Influence of the water vapor on the activity of CuO/SBA-15 SOx adsorbents

Study of the reversible/irreversible character of the deactivation of CuO/SBA–15 SOx adsorbents in wet conditions under SO2 adsorption/regeneration cycling experiments

“…The interaction between the copper active phase and the support most likely involves species of type Cu 2+ -O-Si type, which are in strong interaction with the support, as reported in a previous study [12]. As also set out in a previous work [22], transmission electron microscopy analyses performed after all the DeSOx experiments show that copper-based nanoparticles are present not only in the porosity of the support, with a size similar to the one of the average mesopore diameter (6 nm), but also outside the pores with larger sizes (Figures 5 and 6). These particles are formed by the migration and agglomeration of the copper active phase, at a rate depending on the thermal conditions of the DeSOx experiments:…”

“…For this adsorbent, the irreversible part of the deactivation is less important than the one of the 15CuO/SBA-15 (20 % versus 45 % of the initial ). This interesting finding is probably linked to the lower copper oxide concentration, which induces a more stable dispersion of the CuO active phase particles on the support and thus a better retention of the reactivity of the copper species for the adsorption reactions, this point was discussed in our previous work [22] and is confirmed by the transmission electron microscopy analyses (vide infra). This stability of the CuO dispersion at the lower concentration of CuO (7 wt.%) induces a higher and more stable at around 100 mgSO 2 /gCuO (cycle 41 to 50) than the one obtained with a higher concentration of CuO (15 wt.%) for which continues to decrease from around 90 to 50 mgSO 2 /gCuO (cycle 41 to 50).…”

“…-Concerning the spent 15CuO/SBA-15 adsorbent, the nanoparticles outside the support pores appear larger and in higher amount at 450 °C than at 400 °C, with a size around 60-90 nm and 50-60 nm, respectively. The increase of temperature from 400 to 450°C actually favors the mobility of the copper active phase particles towards the entrance of the pores of the SBA-15 support, resulting in their migration and coalescence to form larger particles located outside the porosity [22]. This point is also supported by the increase of the variation of dispersion of the CuO active phase after the DeSOx test at 450 °C (Figure 6), which is around 85 % versus 55 % at 400 °C.…”

“…The SBA-15 silica support was synthesized in a large amount, according the procedure used in a previous work [22]: 196 g of porogen agent (Pluronic ® P123, Sigma-Aldrich) was dissolved in 1,121 g of HCl (37 wt.%, Carlo Erba) and 6,387 g of demineralized water, at 45 °C for 12 h. Then, 425 g of silica precursor (Tetraethylorthosilicate, Evonik) was added to the solution, which was kept under stirring for 4 h at 45 °C. Afterward, the mixture was heated up to 90 °C for 18 h, under static mode and autogenous pressure.…”

“…However, the combustion of solid and liquid fossil fuels generates water vapor in the flue gas, which is likely to impact the activity of the SOx adsorbents. For this reason, we have investigated in an previous work [22] the effects of water vapor on the performance of the CuO/SBA-15 as a SOx adsorbent over multiple adsorption/regeneration cycles, looking more specifically at the influence of the process temperature and the CuO loading. It has been shown that when water vapor is present in the gas phase during the adsorption step, it can entail two distinct and apparently contradictory effects:…”