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Title: Reaction of sulphur containing gases with zinc oxide absorbents
Author: Sohail, Khalid
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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The reactions of H2S and COS with high purity (99.9&37 ) and doped (Ca, Cd, Cu, Ni, Na and Pd) zinc oxide absorbents were investigated using batch recycle and plug flow reactors and using DRIFTS. The absorbents were characterised by BET surface area measurement, scanning electron microscopy, thermal decomposition and atomic absorption elemental analysis. High purity ZnO was also characterised by the 1R studies of adsorption of H2O, CO2 and O2. The reaction between ZnO and H2S is structure sensitive. The sulphiding mainly takes place on the Zn-polar and O-polar faces of ZnO and proceeds to its bulk through a continuous rearangement and replenishment of hydroxyls due to H2O on these polar faces. The surface reaction takes place in two steps; first S-H groups form on the surface and then these groups are converted into surface sulphide where the first step is fast. The second step is slow in the absence of excess H2O. The reaction pattern is such that the initial reaction is fast where the solid's consumption varies from 4 to 35% depending upon the pre-treatment conditions of the absorbent such as temperature and atmosphere of calcining, water saturation, etc. Doping ZnO with Cd, Co and Cu improves its sulphiding capacity and rate compared to the high purity ZnO whereas doping with Na and Ca inhibits the sulphiding. The dopants directly affect the reaction on the polar faces as well as the bulk of the solid and affect the ZnO crystallite morphology. The effect of the presence of O2 and CO2 in the reactant H2S stream on the ZnO sulphiding performance was also investigated. The possible bulk reaction mechanisms were proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available