Computational Studies On The Regulation Of Regulation Of Active Sites Of Noble Metal Catalysts And The Calculation Of Their Catalytic Hydrodeoxygenation Of Biomass Platform Molecules

With the depletion of fossil resources and the intensification of the greenhouse effect,renewable biomass resources have become the key to obtaining fuels and high-value chemicals.Biomass can be degraded into bio-oil by pyrolysis,depolymerization and other methods.At present,hydrodeoxygenation（HDO）reaction is an important bio-oil upgrading method,which can remove the oxygen-containing functional groups in bio-oil,thereby reducing the oxygen content in bio-oil and improving the utilization value.Noble metal catalysts play an important role in the HDO reaction.Noble metals such as Pt and Pd have excellent H₂ dissociation ability,and can efficiently break C-O bonds in coordination with metal carriers such as Co and Nb.Although noble metal catalysts have made great progress in HDO reaction,there are still the following key problems:（1）The mechanism and structure-activity relationship of HDO reaction catalyzed by noble metal catalysts are not clear;（2）The regulation of the crystal phase of noble metal catalysts and the influence of noble metal species on the catalytic performance are still controversial.This limits the structural design of efficient HDO catalysts to some extent.Based on the above key issues,this paper uses the density functional theory calculation method to study the relationship between the active site structure regulation of monoatomic alloy catalysts and supported noble metal catalysts and HDO reactivity and selectivity from the perspective of regulating the crystal phase of the catalyst and the type of supported noble metal,and reveals its catalytic reaction mechanism.The main research contents and conclusions are as follows:（1）Crystal phase sensitivity of Pt₁Co single-atom alloy catalyst for 5-hydroxymethylfurfural hydrodeoxygenation.The effect of crystal phase of Pt₁Co-fcc and Pt₁Co-hcp surfaces on the HDO reaction of 5-hydroxymethylfurfural was investigated by density functional theory（DFT）calculations.The activity and selectivity of HDO reaction for the conversion of 5-hydroxymethylfurfural to 2-hexanol and2-methyltetrahydrofuran on Pt₁Co-fcc and Pt₁Co-hcp surfaces were compared.Due to the uneven active sites on the surface of Pt₁Co-hcp,the adsorption energy of 5-hydroxymethylfurfural on Pt₁Co-hcp surface is higher than that on Pt₁Co-fcc surface.Furthermore,the Pt₁Co-hcp surface exhibits a low effective energy barrier and has good catalytic activity for HDO reaction.Due to the atomic arrangement of Pt₁Co-fcc surface is denser than that of Pt₁Co-hcp surface and the coordination number of Co atom is higher,2-hexanol is the dominant product of Pt₁Co-fcc surface,while Pt₁Co-hcp surface tends to produce 2-methyltetrahydrofuran.In addition to promoting hydrogen dissociation and hydrogenation capabilities,Pt single atom shows a specific synergistic effect with Co on the Pt₁Co-fcc surface,accelerating the cleavage of the C1-O1 bond.This work provides valuable theoretical guidance for the refined structure regulation of HDO catalysts.（2）Computational study on the selective hydrodeoxygenation of guaiacol catalyzed by M₄/Nb₂O₅.（M=Ru,Rh,Pd,Ir,Pt）Five kinds of M₄/Nb₂O₅（M=Ru,Rh,Pd,Ir,Pt）catalysts were constructed by density functional theory（DFT）calculation.The effects of metal species and metal-support interaction on the HDO reaction activity and product selectivity of guaiacol were investigated.The differences in activity and selectivity of HDO reaction converted into different intermediates and final products on the surface of five catalysts were revealed.The results show that the adsorption energy of guaiacol on Ru₄/Nb₂O₅ surface is much higher than that of the other four kinds of surface adsorption energy due to the two Ru atoms at the Ru₄ interface lose electrons and the metal atoms at the other interface get electrons.When Ru₄ and Pt₄ are supported on Nb₂O₅,the main HDO product is cyclohexanol;when Pd₄ and Ir₄ are supported on Nb₂O₅,the main product is benzene;the main product cyclohexane can be obtained by selecting Ir₄.Among them,Ru₄/Nb₂O₅ has the highest reactivity,while Pt₄/Nb₂O₅ has the highest product selectivity,which is consistent with the d-band center results of the five metal clusters.Through the Pearson correlation coefficient,the activity and selectivity descriptors are linearly analyzed.It is concluded that the optimal descriptor of activity is the first ionization energy of metal,and the optimal descriptor of selectivity is the electronegativity of metal.This descriptor can provide information for further adjusting the geometric structure and electronic structure of multi-component catalysts to achieve directional regulation of HDO products.