Au/ZrO2催化剂中ZrO2的尺寸效应:1,3-丁二烯加氢反应

在不同温度(673～1073K)下,于流动N2气中焙烧ZrO(OH)2醇(乙醇)凝胶,制备了不同尺寸的ZrO2-AN纳米晶(6～30nm).采用沉积-沉淀方法制备了相应的质量分数为0.7%的Au/ZrO2-AN催化剂.用XRD,XRF,TEM/HRTEM,EDS,N2吸附和1,3-丁二烯加氢反应对ZrO2-AN和Au/ZrO2-AN催化剂进行了表征.结果表明,在所有的Au/ZrO2-AN样品中,Au粒子的平均尺寸为4～5nm,ZrO2-AN的颗粒大小没有因为负载Au粒子而发生改变.1,3-丁二烯在Au/ZrO2-AN催化剂催化下能以100%的选择性进行加氢反应生成单烯烃.随着Au/ZrO2-AN催化剂中ZrO2-AN纳米晶尺寸的增加或“载体”焙烧温度的升高,1,3-丁二烯的转化率明显降低;1-丁烯的选择性先增加后减小,2-丁烯中反/顺异构体的摩尔比在0.5～1.0的范围内逐渐增大,TEM/HRTEM表征结果清楚地表明,Au/ZrO2-AN催化剂中Au粒子与ZrO2-AN颗粒接触界面/周边随ZrO2-AN颗粒尺寸的减小而明显增加,这很可能是含有更小尺寸ZrO2-AN纳米粒子的Au/ZrO2-AN催化剂具有更高的催化活性的重要原因.

Size Effect of Zirconia Nanoparticles in Au/ZrO2 Catalysts for 1,3-Butadiene Hydrogenation

This work explores the size-effect of zirconia nano particles on the catalysis of Au/ZrO2-AN catalyst for 1,3-butadiene hydrogenation. Zirconia nanoparticles with different sizes(6—30 nm) were prepared by pretreatment at different temperatures(673—1 073 K) and 0.7%Au/ZrO2-AN-T catalysts by deposition-precipitation method. The samples were characterized with XRD, TEM, XRF and nitrogen adsorption measurements. While the Au particles in all the 0.7%Au/ZrO2-AN-T catalysts appeared to show similar sizes(4—5 nm), the catalytic activity order for 1,3-butadiene hydrogenation clearly revealed that smaller zirconia nanoparticles led to 1%Au/ZrO2-AN-T catalyst with higher catalytic activities. A 100% selectivity to butenes is achieved and the trans to cis ratio in 2-butenes is 0.5—1 over all the 1%Au/ZrO2-AN-T catalysts. The activity improvement by reducing zirconia particle size seems attributable to increased Au-zirconia junctions in the catalyst, as evidenced by the TEM analysis.