CO hydrogenation towards higher alcohols catalysed on SiO2-grafted and zeolite-entrapped Ru, Co and RuCo bimetallic clusters: Their EXAFS and FTIR characterization and catalytic performances

Some Ru and Co carbonyl clusters in zeolite pores such as Ru3(CO)12/NaY, [HRu6(CO)18]−/NaY, [Ru6(CO)18]2−/NaX, Co4(CO)12/NaY and Co6(CO)16/NaY were prepared by the ship-in-bottle technique, and characterized by FTIR and EXAFS. The RuCo bimetallic carbonyl cluster was prepared by reductive carbonylation of the oxidized RuCo/NaY, which provides the proposed assignment to [HRUCo3(CO)12]/NaY. The tailored Ru, RuCo and Co catalysts were prepared by H2 reduction from the precursors, e.g. Ru, RuCo bimetallic and Co carbonyl clusters impregnated on SiO2 and entrapped in NaY and NaX zeolites. The RuCo bimetallic carbonyl cluster-derived catalysts showed substantially higher activities and selectivities for oxygenates such as C1–C5 alcohols in CO hydrogenation (CO/H2 = 0.33-1.0, 5 bar, 519–543 K). By contrast, hydrocarbons such as methane were preferentially obtained on the catalysts prepared from Ru6, Ru3 and Co4 carbonyl clusters and provided lower CO conversion and poor selectivities for oxygenates. The RuCo bimetals are proposed to be associated with the selective formation of higher alcohols in CO hydrogenation.