Patent ID: 6852301

Claim:
Method for producing silane (SiH 4 ) by a) reacting metallurgical silicon with silicon tetrachloride (SiCl 4 ) and hydrogen (H 2 ) to form a crude gas stream containing trichlorosilane (SiHCl 3 ) and silicon tetrachloride (SiCl 4 ), b) removing impurities from the resulting crude gas stream by washing with condensed chlorosilanes to produce a purified crude gas stream containing trichlorosilane and silicon tetrachloride and a homogeneous liquid phase consisting essentially of SiCl 4 , this liquid phase then being removed from the circuit, c) condensing and subsequently separating the purified crude gas stream by distillation to form a partial stream consisting essentially of SiCl 4 and a partial stream consisting essentially of SiHCl 3 , d) returning the partial stream consisting essentially of SiCl 4 to the reaction of metallurgical silicon with SiCl 4 and H 2 , e) disproportionating the partial stream containing SiHCl 3 to form SiCl 4 and SiH 4 , and f) returning the SiCl 4 formed in the reaction to the reaction of metallurgical silicon with SiCl 4 and H 2 , characterized in that the crude gas stream containing trichlorosilane and silicon tetrachloride is liberated from solids as far as possible by gas filtration before being washed with the condensed chlorosilanes, the washing process with the condensed chlorosilanes is carried out at a pressure of 25 to 40 bar and at a temperature of at least 150° C. in a multi-stage distillation column and is carried out in such a way that 0.1 to 3 weight percent of the crude gas stream containing trichlorosilane and silicon tetrachloride is recovered in the form of a condensed liquid phase consisting essentially of SiCl 4 , such condensed liquid phase consisting essentially of SiCl 4 is removed from the SiCl 4 circuit and expanded to a pressure of 1 bar outside said SiCl 4 circuit and cooled to a temperature of 10 to 40° C., whereby dissolved impurities separate out, and such impurities separating out are removed by filtration.