压力和温度对4-甲基二苯并噻吩和二苯并噻吩加氢脱硫反应的影响

研究了4-甲基二苯并噻吩(4-MDBT)和二苯并噻吩(DBT)在CoMo/γ-Al2O3上的加氢脱硫反应产物分布及其可能的反应网络,通过反应压力和温度对产物分布影响的研究,揭示了加氢脱硫反应的可能机理。研究发现4-MDBT在CoMo/γ-Al2O3上的加氢脱硫反应主要通过直接氢解路径和加氢路径进行,且两者反应速率相当；DBT在 CoMo/γ-Al2O3上的加氢脱硫反应主要通过直接氢解路径进行。4-MDBT分子位于4位的甲基阻碍其在催化剂表面通过硫原子的端连吸附,从而降低了其直接氢解脱硫路径的反应速率,因而也降低了其总的加氢脱硫转化率。反应压力降低,DBT和4-MDBT加氢脱硫反应中加氢路径反应速率明显下降,而其对氢解路径影响较小,但效果却与加氢路径相反,反应压力对4-MDBT转化率的影响大于DBT。反应温度对DBT和4-MDBT加氢脱硫反应中加氢路径和氢解路径都有明显影响,但是对DBT加氢脱硫反应中氢解路径的影响小于加氢路径,而对4-MDBT加氢脱硫反应中氢解路径的影响稍高于加氢路径,4-MDBT分子中甲基的供电子作用有利于相连苯环的加氢反应。

EFFECTS OF REACTION PRESSURES AND TEMPERATURES ON THE HYDRODESULFURIZATION OF 4-METHYLDIBENZOTHIOPHENE AND DIBENZOTHIOPHENE

Hydrodesulfurization(HDS) of 4-methyldibenzothiophene(4-MDBT) and dibenzothiophene(DBT) on sulfided CoMo/γ-Al2O3 catalyst was studied. Moreover, reaction networks and mechanisms were revealed on the basis of GC and GC-MS analyses of the reaction products. It was found that the HDS of 4-MDBT on sulfided CoMo/γ-Al2O3 catalyst occurs through the direct hydrogenolysis of C-S bond of 4-MDBT and hydrogenation routes, the con-tributions of both routes being comparable. HDS of DBT on the sulfided CoMo/γ-Al2O3 catalyst occurs essentially through the direct hydrogenolysis route. The methyl group in 4-MDBT causes the spatial restraining for the “end up adsorption” of sulfur atom on the active site of the catalyst, which slows down the reaction rate of the direct hydro-genolysis route and leads to the reduction of conversion of 4-MDBT. The reaction rate of the hydrogenation routes in HDS of 4-MDBT and DBT obviously decreases with the descending of reaction pressure. Reaction pressure was also found to have smaller and opposite effects on hydrogenation routes and the direct hydrogenalysis routes in HDS of 4-MDBT and DBT, i.e., the reaction rate of the direct hydrogenalysis routes slightly ascends with the descending of reaction pressure. The effect of reaction pressure on the conversion of 4-MDBT is higher than that on DBT. Reaction temperature has obvious effect on both the direct hydrogenolysis routes and the hydrogenation routes in HDS of 4-MDBT and DBT. Moreover, effect of temperature on the direct hydrogenolysis route in HDS of DBT is lower than the hydrogenation route. However, the effect of temperature on the direct hydrogenolysis route in HDS of 4-MDBT is slightly higher than the hydrogenation route. The electron donor induction of the methyl group in 4-MDBT can promote the hydrogenation of the adjacent benzene ring.