Mechanism on The Disproportionating Synthesis of Dichlorodimethyl‐ silane by ZSM‐5(5 T)@γ‐Al 2 O 3 Series Core‐Shell Catalysts

Effect of inlet gas velocity on gas-solid fluidization characteristics in fluidized bed

In this article, the Eulerian–Eulerian TFM model is used to simulate the fluidization of the synthesis process of organosilicon monomers. A new method for analyzing the gas-solid fluidization characteristics is proposed by combining the gas-solid two-phase flow evolution formula with the parameters such as particle concentration and bed voidage. On this basis, the fluidization characteristics of silicon powder particles at constant velocity and variable velocity are compared, and the fluidization characteristics of silicon powder particles with different particle sizes under five sets of variable velocity are discussed. The simulation results show that compared with constant velocity, the mean bed voidage is 0.55 when silicon particles adopt variable velocity, which can not only keep silicon particles fully fluidized but also improve the problem of poor gas-solid contact. For silicon particles with particle diameters of 300.1–515 μm, variable velocity fluidization has the advantages of uniform bed distribution and sufficient gas-solid fluidization. In the five groups of variable velocity function, when the inlet gas velocity and time are the quadratic functions of the opening upward, the fluctuation of pressure fluctuation is small, and the maximum fluctuation range of particle solid phase distribution is only 0.13, indicating that the heat and mass transfer efficiency between silicon particles is better, the gas-solid mixing is sufficient, and the gas-solid fluidization quality is better.

Mechanism on redistribution synthesis of dichlorodimethylsilane by AlCl3/ZSM-5(3T)@γ-Al2O3 core-shell catalyst

The redistribution method plays an important role in addressing the issue of organosilicon by-products in the direct synthesis of dichlorodimethylsilane, and the redistribution mechanism is still a topic of debate. The redistribution mechanism by the ZSM-5(3 T)@γ-Al₂O₃ core-shell catalyst and post-modified AlCl₃/ZSM-5(3 T)@γ-Al₂O₃ catalyst was technically performed using the Density functional theory (DFT) at the level of B3LYP/6-311 +  + G(3df,2pd). The results show that no. 1 active site of ZSM-5(3 T)@γ-Al₂O₃ core-shell structure has a significant effect on the activity of the catalyst. Indicating that the active center involved in the reaction is H provided by the Al-O-H bond, which is an obvious catalytic active center of Bronsted acid. Furthermore, the post-modified AlCl₃/ZSM-5(3T)@γ-Al₂O₃ catalyst is in more favor of redistribution reaction comparing with the ZSM-5(3 T)@γ-Al₂O₃ core-shell catalyst. It ascribes to the robust Lewis site of aluminum chloride favorable modification. The redistribution synthesis mechanism of dichlorodimethylsilane on the ZSM-5(3 T)@γ-Al₂O₃ core-shell catalyst and post-modified AlCl₃/ZSM-5(3 T)@γ-Al₂O₃ catalyst had been investigated by using the Density functional theory (DFT) method at the level of B3LYP/6-311 +  + G(3df,2pd). The former active center was Bronsted acidic center, while the latter one was Lewis acidic center, ascribing to the Lewis site of aluminum chloride favorable modification. The catalytic activity of the post-synthesis AlCl₃/ZSM-5(3 T)@γ-Al₂O₃ catalyst completely was consistent with experimental results.