Theoretical Study On Hydrodeoxygenation Of Phenol Over Bimetallic M@Ni(111)single Atom Surface Alloy

Bio-oil,a renewable green energy source which can replace fossil fuels,has attracted attentions to academic and industry communities.However,bio-oil without upgrading has a large amount of oxygen-containing functional groups in their structure,which makes the oil high viscosity and low calorific value.It's impossible to be miscible with hydrocarbon fuels.Therefore,hydrodeoxygenation?HDO?of bio-oil is a key step in converting biomass oil into transportation oil.Selectively activating C-OH bond cleavage of phenolics by catalyst design is essential to hydrodeoxygenation of lignin-derived bio-oil for the removal of oxygen content.Herein,Using phenol as a probe molecule for lignin-derived oxygenates,we have systematically investigated HDO over Ni-based bimetallic single-atom surface alloys denoted as M@Ni?111?where M=Sc,Ti,V,Cr,Mn,Fe,Co,Mo,W,Re.According to the research:?1?It is found that the alloyed M atoms can modify electronic structure of local active sites by lifting d-band centers of three nearest neighboring Ni-M-Ni atoms which enhance OH*binding strength and accordingly phenol HDO,while have only negligible geometric effects on phenol adsorption.?2?From these ten kinds of monoatomic catalysts,we selected V,Fe,Mo,W,and Re represented by 3d,4d,and 5d to perform direct deoxygenation?DDO?and partial hydrodeoxygenation?PHDO?,partial hydrodeoxygenation?PHDO?contributes most to benzene formation.Herein,charge transfer to the Ni host??q?or BE value can be used to estimate the oxophilicity of alloyed M.These observations confirm that the oxophilic M atoms alloyed into the host metal surface forming a bimetallic system play an essential role in selectively activating C–O bond scission.?3?We reveal that for optimal phenolic-HDO performance,a balance of alloyed M's oxophilicity should be achieved to maximize DDO,PHDO,and H₂O formation simultaneously.The predicted turnover frequency?TOF?for benzene formation follows the volcano curve varying with OH*binding strength.Accordingly,M@Ni?111?where M=Fe,Re,Mn,Mo,Cr,are predicted to be promising Ni-based bimetallic catalysts for facilitating phenolic HDO.which can serve as an effective catalytic descriptor for deoxygenation activity producing phenyl hydrocarbon products.Our study could provide a theoretical guidance for designing highly active and selective HDO catalysts for upgrading bio-oil.