苯选择性加氢Ru/TiO_2催化剂载体晶型效应研究

Study on the Crystalline of Ru/TiO_2 Catalyst for Selective Hydrogenation of Benzene

以不同晶型的TiO_2为载体采用化学还原浸渍法制备了三种Ru/TiO_2催化剂,并利用X射线衍射(XRD)、N_2吸附-脱附、透射电镜(TEM)、NH_3程序升温脱附(NH_3-TPD)和傅里叶变换红外光谱(FTIR)等表征手段研究了催化剂的物理化学性质,考察了其在苯选择性加氢反应中的催化性能。结果表明:苯选择性加氢活性与Ru/TiO_2催化剂的Ru粒子分散度有关,Ru粒子分散度越高,催化活性越高;而环己烯选择性与Ru/TiO_2催化剂的酸量呈负相关,Ru/TiO_2-P催化剂的酸量最低,对环己烯的吸附量最低,在相同转化率下苯加氢生成环己烯的选择性最高。动力学分析表明,苯加氢生成环己烯的反应速率常数(k_1)与环己烯加氢生成环己烷的反应速率常数(k_2)的比值与环己烯收率呈近似正相关。

Three types of Ru/TiO2catalysts were prepared by chemical reduction impregnation method with different crystal forms of TiO2.The catalysts were characterized by X-ray diffraction(XRD),N2adsorption-desorption,transmission electron microscopy(TEM),NH3-temperature programmed desorption(NH3-TPD)and Fourier transform infrared spectroscopy(FTIR)were used to study the physicochemical properties of the catalysts.The catalytic performances of Ru/TiO2catalysts in the selective hydrogenation of benzene to cyclohexene were also investigated.The results showed that the activity of benzene hydrogenation was related to the dispersion of Ru in the Ru/TiO2catalysts.The higher the dispersion of Ru was,the higher the catalytic activity was and the selectivity of cyclohexene was negatively correlated with the acid amounts of Ru/TiO2catalysts.The Ru/TiO2-P catalyst had the lowest acid content,the adsorptioncapacity of cyclohexene was the lowest,and the selectivity of cyclohexene was the highest at the same conversion rate.The kinetic analysis showed that the resulting k1/k2ratio of the rate constants of the benzene to cyclohexene step(k1)and the cyclohexene to cyclohexane step(k2)was approximately positively correlated with the yield of cyclohexene.