CN105645428B - The preparation method of the molecular sieves of SSZ 32 with mesoporous micropore graded structure - Google Patents

Abstract

A preparation method of SSZ-32 molecular sieve with mesoporous-microporous hierarchical structure is to homogenize and mix aluminum source, sodium hydroxide and deionized water, add template agent and silicon source, homogenize and mix again; Starch is added to obtain the initial gel mixture, aged and crystallized, the crystallized solid product is separated, washed and dried to obtain the original powder of SSZ-32 molecular sieve; the original powder of SSZ-32 molecular sieve is roasted to obtain the mesoporous-microporous Graded structure SSZ‑32 molecular sieve. The invention has the advantages of simple preparation, good catalytic performance and low cost.

Description

Preparation method of SSZ-32 molecular sieve with mesoporous-microporous hierarchical structure

Field

The invention relates to a preparation method of SSZ-32 silicon-aluminum molecular sieve with mesopore-micropore hierarchical structure.

technical background

SSZ-32 molecular sieve is similar to ZSM-23 silicon-aluminum molecular sieve, and its topology is MTT medium-pore molecular sieve. US Patents 5,252,527 and 5,053,373 disclose a method for preparing SSZ-32 molecular sieves using N-lower alkyl-N'-isopropyl-imidazolium hydroxide as a template. Due to its suitable acidity and unique pore structure, SSZ-32 molecular sieve has excellent performance in the skeletal isomerization reaction of normal alkanes, so it has been widely used in the field of petrochemical industry, especially in the isomerization dewaxing of lubricating oil base oil. received widespread attention.

The main component of wax in lubricating base oil is long-chain normal alkanes with high melting point, which has high pour point and poor low temperature fluidity. These properties can be improved by converting n-paraffins to branched-chain alkanes through hydroisomerization. Due to the relatively large molecular size of the wax, its isomerization reaction on the catalyst mainly occurs at the pores of the catalyst, and only the active centers located near the pores of the molecular sieve can be truly utilized. Therefore, a highly active long-chain n-paraffin isomerization catalyst requires that the molecular sieve used have a large number of exposed pores.

Chinese patent application CN1942560A discloses a method for small-grain SSZ-32 molecular sieves. Alkali metal oxides or hydroxides, alkylamines, N-lower alkyl-N'-isopropyl-imidazolium, aluminum oxides (aluminum oxides are covalently dispersed in silica, using a Aluminum-coated silica sol) and silicon oxide are used as raw materials to produce SSZ-32 with small grains. Chinese patent application CN103153860A discloses a method for preparing small-grained SSZ-32 in the absence of amine components. The reaction raw materials of the method include: at least one silicon oxide active source, at least one aluminum oxide Active source (alumina source provides alumina that can be covalently dispersed on silica), at least one alkali metal active source, hydroxide ion and organic template agent, the average molecular sieve length of the synthesized SSZ-32 About 10-40nm.

In addition to reducing the grain size of molecular sieves, manufacturing larger mesoporous channels (2-50nm) in molecular sieve grains to form a hierarchical structure can also increase the number of exposed pores. Although the small-grain SSZ-32 molecular sieve increases the number of exposed pores, the resulting large non-confined external specific surface area will intensify the non-selective isomerization reaction, which will lead to an increase in cracked products and reduce the yield of lubricating base oil , Deterioration of the viscosity index and volatile performance of the base oil.

Contents of the invention

In order to solve the above-mentioned technical problems, the object of the present invention is to provide a method for preparing SSZ-32 molecular sieve with simple preparation, good catalytic performance, and low-cost mesoporous-microporous hierarchical structure.

The invention synthesizes a class of molecular sieves with a hierarchical structure by adding starch to regulate the synthesis path of the SSZ-32 molecular sieve. Starch is rich in hydroxyl groups, and forms a sponge-like structure by itself at the aging temperature. At the same time, the hydroxyl groups interact with the molecular sieve silica-alumina structure, and finally form a mesoporous-microporous hierarchical composite structure. The mesoporous channel structure is produced after calcination to remove starch. The SSZ-32 molecular sieve synthesized by the method is based on the MTT microporous structure and contains abundant mesopores in and between crystal grains, and has a large mesopore-confined specific surface area and mesopore volume.

