Design of efficient supported Pd-Co catalysts for selective hydrogenation of acetylene

Abstract

The research is devoted to the study of active component formation in the novel Pd-Co catalysts supported on carbon material Sibunit. It was shown that 0.5 %Pd–0.5 %Co/C samples exhibit high ethylene yield in the acetylene hydrogenation process due to the presence of fcc PdxCo(1-x) particles. According to in situ XRD-TPR analysis, solid solution formation begins during the reduction of samples in H2 at T ≥ 500 °C. Using the EXAFS, XRD and EDX it was established that H2-treatment at 500 °C leads to the formation of ∼Pd0.6Co0.4 particles and an increase in the reduction temperature to 600 and 700 °C is accompanied by the enrichment of the Pd-Co-phase with cobalt to ∼Pd0.5Co0.5 and ∼Pd0.45Co0.55 compositions, respectively. The ethylene yield on Pd-Co/C catalysts reduced at 500, 600 and 700 °C is 56, 66 and 68 %, respectively, which significantly exceeds the ethylene quantity obtained on monometallic Pd/C samples (∼52 %). It is assumed that the excellent selectivity of Pd-Co/C samples treated in H2 at 600 and 700 °C is due to an increase in the amount of palladium atoms surrounded by cobalt and a change in the palladium electronic state (XPS).