Preparation method for nanometer mordenite molecular sieve with multi-stage holes

Abstract

The invention discloses a preparation method for a nanometer mordenite molecular sieve with multi-stage holes. In the method, a novel cationic surfactant is used as a template agent for directly synthesizing the nanometer mordenite molecular sieve with the multi-stage holes through hydro-thermal synthesis; the raw materials for preparing the nanometer mordenite molecular sieve comprise a silicon source, the template agent, an alkali source, an aluminium source and water, and the molar ratio of the silicon source to the template agent to the alkali source to the aluminium source to the water is 1 : (0.005-1.0) : (0.3-0.7) : (0.01-0.1) : (30-200). Compared with the prior art, the preparation method has the most remarkable advantages that the novel cationic surfactant is used as a single structure-directing agent for synthesizing the mordenite molecular sieve with both the multi-stage holes and the nanometer crystalline grain size in one step, the synthetic method is simple, the repeatability is high, and the prepared mordenite molecular sieve has the advantages of high crystallinity, high purity and the like.

Description

technical field [0001] The invention relates to the synthesis of zeolite molecular sieves, in particular to a synthesis method of multi-level porous nanometer mordenite molecular sieves. Specifically, nanometer mordenite molecular sieves with hierarchical pores are directly prepared by using a new type of cationic surfactant as a template through a hydrothermal synthesis method. Background technique [0002] The hydrogen-form mordenite exhibits excellent catalytic reactions in toluene disproportionation, alkylation, isomerization of C8 aromatics and selective disproportionation of toluene due to its one-dimensional twelve-membered ring straight cylindrical channel (pore size 0.695 nm × 0.581 nm) performance. The current research focus on mordenite molecular sieves is mainly to synthesize nano-sized mordenites with hierarchical pores (or micro-mesoporous composites). Lower ratio of silicon to aluminum (SiO 2 / Al 2 o 3 Molar ratio between 5 and 10) significantly reduces t...

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Problems solved by technology

The specific synthesis method is to directly treat the mordenite synthesized by the direct method with concentrated nitric acid or concentrated hydrochloric acid under reflux, or to remove the aluminum in the molecular sieve framework by treating the mordenite with steam. This synthesis strategy can obtain micropore-mesopore-large However, the preparation conditions of this synthesis strategy are harsh and complicated, and the crystallinity of the obtained mordenite molecular sieve is greatly reduced, which greatly increases the synthesis cost of mordenite and causes a lot of pollution to the environment.

[0005] Comparing the advantages and disadvantages of the two methods, recently Tago et al. used the non-ionic surfactant Polyoxyethylene-(15)-oleylether (O-15) as a particle growth inhibitor in the organic solvent of cyclohexane to prepare nano-sized small grains Mordenite molecular sieves, but a large amount of organic templates and organic solvents are used in this method, which greatly increases the synthesis cost of zeolite molecular sieves and easily causes a lot of pollution to the environment

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