Mixed metal oxide - noble metal catalysts for total oxidation of volatile organic compounds and carbon monoxide

CO, volatile organic compounds, and polyaromatics areubiquitous air pollutants that give rise to deleterious healthand environmental effects. Such compounds are emitted, forinstance, by the combustion of wood, particularly fromsmall-scale heating appliances. Total catalytic oxidation isconsidered to be an effective approach in controlling theseemissions, however, some problems remain such as thenon-availability of catalysts with low-cost, high activity andstability in prevailing conditions. Hence, this thesis aims atthe development of oxidation catalysts and improvedunderstanding of their behaviour. The catalytic activity was evaluated for the oxidation of amixture of CO, naphthalene (or ethylene), and methane inpresence of carbon dioxide, water, oxygen and nitrogen. Variouscharacterisation techniques, including Temperature-ProgrammedReduction and Oxidation, BET-Surface Area Analysis, X-RayDiffraction, X-Ray Photoelectron Spectroscopy, RamanSpectroscopy and Scanning and Transmission Electron Microscopywere used. In the first part of this thesis, catalysts based on metaloxides (MnOx, CuO) and/or a low amount of noble metals (Pt, Pd)supported on alumina washcoat were selected. It was shown thatPt and Pd possessed a superior catalytic activity to that ofCuO and MnOxfor the oxidation of CO, C10H8and C2H4, while for the oxidation of CH4, CuO was largely more active than noble metals,and MnOxas active as Pd and Pt. Some mixed metaloxide-noble metal catalysts showed decreased activity comparedto that of noble metals, however, a higher noble metal loadingor a successive impregnation with noble metals led to positivesynergetic effects for oxidation. Deactivation of the catalysts by thermal damage and sulphurpoisoning is addressed in the second part of the dissertation.An alumina washcoat was found to be well anchored to themetallic support after thermal treatment at 900°C due tothe growth of alumina whiskers. The sintering of the washcoatwas accelerated after high temperature treatments in thepresence of metal catalysts. ...