CN1176848C - SAPO-11 molecular sieve catalyst and its preparation method - Google Patents

Abstract

The present invention relates to a method for synthesizing an SAPO-11 molecular sieve catalyzer. Dipropylamine is adopted as a template agent in the prior art, but synthetic product is unstable and easy to form many silicon zones so that the catalytic property is reduced. The present invention adopts cheap diethylamine as the template agent, and the SAPO-11 molecular sieves are synthesized at a higher crystallization temperature and a shorter crystallization time. The molecular sieve has more SAPO zones and higher ratio of medium strong acids to weak acids. After molecular sieves are loaded with precious metals, the selectivity and the yield rate of alkane hydroisomerization reaction are greatly raised with molecular sieves.

Description

SAPO-11 molecular sieve catalyst and preparation method thereof

Technical field:

The invention relates to a SAPO-11 molecular sieve catalyst and a preparation method thereof.

Background technique:

The n-alkanes in hydrocarbon oil, mainly long-chain n-alkanes, must reduce their content in order to improve oil performance. For example, for diesel oil or lubricating oil, the freezing point or pour point can be lowered by removing n-alkanes, which can significantly improve the low-temperature performance; it can also achieve the purpose of increasing the octane number by shape-selective isomerization of gasoline fractions. SAPO-11 molecular sieve has attracted much attention because of its special structure and acid properties, and its excellent hydroisomerization performance after loading noble metals.

SAPO-11 molecular sieve belongs to AEL structure, space group Ima2, elliptical channel size is 0.39×0.63nm. The catalytic performance of SAPO-11 molecular sieve mainly depends on the position and environment where Si enters the framework. If two Si replace one P and one Al into the framework, a Si region is formed, and no active site is generated; if one Si replaces one P into the framework, a SAPO region Si(4Al) is formed, and a Brnsted acid active site is obtained. More strong acid centers corresponding to Si (nAl, n=1, 2, 3) are formed at the junction of SAPO region and Si region. Therefore, controlling the mechanism of Si entering the framework and increasing the amount of stronger active acid centers are the key to the synthesis of SAPO-11 molecular sieves with better performance.

The synthesis of existing AEL molecular sieves, including U.S Pat 4,440,871, U.S Pat 4,701,485, U.S Pat 5,208,005, and U.S Pat No 4,943,424, all use dipropylamine as a template. The conventional synthesis conditions of SAPO-11 are: dipropylamine is used as template, pseudoboehmite is used as aluminum source, phosphoric acid is used as phosphorus source, ethyl silicate or silica sol is used as silicon source, crystallization temperature is 473K, and crystallization time is 24 hours. Many studies have been devoted to improving the sol composition and crystallization conditions, so that more SAPO regions can be formed in the SAPO-11 framework. Using conventional synthesis methods, the synthesis results of SAPO-11 are often not easy to repeat, or more Si regions are easily formed to reduce the catalytic performance, which is not conducive to the industrial scale-up and production of SAPO-11.

Invention content:

The purpose of the invention is to study a high silicon SAPO-11 molecular sieve catalyst and a preparation method thereof.

The purpose of the present invention is to study a kind of SAPO-11 molecular sieve catalyst and preparation method thereof that improves active acid center.

The present invention proves that diethylamine as a template agent is more conducive to the generation of high-silicon-content SAPO-11 molecular sieve framework than dipropylamine through theoretical simulation and energetics results. But because diethylamine is used as a template under conventional synthesis conditions, it is easy to generate CHA or AFI structures, or only SAPO-11 crystals containing more heterocrystals can be obtained. The present invention improves the conventional synthesis method and adopts diethylamine as a template. It increases the crystallization temperature, shortens the crystallization time, and can obtain high-silicon SAPO-11 molecular sieve crystals with more SAPO regions and has good n-dodecane hydroisomerization catalysis after being made into a bifunctional catalyst performance.

When the molar composition of the catalyst of the present invention is calcined to remove the template agent, it is xR: Al ₂ O ₃ : yP ₂ O ₅ : zSiO ₂ when represented by the anhydrous chemical formula of the oxide form, wherein R is the diethylamine template in the molecular sieve crystal channel agent, the value of x is 0.05-0.5, y is 0.60-1.20, and z is 0.05-1.3.

The value of x is 0.10-0.30, y is 0.60-1.20, and z is 0.10-1.10 when the molar composition of the catalyst of the present invention is represented by the anhydrous chemical formula in oxide form before the template agent is removed by roasting.