Preparation method concrete steps of the present invention are as follows:

(1) The aluminum source, sodium hydroxide, and deionized water are homogenized and mixed;

(2) Add templating agent and silicon source to the mixture of step (1), homogenize and mix again;

(3) adding starch to (2) mixture to obtain initial gel mixture;

(4) aging the initial gel mixture in step (3), and then crystallizing, separating, washing and drying the crystallized solid product to obtain the original powder of SSZ-32 molecular sieve;

(5) Roasting the former powder of SSZ-32 molecular sieve to obtain SSZ-32 molecular sieve with mesoporous-microporous hierarchical structure;

_In the synthesis process, the silicon source is calculated as _SiO2 , the aluminum source is calculated as _Al2O3 , the _sodium hydroxide is calculated as ^OH- , and the starch is calculated as _C6H10O5 . _The molar ratio of each addition is controlled as follows:

SiO ₂ : Al ₂ O ₃ : Templating agent: OH ⁻ : C ₆ H ₁₀ O ₅ : Deionized water = 1.0: 0.01-0.05: 0.01-0.5: 0.05-1.5: 0.1-0.6: 5-150.

As mentioned above, the chemical formula of starch is [(C ₆ H ₁₀ O ₅ ) _n ]. The starch used can be one or more of corn starch and potato starch

The aluminum source used above can be one or more of sodium aluminate, aluminum sulfate, aluminum isopropoxide, and aluminum isobutoxide, and the silicon source used can be silica sol, white carbon black, ethyl orthosilicate One or more of esters, the template used can be one or more of isobutylamine, diisobutylamine, diisopropylamine, N,N'-diisopropylimidazolium hydroxide .

The mixing process of steps (1), (2) and (3) as mentioned above is carried out at 20-50°C.

In step (4) above, the aging temperature can be controlled at 90-140° C., the aging time can be controlled at 1-8 hours, the crystallization temperature can be controlled at 160-260° C., and the crystallization time can be controlled at 0.5-6 days.

The calcination temperature in step (5) above can be controlled at 500-600° C., and the calcination time can be controlled at 5-12 hours.

The technical indicators for preparing SSZ-32 molecular sieve with mesoporous-micropore hierarchical structure in the present invention are that the specific surface area is 200-360m ² /g, the micropore area is 120-190m ² /g, and the mesoporous area is 110-180m ² /g , Mesopore average pore size of 12-20nm.

In the hydroisomerization reaction of linear C20-C30 alkanes, compared with traditional SSZ-32 molecular sieves, SSZ-32 molecular sieves with hierarchical structure have similar yields of isomerization products, and the multi-branched products are compared with traditional SSZ-32 molecular sieves. The proportion of single-chain branched products is greatly increased, which helps to reduce the pour point of the product.

The advantages of the present invention compared with the prior art are as follows:

1. The synthesis method uses cheap starch to realize the synthesis of the mesoporous-microporous hierarchical structure SSZ-32, which is conducive to increasing the mesoporous area of the SSZ-32 molecular sieve, and is conducive to the large-scale application of the hierarchical structure SSZ-32 molecular sieve.

2. By selecting different types of starch and adjusting the types and proportions of branched chain molecules and linear chain molecules in starch, it is relatively easy to control the structure of mesopores in the hierarchical structure SSZ-32.

Detailed ways

Example 1

Under stirring at 30°C, add 0.64g of sodium aluminate and 1.2g of sodium hydroxide into 50ml of deionized water for homogenization and mixing, add 1.97g of isobutylamine, then add 5.6g of white carbon black, and homogenize and mix again for one hour. 2.5 g of corn starch was added to the obtained mixture, the temperature of the system was raised to 90° C., and the mixture was aged with stirring for 8 hours. Finally, the obtained mixture was put into a stainless steel reaction kettle lined with polytetrafluoroethylene, statically crystallized at 160°C for 144 hours, taken out, cooled, filtered, and dried at 80°C to obtain the molecular sieve powder. Calcined at 500°C for 12 hours in an air atmosphere, the SSZ-32 molecular sieve with the final hierarchical structure (the total BET specific surface area is 269m ² /g, the micropore area is 145m ² /g, the mesopore area is 124m ² /g, The average pore diameter of mesopores is 12nm).

Example 2

Under stirring at 30°C, add 0.64g of sodium aluminate and 1.2g of sodium hydroxide into 50ml of deionized water for homogenization and mixing, add 3.48g of diisobutylamine, then add 5.6g of white carbon black, and homogenize and mix again for one hour . 4.5 g of corn starch was added to the obtained mixture, the temperature of the system was raised to 120° C., and the mixture was aged with stirring for 4 hours. Finally, the obtained mixture was put into a stainless steel reaction kettle lined with polytetrafluoroethylene, statically crystallized at 200°C for 24 hours, taken out, cooled, filtered, and dried at 80°C to obtain the molecular sieve powder. Calcined at 550°C for 5 hours in an air atmosphere, the SSZ-32 molecular sieve with the final hierarchical structure (the total BET specific surface area is 336m ² /g, the micropore area is 163m ² /g, the mesopore area is 173m ² /g, The average pore diameter of mesopores is 14nm).

