N2O decomposition over (CaO)1-x(MO)xoxide systems (M=Ti, Cr):relation with photoluminescence

Abstract

(CaO) _1-x (MO) _x oxide systems (M=Ti, Cr;x=0–1), prepared at 1150 °C under atmospheric conditions, were investigated for their photoluminescence as well as for their catalytic activity in N ₂ O decomposition in the temperature range 400–650 °C. As shown by XRD analysis, the solids are either multicomponent systems or simple phase oxides. Titanium addition to CaO of up to 30% results in a significant enhancement of the catalytic activity, while chromium addition beyond 1% has the reverse effect; solids rich in Ti or Cr are rather inactive. Thus, the systems showing considerable activity are either simple phase CaO, or CaO–CaTiO ₃ mixed oxides. The photoluminescence intensity of the catalysts was found to be suppressed by addition of Cr or Ti (>0.5%) to CaO. Although the catalytic activity is affected in different ways by addition of Ti or Cr, and a variety of structural composition are noted for the (CaO) _1-x (MO) _x catalysts, a relation between catalytic activity and photoluminescence is observed, not only across each sample series, but also for the total set of catalysts.