Method for preparing L-zeolite by in-situ crystallization

The invention relates to a preparation method of L-zeolite. The preparation method comprises the following steps of: uniformly mixing solid silicon dioxide with silica sol, regulating the pH value of a system to 7-8, then forming, drying and calcining at the temperature of 300-900 DEG C for 1-6 hours to get a pre-formed body; adding solid sodium aluminate and potassium hydroxide into deionized water, and stirring till a solution is transparent to get a crystallized solution, wherein the molar ratio of KOH/AL2O3 is 1-20, and the molar ratio of H2O/Al2O3 is 10-120; adding the prepared pre-formed body into the crystallized solution, wherein the weight ratio of the crystallized solution to the pre-formed body is 2-10; and uniformly mixing, then performing hydrothermal crystallization for 6-24hours at the temperature of 100-180 DEG C, filtering, washing, and drying to get the in-situ crystallized L-zeolite. The crystallized L-zeolite has higher relative degree of crystallization and larger pore volume of mesopores, the pore diameter of the mesopores is 5-10nm, and an n-alkane aromatization catalyst prepared by taking the L-zeolite as a carrier has higher yield of arene.