Vanadium oxide supported on porous clay heterostructure for the partial oxidation of hydrogen sulphide to sulfur

A review on sensitivity of operating parameters on biogas catalysts for selective oxidation of Hydrogen Sulfide to elemental sulfur

Hydrogen sulfide (H₂S) is a critical problem for biogas applications, such as electricity and heat generation, or the production of different chemical compounds, due to corrosion and toxic effluent gases. The selective catalytic oxidation of H₂S to S is the most promising way to eliminate H₂S from biogas due to the lack of effluents, therefore can be considered a green technology. The most extensively used catalysts for H₂S selective oxidation can be classified in two groups: metal oxide-based catalysts, including vanadium and iron oxides, and carbon-based catalysts. Numerous studies have been devoted to studying their different catalytic performances. For industrial applications, the most suitable catalysts should be less sensitive to the operating parameters like the temperature, O₂/H₂S ratio, and H₂O content. More specifically, for metal oxides and carbon-based catalysts, the temperature and O₂/H₂S ratio have a similar effect on the conversion and selectivity, but carbon-based catalysts are less sensitive to water in all operating conditions.

The Prospects of Clay Minerals from the Baltic States for Industrial-Scale Carbon Capture: A Review

Carbon capture is among the most sustainable strategies to limit carbon dioxide emissions, which account for a large share of human impact on climate change and ecosystem destruction. This growing threat calls for novel solutions to reduce emissions on an industrial level. Carbon capture by amorphous solids is among the most reasonable options as it requires less energy when compared to other techniques and has comparatively lower development and maintenance costs. In this respect, the method of carbon dioxide adsorption by solids can be used in the long-term and on an industrial scale. Furthermore, certain sorbents are reusable, which makes their use for carbon capture economically justified and acquisition of natural resources full and sustainable. Clay minerals, which are a universally available and versatile material, are amidst such sorbents. These materials are capable of interlayer and surface adsorption of carbon dioxide. In addition, their modification allows to improve carbon dioxide adsorption capabilities even more. The aim of the review is to discuss the prospective of the most widely available clay minerals in the Baltic States for large-scale carbon dioxide emission reduction and to suggest suitable approaches for clay modification to improve carbon dioxide adsorption capacity.

Hybrid Hosts Based on Sodium Alginate and Porous Clay Heterostructures for Drug Encapsulation

In this study, some hybrid materials based on sodium alginate (NaAlg) and porous clay heterostructures (PCHs) were investigated as new hosts for 5-Fluorouracil (5-FU) encapsulation. The hybrid hosts were prepared by ionotropic gelation technique using different concentrations of PCHs (1, 3, and 10 wt%) in order to identify the optimal parameters for encapsulation and drug release. The obtained hybrid materials were characterized using FTIR Spectrometry, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and UV-Vis spectrometry to investigate the interactions of the raw materials involved in the preparation of hybrid hosts, the influence of PCHs concentrations on drug encapsulation efficiency and drug release profile. All the results show that the synthesized hybrid materials were able to load a high amount of 5-FU, the encapsulation efficiency and the release profile being influenced by the concentrations of PCHs.

Precise control of heat-treatment conditions to improve the catalytic performance of V2O5/TiO2 for H2S removal

The purpose of this study is to investigate the influences of atmospheric gas and temperature while preparing V₂O₅/TiO₂ catalysts to find a suitable heat-treatment method to improve catalytic performance during the process of H₂S removal. The catalysts prepared by wet-impregnation were heat-treated at different temperatures (400 or 600 ℃) under various atmospheres (Air, N₂, or H₂). The catalytic tests demonstrated that the catalyst heat-treated at 400 ℃ under N₂ atmosphere (N-400) possessed excellent catalytic activities regarding H₂S conversion (96.4%) and sulfur yield (89.1%). The characterization results revealed that the mild reducing condition employed for N-400 led to the formation of partially reduced V₂O₅ crystals and a strong V-Ti interaction owing to the anatase TiO₂ phase, resulting in the high oxygen vacancies on the catalyst surface. However, severe reducing conditions (H₂ or N₂ with 600 ℃) or the higher temperature (600 ℃) induced highly reduced V₂O_5-x or rutile TiO₂ related to a weak V-Ti interaction, respectively, which facilitated lower oxygen vacancies. This study is the first to demonstrate the significance of a precisely controlled heat-treatment to enhance catalytic performance for H₂S removal.

Adsorption of Salmonella in Clay Minerals and Clay-Based Materials

A series of clay minerals and clay-based materials have been tested to eliminate one of the most dangerous bacteria we can find in the water: Salmonella. It has been proven that the use of clays and their PCH materials can be a suitable method for removing Salmonella from water. The results of this initial study show that all the materials analyzed have great salmonella adsorption capacities ranging from the lowest value observed in the mont-PCH sample (0.29 × 1010 CFU g−1) to the highest value observed in the natural palygorskite sample (1.52 × 1010 CFU g−1). Macroporosity, accessible external surface area, and the presence of silanol groups in the external surface of the particles appears to be the controlling factors for Salmonella adsorption capacity while it seems that the structural characteristics of the clay minerals and their respective PCH does not affect the adsorption capacity.

Selective Oxidation of Hydrogen Sulfide to Sulfur Using Vanadium Oxide Supported on Porous Clay Heterostructures (PCHs) Formed by Pillars Silica, Silica-Zirconia or Silica-Titania

Vanadium oxide (V₂O₅) species has been supported on different porous clay heterostructures (with silica pillars, silica-zirconia with a molar ratio Si/Zr = 5 and silica-titania with a molar ratio Si/Ti = 5) by wetness incipient method. All catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption at −196 °C, NH₃ thermoprogrammed desorption (NH₃-TPD), Raman spectroscopy, diffuse reflectance UV-Vis and X-ray photoelectron spectroscopy (XPS). After that, the catalytic activity of the vanadium-based catalysts was evaluated in the selective oxidation of H₂S to elemental sulfur. The catalytic data show that both the activity and the catalytic stability increase with the vanadium content, obtaining the highest conversion values and sulfur yield for the catalysts with vanadium content of 16 wt.%. The comparison among all supports reveals that the incorporation of TiO₂ species in the pillars of the PCH improves the resistance to the deactivation, attaining as best results a H₂S conversion of 89% for SiTi-PCH-16V catalyst and elemental sulfur is the only compound detected by gas chromatography.

Minireview: direct catalytic conversion of sour natural gas (CH4 + H2S + CO2) components to high value chemicals and fuels

Direct sour natural gas catalytic conversion allows to obtain high value products, such as hydrocarbon and organosulfur chemicals, fuels and fertilizers.

Partial oxidation of ethylbenzene by H2O2 on VOx/HZSM-22 catalyst

Highly dispersed extra-framework vanadium species mainly led to the oxidation of EB with 17.5% yield and 72.5% selectivity to AP.