GBL/BDO pair as a bio-based liquid organic carrier: Kinetic modeling of liquid phase hydrogenation and dehydrogenation over copper-based catalyst

The use of liquid organic hydrogen carriers (LOHC) for hydrogen storage has technical, economical, and environmental advantages. The gamma -butyrolactone (GBL)/1,4-butanediol (BDO) pair is used in this work as a bio-based LOHC. Reaction kinetics of liquid phase GBL hydrogenation and BDO dehydrogenation have been studied using a semi -batch reactor filled with a copper based methanol catalyst with the experiments have been performed in the temperature range of 458 - 503 K with a constant pressure of 50 and 3 bar for hydrogenation and dehydrogenation respectively. Based on analytical results, a reaction pathway including the formation of side products was proposed. This pathway includes the formation of two side -products: 4-hydroxybutyl 4-hydroxybutanoate (4HHB) is produced from the transesterification of GBL by BDO in both reactions; and dibutyleneglycol (DG) from the etherification of BDO in dehydrogenation. Based on experimental results, kinetic models were established for hydrogenation and dehydrogenation reactions. In these models, balanced reactions with a first order were used. Estimation of kinetic parameters for both reactions allows a good prediction of the experimental data and results in a temperature extrapolation by an Arrhenius law. Activation energies for GBL hydrogenation and BDO dehydrogenation were determined to be respectively 104 kJ/mol LOHC and 98.3 kJ/mol LOHC . Furthermore, models are valid at short (up to 5 h) and long (up to 20 h) reaction times and the estimation results display acceptable uncertainties for all the reaction temperatures.