Catalytic hydrogen supply from a decalin-based chemical hydride under superheated liquid-film conditions

Chemical Recuperation of Low-Quality Waste Heats by Catalytic Dehydrogenation of Organic Chemical Hydrides and Its Exergy Analysis

“…A platinum catalyst supported on the granular activated carbon (KOH-activation, BET specific surface area 3100 m 2 /g, pore volume 1.78 cm 3 /g, average particle size 13 µm, average pore size 2.0 nm, Kansai Netsukagaku Co. Ltd – , First, granular powders of the base-pretreated activated carbon were stirred with a K 2 PtCl 4 aqueous solution at room temperature for 48 h, which was followed by dropwise addition of a NaBH 4 aqueous solution at 90 °C for 30 min. Here, all metallic species added to the granular activated carbon were experimentally confirmed to be adsorbed onto the carbon support during impregnation step by measuring the concentration of the residual metallic species in the supernatant aqueous solution after 48 h by means of the ultraviolet−visible spectroscopy (U-3300 spectrometer, Hitachi) .…”

“…Figure A shows the experimental apparatus for catalytic dehydrogenation under atmospheric pressure in batchwise mode. – Catalytic dehydrogenation of methylcyclohexane to toluene using this batchwise reactor (eggplant-type flask, volume 50 mL) was performed under boiling and refluxing conditions by heating at 180−240 °C and cooling at 5 °C. The platinum catalyst supported on granular activated carbon (Pt/C, 5 wt-metal %) was evacuated inside the reactor at 150 °C for 1.0 h before use.…”

“…In order to popularize hydrogen energy systems, e.g., fuel cells and hydrogen vehicles powered by internal combustion engines (ICE), however, any technological breakthrough on hydrogen storage and transportation is urgently required. Organic chemical hydrides, – consisting of reversible reaction pairs such as decalin dehydrogenation/naphthalene hydrogenation (eq ) and methylcyclohexane dehydrogenation/toluene hydrogenation (eq ), have been proposed by our group as the materials for carrying hydrogen due to the following excellent properties: (1) high storage capacities ( cis -decalin 7.3 wt %, 64.8 kg-H 2 /m 3 ; methylcyclohexane 6.2 wt %, 46.5 kg-H 2 /m 3 ; the target values presented by the U.S. Department of Energy (DOE) 6.5 wt %, 62.0 kg-H 2 /m 3 ); (2) facile reversibility; (3) being safe and cost-competitive. …”

“…The superheated liquid-film-type catalysis, – , a novel concept developed by our group, made it possible for the first time to generate hydrogen quite efficiently from organic chemical hydrides at moderate heating temperatures of 200−300 °C without coke formation. By charging an adequate amount of reactant solution (e.g., decalin and methylcyclohexane) to a constant amount of solid catalyst, consisting of metallic nanoparticles (e.g., platinum, platinum−rhenium, and nickel−ruthenium) supported on activated carbon, “the superheated liquid-film state” is realized. – , Since the catalyst surface is covered with a thin liquid-film of solution but not suspended, this catalyst state has been designated as a “liquid-film state”. – , This liquid-film state was confirmed to exhibit much higher catalytic activities than those with ordinary heterogeneous catalysis in the either solid−gas or solid−liquid phase. Therefore, it is possible to utilize low-quality waste heats below 300 °C as the heat source for endothermic dehydrogenation.…”

Dehydrogenation Catalyst for Organic Hydride on the Basis of Superheated Liquid-Film Concept

“…Properly-wetted nano-metal catalysts, supported on highly-porous activated carbon, had been chosen for efficient dehydrogenation [7][8][9][10]. Reasons of choice would be summarized as follows.…”