Fabrication Of Highly Efficient Ni/SiO₂ Catalysts For Liquid-Phase Hydrodeoxygenation Of Phenol

Due to the reduction in the fossil fuel reserves and environmental apprehensions all around the world,the society is shifting towards renewable energy resources.Biomass is considered as one of the cheaper available resource.Pyrolysis of the biomass produces bio-oil.The catalytic upgrading of bio-oil undergoes to production of liquid fuels.Catalytic hydrodeoxygenation(HDO)of lignin derived phenolic compounds is one of the most promising routes for the production of liquid fuels.A bifunctional Ni/SiO₂ catalyst having Nickel phyllosilicate(Ni-PS)was synthesized by Ammonia evaporation(AE)method.The catalyst was then reduced at different temperature.The catalyst is then identified by different characterization techniques.The formation of Nickel phyllosilicate on bifunctional Ni/SiO₂ catalyst was confirmed by X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and Transmission Electron Microscope(TEM)characterization techniques.TEM also showed that Ni particles were well dispersed on Ni/SiO₂catalyst.Temperature programmed reduction(TPR)results shown that Ni/SiO₂ catalyst fabricated by AE method has a strong metal-support interaction.The superior performance of Ni/SiO₂ catalyst in phenol HDO is affected by the reduction temperature,and the best cyclohexane yield can be achieved on the catalyst reduced at 350-400 ^oC.The amount of nickel phyllosilicate can be greatly affected by the reduction temperature.The acid sites originated from the nickel phyllosilicate could enhance the dehydration of cyclohexanol,resulting in a higher selectivity of cyclohexane.Hence the formation of metallic Ni can benefit the hydrogenation of aromatic ring and the intermediate product cyclohexene.Therefore,catalytic performance of Ni/SiO₂ catalyst is remarkably affected by reduction temperature.Further studies have shown that phenol HDO is subjected to an initial hydrogenation to produce cyclohexanone,which is rapidly hydrogenated to produce cyclohexanol.It is then dehydrated to cyclohexene and cyclohexene is rapidly hydrogenated to cyclohexane.The dehydration of cyclohexanol should be the rate-determining step of phenol HDO on Ni/SiO₂ catalyst.