La2O3对Pd/Al2O3催化蒽醌氢化制H2O2性能的影响

 采用湿浸法制备了用于蒽醌氢化制H2O2的La2O3促进的Pd/Al2O3催化剂,并考察了不同La2O3含量对催化性能的影响. 采用XRD,N2物理吸附,CO2-TPD,H2-O2滴定和电子探针等技术对催化剂进行了表征. 结果表明,加入适量的La2O3能够抑制高温焙烧时Al2O3晶粒的长大,增大催化剂的比表面积,提高金属Pd的分散度,增强载体表面碱性,提高催化剂表面的Pd浓度,减小Pd层厚度,从而提高催化剂的氢化活性. 加入La2O3可使催化剂的Pd负载量由0.281%降至0.188%,而催化剂活性提高了44%.

Effect of Lanthanum Oxide on Catalytic Performance of Pd/Al2O3 Catalyst for Anthraquinone Hydrogenation to H2O2

The Pd/Al_2O_3 catalyst promoted with La_2O_3 for anthraquinone hydrogenation to H_2O_2 was prepared by impregnating Al_2O_3 with aqueous solutions of lanthanum nitrate and Na_2PdCl_4 succesively. The effect of lanthanum oxide on the catalytic performance of Pd/Al_2O_3 catalyst was investigated by means of X-ray diffraction, N_2 adsorption, temperature-programmed desorption of CO_2, H_2-O_2 titration and electron probe microanalysis. The results showed that lanthanum oxide was a good promoter of Pd/Al_2O_3 for the reaction. It could inhibit the growth of alumina crystals at high temperature, increase the surface area, enhance the surface alkalinity of Al_2O_3, improve the Pd dispersion on the support, increase the Pd concentration, decrease the Pd layer thickness on the catalyst surface, and thus improve the catalytic activity effectively. The addition of La_2O_3 could decrease the Pd loading from 0.281% to 0.188%, while the catalyst activity increased by 44%.