Toward Understanding the Formation of Coke during the MCS Reaction: A Theoretical Approach

Abstract

In the Muller−Rochow process, where CH 3 Cl reacts with silicon to form methylchlorosilanes, copper is used as a catalyst. To provide insight into mechanisms leading to coke formation in the process, the interactions and decomposition of CH 3 Cl with four different surface orientations of copper were investigated by means of density functional theory. CH 3 Cl adsorbs weakly on the different surfaces, and decomposition occurs preferentially by splitting the C−Cl bond, leaving CH 3 and Cl on the surface. Dehydrogenation of CH 3 can be considered as a key step toward coke formation as the presence of CH 2 can lead to C−C bond coupling or further dehydrogenation. All surfaces investigated, Cu(100), Cu(111), Cu(410) and Cu( 221), show that CH 2 formation is thermodynamically favorable relative to gaseous CH 3 Cl, and the path with lowest energy barriers is found for the Cu(410) surface.

Effect of Copper Catalyst Content and Zinc Promoter on Carbon Formation in the Direct Synthesis of Methylchlorosilanes

“…Detailed mechanistic insight remains difficult, however, and thus, more theoretical approaches and use of model systems may prove highly useful. 56 Our results confirm the heterogeneity of reacted contact masses, displaying unreacted Si with localized etching and differences in the CuCl, metallic Cu, and copper silicide phases as well as carbon of varying order, H-content, and reactivity. The somewhat similar reactivity and Si consumption between the std-Cu experiments after 16 h and 5 × Cu after 5 h suggest that higher Cu loadings may be used as representative, accelerated protocols for enhancing effects of a progressed reaction.…”

“…In order to extract good characterization data, storage under inert conditions must be ensured. Detailed mechanistic insight remains difficult, however, and thus, more theoretical approaches and use of model systems may prove highly useful …”