Electron spin resonance studies of formation of SO –2 radicals on calcium oxide
Abstract
The formation of SO–2 radicals on CaO has been studied by e.s.r. spectroscopy. CaO, prepared by evacuating CaCO3 at 1173 K was exposed to sulphur dioxide at 473 K. Under these conditions, SO–2 radicals were observed at concentrations of ≈ 3 × 1017 spins g–1. The effect of the heat-treatment temperature of the starting CaCO3 and of the adsorption temperature have been examined. The SO–2 radicals are stable up to 473 K, but decay with second order kinetics above 498 K. The radicals react with oxygen to form SO–4 radicals at 77 K and SO–3 radicals at room temperature.