Example 3

Under stirring at 20°C, add 1.10g of aluminum isopropoxide and 1.8g of sodium hydroxide into 50ml of deionized water for homogenization and mixing, add 1.97g of diisopropylamine, then add 22.2g of silica sol (SiO ₂ 25wt%), and again Homogenize and mix for one hour. Add 5.5 g of corn starch, raise the temperature of the system to 140° C., and stir and age for 1 hour. Finally, the obtained mixture was put into a stainless steel reaction kettle lined with polytetrafluoroethylene, statically crystallized at 200°C for 24 hours, taken out, cooled, filtered, and dried at 80°C to obtain the molecular sieve powder. Calcined at 600°C for 5 hours in an air atmosphere, the SSZ-32 molecular sieve with the final hierarchical structure (the total BET specific surface area is 355m ² /g, the micropore area is 188m ^{2 /g, the mesopore area is 167m 2 /} g, The average pore diameter of mesopores is 14nm).

Example 4

Under stirring at 50°C, 1.20 g of aluminum isobutoxide and 1.8 g of sodium hydroxide were added to 50 ml of deionized water. Then the solution was added, and after the solution was homogenized, 2.87 g of N,N'-diisopropylimidazolium hydroxide was added, and then 18.7 g of ethyl orthosilicate was added, and homogenized again for one hour. 4.5 g of corn starch was added, the temperature of the mixture was raised to 100° C., and the mixture was stirred and aged for 4 hours. Finally, the obtained mixture was put into a stainless steel reaction kettle lined with polytetrafluoroethylene, statically crystallized at 190°C for 96 hours, taken out, cooled, filtered, and dried at 80°C to obtain the molecular sieve powder. Calcined at 600°C for 8 hours in an air atmosphere, the SSZ-32 molecular sieve with the final hierarchical structure (the total BET specific surface area is 234m ² /g, the micropore area is 124m ² /g, the mesopore area is 110m ² /g, The average pore diameter of mesopores is 15nm).

Example 5

Using the above preparation process of Example 4, the aging time was 1 hour, the aging temperature was 140° C., the crystallization time was 24 hours, and the crystallization temperature was 260° C. (stainless steel reactor without polytetrafluoroethylene lining). Finally, the total BET specific surface area of SSZ-32 molecular sieve with hierarchical structure is 272m ² /g, the micropore area is 163m ² /g, the mesopore area is 109m ² /g, and the average mesopore diameter is 20nm.

Example 6

Using the preparation process of the above-mentioned Example 1, the template agent is a mixture of isobutylamine and diisopropylamine, wherein isobutylamine is 1.2 g, and diisopropylamine is 0.77 g. Finally, the total BET specific surface area of SSZ-32 molecular sieve with hierarchical structure is 313m ² /g, the micropore area is 190m ² /g, the mesopore area is 123m ² /g, and the average mesopore diameter is 14nm.

Example 7

Adopt the preparation process of above-mentioned embodiment 6, the addition amount of corn starch is 5.5g. Finally, the total BET specific surface area of SSZ-32 molecular sieve with hierarchical structure is 309m ² /g, the micropore area is 165m ² /g, the mesopore area is 144m ² /g, and the average mesopore diameter is 18nm.

Example 8

Under stirring at 50°C, add 0.29g of aluminum sulfate and 2.2g of sodium hydroxide into 50ml of deionized water for homogenization, add 1.2g of isobutylamine and 0.77g of diisopropylamine, then add 5.6g of white carbon black, and homogenize again Mix for one hour. Add 4.5 g of potato starch, raise the temperature of the mixture to 140° C., and stir and age for 1 hour. Finally, the obtained mixture was put into a stainless steel reaction kettle lined with polytetrafluoroethylene, statically crystallized at 200°C for 12 hours, taken out, cooled, filtered, and dried at 80°C to obtain the molecular sieve powder. Calcined at 650°C for 4 hours in an air atmosphere, the SSZ-32 molecular sieve with the final hierarchical structure (the total BET specific surface area is 217m ² /g, the micropore area is 105m ² /g, the mesopore area is 112m ² /g, The average pore diameter of mesopores is 13nm).

