以活性炭为载体的碳化钼催化剂在香兰素加氢脱氧反应中的作用

XRD,TEM,N2-吸附等表征手段表明,在700℃下以碳热氢还原方法制备的粒径在1~4nm的β-Mo2C,能够均匀分散在活性炭载体上.在温和条件(100℃,氢压1.0MPa,3h)下,以水作为反应溶剂,质量分数为20.0%的Mo2C/AC催化剂催化香兰素的加氢脱氧反应转化率高达93.2%,2-甲氧基-4-甲基苯酚的选择性达到53.8%.随着负载量的增加,Mo2C/AC催化剂的比表面积呈下降趋势,其活性先增强后减弱,而当负载量增加到一定程度后,Mo2C粒子在载体上发生团聚,导致催化活性大幅度降低.根据原料和产物浓度随时间的变化曲线,提出加氢脱氧反应以香兰醇作为中间产物,经过2步加氢步骤生成2-甲氧基4-甲基苯酚,且第1步加氢反应速率大于第2步.使用多次后,Mo2C/AC催化剂的催化活性几乎不变,说明其具有工业应用前景.

Hydrodeoxygenation of vanillin catalyzed by molybdenum carbide supported on activated carbon

Characterized by X ray diffraction (XRD), transmission electron microscopy (TEM), N2 sorption, the molybdenum carbide (β Mo2C) nanoparticles with diameter from 1 to 4 nm were successfully synthesized by carbothermal hydrogen reduction (CHR) method and highly dispersed on the support at 700 ℃. In this research, vanillin was selected as model compound of the bio oils to test the activity of Mo2C based catalyst for hydrodeoxygenation (HDO). The conversion rates of vanillin and the selectivity of p creosol catalyzed by 20.0 % Mo2C/AC catalyst were 93.7 % and 53.8 % under the mild conditions (100 ℃, 1.0 MPa of H2, 3 h) in aqueous solution, respectively. With the loading increase of Mo2C, the specific surface area of catalysts declined sharply, while the catalytic activity only increased within certain loadings. According to the distribution of products vs. time, the HDO mechanism involved vanillyl alcohol as intermediate product was proposed, and the reaction rate of the first step is higher than the second one, so the second step is the rate determining step. The molybdenum carbide catalyst could be reused for several times without losing its activity, indicating its resistance for deactivation and its promising prospect in being used for HDO.