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A copper-based metal organic framework (MOF-199) was synthesized by a hydrothermal method and was used to remove hydrogen sulfide, ethyl mercaptan, and dimethyl sulfide. Characterizations of the samples before and after desulfurization were carried out by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The adsorption performance of the prepared sample MOF-199 was evaluated by breakthrough experiments in a fixed-bed reactor. Heat treatment was carried out in nitrogen flow to activate the prepared MOFs. The optimum activation temperature was found to be 180 °C. Evaluation results showed that the breakthrough capacity of MOF-199 for hydrogen sulfide removal increased with the working temperature, whereas the capacity for ethyl mercaptan and dimethyl sulfide removal decreased with the temperature. MOF-199 had the highest breakthrough sulfur capacity for dimethyl sulfide removal (8.48 g of sulfur/100 g of MOF-199). The color of the MOF changed during sulfur capture in all cases, indicating a change in the chemical environment of the copper metal site. Interactions between the unsaturated copper sites in MOFs and the sulfur compounds differed because of the steric effect. A strong interaction was apparent during adsorption of ethyl mercaptan and hydrogen sulfide, which resulted in the formation of various amounts of CuS and serious damage to the MOF structure. The relatively weak interaction with dimethyl sulfide originated from electrostatic force and a weak coordination effect, which led to easy recycling and recovery of MOF-199 by thermal regeneration at 180 °C.

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The performance of γ-Fe 2 O 3 as sorbent for H 2 S removal at low temperatures (20−80°C) was investigated. First, γ-Fe 2 O 3 /SiO 2 sorbents with a three-dimensionally ordered macropores (3DOM) structure were successfully prepared by a colloidal crystal templating method. Then, the performance of the γ-Fe 2 O 3 -based material, e.g., reference γ-Fe 2 O 3 and 3DOM γ-Fe 2 O 3 /SiO 2 sorbents, for H 2 S capture was compared with that of α-Fe 2 O 3 and the commercial sorbent HXT-1 (amorphous hydrated iron oxide). The results show that γ-Fe 2 O 3 has an enhanced activity compared to that of HXT-1 for H 2 S capture at temperatures over 60°C, whereas α-Fe 2 O 3 has little activity. Because of the large surface area, high porosity, and nanosized active particles, 3DOM γ-Fe 2 O 3 /SiO 2 sorbent shows the best performance in terms of sulfur capacity and utilization. Moreover, it was found that moist conditions favor H 2 S removal. Furthermore, it was found that the conventional regeneration method with air at high temperature was not ideal for the composite regeneration because of the transmission of some amount of γ-Fe 2 O 3 to α-Fe 2 O 3 . However, simultaneous regeneration by adding oxygen in the feed stream allowed the breakthrough sulfur capacity of FS-8 to increase up to 79.1%, which was two times the value when there was no O 2 in the feed stream.

A series of iron oxide sorbents with novel structures of three-dimensionally ordered macropores (3DOM), ranging in size from 60 to 550 nm, were fabricated and creatively used as sorbents for the removal of H2S at medium temperatures of 300-350 °C. Evaluation tests using thermogravimetric analysis (TGA) and a fixed-bed reactor showed that, in comparison to the iron oxide sorbent prepared by a conventional mixing method, the fabricated iron oxide sorbent with a 3DOM structure exhibited much higher reactivity and efficiency, as well as high sorbent utilization with low regeneration temperature. The excellent performance of 3DOM iron oxide as a sulfur sorbent is attributed to its special texture, i.e., the open and interconnected macroporous, large surface area, and nanoparticles of iron oxide, which are revealed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption techniques. The investigation results of the pore effect on the performance of the sorbent show that sorbents with pores size around 150 nm in diameter revealed the best performance. The reason is that pores of this size are large enough to allow gas to pass through even if the channel is partially blocked during the reaction process while remaining a large surface area that can provide more active sites for the reaction.

A series of novel zinc oxide-silica composites with three-dimensionally ordered macropores (3DOM) structure were synthesized via colloidal crystal template method and used as sorbents for hydrogen sulfide (H2S) removal at room temperature for the first time. The performances of the prepared sorbents were evaluated by dynamic breakthrough testing. The materials were characterized before and after adsorption using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that the composite with 3DOM structure exhibited remarkable desulfurization performance at room temperature and the enhancement of reactive adsorption of hydrogen sulfide was attributed to the unique structure features of 3DOM composites; high surface areas, nanocrystalline ZnO and the well-ordered interconnected macroporous with abundant mesopores. The introduction of silica could be conducive to support the 3DOM structure and the high dispersion of zinc oxide. Moisture in the H2S stream plays a crucial role in the removal process. The effects of Zn/Si ratio and the calcination temperature of 3DOM composites on H2S removal were studied. It demonstrated that the highest content of ZnO could reach up to 73 wt % and the optimum calcination temperature was 500 °C. The multiple adsorption/regeneration cycles showed that the 3DOM ZnO-SiO2 sorbent is stable and the sulfur capacity can still reach 67.4% of that of the fresh sorbent at the fifth cycle. These results indicate that 3DOM ZnO-SiO2 composites will be a promising sorbent for H2S removal at room temperature.

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