CN106799257A - A kind of alkane isomerization catalyst and preparation method thereof - Google Patents

Abstract

The invention relates to an alkane isomerization catalyst and a preparation method thereof. The catalyst is composed of a silicon-aluminum phosphate composite molecular sieve and one or two of Group VIII noble metals Pt, Pd and Ir with a content of 0.05-5.0 wt%. Said silicoaluminophosphate composite molecular sieve has SAPO-11 and a mixed crystalline phase of silicoaluminophosphate, and its X-ray diffraction pattern has at least the following diffraction peaks, The value represents the diffraction peak position, 8.14±0.2, 9.48±0.2, 12.49±0.1, 13.24±0.2, 15.70±0.2, 16.32±0.2, 17.56±0.2, 17.87±0.1, 19.02±0.2, 20.46±0.2, 21.10±0.2, 21.66±0.1, 22.18± 0.2, 22.60±0.2, 22.76±0.2, 23.22±0.2, 24.74±0.2, 27.86±0.1, 28.49±0.1, 33.03±0.1, 33.41±0.1. When the catalyst involved in the invention is used for the isomerization reaction of alkanes and alkanes, it has better catalytic activity than the catalysts commonly used in the prior art.

Description

A kind of alkane isomerization catalyst and preparation method thereof

technical field

The invention relates to an alkane isomerization catalyst, in particular to an alkane isomerization catalyst composed of a silicon-aluminum phosphate composite molecular sieve and Group VIII noble metal with a content of 0.05-5.0 wt%.

The present invention also relates to a method for preparing the above-mentioned catalyst.

Background technique

Early alkane isomerization catalysts were mainly liquid acid catalysts, such as AlCl ₃ -HCl Freund's catalyst, sulfuric acid and liquid superacid catalyst. These liquid acid catalysts have high isomerization performance, usually at room temperature to 90 °C, can obtain near-equilibrium conversion, but poor selectivity and insufficient stability. In addition, due to strong corrosion of equipment and serious pollution to the environment, it has been basically eliminated at present. Since the 1940s, bifunctional solid catalysts have been gradually developed and applied to the process of alkane isomerization.

The bifunctional solid catalyst is composed of a hydrogenation-dehydrogenation component and an acidic carrier. Hydrogenation-dehydrogenation components can be divided into two categories, including: 1. Single-metal or multi-metal composite systems, such as Pt, Pd, Rh, Ir and Ni; 2. Transition metal sulfide systems, such as Ni-Co, Ni-W, Ni-Mo and other sulfides. Acid supports can be divided into the following three categories: 1. Amorphous single metal oxides or composite oxides, such as Al ₂ O ₃ , SiO ₂ /Al ₂ O ₃ , superacid ZrO ₂ /SO ₄ ² treated with halides ^- , WO ₃ /ZrO ₂ , etc.; 2. Silicon-aluminum molecular sieve series, such as Y, Beta, ZSM-5, ZSM-22, etc.; 3. Aluminum phosphate molecular sieve series, such as SAPO-5, SAPO-11, SAPO-31 and SAPO-41 etc. Compared with amorphous oxides and superacids, molecular sieves have shown excellent performance in terms of shape selectivity, stability, anti-poisoning, and anti-carbon deposition. Therefore, isomerization catalysts based on molecular sieves have been widely used.

Molecular sieves refer to substances with sieving ability in molecular size. Due to its regular pore structure and unique surface properties, it has been widely used in catalysis, ion exchange, adsorption and separation and other fields. The earliest molecular sieve material recognized by mankind is natural zeolite. In the 1940s, Barrer RM and others realized the artificial synthesis of molecular sieves for the first time. Afterwards, a large number of molecular sieve materials were artificially synthesized one after another. However, with the development of industry, many fields require The performance and structure of molecular sieves put forward higher requirements, so the development of new molecular sieve materials is of great significance.

Aluminum phosphate molecular sieve (AlPO ₄ -n) is a new type of molecular sieve material developed in the 1980s. The framework of this type of molecular sieve is strictly composed of PO ₄ ⁺ and AlO ₄ ^- tetrahedrons alternately, and has no exchangeable charges, so it has no acidity, and its application in catalytic reactions is extremely limited. Si-aluminophosphate molecular sieve (SAPO-n) can be produced by isomorphic substitution of silicon on the skeleton of aluminum phosphate molecular sieve, which makes it acidic due to the imbalance of the skeleton charge. At the same time, because the pore structure of AlPO ₄ -n is maintained, SAPO-n has great application prospects in catalysis. At present, a variety of SAPO-n have been applied to chemical industrial processes, especially catalytic processes related to petroleum refining. For example, the application of SAPO-34 in the process of methanol to olefins, and the application of SAPO-11 in the process of diesel upgrading and lubricating oil dewaxing, etc.

