Structural/surface characterization of transition metal element–doped H-ZSM-5 adsorbent for CH3SH removal: identification of active adsorption sites and deactivation mechanism
CH 3 SH is a potential hazard to both chemical production and human health, so controlling its emissions is an urgent priority. In this work, a series of transition metal-loaded H-ZSM-5 adsorbents (Si/Al = 25) (Cu, Fe, Co, Ni, Mn, and Zn) were synthesized through the wet impregnation method and tested for CH 3 SH physicochemical adsorption at 60 °C. It was shown that the Cu-modified H-ZSM-5 adsorbent was much more active for CH 3 SH removal due to its abundant strong acid sites than other transition metal-modified H-ZSM-5 adsorbents. The detailed physicochemical properties of various modified H-ZSM-5 adsorbents were characterized by SEM, XRD, N 2 physisorption, XPS, H 2 -TPR, and NH 3 -TPD. The effects of metal loading mass ratio, calcination temperature, and acid or alkali modification on the performance of the adsorbent were also investigated, and finally 20% Cu/ZSM-5 was found to have the best adsorption capacity after calcined at 350 °C. Additionally, the Cu/ZSM-5 adsorbent modified by sodium bicarbonate could expose more active components, which improved the adsorbent’s stability. However, the consumption and reduction of the active component Cu 2+ and the accumulation of sulfate during the adsorption process are the main reasons for the deactivation of the adsorbent. In addition, the simultaneous purging of N 2 + O 2 can effectively restore the adsorption capacity of the deactivated adsorbent and can be used as a potential strategy to regenerate the adsorbent. Graphical
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