Removal of dibenzothiophene by extraction and catalytic oxidation using long- and short-channel SBA-15 containing Zr and Mo species

Two different SBA-15 silicas with long and short channels, containing zirconium species, were prepared and used as supports for molybdenum additives. The resulting materials were characterized and tested as catalysts for extractive catalytic oxidative desulfurization (ECODS) of dibenzothiophene (DBT) using acetonitrile as a solvent and H2O2 as an oxidant. The synthesis procedure for the zirconium-containing silicas influenced both the zirconium loading and its distribution, i.e., whether it was incorporated into the framework or present in extra-framework positions. Additionally, the choice of support for molybdenum inclusion affected the amount of modifier loaded and its resistance to leaching, which collectively impacted the acidic and basic properties of the synthesized catalysts. The textural and surface properties of the materials were evaluated using low-temperature nitrogen adsorption/desorption, XRD, SEM-EDS, FT-IR-ATR, XPS, and UV-vis. The acidity and basicity of the samples were evaluated using FT-IR spectroscopy with pyridine adsorption/desorption and test reactions including 2-propanol dehydration/dehydrogenation and 2,5-hexanedione cyclization/dehydration. The catalytic activity was measured in ECODS. The Mo/ZrSBA-15-S catalyst demonstrated the best performance in DBT removal from the oil phase, achieving approximately 92% conversion of DBT within 120 minutes at 60 °C. This superior activity was attributed to the material's high acidity strength.

SBA-15 Type Mesoporous Silica Modified with Vanadium as a Catalyst for Oxidative and Extractive Oxidative Desulfurization Processes

One of the current challenges is the reduction of sulfur emitted into the atmosphere, usually in the form of sulfur oxides generated by fossil fuel combustion. To achieve this goal, the sulfur content should be reduced in fuel. In this context, vanadium-containing materials based on SBA-15 mesoporous silica supports and two different sources of vanadium were prepared, characterized, and applied as catalysts for oxidative desulfurization (CODS) and extractive oxidative desulfurization processes (ECODSs). The novelty of this work was the comparative study of vanadium-containing materials in two desulfurization systems. The properties of the catalysts, the concentration and state of vanadium species, and their role in the catalytic process were examined by low-temperature nitrogen physisorption, XRD, UV-Vis, XPS, and chemisorption of pyridine combined with FTIR spectroscopy. The catalytic performance of the material prepared using ammonium metavanadate was superior to that of the catalyst obtained using vanadium(IV) oxide sulfate, which was explained by a higher concentration of vanadium species on the surface of the support and their lower oxidation state in the former. Both types of catalysts showed high activity and stability in the ECODS process.

Improving bioelectrochemical performance by sulfur-doped titanium dioxide cooperated with Zirconium based metal-organic framework (S-TiO2@MOF-808) as cathode in microbial fuel cells

The sulfur-doped titanium dioxide (S-TiO2) cooperated with Zirconium based on a kind of metal-organic framework (MOF-808) was successfully prepared as cathode catalyst (S-TiO2@MOF-808) of microbial fuel cell (MFC) by two-step hydrothermal reaction. The particle size was approximately 5 μm, and the spherical S-TiO2 particle was attached to the surface of MOF-808 as irregular block solid. Zr-O, C-O and O-H bond were indicated to exist in S-TiO2@MOF-808. When n (Zr4+): n(Ti4+) was 1: 5, S-TiO2@MOF-808 showed better oxygen reduction reaction (ORR). The introduction of S-TiO2 restrained the framework collapse of MOF-808, S-TiO2@MOF-808 showed much higher catalytic stability in reaction. The recombination of sulfur and TiO2 reduced the charge transfer resistance, accelerated the electron transfer rate, and improved ORR greatly. The maximum power density of S-TiO2@MOF-808-MFC was 84.05 mW/m2, about 2.17 times of S-TiO2-MFC (38.64 mW/m2). The maximum voltage of S-TiO2@MOF-808-MFC was 205 mV, and the stability was maintained for 6 d.

The Effect of Mesoporous Structure of the Support on the Oxidation of Dibenzothiophene

A source of Brønsted acid centers, generated on the surface of two mesoporous silica supports of different structures (SBA-15 and MCF), was 3-(trihydroxysilyl)-1-propanesufonic acid (TPS). The materials obtained were characterized and applied as catalysts for the oxidative desulfurization of dibenzothiophene (DBT) with hydrogen peroxide as a model ODS (oxidative desulfurization) process. The properties of the materials were examined via nitrogen physisorption, XRD (X-ray Diffraction) and elemental analysis showing the preservation of the support structure after modification with organosilane species. Due to the aggregation of catalyst particles in the reaction mixture, the SBA-15 based catalyst was not very effective in DBT oxidation. Contrary, TPS/MCF catalyst exhibited a very good activity (almost total conversion of DBT after 1 h in optimized reaction conditions) and stability in dibenzothiophene oxidation in mild reaction conditions.