活性炭表面基团的调变对Ru/AC氨合成催化剂的影响

Effects of Surface Functional Groups on the Performance of Ru/AC Catalysts for Ammonia Synthesis

通过硝酸处理的方法对活性炭表面基团进行了调控,研究了活性炭表面基团的数量对负载钌基氨合成催化剂的影响。运用N2物理吸附、CO化学吸附、Boehm滴定法和质量滴定法等分析手段对催化剂进行了表征。结果表明,随着预处理硝酸浓度的增加,活性炭表面含氧基团的数量线性增加,等电点逐渐减小,而催化剂的活性先增加后减小,钌的分散度也呈现相同的规律。当硝酸浓度达到4.6mol/L时,活性炭表面总含氧基团量为1.21mmol/g,钌的分散度和催化剂的活性都是最佳。适量的含氧基团对提高钌的分散度是有利的,但过量的含氧基团并不能进一步提高钌的分散度,催化剂的合成氨活性和载体表面的含氧基团数量不是线性增加的关系。

The surface functional oxygen-contained groups of activated carbon were controlled by nitric acid treatment.The effect of the amount of the surface oxygen-containing groups of activated carbon on the performance of Ru-based ammonia synthesis catalyst was studied.The properties of activated carbons and catalysts were characterized by N2 physical adsorption,CO chemisorption,Boehm titration and the quality titration methods.The results showed that the amounts of surface oxygen-containing groups of activated carbon increased linearly and the point of zero charge gradually decreased with increasing of nitric acid concentration.The dispersion of Ru and the catalytic activity increased when the amount of surface functional groups was low and then decreased slightly when the amount of functional groups further increased.When the concentration of nitric acid was 4.6mol /L,the amount of oxygencontaining groups was 1.21mmol /g,the Ru dispersion and the catalytic activity of the catalyst were the highest.Appropriate amount of oxygen-containing groups on the Ru loading on activated carbon played an important role,but the excessive amount of oxygen-containing groups did not further improve the dispersion of ruthenium,the catalytic activity of the catalyst and the amount of oxygen-containing groups was not a linear relationship.