Emission of hydrogen gas from weathered steam coal piles via formaldehyde as a precursor - I. Oxidative decomposition of formaldehyde catalyzed by coal - batch reactor studies

Molecular hydrogen is formed as a result of low temperature (40 degrees C-115 degrees C) weathering of steam (bituminous) coal which occurs during relatively long term storage periods of coal piles. It is observed that: formaldehyde is the precursor intermediate (formaldehyde was suggested as one of the ambient temperature oxidation products of coal). The study of the thermal decomposition of formaldehyde in batch reactors has shown that the decomposition reaction occurs only in the presence of oxygen and bituminous coal (the catalyst). The stoichiometric reaction observed, is the coal catalyzed oxidative decomposition of formaldehyde: [GRAPHICS] This is in contrast with the commonly observed chemical behavior of formaldehyde as hydrogen donor upon decomposition to yield carbon monoxide as a product. A possible mechanism by which the coal catalyzed oxidative decomposition of formaldehyde occurs is suggested and discussed in detail. (C) 1999 Elsevier Science Ltd. All rights reserved.