Formation of dimethyldichlorosilane (M2) in the Müller-Rochow process at the molecular level

In the Müller-Rochow process or direct process, CH 3 Cl reacts with silicon, forming (CH 3 ) 2 SiCl 2 (M2) as the dominant species with copper as catalyst. This complex and highly heterogeneous process takes place in a gas-solid stirred fluidized bed reactor. In this study, the formation of (CH 3 ) 2 SiCl 2 on a Cu rich Cu-Si model has been investigated using density functional theory (DFT). The results show that the overall reaction is exoergic. Upon dissociation of CH 3 Cl, the reaction proceeds first by interaction of CH 3 with Si followed by subsequent addition of Cl. The largest activation barrier is found for the second Si-Cl bond formation in which a weakly adsorbed (CH 3 ) 2 SiCl 2 is formed. Compared to dehydrogenation of adsorbed CH 3 formed upon dissociation of CH 3 Cl, formation of M2 is energetically favoured on a Si modified Cu(111) model. • A reaction path for ( CH 3 ) 2 SiCl 2 formation in the Müller-Rochow process is proposed. • The Müller-Rochow reaction can proceed on a Cu-rich mixed Cu-Si phase. • Coke precursor formation is more advantageous with Si in the Cu surface. • The path to ( CH 3 ) 2 SiCl 2 is advantageous compared to formation of coke precursors.