Andrea R. Beltramone

Synthesis of menadione over selective oxidation zeolites

Abstract We report on the synthesis of Menadione (vitamin K 3 ) by selective oxidation of 2-methylnaphthalene (2MN) with hydrogen peroxide over Ti- and Fe-containing catalysts. Different parameters affecting the oxidation of 2-methylnaphthalene with hydrogen peroxide on zeolite Fe-Beta are described. The influence of the amount of catalyst as well as the concentration of hydrogen peroxide and the influence of the reaction temperature on the reaction rate were studied. The effect of the nature of the solvent was also investigated. All tests were performed over several selective oxidation zeolitic catalysts, synthesized and characterized in our laboratory.

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

AbstractnA 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.

Novel Preparation of Titania-Modified CMK-3 Nanostructured Material as Support for Ir Catalyst Applied in Hydrodenitrogenation of Indole

Iridium catalyst was prepared using a novel titanium oxide-CMK-3 support synthesized as a replica of Ti-SBA-15. The catalyst was applied in the hydrodenitrogenation of indole. The activity was compared with an iridium catalyst supported over a grafted titanium-CMK-3. Structural and textural characterization of the catalysts was performed by means of N2 adsorption, XRD, UV–Vis–DRS, Raman spectroscopy, XPS, TEM and H2 Chemisorption. Ir-Ti-CMK-3 was the most active catalyst for the hydrodenitrogenation reaction at mild conditions. Titanium oxide contained in carbon ordered mesoporous CMK-3 promotes a very good anchorage of iridium metallic clusters in the carbon framework reaching high active site distribution and more stable nanoclusters.Graphical Abstract

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.

Synthesis, characterization and catalytic activity of selective oxidation zeolites catalysts

Zeolites TS-1,TS-2,VS-1, Ti-NCL, TiBEA and FeBEA were synthesized via a new procedure, the sol-gel method. The samples were characterized by FT-IR spectroscopy, BET surface area, pyridine adsorption, XRD-synchrotron, temperature programmed desorption of the template, and were tested in the hydroxylation of benzene to phenol, oxifunctionalization of n-hexane, epoxidation of 1-hexene, selective transformation of toluene to benzaldehyde and oxidation of 2- methylnaphthalene into 2-methyl-1,4-naphthoquinone. The results showed the incorporation of Ti, V and Fe into the framework and high crystallinity of the catalytic materials. Special attention was paid to sol-gel method using raw amorphous SiO2/Heteroatoms Oxide xerogels.

Kinetic studies on diacetyl synthesis over V-containing zeolites

The gas-phase oxidation of methyl ethyl ketone (MEK) was studied on V-ZSM-5 zeolite in the presence of molecular oxygen. Two types of competitive partial oxidations, i.e., diacetyl formation and oxidative scission reaction leading to acetaldehyde and acetic acid, took place at 200–350°C. A detailed kinetic study was realized for the oxidation reaction, a linear relationship was observed between the conversion and partial pressure of oxygen, and an activation energy of 16 kcal/mol was encountered. The content of vanadium in the catalyst was also analyzed.

Studies on the synthesis of diacetyl over oxidation zeolite catalysts

Diacetyl (2,3-butanedione) synthesis from methyl ethyl ketone over oxidation zeolites using O2 as oxidant was studied. Various zeolites with Fe, V and Ti as active sites were employed. VS-1, Ti-NCL, Ti-MCM-41 and FeBEA type materials were synthesized and characterized by BET, FTIR, XRD, pyridine adsorption and template desorption. The detailed study of the effect of reaction temperature, the effect of concentration of oxygen and the addition of water was realized. The most active catalyst was zeolites with V as oxidation center.

Synthesis of 2,3-Butanedione over TS-1, Ti-NCl, TiMCM-41, Ti-Beta, Fe-Si, Fe-Beta and VS-1 Zeolites

The purpose of this work is the synthesis of 2,3-butanedione (diacetyl) by selective oxidation of 2-butanone (methyl ethyl ketone) in the presence of O2 and H2O2 30% as oxidants. All the tests were performed over several selective oxidation zeolite catalysts, synthesized and characterized in our laboratory.