Platinum Metals Rev., 1963, 7, (1), 14
Production of Hydrogen from Coal
Palladium Catalysts in Dehydrogenation of Vitrain
The possibility of the economic production of molecular hydrogen by the catalytic dehydrogenation of coal is suggested by the results of work reported recently by R. Raymond, I. Wender and L. Reggel, of the Pittsburgh Coal Research Center, U.S. Bureau of Mines (Science, 1962, 137, (August 31st), 681-682). Surprisingly large yields of hydrogen were obtained in attempts to determine the hydroaromaticity of coal by the dehydrogenation of vitrains and other related materials with the use of polycyclic aromatic solvents and supported palladium catalysts.
In the laboratory-scale process, 0.5 g finely-divided coal (—200 mesh), the solvent and 0.55 g palladium-on-calcium carbonate catalyst were refluxed together for five hours in a helium atmosphere. Generally the major part of the gases, consisting of hydrogen with small amounts of carbon monoxide, carbon dioxide and methane, was evolved in the first hour. With phenanthridine as solvent and a 30 percent palladium-on-calcium carbonate catalyst, 30 percent of the hydrogen contained in Pittsburgh vitrain was evolved. Other coals, under the same conditions, gave lower but appreciable yields of hydrogen, depending on their rank. About 50 per cent of the total hydrogen content of Pittsburgh vitrain was evolved when 2-azafluoranthene was used as solvent, but it is thought that some of this hydrogen was due to side reactions.
Yields of about 30 per cent of the total hydrogen in Pittsburgh vitrain were also obtained when other platinum metal catalysts were used with phenanthridine as solvent. Such catalysts included 1 and 5 percent palladium-on-calcium carbonate, 5 percent palladium-on-alumina, 5 percent ruthenium-on-alumina, and 5 percent rhodium-on-alumina. A commercial chromia-on-alumina catalyst was totally ineffective in these conditions.
This catalytic dehydrogenation process, demonstrated so far only on a small scale, has indicated a possible new use for certain coals as a source of hydrogen gas.