Hydrogenation Of Phenol Over Supported Nickel Phosphide Catalysts

Biomass energy as a kind of economic sustainable,environmental friendly and efficient renewable clean energy,has been widespread paid.The bio-oil obtained from rapid pyrolysis of biomass is considered to be the most promising liquid fuel.However,some disadvantages of bio-oil such as low heat value,poor stability,high water content and high acidity limit its application.So upgrading process of bio-oil is needed to improve its qualities before using as high quality fuels.Catalytic hydrodeoxygenation process is one of the common methods of for bio-oil upgrading to remove oxygen compounds in the bio-oil.During this process,catalysts play an important role.Nickel phosphide?Ni₂P?as a new type of hydrodeoxygenation catalyst,have caused greatly attention because of its unique physical and chemical properties.However,unsupported nickel phosphide catalyst faces some problems such as easy agglomeration,large particle size and so on,which cause its low catalytic activity.Therefore,in this paper,supported nickel phosphide catalysts were prepared and characterized by XRD,TEM,BET methods.And the hydrodeoxygenation performance of the catalysts was investigated using phenol as the model compound of bio-oil.First,a series of Ni₂P/ZrO₂ catalysts with different loading were obtained by impregnation-thermal decomposition method.The characterization indicates that with the increase of the nickel loading,the particle size of nickel phosphide catalyst increases slightly,and the specific surface area or pore volume decrease gradually.The catalyst with 10% nickel loading?10%-Ni₂P/ZrO₂?exhibited the best activity under the same reaction conditions using phenol as bio-oil model compound.Compared with the unsupported Ni₂ P catalyst,we found that after loading,the specific surface area of the catalyst is obviously increased and the dispersibility is improved,more active sites are hence exposed and the activity of the catalyst is improved.The results of activity evaluation showes that the conversion of phenol on the supported 10%-Ni₂P/ZrO₂ catalyst can reach 58.7% at 250 ? for 2 h,while the conversion of phenol on the unsupported Ni₂ P catalyst is only 14.1%.In addition,with the increase of reaction temperature and reaction time,the conversion of phenol and the selectivity of cyclohexane increased.When the reaction time was 2 h and the reaction temperature was 300 ?,the conversion of phenol reached 90.8% and the selectivity of cyclohexane reached 91.7%.ZrO₂-SiO₂ composite supporter was prepared by precipitation method in order to further improve the specific surface area,and Ni₂P/ZrO₂-SiO₂ catalysts were prepared by impregnation-thermal decomposition method.From the analysis of characterization,it is found that the Ni₂P/ZrO₂-Si O₂ catalyst significantly increased the specific surface area and the pore volume in comparison with the Ni₂P/ZrO₂ catalyst.The addition of silicon further improved the dispersibility of the active component Ni₂ P and the activity of the catalyst.The conversion of Ni₂P/ZrO₂-SiO₂?1:1?and Ni₂P/ZrO₂ to phenol was 60.3% and 37.1% at 250 ? for 2 h.Using Ni₂P/Zr O₂-SiO₂?1:1?at reaction temperature from 220 to 300 ?,the phenol conversion rate increased from 26.9% to 100%,and the selectivity of cyclohexane increased from 5% to 91.1%.With the reaction time increasing from 2 h to 5 h,the conversion of phenol increased from 58.7% to 100%,and the selectivity of cyclohexane increased from 29.1% to 100%.