The main classification of catalyst
Source: | Author:admin | Published time: 2019-07-02 | 678 Views | Share:
here are many types of catalysts, which can be divided into liquid catalysts and solid catalysts according to the state; according to the phase state of the reaction system, they are divided into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts include acids, bases, soluble transition metal compounds and peroxide catalysts.
There are many types of catalysts, which can be divided into liquid catalysts and solid catalysts according to the state; according to the phase state of the reaction system, they are divided into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts include acids, bases, soluble transition metal compounds and peroxide catalysts. Heterogeneous 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, they are further divided into polymerization, polycondensation, and esterification , Acetalization, hydrogenation, dehydrogenation, oxidation, reduction, alkylation, isomerization and other catalysts; according to the size of the role is also divided into main catalyst and co-catalyst.

Homogeneous catalysis
The catalyst and the reactant are in the same phase, and the reaction without phase boundary exists is called homogeneous catalysis. The catalyst that can perform homogeneous catalysis is a homogeneous catalyst. Homogeneous catalysts include liquid acids, basic catalysts and Secothys solid acids and basic catalysts, soluble transition metal compounds (salts and complexes) and so on. Homogeneous catalysts act independently with molecules or ions, have uniform active centers, and have high activity and selectivity.

Heterogeneous catalysis
Heterogeneous catalysts, also known as heterogeneous catalysts, are used in reactions of different phases (Phase), that is, they are in different states from the reactants they catalyze. For example, in the production of margarine, through the use of solid nickel (catalyst), unsaturated vegetable oil and hydrogen can be converted into saturated fat. Solid nickel is a heterogeneous catalyst, and the reactants catalyzed by it are liquid (vegetable oil) and gaseous (hydrogen). A simple heterogeneous catalytic reaction involves the reactant (or zh-ch: substrate; zh-tw: substrate) adsorbed on the surface of the catalyst, the bond in the reactant is broken to cause the generation of new bonds, but Because the bond between the product and the catalyst is not strong, the product is separated from the reaction site and other processes. Many different structures where adsorption and reaction occur on the surface of many catalysts are known.

Bio catalysis
Enzymes are biocatalysts, which are organic substances (most proteins) produced by plants, animals and microorganisms (the vast majority of proteins. But a small amount of RNA also has a biocatalytic function), formerly called enzymes. The catalytic effect of the enzyme is also selective. For example, starch. Enzymes catalyze the hydrolysis of starch into dextrin and maltose, and proteases catalyze the hydrolysis of proteins into peptides. Living organisms use them to accelerate chemical reactions in the body. Without enzymes, many chemical reactions in the organism will proceed very slowly, making it difficult to sustain life. At a temperature of about 37°C (the temperature of the human body), the working state of the enzyme is optimal. If the temperature is higher than 50 ℃ or 60 ℃, the enzyme will be destroyed and can no longer function. Therefore, biological detergents that use enzymes to decompose stains on clothing are most effective when used at low temperatures. Enzymes are of great significance in physiology, medicine, agriculture, industry, etc. At present, the application of enzyme preparations is increasingly widespread.