Application of 553 industrial silicon powder: The direct chlorination method is the main method to produce trichlorosilane. Static processing. The bed synthesis furnace reacts to generate trichlorosilane, silicon tetrachloride, dichlorodihydrosilane, etc. as by-products. At the same time, this method also generates chlorosilane polymers, metal chlorides, etc. The main chemical reaction formula is as follows:
Main reaction si+2hcl→sih2cl2
Side reaction si+4hcl→sicl4+2h2
From the perspective of thermodynamics, the process of synthesizing trichlorosilane with 553 industrial silicon powder is an exothermic reaction, and its heat of reaction is 141.8kj mol-1. From a kinetic point of view, a higher reaction temperature can speed up the reaction rate, but, from a thermodynamic point of view, a higher reaction temperature will promote the conversion of trichlorosilane into by-product silicon tetrachloride, which is not conducive to the formation of trichlorosilane . The by-product silicon tetrachloride needs to be converted into trichlorosilane by cold hydrogenation or hot hydrogenation, which will increase the production cost of trichlorosilane. At present, the fluidized bed synthesis furnace for the production of trichlorosilane mainly adopts a jacket or a heat exchange tube for cooling, and water or heat transfer oil is passed into the jacket and heat exchange tube for cooling. The temperature adjustment speed is slow, and the jacket and heat exchange tube heat pipe is easy to wear and leak.
The preparation method of trichlorosilane comprises: taking 553 industrial silicon powder and hydrogen chloride as raw materials, making the silicon powder and hydrogen chloride undergo a synthesis reaction in a fluidized bed reactor to generate trichlorosilane, and introducing tetrahydrosilane during the synthesis reaction. The temperature is lowered by using the chloride liquid as the cooling medium, the reaction temperature is controlled, and the production of by-product silicon tetrachloride is reduced. The synthesis reaction temperature of 553 industrial silicon powder is controlled at 300-360°C. Before passing the silicon tetrachloride liquid into the fluidized bed reactor, it also includes: preheating the silicon tetrachloride liquid to 110-150°C, and the pressure of the silicon tetrachloride liquid is 1.0-1.5mpa. The preheating adopts the synthesis reaction tail gas output from the fluidized bed reactor as the heat source.