The SAPO-11 molecular sieve has an AEL structure, belongs to the orthorhombic crystal system, the space group is Ima2, and the unit cell parameters are Its skeleton is mainly formed by the interweaving of PO ₄ ⁺ , AlO ₄ ^- and SiO ₄ tetrahedra. Its typical X-ray diffraction spectrum data are shown in Table 1 .

surface 1

*Diffraction peak intensity, w-m:<20; m:20~70; s:70~90; vs:90~100

The synthesis of silicoaluminophosphate molecular sieve SAPO-11 can be found in many patent reports, such as US4440871, US4310440, US4943324, US5208005, EP146384, CN99109681 and so on. In these patents, a hydrothermal synthesis method is used to synthesize pure phase SAPO-11. Due to the structural characteristics _of the AEL framework, only weak _acid sites and medium-strong acid sites can be formed on SAPO-11 molecular sieves prepared by various synthesis methods reported so far. It appears at around 180 and 280°C (as shown in Figure 2 ), representing weak acid sites and medium-strong acid sites, respectively. Continuing to increase the amount of silicon substitution can only increase the number of these two acidic sites, but cannot produce stronger acidic sites, that is, a desorption peak around 400°C appears in the NH ₃ -TPD diagram .

When SAPO-11 acts on the isomerization of long-chain alkanes, the performance of the catalyst is determined by the ten-membered ring, one-dimensional straight channel of SAPO-11 and its acidity. The stronger the acidity, the more active the catalyst and the lower the reaction temperature required to achieve the target conversion. Therefore, the synthesis of SAPO-11 with strong acid sites or SAPO-11 composite molecular sieves with strong acid sites may expand the further application of such molecular sieves in isomerization and cracking catalytic processes. The isomerization of alkanes prepared based on this type of molecular sieve will show more excellent performance.

Contents of the invention

The object of the present invention is to provide an alkane isomerization catalyst, which is composed of silicoaluminophosphate composite molecular sieve and Group VIII noble metal; wherein, the mass content of Group VIII noble metal is 0.05-5.0wt%;

Among them, the silicoaluminophosphate composite molecular sieve has micropores of 0.3-0.7nm, BET specific surface area of 100-300m ² /g, pore volume of 0.1-0.5mL/g, and its X-ray diffraction pattern has at least the following diffraction peak,

The 2θ value indicates the position of the diffraction peak, 2θ/°: 8.14±0.2, 9.48±0.2, 12.49±0.1, 13.24±0.2, 15.70±0.2, 16.32±0.2, 17.56±0.2, 17.87±0.1, 19.02±0.2, 20.46±0.2 , 21.10±0.2, 21.66±0.1, 22.18±0.2, 22.60±0.2, 22.76±0.2, 23.22±0.2, 24.74±0.2, 27.86±0.1, 28.49±0.1, 33.03±0.1, 33.41±0.1.

The Group VIII noble metal is one or two or three of Pt, Pd or Ir.

The mass content of the Group VIII noble metal is preferably 0.1 to 2.0 wt%.

The present invention also provides a method for preparing the above-mentioned alkane isomerization catalyst, the steps are as follows:

a) mixing the aluminum source, the phosphorus source and water and stirring evenly to prepare a precursor mixture A; the precursor mixture A is aged at 0-30°C for 0-12h;

b) Add an organic amine to the precursor mixture A after standing and aging, stir until uniform, then add a silicon source, continue stirring until uniform to form a precursor mixture B, in B, aluminum source: phosphorus source: silicon source: organic amine and Al ₂ O ₃ :P ₂ O ₅ :SiO ₂ :organic amine, the molar ratio is 1:0.1～5:0.01～5:0.1～5;

c) heating the prepared precursor mixture B to crystallize under the condition of 120°C-250°C, and the crystallization time is 8-48h;

d) After the crystallization is completed, the reactant is cooled to room temperature, filtered, washed and dried, and the obtained solid is a silicoaluminophosphate composite molecular sieve;

e) Using one or more of the methods of impregnation, precipitation, adding a binder to bond or mechanical pressing to realize the combination of Group VIII noble metal and silicoaluminophosphate composite molecular sieve, and calcining at 400-600°C;

f) Before use, the calcined catalyst is subjected to reduction treatment.

