. The product yield
was calculated based on the luboil faction obtained, and the pouring
point (GB/T 3535) and viscosity index (GB/T 2541) were measured.
The evaluation results show that the luboil yield was 84.2%, pouring
point -16.degree. C., and viscosity index 120.
It can be seen apparently from these evaluation results that the
bifunctional catalysts with the molecular sieves of the present
invention as an acidic active component have superior hydroisomerization
performances.
Example 10
This example is for illustrating the effect of the catalysts of
the present invention when used for diesel oil hydroisomerization
for depressing freezing point.
The reaction evaluation was carried out on a fixed-bed micro-reactor,
wherein 20 ml of Catalyst C with a particle size of 20-40 mesh was
loaded. The feed oil has a boiling range of 180-350.degree. C. and
a freezing point of 30.degree. C. The reaction conditions used were
as follows: reaction temperature 360.degree. C., reaction pressure
4.0OMPa, liquid hourly space velocity 1.5 h.sup.-1 and hydrogen
flow rate 180 ml/min. The catalyst was firstly reduced with hydrogen
before reaction evaluation. The reduction conditions were that the
temperature was raised in a rate of 5.degree. C./min. to 500.degree.
C. by temperature programmed heating, and held for 2 hours, then
lowered to reaction temperature to proceed reaction evaluation.
The reaction product was cooled, collected, and fractionated. The
product yield was calculated based on diesel oil fraction obtained,
and the freezing point was measured (GB/T 510). The evaluation results
show that the diesel oil yield is 92.82%, and its freezing point
is -18.degree. C.
It can be seen apparently from these evaluation results that the
bifunctional catalysts with the molecular sieves of the present
invention as an acidic active component have superior hydroisomerization
performances. |