Adsorption Isotherm of Dibenzyl Toluene and its Partially Hydrogenated Forms Over Phenyl Hexyl Silica

Abstract

Liquid organic hydrogen carriers (LOHC) are an interesting option for chemical energy storage and hydrogen transportation. Dibenzyltoluene (H0-DBT), heat transfer oil, is capable of reversibly storing hydrogen emerged as a feasible LOHC system. However, it is not available as a pure compound but consists of an isomeric mixture of 6 to 8 compounds. During the hydrogen storage process a high number of stable intermediate species is formed. These compounds can be categorized into four main classes according to their degree of hydrogenation. To implement H0- DBT as a LOHC system, thermophysical data of these intermediate compounds are required. In our previous work, a reversed phase HPLC method was developed using phenylhexyl silica stationary phase and acetone/water as eluent to separate these partially hydrogenated fractions with a purity >98%. For further designing a batch or continuous HPLC process, adsorption isotherm data are required. In this work, adsorption isotherms for dibenzyltoluene and its partial and fully hydrogenated forms namely hexahydro-dibenzyltoluene, dodecahydro-dibenzyltoluene, and octadecahydrodibenzyltoluene are measured over phenylhexyl silica in acetone/water solvent using the static method. Sip’s equation (Combined Langmuir-Freundlich isotherm) fits the data better as compared to simple Freundlich, Langmuir or competitive Langmuir adsorption isotherms.