活性炭负载AlCl_3固体酸催化甲基氯硅烷再分配反应性能与结构研究

Activated carbon supported AlCl_3 solid acid catalyst:structural characterization and catalytic properties for redistribution reaction of methylchlorosilane

以活性炭为载体，采用浸溃蒸发煅烧法制备了负载型AlC13固体酸催化剂，并以甲基三氯硅烷（M1）和三甲基氯硅烷（M3）的再分配反应为模型反应，在φ20mm×800mm的固定床反应器中，310℃、n（M1／M3）=1．0、液时空速1．5h^-1下考察了催化剂的制备条件对其反应活性的影响，并对催化剂的稳定性进行了初步考察．运用N2等温吸附-脱附法、XRD、TG-DSC和吡啶吸附Raman光谱等手段对催化剂的结构和酸性进行了表征．结果表明，较佳的催化剂制备条件为：活性炭经过2．0mol·L^-1盐酸溶液处理6h，AlC13负载量为1.87mmol·g^-1，450-500℃焙烧活化;催化剂在100h内表现出良好的催化稳定性．催化剂的XRD和TG-DSC表征结果表明，AlCl3负载到活性炭载体上经活化后不再以AlCl3晶相存在，催化剂在485～600℃时活性组分出现分解；吡啶吸附Raman光谱分析表明催化剂的活性组分为Lewis酸。

Methyltrichlorosilane （M1） and trimethylchlorosilane （M3） are usually produced as byproducts in the direct synthesis process of dimethyldichlorosilane. The two chemicals could be converted into more valuable dimethyldichlorosilane through the redistribution technology. By using activated carbon as support, environmentally benign activated carbon supported AlCl3 solid acid catalysts were prepared by the impregnation-evaporation-calcination method. The effects of acid-treatment conditions, AlCl3 loading and activation （calcination） temperature on the catalytic activity were examined for the redistribution reaction of methyltrichlorosilane and trimethylchlorosilane in a φ20 mm×800 mm fixed bed reactor under conditions of 310℃, n（M1/M3）= 1.0 and LHSV= 1.5 h^-1, and the stability of catalytic activity was investigated also. The structure and surface properties of catalysts were claaracterized with BET, XRD, TG-DSC and pyridine-adsorbed Raman spectroscopy. The results revealed that it would be better if the activated carbon was treated by hydrochloric acid of 2.0 mol·L^-1 for 6 h, and suitable conditions for AlCl3 loading and calcination temperature were 1.87 mmol·g^-1 and 450-500℃ respectively. The stability of the activated carbon supported AlCl3 catalyst was good for at least 100 h. Th＇e XRD and TG-DSC results indicated that AlCl3 would no longer exist in the form of AlCl3 crystal after it was supported on activated carbon and activated. The TGDSC analysis showed that further heating of the catalyst at 485-600℃ resulted in decomposition and removal of active component from the catalyst surface. The pyridine-adsorbed Raman spectroscopy revealed that the active component of the catalyst behaved as Lewis acid.