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 N2-purging process were investigated by using characterization
techniques of X-ray fluorescence, X-ray diffraction, transmission
electron microscopy, N2 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.