Method for preparing silicon-aluminum mixed oxide by taking waste silicon-aluminum molecular sieve

The invention relates to a method for preparing a silicon-aluminum mixed oxide by taking a waste silicon-aluminum molecular sieve as a raw material. The method mainly comprises the following steps of uniformly mixing the waste silicon-aluminum molecular sieve and an acid compound solution for reaction for 0.5-10h at 60-110 DEG C, filtering to form an acid reaction solution and undissolved substance, mixing the undissolved substance and a basic compound solution after washing and drying, performing hydrothermal treatment for 2-10h at 120-200 DEG C to form a basic reaction solution, neutralizing the acid reaction solution and the basic reaction solution into gel, treating slurry for 2-6h at 60-90 DEG C after the reaction finishes, and carrying out solid-liquid separation, washing and drying to form silicon-aluminum mixed oxide powder. Compared with the prior art, the method substitutes the waste silicon-aluminum molecular sieve for expensive industrial raw materials to prepare the silicon-aluminum mixed oxide, enlarges a raw material source, lowers preparation cost of the silicon-aluminum mixed oxide and treatment cost of the waste molecular sieve, prevents environmental pollution caused by the waste molecular sieve, allows the waste to be recycled and has better economic and social benefits.