Maximizing the degree of dehydrogenation of perhydro-dibenzyl toluene via in-line distillation for continuous hydrogen release in commercial systems

AbstractDibenzyl toluene is an organic compound that can store hydrogen via chemical bonding of hydrogen having a storage capacity of 9 mol_H2/mol_DBT to form perhydro-dibenzyl toluene. When required, the stored hydrogen can be retrieved by supplying thermal energy, however, in most applications continuous hydrogen supply is required like in fuel cell applications, the degree of dehydrogenation can go well below 30% making the process highly inefficient as well as uneconomic. Unlike benzyl toluene, reactive distillation is not viable for perhydro dibenzyl toluene since a minimum of 350 °C will be required for its separation which can cause permanent degradation of the DBT molecule. This study introduces in-line distillation with the dehydrogenation reactor. Dual distillation is found to have excessive thermal energy requirements while providing insignificant improvement in the output degree of dehydrogenation. Moreover, an intermediate reservoir is essential for continuous operation by preventing increased flowrate through the reactor. For an output of megawatt class hydrogen energy using 400 kg catalyst and distillate to feed ratio of 0.75 gives a continuous operation at inlet concentration of 0.927 and net output DoD of 0.921 at the expense of additional 58.6 kW which can be improved using 600 kg catalyst that gives a net output DoD of 0.982 with slight increase of 2.2 kW thermal energy.