Preparation method of catalyst: ion exchange method

The ion exchange method is a method that uses ion exchange reaction as the main preparation process to prepare the catalyst. In this method, the active component is loaded onto the carrier by ion exchange, and then the catalyst is prepared by appropriate treatment such as washing, drying, roasting, etc.

Since the early 1960s, zeolite molecular sieves have been used more and more in catalytic reactions as inorganic ion exchangers. The rare earth Y-type catalytic cracking catalyst, diesel hydrogenic depolymerization catalyst, HZSM-5 catalyst for alkyl synthesis of styrene by ethylene and benzene are all widely used in petrochemical industry.

For example, aluminum silicate (SA) has a hydroxyl group on its surface and is very acidic. These ions (H+) cannot be exchanged directly with transition metal ions or metal complex ions, and ion exchange can occur if the surface protons are replaced by NH4+ ions in the future. The metal particles produced by the catalyst after reduction are very fine, the activity and selectivity of the catalyst are very high.

Sodium zeolite and sodium high ion exchange resin can also be used to produce the desired catalyst by ion exchange reaction. For example, the exchange reaction of hydrogen ions with sodium ion exchange resin can be used as a catalyst for some acid and base reactions.The corresponding molecular sieve catalyst can be prepared by the exchange reaction of NH4+, alkali earth metal ion or precious metal ion with molecular sieve.

Ion exchange reactions occur on fixed and limited exchange groups on the surface of the exchanger, and are stoichiometric, reversible (some exchange reactions are irreversible), and mild processes. The catalyst prepared by this method has high dispersion, large surface area and high activity, and is especially suitable for the preparation of precious metal catalysts with low content and high utilization rate.