Gas-phase hydrogenation of furfural to furfuryl alcohol over Cu/ZnO catalysts

• CuZnO catalysts are active in hydrogenation of furfural to furfuryl alcohol.
• The Cu–ZnO interaction is higher for lower copper loading.
• Long term stability is improved in comparison with copper chromite.
• Selectivity to furfuryl alcohol is higher at low H2 feed rates.

A series of Cu/ZnO catalysts (Cu:Zn molar ratio = 0.2–6.0), prepared by coprecipitation and subsequent calcination and reduction, has been characterized and evaluated in the gas-phase hydrogenation of furfural (FUR). All catalysts exhibit high stability, with conversion values higher than 55 mol% after 5 h of time-on-stream (TOS) at 463 K with a H2:FUR molar ratio of 11.5 and a WHSV of 1.5 h−1. The best catalytic performance is found for the catalyst with the lowest copper loading, which maintains a conversion of 93 mol% after 5 h of TOS, with a selectivity of 82 mol% towards furfuryl alcohol. After 24 h of TOS, this catalyst still shows a furfuryl alcohol yield of 60 mol%. The strong metal-support interactions in the catalysts with lower copper contents explain their higher stabilities. In all cases, the carbon percentages in the used catalysts are lower than 1.5%, thus indicating that carbonaceous deposits could be the cause of the slight deactivation of Cu/ZnO catalysts, together with metal sintering in catalysts with higher copper contents.

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