Catalytic Performance Of Ni-based Composite Metal Oxides For Hydrodeoxidation Of Methyl Laurate

With the rapid development of global economy,the demand for energy is increasing.While the limited non-renewable fossil energy is gradually depleted,it has also caused serious environmental problems.Therefore,the development of clean and renewable energy is an urgent problem to be solved.In recent years,biodiesel,as a substitute for traditional fossil fuels,has attracted wide attention due to its excellent environmental protection and renewable properties.However,the first generation of biodiesel（FAME）limited its large-scale utilization due to high oxygen content.Therefore,it is necessary to upgrade the first-generation biodiesel by hydrodeoxygenation reaction.In this paper,methyl laurate was used as a model compound to study the hydrodeoxygenation reaction of FAME,and we constructed three high-selectivity Ni-based catalysts,which can effectively control the hydrodeoxygenation pathway of methyl laurate.The main research contents and results are as follows.（1）Ni/CeO₂-TiO₂catalyst was prepared for the catalytic conversion of methyl laurate to C₁₁alkane by hydrodeoxygenation.The physicochemical properties of the catalysts were investigated by XRD,Raman,NH₃-TPD,H₂-TPR,XPS,etc.The experimental results showed that under the optimal conditions of reaction temperature was 300 ^oC,reaction time was 4 h,hydrogen pressure was 2.5 MPa,Ce/Ti molar ratio was 1:1 and Ni loading was 10 wt.%.The conversion of methyl laurate was 100%and the selectivity of C₁₁alkane was 96%.This was due to the oxygen defect site Ce³⁺and the oxyphilic site Ti cations could have strong interaction with carbonyl oxygen in the raw materials,thereby reducing the energy required for decarbonylation/carboxylation,and increasing the reaction activity.（2）Ni/SnO₂-ZrO₂catalyst was prepared for the catalytic conversion of methyl laurate to lauryl alcohol by hydrodeoxygenation.The physicochemical properties of the catalysts were investigated by NH₃-TPD,Py-IR,H₂-TPR,XPS,etc.The experimental results showed that under the conditions of reaction time was 6 h,reaction temperature was 300 ^oC,hydrogen pressure was 3.5 MPa,Ni loading was 10wt.%and Sn/Zr molar ratio was 2:1,the conversion of methyl laurate and selectivity of lauryl alcohol were 100%and 93%,respectively.This was due to the doping of ZrO₂could significantly increase the oxygen vacancies content on the surface of the support.The electrons in the oxygen vacancies can be transferred from the support to metal Ni⁰,which could increase the electron density of the metal Ni⁰.The negatively charged metal Ni⁰promoted the heterolysis of hydrogen,and the generatedand H^δ+and H^δ-selectively adsorption and activation the C=O bond of methyl laurate to fatty alcohols.（3）NiMo/TiO₂-SiO₂catalyst was prepared for direct hydrodeoxygenation.of methyl laurate to C₁₂alkanes.The physicochemical properties of the catalyst were investigated by XRD,H₂-TPR,XPS,NH₃-TPD,Py-IR,etc.The experimental results showed that under the conditions of reaction time was 4 h,reaction temperature was300℃,hydrogen pressure was 2.5 MPa,Ni loading was 10 wt.%,Mo loading was 3wt.%and Ti/Si molar ratio was 1:1,the conversion of methyl laurate was 100%and the selectivity of C₁₂alkane was 92%.This was due to the introduction of oxyphilic modifier Mo could decrease the strong adsorption of electron-rich Ni to the carbonyl C and H,accelerate the migration and dissociation of H on the surface of the active center,which was conducive to adsorb and activate the C=O bonds to give the hydrodeoxygenation products.