The phosphorus source is one or more of ammonium phosphate, ammonium monohydrogen phosphate or ammonium dihydrogen phosphate in phosphoric acid or phosphate;

The aluminum source is one or two of pseudo-boehmite or hydrated alumina;

The organic amine is one or more of aliphatic amines, aromatic amines, alcohol amines, and quaternary ammonium salts;

The Group VIII noble metal is one or two or three of Pt, Pd or Ir.

The silicon source is one or more of fumed silica, silica sol, water glass, solid silica gel and amorphous silica.

In step a), the preferred condition is that the precursor mixture A is statically aged at 0-25° C. for 0-8 hours.

In step b), in the preferred condition precursor mixture B, the aluminum source: phosphorus source: silicon source: organic amine is based on Al ₂ O ₃ :P ₂ O ₅ :SiO ₂ :organic amine, and the molar ratio is 1:0.5～2 :0.1～1:0.5～2.

In step c), the crystallization temperature is preferably 160°C-220°C, and the crystallization time is 12-36h.

The organic amine described in step d) is preferably an aliphatic amine.

In step e), the combination of Group VIII noble metals and silicoaluminophosphate composite molecular sieves uses metal acids, metal salts, chlorides, ammonia complexes, carbonyl complexes or mixtures thereof of Group VIII noble metals as raw materials.

For the reduction treatment in step f), the reducing atmosphere is hydrogen, or a mixture of hydrogen and inert gas, and the reduction temperature is 100-600°C.

Compared with pure SAPO-11 synthesized by currently known means, the silicoaluminophosphate composite molecular sieve involved in the present invention has stronger acidity and higher acid content.

Therefore, based on pure SAPO-11 prepared by the prior art as a carrier catalyst, the alkane isomerization catalyst prepared by the present invention has the following characteristics:

(1) SAPO-11 crystal phase with high strength, that is, maintaining a large number of ten-membered rings with AEL structure and one-dimensional straight channels; at the same time, it also has a crystal phase of layered silicon aluminum phosphate;

(2) It has a large number of strong acid sites;

(3) When used in the isomerization reaction of long-chain alkanes, the activity is higher, and the reaction temperature required for long-chain alkanes to reach a high conversion rate is lower.

Description of drawings

Fig. 1 is the X-ray diffraction spectrogram of the pure SAPO-11 that comparative example 1 prepares

Figure 2 is the NH ₃ -TPD characterization diagram of pure SAPO-11 prepared in Comparative Example 1

Fig. 3 is the X-ray diffraction spectrum of the silicoaluminophosphate composite molecular sieve in the alkane isomerization catalyst prepared in Example 1 of the present invention

Figure 4 is the NH ₃ -TPD characterization diagram of the silicoaluminophosphate composite molecular sieve in the alkane isomerization catalyst prepared in Example 1 of the present invention

detailed description

The present invention will be further described below in conjunction with specific examples, but it should be pointed out that the content of the present invention is not limited thereto.

Comparative example 1

Weigh 114g aluminum isopropoxide, dissolve it in 200g deionized water, stir and mix evenly; weigh 130g phosphoric acid, dissolve it in 100g deionized water, mix evenly; Precursor mixture A; weigh 57g of di-n-propylamine, add it dropwise to A, and stir evenly; then weigh about 45g of silica sol (30wt%), add it dropwise to A, and stir evenly to form precursor mixture B; Put it into a reaction kettle with a volume of 1L, start to heat up and crystallize, the crystallization temperature is 200°C, and keep it for 24h; after the crystallization is completed, wash and filter the product until the filtrate is neutral, and put the filtered product in an oven at 120°C After drying for 24 hours, pure SAPO-11 molecular sieves were obtained. The X-ray diffraction spectrum is shown in Figure 1 , and the acidic characterization results are shown in Figure 2 ; the X-ray diffraction peak positions are summarized in Table 2 .

Comparative example 2

Take 100g of the pure SAPO-11 molecular sieve prepared in Comparative Example 1 above, mix it with 30g of γ-Al ₂ O ₃ evenly, add 80g of 5wt% HNO ₃ solution, knead, extrude, dry naturally, and then dry at 120°C for 4h, 550°C Calcined at ℃ for 8h to prepare molecular sieve carrier. 100 g of the above support was impregnated with 10 mL of H ₂ PtCl ₆ solution containing 0.05 g/mL of Pt to prepare a 0.5 wt % Pt/SAPO-11 catalyst, coded as A1. The evaluation results of catalytic reactions are shown in Table 3 .

