Name：Panjin dew-point catalyst technologise co.,ltd.
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Basic types of catalysts
Chemical catalysts are divided into homogeneous catalysis and heterogeneous catalysis, and the catalysts should also have their corresponding types. Although this distinction does not reflect the nature of the role of the catalyst and its internal connection, it is very practical and convenient.
The catalysts of homogeneous catalytic system mainly include two types of acid-base catalysts including Lewis acids and bases and soluble transition metal compound (salts and complexes) catalysts. In addition, there are a few non-metal molecular catalysts, such as I2 and NO. Homogeneous catalysts act independently at the molecular or ion level. The properties of the active center are relatively uniform, and it is easier to temporarily combine with the reactants. It is detected and tracked by optical disc, pop and isotope tracer methods, and the catalytic reaction kinetics equation is general It is also not too complicated, so quite a lot of homogeneous catalytic reaction kinetics and mechanisms have been studied more clearly.
The catalysts of heterogeneous catalytic systems are mostly solid. Industrially important solid catalysts can be roughly divided into conductors, semiconductors and insulators according to their main catalytic components.
Segmentation can also be divided into:
1. Transition metal catalyst;
2. Semiconductor type oxygen (sulfur) compound catalyst;
3. Transition metal complex catalyst;
4. Solid acid-base catalyst.
Between these types, there are not only their essential differences, but also some interoperability.
Catalysis can be divided into the following types: ① Homogeneous catalysis. The catalysis in which the catalyst and the reactants are in the same phase, such as homogeneous acid-base catalysis, homogeneous complexation catalysis, etc. Homogeneous catalysis is mostly carried out in the liquid phase. Homogeneous catalysts have relatively uniform active centers, higher selectivity, and fewer side reactions, but the catalysts are difficult to separate, recover and regenerate.
② Heterogeneous catalysis. Catalysis that occurs at the interface of the two phases. Usually the catalyst is a porous solid, and the reactant is a liquid or gas. In the heterogeneous catalytic reaction, the solid catalyst chemically adsorbs the reactant molecules, which activates the reactant molecules, reduces the activation energy of the reaction, and accelerates the reaction rate. The surface of the solid catalyst is not uniform, and only some of the spots chemically adsorb the reactant molecules, which are called active centers. Most of the catalysis in industrial production is heterogeneous catalysis.
③Biocatalysis. The catalytic reaction in the organism under the action of enzymes. Enzyme catalysis has the characteristics of high selectivity, high catalytic activity, and mild reaction conditions, but it is greatly affected by factors such as temperature, pH in the solution, and ionic strength.
④Autocatalysis. The autocatalysis of reaction products. In some reactions, the products or intermediates of certain reactions have a catalytic function, which greatly accelerates the reaction rate after a period of induction. Autocatalysis is one of the necessary conditions for chemical oscillation.