Binding of phenolic model compounds with noble metal doped graphene sheets

Abstract

Abstract Presence of large number of oxygenates in raw bio-oil restrict its application as transportation fuel. Therefore, there is a strong necessity of finding a viable catalyst for upgrading raw bio-oil to transportation fuel level. In this study, palladium- and platinum- doped graphene sheets are examined theoretically for possible interactions of oxygenates such as guaiacol, phenol, anisole, vanillin, and salicylaldehyde on to metal doped graphene catalyst surfaces to understand preliminary adsorption mechanisms. For this purpose, B3PW91 functional of density functional theory (DFT) has been utilized. Adsorption kinetics, for instance, adsorption free energy, adsorption enthalpy, and equilibrium rate constant at a fixed pressure of 1 atm but over a wide range of temperature (400–800 K) are reported. Briefly results indicate that binding of both metals at vacant site of graphene sheet is found to be high energy releasing process and excellently agree with their contemporary literature results. The interaction of hydroxyl group of salicylaldehyde with Pd-doped graphene (PdGr) surface is most favourable configuration, whereas, Pt-doped graphene (PtGr) surface exhibited superior adsorption stability through phenyl ring. Binding of guaiacol, phenol, and anisole are energetically most favourable by phenyl ring interaction over each surface. Vanillin interacts strongly by oxygen atom of formyl group over PtGr surface. Further the values of adsorption kinetic parameters are very high for all model species; however, temperature increment deteriorates them. Finally, for each adsorption configuration of all model species over both catalyst surfaces, ln(Keq) vs. 1/T relation is proposed.