The synthesis method of the SAPO-11 molecular sieve mentioned in the catalyst provided by the present invention comprises: mixing distilled water, aluminum source, silicon source, phosphorus source and organic templating agent uniformly to make the molar composition aR: Al ₂ O ₃ : bP ₂ O ₅ : cSiO ₂ : dH ₂ O reaction mixture, then gradually increase the temperature to hydrothermally crystallize the mixture, filter, wash and dry the crystallized mixture; wherein the mixing temperature of the raw materials is 15-60°C; The crystallization conditions are hydrothermal crystallization at a temperature of 250-350°C and autogenous pressure for 0.5-15 hours; wherein the value of a is 0.2-2.0, the value of b is 0.6-1.4, the value of c is 0.05-1.5, and the value of d The value is 15~150.

Said aluminum source, silicon source and phosphorus source are corresponding raw materials commonly used in the prior art, and the present invention has no special limitation. The organic template is diethylamine. These raw materials can be: said aluminum source includes aluminum hydroxide, hydrated aluminum oxide, aluminum isopropoxide or aluminum phosphate, said silicon source includes white carbon black, solid silica gel or silica sol, and said phosphorus source includes phosphoric acid or aluminum phosphate , said organic template is diethylamine.

The preferred conditions for the above synthesis method are: the mixing temperature of the raw materials is 20-40°C, and the hydrothermal crystallization is carried out at 260-330°C for 1-12 hours during crystallization, and in the mixture, a is 0.3-1.5, b is 0.75-1.2, c is 0.1-1.1, and d is 15-150.

The better conditions for the above synthesis method are: the reaction mixing temperature is 25-35°C, the crystallization is hydrothermal crystallization at 280-310°C for 1.5-6 hours, a in the mixture is 0.5-1.0, d is 50-100, b , c are the same as above.

The preparation method of the catalyst-loaded noble metal provided by the present invention is carried out according to the existing impregnation method. The method can be: kneading the calcined SAPO-11 molecular sieve powder with the precursor of alumina, nitric acid, deionized water, etc., and then drying and roasting; mixture, and then after drying and roasting, the catalyst of the present invention is obtained; wherein the precursor of aluminum oxide can be commonly used in the prior art to form gamma-Al ₂ O ₃ compound aluminum after roasting; these precursors It may be one or more selected from amorphous aluminum hydroxide, pseudo-boehmite, gibbsite and bayerite, among which pseudo-boehmite is preferred. The alumina mentioned in the catalyst of the present invention is the alumina obtained after the above-mentioned alumina precursor is calcined at 400° C. to 700° C. for 1 to 5 hours.

The above-mentioned SAPO-11 molecular sieve supports noble metal Pd, Pt or a mixture thereof. After supporting noble metals Pd and Pt, it has a very good effect on the selectivity and activity of long-chain alkane hydroisomerization.

In the present invention, diethylamine and dipropylamine can also be used as mixed templates, and the effect is also very good.

The roasting condition of SAPO-11 molecular sieve of the present invention removes templating agent can be the condition that generally adopts in the prior art, but the condition of the present invention is roasting 2～24 hours under 500～650 ℃ of air atmospheres; Calcined at 500-650°C for 2-24 hours under _N2 atmosphere, and then fired at 500-650°C for 2-24 hours in air atmosphere.

The molecular sieve provided by the invention can be used as a catalyst for hydroisomerization of normal alkanes after being loaded with precious metals, and can also be used as a catalyst for aromatization of low-carbon alkanes. In order to prepare the molecular sieve into a dual-functional catalyst with metal and acid centers, the molecular sieve can be roasted to remove the template agent first, and then impregnated with the noble metal, or the molecular sieve can be impregnated with the noble metal first, and then roasted to remove the template agent.

The invention uses diethylamine as a template and adopts a new system to synthesize high-silicon SAPO-11 molecular sieve crystals. Compared with the existing technology, the molecular sieve catalyst significantly expands the SAPO region in the AEL molecular sieve, and has a relatively strong medium-strong acid/weak acid ratio; at high temperatures, Brnsted acid centers are dominant; after the molecular sieve crystal is loaded with precious metals, Compared with the prior art, the isomerization selectivity and isomerization yield are obviously improved.

Detailed ways:

Example 1. 5.0g of pseudoboehmite (water content 30%, Wenzhou Shuanghua Group), placed in 50mL of distilled water and vigorously stirred, slowly added 2.0g of white carbon black (99%, Shanghai Wujing Chemical Factory), 15 ℃ Stir vigorously for 30 minutes; slowly add 3.7mL phosphoric acid (AR, 85%, Shanghai Chemical Reagent Company), and stir vigorously for 40 minutes; slowly add 18mL diethylamine, continue stirring for 10 minutes, put into a stainless steel reactor, and then ℃ to crystallize for 2 hours, take it out, cool, filter, dry at 80°C, slowly heat up, first bake at 550°C for 20 hours under _N2 atmosphere, and then bake at 550°C for 24 hours under air atmosphere to obtain the roasted SAPO -11 samples. The solid sample yield is not less than 90%.

