Dynamic transitions in a reactive distillation column for the production of silicon precursors

The production of energy from solar cells is being considered as one key technology of the future. The remarkable growth in this market is primarily based upon solar cells made from polycrystalline silicon, which is typically produced via chemical vapor deposition of dichlorosilane or silane. Different technologies including reactive distillation have been considered for the production of polycrystalline silicon precursors. In the reactive distillation process, the trichlorosilane disproportionation reaction takes place producing monochlorosilane, dichlorosilane and silane. Steady state studies have reported that different silane products can be obtained by adjusting the operating condition of the reactive column. However, dynamic transitions from one product to another that can meet product quality specifications during operation still remains as a key challenge. This work investigates a feasible strategy for the dynamic transition and production of three silanes in a reactive distillation column. Results from this study show that there is a feasible dynamic transition from silane to monochlorosilane, then to dichlorosilane, and then back to monochlorosilane and silane. Temperature control and equipment sizing were identified as key design and operating variables to accomplish those transitions.