SAPO-11 molecular sieve, its synthetic method and a catalyst...

Details SAPO-11 molecular sieve, its synthetic method and a catalyst... SAPO-11 molecular sieve, its synthetic method and a catalyst...

2001-09-05

2003-07-22

Dunn, Tom (Department: 1725)

Mineral oils: processes and products

Chemical conversion of hydrocarbons

Reforming

C208S134000, C208S135000, C502S208000, C502S213000, C502S214000, C423S305000

Reexamination Certificate

active

06596156

ABSTRACT:

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. 4,310,440) 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
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 Å, b=13.4 Å, and c=8.4 Å, and the one dimensional pore size of its 10-member ring is 3.9×6.3 Å. 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
1
, with the crystal unit cell parameters of a=18.1 ÅA, b=13.8 Å, and c=8.1 Å. 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 &thgr;
d
100 × I/I
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 &thgr;
d
100 × I/I
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. 4,440,871). 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
+
, 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
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. 4,440,871, 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&thgr;=12.8, 16.1, and 21.9°, 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
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&thgr;=9.85, 12.8, 16.1, and 21.95°, and the thorough disappearance of the peaks at 2&thgr;=9.4, 13.1, 15.65, and 21.1° 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
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. 4,943,424 and 5,208,005 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. 4,440,871. 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. 4,310,440 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
2
O
5
: Al
2
O
3
: 40H
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° 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. 4,440,871 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 not

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