Application of Prussian Blue Analogue‐Derived Mn−Co Catalysts in the Hydrogenation of CO to Higher Alcohols

Abstract

AbstractMnxCo3‐x[Co(CN)6]2 Prussian blue analogues were synthesized with Mn : Co ratios in the range from 7 : 10 to 1 : 11 and pyrolyzed at 600 °C to obtain a highly nitrogen‐ and oxygen‐functionalized carbon matrix with embedded reduced Mn and Co species. These catalyst precursors were applied in the CO hydrogenation to higher alcohols at 260 °C and a pressure of 60 bar using a H2/CO ratio of 1. Metallic Co0 formed during pyrolysis was partially transformed into Co2C under reaction conditions. With increasing Co content CO conversion increased up to 10.6 % reaching a total alcohol selectivity of 19 %. Gas chromatograms revealed the expected formation of primary short‐chain alcohols, but also of secondary alcohols, acetic acid and propionaldehyde indicating olefin hydration, carbonylation and hydroformylation as reaction pathways, respectively. The obtained hydrocarbon fractions had a very high olefinicity, which is beneficial for both olefin hydration to secondary alcohols catalyzed by adsorbed carboxylic acids and for hydroformylation. Whereas the carbide‐based reaction pathway and the reductive hydroformylation are assumed to occur at the Co2C/Co0 interface, carbonylation is presumably catalyzed by an additional Co‐based active site. Thus, a unique class of multifunctional catalysts was obtained with highly promising properties bridging the gap between heterogeneous and homogeneous catalysis.