SYNTHESIS AND CHARACTERIZATION OF NICKEL BASED CATALYSTS FOR HYDROGENATION OF FURFURAL TO FURFURYL ALCOHOL

Abstract

Monometallic Ni-alumina catalysts, containing different loadings of nickel, were prepared by wetness impregnation method and tested for the liquid phase hydrogenation of furfural to furfuryl alcohol. The physiochemical properties of the catalysts was characterized by various techniques such as X-ray diffraction (XRD), temperature programmed reduction (TPR), and scanning electron microscopy (SEM). Surface area of alumina was 152.6 m2/g. It was found that the surface area of the impregnated catalysts was reduced significantly and it was in the range of 66.4 m2/g to 80.2 m2/g. Initially, the surface area was increased with metal loading up to 10 wt.% probably due to the dispersion effect of smaller particles of Ni oxides. Surface area was decreased with further increase in metal loading up to 20 wt.% probably due to the agglomeration of the catalyst as big lumps. The XRD results confirmed the formation of nickel oxide particles on the catalyst along with metal ion and the broader peaks showed the indication of typical amorphous structure of the nickel catalyst supported on alumina. The TPR results revealed that with increasing nickel content the reduction temperature is marginally shifted towards lower temperature. The catalytic tests were done in the batch 250 ml Teflon coated stainless steel batch reactor. Hydrogenation of furfural was carried at a temperature of 160°C and hydrogen pressure of 3.5 MPa. The constant amount of catalyst (2 g) was used in every experiment. Total 80 ml of reaction mixture was taken. Furfural to ethanol volume ratio was fixed at 1:4. The experimental data were collected after a reaction time of 5 h. The effect of support as well as metal loading on liquid phase reaction was studied. Among all the catalysts tested, Ni catalyst with metal loading of 5 wt.% supported on alumina showed highest activity (98.4%) with the selectivity to furfural alcohol of 88.4% after a reaction time of 2h. These results can be inferred from the characterization results of the catalysts which showed the decrease in catalytic properties of catalyst with increase in metal loading. Highest activity and selectivity in hydrogenation reaction after a reaction time of 2h also validates the reaction pathway of furfural hydrogenation which explains that excess hydrogenation of furfural lead to the formation of tetrahydrofurfuryl alcohol at the expense of furfural alcohol.