Heterogeneous Catalytic Reaction Process

In heterogeneous catalysis there is a single catalyst phase, which complicates the process of heterogeneous catalysis reactions. Under the reaction conditions, most of the reactants and products are gaseous substances, while most of the catalysts are porous solids, and the internal surface is extremely large. Generally, the internal surface area of each gram of catalyst is as much as several hundred square meters, and the external area of the particles is the same as that of the catalyst. Insignificant in comparison. Chemical reactions mainly take place on the inner surface of the catalyst. The reacting components therefore have to diffuse not only to the outer surface, but also to the interior of the particle and then react on the inner surface of the particle. The product then diffuses in the opposite direction from the inner surface of the particle to the bulk of the fluid. Therefore, heterogeneous catalytic reactions go through the following steps:
① The reactant diffuses to the surface of the catalyst;
② The reactants are adsorbed on the inner surface of the catalyst;
③ The adsorbed reactants migrate, chemically rearrange and react on the surface of the catalyst;
④ The product is desorbed from the surface of the catalyst;
⑤ The product diffuses from the catalyst surface to the flow body.