Reactions of molten Fe, Co, Cu, and Pb sulfides with hydrogen
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IN
a recent paper 1 the kinetics and mechanism of the reaction between molten nickel sulfide and hydrogen were reported. Measurement of the hydrogen sulfide generation rate showed the rate of reduction of nickel sulfide to be second order in sulfur concentration and half order in hydrogen p r e s s u r e in the range investigated. The kinetics were consistent with a rate determining step involving a reaction between Sa and hydrogen in the melt. It was further concluded that the nickel in the molten sulfide may be functioning as a catalyst by promoting the reaction of Sa and hydrogen. In view of these observations the present paper examines the kinetics and mechanisms of reactions of other molten transition metal sulfides with hydrogen and, for comparison purposes, the reaction of a typical nontransition metal sulfide with hydrogen. Fe, Co, Ni, and Cu are well known for their ability to activate hydrogen heterogeneously and, under some conditions, homogeneously, a,a This catalytic activity has long been associated with the unsaturated d-shell structure of these metals. On the other hand, lead is considered to be rather inactive with respect to activation of hydrogen. By using the same experimental approach previously employed for the study of the r e action between nickel sulfide and hydrogen, kinetic data were obtained for reactions of iron sulfide, cobalt sulfide, copper sulfide, and lead sulfide with hydrogen. The kinetics of each sulfi~le system in turn provide information as to the possible mechanism of reaction which includes a metal catalyzed step.
EXPERIMENTAL The experimental method used in this investigation consisted of direct reaction of molten Fe, Co, Cu, and Pb sulfides with hydrogen. The kinetics of these r e a c tions were determined by measuring rates of hydrogen
consumption ( - r Ha), rates of sulfur consumption (-- rs),* *The kinetic data for the reaction of cobalt sulfide with hydrogen were based only on rates of sulfur consumption (-rs), since no density data are available for molten cobalt sulfide. i
and rates of hydrogen sulfide generation (rHaS). Both the generation rate of hydrogen sulfide and consumption rate of hydrogen were obtained by applying an open system treatment to the concentration of these gases in the outlet gas mixture. The rate of sulfur consumption was determined by analysis of sulfide samples withdrawn periodically from the melt. A complete description of all experimental details is given in a recent article. 1 Materials The Fe, Co, and Pb sulfides were prepared by heating pure iron powder (99.88 pct purity), cobalt powder (99.0 pct purity), and lead foil (99.99 pct purity) with reagent grade sulfur in high purity recrystallized alumina crucibles. The copper sulfide (CuaS) was p r e pared by desulfurizing CuS powder (99.4 pct purity). All fusions were done under purified argon. The iron was carbonyl iron powder MC grade supplied by the International Nickel Company of Canada Ltd., cobalt was supplied by Matheson, Coleman and Bell Co., lead and sulfur were supplied by Brit
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