Low-cost solar array project. Task I. Silicon material: investigation of the hydrogenation of SiCl/sub 4/. Third quarterly report

Abstract

A laboratory stainless steel reactor has been constructed and installed to study the hydrogenation of SiCl/sub 4/, 3 SiCl/sub 4/ + 2 H/sub 2/ + Si reversible arrow 4 SiHCl/sub 3/. The reactor is designed to operate at pressure up to 500 psig which is the proposed operating pressure range of the Union Carbide EPSDU; silane-to-silicon process. Series of experiments were carried out to measure the reaction kinetics. The effect of reactor temperature on the rate of the hydrogenation of SiCl/sub 4/ to SiHCl/sub 3/ was measured at 400, 450, 500 and 550/sup 0/C. As expected, the reaction rate increases rapidly with increasing reactor temperature. The reaction rate and SiHCl/sub 3/ conversion were studied as functions of hydrogen and SiCl/sub 4/ concentrations at H/sub 2//SiCl/sub 4/ ratios of 1.0 and 2.8. Higher H/sub 2/SiCl/sub 4/ ratio produces a higher SiHCl/sub 3/ conversion per pass while the reaction rate remains approximately the same. The effect of reactor pressure on the rate of the hydrogenation reaction is most interesting. The rate of approaching equilibrium at higher reactor pressure (500 psig) is somewhat slower than those at lower reactor pressure (300 psig). In general, the 500 psig experimental data confirm previous estimated results which were obtained by extrapolating from lower reactor pressure data. Results of these experimental data show that the highest product SiHCl/sub 3/ output for a given reactor size is achievable by operating the hydrogenation process at maximum reactor temperature and pressure.