Theoretical Study On Hydrodeoxygenation Of Phenolic Compounds Over Fe-Pt Bimetallic Catalysts

Catalytic hydrodeoxygenation（HDO）is an important approach for the upgrading of lignin-based bio-oil,and Fe-based catalysts are a very important type of HDO catalysts.Oxyphilic iron has excellent selectivity for the hydrodeoxygenation of oxygen-containing compounds such as phenolic compounds,while the addition of a small amount of noble metals such as Pt to Fe catalysts is beneficial to stabilize the surface structure of Fe catalysts and promote the formation of surface active H*species.The composition and structure of Pt-Fe bimetallic catalysts and their interactions are key factors affecting the catalytic activity and product selectivity.Based on density functional theory（DFT）calculations,this thesis studied the adsorption,activation and hydrodeoxygenation mechanism of phenolic model compounds on the Pt-Fe bimetallic surfaces.Through the analysis of reaction mechanism,energetic pathways and kinetic barriers,the key parameters influencing the C-O bond cleavage activity were elucidated,the effect of bimetallic Pt-Fe surface structure on the catalytic activity and selectivity of phenolic compounds HDO was revealed,and the understanding of the synergistic effect of bimetallic catalysts was deepened.The stepped（211）surface among the different surfaces of iron,is advantageous for the selective removal of oxygen-containing functional groups in phenolic compounds.The Fe（211）surface was used as the substrate to study the different introduction forms of single Pt atom（single-site substitution and surface loading）as well as the effect of Pt loading content on the reaction perfoemance.The electronic interaction mechanisms of C-O bond activation and cleavage on the two 1Pt-Fe surfaces are different,and the selective deoxygenation of guaiacol on the 1Pt_ads-Fe（211）surface is better,but the difference is not significant between two surfaces.By studying different cluster-supported Pt_n/Fe（211）（n=1,2,4）,and Fe₃Pt₁（111）alloy surfaces,the effect of increasing Pt content on the HDO reaction was illustrated.The size of Pt clusters leads to different electronic properties on the Pt-Fe catalyst surface,which in turn affects the adsorption and reactivity of phenolic compounds.The smaller loading of Pt_nclusters onto Fe（211）is favorable for the selective deoxygenation of guaiacol.Fe-based catalysts have superior C-O bond cleavage selectivity for the HDO reaction of phenolic compounds,but the catalysts are also prone to oxidation during the reaction.In order to find out the effect of surface oxidation on the deoxidation activity,the adsorption behavior and C-O bond cleavage of guaiacol on different Fe₂O₃ catalyst surfaces were studied.The calculation results show that excessive surface oxidation increases the difficulty of deoxidation reactions.In this thesis,the composition and surface structure,electronic interaction,adsorption and activation,reaction mechanism,energetic pathways,and important factors affecting the catalytic performance are deeply studied at the molecular level,attempting to provide useful references for future design of efficient HDO catalysts.