Influence of WO3 Content in Phosphated Tungsten-Zirconium Oxide Catalysts on the Catalytic Pathways of Glycerol Transformation

The catalytic performance of phosphate-stabilized WOx-ZrO2 compositions in gas-phase glycerol dehydration has been investigated. Results show that varying WO3 concentrations direct the process towards either acrolein or allyl alcohol formation. Catalysts with low WOx content exhibit strong Lewis acid sites (Zr4+ and W6+), where these metal ions likely function as redox sites, facilitating glycerol hydrogenolysis to produce allyl alcohol. Higher WOx concentrations (exceeding 20 wt %) lead to the shielding of some W6+ and Zr4+ sites by polytungstate surface complexes, which are strong Brønsted acid sites. This alteration promotes glycerol dehydration through the removal of two water molecules, thereby shifting the selectivity towards acrolein formation.

Amphoteric composite of ZrP and N-doped porous carbon: Synthesis, characterization, and potential use for cycloaddition of CO2

Composites of amorphous ZrP and N-doped carbon were prepared in a one-step pyrolysis process instead of general post-loading technique. Owing to their mesoporous structure (6-10 nm) and Zr content (up to 41 wt%), the amphoteric materials have potential use in the cycloaddition of CO2 to epoxides, which is an acid‒base tandem process including the ring opening of epoxides and the addition of CO2. Substantial work has been done on how starting materials impact the structure and performance of composite materials. The coordination between metal and melamine has been confirmed, and it can be implanted in the melamine-polymer initiation of formation of porous metal-carbon materials. The composite catalysts exhibit amphoteric properties, present broad-spectrum adsorption, and finally produce carbonates via cycloaddition of CO2 to epoxides. It is remarkable that the multiple characteristics of porous solids are stabilized, and no significant loss of catalytic performance is observed after four cycles.

Tungsten-Based Catalysts for Environmental Applications

This review aims to give a general overview of the recent use of tungsten-based catalysts for wide environmental applications, with first some useful background information about tungsten oxides. Tungsten oxide materials exhibit suitable behaviors for surface reactions and catalysis such as acidic properties (mainly Brønsted sites), redox and adsorption properties (due to the presence of oxygen vacancies) and a photostimulation response under visible light (2.6–2.8 eV bandgap). Depending on the operating condition of the catalytic process, each of these behaviors is tunable by controlling structure and morphology (e.g., nanoplates, nanosheets, nanorods, nanowires, nanomesh, microflowers, hollow nanospheres) and/or interactions with other compounds such as conductors (carbon), semiconductors or other oxides (e.g., TiO2) and precious metals. WOx particles can be also dispersed on high specific surface area supports. Based on these behaviors, WO3-based catalysts were developed for numerous environmental applications. This review is divided into five main parts: structure of tungsten-based catalysts, acidity of supported tungsten oxide catalysts, WO3 catalysts for DeNOx applications, total oxidation of volatile organic compounds in gas phase and gas sensors and pollutant remediation in liquid phase (photocatalysis).

An efficient ordered mesoporous molybdate-zirconium oxophosphate solid acid catalyst with homogeneously dispersed active sites: Synthesis, characterization and application

Ordered mesoporous molybdate-zirconium oxophosphate (M-ZrPMo) solid acid catalysts with controllable molybdenum contents (0-20%) are designed and synthesized through a one-pot evaporation-induced self-assembly strategy. Afterwards, ordered mesostructure and molybdenum species in the materials are systematically researched by a variety of means. The results show that M-ZrPMo has highly ordered mesoporous structure with large specific surface area (∼200 m²·g^-1), big pore volume (∼0.30 cm³·g^-1) and pore size (∼6.5 nm). Additionally, ordered mesoporous structure of M-ZrPMo can be efficiently preserved even treated at 700 °C, presenting an outstanding thermal stability. Meanwhile, the molybdenum species are introduced as designed and homogeneously dispersed in mesoporous framework even at molybdenum content up to 20%. More importantly, the Brønsted and Lewis acidic properties of these materials are successfully enhanced with the introduction of molybdenum species. Meantime, the M-ZrPMo is employed as a solid acid catalyst for alkylation of aromatic compounds and esterification of levulinic acid with 1-butanol. The effect of molybdenum contents and calcination temperature on catalytic performance is thoroughly discussed. The excellent activity and reusability suggested that M-ZrPMo is a promising solid acid catalyst.