Cu/γ-Al_2O_3的制备及其对纯甘油常压氢解制备1,2-丙二醇的催化性能

Preparation of Cu/γ-Al_2O_3 Catalyst and Its Catalytic Performance in Hydrogenolysis of Pure Glycerol to 1,2-Propanediol at Ambient Pressure

采用H2-TPR、XRD、CO化学吸附、N2吸附-脱附等方法表征了等体积浸渍法制备的Cu/γ-Al2O3催化剂,并评价了其催化甘油氢解制备1,2-丙二醇(1,2-PDO)反应的性能。结果表明,Cu/γ-Al2O3的适宜Cu负载量为15%(质量分数),适宜的制备条件为,采用纯H2还原、升温速率2℃/min、还原温度250℃、还原时间2h。在常压氢气、甘油液时空速0.20h-1、氢气/甘油摩尔比100、催化剂装填量3mL和反应温度190℃的条件下,甘油转化率为100%,1,2-PDO选择性为92.9%;反应运行36h,1,2-PDO选择性仍高于85%,说明Cu/γ-Al2O3催化剂的稳定性较好。Cu/γ-Al2O3催化剂表面以高分散的Cu微粒为主,Cu粒子的粒径和分散度是影响其活性的主要因素;Cu粒子的粒径越小、分散度越大,催化活性越高。甘油脱水生成丙酮醇的反应只有在酸性中心和金属共同作用下才能进行,丙酮醇加氢合成1,2-丙二醇是反应控制步骤。

The physicochemical properties of Cu/y-A12O3 catalyst prepared by incipient impregnation method were studied by means of H2-TPR, XRD, CO chemisorption, N2 adsorption-desorption measurement. The catalytic performance of Cu/y-A12O3 for glycerol hydrogenolysis to 1,2-propanediol （1, 2-PDO） was evaluated. The results showed that the suitable Cu loading of Cu/y-A12O3 was 15%, and the suitable preparation conditions were reduction atmosphere of pure hydrogen, temperature rising rate of 2℃/min, reduction temperature of 250℃ and reduction time of 2 h. Under the reaction conditions of pure glycerol, atmospheric pressure, n（H2）/n（Glycerol）= 100,Cu/y-A12O3 volume of 3 mL, LHSV= 0.20 h 1 and reaction temperature of 190℃, the conversion of glycerol was 100%, and the selectivity of 1, 2-PDO was 92.9%. Furthermore, the selectivity of 1, 2-PDO was not less than 85% during the 36 h stability test, demonstrating that Cu/y-A12O3 catalyst exhibited a good stable activity. In Cu/y-A12O3 catalyst Cu particles were highly dispersed on the surface of y-A12O3. The particle size and dispersion of Cu were the main factors influencing the catalytic performance of Cu/y-A12O3. The smaller the particle size and the higher the dispersion of Cu, the better the catalytic performance of Cu/y-A12O3 was. The conversion of glycerol to acetol required both acid sites and metal sites, and the hydrogenation of acetol to 1,2-PDO was the rate controlling step of glycerol hydrogenolysis to 1,2-PDO.