| With the rapid development of human society,intensive use of fuels results in the energy and environmental issues.It becomes a major development trend to find more environmentally friendly and renewable new energy sources.Biomass energy is recognized as an ideal substitute energy since it is renewable and has the feature of CO2 zero emissions.In recent years,bio-oil,a liquid fuel,could be obtained from biomass by rapid pyrolysis technology,which has received widespread attention.While,bio-oil cannot be directly used as fuel because of its high oxygen content,high water content,low calorific value and poor stability.It is necessary to upgrade bio-oil to fuel by some chemical and physical methods.In-situ hydrodeoxygenation is one of the efficient method for upgrading bio-oil,which has the advantage of simple operation,high safety and low cost with no additional hydrogen supply.In this research,the in-situ hydrodeoxygenation of phenol a model compound of bio-oil,has been studied over the Ni-Cu-Co/?-Al2O3 catalyst.The main contents and results as follows:(1)A series of Ni-Cu-Co/?-Al2O3 were prepared by the impregnation method.The structure,specific surface area,acidity and disperse of the catalysts were characterized by XRD,temperature programmed reduction(H2-TPR),N2 adsorption-desorption,scanning electron microscopy,transmission electron microscopy and gas chromatography.It shows that the Ni-Cu-Co/?-Al2O3 catalyst prepared by the impregnation method is uniformly dispersed,and its specific surface area is 78 m2/g.The acidity of the ?-Al2O3 has an positive effect on the hydrodeoxygenation reaction of phenol.(2)The reaction of hydrogenation of phenol to cyclohexane over Ni-Cu-Co/?-Al2O3 catalyst was studied.The catalyst composition,reaction time,reaction temperature,reaction pressure and solvent type for the direct hydrogenation of phenol over the Ni-Cu-Co/?-Al2O3 catalyst were investigated.The results show that the conversion of phenol can reach 100%and the selectivity of cyclohexane is over 99%under the reaction time of 4 h,the reaction temperature of 220? and the pressure of 4 MPa H2.(3)The reaction of in-situ hydrodeoxygenation of phenol to cyclohexane over the bifunctional Ni-Cu-Co/?-Al2O3 catalyst was also studied.It was found that the conversion of phenol can reach more than 99%,and the selectivity of cyclohexane is about 98%under the condition of 240?,4 MPa,the reaction time of 4 h,and the ratio of water:methanol:phenol raw material of 30:15:3.At the same time,the effects of different hydrogen donors on the in situ hydrodeoxygenation of phenol were also investigated.The results showed the order of the conversion of phenol for the in-situ hydrodeoxygenation is methanol>ethanol>propanol>acetic acid>formic acid.In terms of catalyst stability,the selectivity of cyclohexane can still be maintained above 95%after 10 times of use of the catalyst.The characterization results of XRD and ICP also confirmed that the catalyst has excellent structural stability.(4)The reaction mechanism of Ni-Cu-Co/?-Al2O3 catalyst on in-situ hydrodeoxygenation of bio-oil model compound phenol to cyclohexane was discussed.The Ni-Cu-Co/?-Al2O3 catalyst showed a bifunctional catalytic performance in a methanol-water-phenol system.Methanol and water are first reformed on Ni-Cu-Co/?-Al2O3 catalyst to produce hydrogen,which reacted with phenol to form cyclohexanone.Subsequently,cyclohexanone is further hydrogenated to rapidly form cyclohexanol.The cyclohexanol are then dehydrated and hydrogenated to form cyclohexane.Compared with the hydrogenation of phenol,the in-situ hydrogenation reaction due to the participation of water solvent prevents the side reaction of phenol to benzene and C12.The addition of Cu promoter helps to increase the hydrogen production rate in the in-situ hydrogenation of phenol;the addition of Co promotes the dehydration reaction of cyclohexanol and improves the selectivity of cyclohexane. |
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