Vibrational spectroscopy study of zinc-containing mixed oxides as regenerable sulphur sorbents at high temperature

Abstract

Four series of zinc-based mixed oxides doped with Fe, Cu or Ti, as potential regenerable desulphurization sorbents of coal gas at high temperature were characterized using vibrational spectroscopies, in conjunction with previous studies in which the same sorbents were studied by XRD, SEM-EDX and XPS. For each series, the influence of the composition, within a broad range of concentration in their component oxides, and the temperature of calcination of the fresh sorbents, as well as the structural modifications undergone during sulphidation/regeneration cycles were investigated. It is shown that by analysing the end-process materials, vibrational spectroscopies can reveal fairly well the formation of spinel-structure compounds, sulphides and probable sulphates during calcination, sulphidation and regeneration, respectively. Additionally, vibrational spectroscopies can detect short-range structural changes, not evidenced by XRD, and can be used with advantage to study the evolution of these compounds under real operating conditions.