Molecular sieve and its preparation method

A method for preparing a molecular sieve, comprising the following steps:

• (1) utilizing N,N,N-trimethyl-1-adamantyl ammonium hydroxide, sodium hydroxide, silica sol, sodium metaaluminate and water to obtain a first mixture, and performing a first hydrothermal synthesis reaction to obtain a first reaction product;
• (2) mixing the first reaction product obtained in step (1) with ammonium nitrate and copper-glutamate chelate to obtain a second mixture, and performing a second hydrothermal synthesis reaction to obtain a second reaction product;
• (3) mixing the second reaction product obtained in step (2) with rare earth oxide to obtain a third mixture, and performing a third hydrothermal synthesis reaction to obtain a third reaction product;
• (4) performing solid-liquid separation of the third reaction product obtained in step (3) to obtain solid substance in the third reaction product, and calcining the obtained solid substance in the third reaction product to obtain the molecular sieve;
• wherein a molar ratio of silica sol to sodium metaaluminate is 1-20:1, a molar ratio of sodium hydroxide to sodium metaaluminate is 5.1-15.3:1, a molar ratio of N,N,N-trimethyl-1-adamantyl ammonium hydroxide to sodium metaaluminate is 1.0-10:1, and a molar ratio of water to sodium metaaluminate is 550-1000:1;
• wherein a molar ratio of copper-glutamate chelate to sodium metaaluminate is 0.6-8:1, a molar ratio of ammonium nitrate to sodium metaaluminate is 2.1-8:1;
• a mass of rare earth oxide is 50 ppm-2 wt % of the solid substance in the reaction product obtained in step (1);
• wherein silica sol is calculated by silicon dioxide, sodium metaaluminate is calculated by aluminum oxide, sodium hydroxide is calculated by sodium oxides, copper-glutamate chelate is calculated by copper oxides, ammonium nitrate is calculated by NH4+;
• wherein a temperature of the first hydrothermal synthesis reaction is 80-180° C., and the reaction time of the first hydrothermal synthesis reaction is 1-5 days;
• a temperature of the second hydrothermal synthesis reaction is 40-100° C., and reaction time of the second hydrothermal synthesis reaction is 4-48 hours;
• a temperature of the third hydrothermal synthesis reaction is 40-80° C., and reaction time of the third hydrothermal synthesis reaction is 4-48 hours;
• the solid substance is calcined by microwave roasting at a calcination temperature of 500-800° C. for 3-10 hours.