MeO_x/SBA-15 (Me = Zn, Fe): highly efficient nanosorbents for mid-temperature H₂S removal

Abstract

Zinc oxide/ and iron oxide/SBA-15 composites were synthesized using the innovative Two-Solvents procedure and tested as sorbents for the mid-temperature (300 C) removal of hydrogen sulphide, and then compared with a commercial unsupported ZnO sorbent. The sulphur retention capacity results showed the superior performance of the iron oxide/SBA-15 composite (401 mg S g1 Fe2O3) in comparison with the zinc oxide/SBA-15 composite (53 mg S g1 ZnO), both these sorbents being much more efficient than the commercial sorbent (6 mg S g1 ZnO). The different sorption behaviour was discussed in terms of the nature of the nanocomposites where: (i) the mesostructure of the support was retained with a high surface area and pore volume; (ii) the zinc oxide phase was incorporated inside the SBA-15 channels as a thin amorphous homogeneous layer while the iron oxide was dispersed in form of small maghemite crystallites; and (iii) significant interactions occurred between the silica matrix and the zinc oxide phase. Remarkable differences in the regeneration behaviour of the exhaust sorbents were revealed by temperature-programmed experiments under an oxidizing atmosphere. After regeneration, the sorption properties of the zinc oxide/SBA-15 composite appeared to be enhanced compared to the commercial sorbent. Incomplete recovery of the sorption activity was observed for the regenerated iron oxide/SBA-15 sorbent, whose performance remained far better than that of the ZnO-based one, either fresh or regenerated. In view of its higher sulphur retention capacity and appropriate regeneration temperature (T # 350 C), the iron oxide/SBA-15 composite is a promising material for the design of advanced sorbents for a thermally efficient H2S removal process from hot gas streams

Meso- and macroporous silica-based arsenic adsorbents: effect of pore size, nature of the active phase, and silicon release

“…15Fe-SBA15 reveals the presence of small particles (dark spots) or dark channels all over the support, compatible with the pore size of SBA15 and with no evidence of particles outside the support, due to the efficient impregnation strategy. 72,73,[86][87][88][89][90] In contrary, the macroporous composite 15Fe-MOSF reveals the presence of iron oxide particles inside and outside the pores of about 10 nm -20 nm. The particles are difficult to visualize due to the presence of the macroporous silica support.…”

“…The presence of a bimodal pore size distribution obtained by BJH model for the 15Fe-SBA15 can be justified due to the presence of small NPs instead of a homogeneous film of the impregnating phase on the support, leading to smaller Fe 2 O 3 -impregnated pores and empty larger ones. 89 Conversely, only a slight decrease in the surface area is evinced for the 15Fe-MOSF composite, from 226 m 2 /g to 219 m 2 /g (Figure 1d, Table 1).…”

Exploiting XPS for the identification of sulfides and polysulfides

“…The problem of sulfur speciation at the surfaces of materials is of general interest, involving chemists, geochemists, physics and material scientists. Sulfur speciation is of crucial importance for studies on portable storage devices (rechargeable Li-S batteries), [1][2][3] on mineral processing and oxidation processes, 4,5 on tribology, 6,7 on sorbents for desulfurization 8 and on corrosion phenomena. 9 Authors have been involved over the last decade in research on arsenic bearing sulde minerals oxidation [10][11][12][13][14] and biooxidation and particular attention was devoted to the investigation of the surface alteration of the minerals by means of surface analytical techniques (XPS and XAES) in order to clarify the mechanism of oxidative dissolution especially for enargite.…”

Modified and systematic synthesis of zinc oxide‐silica composite nanoparticles with optimum surface area as a proper H2S sorbent

“…Among different metal oxides, incorporation of zinc oxide particles into silica can considerably enhance the physicochemical properties of composite materials . Composite materials containing a zinc oxide phase have extended applications in different fields including environmental issues such as photocatalytic decomposition and removal of pollutants in the industry, adsorbing toxic components like hydrogen sulphide as a fatal hazardous gas, catalytic synthesis of methanol, development of gas sensors, catalytic oxidation of carbon monoxide, etc.…”