Direct Synthesis of Methylchlorosilanes: Catalysts, Mechanisms, Reaction Conditions, and Reactor Designs

Abstract

Silicone polymers are produced commercially mainly from methylchlorosilanes prepared by direct synthesis. The yield and selectivity of this synthetic process depend not only on chemical reactions but also on transfer phenomena, leading to conflicting results and controversial interpretations within this research field. This review highlights recent advances in synthesis mechanisms, including catalysts and promoters, especially the effect of process parameters and reactor form on the reactivity and selectivity of the reaction. This review shows that different catalysts and their structures and promoters lead to significant differences in reaction rates and product distributions. Process parameters such as feed gas velocity and composition, reaction temperature, reaction pressure, silica fume, etc., as well as synthesis reactor structure have influenced the reaction rate and yield distribution. Although there is some consensus on understanding the influence of operating parameters, synthesis reactor structure, and reaction kinematics, further studies are still needed to elucidate the catalytic mechanism and synergistic mechanism between the reaction and transfer processes. It also reviews recent trends in these response characteristics in previously reported studies and offers important directions for future research in this field.

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

“…The industrial process productivity is related to the reactivity (how much Si is converted) and selectivity (desired products vs byproducts) resulting from the adjustment of the reactor parameters, Si powder characteristics (chemical composition, microstructure, size distribution, etc. ), and additives (catalyst and promoters) . The direct synthesis is assumed to start with the adsorption of CH 3 Cl on the particle surface, and its subsequent decomposition into adsorbed CH 3 and Cl .…”

“…), and additives (catalyst and promoters). 2 The direct synthesis is assumed to start with the adsorption of CH 3 Cl on the particle surface, and its subsequent decomposition into adsorbed CH 3 and Cl. 3 Adsorbed CH 3 can further decompose to CH 2 , CH, and C, producing an adsorbed H on the surface for each step.…”

Utilization of Silicon Dust to Prepare Si3N4 Used for Steelmaking Additives: Thermodynamics and Kinetics

“…Based on the EDS results, it was found that the first type of powder has bright white ferrosilicon particles attached to the surface, as shown in Figure 2b. The other type of powder particles have a mixture of Si and SiO 2 on the surface, with pits of different sizes as shown in Figure 2c, and there are pits of different sizes, which are caused by the erosion by copper during the preparation of organosilicon monomers using the Rochow-Müller process [15].…”

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

“…The presence of a solid reactant limits the precision of the reaction experiments and the possibility for extracting systematic data since there is no real steady-state, and it is difficult to ensure the absence of concentration and temperature gradients. The recent review by Zhang et al discusses how different catalysts and promoters in addition to the reactor design and process parameters influence the reaction rate and product distribution of the MCS process. The fluidized bed laboratory arrangement adopted in the present work has been developed by Elkem over decades and has demonstrated good reproducibility and capability with respect to extracting valuable insights. − In the present work, the protocol was extended to disentangle the effects of the reaction time and Cu/Si ratio in conjunction with the effect of the Zn promoter.…”

“…The reaction between chloromethane (CH 3 Cl, also called methyl chloride) and silicon (Si) to synthesize methylchlorosilanes (MCS), also known as the Müller-Rochow Synthesis or the Direct Process, is currently the most convenient and economical way to produce MCS industrially. Almost 90% of the starting materials for current silicone manufacturing are obtained with MCS monomers. − On an industrial scale, ground metallurgical grade silicon is mixed with a copper-based catalyst − and minor amounts of various other promoter elements − in a fluidized bed reactor under gaseous CH 3 Cl, at temperature and pressure ranging between 280–350 °C and 1–10 bar. , This quite unique gas (CH 3 Cl)–solid (Si)–solid (Cu-based catalyst) heterogeneous reaction exhibits a complicated dependency on reaction temperature, (partial) pressure(s), reactor type, residence time distribution, and phase/component interactions. , The latter incorporates nature, purity, size distribution, morphology, and proportion of silicon to copper catalyst precursor and promoters . Moreover, a range of methylchlorosilanes, (CH 3 ) x SiCl 4– x , is formed although the dominant and main product of interest is dimethyldichlorosilane, (CH 3 ) 2 SiCl 2 , also referred to as “M2” .…”