Factors controlling the selectivity of V2O5 supported catalysts in the oxidative dehydrogenation of propane

The surface properties of a series of V₂O₅ catalysts supported on different oxides (Al₂O₃, H–Na/Y zeolite, MgO, SiO₂, TiO₂ and ZrO₂) were investigated by transmission electron microscopy and FTIR spectroscopy augmented by CO and NH₃ adsorption. In the case of the V₂O₅/SiO₂ system TEM images evidenced the presence of V₂O₅ crystallites, whereas such segregated phase was not observed for the other samples. VO_x species resulted widely spread on the surface of Al₂O₃, H–Na/Y zeolite, MgO and SiO₂, whereas on TiO₂ and ZrO₂ they are assembled in a layer covering almost completely the support. Furthermore, evidences for the presence in this layer of V–OH Brønsted acid sites close to the active centres were found. It is proposed that propene molecules primarily produced by oxydehydrogenation of propane can be adsorbed on this acid centres and then undergo an overoxidation by reaction with redox centres in the neighbourhood. This features could account for the low selectivity of V₂O₅/TiO₂ and V₂O₅/ZrO₂ catalysts.     

Intrazeolite Pd clusters: particle location

A chemical vapour deposition (CVD) procedure has been adopted for the preparation of Pd/NaY, resulting in a high dispersion of the metal phase, characterised by a bimodal distribution of particle size. The most abundant particles (80%) are about 25 Å in size, corresponding to almost twice the dimension of the zeolitic supercages. To identify their location inside or outside the zeolite matrix, the IR spectra of adsorbed CO, obtained before and after admission of NH₃, have been compared. The results obtained are in sharp contrast with those for a Pd/SiO₂ system, where Pd particles of comparable size are exclusively located on the external surface of the carrier. These differences support the conclusion that Pd particles in Pd/NaY are indeed located in the zeolitic cavities.     

CO oxidation over CuOx-CeO2-ZrO2 catalysts: Transient behaviour and role of copper clusters in contact with ceria

The effects of ZrO₂ content on the CO oxidation activity in a series of CuO_x/Ce_xZr_1−xO₂ (x = 0, 0.15, 0.5, 0.7 and 1) catalysts were investigated, both in the absence and in the presence of H₂, i.e. preferential CO oxidation—PROX. The investigation was performed under light-off conditions to focus the effects of transients and shut-down/start-up cycles on the performance; such phenomena are expected to affect the activity of PROX catalysts in small/delocalised fuel reformers. Evidence has been obtained for a transition from an “oxidized” towards a “reduced” state of the catalyst under the simulated PROX reaction conditions as a function of the reaction temperature, leading to different active species under the reaction conditions. Both CO oxidation activity and PROX selectivity appear to be affected by this process. IR characterisation of the surface copper species suggests an important role of reduced cerium sites in close contact with copper clusters on the CO oxidation activity at low temperatures.     

Local Structures of Active Sites on Ti-MCM-41 and Their Photocatalytic Reactivity for the Decomposition of NO

The characterization of mesoporous Ti-MCM-41 prepared at ambient temperature, with Ti contents in the 0.15–2.00?wt% range, was carried out using XAFS, FT-IR and photoluminescence methods. For Ti contents up to 0.60?wt%, isolated tetrahedrally coordinated Ti-oxide species was found to be formed in the MCM-41 network structures, while at higher titanium contents, dimeric or oligomeric Ti-oxide species, with Ti (IV) in tetrahedral coordination, became overwhelming. It was found that only the highly dispersed isolated tetrahedrally coordinated Ti-oxide species act as active sites in the photocatalytic decomposition of NO into N₂ and O₂.     

FTIR Study of Cobalt Containing Aluminophosphates with Chabasite Like Structure by Using CO and NO as Molecular Probes

FTIR spectroscopy of adsorbed molecules such as CO and NO was used to monitor the nature of cobalt centres in Co-containing aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs) with chabasite-like structures. The samples were synthesized by following a facile route during which the cobalt ions were directly inserted in the synthesis gels. These studies show that Co²⁺ ions are located in framework positions in CoAPO-34, where they substitute for some Al³⁺ ions, whilst in CoAPSO-34, where Si⁴⁺ ions replacing for some phosphorous lead to negative charges in the aluminophosphate framework, are contemporarily present both in framework and extra-framework positions. It is likely that, in the latter case, some cobalt ions act as counter ions compensating the negative structure.     

