Influence de l'oxygène absorbé sur la sulfatation de l'oxyde de nickel par le dioxyde de soufre
Abstract
The interactions between gaseous sulfur dioxide and nickel oxide at 250°C have been investigated by means of temperature-programmed desorption (TPD) and microcalorimetric techniques. Depending on the thermal treatment of the oxide, different NiO samples were prepared containing chemisorbed oxygen species, O1, O2, O3 and O4, with different energies. The calorimetric data indicated that the weakly-bound species O1 is the most reactive of the oxygen forms towards sulfur dioxide. In this case, the TPD curves (m/e=48 and m/e=32) show a new peak at 710°C; this may be correlated with the desorption of a sulfur-containing compound, probably NiSO4, created by oxidation of sulfur according to the reaction SIV ↔ SVI. The regeneration of the species O1 has been studied as a function of the temperature of oxygen adsorption; the most favourable temperature for the sulfation of nickel oxide appears to be about 400°C.