Removal of Gaseous Hydrogen Sulfide by a FeOCl/H₂O₂ Wet Oxidation System

Abstract

The removal of gaseous hydrogen sulfide using FeOCl/H 2 O 2 was studied. The effects of the FeOCl dosage, the H 2 O 2 concentration, the reaction temperature, and the gas flow rate on the removal of H 2 S were investigated. The reaction products were analyzed, and the characterization of FeOCl was carried out by X-ray diffraction, scanning electron microscopy, Xray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy. Furthermore, radical quenching experiments were carried out using butylated hydroxytoluene, isopropanol, and benzoquinone. It was found that the H 2 S removal rate for a H 2 S gas concentration of 160 ppm reached 85.6% when bubbling through 100 mL of an aqueous solution containing FeOCl (1 g/L) and H 2 O 2 (0.33 mol/L) at 293 K with a flow rate of 135 mL/min. Although the dissolution of chlorine in FeOCl was found to result in reduced catalytic performance, the activity was restored after soaking the catalyst in concentrated hydrochloric acid (37%) and subsequent calcination. The mechanism of H 2 S removal was also discussed, and it was found that this process was controlled by H 2 S diffusion. FeOCl was found to activate H 2 O 2 and produce radicals, such as • OH and • O 2 − , resulting in the formation of a water film rich in radicals on the FeOCl surface. Following the diffusion of H 2 S into the water film, it underwent oxidation by radicals to produce SO 4 2− . Overall, the catalyst and the product can be effectively separated.

Removal of Gaseous H2S by the Titanium Silicalite-1/H2O2 Wet Oxidation System

“…As shown in Figure 2E, η increased from 81.6 to 86.3% as the temperature increased from 283 to 293 K. However, the efficiency did not increase significantly as the temperature continued to increase to 303 K, and for that reason, a higher temperature is beneficial to accelerate the diffusion while detrimental to dissolution for gaseous H 2 S. 14 As presented in Figure 2F, η decreased slightly from 86.3 to 80.4% within 15 h and changed little in the next 5 h. In this experiment, for one of the reactants, H 2 S, the concentration remained unchanged, while that of another reactant, H 2 O 2 , decreased as a result of the reaction consumption. The oxidation products of H 2 S could be elemental sulfur (S 0 ), SO , with the reaction equation shown in eq 4.…”

“…As shown in Figure E, η increased from 81.6 to 86.3% as the temperature increased from 283 to 293 K. However, the efficiency did not increase significantly as the temperature continued to increase to 303 K, and for that reason, a higher temperature is beneficial to accelerate the diffusion while detrimental to dissolution for gaseous H 2 S …”

“…15 Studies 14−16 showed that free state radicals (such as − and • OH, respectively. 14,40 Thus, an experiment using IPA and BQ was carried out to verify whether • O 2 − and • OH are involved in the reaction. Results are shown in Figure 10, and η in the system was not affected after using IPA and BQ, indicating that the oxidation of H 2 S is caused by neither • O 2 − nor • OH.…”

“…In recent years, the studies on the removal of H 2 S by the wet oxidation system has attracted much attention. − Wang and his colleagues , developed a system with hydrogen peroxide (H 2 O 2 ) and persulfate as the oxidizer and Fe 3+ and Cu 2+ as the catalyst to remove gaseous H 2 S, which achieves efficient desulfurization at a low cost, whereas, in such a homogeneous system, the separation and recovery of the catalyst become a problem.…”

“…However, the efficiency decreased gradually, attributed to the destruction of FeOCl in an acid solution, and after continuous reaction for 6 h, the removal rate of H 2 S decreased by 17%. 14 Titanium silicalite-1 (TS-1) zeolites are considered as a stable catalyst in acidic environments, 20 and the wet oxidation system of TS-1 zeolites and H 2 O 2 (TS-1/H 2 O 2 ) has been widely used in Beckmann rearrangement of cyclohexanone oxime, propylene epoxidation, and oxidation of aromatic sulfur compounds because of its highly catalytic ability, non-pollution, and low cost. 20−22 Nevertheless, we are not aware of any studies on the removal of gaseous H 2 S by the TS-1/H 2 O 2 wet oxidation system.…”