Development of a liquid chromatographic method for the separation of a liquid organic hydrogen carrier mixture

• Liquid organic hydrogen carriers are potential candidates for hydrogen storage.
• A chromatographic method for separation of partially hydrogenated LOHC is presented.
• The method is successfully scaled up to the semi-preparative scale.
• Recovery method of desired product from eluent is presented.

Liquid organic hydrogen carriers (LOHC) are an interesting option for hydrogen storage and transportation. This concept is based on reversible hydrogenation and dehydrogenation of a carrier compound for uptake and release of hydrogen respectively. Among others, dibenzyltoluene is a potential LOHC due to its reasonable hydrogen storage capacity (6.2 ma-%) and high thermal stability. However, a huge number of stable intermediates with different degrees of hydrogenation are observed in a partially hydrogenated reaction mixture of dibenzyltoluene. For the process development and studies of the dibenzyltoluene reaction mechanism, it is crucial to determine physico-chemical properties of its various partially hydrogenated fractions, which requires their isolation from the reaction mixture. In this work, a reversed-phase high performance liquid chromatography (RP-HPLC) method for the separation and purification of partially hydrogenated mixtures of dibenzyltoluene is presented. The method was developed and validated at analytical scale and successfully scaled up to semi-preparative scale. The mixture was separated into four fractions according to their degree of hydrogenations using phenylhexyl silica stationary phase and a mobile phase consisting of acetone/water (96/4, v/v). Fractions with purity above 98% and yield higher than 90% were obtained in a semi-preparative column with an internal diameter of 50 mm.