Studies on NO_X conversion over transition metal ion (TMI) dopeq alumina-boria system

Abstract

Catalytic decomposition of NO_X has been studied using a fixed bed tubular flow reactor in the temperature range 573-773K, over six aluminium-borate catalysts (containing 2Al₂O_3.B₂O₃ as the major phase and 9Al₂O_3.2B₂O₃ as the minor phase) doped with different transition metals. The catalyst phases have been characterised by XRD, IR, ESR and ESCA studies on fresh and used catalyst samples. The results indicate structural stability of the catalyst phase over the experimental temperature range and oxidation of Co²⁺ to CO³⁺ accompanied by surface migration of CO³⁺ species. No valence change in the other transition metal ions and surface oxygen enrichment in, the used catalyst .is observed. Kinetic studies show a first order dependence, on NO_X partial pressure in the lower temperature: region, except in the case of the mixed doped catalyst. Breaks in the Arrhenius plots at about 673K are noted for all the catalysts.