Example 1

Weigh 70g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 130g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; add the phosphoric acid solution dropwise to the pseudo-boehmite in a stirring state The solution forms a precursor mixture A; A is aged at 10°C for 4 hours; weigh 57g of diisopropylamine, add it dropwise to A, and stir evenly; then weigh about 45g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1L, and start crystallization at a temperature of 200°C for 24 hours; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 24 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction spectrum is shown in Figure 3 , and the acidic characterization results are shown in Figure 4 ; the X-ray diffraction peak positions are summarized in Table 2 .

Example 2

Weigh 70g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 130g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; add the phosphoric acid solution dropwise to the pseudo-boehmite in a stirring state The solution forms a precursor mixture A; A is aged at 0°C for 2 hours; weigh 57g of di-n-propylamine, add it dropwise to A, and stir evenly; then weigh about 45g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1L, and start crystallization at a temperature of 200°C for 24 hours; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 20 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction peak positions are summarized in Table 2 .

Example 3

Weigh 70g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 130g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; add the phosphoric acid solution dropwise to the pseudo-boehmite in a stirring state The solution forms a precursor mixture A; A is aged at 0°C for 8 hours; weigh 57g of di-n-propylamine, add it dropwise to A, and stir evenly; then weigh about 23g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1L, and start crystallization at a temperature of 200°C for 24 hours; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 18 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction peak positions are summarized in Table 2 .

Example 4

Weigh 70g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 130g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; add the phosphoric acid solution dropwise to the pseudo-boehmite in a stirring state The solution forms the precursor mixture A; A is aged at 0°C for 6h; weigh 57g of diisopropylamine, add it dropwise to A, and stir evenly; then weigh about 66g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1 L, and start crystallization by heating up, the crystallization temperature is 200°C, and keep for 26 hours; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 24 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction peak positions are summarized in Table 2 .

Example 5

Weigh 70g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 130g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; add the phosphoric acid solution dropwise to the pseudo-boehmite in a stirring state The solution forms the precursor mixture A; A is aged at 5°C for 6h; weigh 57g of diisopropylamine, add it dropwise to A, and stir evenly; then weigh about 66g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1 L, and start crystallization by heating up, the crystallization temperature is 200°C, and keep for 26 hours; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 24 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction peak positions are summarized in Table 2 .

Example 6

Weigh 84g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 130g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; The solution forms a precursor mixture A; A is aged at 0°C for 6 hours; weigh 69g of diisopropylamine, add it dropwise to A, and stir evenly; then weigh about 66g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1 L, and start crystallization by heating up, the crystallization temperature is 200°C, and keep for 26 hours; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 24 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction peak positions are summarized in Table 2 .

Example 7

Weigh 84g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 130g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; The solution forms a precursor mixture A; A is aged at 5°C for 8 hours; weigh 69g of di-n-propylamine, add it dropwise to A, and stir evenly; then weigh about 44g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1L, and start crystallization at a temperature of 200°C for 24 hours; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 24 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction peak positions are summarized in Table 2 .

Example 8

Weigh 84g of pseudo-boehmite, dissolve in 200g of deionized water, stir and mix evenly; weigh 156g of phosphoric acid, dissolve in 100g of deionized water, mix evenly; The solution forms a precursor mixture A; A is aged at 0°C for 7 hours; weigh 69g of di-n-propylamine, add it dropwise to A, and stir evenly; then weigh about 66g of silica sol (30wt%), and add it dropwise to A , and stir evenly to form precursor mixture B; put B into a reaction kettle with a volume of 1L, and start crystallization by heating up, the crystallization temperature is 210°C, and keep for 24h; after the crystallization is completed, wash and filter the product until the filtrate is Neutral, the filtered product was dried in an oven at 120°C for 24 hours to obtain a silicon-aluminum phosphate composite molecular sieve SC1. The X-ray diffraction peak positions are summarized in Table 2 .

