Superhydrophobic and stable mesoporous polymeric adsorbent for siloxane removal: D4 super-adsorbent

Abstract

Synthesis of a new class of siloxane adsorbent (D4) was done to purify methane-rich gases including biogas and digester gas, at near ambient temperature and atmospheric pressure. The nanoporous polymeric adsorbent with controlled wettability was successfully prepared under solvothermal conditions. Imidazole groups were introduced into the samples by copolymerization of divinylbenzene (DVB) with 1-vinylimidazole (VI). The copolymer composition was varied to obtain optimum adsorption performance. Low-cost PDVB and PDVB-VI were evaluated under different adsorption conditions with a gas flow rate of 10 mL min⁻¹. To simulate near real time biogas composition, 50%-relative humidity at 25 °C was maintained to assess the effect of humidity on D4 removal efficiency. In addition, the mixture gas was used to evaluate the adsorptive activity in the presence of CO₂ (up to 35%). While PDVB alone demonstrates a significant adsorption activity with a capacity of 1951 ± 74 mg g⁻¹, an improvement in adsorption capacity to 2370 ± 92 mg g⁻¹, was noted with PDVB-VI. Characterization of exhausted adsorbent demonstrates the correlation between D4 adsorption and PDVB-VI-x textural properties. Finally, PDVB-VI-x was readily regenerated after five cycles with less than 10% loss in adsorption activity under both dry and humid conditions.