Tangled effects of CuCl precursor and Zn, Sn promoters used for the methylchlorosilanes direct synthesis

Abstract

In this work, the effects of CuCl catalyst precursor and Zn, Sn addition on formation of Cu-based metallic phases and on either catalytic performance and coke formation was investigated during the early stage of methylchlorosilanes synthesis. The Cu₃Si active phase is formed during pretreatment at 310 °C as well as Cu₁₅Si₄ and Cu. Addition of Zn and Cu_0.9Sn_0.1 was shown to accelerate their formations probably through the wetting of Si particles by mixed chloride. Furthermore, residual chloride particles were observed both for promoted and unpromoted masses. It was confirmed that Zn and Sn promote the dimethyldichlorosilane formation rate but also clearly showed they favour CH₃Cl cracking. Coke early detected as disordered graphite by Raman spectroscopy, was preferentially formed on residual chloride particles. CH₃Cl cracking could be favoured by the presence of Zn and Sn within such particles. Therefore, the tangled positive and negative effects of Zn and Sn ‘promoters’ as well as CuCl precursor highlight the need to optimize their respective amounts in an industrial process.