Optimization of Preparation Conditions of Vanadium-Based Catalyst for Room Temperature Oxidation of Hydrogen Sulfide

MCM-41 silica spheres were synthesized and functionalized with 3-aminopropyltriethoxysilane (3-APTES). The Schiff base has been derived from amino groups and 5-boromo salicylaldehyde, then a tetra dentate Cu(II)–Schiff base complex was prepared. This compound was characterized by X-ray diffraction, nitrogen physisorption, UV–Vis spectrometer, transmission electron micrographys (TEM), IR-spectra, and TGA/DTA technique. The prepared grafting Cu-salen-MCM-41 over a mesoporous surface was found to be an efficient and selective catalyst for the oxidation of different sulfides into sulfoxides with urea hydrogen peroxide (UHP) giving excellent yields at room temperature. The results showed that Cu-salen-MCM-41 is an effective catalyst for the oxidation of sulfides and can be repeatedly used and regenerated with no significant decrease in its catalytic ability. They also showed that the prepared material retained a good mesoporous structure and the best catalytic properties.

Oxidodiperoxidomolybdenum Complexes: Properties and Their Use as Catalysts in Green Oxidations

The state of surface adsorption sites in the IK-42-1 oxide catalyst for ammonia oxidation depending on catalyst preparation conditions (the nature of raw materials and the temperature of calcination) was studied in this work with the use of the diffuse reflectance IR spectroscopy of the adsorbed NO probe molecule. Hematite, which was prepared by a sulfate or chloride technology, was used as the starting raw material; Al2O3 binding agents were prepared by the reprecipitation or hydration of thermally activated gibbsite; and acetic or nitric acid was used as an electrolyte. The samples were calcined at 900–1000°C. It was found that mono- and dinitrosyl complexes with reduced coordinatively unsaturated Fe2+ cations and nitrite-nitrate complexes were formed upon the adsorption of NO on the catalyst surface (regardless of the catalyst preparation conditions). The samples differed in the amount and degree of coordinative unsaturation of adsorption sites depending on the preparation conditions. It was concluded that the most coordinatively unsaturated Fe2+ adsorption sites observed were formed on the surface of a solid solution of iron cations in aluminum oxide, which was formed in the course of catalyst preparation. It was found that an increase in the catalyst calcination temperature resulted in a decrease in the number of coordinatively unsaturated adsorption sites, which correlated with the observed decrease in the yield of NO. This correlation had the shape of a saturation curve, which can reflect the occurrence of a reaction in the diffusion mode at high degrees of conversion for the majority of catalysts.

Selective oxidation of organic sulfides to sulfoxides has been the subject of extensive research because of their importance of sulfoxides as intermediates in various organic reactions. One of the simplest methods for oxidation of sulfides to sulfoxides is the use of hydrogen peroxide as an oxidant in the presence of a catalyst. Though a number of catalysts including soluble metal complexes have been used for the reaction, there are a few reports employing a heterogeneous catalyst despite the advantage in separation and reuse of the catalyst. In this paper, we introduce a new heterogeneous catalyst, HNbMoO6, which shows an excellent catalytic activity in the oxidation of sulfides. Trirutile-type solid oxide, AMM’O6, was first synthesized in 1970. Since then, many applications of the solid oxide in various fields such as non-linear optics and composites have been reported. However, the catalytic activity of the oxide in organic reactions has not been well studied in spite of the potentials expected from the two different transition metals contained in the solid oxide. Recently, we reported a selective sulfoxidation of allylic sulfides catalyzed by the trirutile-type solid oxide, LiNbMoO6 and successfully applied the oxidation method to the synthesis of Lansoprazole. Because of the good catalytic activity shown by the LiNbMoO6 in the sulfoxidation of sulfides, we decided to test other trirutile-type solid oxides, AMM’O6 (A=H, Li, M=Nb, Ta, M’=Mo, W), as a catalyst in the hydrogen peroxide oxidation of sulfides to sulfoxides (Eq. 1).