comparative example

Under stirring at 50°C, 1.20 g of aluminum isobutoxide and 1.8 g of sodium hydroxide were added to 50 ml of deionized water. Then the solution was added, and after the solution was homogenized, 2.87 g of N,N'-diisopropylimidazolium hydroxide was added, and then 18.7 g of ethyl orthosilicate was added, and homogenized again for one hour. The mixture was warmed to 100°C and aged with stirring for 4 hours. Finally, the obtained mixture was put into a stainless steel reaction kettle lined with polytetrafluoroethylene, statically crystallized at 190°C for 96 hours, taken out, cooled, filtered, and dried at 80°C to obtain the molecular sieve powder. Calcined at 600°C for 8 hours in an air atmosphere, the SSZ-32 molecular sieve with the final hierarchical structure (the total BET specific surface area is 146m ² /g, the micropore area is 135m ² /g, and the mesopore area is 11m ² /g.

The reaction conditions and catalytic results of comparative example and Example 4 in the linear C20-C30 alkane hydroisomerization reaction are as follows:

Reaction conditions: reaction temperature 280°C; liquid space velocity 1.1h ^-1 ; hydrogen-oil ratio 750; reaction hydrogen pressure 4.0Mpa

Comparative example: liquid yield (C5+): 96%; C20-C30 isomerization degree: 100%; C20-C30 isomerization product yield: 51%; Proportion of branched chain products: 0.6

Example 4: Liquid yield (C5+): 95%; C20-C30 isomerization degree: 100%; C20-C30 isomerization product yield: 55%; Ratio of single branched products: 2.2.

Claims (7)

1. a kind of preparation method of the SSZ-32 molecular sieves with mesoporous-micropore graded structure, it is characterised in that including as follows Step：

（1）Silicon source, sodium hydroxide, deionized water are homogenized mixing；

（2）To step（1）Template and silicon source are added in mixture, homogenize mixing again；

（3）To（2）Starch is added in mixture, obtains initial gel mixture；

（4）To step（3）Initial gel mixture carries out burin-in process, then carries out crystallization, by the separation of crystallization solid product, washes Wash, dry, obtain SSZ-32 molecular screen primary powders；

（5）SSZ-32 molecular screen primary powders are calcined, obtain the SSZ-32 molecular sieves of mesoporous-micropore graded structure；

Wherein in building-up process, silicon source is with SiO₂Meter, silicon source is with Al₂O₃Meter, sodium hydroxide is with OH^-Meter, starch is with C₆H₁₀O₅Meter, Each mol ratio for adding material, which controls, is：

SiO₂： Al₂O₃：Template： OH^-： C₆H₁₀O₅：Deionized water=1.0：0.01-0.05：0.01-0.5：0.05-1.5： 0.1-0.6：5-150；

Described silicon source is the one or more in sodium aluminate, aluminum sulfate, aluminium isopropoxide, isobutanol aluminum；

Described silicon source is the one or more in Ludox, white carbon, tetraethyl orthosilicate；

Described step（4）Aging temperature control is 90-140^oC, ageing time control is 1-8 hours.

2. a kind of preparation method of the SSZ-32 molecular sieves with mesoporous-micropore graded structure as claimed in claim 1, its It is characterised by the starch for the one or more in cereal starch and potato starch.

3. a kind of preparation method of the SSZ-32 molecular sieves with mesoporous-micropore graded structure as claimed in claim 1, its It is isobutyl amine, in di-iso-butylmanice, diisopropylamine, N, N '-diisopropyl imidazolium hydroxide to be characterised by described template One or more.

4. a kind of preparation method of the SSZ-32 molecular sieves with mesoporous-micropore graded structure as claimed in claim 1, its It is characterised by described step（1）、（2）、（3）Mixed process is in 20-50^oCarried out in C.

5. a kind of preparation method of the SSZ-32 molecular sieves with mesoporous-micropore graded structure as claimed in claim 1, its It is characterised by that described crystallization temperature control is 160-260^oC, crystallization time control are 0.5-6 days.

6. a kind of preparation method of the SSZ-32 molecular sieves with mesoporous-micropore graded structure as claimed in claim 1, its It is characterised by described step（5）Sintering temperature control is 500-600^oC, roasting time control is 5-12 hours.

7. the SSZ-32 molecular sieves of mesoporous-micropore graded structure prepared by the preparation method as described in claim any one of 1-6, It is characterized in that the specific surface area of mesoporous-micropore graded structure SSZ-32 molecular sieves is 200-360 m²/ g, micropore area are 120-190 m²/ g, mesoporous area are 110-180 m²/ g, mesoporous average pore size are 12-20 nm.