Au/SiO_2催化剂上丙烯空气氧化制丙烯醛

Selective Oxidation of Propene to Acrolein Using Air as Oxidant over Au/SiO_2 Catalyst

采用等体积浸渍法制备了Au/S iO2催化剂,X射线粉末衍射、透射电子显微镜表征结果显示,其金粒子的平均大小可控制在10nm以内。考察了反应温度、空速、金负载量、催化剂焙烧温度、添加助剂等对Au/S iO2催化剂催化丙烯空气氧化制丙烯醛反应性能的影响。实验结果表明,该催化剂具有很高的丙烯醛选择性。在325℃、原料气空速4 000h-1、V(C3H6)∶V(O2)=1∶2、反应时间120m in的条件下,采用500℃焙烧的Au/S iO2催化剂,当丙烯的转化率为1.0%时,丙烯醛的选择性达70%以上。提高焙烧温度至800℃,丙烯醛选择性可达90%。加入Cu助剂可以提高丙烯的转化率,但使丙烯醛选择性下降。

SiO2 - supported Au catalyst was prepared by impregnating and adjusting pH value of HAuCl4 solution. XRD and TEM measurements showed that size of gold particles could be controlled below 10 nm. XPS characterization indicated that some chlorine ions still existed on catalyst surface after washing with water. Au species existed in metallic state. Influences of reaction temperature, space velocity, Au loading, calcination temperature and promoter on catalytic performance in synthesis of acrolein were investigated. Catalyst showed very high selectivity of acrolein but low propene conversion. Under optimal reaction conditions： temperature 325 ℃, V（ C3 H6 ） ： V（ O2 ） = 1 ： 2, GHSV 4 000 h^ -1, reaction time 2 h, and calcination temperature of catalyst 500 ℃ ,although conversion of propene was only 1% , selectivity of acrolein could reach more than 70%. When calcination temperature rose to 800 ℃, selectivity of acrolein could even exceed 90%. Adding Cu promoter could distinctly improve activity of catalyst but would make acrolein selectivity decreasing.