Anatase nanoparticles boundaries resulting from titanium tetrachloride hydrolysis

Clean Synthesis of Ti-MWW by Utilizing the Recycled Mother Liquor

This article introduces a clean and efficient method for the synthesis of Ti-MWW by utilizing the recycled mother liquor. The effects of titanium and silicon sources on the synthesis of Ti-MWW and the recycling of the mother liquor are discussed in detail. Precipitated silica prepared with Na₂SiO₃ and CO₂ was selected as the silicon source, and TiCl₃ was selected as the titanium source. The mother liquor was recycled five times, and the obtained samples showed good catalytic activity in cyclohexanone ammoximation. This work can be conducive to reducing the influence on the environment and economizing on materials for the industrial production of Ti-MWW.

Morphology control of anatase TiO2 for well-defined surface chemistry

Surface hydroxyls of titanium dioxide (anatase) are studied by infrared spectroscopy, density functional theory and nuclear magnetic resonance. They are found to be dependent on morphology and fluoride content.

Probing the Catalytic Activity of Sulfate-Derived Pristine and Post-Treated Porous TiO2(101) Anatase Mesocrystals by the Oxidative Desulfurization of Dibenzothiophenes

Mesocrystals (basically nanostructures showing alignment of nanocrystals well beyond crystal size) are attracting considerable attention for modeling and optimization of functionalities. However, for surface-driven applications (heterogeneous catalysis), only those mesocrystals with excellent textural properties are expected to fulfill their potential. This is especially true for oxidative desulfuration of dibenzothiophenes (hard to desulfurize organosulfur compounds found in fossil fuels). Here, we probe the catalytic activity of anatases for the oxidative desulfuration of dibenzothiophenes under atmospheric pressure and mild temperatures. Specifically, for this study, we have taken advantage of the high stability of the (101) anatase surface to obtain a variety of uniform colloidal mesocrystals (approximately 50 nm) with adequate orientational order and good textural properties (pores around 3-4 nm and surface areas around 200 m²/g). Ultimately, this stability has allowed us to compare the catalytic activity of anatases that expose a high number of aligned single crystal-like surfaces while differing in controllable surface characteristics. Thus, we have established that the type of tetrahedral coordination observed in these anatase mesocrystals is not essential for oxidative desulfuration and that both elimination of sulfates and good textural properties significantly improve the catalytic activity. Furthermore, the most active mesocrystals have been used to model the catalytic reaction in three-(oil-solvent-catalyst) and two-phase (solvent-catalyst) systems. Thus, we have been able to observe that the transfer of DBT from the oil to the solvent phase partially limits the oxidative process and to estimate an apparent activation energy for the oxidative desulfuration reaction of approximately 40 kJ/mol in the two-phase system to avoid mass transfer limitations. Our results clearly establish that (101) anatase mesocrystals with excellent textural properties show adequate stability to withstand several post-treatments without losing their initial mesocrystalline character and therefore could serve as models for catalytic processes different from the one studied here.