Preparation Of Nickel Phosphides And Borides And Their Catalytic Performance In Aqueous Phenol Hydrodeoxygenation

The consumption of traditional energy was huge,leading to the environmental pollution and massive CO₂ emission.Biomass,a new renewable energy source,is the ideal alternative energy.However,the crude bio-oil has a high oxygen content,bringing about a series of problems,such as low heat value,poor stability,high viscosity and immiscible with petroleum fraction.As a result,the crude bio-oil was impossible to be used as the engine fuel.Therefore,it is necessary to upgrade the crude bio-oil by hydrodeoxygenation（HDO）.The core technology is the development of HDO catalyst with low price and high performance.In this paper,the bulk Ni₃P and Ni₃B catalysts were prepared by liquid phase reduction method.The Ni₃P catalyst was modified by addition of transition metal（Co,W,Cu and Fe）and non-metal（B）.Their catalytic performance was studied in aqueous-phase HDO of phenol.Moreover,the catalysts were characterized by means of XRD,N₂-adsorption-desorption,SEM and TEM to analyze the relationship between the structure and performance.The effects of the preparation conditions（pH value,nickel source and Ni/P molar ratio）and the promoter（species and contents）on the crystal phase and catalytic performance of the Ni₃P catalyst were investigated.The amorphous Ni-P was prepared by liquid reduction with pH value of 5.5,using Ni Cl₂ as the nickel source at Ni/P molar ratio of 1/5.After thermal treated in H₂ at 400℃for 2 h,the amorphous Ni-P was transformed into Ni₃P.The increase of P content decreased the mean particle size of the Ni₃P catalyst,leading to the enhanced hydrogenation activity.Under the optimal conditions,the effect of metal promoter（Co,W,Cu and Fe）on the crystal phase and catalytic performance of Ni₃P was investigated.The addition of second metal did not influence the formation of Ni₃P.Trace content of Cu Ni alloy was formed after addition of Cu.Their catalytic performance was studied in aqueous-phase HDO of phenol at 4 MPa H₂and 200℃.Among the metal additives,the Fe（0.3）-Ni₃P exhibited the best catalytic performance.NaBH₄,an efficient reductant in liquid phase reduction,can be used as the alternative of Na H₂PO₂.The addition of NaBH₄ was added by two programs.In program 1,NaBH₄ and Ni Cl₂ were added dropwise to the solution containing Na H₂PO₂ at 90℃.The main crystal phase of the obtained catalyst was Ni₂P.In program 2,NaBH₄ was added into the mixed solution of Ni Cl₂ and Na H₂PO₂ at 90℃.The main crystal phase was a mixture of Ni₃P and Ni.The bulk Ni₃B catalyst was prepared by liquid phase reduction method.The effects of Ni/B molar ratio,thermal treatment（atmosphere and temperature）,and acid etching on the crystal phase and catalytic performance of the catalyst were investigated.A mixture of Ni₃B and Ni was obtained after thermal treated in N₂ at 400°C for 1 h with Ni/B molar ratio of 1/6.The Ni₃B crystal phase was transformed into Ni with the increasing temperature（>400°C）.After etched in formic acid for 0.5-2 h,pure Ni₃B crystal phase was obtained.As the etching time increased to 4 and 8 h,the Ni₃B crystal phase gradually disappeared.At 4 MPa H₂ and100°C,the catalytic performance decreased in the order:Ni₃B>Ni-Ni₃B>Ni-B.The crystal phased of Ni₃B and Ni-Ni₃B was unchanged,indicating they were stable under the reaction conditions.However,the amorphous Ni-B was partly crystallized after the reaction.At high temperature（200°C）,all the three catalysts were unstable.The crystal phase was transformed into metallic Ni after the reaction.