Alkyl phosphorus dihalide preparing method

The invention relates to an alkyl phosphorus dihalide preparing method and belongs to the technical field of preparation of alkyl phosphorus halide. According to the method, hydrocarbon and phosphorus trihalide are taken as raw materials, alkali metal or alkaline-earth metal is taken as the initiator, and reaction is conducted at -30-170 DEG C. The initiator alkali metal or alkaline-earth metal reacts with the phosphorus trihalide to generate phosphorus dihalide free radicals, and free radical reaction is conducted between the phosphorus dihalide free radicals and the hydrocarbon to generate alkyl phosphorus dihalide, halogen hydride and a small amount of alkali halide or alkaline earth halide. The generated halogen hydride is low in solubility in a reaction system, and therefore the halogen hydride can be separated out in the gas form simply by conducting decompression on products. Compared with existing methods of preparing alkyl phosphorus dihalide with hydrocarbon and phosphorus trihalide as raw materials, the method has the advantage that due to the adoption of the initiator alkali metal or alkaline-earth metal, reaction temperature is reduced remarkably, so that the requirements of reaction for temperature and equipment are reduced, and then cost is reduced greatly.