MSc dissertation: Use of niobia as support in catalysts for the hydrogenation of furfural to furfuryl alcohol in liquid phase

The metal loading of the Ni catalyst was varied between 5 and 20 wt%. Base metals (Ni and Cu) were reduced under H2 flow and noble metals (Pd and Ru) were reduced using formaldehyde in their preparation. The reactions were conducted in a slurry Parr reactor under H2 pressure of 5 MPa, temperature of 150°C and 2-propanol was used as solvent.

In order to correlate the obtained results with the physicochemical properties of the materials, support and catalysts were characterized by N2 physisorption, EDS, XRD, TPR, TPD-NH3 and XPS. The calcination temperature of the support allowed the synthesis of non-crystalline materials with high specific surface area. There are indications that the reduction by formaldehyde prevented particle aggregation in noble metals, while the exposure to H2 flow allowed a high degree of reduction for base metals.

The increase of metal loading on Ni catalysts intensified pore blockage, mainly in the solid 15% Ni/Nb2O5, but in general it contributed to an increase in catalytic activity. Ni and Cu catalysts showed high selectivity to furfuryl alcohol, however the solid Cu/Nb2O5 presented a furfural conversion of only 15% due to the loss of active sites on the surface. Pd and Ru catalysts provided high initial reaction rates and enabled complete furfural conversion, but while Pd/Nb2O5 showed increasing selectivity to tetrahydrofurfuryl alcohol, Ru/Nb2O5 enabled the formation of furfuryl alcohol in the first 2 hours of reaction.

The presence of acid sites on the catalytic surface favored the formation of by-products, especially difurfuryl ether.