Investigation of ethanol-phenol interactions used in steam reforming process: Molecular level understanding through experimental and theoretical studies

Ethanol-phenol binary mixtures are used as feed for hydrogen production in the steam reforming process. The present work investigates the physicochemical properties of the various compositions of ethanol-phenol binary mixtures experimentally to understand the interactions of these two molecules at the molecular level. The densities (ρ) and sound velocities (U) values of the binary mixtures increased with the mole fraction of the phenol. The excess molar volume (VmE) and various acoustic parameters such as acoustic impedance (ZE), compressibility (βsE), and intermolecular free length (LfE) were computed in the whole mole fraction range. The negative values of VE, LfE, βsE and positive values of ZE, UE up to a 0.5 mole fraction of phenol indicate strong intermolecular interaction between dissimilar molecules than similar molecules. DFT/B3LYP computational methods were used to optimize the structure of the monomer of ethanol and phenol and the dimers, ethanol-ethanol, ethanol-phenol, and phenol-phenol with a 6-311G ++ (d, p) basis set. The variation of energy of all-possible conformers of homo and hetero molecular dimers of ethanol and phenol was computed by varying the distance between the molecules. The energy values obtained in the computational method supported the experimental findings well and envisaged the significant interaction between ethanol-phenol than ethanol-ethanol and phenol-phenol binary mixture at a 1:1 composition. Summarizing, the 1:1 stoichiometric ratio of the ethanol-phenol binary mixture could be the appropriate feedstock for optimal hydrogen production in the steam reforming process, and accordingly suitable substitute of this mixture can be designed to lessen the overload on ethanol-phenol mixture.