Efficacy of 5-FU Combined to Na[trans-RuCl(4)(DMSO)Im], A Novel Selective Antimetastatic Agent, on the Survival Time of Mice With P388 Leukemia, P388/DDP subline and MCa Mammary Carcinoma

The combinational treatment between the selective antimetastatic agent, sodium-trans-rutheniumtetrachloridedimethylsulfoxideimidazole, Na[trans-RuCl(4)(DMSO)Im], and the cytotoxic drug 5-fluorouracil (5-FU) on primary tumor growth and on the survival time of experimental tumors results in an effect significantly greater than that of each single agent used alone either with the solid metastasizing MCa mammary carcinoma of the CBA mouse or with the lymphocytic leukemia P388 and its platinum resistant P388/DDP subline. Thus the inorganic compound Na[trans-RuCl(4)(DMSO)Im], known for its potent and selective antimetastatic effects, positively interacts with the antitumor action of an organic anticancer agent such as 5-FU on both a solid metastasizing tumor and a tumor of lymphoproliferative type. In particular, the effects of the combinational treatment on the survival time of tumor bearing mice seem to be related to the selective antimetastatic activity of the ruthenium complex that joins the potent cytotoxicity of 5-FU for the tumor. Moreover, these data show that Na[trans-RuCl(4)(DMSO)Im] is almost as effective on the subline of P388 made resistant to cisplatin as it was on the parental line.     

Kinetic Investigation of the Photocatalytic Reduction of Nitric Oxide by Carbon Monoxide at Low Pressure on Silica-Supported Molybdenum Oxide

The kinetics of photoinduced reactions that occur upon UV irradiation (<360 nm) of a MoO₃/SiO₂ catalyst (2.5 wt% Mo) in CO-NO mixtures and CO alone are studied at gas pressures from 0.05 to 2 torr and for CO/NO ratios from 0.3 to 3.0 in the temperature interval 20-150C. The data obtained are consistent with a previously proposed two-stage redox mechanism. In the first stage NO is reduced to N₂O through the reaction CO+2NO CO₂+N₂O, while in the second stage the N₂O formed is further reduced to N₂ via the reaction CO+N₂O CO₂+N₂. The ratio of rate constants for quenching of a transient excited state (Mo⁵⁺-O^-)* by NO and CO molecules is found to be 2.8. The reaction rates decrease with increasing temperature, apparently because of a lower concentration of adsorbed species and/or a reduction of the steady-state concentration of (Mo⁵⁺-O^-)*.     

The Role of Mechanochemistry in the Pulmonary Toxicity Caused by Particulate Minerals

The release of free radicals from mechanically ground mineral dusts in aqueous suspensions has been employed to predict the possible pathogenic potential of the dusts when inhaled. Two separate free radical-generating reactions have been considered: formation of the OH radical from hydrogen peroxide via a "Fentonlike" reaction and of a carbon centered radical, following cleavage of a carbon–hydrogen bond. The particulate examined were: variously contaminated quartz dusts, whose well-documented pathogenicity varies from one to the other source; iron- and titanium-doped alumina pigments, prepared via a mechanochemical reaction, whose pathogenic potential is unknown, and hard metal mixtures, obtained from tungsten carbide (WC) and one metal dust, namely Fe, Co, or Ni, the cobalt mixture only being a renown hazardous material. Quartz obtained by grinding coarse particles in grinding chambers composed of steel, widia, corundum, and agate, retain some characteristics of the wall chamber material, which deeply affects its capability to generate radicals and may explain the variability of quartz hazard. Insertion of ions in the mechanochemically prepared pigments imparts to the particle suspected free radical-generating properties. Among the hard metal mixtures examined, the most active is the cobalt one.     

Sulfonamide Inhibitors of β-Catenin Signaling as Anticancer Agents with Different Output on c-MYC

The Wnt/β-catenin pathway is often found deregulated in cancer. The aberrant accumulation of β-catenin in the cell nucleus results in the development of various malignancies. Specific drugs against this signaling pathway for clinical treatments have not been approved yet. Herein we report inhibitors of β-catenin signaling of potential therapeutic value as anticancer agents. Ethyl 4-((4-(trifluoromethyl)phenyl)sulfonamido)benzoate (compound 14 ) inhibits the effect on Wnt reporter with an IC₅₀ value of 7.0 μM, significantly reduces c-MYC levels, inhibits HCT116 colon cancer cell growth (IC₅₀ 20.2 μM), does not violate Lipinski and Veber rules, and shows predicted Caco-2 and MDCK cell permeability P_app>500 nm s⁻¹. Compound 14 seems to have potential for the development of new anticancer therapies.