Adsorption Mechanism and Regeneration Performance of 13X for H2S and SO2

Claus tail gas including 1-2 vol % sulfur compounds in forms of H2S and SO2 requires to be purified for discharging. However, there are few research studies focusing on simultaneous removal performance and mechanism of H2S and SO2 mixed gases with high water vapor. In this paper, 13X was used as a sorbent to simultaneously remove H2S and SO2 in the simulated Claus tail gas. Desulfurization and regeneration performance of 13X in a fixed bed were studied. Meanwhile, the removal mechanism and the decline in regeneration efficiency of 13X in the thermal N-2-purging process were investigated by using characterization techniques of X-ray fluorescence, X-ray diffraction, transmission electron microscopy, N-2 adsorption-desorption, Raman spectroscopy, thermogravimetry-differential thermal analysis, and X-ray photoelectron spectroscopy. The results showed that the breakthrough sulfur capacity of 13X was 179.7 mg S/g sorbent, three times more than that of activated carbon (64.3 mg S/g sorbent). The adsorption removal mechanism of 13X for H2S and SO2 mixed gases was an adsorption- redox process, and crystal planes (111) and (220) in 13X were the main active centers. Under the oxygen-containing atmosphere, H2S was oxidized to elemental sulfur and SO2 was oxidized to sulfuric acid adsorbed on 13X. Meanwhile, H2S and SO2 also produced elemental sulfur through Claus reaction. Sulfur species in 13X existed in forms of elemental sulfur (ca. 40 atom %) and sulfate species (ca. 60 atom %) after the adsorption process. The proportion of elemental sulfur in 13X-E was twice as much as that of activated carbon (20 atom %). After five adsorption-regeneration cycles, the specific surface area of 13X-R decreased by 24.5% because of a small amount of sulfate residues in the pores of 13X, leading to the incomplete recovery of crystal planes (111) and (220) and the decrease of strength of crystallization which resulted in the slight decrease of micropore volume and specific surface area.