Selective Removal of Hydrogen Sulfide from Gaseous Streams Using a Zinc-Based Sorbent

Sol-Gel Synthesis of Zinc Alumotitanate, Monitoring of Chelation, Hydrolysis, Condensation, and Crystallization Processes

Zinc alumotitanate sorbents with various compositions were prepared through sol-gel synthesis with the use of ethyl acetoacetate as a chelating agent. The formation and decomposition of chelates, providing insight into sol-gel process advancement, have been successfully monitored via 1H NMR, 13C NMR, and FTIR spectroscopy. It has been established that Al(OBus)3 and Ti(OBun)4 react completely with Eaa, forming chelates after 1 h, while after 24 h hydrolysis is already advanced. Hydrolysis is accelerated in the presence of Zn(NO2)3·6H2O, supplying the water needed for hydrolysis. In dried gels, the amount of ethyl acetoacetate is greatly reduced, and it is mainly present unbound. According to XRD analysis, samples with none or less titania are composed of layered double hydroxide, while in samples with greater amounts of titania, crystal nitrates are present. In all samples except those without Al, the spinel phase with variable composition crystallizes.

Enhanced adsorption of hydrogen sulfide on mixed zinc/cobalt hydroxides: effect of morphology and an increased number of surface hydroxyl groups

Mixed zinc and cobalt hydroxides were synthesized using a precipitation method and tested as adsorbents of hydrogen sulfide from either dry or moist air. The adsorption capacity increased with an increase in the content of cobalt in the structure of mixed hydroxides. The synergistic effect was demonstrated by a fourfold increase in the amount of hydrogen sulfide adsorbed on the surface of the best performing mixed hydroxide in comparison with the hypothetical mixture of the two hydroxides. The initial and exhausted materials were characterized by FTIR, thermal analysis, potentiometric titration, X-ray diffraction, SEM/EDX, and adsorption of nitrogen. The results obtained suggest that an increase in the content of cobalt results in an increase in amorphicity level and in an increase in the number of hydroxyl groups. These groups, besides providing higher basicity thereby increasing the extent of H2S dissociation in the presence of water, are the main active centers reacting with hydrogen sulfide. Defects in the structure and oxygen vacancies result in the oxidation of some H2S to sulfites and sulfates.