CH₃Cl/Cu(410): Interaction and Adsorption Geometry

Abstract

The Rochow process is the most common technology used to prepare organosilicon compounds on an industrial scale, and yet the mechanism is still not well understood. It involves the reaction of methyl chloride (CH3Cl) with silicon, catalyzed by copper. To understand the elementary steps of the reaction involved, we studied the molecular adsorption of CH3Cl/Cu­(410) at 100 K and its complete desorption at higher temperatures, 100 K < T D < 200 K. Temperature-programmed desorption (TPD) spectra show two CH3Cl desorption peaks. We attribute the low temperature TPD peak (T D ≈ 120 K) to CH3Cl desorbing from both step-edges and terraces and the high temperature TPD peak (T D ≈ 160 K) to CH3Cl desorbing from the step-edges. Infrared reflection–absorption spectra (IRAS) indicate that at low CH3Cl coverage (Θ = 0.06 ML), CH3Cl adsorbs with its molecular axis (Cl–C bond) aligned either parallel or perpendicular to [001]. At high CH3Cl coverage (Θ ≥ 0.09 ML), CH3Cl adsorbs with its molecular axis aligned perpendicular to [001].

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

“…The absolute differences between literature and the herein reported values are within what is considered quantum chemical accuracy and can be ascribed to different applied functionals and computational settings. Makino et al showed experimentally that at low coverage physisorption is possible with the C–Cl bond either perpendicular or parallel to the [001] plane of the Cu(410) surface and that at higher coverage the perpendicular adsorption geometry was dominant. In the present study the adsorption energies without ZPE of CH 3 Cl on different Cu(410) sites range from −0.02 to −0.30 eV.…”

Catalytic de-halogenation of alkyl halides by copper surfaces

“…underpin the catalytic capacity of copper-terminated (100) surface with other copper terminations, we have contrasted our obtained activation energies for dissociation reactions in selected halogenated hydrocarbons molecules with corresponding values ensued over another copper termination surface (i.e., Cu(410))[61]. FigureS1(in the supplementary materials) shows that fission of the C-Cl bond in the CH3Cl molecule over copper-terminated (410) requires slightly higher activation barrier (10.3 kcal mol -1 ) in reference to the value calculated here for the clean Cu(100) surface; i.e., 8.3 kcal mol -1 .…”

Catalytic cracking of CH3Cl on copper-based phases

“…80 years after the independent discovery by R. Müller and E. G. Rochow, the direct synthesis reaction, given in eqn (1), remains the most common method for the synthesis of organosilicon compounds. [1][2][3][4][5][6][7] Si(s) + 2CH 3 Cl(s) → (CH 3 ) 2 SiCl 2 (g) (1) It is an important industrial process with a high amount of silicones produced per year (2.4 million metric tons in 2019) 8 with major applications such as construction, electronics, transportation, medical, personal care and others. 5 Therefore, the optimization of the silicones production via the increase in production yield is crucial as well as better energy efficiency and raw materials utilization and lower greenhouse gas emissions.…”

“…5 Therefore, the optimization of the silicones production via the increase in production yield is crucial as well as better energy efficiency and raw materials utilization and lower greenhouse gas emissions. For the direct synthesis, silicon powder is mixed with a copper-based catalyst [1][2][3][4][5] and gaseous CH 3 Cl in a fluidized bed reactor at temperature and pressure ranging between 280-350 °C and 1-10 bar. 9,10 The nature of the copper precursor strongly influences the catalytic performance and promoters such as Zn, Sn, Al and P contribute to increase the activity, stability, and selectivity toward chlorosilanes 5,7,[10][11][12][13][14][15][16] (mostly desired dimethyldichlorosilane, but also methylchlorosilane, trimethylchlorosilane, methyldichlorosilane, dimethylchlorosilane and tetramethylsilane).…”