Exploring the potential of infrared spectroscopy on the study of the adsorption/desorption of siloxanes for biogas purification

[Display omitted] •In situ observation of D4 polymerization into PDMS over activated carbon.•The rate of PDMS desorption from AC is maximum at 250°C.•AC pretreatment above 250°C induces the strengthening of the D4-AC interaction.•In situ FTIR spectroscopy appears as a powerful technique to study the reactivity of D4 adsorbed in AC. A commercial activated carbon (AC) was characterized by physicochemical methods. The AC adsorption/desorption properties and the adsorbent regenerability were evaluated for the removal of octamethylcyclotetrasiloxane (D4), a common siloxane impurity in biogases. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) was employed to investigate the adsorption of D4 on AC at room temperature and its thermodesorption up to 300°C. The AC was activated in N2 at varying temperatures within the 25–300°C interval. The striking feature is the polymerization of D4 observed during the desorption experiment followed by the release of PolyDimethylSiloxane (PDMS) in the gas phase. The thermal treatment before adsorption is proposed to influence the D4–AC interaction.