Selective hydrogenation of furfural over supported nickel and nickel phosphide catalysts

The Ni/Al 2 O 3 was highly active and selective for the hydrogenation of furfural to tetrahydrofurfuryl alcohol (THFA) due to the strong adsorption of aldehyde group and furan ring on Ni, while the Ni 2 P/MgO-Al 2 O 3 was fairly active and highly selective to furfuryl alcohol (FA) for the reaction owing to the relatively stronger adsorption of aldehyde group than furan ring on Ni 2 P although the two groups were much weakly adsorbed on Ni 2 P. In addition, the surface acidity promoted the selectivity to THFA on Ni while the surface basicity favored the selectivity to FA on Ni 2 P. • Ni catalysts were highly active for the hydrogenation of C C and C O in furfural . • Ni 2 P catalysts were more active for the hydrogenation of C O than for that of C C. • Ni/Al 2 O 3 was selective for the furfural hydrogenation to tetrahydrofurfuryl alcohol. • Ni 2 P/MgO-Al 2 O 3 was selective for the hydrogenation of furfural to furfuryl alcohol. • Surface acidity/basicity affected the adsorption of C C and C O on Ni sites. Supported Ni (60 wt% Ni) catalysts were prepared and phosphided into corresponding Ni 2 P catalysts. They were used for the hydrogenation of furfural as well as for the probe reactions (the hydrogenation of furan and propanal). The results demonstrated that the acidic support promoted the adsorption and hydrogenation of furan ring and aldehyde group over the nickel sites while the basic support played the opposite role. The IR spectra demonstrated that the aldehyde group was more easily hydrogenated than the furan ring at room temperature, implying the sequential hydrogenation of furfural to furfuryl alcohol (FA) and then to tetrahydrofurfuryl alcohol (THFA) over Ni. The microcalorimetric studies revealed that both the aldehyde group and furan ring were strongly adsorbed on Ni so that the Ni catalysts were highly active to hydrogenate the two groups, i.e., the Ni catalysts favored the formation of THFA. On the other side, although the adsorption heats of aldehyde group were much lower on Ni 2 P than on Ni, the adsorption heats were significantly higher for aldehyde group than for furan ring on Ni 2 P, implying the high selectivity to FA on Ni 2 P.