Comparative Kinetics of High-Temperature Reaction Between H2S and Selected Metal Oxides Phillip R. Westmoreland', James 6. Gibson', and Douglas P. Harrison* Department of Chemical Engineering, Louisiana State University, Baton Rouge, La. 70803
Initial rates for the reactions between H2S and MnO, CaO, ZnO, and Vz03over a temperature range of 300-800 "C were determined in a thermobalance reactor. All reactions were first order with respect to H2S and obeyed the Arrhenius equation. The relative magnitude of reaction rates determined was MnO > CaO = ZnO > V2O3. MnO possessed favorable properties for a high-temperature desulfurization process, and additional research in this area is recommended. Numerous reactions between solid metal oxides and H2S a t high temperature are reported in the literature (1).Such reactions form the basis of past processes for coke oven gas purification using iron oxide (2, 3), existing processes for ammonia synthesis gas desulfurization (4),and developing processes for sulfur removal from gases produced from coal or residual oil gasification (5). Success in the last application is particularly important if coal gasification technology is to achieve optimal development. Although the reactions are well known, basic kinetic data are quite sparse, the notable exception being the work by Ruth et al. (6) on the HzS-dolomite system. Several reasons for the scarcity of kinetic studies may be cited. Perhaps of greatest importance is the emphasis placed upon rapid process development with little priority assigned to studying the basic phenomena. In addition, gas-solid kinetic studies are inherently difficult, both from the experimental and data interpretation aspects. In a previous paper, Westmoreland and Harrison (7) reported on a thermodynamic investigation of the desulfurization feasibility of a large number of elements a t cbnditions representative of future high sulfur coal gasification. Eleven metals and their oxides were identified as possessing desulfurization potential over at least a portion of the raqge of operating conditions of interest. In this paper we are reporting comparative kinetic measurements for four of the candidate oxides-Mn0, ZnO, CaO, and VzO3. Experimental
Operating Conditions. Initial rates of chemical reaction were determined over a temperature range of 300-800 "C a t 1atm total pressure. H?S concentration was varied from 1.9 to 7.0 mol %. Hydrogen was added to the reactive gas in a ratio of 5 mol Hz/mol of Has, both to simulate the reducing atmosphere found in coal gases and to prevent the decomposition of H2S a t high temperature. Separate tests at low temperatures (
