The influence of organic additives on the regioselectivity of oxygenation of alkanes with hydrogen peroxide in the presence of TS-1titanium silicalite

Hydrogen peroxide oxidizes n-hexane, n-heptane, and n-octane at 50°C in the presence titanium silicalite TS-1 as a catalyst, forming isomeric mixtures of ketones and alcohols. Admixtures of organic acids, alcohols, benzene, and ethylbenzene sharply change the ratio of position isomers. For example, the normalized ratio is C(4): C(3): C(2) = 0.44: 1.0: 0.47 for n-heptane oxidation in the absence of additives, but it becomes 0.52: 1.0: 1.00 in the presence of benzyl alcohol and the addition of ethylbenzene changes it to 0.16: 1.0: 0.94.     

Hydrophobic Zeolite‐Filled Polymeric Films with High Ethylene Permselectivity for Fresh Produce Packaging Applications

Gas permselective plastic films have been in a great deal of attention in the area of modified atmosphere packaging of fresh produces. Such films must allow transport of the respiring gases, i.e. oxygen and carbon dioxide, in a controlled manner and, moreover, should efficiently remove ethylene gas. Therefore, the development of highly permeable films with high ethylene permselectivity, i.e. high in both permeability and selectivity, was carried out. The concept of ‘mixed matrix membrane’, by which enhanced gas permselectivity can be obtained by incorporation of zeolite particles into the polymeric film, was applied. Fine particles of hydrophobic zeolites, i.e. zeolite beta and ZSM‐5, and the surface‐modified zeolites were used in this study. The films with uniform distribution of zeolite particles (10% w/w) in 70LDPE/30SEBS (styrene‐b‐(ethylene‐ran‐butylene)‐b‐styrene block copolymer) matrix can be prepared by blow film extrusion. Significantly high ethylene permselectivity, i.e. ethylene permeability of 1.78–2.67 × 10³ cm³ ? mm/m² ? day ? atm and ethylene/O₂ selectivity of 4.67–8.26, was obtained from the films containing octyl‐modified and phenyl‐modified zeolites. Particular enhancement was observed on the films containing phenyl‐modified zeolites. Crystallinity of polyethylene, transition temperatures and decomposition temperature were, however, indifferent among the studied films. Nevertheless, elongation at break and toughness of the films containing surface‐modified zeolites were superior. Particle–polymer interface could thus be improved. Copyright © 2014 John Wiley & Sons, Ltd.     

Kinetics and mechanism of hydrogenation of furfural on Cu/SiO2 catalysts

The hydrogenation/hydrodeoxygenation of furfural was studied on a Cu/SiO₂ catalyst at 230–290 °C. Detailed kinetics, density function (DFT) calculations, and spectroscopic studies were combined to investigate this reaction. A Langmuir–Hinshelwood model was found to fit the kinetic data well and provided the parameters of physical significance. The heat of adsorption (ΔH_ads) of furfural, derived from the fitting, was found to be significantly higher than those of furfuryl alcohol and 2-methyl furan. Activation energies for the conversion of furfural and furfuryl alcohol were both about 12 kcal/mol. DFT calculations and DRIFTS provided guidance about the nature of the surface species. Accordingly, the most likely species adsorbed on the Cu surface is suggested to be a top η¹(O)-aldehyde. DFT calculations of the reaction path show that the predicted energy barriers are of the same order as the experimental values and suggest that the hydrogenation of furfural can occur via either an alkoxide or ahydroxyalkyl intermediate.     

Connecting GEON: Making sense of the myriad resources,researchers and concepts that comprise a geoscience cyberinfrastructure

Simply placing electronic geoscience resources such as datasets, methods, ontologies, workflows and articles in a digital library or cyberinfrastructure does not mean that they will be used successfully by other researchers or educators. It is also necessary to provide the means to locate potentially useful content, and to understand it. Without suitable provision for these needs, many useful resources will go undiscovered, or else will be found but used inappropriately. In this article, we describe an approach to discovering, describing and understanding e-resources based on the notion that meaning is carried in the interconnections between resources and the actors in the cyberinfrastructure (including individuals, groups, organizations), as well as by ontologies and conventional metadata. Navigation around this universe is achieved by implementing the idea of perspectives as dynamic, conceptual views (defined by SPARQL-like queries against an OWL schema) that not only act as filters, but also dynamically promote and demote concepts, relationships and properties according to their immediate relevance. We describe a means to represent a wide variety of interactions between resources using the notion of a knowledge nexus, and we illustrate its use with resources and actors from the Geosciences Network (GEON) cyberinfrastructure community. We also closely link browsing and visualizing strategies to our nexus, drawing on ideas from semiotics to move resources and connections not currently of interest from the foreground to the background, and vice versa, using a new form of adaptive perspective. We illustrate our ideas via ConceptVista, an open-source concept mapping application that provides rich, visual depictions of the resources, cyber-community and myriad connections between them. Examples are presented that show how geoscientific knowledge can be explored not only via ontological structure, but also by use cases, social networks, citation graphs and organization charts; all of which may carry some aspects of meaning for the user.     

Tin oxide thin films deposited by ultrasonic spray pyrolysis

This study investigated microstructure of SnO₂ thin films deposited by ultrasonic spray pyrolysis technique using 0.2 M of SnCl₄·5H₂O in absolute ethanol as a precursor. The deposition temperature (350–450 °C) and time (20–90 min) were varied. The influence of film-deposition conditions on grain size and orientation were discussed. The deposited SnO₂ films were textured polycrystalline films. The preferred orientation of SnO₂ films were quantitatively evaluated by texture coefficient (TC). The mean grain size and film thickness determined by SEM could be controlled over a range of 50–325 nm and 80–2690 nm, respectively.     

Oxidation of Saturated Hydrocarbons to Alkyl Hydroperoxides by a ‘H2O2/Titanosilicalite-1/NaOH/MeCN’ System

Hydrogen peroxide oxidizes alkanes at room temperature to produce the corresponding alkyl hydroperoxides in the presence of titanosilicalite-1, NaOH and acetonitrile. The reaction proceeds with low regio- and bond-selectivity and its mechanism apparently involves the formation of hydroxyl radicals.     

Selective ethylene‐permeable zeolite composite double‐layered film for novel modified atmosphere packaging

The composite double‐layered films, for the packaging application of postharvest fruits and vegetables, were prepared by laminating low‐density polyethylene (LDPE) and poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) modified with zeolite ZSM‐5. The film was characterized by scanning electron microscope and differential scanning calorimeter and tested for permeation of ethylene (C₂H₄), oxygen (O₂), carbon dioxide (CO₂), and water vapor. It was found that the C₂H₄ permeability of the films was improved because of an enhanced adsorption of C₂H₄ by the incorporated zeolite (0–10 wt%). The preconcentrated layer (zeolite/SEBS) leads to a higher C₂H₄ concentration gradient across the film. Moreover, the high dispersion of zeolite increased the C₂H₄ permeation. When compared with O₂ and CO₂, the composite films were more selective to C₂H₄. However, the C₂H₄ permeation decreased in the presence of O₂ because of a competitive adsorption. In addition, the films possessed appreciate tensile properties for packaging application. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers