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

Abstract

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 m 2 /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.

TiO2 Nanostructures as Anode Materials for Li/Na‐Ion Batteries

“…To improve the performance of Li‐ion cells based on TiO 2 ‐electrodes, in our group we started a research line focused on the synthesis of mesoporous TiO 2 nanostructures with controlled crystallinity (mesocrystals), size and excellent textural characteristics. To achieve this objective, we developed an original synthetic procedure that combines thermally‐driven self‐assembly of nanomicelles with seeded assisted chemistry and a two‐stage temperature program ,. The scheme of the synthesis route is shown in Figure a.…”

“…More specifically, we have highlighted our work on TiO 2 anatase mesocrystals with colloidal size and excellent textural properties. The design and development in our group of a versatile methodology for the preparation of mesocrystals have allowed us: 1) to advance in the comprehension on how anatase anodes work and 2) to optimize the electrochemical response of these unique nanostructures (porous mesocrystals can be considered as single crystals with nanocapabilities) in conventional alkyl carbonates electrolytes as well as in safe electrolytes based on ionic liquids ,. As the main drawback of TiO 2 ‐based anodes is their intrinsically low electronic conductivity, which seriously limit their rate performances, future developments on open nanostructures must be based for example on the combination of these sophisticate morphologies with carbon‐coating or the synthesis of TiO 2 ‐composites with carbon‐based matrices.…”

Selective vapor‐phase oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H3PW12O40@TiO2 using molecular oxygen as a green oxidant

“…As shown in Figure , the studied XPS detailed regions were Ti 2p, W 4d, Co 2p, Mn 2p and O 1 s. The XPS of Ti 2p levels for the all samples are presented in Figure a which show the doublet arising from spin‐orbit splitting Ti 2p 3/2 and Ti 2p 1/2 . The analysis of the Ti 2p 3/2 level (more intense signal) shows the binding energy value at 458.7 eV that is typical of Ti 4+ whereas, in the reused Co‐Mn/HPW@TiO 2 catalyst after 5 th run, it shifted to 459.1 eV. The XPS spectrum in Figure b shows the most intense W 4d 5/2 component of the W 4d doublet at a binding energy of 247.5 eV which confirms the oxidation state of +6 (W 6+ ) for tungsten in the catalysts.…”

“…Finally, we must mention that the analysis of the O 1 s core levels (see Figure S2) reveals a peak at 530.2 eV assigned to oxygen bound to metallic ions (mainly Ti 4+ ) except in reused Co‐Mn/HPW@TiO 2 after 5 th run where the region is dominated by higher binding energy components (531.5 eV) corresponding to organic oxygen (bound to carbon) and commonly to OH from hydroxyl ions …”

Adsorption oxidation desulfurization of model fuel by mesoporous SiO2 supported deep eutectic solvents TBAB/PEG-200

“…In order to solve the problem of sulfur pollution, researchers have proposed desulfurization solutions generally including precombustion, during combustion, and post combustion according to different processes. [1][2][3] At present, the mature desulfurization method precombustion is the hydrodesulfurization (HDS) technology of petroleum. [4][5][6][7] HDS showed a great removal effect for low molecular weight mercaptan, sulfide, and hydrogen sulfide.…”