Hydrothermal synthesis, hydrothermal conversion and ion exchange:
Hydrothermal synthesis is used to produce products with higher purity and to synthesize molecular sieves not found in nature. The silicon containing compound (water glass, silicon sol), aluminum compound (hydrated alumina, aluminum salts) and alkali (sodium hydroxide and potassium hydroxide) and water proportionately, heating time in autoclave, the precipitation of zeolite crystals. The synthesis process can be expressed as a lower order:
In the presence of excess alkali, the hydrothermal conversion of the solid aluminum silicate brine into a molecular sieve. The raw materials used are kaolin, bentonite, diatomite, etc., and synthetic silica aluminum gel particles can also be used. This method has low cost, but the purity of the product is less than that of hydrothermal synthesis.
Ion exchange usually transforms the Na zeolite into a molecular sieve containing the desired cations in aqueous solution. The general formula is as follows:
In the formula, Z- represents the anion backbone, and Me+ represents the cations to be exchanged, such as NH4 +, Ca2+, Mg2+, Zn2+, etc. the raw material is usually chloride, sulfate, and nitrate. In the solution of different cation exchange to molecular sieve on different degrees of difficulty, called sieve order, for example: the cationic molecules of 13X zeolite are Ag+, Cu2+, select H+, Ba2+, Au3+, Th4+, Sr2+, Hg2+, Cd2+, Zn2+, Ni2+, Ca2+, Co2+, NH4 K+, Au2+, Na+ +, Mg2+, and Li+. The following parameters: the common said exchange exchange degree, Na+ exchange accounted for the percentage of molecular sieve down in the original amount of Na+; exchange capacity, in exchange for every 100 moles of sieve in cationic milligram equivalent number; exchange efficiency, said the solution to the mass percentage of cation exchange on molecular sieve. In order to make the appropriate molecular sieve catalysts are needed to exchange the product with other components and deployment of these components may be other catalysts, catalyst and diluent or adhesive, prepared by molding material activated catalyst can be carried out.