The influence of metal selection on catalyst activity for the liquid phase hydrogenation of furfural to furfuryl alcohol

In this work the replacement of toxic chromium containing catalysts for the selective hydrogenation of furfural to furfuryl alcohol was investigated. The initial focus was on the synthesis of monometallic catalysts by wet impregnation and concentrated on the employment of metals such as platinum, palladium, copper and nickel. Experiments were conducted using ethanol as the solvent which was found to have a negative effect on the selectivity to the desired product, furfuryl alcohol, with high quantities of 2-Furaldehyde diethyl acetal and difurfuryl ether formed. Consequently, toluene was selected as an alternative solvent facilitating selectivity to furfuryl alcohol only. It was found that platinum was the most promising metal of those studied as it displayed higher selectivity to furfuryl alcohol and was subsequently employed for the synthesis of bimetallic catalysts. The bimetallic catalysts were synthesised by surface reactions using a variety of promoter metals selected according on their electronegativity. It was found that, while the selectivity of all catalysts to furfuryl alcohol was close to 100%, the conversion was influenced significantly by the second metal and followed the order tin > molybdenum > manganese > barium > iron > nickel. The purpose of the research was to produce an active catalyst for the liquid phase hydrogenation under suitable industrial conditions with the results presented here conducted at 100 °C and 20 bar hydrogen pressure. Furfural conversion of 47% and close to 100% selectivity to furfuryl alcohol was achieved using a 0.6%Pt0.4%Sn/SiO₂ catalyst.