María L. Martínez

Hydrogenation of Tetralin Over Ir Catalysts Supported on Titania-Modified SBA-16

Abstract A series of Ti modified SBA-16 supports and their respective Ir-catalysts were prepared and characterized to study the effect of support preparation method on the dispersion of iridium and on the characteristics of Ir surface species. Two methods of incorporation of titania were tested: the sol–gel method in order to obtain Ti as heteroatom and incipient wetness impregnation to obtain Ti as TiO2 (anatase phase). The results show that supports with different Ti species and dispersion can be obtained. The final catalyst was characterized at different preparation stages by XRD, elemental analysis and BET. The presence of Ti as Ti4+ in the nanostructure of SBA and as TiO2 (anatase phase) was analyzed by UV–Vis–DRS and Raman spectroscopy. The iridium oxidation sate upon Ti-containing SBA-16 was studied by XPS, EDX, TEM and XRD, arriving at the good proportion of Ir0. H2 chemisorption and TEM characterization for Ti-SBA-16 indicated that Ir particle size was lower than anatase/SBA-16. The catalyst that we synthesized had good activity measured in tetralin hydrogenation in presence of quinoline at mild conditions. The experimental data were quantitatively represented by a modified Langmuir–Hinshelwood-type rate equation. The preliminary results show these materials as promising catalysts for HDS/HDN reactions.Graphical Abstract

Hydroxyapatite/MCM-41 and SBA-15 Nano-Composites: Preparation, Characterization and Applications

Composites of hydroxyapatite (HaP) and highly ordered large pore mesoporous silica molecular sieves such as, Al-SBA-15 and Al-MCM-41 (denoted as SBA-15 and MCM-41, respectively) were developed, characterized by XRD, BET, FTIR, HRTEM and NMR-MAS, and applied to fluoride retention from contaminated water. The proposed procedure by a new route to prepare the HaP/SBA-15 and HaP/MCM-41, composites generates materials with aluminum only in tetrahedral coordination, according to the 27Al NMR-MAS results. Free OH- groups of HaP nanocrystals, within the hosts, allowed high capacity fluoride retention. The activity of fluoride retention using HaP/MCM-41 or HaP/SBA-15 was 1-2 orders of magnitude greater, respectively, than with pure HaP.

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.

Utilidad del citrato de galio 67 en el diagnóstico de fiebre de origen desconocido

Resumen Se presenta el caso de un paciente con cuadro de 4 meses de evolucion de fiebre intermitente, perdida no cuantificada de peso y diaforesis nocturna. El examen fisico revelo hepatoesplenomegalia sin otras alteraciones. Los estudios iniciales mostraron anemia macrocitica-hipocromica, y las serologias para VIH, hepatitis B y hepatitis C fueron negativas. La TAC de cuello reporto adenomegalias cervicales subcutaneas bilaterales; a una de ellas se le tomo una biopsia, que resulto negativa para malignidad o infeccion. El objetivo de este reporte es ilustrar la utilidad del 67Gacitrato en el estudio de la fiebre de origen desconocido.