X-ray diffraction peak position and intensity of silicoaluminophosphate composite molecular sieve in the embodiment of table 2

sample real

Example number

*Diffraction peak intensity, w-m:<20; m:20~70; s:70~90; vs:90~100

Example 9

Take 100g of the silicoaluminophosphate composite molecular sieve prepared in Example 1, mix it with 30g of γ-Al ₂ O ₃ evenly, add 80g of 5wt% HNO ₃ solution, knead, extrude, and dry naturally, then dry at 120°C for 4 hours, and then dry at 550°C The molecular sieve carrier was prepared by calcining for 8 hours. 100 g of the above carrier was impregnated with 10 mL of H ₂ PtCl ₆ solution containing 0.05 g/mL of Pt to prepare a 0.5 wt % Pt/SC1 catalyst, coded as B1. The evaluation results of catalytic reactions are shown in Table 3 .

Example 10

Take 100g of the silicoaluminophosphate composite molecular sieve SC1 prepared in Example 2, mix it with 30g of γ-Al ₂ O ₃ evenly, add 80g of 5wt% HNO ₃ solution, knead, extrude, dry naturally, and then dry at 120°C for 4h, 550°C Calcined at ℃ for 8h to prepare molecular sieve carrier. 100 g of the above carrier was impregnated with 10 mL of H ₂ PtCl ₆ solution containing 0.05 g/mL of Pt to prepare a 0.5 wt % Pt/SC1 catalyst, numbered B2. The evaluation results of catalytic reactions are shown in Table 3 .

Example 11

Take 100g of the silicon-aluminophosphate composite molecular sieve SC1 prepared in Example 3, mix it with 30g of γ-Al ₂ O ₃ evenly, add 80g of 5wt% HNO ₃ solution, knead, extrude, dry naturally, and then dry at 120°C for 4h, 550°C Calcined at ℃ for 8h to prepare molecular sieve carrier. Impregnate 100 g of the above support with 10 mL of H ₂ PtCl ₆ solution containing 0.05 g/mL Pt and 10 mL of PdCl ₂ solution containing 0.01 g/mL Pd to prepare 0.5 wt % Pt-0.1 wt % Pd/SC1 catalyst, coded as B3. The evaluation results of catalytic reactions are shown in Table 3 .

Example 12

Take 100g of the silicoaluminophosphate composite molecular sieve SC1 prepared in Example 4, mix it with 30g of γ-Al ₂ O ₃ evenly, add 80g of 5wt% HNO ₃ solution, knead, extrude, dry naturally, and then dry at 120°C for 4h, 550°C Calcined at ℃ for 8h to prepare molecular sieve carrier. Impregnate 100 g of the above carrier with 10 mL of H ₂ PtCl ₆ solution containing 0.05 g/mL Pt and 10 mL of PdCl ₂ solution containing 0.01 g/mL Pd to prepare 0.5 wt % Pt-0.1 wt % Pd/SC1 catalyst, numbered B4. The evaluation results of catalytic reactions are shown in Table 3 .

Example 13

Take 100g of the silicoaluminophosphate composite molecular sieve SC1 prepared in Example 5, mix it with 30g of γ-Al ₂ O ₃ evenly, add 80g of 5wt% HNO ₃ solution, knead, extrude, dry naturally, and then dry at 120°C for 4h, 550°C Calcined at ℃ for 8h to prepare molecular sieve carrier. Impregnate 100 g of the above carrier with 10 mL of H ₂ PtCl ₆ solution containing 0.05 g/mL of Pt and 10 mL of PdCl ₂ solution containing 0.01 g/mL of Pd to prepare a 0.5 wt % Pt-0.1 wt % Pd/SC1 catalyst, numbered B5. The evaluation results of catalytic reactions are shown in Table 3 .

Table 3 Evaluation results of different catalysts

catalyst Reaction temperature (°C) Conversion rate(%) Isomerization selectivity (%) Isomerization yield (%) A1 340 65.0 93.3 60.6 B1 330 91.1 80.3 73.2 B2 325 89.7 82.5 74.0 B3 320 90.2 80.7 72.8 B4 330 90.9 79.2 72.0 B5 325 89.5 81.6 73.0

Example 14

Catalytic reaction evaluation:

Raw material: n-dodecane; reaction conditions: 10mL fixed-bed reactor, reaction temperature 300-370°C, reaction pressure 8MPa, space velocity 1h ^-1 , hydrogen-oil ratio 200nL/nL. The catalysts prepared in the above-mentioned Examples 9-13 were respectively used, and the catalyst consumption was 8g, and the evaluation results of each catalyst were listed in Table 3 .

