Single component equilibrium and uptake of methane and nitrogen in barium exchanged ETS-4, Ba-ETS-4, have been measured in a constant volume apparatus over a wide range of temperatures and pressures followed by binary measurements in a differential adsorption bed at some selected conditions. Similar binary data in two strontium exchanged samples have also been included for which unary data were earlier reported from our laboratory. Adsorbent particles used in these measurements were obtained by pressure-binding very fine crystals of Ba-ETS-4 synthesized in this laboratory, thus giving rise to a bidispersed pore structure with the controlling resistance to diffusion in the micropores. The effect of dehydration temperature on equilibrium and kinetics of aforementioned gases in Ba-ETS-4 has also been investigated. The uncoupled kinetic selectivity of nitrogen over methane in Ba-ETS-4 measured in this study far exceeds the selectivity reported for methane−nitrogen separation in other adsorbents in the literature. Kinetic selectivity including the coupling of equilibrium isotherm and uptake has also been calculated from binary measurements and is found to be equally encouraging. The impact of isotherm models on the concentration dependence of micropore diffusivity has been analyzed on the basis of chemical potential gradient as the driving force for diffusion. Binary equilibrium and kinetic models based on parameters independently established from unary experiments have been proposed that are able to explain the transport mechanism and capture the essential features of measured binary data.
Carbon dots were used as a reducing agent for the synthesis of Pd nanoparticles coated with ultrathin carbon dot shells of ca. 4 nm. The resulting composite nanoparticles showed high catalytic activity for the Heck and Suzuki coupling reactions.
A heterogeneous, inexpensive, and environmentally friendly carbocatalyst, graphene oxide (GO) enables the formation of α-ketoamides from activated aldehydes and amines through a cross-dehydrogenative coupling pathway. The oxygenated functionalities (e.g., carboxyl, hydroxyl, ketonic, and epoxides) on the surface of graphene oxide impart acidic as well as oxidizing properties to the material. This dual catalytic property of graphene oxide is explored toward the generation of α-ketoamides where surface acidity of graphene oxide favors the initial formation of hemiaminal intermediate followed by oxidation leading to the desired final product. The hemiaminal intermediate could be isolated and confirmed by NMR and mass analysis. A few control experiments confirmed that both acidic and oxidizing catalytic activities of graphene oxide were instrumental in the coupling reaction. Use of benzoic acid and p-toluene sulfonic acid as catalysts resulted in the formation of only hemiaminal intermediate as the major product along with a trace amount of α-ketoamide. As these catalysts do not possess oxidative catalytic capability, the formation of ketoamide was not favorable. However, use of GO as the catalyst could generate the ketoamide product from the hemiaminal intermediate as initial acid-catalyzed hemiaminal formation was followed by oxidation to α-ketoamide. Graphene oxide annealed at different temperatures demonstrates the role of oxygenated functional groups in the catalytic reaction. Further investigation of catalytic activity with modified GO surfaces using various conditions, such as base, acid, or NaBH 4 , showed carboxylic acid groups on the surface to be the active site for the catalytic reaction. The method is also effective toward the synthesis of biologically important α-ketoamide.
Herein, we report the fluorescent carbon dots as an effective and recyclable carbocatalyst for the generation of carbon-heteroatom bond leading to quinazolinone derivatives and aza-Michael adducts under mild reaction conditions. The results establish this nanoscale form of carbon as an alternative carbocatalyst for important acid catalyzed organic transformations. The mild surface acidity of carbon dots imparted by -COOH functionality could effectively catalyze the formation of synthetically challenging spiro/glycoquinazolinones under the present reaction conditions.
The development of carbonaceous materials as metal-free catalysts integrating different types of catalysis in a single system represents a significant advance in cascade/tandem organic synthesis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.