载体预处理对Pd/C催化剂催化性能的影响

研究了活性炭硝酸表面改性对以其为载体制备的负载钯催化剂性能的影响。利用表面官能团滴定、N₂物理吸附和扫描电镜对催化剂进行表征，以邻硝基氯苯催化加氢制备2，2'-二氯氢化偶氮苯反应为模型反应对催化剂的性能进行评价。结果表明，经过不同浓度的HNO₃处理，活性炭孔结构性能变化不大，但是活性炭表面酸性含氧基团的浓度有了较大程度的增长，为Pd金属粒子的沉积提供了大量的吸附位，提高了Pd金属的分散度，从而制得高活性的Pd/C催化剂。通过30%HNO₃ 60 ℃水浴中回流4 h处理的活性炭可以达到最佳效果，所制得催化剂的活性是以未经硝酸处理过的活性炭载体制备的催化剂活性的2.3倍。

Effects of pretreatment of activated carbon on the activity of Pd/C catalysts

The effects of surface modification of activated carbon (AC) by pretreatment with HNO₃ on behaviors of Pd/C catalysts were investigated. The activated carbon supports and the catalysts were characterized by chemical titration of surface groups, N₂ physical adsorption and SEM. Activity of Pd/C catalysts for 2,2'-dichlorohydrobenzene synthesis was tested. The results showed that activated carbon support treated with nitric acid of different concentration did not remarkably changed the surface structure of activated carbon, but resulted in considerable increase in the surface acidic groups. These led to higher dispersion of palladium and enhanced the activity of the catalysts prepared by impregnation with PdCl₂ aqueous solution. Optimal results were obtained over the catalyst prepared by treatment of the activated carbon with 30% HNO₃ at 60 ℃ for 4 h with reflux in water bath, which exhibited activity 2.3 times higher than that without pretreatment.