Role of Copper in the Formation of Carbon during Direct Synthesis of Methylchlorosilanes

Abstract

Coke formation by cracking of chloromethane remains a challenge for profitability and predictable operation of the MCS process (also known as Müller-Rochow or Direct process). In this process methylchlorosilanes are produced by reacting methyl chloride (CH3Cl) with silicon. Identifying situations that lead to cracking and understanding the catalysis behind the cracking is needed to understand and ultimately find countermeasures to limit these unwanted reactions. Results and observations have shown that de-activated copper catalyst can be an initiation point for cracking of the CH3 group. Atomistic modelling by density functional theory (DFT) has been performed to study and understand the initiation of the cracking, intermediates of cracking and carbonaceous products. This has been combined with lab scale experimentation and a wide range of characterization techniques to investigate formation of both advantageous and detrimental copper species as well as formed carbon compounds on the contact mass surface as a function of contact mass composition and progress of the reaction. Both macro scale effects and detailed mechanisms on copper rich surfaces affecting the cracking of chloromethane are discussed with the aim to give input on how to actively mitigate cracking in the MCS process.

Keywords: Silanes, MCS, cracking, catalysis