Cross-method identification of hydrogenated species originating from dibenzyltoluene/(benzyl)benzyltoluene in a promising commercial LOHC product

A commercial heating fluid, called with the generic name “DBT”, composed of different isomers of dibenzyltoluene (DBT) and of (benzyl)benzyltoluene (BBT), is known as a potential Liquid Organic Hydrogen Carrier (LOHC). The analysis of the hydrogenated mixtures was performed using gas chromatography alone (GC-FID) or coupled with mass spectrometry (GC-MS). The hydrogenated compounds used for the analysis were obtained by the hydrogenation of the commercial mixture at 150 °C. The identification of all the isomers originated from DBTs was achieved studying specific fragmentation observed in electronic ionization (EI) mass spectra. The distinction between hydrogenated DBTs and BBTs was also obtained. The isomer distinction was further supported by the molecular balances established during hydrogenation experiments carried out at 150 °C. 2,3-DBT and 3,4-DBT were synthesized and hydrogenated individually to facilitate the identification of their hydrogenated compounds, which showed certain inversions in the chromatograms. For the BBT isomers, the identification of each individual isomer is not confirmed, mainly due to overlap of compounds under GC peaks. However, the degree of hydrogenation of all the BBT derived compounds was determined. • All hydrogenated isomers of dibenzyltoluene (Hx-DBT) were identified. • The identification was carried out using MS, kinetics, mass balance and synthesis. • The distinction between Hx-(benzyl)benzyltoluene and Hx-DBT was achieved. • 51 out of 71 molecules were identified.