Influence of preparation method on the adsorptive performance of silica sulfuric acid for the removal of gaseous o-xylene

Abstract

Two types of silica supported sulfuric acid (SSA), with same sulfuric acid loading of 3.4 mmol g−1, were prepared by sol-gel processing (SSAI) and impregnation method (SSAII). The TG/DSC and FTIR characterization revealed that two anchoring states coexisted for the sulfuric acid supported on the silica surface: a physiosorbed (P)-state and a chemically bonded (C)-state. The dynamic adsorption analysis demonstrated that both SSAI and SSAII possessed a significant removal capacity for gaseous o-xylene in the reactive temperature regions (120–200 °C and 130–200 °C), which could be attributed to the sulfonation reaction between o-xylene and anchored sulfuric acid. The optimum temperatures were noted to be 150 °C and 160 °C for SSAI and SSAII respectively. Further, SSAI exhibited a higher breakthrough adsorption capacity (QB, 184.9 mg g−1) as compared to SSAII (142.8 mg g−1). QB was noted to be closely associated with the amount or proportion of the C-state sulfuric acid on the SSA surface. The optimal values of breakthrough time and QB were obtained by enhancing the bed height and decreasing the flow rate and inlet concentration. Both SSAI and SSAII exhibited excellent recyclability and reuse performance over eight consecutive adsorption/regeneration cycles, thus, suggesting that the SSAs prepared using different methods, especially SSAI, have a significant potential of application as adsorbents for the removal of BTEX pollutants.