Method for synthesizing ZSM-5 molecular sieve through two-segment temperature change

Abstract

The invention relates to a method for synthesizing a ZSM-5 molecular sieve through a two-segment temperature-changing crystallizing process, which comprises the following steps of using a water-soluble liquid silicon source and a water-soluble liquid aluminum source as raw materials, wherein the molar ratios of the raw materials calculated by oxides are as follows: SiO2 / Al2O3=50-70, Na2O / SiO2=0.05-5, H2O / SiO2=50-70, and a template agent / SiO2=0.05-0.4; mixing the silicon source and the template agent according to formula amounts with deionized water which is added by accounting for 15-33.3wt% of the total usage amount of the required water under a dynamic state of overall-process stirring to prepare an A solution, mixing the aluminum source and sulfuric acid according to the formula amounts with the water which is added by accounting for 24-44.4wt% of the total usage amount of the required water to prepare a B solution, slowly adding the B solution into the A solution, adding the residual water, adding ZSM-5 crystal seeds into initial gel which is obtained by stirring the mixture for 0.5-2 hours, crystallizing for 10-20 hours at the temperature of 80-110 DEG C, and then crystallizing for 10-40 hours after increasing the temperature to 115-130 DEG C.

Description

technical field [0001] The invention relates to the synthesis of molecular sieves, in particular to a method for synthesizing ZSM-5 molecular sieves through a two-stage variable temperature crystallization process. Background technique [0002] Mobile company first reported the synthesis of ZSM-5 in 1972. In its disclosed synthesis method (US3,702,886), tetraalkylammonium hydroxide (alkyl C number 2~5) is used as template, and the reaction mixture prepared by silicon source, aluminum source, water, alkali and template The ZSM-5 product was obtained after crystallization under hydrothermal conditions. Since then, people have improved the synthesis method of ZSM-5 molecular sieve through a lot of research. For example, a number of patents have disclosed methods for the synthesis of ZSM-5 using different types of organic templates, including primary amines (US4,151,189), diamines (US4,139,600, US4,495,166), polyamines (US4,495,166), 4,404,175), low-carbon alcohols (US 4,175,...

AI Technical Summary

Problems solved by technology

In the usual molecular sieve synthesis method, due to the low viscosity of the starting material, the stirring process can be started smoothly, but in the multi-stage variable temperature process, the reaction mixture that is aged by standing still tends to form a high viscosity after the aging is completed. Therefore, when the stirring is started, it is difficult to stir due to the large resistance, or the stirring equipment is overloaded and damaged; the insufficient stirring caused by this will easily cause the temperature gradient of the synthesis system and the uneven distribution of the gel components, resulting in The obtained molecular sieve product has poor crystallinity and uneven particle size

In addition, the high temperature section of the above method often still requires a higher crystallization temperature and a longer crystallization time, which will also result in a decrease in equipment utilization and an increase in energy consumption.

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