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

MARTÍNEZ, MARIA L.; CAMPOS-MARTIN, JOSE M.; RIVOIRA, LORENA P.; BELTRAMONE, ANDREA R.; TARTAJ, PEDRO; FALCÓN, HORACIO; FIERRO, JOSE L.G.

ACS Omega

American Chemical Society

Lugar: Chicago; Año: 2017 p. 2351 - 2359

Mesocrystals (basically nanostructures showing alignment of nanocrystals well beyond crystal size) are attracting considerable attention for modelling 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 the 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 underatmospheric 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 (ca. 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 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 catalytic activity. Furthermore, the most active mesocrystals have been used to model the catalytic reaction in three- and two-phase 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 estimate an apparent activationenergy for the oxidative desulfuration reaction of around 40 kJ/mol. Our results clearly stablish that TiO2(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 to the one here studied.