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A kind of molecular sieve with hzsm-5silicalite-1 core-shell structure and its preparation method and application

A core-shell structure, molecular sieve technology, applied in molecular sieve catalysts, chemical instruments and methods, crystalline aluminosilicate zeolites, etc., can solve problems such as cumbersome, difficult control, catalyst hole blocking, etc., to improve conversion rate and catalytic effect. , to ensure the effect of compactness

Inactive Publication Date: 2015-08-19
HUNAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The process of carbon pre-deposition technology is difficult to control, and the recovered molecular sieve catalyst needs to repeat the pre-coking operation after roasting and regeneration
Using a simple silicon source, such as tetraethyl orthosilicate, to modify ZSM-5 by chemical vapor deposition or liquid phase deposition to improve para-selectivity requires a cumbersome and complicated process, and it is easy to cause catalyst plugging. hole

Method used

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  • A kind of molecular sieve with hzsm-5silicalite-1 core-shell structure and its preparation method and application

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] According to molar ratio SiO 2 :Al 2 o 3 :TPAOH:TEA:NaOH:H 2 O=1:0.0067:0.1:0.3:0.165:3.8 ratio, 20.03g silica sol (30wt%), 0.446g aluminum sulfate, 8.134g tetrapropylammonium hydroxide (25wt%), 4.476g triethanolamine and 48.06 g deionized water mixed evenly, hydrothermally crystallized at 180°C for 48h, cooled, centrifuged, washed with water, dried and roasted, and deionized with NH 4 NO 3 The solution is subjected to proton exchange, and then dried and calcined to obtain HZSM-5 molecular sieve with Si / Al=75.

[0025] Mix 7.32g of tetrapropylammonium hydroxide (25wt%) into 30ml of 0.3mol / L aqueous solution (pH=13.5), then add 3g of HZSM-5 molecular sieve prepared in the above steps into the solution, ultrasonically disperse for 30min, Treat at 80°C for 3h, then slowly add 2.14g of ethyl silicate, age at 20°C for 3h, then hydrothermally crystallize at 180°C for 48h, cool, centrifuge, wash with water, dry and bake at 540°C to obtain a shell thickness of 40nm The HZ...

Embodiment 2

[0028] Add 3 g of HZSM-5 molecular sieves with Si / Al=75 in Example 1 to 30ml of 0.1mol / L tetrapropylammonium bromide solution, then add 28wt% ammonia water dropwise to adjust the pH to 13.5, and other operations are similar to Example 1, HZSM-5silicalite-1 molecular sieve with core-shell structure was prepared. The performance of the prepared catalyst was evaluated according to the operation similar to that of Example 1. After 1 hour of reaction, the conversion rate of toluene was 34%, and the para-selectivity of xylene was 61%.

Embodiment 3

[0030] According to molar ratio SiO 2 : Al 2 o 3 :TPAOH:TEA:NaOH:H 2 O=1: 0.0013: 0.1: 0.3: 0.165: 3.8, other operations are similar to Example 1, and a HZSM-5silicalite-1 core-shell molecular sieve with a core Si / Al=380 and a shell thickness of 40nm was obtained. The performance of the prepared catalyst was evaluated according to the operation similar to that of Example 1. After 1 hour of reaction, the conversion rate of toluene was 47%, and the para-position selectivity of xylene was 74%. After 3 hours of reaction, the conversion rate of toluene was 46%, and the para-selectivity of xylene was 76%.

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Abstract

The invention provides an HZSM-5@silicalite-1 core-shell structure molecular sieve. The core-shell structure molecular sieve is characterized in that the HZSM-5 is taken as the core of the molecular sieve and total silica silicalite-1 is taken as the shell of the molecular sieve, and the formed shell layer is even and compact, and 10-70nm thick. The invention also provides a preparation method of the HZSM-5@silicalite-1 core-shell structure molecular sieve, and application of the HZSM-5@silicalite-1 core-shell structure molecular sieve in preparing xylene with methyl bromide as a methylating reagent by virtue of methylbenzene catalysis. The core-shell structure molecular sieve provided by the invention has the characteristics such as high crystallinity, high dispersion of particles and regular morphology. The HZSM-5@silicalite-1 core-shell structure molecular sieve provided by the invention is excellent in catalysis activity, para-selectivity and stability if being applied to preparing the xylene by methylating the methylbenzene with the methyl bromide.

Description

【Technical field】 [0001] The invention belongs to the technical field of preparation and application of zeolite catalytic materials. Specifically, it relates to a molecular sieve with HZSM-5silicalite-1 core-shell structure and its preparation method and application. 【Background technique】 [0002] P-xylene is a very important basic chemical raw material, mainly used to manufacture terephthalic acid, which is an important intermediate in the production of polyethylene terephthalate. In addition, p-xylene is also widely used in the fields of pesticides, medicines, solvents and fuels. In 2012, China demanded 13.85 million tons of p-xylene, accounting for 32% of global consumption, and was the world's largest consumer of p-xylene. However, China's total production capacity of p-xylene was only 8.8 million tons, with a self-sufficiency rate of 63%. [0003] P-xylene can be prepared by methods such as toluene alkylation, toluene disproportionation and transalkylation. Among th...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B01J29/40C01B39/38C07C15/08C07C2/88
CPCY02P20/52
Inventor 尹双凤邓益强周伟芳吕浩民张莹莹陈浪
Owner HUNAN UNIV