Benchmark properties of diphenyl oxide as a potential liquid organic hydrogen carrier: Evaluation of thermochemical data with complementary experimental and computational methods

The standard molar enthalpy of vaporisation of diphenyl oxide was derived from the vapour pressure temperature dependences measured by the transpiration method. Thermodynamic data on vaporisation processes available in the literature were collected. They were evaluated and combined with our own experimental results. Additional combustion experiment on the highly pure diphenyl oxide helped to resolve ambiguity in the enthalpy of formation for this compound. We have evaluated and recommended the set of vaporisation and formation enthalpies for the diphenyl oxide at 298.15 K (in kJ·mol−1): ΔlgHmo = (66.7 ± 0.2), ΔfHmo (liq) = −(15.8 ± 1.4), and ΔfHmo (g) = (50.9 ± 1.4), as the reliable benchmark properties for further thermochemical calculations. Gas phase molar enthalpy of formation of diphenyl oxide calculated by the high-level quantum-chemical method G4 was in an excellent agreement with the recommended experimental data. The standard molar Gibbs function of formation and the standard molar entropy of formation of diphenyl oxide were estimated. The hydrogenation/dehydrogenation reaction enthalpy of diphenyl oxide was calculated and compared with the data for other potential liquid organic hydrogen carriers.