Catalytic hydrodeoxygenation of simulated phenolic bio-oil to cycloalkanes and aromatic hydrocarbons over bifunctional metal/acid catalysts of Ni/HBeta, Fe/HBeta and NiFe/HBeta

Bifunctional metal/acid catalysts of 5 wt% Ni/HBeta, 5 wt% Fe/HBeta, 2.5 wt% Ni-2.5 wt% Fe/HBeta (NiFe-5/HBeta) and 5 wt% Ni-5 wt% Fe/HBeta (NiFe-10/HBeta) were used for hydrodeoxygenation (HDO) of a simulated phenolic bio-oil consisting of phenol (50 wt%), o-cresol (25 wt%) and guaiacol (25 wt%). Nickel and iron metals were supported on hydrogen form Beta zeolite (HBeta) under similar ion-exchange conditions. BET surface area and acid sites density of Ni/HBeta, Fe/HBeta, NiFe-5/HBeta and NiFe-10/HBeta were 463, 445, 455, 417 m²/g and 0.53, 0.48, 0.50, 0.38 mmol/g, respectively. Cycloalkanes (21.39 wt%) and aromatic hydrocarbons (20.21 wt%) were the dominant hydrocarbons obtained over monometallic catalysts of Ni/HBeta and Fe/HBeta through reactions of hydrogenation and hydrogenolysis, respectively. It was revealed that both hydrogenation and hydrogenolysis mechanisms were effectively proceeded over the bimetallic catalyst of NiFe/HBeta which showed enhanced HDO efficiency compared to monometallic catalysts of Ni/HBeta and Fe/HBeta due to the synergistic effect between the two metals. The effect of reaction temperature on HDO efficiency of NiFe-10/HBeta catalyst was investigated at 220, 260, 300 and 340 °C. Maximum catalytic activity and hydrocarbons selectivity was observed at 300 °C. Replacement of water with methanol as solvent in HDO of the simulated phenolic bio-oil over NiFe-10/HBeta remarkably reduced the selectivity towards hydrocarbons.