Hydrosilylation reaction refers to the addition reaction between organosilicon compounds containing silicon hydrogen bonds and compounds containing unsaturated bonds under certain conditions. It is the main form of forming silicon carbon bonds and one of the most basic and important reaction types in organosilicon chemistry. Unsaturated bonds can be carbon carbon double bonds, carbon carbon triple bonds, carbon oxygen double bonds and carbon nitrogen double bonds. Among them, the addition reaction of silicon hydrogen bond and carbon carbon double bond is the most common silicon hydrogen addition reaction in the silicone industry, and is the core reaction of many addition molding silicone products.

For hydrosilylation reaction, except hydrosilanes and unsaturated compounds, catalyst is an indispensable component, which plays a role in accelerating reaction speed, shortening reaction time and reducing reaction temperature. The catalysts for hydrosilylation reaction are mainly the compounds and complexes of Ⅷ B group transition metal elements such as platinum, palladium, nickel and rhodium in the periodic table, among which platinum catalyst has the highest catalytic activity and is most widely used.

Platinum catalysts for hydrosilylation are mainly divided into homogeneous catalysts and heterogeneous catalysts. Among them, homogeneous catalyst and reactant are in the same phase, and there is no phase interface. In hydrosilylation reaction, homogeneous catalyst generally refers to liquid catalyst.

There are three main types of homogeneous platinum catalysts: the first is to convert chloroplatinic acid (H2PtCl6 ▪ 6H2O) is dissolved in ethanol, isopropanol, tetrahydrofuran and other organic solvents, so that they can interact to form a complex, which is called "Speier catalyst". This catalyst is easy to make and use; The second type of platinum catalyst is the complex of platinum and vinyl double heads, which is called Karstedt's catalyst. It has high reaction activity, can be stored stably, and has good compatibility with various types of polysiloxanes. It is the most widely used catalyst in addition silicone release agents; The third type of platinum catalyst is that chloroplatinic acid forms complexes with ketones, cyclopentadienes, esters, alcohols, crown ethers, heteroatom containing crown ethers and polysiloxanes, in addition to forming complexes with other unsaturated compounds.

Homogeneous platinum catalyst has high activity and reaction selectivity. However, because it is in the same phase with the reactants, it is difficult to separate and reuse after the reaction is completed, so the cost is high and heavy metal ion pollution may occur. Therefore, the researchers prepared heterogeneous catalysts by immobilizing homogeneous catalysts. The so-called immobilization of homogeneous catalyst is to combine homogeneous catalyst with solid carrier by physical or chemical methods to form a special catalyst. Heterogeneous platinum catalyst and reactant belong to different phases. The common form is that solid catalyst catalyzes hydrosilylation of liquid mixed reactants.

Heterogeneous catalysts for hydrosilylation are mainly divided into two types, traditional heterogeneous platinum catalysts and polymer metal complex catalysts. Among them, traditional heterogeneous catalysts are formed by adsorbing transition metals on inorganic particles such as carbon black and aluminum oxide. These catalysts have high stability and can be recycled, but their catalytic activity and selectivity are low, and the reaction process requires high temperature and pressure. Polymer metal complex catalyst consists of polymer carrier, coordination group bonded on the carrier and transition metal. In general, heterogeneous catalyst has the advantages of high stability and recyclability, but its application is limited due to its low activity and selectivity, complex preparation process and reduced catalytic activity when it is used again.

There are many substances that can "poison" the platinum catalyst, causing its catalytic activity to decrease or even lose its activity. For example, organic compounds containing nitrogen, phosphorus, sulfur and other elements and ionic compounds containing tin, lead, mercury, bismuth, arsenic and other heavy metals. Therefore, special attention should be paid during the use of platinum catalyst to avoid platinum catalyst contacting with these substances that can make it toxic. There are many types and forms of platinum catalysts. Therefore, in the application process, appropriate platinum catalysts should be selected according to the characteristics of the reaction system to achieve the best catalytic effect.

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