There are various types of catalysts, which can be divided into liquid catalysts and solid catalysts according to their states; According to the phase state of the reaction system, it can be divided into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts include acid, base, soluble transition metal compounds, and peroxide catalysts. Multiphase catalysts include solid acid catalysts, organic base catalysts, metal catalysts, metal oxide catalysts, complex catalysts, rare earth catalysts, molecular sieve catalysts, biocatalysts, nanocatalysts, etc; According to the type of reaction, catalysts can be divided into polymerization, condensation, esterification, acetalization, hydrogenation, dehydrogenation, oxidation, reduction, alkylation, isomerization, etc; According to the size of their effects, they can be divided into main catalysts and co catalysts.
Homogeneous catalysis
A reaction in which a catalyst and reactants are in the same phase without a phase boundary is called homogeneous catalysis, and a catalyst that can perform homogeneous catalysis is called a homogeneous catalyst. Homogeneous catalysts include liquid acid, base catalysts, solid acid and base catalysts, soluble transition metal compounds (salts and complexes), etc. Homogeneous catalysts act independently of molecules or ions, with uniform active centers and high activity and selectivity.
Multiphase catalysis
Heterogeneous catalysts, also known as heterogeneous catalysts, are used in reactions of different phases, where the reactants they catalyze are in different states. For example, in the production of margarine, unsaturated vegetable oil and hydrogen can be converted into saturated fat through solid nickel (catalyst). Solid nickel is a heterogeneous catalyst, and the reactants catalyzed by it are liquid (vegetable oil) and gaseous (hydrogen gas). A simple heterogeneous catalytic reaction involves the adsorption of reactants (or substrates) on the surface of a catalyst, the breaking of bonds within the reactants leading to the formation of new bonds, and the detachment of the product from the reaction site due to weak bonds between the product and the catalyst. It is now known that many catalysts exhibit different structures for adsorption and reaction on their surfaces.
Biocatalysis
Enzymes are biocatalysts, organic compounds with catalytic ability produced by plants, animals, and microorganisms (the vast majority of proteins, but a small amount of RNA also has biocatalytic function), formerly known as enzymes. The catalytic action of enzymes also has selectivity. For example, starch. Enzymes catalyze the hydrolysis of starch into dextrin and maltose, while proteases catalyze the hydrolysis of proteins into peptides. Living organisms use them to accelerate chemical reactions within their bodies. If there were no enzymes, many chemical reactions in organisms would proceed very slowly, making it difficult to sustain life. At a temperature of approximately 37 ℃ (the temperature of the human body), the working state of enzymes is optimal. If the temperature is above 50 ℃ or 60 ℃, the enzyme will be destroyed and can no longer function. Therefore, biological detergents that use enzymes to break down stains on clothing are most effective when used at low temperatures. Enzymes have significant implications in physiology, medicine, agriculture, industry, and other fields. Currently, the application of enzyme preparations is becoming increasingly widespread. (For example, enzyme preparations can be used as catalysts in industry, and some enzymes are also valuable drugs.)