Example 2. 5.0g pseudo-boehmite (water content 30%, Wenzhou Shuanghua Group), placed in 86mL distilled water and vigorously stirred; slowly added 5.5mL phosphoric acid (AR, 85%, Shanghai Chemical Reagent Company) and vigorously stirred for 40 minutes Slowly add 34mL diethylamine, continue to stir for 2 hours, slowly add 3.1g white carbon black (99%, Shanghai Wujing Chemical Factory), stir vigorously for 30 minutes; put into a stainless steel reactor, then crystallize at 260 ° C for 12 hour, take it out, cool, filter, dry at 80°C, slowly raise the temperature, and bake at 550°C for 24 hours in an air atmosphere to obtain the roasted SAPO-11 sample. The solid sample yield is not less than 75%.

Example 3.5.0g pseudo-boehmite (water content 30%, Wenzhou Shuanghua Group), placed in 8.7mL distilled water and stirred vigorously; slowly added 2.5mL phosphoric acid (AR, 85%, Shanghai Chemical Reagent Company) and stirred vigorously for 40 minutes; slowly add 4.4mL diethylamine, continue to stir for 2 hours, slowly add 0.13g white carbon black (99%, Shanghai Wujing Chemical Factory), and stir vigorously for 30 minutes; put it into a stainless steel reaction kettle, and then crystallize at 320 ° C After heating for 1.5 hours, take it out, cool, filter, dry at 80°C, slowly raise the temperature, and bake at 550°C for 24 hours in an air atmosphere to obtain the roasted SAPO-11 sample. The solid sample yield is not less than 80%.

Claims (10)

1. SAPO-11 molecular sieve catalyst is characterized in that when mole before its roasting removed template method is formed anhydrous chemical formulation with oxide form be xR: Al ₂O ₃: yP ₂O ₅: zSiO ₂, wherein R is the diethylamine template in the molecular sieve crystal duct, and the value of x is 0.05～0.5, and y is 0.60～1.20, and z is 0.05～1.3.

2. SAPO-11 molecular sieve catalyst according to claim 1 is characterized in that the value of x was 0.10～0.30 when mole before its roasting removed template method was formed anhydrous chemical formulation with oxide form, and y is 0.60～1.20, and z is 0.10～1.10

3. the preparation method of SAPO-11 molecular sieve catalyst according to claim 1 and 2 is characterized in that synthetic method is: it is aR that diethylamine or diethylamine and dipropyl amine template and aluminium source, silicon source, phosphorus source, distilled water are made homogeneous reaction mixture: Al ₂O ₃: bP ₂O ₅: cSiO ₂: dH ₂O progressively heats up then, with the mixture hydrothermal crystallizing, and filtration, washing, drying, actual conditions is: (1) raw material mixing temperature is 15～60 ℃; (2) crystallization condition is 250～350 ℃ of following crystallization 0.5～15 hour; (3) a is 0.2～2.0 in the mixture, and b is 0.6～1.4, and c is 0.05～1.5, and d is 15～150.

4. the preparation method of SAPO-11 molecular sieve catalyst according to claim 3 is characterized in that synthesis condition is: (1) raw material mixing temperature is 20～40 ℃; (2) crystallization condition is 260～330 ℃ of following hydrothermal crystallizings 1～12 hour; (3) a is 0.3～1.5 in the mixture, and b is 0.75～1.2, and c is 0.1～1.1, and d is 15～150.

5. the preparation method of SAPO-11 molecular sieve catalyst according to claim 4 is characterized in that synthesis condition is: (1) raw material mixing temperature is 25～35 ℃; (2) crystallization condition is 280～310 ℃ of following hydrothermal crystallizings 1.5～6 hours; (3) a is 0.5～1.0 in the mixture, and d is 50～100.

6. the preparation method of SAPO-11 molecular sieve catalyst according to claim 3, it is characterized in that will make the roasting of SAPO-11 molecular sieve remove after the template and the precursor of aluminum oxide and nitric acid, deionized water mixing moulding, drying, roasting, use pickling process load P d, Pt metallic compound or its mixture again.

7. the preparation method of SAPO-11 molecular sieve catalyst according to claim 6, the precious metal that it is characterized in that the pickling process load is Pd or Pt, or their mixture.

8. the preparation method of SAPO-11 molecular sieve catalyst according to claim 3 is characterized in that template is diethylamine and dipropyl amine mixed templates.

9. the preparation method of SAPO-11 molecular sieve catalyst according to claim 3, it is characterized in that the removed template method condition is: roasting is 2～24 hours under 500～650 ℃ of air atmospheres; Perhaps 500～650 ℃ of roastings 2～24 hours under nitrogen atmosphere, roasting 2～24 hours under 500～650 ℃ of air atmospheres again.

10. according to the application of claim 1 or 3 described SAPO-11 molecular sieve catalysts as the alkane hydroisomerization.