The Direct Method Of Cayalyzingmonohydric Alcohol And Silicon Synthesisof Alkoxysilane Research Over Copper-Based Catalyst

In this paper,the preparation of methoxysilane and ethoxysilane from methanol,ethanol and silicon powder catalyzed by copper-based catalyst in a fixed-bed reactor was studied.The research results are as follows:In the study of catalytic synthesis of methoxysilane over copper-based catalysts,it was found that CuCl/Si mixture was pretreated at 200-240℃in nitrogen atmosphere,and CuCl/Si phase still existed in CuCl/Si mixture,Cu⁰ phase appeared after pretreatment at 260-340℃,and Cu₃Si formed after pretreatment at 200-240℃.When CuCl/Si was preheated at 200-240℃,trimethoxysilane was dominantly formed at the reaction temperatures of 220-260℃.And the yield of trimethoxysilane is up to 85%.When the pretreatment temperatures were raised to 260–340 ^oC,tetramethoxysilanewasfavorablyformedatthereactiontemperaturesof220-260℃,and the yield of tetraethoxysilane is up to 93%.The study found that,the Cu_xSi_yCl_zspecies catalyzed the reaction between silicon and methanol to trimethoxysilanewhiletheCu⁺/Cu⁰speciescatalyzedtheformationof tetramethoxysilane.After the deactivation of CuCl catalyst,the deactivated CuCl/Si mixture was regenerated by chlorination,which promoted the reaction of methanol with silicon powder to form trimethoxysilane and tetramethoxysilane.This is due to the recovery of cuprous chloride phase and the exposure of copper phase by chlorination treatment.When Cu₂O,CuO and Cu⁰ are used as catalysts for the direct reaction of methanol with silicon powder,Cu₂O and CuO are reduced to metal Cu⁰,and tetramethoxysilane is the main product.In the study of synthesis of ethoxysilane catalyzed by copper-based catalysts.It was found that CuCl and Cu⁰ nanoparticles could selectively synthesize triethoxysilane and tetraethoxysilane by direct reaction of silicon with ethanol,respectively.When CuCl/Si mixture is pretreated in nitrogen flow,the metal Cu⁰ phase appears at260–500℃and the Cu₃Si phase appears at 280–500℃.When the CuCl/Si mixture is pretreated at 240–300℃,it is beneficial to the formation of triethoxysilane,and the selectivity of triethoxysilane is up to 94%.However,when pretreated at 500℃,tetraethoxysilane can befavorably formed,and the selectivity of tetraethoxysilane can reach 99%.The catalytic activity of small size CuCl is higher than that of large size CuCl.It was found that the Cu-Si-Cl complex may be the active site for the formation of triethoxysilane,while the metal Cu⁰ microcrystal is the active site for the formation of tetraethoxysilane.The reaction of solid waste of silicon powder-copper-based catalyst produced in the production of organosilicon with HCl showed that the waste silicon powder could react directly with HCl to produce trichlorosilane.At 280–320℃,the selectivity of trichlorosilane is over 90%,and the rest is silicon tetrachloride.In this study,the industrial chain of preparing alkoxysilane from silicon powder was formed,and the reacted silicon powder was further reacted with HCl to prepare chlorosilane.The research results have the advantages of green and environmental protection.