Claims (10)

1. a kind of alkane isomerization catalyst, it is characterised in that：By SAPO composite molecular screen and VIII Race's noble metal composition；

Wherein, the mass content of group VIII noble metals is 0.05~5.0wt%；

Wherein, SAPO composite molecular screen has the micropore of 0.3~0.7nm, and BET specific surface area is 100~300m²/ g, pore volume is 0.1~0.5mL/g, and its X-ray diffraction spectrogram has diffraction at least set forth below Peak,

2 θ values expression diffraction maximum position, 2 θ/°：8.14 ± 0.2,9.48 ± 0.2,12.49 ± 0.1,13.24 ± 0.2, 15.70 ± 0.2,16.32 ± 0.2,17.56 ± 0.2,17.87 ± 0.1,19.02 ± 0.2,20.46 ± 0.2,21.10 ± 0.2, 21.66 ± 0.1,22.18 ± 0.2,22.60 ± 0.2,22.76 ± 0.2,23.22 ± 0.2,24.74 ± 0.2,27.86 ± 0.1, 28.49 ± 0.1,33.03 ± 0.1,33.41 ± 0.1.

2. catalyst as claimed in claim 1, it is characterised in that：The group VIII noble metals be Pt, One or two or three kinds in Pd or Ir.

3. catalyst as claimed in claim 1 or 2, it is characterised in that：The quality of group VIII noble metals Content is 0.1~2.0wt%.

4. the preparation method of the catalyst described in a kind of claim 1, it is characterised in that：Step is as follows：

A) silicon source, phosphorus source and water are mixed and stirred for uniformly being made precursor mixture A；Precursor mixture A exists Still aging 0~12h at 0~30 DEG C；

B) organic amine is added in the precursor mixture A after still aging, silicon source is added after being stirred until homogeneous, Continue to be stirred until homogeneous to form precursor mixture B, in B, silicon source：Phosphorus source：Silicon source：Organic amine is with Al₂O₃: P₂O₅:SiO₂:Organic amine meter, molar ratio is 1:0.1~5:0.01~5:0.1~5；

C) crystallization under the conditions of obtained precursor mixture B being heated into 120 DEG C~250 DEG C, crystallization time is 8~48h；

D) after crystallization terminates, reactant is cooled to room temperature, is filtered, washed and dried, the solid for obtaining is SAPO composite molecular screen；

E) using one or two or more kinds in dipping, precipitation, addition adhesive bond or mechanical press method, The combination of group VIII noble metals and SAPO composite molecular screen is realized, and in 400~600 DEG C of roastings；

F) preceding in use, the catalyst after roasting is by reduction treatment；

Described phosphorus source is the one kind in the ammonium phosphate in phosphoric acid or phosphate, monoammonium phosphate or ammonium dihydrogen phosphate Or more than two kinds；

Described silicon source is one kind or two kinds in boehmite or hydrated alumina；

The group VIII noble metals are one or two or three kinds in Pt, Pd or Ir；

Described organic amine be fatty amine, aromatic amine, hydramine, quaternary ammonium compound in one kind or two kinds with On；

Described silicon source is in gas-phase silica, Ludox, waterglass, solid silicone and amorphous silica One or two or more kinds.

5. according to the preparation method described in claim 4, it is characterised in that：Precursor mixture A in step a) Still aging 0~8h at 0~25 DEG C.

6. according to the preparation method described in claim 4, it is characterised in that：Precursor mixture B in step b) In, silicon source：Phosphorus source：Silicon source：Organic amine is with Al₂O₃:P₂O₅:SiO₂:Organic amine meter, molar ratio is 1: 0.5~2:0.1~1:0.5~2.

7. according to the preparation method described in claim 4, it is characterised in that：Crystallization temperature is in step c) 160 DEG C~220 DEG C, crystallization time is 12~36h.

8. according to the preparation method described in claim 4, it is characterised in that：Described organic amine is fatty amine.

9. according to the preparation method described in claim 4, it is characterised in that：Step e) the group VIIIs are expensive The combination of metal and SAPO composite molecular screen, using the metal acid of group VIII noble metals, metal acid-salt, Chloride, ammino-complex, carbonyl complex or their mixture are raw material.

10. according to the preparation method described in claim 4, it is characterised in that：Original place is gone back described in step f) Reason, reducing atmosphere is hydrogen, or hydrogen and inert gas gaseous mixture, reduction temperature is 100~600 DEG C.