Role of the process conditions on the sulphation and stability of a CuO/SBA-15 type SOx adsorbent in cycling operations

SOx abatement is one of the major challenges for the industry with regards to the more stringent European regulations. Despite their good performance, current DeSOx technologies are energy-intensive and produce waste. Flue gas desulphurisation using SOx adsorbents thus is a viable alternative. However, the development of such a technology is still hampered by the adsorbent short lifetime within the wide range of conditions prevailing at the exhaust of combustion engines. In this work, a CuO/SBA-15 adsorbent was assessed as a SOx trap material under different sulphation conditions (temperature from 350 °C to 450 °C, gas composition (SO2: 250, 450 and 450 ppm; O2: 150 vol%), GHSV from 18,000 to 110,000 h−1 and sulphation time). The SO2 adsorption capacity of the adsorbent was greatly impacted by the temperature: the higher the temperature, the better the performance. Indeed, the dynamic adsorption capacity is equal to 31 mgSO2/gads, 37 mgSO2/gads and 52 mgSO2/gads at 350 °C, 400 °C and 450 °C respectively. Conversely, no significant changes in the SO2 dynamic adsorption capacity were observed whatever the SO2 and O2 molar fractions in the adsorption gas stream. The GHSV appears as a very sensitive parameter since the higher this parameter, the worse the adsorbent performance (e.g. for GHSV of 25,000 h−1, Cads = 37 mgSO2/gads; for GHSV of 50,000 h−1, Cads = 19 mgSO2/gads). Stabilised SO2 adsorption capacities along 25 cycles were obtained by regenerating before the breakthrough. Under these conditions, no SO2 emission occurs during the adsorption step, which represents the major technology block faced in any multicycle adsorption-based process over time.