The hopcalite (CuMnOx) catalyst is a well-known catalyst for oxidation of CO at ambient temperature. It has prepared by co-precipitation method and the preparation parameters were like Copper/Manganese (Cu:Mn) molar ratios, drying temperature, drying time, calcination temperature and calcination time has an influence on activity of the resultant catalyst. The activity of the catalyst was measured in flowing air calcinations (FAC) conditions. The reaction temperature was increased from ambient to a higher value at which complete oxidation of CO was achieved. The particle size, weight of catalyst and CO flow rate in the air were also influenced by the activity of the catalyst for CO oxidation. The characterizations of the catalysts were done by several techniques like XRD, FTIR, BET, SEM-EDX and XPS. These results were interpreted in terms of the structure of the active catalyst. The main aim of this paper was to identify the optimum preparation conditions of CuMnOx catalyst with respect to the performance of catalyst for CO oxidation.

Respirometric characterization of aerobic sulfide, thiosulfate and elemental sulfur oxidation by S-oxidizing biomass

Voltammetry study of electrocatalytic activity of lanthanum nickel perovskite nanoclusters-based composite catalyst for effective oxidation of urea in alkaline medium

Microbiology and geochemistry in a hydrogen-sulphide-rich karst environment

New effective catalysts based on mesoporous nanofibrous carbon for selective oxidation of hydrogen sulfide

Hydrogen sulphide emission control by combined adsorption and catalytic combustion

Corrosion of concrete sewers—The kinetics of hydrogen sulfide oxidation

Several animals from hydrogen sulfide‐rich marine habitats were found to contain unusual heme compounds (hematins) at levels of up to 10 mM; these hematins catalyzed the oxidation of sulfide and may protect the animals from sulfide poisoning. Freshly captured specimens of the echiuran worm Urechis caupo contained 0–10 mM hematin in their coelomic fluid. This hematin was present within coelomocytes in addition to 0.5–2 mM hemoglobin present in these cells as a functional oxygen‐binding hemoprotein. The hematin was present in granules, and was not associated with a globin, cytochrome, or other protein known to have a heme prosthetic group. The hematin catalyzed oxidation of hydrogen sulfide. Further studies revealed that similar hematins were present in gill tissues of bivalve molluscs, which harbor vast numbers of endosymbiotic sulfur bacteria. Hematin was found at 1.0 mM, in addition to 0.1 mM hemoglobin, in the gill tissue of the clam Solemya reidi. Hematin was also found at 1–2 mM in gill tissue of two other clams, Calyptogena magnifica and Lucinoma annulata, in addition to < 0.4 mM hemoglobin. These clam hematins also appeared to be catalysts of sulfide oxidation.

The effect of the calcination temperature on the properties of supported iron oxide catalysts for hydrogen sulfide oxidation prepared by impregnation of silica with iron(III) nitrate has been studied. An increase in the calcination temperature was found to diminish the catalytic activity of the Fe2O3/SiO2 catalysts in hydrogen sulfide oxidation. This behavior can be explained by the agglomeration of iron oxide particles and by a decrease in the surface concentration of active sites. It has been shown that an increase in the calcination temperature makes the catalyst more stable towards the sulfidation of the active component (Fe2O3) to the iron disulfide phase.

The name Goshikinuma means a lake or pond having five colors. Actually, Lake Matsuo-Goshikinuma has had three distinct colors, namely, a heavily turbid brown hue, a slightly turbid, pale blue, and a clear blue. This phenomenon was accounted for as follows : The lake was supplied solely with underground water from the bottom, containing ferrous iron, hydrogen sulfide, but no dissolved oxygen. In the colder seasons from September to June, the lake water was in the circulation period and, therefore, was supplied with oxygen. Both ferrous iron and hydrogen sulfide in the water were continuously oxidized and gave a turbid brown color to the lake. In July, the lake was in the early stagnation stage, and dissolved oxygen decreased. Then, oxidation of some hydrogen sulfide but no ferrous iron had occurred. Thus, the lake color turned a slightly turbid, pale blue. In August, oxidation of neither ferrous iron nor hydrogen sulfide occurred as a result of stagnation, and the lake hue became a clear blue. It was also noticed that oxidation of ferrous iron was quite dependent on the activity of iron-oxidizing bacteria.

Keggin-type polyoxometalates/Amberlite nanocomposites as efficient catalysts for the aqueous oxidation of sulfides: Crucial roles of mono-iron and mono-manganese substituents