Preparation Of Ni-based Catalyst And The Hydrogenation Performance Of Oils

The contradiction of the rapid development of society and energy supply,and environmental problems caused by the harmful gases releasing from fossil fuels are becoming more and more serious.On the other hand,the catering industry is growing flourish.Simultaneously,the output of waste cooking oil is increasing unprecedentedly.If this phenomenon can’t be properly controlled and processed,it will bring a huge threat to the food safety and environment.It has become an urgent social problem to correct disposal and effective utilization of waste cooking oil.If the waste cooking oil can be utilized as resource and turned into a treasure,which can not only greatly alleviate the pressure of the sustained growth in energy demand but also change the distorted trend of the waste cooking oil returning to the table,and achieve good economic benefits and social benefits.It has attracted wide attention to obtain biodiesel from waste cooking oil by energy conversion technology（hydrodeoxygenation（HDO）technology）.In this paper,mesoporous Ni-based catalysts were prepared by impregnation method.H₂-TPR,XRD,BET,TEM,SEM,H₂-TPD,and In-situ XPS were used to study the physicochemical properties of the prepared catalysts.The catalytic performances of each catalyst were evaluated by ethyl acetate and methyl laurate catalytic HDO reaction.Some main conclusions were drawn as follows:1.The catalytic HDO performance of the prepared N₂₀A_xK catalysts is related to the adsorption and activation performance for H₂molecules,as well as the dispersion of matal Ni active components.N₂₀A₅K catalyst with Al dosage of 5%of shows the best H₂adsorption property and Ni dispersion.N₂₀A₅K catalys shows the best H₂adsorption property and Ni dispersion.N₂₀A₅K catalyst presents superior catalytic HDO performance.At 300°C and atmospheric pressure,the conversion of ethyl acetate and ethane selectivity of N₂₀A₅K catalyst are 99.3%and 97.4%,respectively.Besides,the N₂₀A₅K catalyst exhibits good stability.2.All the prepared Ni-based catalysts have mesoporous structure and large specific surface area,and the Ni,Cu,Fe,Zn,Mn,and Co species were highly dispersed on the Ni₅X₅/γ-Al₂O₃catalyst surface.The introduction of X transition metal has a significant influence on the reducibility of Ni species and enormously improve the low temperature"absorption-desorption"performance of Ni-based catalysts to H₂,due to the interaction between X and Ni species.All the studied catalysts preferentially catalyzes the decarbonylation/carboxyl（DCO）reaction in the deoxygenation of methyl laurate,and the main deoxygenation products are C₁₁alkane.At the ratio of H₂/Oil,the space velocity（SV）,H₂pressure（P）,and reaction temperature are 500N,1.5h^-1,2MPa and 400°?,respectively,the Ni₅Cu₅/γ-Al₂O₃catalyst shows the best methyl laurate DCO properties,and methyl laurate conversion and C₁₁alkane selectivity can reach99.8 and 87.3%,respectively.3.The physicochemical properties and catalytic HDO performance of Ni_xCu_y/γ-Al₂O₃catalyst were obviously influenced by Cu content.The Ni_xCu_yO/γ-Al₂O₃precursors can be reduced by H₂at 420°?to Ni⁰,Cu⁰,and Ni Cu alloy active species.Formed Ni Cu alloy can effectively promote the electronic effect between Ni and Cu,and enhance the adsorption and activation abilities of the corresponding catalyst to the reactant molecules.The Ni active sites preferentially catalyzes the decarbonylation/carboxyl（DCO）reaction in the deoxygenation of methyl laurate,while the HDO pathway is predominant on the Cu active sites.The deoxygenation pathway obviously changes from DCO to HDO at the mole ratio of Ni/Cu lower than 3/7,and the main deoxygenation products change from C₁₁to C₁₂alkane.At the ratio of H₂/Oil,the space velocity（SV）,H₂pressure（P）,and reaction temperature are 500N,1.5h^-1,2MPa and 400°?,respectively,the Ni₃Cu₇/γ-Al₂O₃catalyst shows the best methyl laurate DCO properties,and methyl laurate conversion and C₁₁alkane selectivity which is the main deoxygenation products can reach 99.8 and 87.3%,respectively.Moreover,Ni₃Cu₇/γ-Al₂O₃catalyst also exhibits good stability.