Introduction To Heterogeneous Catalysis

Heterogeneous catalysis refers to the catalytic reaction that occurs on the interface of two phases (solid-liquid, solid-gas, liquid-gas). Most of the catalytic reactions used in industry belong to heterogeneous catalysis. Heterogeneous catalysis occurs on the surface of the catalyst. Therefore, the heterogeneous catalytic reaction includes the diffusion of reactant molecules in the pores of the catalyst, the adsorption on the surface, the reaction on the surface, the desorption of product molecules, and the diffusion in the pores. For catalysts, the adsorption center is often the catalytic active center. Adsorption centers and adsorbate molecules together constitute surface adsorption complexes, that is, surface active intermediate species. Adsorption of reactant species on the catalyst surface alters the pathway of the reaction and thus the activation energy required for the reaction. There is no heterogeneous catalysis without adsorption, and the reaction mechanism of heterogeneous catalysis is inseparable from the mechanism of adsorption and diffusion.