Process for hydrogenation of a silicon tetrahalide and silicon to trihalosilane

Abstract

A process of hydrogenation of a silicon tetrahalide and silicon to a trihalosilane comprising: providing a vessel with at least one inlet and one outlet with a plurality of silicon particles located in a bed inside the vessel and feeding a mixture of gases consisting primarily of a silicon tetrahalide and hydrogen. A calculational procedure is provided where the flow rate of the gases and the incoming size of the silicon particulates are chosen so that at least 90% of the volume of the bed is free of bubbles after allowance for decrease in particle size due to the reaction and attrition resulting in a higher yield of the trihalosilane.

1 . A process for hydrogenation of a silicon tetrahalide and silicon to trihalosilane comprising:
 providing a vessel with at least one inlet and at least one outlet and a bed comprising a plurality of silicon particles located inside the vessel, and   feeding a mixture of gases comprising a silicon tetrahalide and hydrogen into the vessel and through the bed, wherein the flow rate of the mixture of gases and the average size of the silicon particles are chosen so that at least 90% of the volume of the bed is free of bubbles.   
     
     
         2 . The process of  claim 1  where the velocity of the mixture of gases is equal to or less than a minimum bubbling velocity calculated based on the properties of the gases and silicon particles in the bed so as to maintain at least 90% of the volume of the bed free of bubbles. 
     
     
         3 . The process of  claim 1  where an average size of the silicon particles is determined by selecting the velocity of the gases through the vessel to provide at least 90% of the volume of the bed free of bubbles, said velocity being equal to or less than a calculated minimum bubbling velocity. 
     
     
         4 . The process of  claim 1  where additional silicon particles larger than an average size in the vessel are added intermittently to maintain the average size of particles in the vessel at or above a chosen size. 
     
     
         5 . The process of  claim 4  wherein standard population balance calculations, making allowance for reaction and attrition of the silicon particles in the vessel, are used to calculate a minimum size for the feed particles.