Tuning Of Multifunctional Surface-Interface Structure For Ni Catalysts And Their Catalytic Hydrodeoxygenation Performance Of Lignin Derived Model Molecules

The environmental issues exposed in the consumption of fossil resources and the limited reserves and non-renewable features of fossil resources urge us to find alternatives to substitute fossil resources.Biomass,possessing the advantages of renewable,huge reserves,carbon neutralization in the utilization process,is a potential candidate to replace fossil resources.As an important component of biomass,lignocellulose has attracted extensive attention.Lignin is a kind of aromatic polymer within lignocellulose.Due to its special aromatic structure,the direct conversion and utilization of lignin are difficult.Usually,lignin is first depolymerized by pyrolysis to generate bio-oils.The obtained bio-oils contain a large number of aromatic phenols,aldehydes,acids,esters,and other components thus bio-oils exhibit high oxygen content and can not be used directly as transportation fuels.Therefore,the catalytic upgrading of bio-oils is needed to generate fuel or high value-added chemicals,which can be achieved by catalytic hydrodeoxygenation（HDO）.The main purpose of catalytic HDO process is the removal of methoxy,hydroxyl,and other oxygen-containing groups connected to the aromatic ring,due to component complexity,anisole and guaiacol are widely used as model molecules of lignin derivatives in the study of catalytic HDO of lignin derivatives.The HDO performance of supported catalysts mainly depends on the surface/interface structure and properties of the catalyst.The catalytic HDO process involves multiple continuous or parallel reactions,so the catalysts should have multiple functions to control the product selectivity through catalyzing different reactions.The catalytic activity of metal sites,acid sites,and defective sites,and the cooperation between metal and acid sites and/or defective sites are the origin of the HDO ability of supported transition metal catalysts.Through the fine balance of active sites,effective supported metal catalysts were developed for the selective generation of target deoxygenated product cyclohexane in the HDO of lignin-derived compounds.Based on the understanding of the origin of HDO catalytic ability of supported transition metal catalysts,monometallic and bimetallic Ni-based catalysts were constructed by fine manipulation of the surface/interface structure and properties of supported catalysts.In the HDO process of lignin-derived model molecules anisole and guaiacol,the cooperation among metal sites,acid sites,and defective sites is realized to improve the catalytic HDO performance of the supported catalyst and produce cyclohexane with high yields.The main work is as follows:1.Construction of multiple active sites on the surface and interface of Al-Zr oxide solid solution supported nickel catalyst and its HDO performance of anisole.Hexadecyl trimethyl ammonium bromide（CTAB）was used as a structural additive to realize the uniform coprecipitation of Ni²⁺,Al³⁺,and Zr⁴⁺to synthesize catalyst precursors.Al-Zr oxide solid solution supported Ni-based catalyst was constructed by calcination and reduction.The introduction of Al enhances the metal-support interaction and favors the formation of the interfacial Ni^δ+species.Meanwhile,it is conducive to the generation of new types of oxygen vacancies and acid sites in the catalyst;On the one hand,Ni^δ+species and oxygen vacancies can promote the direct removal of methoxy group of anisole to produce benzene,and benzene can produce cyclohexane after hydrogenation.On the other hand,after aromatic ring hydrogenation of anisole,the demethylation of methoxycyclohexane occurred on acidic sites to produce cyclohexanol,and the dehydration of cyclohexanol and subsequent hydrogenation to produce cyclohexane.When the mass ratio of Al₂O₃:Zr O₂ was5:2,the complete conversion of anisole was realized at 230°C and 1 MPa,and the cyclohexane yield was 77.4%.2.Fe O_x decorated bimetallic Ni Fe catalyst derived from layered double hydroxides and its HDO performance of guaiacol.Ni Fe Al-LDHs were used as precursors to construct Fe O_x modified Ni Fe bimetallic catalysts with different Ni/Fe molar ratios after calcination and reduction.The cooperation of multiple active sites in the catalyst improves the guaiacol HDO performance of Ni Fe bimetallic catalyst:defective Fe O_x site in the catalyst is conducive to the removal of methoxy groups in guaiacol and 2-methoxycyclohexanol and the removal of hydroxyl group in cyclohexanol,while Ni Fe bimetallic alloy sites are responsible for the removal of hydroxyl group in cyclohexanol to produce cyclohexane.When the Ni/Fe molar ratio was3:0.5,at 230°C and 1 MPa,the complete conversion of guaiacol was realized and the cyclohexane yield was 70.5%.3.Cooperation between Ni Mo alloy sites and defective sites of hierarchical Ni Mo bimetallic catalysts in guaiacol HDO.Dopamine assisted hydrothermal approach was used to fabricate the Ni Mo bimetallic catalyst precursors.After reduction,Mo O_x modified Ni Mo bimetallic catalysts with different Mo/Ni molar ratios possessing three-dimensional hierarchical flower structures were obtained.The defective Mo O_x sites in the Ni Mo catalysts favor the removal of methoxy groups of guaiacol and intermediate 2-methoxycyclohexanol,while the Ni Mo bimetallic alloy sites promote the hydrogenolysis of intermediate cyclohexanol to produce cyclohexane.At the same time,the three-dimensional hierarchical flower structure is conducive to the better exposure of active sites and the adsorption and diffusion of reactants and intermediates,Thus,the catalytic HDO performance is greatly improved.When the Mo/Ni molar ratio was 0.1,the complete conversion of guaiacol was achieved at 230°C and 1 MPa,and the cyclohexane yield was 81.4%.