Understanding hydrogen pressure control of furfural hydrogenation selectivity on a Pd(111) model catalyst

We investigate the postulate that hydrogen pressure influences the furfural hydrogenation selectivity on palladium to form decarbonylation products at low hydrogen pressures, but 2-methyl furan at higher pressures. This change is caused by co-adsorbed hydrogen changing the orientation of adsorbed furfural; low hydrogen coverages favor flat-lying furfural, higher coverages form tilted species. This was tested for hydrogenation of furfural on a Pd(1 11) single crystal. The product distribution agreed with the postulate, with 100% selectivity to furan and tetrahydrofuran for low hydrogen pressures, with 2-methyl furan increasing with hydrogen pressure. The origin of the effect is explored using reflection-absorption infra -red spectroscopy. This showed that co-adsorbed hydrogen influenced the orientation in a way predicted by theory. It was also found that other co-adsorbates displayed similar effects implying that a range of molecules in the reaction mixture could have significant effects on the furfural selectivity.(c) 2023 Elsevier Inc. All rights reserved.

Automated summary

We investigated the influence of hydrogen pressure on the selectivity of furfural hydrogenation on palladium. Our findings show that at low hydrogen pressures, decarbonylation products are formed, while at higher pressures, 2-methyl furan is produced. This change in selectivity is attributed to the effect of co-adsorbed hydrogen on the orientation of furfural adsorbed on the surface. The results obtained from studying the hydrogenation of furfural on a Pd(111) single crystal support this postulate.