以活性炭为载体制备Pd和Pt加氢脱硫催化剂

Preparation of Pd and Pt Hydrodesulfurization Catalysts Supported on Activated Carbons

分别以椰壳活性炭、果壳活性炭和木质活性炭为载体,采用等体积浸渍法制备了Pd/C和Pt/C催化剂。以二苯并噻吩(DBT)为模型含硫化合物,考察了不同种类活性炭负载的贵金属催化剂加氢脱硫(HDS)催化性能。结果表明,增加活性炭表面酸性含氧基团或碱性基团数量都有助于提高Pt和Pd的分散度。DBT在Pd/C和Pt/C催化剂催化下进行HDS反应时,直接脱硫(DDS)路径选择性高于加氢反应路径(HYD)选择性,其中Pt/C催化剂的HDS催化活性和DDS路径选择性都显著高于Pd/C催化剂。Pd/C和Pt/C催化剂的HDS催化性能主要取决于载体表面官能团的种类和分布。Pd和Pt催化剂的HYD反应路径选择性和稳定性都随载体表面酸性含氧基团的增加而增加,但它们断裂C—S的活性却有所降低;增加载体表面碱性基团数量则有助于提高催化剂断裂C—S的活性,但不利于其稳定性。

The Pd and Pt hydrodesulfurization （HDS） catalysts supported on coconut shell activated carbon, nut shell activated carbon, and wood activated carbon were prepared by an incipient wetness impregnation method. The HDS catalytic performances of these noble metal catalysts supported on different activated carbons were investigated by using a model feed containing 0.8% dibenzothiophene （DBT） in decalin. The results indicated that the dispersion of Pd and Pt could be enhanced by increasing the amounts of either the acidic oxygen-containing groups or the basic groups on the surface of the support. In the HDS of DBT over the Pd/C and Pt/C catalysts, the selectivity toward the direct desulfurization pathway （DDS） was higher than that toward the hydrogenation pathway （HYD）. Both the HDS activity and the DDS pathway selectivity of the supported Pt catalysts were significantly higher than those of the supported Pd catalysts. The HDS catalytic performances of the Pt/C and Pd/C catalysts were mainly determined by the surface groups of the support and their distributions. An increase of the surface acidic oxygen-containing groups led to an increase of the HYD selectivity and the stability of the Pd and Pt catalysts, but a decrease in their C-S bond cleavage activity. On the other hand, the basic groups showed a positive effect on the C-S bond cleavage activity of Pd/C and Pt/C and a negative influence on their stability.