Efficient Adsorption Removal of Trace PCl3 Impurities from an Organic System over Mo-Modified Al2O3 Material

Polysilicon is widely used in the photovoltaic and semiconductor industries. The presence of trace phosphorus impurities in the trichlorosilane feedstock can severely degrade the quality of polysilicon products. To address the urgent need for complete phosphorus removal of trichlorosilane, in this work, on the basis of the reducing ability of PCl3 and the stronger Lewis base properties of its oxidation product, POCl3, we developed an efficient material, xMo/Al2O3y, using Al2O3 as the support and Mo species as active substances through a simple and straightforward method. Under the optimized preparation conditions of 7.8% Mo loading and a calcination temperature of 450 °C, the adsorbent exhibited optimal performance in an organic system simulating a trichlorosilane system with a P adsorption capacity of 53.52 mg g−1, achieving near-complete elimination of phosphorus impurities. A series of characterization analyses suggested the following primary removal mechanism: initial oxidation of PCl3 to POCl3 by Mo6+ species, followed by its complexation with Mo sites via Lewis acid-base interactions. Furthermore, surface morphology damage during the removal process and the accumulation of reaction products on the spent adsorbent are the main factors contributing to its deactivation. This work presents an effective strategy for the deep dephosphorization of trichlorosilane.