Catalytic effect of iron in hydrogasification of coal

Hydrogasification of coal is a technique to produce synthetic natural gas (SNG), which offers the advantage of methane production in a single process step. A fundamental limitation of hydrogasification is the low reactivity of hydrogen compared to steam or oxygen, towards coal chars. Utilization of a low-cost catalyst which would greatly enhance the reactivity of hydrogen towards coal char would significantly impact the SNG program. While investigating mineral matter effects in coal gasification, we observed that finely divided hematite enhances the production of methane, by a factor of fifteen, during char gasification at one atmosphere of hydrogen. Gasification rates are measured by heating the samples in a thermal gravimetric analysis (TGA) system to a fixed temperature and then monitoring the rate of weight loss versus time. Product gas analysis indicates that during char gasification with hematite present, greater than 85 mole % of the gas is methane. The catalytic form of the hematite has been identified as reduced iron. The effect of the reduced iron as a catalyst is strongly dependent on particle size. The catalytic activity is also dependent on precursor species with the following order observed: Fe/sub 2/O/sub 3/ > Fe/sub 3/O/sub 4/ > FeS/sub 2/ > Fe.