CuO-catalyzed depolymerization of polydimethylsiloxane (PDMS) promotes the thermal regeneration of siloxanes in activated carbon

Activated carbon (AC) adsorption is the primary method for removing siloxanes from biogas, but siloxane polymerization during adsorption hinders regeneration, limiting the reuse of adsorbents and long-term biogas utilization. This study investigates the thermal regeneration efficiency of copper oxide-modified activated carbon (CuO/AC) compared to conventional AC for removing octamethylcyclotetrasiloxane (D4) from biogas, and employed GPC, XPS, and theoretical calculations to elucidate the role of CuO in enhancing regeneration performance. CuO/AC achieved a regeneration efficiency of 70.3 % at 230°C, 26.9 % higher than AC, with no residual D4 detected and the formation of higher molecular weight polymers. DFT calculations indicated that Si–O bond cleavage requires less energy on CuO than on AC, consistent with XPS results, confirming that CuO acts as a Lewis acid site to catalyze the ring-opening polymerization of D4, and promote the further volatilization of PDMS depolymerization products at elevated temperatures, thereby improving the regeneration efficiency of AC-based adsorbents. This work provides new insights into the reuse of activated carbon in conventional biogas purification processes.