Influence of Impregnation Medium on the Adsorptive Performance of Silica Sulfuric Acid for the Removal of Gaseous o-Xylene: Comparison on Ethyl Acetate and Water

Abstract

Silica supported sulfuric acid (SSA) has been demonstrated to be capable of effectively removing phenyl VOCs through the reaction-type adsorption mechanism. The effects of the solvent (water, ethyl acetate) used to impregnate silica gel with H2SO4 solution in order to prepare SSA adsorbents have been studied. As-prepared two series SSA(E)-x and SSA(W)-x materials (x = 1, 2, 3, 4) were characterized by TG, SEM/EDS and N2 adsorption/desorption techniques, and their breakthrough adsorption performances were evaluated from experimental and theoretical aspects. The results showed that the H2SO4 loading amounts were 2.8, 4.0, 4.8 and 5.6 mmol g−1 respectively for both SSA(E)-x and SSA(W)-x when x equaled 1, 2, 3, 4. Among them, SSA(E)-4 was found to have a higher proportion of the C-state H2SO4 than SSA(W)-4. Both SSA(E)-x and SSA(W)-x exhibited significant removal capacity of gaseous o-xylene. The reactive temperature regions were determined to be 120–170 °C for SSA(E)-4 and 120–160 °C for SSA(W)-4 with a common optimum point of 160 °C. Both SSA(E)-x and SSA(W)-x adsorbents exhibited excellent recyclability and reuse performance. Further, the series SSA(E)-x materials outperformed the series SSA(W)-x on all adsorption performance metrics, suggesting that ethyl acetate is a preferred solvent for preparing the SSA materials in phenyl VOCs removal application.

Reactive Adsorption of Gaseous Anisole by MCM–41-Supported Sulfuric Acid

“…As can be seen in Figure 1, the response curve of the anisole removal ratio (X a ) vs. temperature (T) presented an inverted U-shaped profile, indicating that there was an appropriate temperature window of 110-140 • C for the reactive adsorption of anisole by SSA/MCM-41, with both sides experiencing an activation stage (upward trend) and a deactivation stage (downward trend). The response curve of anisole on SSA/MCM-41 was similar to that of o-xylene on various supported sulfuric acid systems such as SSA/MCM-41, SSA/SBA-15, SSA/SG, and silica sulfuric acid [16][17][18][19]. Therefore, anisole was expected to follow the same reactive adsorption mechanism as o-xylene, i.e., it was removed from the gaseous stream by the sulfonation reaction with the anchored H 2 SO 4 molecules on SSA/MCM-41.…”

“…The removal performance and transformation products of target pollutants is most probably linked to their molecular structures. However, only the o-xylene results have been reported to date [17][18][19]. Supported adsorbents that have been tested include silicasupported sulfuric acid (SSSA) [16], synthetic silica-supported sulfuric acids (SSAI and SSAII) [19], and mesoporous MCM-41-and SBA-15-supported sulfuric acids (SSA/MCM-41 and SSA/SBA-15) [17].…”