Mechanism of the Catalytic Gasification and Reactivity of Graphite.

摘要

Graphite is being used as a carbon source for gasification to insure that hydrogen or hydrogen in hydrocarbons is derived from water. Relatively low temperatures (500 to 800K) are used to favor the equilibrium C + 2H sub 2 O implies CH sub 4 + CO sub 2 which is almost thermally neutral. In the presence of alkali hydroxide C sub 2 -C sub 6 hydrocarbons are formed in addition to H sub 2 , CH sub 4 and CO sub 2 . Formation of hydrocarbons is a stoichiometric reaction proceeding on the crystal edges to form a phenolate and hydrocarbons, e.g. 5C + 4KOH 4COK + CH sub 4 . Surface spectroscopy has confirmed the presence of phenolate, which can be decomposed over metal oxide to make the reaction truly catalytic: 4COK + MeOx implies 2K sub 2 O + 2C + 2CO; 2K sub 2 O + 2H sub 2 O implies 4KOH. In the presence of both KOH and metal oxide the major products are CO sub 2 and H sub 2 with traces of CH sub 4 and CO. The 2:1 ratio of H sub 2 /CO sub 2 appears due to either or both watergas shift and Boudouart reaction. The mechanisms will be illustrated by electron microscopy and XPS measurements. 7 refs., 11 figs. (ERA citation 10:026619)