The catalytic reaction couples of aromatic hydrogenation and its reverse dehydrogenation make it possible to store or to transport hydrogen as one component element in organic chemicals. The hydrogen densities capable of recovery from methylcyclohexane / toluene and decalin / naphthalene pairs amount to 6.4 and 7.3 wt%, respectively. Large-scale catalytic hydrogenation of toluene or naphthalene started early in contrast to endothermic dehydrogenation, since the latter required high-temperature reaction conditions thermodynamically and certain catalytic devices protecting from carbon deposite.
As the result of reactive distillation under boiling and refluxing conditions, catalytic hydrogen evolution from organic chemical hydrides could proceed stationarily. High reaction rates and large extents of conversion were accomplished by adopting “superheated liquid-film states” for dehydrogenation catalysts. Vigorous formation of bubbles at the catalytic active sites would accelerate the desorption process of reaction products, because heats were transferred along with the temperature gradients from the external high-temperature thermo-reservoir toward the substrate solution at the boiling point. An important role for avoiding thermodynamic restriction is taken by this thermal flow, where applicable is not the isothermal equation ( ΔG = ΔH-TΔS ) but the irreversible one ( ΔG* = ΔH-Δ(TS) ), leading us to such positive non-zero correlation as ΔG-ΔG* = SΔT > 0, with the equibrium conversion ( ΔG ) overcome at the reacting conditions (ΔG*).
Nickel-ruthenium bimetallic catalysts were found recently to be effective to liquid-phase dehydrogenation of organic chemical hydrides as well performed as platinum-based catalysts.