The direct synthesis of methylchlorosilanes I. Steady-state and transient reaction kinetics

An extensive laboratory reaction kinetics study was performed on the "direct process" of methyl chloride and silicon, also commonly referred to as the methylchlorosilane (MCS) reaction. Temperature and concentrations of copper, zinc, and tin were varied. Reaction rate reproducibility and repeatability were improved by increasing temperature homogeneity in our fixed-bed reactor system. A stripped gas chromatograph (GC) oven, a detailed standard operating procedure, and small-diameter fixed-bed reactors were used to achieve good temperature control. The kinetics study incorporated multiple sample points per run as opposed to a single sample. The complete kinetics data set was analyzed with statistical analysis tools (SAS, Minitab). Three silicon utilization windows (0-15%, 15-30%, and g30%) were assumed to determine reaction rate descriptions by so-called transfer functions. The developed model supports a proposal wherein at least two processes exist. The main reaction (the MCS reaction) produces dimethyldichlorosilane (Di) and equimolar amounts of trimethylchlorosilane (mono) and methyltrichlorosilane (Tri). At least one side reaction occurs during the MCS deactivation phase resulting in higher levels of Tri and other byproducts.

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“…The Rethwisch group used a continuous fixed-bed reactor system and determined the reaction rate as a function of catalyst composition …”

Section: Introductionmentioning

confidence: 99%

Mechanism of the Methylchlorosilane Reaction: Improved Lab Reactor Design and Kinetic Data

Bablin

Lewis

Bui

et al. 2003

Ind. Eng. Chem. Res.

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“…Synthetic reaction kinetics were generally measured employing contact mass prepared from silicon, catalyst, and promoters in a fixed-bed reactor. For this case, the synthesis reaction rate r (the number of molecules of methyl chloride that react per hour per kg of contact mass) can be expressed by eq : where k is the reaction rate constant (g silane/kg Si/h); K is the adsorption equilibrium constant (atm –1 ), which usually changes with temperature ( K A = 94.1 – 10.89 T + 9.74 E – 4 T 2 ); P is the partial pressure (atm); the subscripts A and B represent MeCl and silane, respectively; and n and m are 1 and 2, respectively. This kinetics law belongs to the classical Hougen–Watson approach.…”

Section: Mechanism and Kinetics Of The Direct Synthesismentioning

confidence: 99%

“…To characterize the reaction rate in a meaningful way, it must be independent of the amount of silicon particles and the MeCl gas flow rate. where , , , k p is reaction rate constant (kg silane/kg Si·h), F is the MeCl feed gas flow (mol/h), M Si is the silicon amount in reactor (mol), P is the total reactor pressure (atm), and X is the fraction of MeCl conversion. For low conversions, Kim et al proposed that the rate expression eq can be simplified as follows: where q is the apparent reaction order. Authors measured the apparent reaction order with respect to methyl chloride using different catalysts (see Table ).…”

Section: Mechanism and Kinetics Of The Direct Synthesismentioning

confidence: 99%

“…, k p is reaction rate constant (kg silane/kg Si•h), F is the MeCl feed gas flow (mol/h), M Si is the silicon amount in reactor (mol), P is the total reactor pressure (atm), and X is the fraction of MeCl conversion. For low conversions, Kim et al 40 proposed that the rate expression eq 3 can be simplified as follows:…”

Section: Mechanism and Kinetics Of The Direct Synthesismentioning

confidence: 99%

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

Zhang

Dong

et al. 2022

Org. Process Res. Dev.

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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.

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“…The diffusion of silicon atoms, through the solid phase onto active sites of the catalyst, where they can react with the MeCl, is considered as the rate determining step in the direct synthesis process 47 . Based on the above theory, the rate expression for the direct reaction has been assumed to be of the form 48 : where k is the apparent rate constant, K are adsorption equilibrium constants for MeCl (A), and silane (B), (atm −1 ), P are partial pressure for MeCl (A), and silane (B), (atm)…”

Section: Modelmentioning

confidence: 99%

Effect of Bed Characters on the Direct Synthesis of Dimethyldichlorosilane in Fluidized Bed Reactor

Zhang

Duan

Chen

et al. 2015

Sci Rep

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This paper presents the numerical investigation of the effects of the general bed characteristics such as superficial gas velocities, bed temperature, bed heights and particle size, on the direct synthesis in a 3D fluidized bed reactor. A 3D model for the gas flow, heat transfer, and mass transfer was coupled to the direct synthesis reaction mechanism verified in the literature. The model was verified by comparing the simulated reaction rate and dimethyldichlorosilane (M2) selectivity with the experimental data in the open literature and real production data. Computed results indicate that superficial gas velocities, bed temperature, bed heights, and particle size have vital effect on the reaction rates and/or M2 selectivity.

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The direct synthesis of methylchlorosilanes I. Steady-state and transient reaction kinetics

Cited by 28 publications

References 9 publications

Mechanism of the Methylchlorosilane Reaction: Improved Lab Reactor Design and Kinetic Data

Mechanism of the Methylchlorosilane Reaction: Improved Lab Reactor Design and Kinetic Data

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

Effect of Bed Characters on the Direct Synthesis of Dimethyldichlorosilane in Fluidized Bed Reactor

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