Solid support ionic liquid (SSIL) adsorbents for mercury removal from natural gas

Abstract

Mercury removal is an integral part of gas-processing and coal combustion plants due to its implication on health, environment and process equipment. Utilization of impregnated carbons and metal sulfide-based adsorbents for mercury removal are common, however with limitations in adsorption capacity and life time. Continued efforts to develop porous carbon sorbents with better mercury adsorption capacity and kinetics are evident from the open literature with the recent focus being on solid support ionic liquid (SSIL)-based adsorbents with ionic liquid and chelating agents. However, reports on application of SSILs-based adsorbents for gas-phase mercury removal are not available in the open literature. Toward this objective, the present work attempts to synthesize three different SSILs adsorbents identified as SSIL (porous carbon + IL), SSILM (porous carbon + IL + MPTS), SSILA (porous carbon + IL + APTS–MBT) utilizing ultrasound-induced wet impregnation method. The adsorbents were subjected to characterization utilizing BET, XRD, FT-IR and SEM and were tested for its mercury adsorption capacity. The SSIL sorbents were found to possess higher order of magnitude adsorption capacity as compared to high-surface-area porous carbons and metal sulfide-based porous carbons. The adsorption capacity of the SSILs increased orders of magnitude with increase in adsorption temperature from 30 to 50 °C attributed to the predominance of the chemisorption. Among the three SSIL adsorbents, SSILA was found to exhibit highest equilibrium adsorption capacity of 36.9 mg/g at 50 °C. ΔH°, ΔS° and ΔG° indicate that elemental mercury adsorption on SSILA is a spontaneous and endothermic process.