Preparation method of high-silicon/aluminum ratio step hole Beta molecular sieve

Abstract

The invention provides a preparation method of a high-silicon / aluminum ratio step hole Beta molecular sieve and more detailedly explains a synthesis mechanism, thereby having certain guiding significance in the subsequent synthesis of the molecular sieve by using the method. The preparation method can successfully synthesize the high-crystallinity Beta molecular sieve with a silicon / aluminum ratioof 200-2000 within 24 hours and has the advantages of being controllable in silicon / aluminum ratio, high in crystallinity, rich in step hole structure and the like. Compared with a traditional hydrothermal method, the preparation method provided by the invention has the beneficial effects that crystallization liquid required is less, so that the problem of discharge of a large amount of crystallized waste liquid is solved; the consumption of a template agent is less, so that the synthesis cost is low; the raw material utilization rate is high, and about 100 percent of product yield can be reached; the synthesis time is short, and the steps are simple, the energy consumption can be effectively reduced, and the large-scale industrial production is facilitated.

Description

technical field [0001] The present invention relates to a preparation method of a molecular sieve with a *BEA structure, specifically a Beta with a high silicon-aluminum ratio, high crystallinity, and a rich stepped pore structure that is rapidly synthesized under a low amount of templating agent by steam assistance. Preparation method of molecular sieve. Background technique [0002] Beta molecular sieve is the only molecular sieve with twelve-membered ring intersecting channel system, which has unique channel structure, high acidity and good hydrothermal stability. In the 1960s, a series of molecular sieves with a low silicon-to-aluminum ratio were developed by the US Mobile Company, and molecular sieve materials have become the most important catalytic core or catalyst carrier in the petrochemical field. Patent CN106430230 B once pointed out that the thermal stability and hydrothermal stability of low-silicon molecular sieves are relatively low, and the reaction process ...

AI Technical Summary

Problems solved by technology

This patent provides a new method of synthesizing Beta molecular sieves by using steam, which effectively avoids the disadvantages of traditional hydrothermal synthesis, but the method uses a large amount of organic template (TEAOH / SiO 2 The molar ratio is up to 0.65), and the hard template agent is introduced for the second time to expand the pores, which not only increases the production cost, but also brings huge environmental problems to the calcination of the soft and hard template agents in the later stage, and under the condition of using a large amount of organic template agents, The silicon-aluminum ratio of the synthesized Beta molecular sieve is still not high, and the silicon-aluminum ratio can only be adjusted within 10~50

[0009] In Zhang Junliang’s latest study on the synthesis of Beta molecular sieves by steam-assisted method (Chemical Engineering Journal 291 (2016) 82-93), he reported a synthesis method of step-pore Beta molecular sieves with coexistence of micro-step pores, and the silicon-aluminum ratio of the samples It can be tuned within the range of 30~100, but with the increase of silicon-aluminum ratio, the relative crystallinity decreases

[0010] The above-mentioned methods for synthesizing Beta molecular sieves all have the following defects: First, most of the techniques for synthesizing Beta molecular sieves today are limited to hydrothermal synthesis, and there are unavoidable defects in hydrothermal synthesis: (1) The product yield is low

However, judging from the current research progress of Beta molecular sieve synthesis by dry glue method, the silicon-aluminum ratio in Beta molecular sieve products is limited in the range of Si / Al<100, and the structural stability and hydrothermal stability of the sample are also poor. Molecular sieves with a high silicon-aluminum ratio must require a certain amount of template. Therefore, it has always been a challenge to synthesize a stepped-pore Beta molecular sieve with an ultra-high silicon-aluminum ratio at a low dosage of template.

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