A kind of preparation method and application of thin-layer nano-sheet all-silicon molecular sieve for preparing caprolactam

Abstract

The invention relates to a preparation method of a thin-layer nano flaky total-silicon molecular sieve for preparing caprolactam. The preparation method comprises the following steps: uniformly stirring a silicon source and an alkali source to obtain a mixture I; dissolving a template agent in a mixed solution of deionized water and ethanol to obtain a mixture II, and gradually dropwise adding the mixture I into the mixture II to be stirred to obtain a mixture III, and stirring the mixture III in a water bath to obtain initial gel; dynamically crystallizing the initial gel in a closed reaction kettle, and washing and drying the initial gel to obtain the thin-layer nano flaky total-silicon molecular sieve. The preparation method has the advantages of low cost, small energy consumption, high conversion rate, no pollution and capability of realizing industrial production.

Description

technical field [0001] The invention belongs to the preparation of molecular sieves, and in particular relates to a preparation method and application of a thin-layer nano-flaky all-silicon Silicalite-1 molecular sieve prepared from caprolactam. Background technique [0002] Caprolactam is an important intermediate used in the synthesis of nylon-6 fibers and resins, and is widely used in artificial leather, medicine, and chemical additives. In 2010, the domestic self-sufficiency rate of caprolactam was 43.9%, and the amount of imported caprolactam in my country increased by an average of 12% per year. The domestic production capacity is insufficient, and a large number of imports are relied on. [0003] At present, caprolactam is mainly synthesized by Beckmann rearrangement reaction of cyclohexanone oxime. There are two main processes to realize this process: liquid-phase Beckmann rearrangement and gas-phase Beckmann rearrangement. Since the liquid-phase Beckmann rearrangem...

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Problems solved by technology

[0007] CN102658191B discloses a supported solid acid catalyst with heteropolyacid as the active component and mesoporous molecular sieve as the carrier for the Beckmann rearrangement reaction of cyclohexanone oxime, but its conversion rate is only 82.5%, and the selectivity is only 87.1% %

CN103288735A has reported a mixed catalytic system with acidic ionic liquid and ZSM-5, the reaction conditions are relatively mild, but the catalyst deactivation is very fast

CN102895996A discloses a homogeneous catalytic system composed of organic acid and organic solvent, but the product is not easy to separate

[0011] In ACSCatal.2011,1:337, Ryoo et al reported the use of asymmetric double-headed ammonium surfactant [C 16 h 33 -N + (CH 3 ) 2 -C 6 h 12 -N + (CH 3 ) 2 -C 6 h 13 ](OH) - 2 A single-layer sheet-like hierarchical porous all-silicon molecular sieve with a b-axis thickness of 2nm was synthesized for gas-phase Beckmann rearrangement reaction, WHSV=3h -1 , the reaction temperature is 350°C, the initial conversion rate is 85%, and it drops to 65% after 100 hours. The activity and stability of the catalyst are much higher than that of large particle all-silicon molecular sieves, but compared with the existing industrial application level, the conversion rate is low In addition, adopting the higher toluene and acetonitrile of toxicity and cost as solvent synthesis template is unfavorable for industrialized large-scale production: the harm of toluene to human health includes irritation to skin and mucous membranes, and anesthesia to central nervous system

Acetonitrile is extremely volatile and is a moderately toxic substance that is extremely harmful to the human body, and the discharge of waste liquid can cause serious environmental pollution; using anion exchange resin to exchange bromine-type template agent to obtain hydrogen-oxygen-type template agent, the process is complicated and the cost is high

Currently disclosed patents and documents do not use the very low toxicity of green chemicals dimethyl carbonate, diethyl carbonate and ethanol, propanol as a solvent to synthesize bromine-type, chlorine-type asymmetric double-headed ammonium surfactants, and directly use Synthesis of thin-layer nanosheet silicalite-1 molecular sieves with bromine-type and chlorine-type templates

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