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The use of solid oxygen carriers (SOCs) in catalytic dehydrogenation may provide a more efficient production process for small alkenes by shifting the equilibrium to the product side. In this paper we use dynamic simulations to investigate the feasibility of two-step oxidative dehydrogenation of propane to propene using a SOC. The proposed process is carried out in a cyclically operated fixed-bed reactor, filled with a mixture of a dehydrogenation catalyst and a SOC. In the first step (the dehydrogenation), propane is fed to the reactor. The SOC oxidises the hydrogen produced during the dehydrogenation. In the second step, the SOC is regenerated and the accumulated coke burned off by allowing oxygen into the reactor. We determine the cyclic steady states by simulating the process for different feed temperatures and SOC concentrations, and we show that addition of a SOC to a reactor filled with dehydrogenation catalyst increases the conversion of propane and enhances the selectivity towards propene.

Stable nanoclusters (~2 nm in diameter) of copper, silver, gold, palladium, and ruthenium coated with hydrophobic coronas are easily trapped in self-assembled “soft crystal” hexagonal phase gels made of water and surfactants. The system's crystal structure and phase behavior are studied in detail. A partial phase diagram showing the hexagonal phase region for the water/SDS/toluene region is presented. High-energy X-ray scattering and cross-polarized optical microscopy experiments show that the clusters are tightly confined within the tubes. The thermal gel−fluid transitions of the hexagonal phase are investigated, and it is shown that the hexagonal phase can melt and recrystallize repeatedly. The melt/gel cycles enable easy trapping of various metal clusters in pre-prepared hexagonal phases. In contrast to spherical micelles, the hexagonal phase doped with metal clusters can grow without limit, basically up to the container walls (Ru-doped soft crystals grew to 0.5 mm over 2 months, forming wormlike tubes that are more than 50 μm long but only 7−10 nm in diameter).

Heterogeneous Pd-catalyzed coupling reaction of substituted halobenzenes to biphenyls is performed effectively in different organic solvents using an alcohol as the reducing agent in the presence of a base and a catalytic amount of phase-transfer (PT) agent. The alcohol is oxidized to the respective aldehyde or ketone. Kinetic studies show that the reaction rate equation fits to second order in halobenzene. The effects of reaction temperature, catalyst loading, base concentration, PTC concentration, and alcohol concentration and structure are studied and discussed.

A novel concept for the preparation of hydroxide compounds using liquid/liquid anion exchange is presented. The exchange is accomplished by loading a chemical potential into a liquid organic membrane and subsequently releasing it from the membrane using an onium−alcoholate complex as the potential carrier. Accordingly, this method requires no electricity and no energy input other than a concentration gradient. The influence of the alcohol concentration and structure on the extraction equilibrium is studied. Alcohol acidity and stabilization of the alcoholate−quat ion pair are the key factors in determining the transfer efficiency. For example, diols are good coextractants, probably as a result of intramolecular hydrogen bonding that stabilizes the complex. The synthetic application of this concept to make CsOH, LiOH, KOH, and water-soluble tetraalkylonium hydroxides is examined. The extraction mechanism and the function of the organic membrane as a one-way transport medium and a “water pump” are discussed.

Vanadium pentoxide, V2O5, catalyses the two-electron oxidation of Br^- to Br⁺, using aqueous hydrogen peroxide under dilute acidic conditions. In this system, kinetic studies show that HBr can be replaced with a combination of an alkali bromide salt (NaBr, KBr) and a dilute mineral acid (e.g., HCl, H2SO4, HNO3, H3PO4). The salt/acid/peroxide system may be used for in situ or ex situ oxidative bromination, e.g. of various aromatic compounds. The application of the above concept towards the recycling of industrial acid waste is discussed. The cost effectiveness, E factors, and hazard factors for several bromination and oxidative bromination reagent systems are compared.

Kinetics and process parameters of coupling and hydro-dehalogenation reactions of chloroaryls are studied in the presence of zinc, water, and catalytic Pd/C. Good yields are obtained for the coupling of chlorobenzene, 4-chlorotoluene, and 4-chloro-1,1,1-trifluorotoluene. It is shown that water is actually one of the reagents, reacting with zinc in the presence of palladium to give zinc oxide and hydrogen gas, which then regenerates the Pd⁰ catalyst for the coupling reaction.

The nanophase material (powder) of Ce0.9W0.1O2 was synthesized via coprecipitation of oxalates of cerium (IV) and tungsten cations. Pt-Ce0.9W0.1O2 (2 wt% Pt) was prepared by an alcohol-reduction process using H2PtCl6.6H2O as source of Pt, Ce0.9W0.1O2 as support and ethylene glycol as solvent and reducing agent. Pt-Ce0.9W0.1O2 was physically mixed with commercial Pt/C E-TEK (20 w% Pt) to produce the Pt-(2%Pt-Ce0.9W0.1O2)/C electrocatalyst. The prepared electrocatalysts were characterized by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and CO stripping. The performances of Pt/C E-TEK and Pt-(2%Pt-Ce0.9W0.1O2)/C electrocatalysts were tested in single fuel cell fed with a mixture H2/CO (100 ppm of CO). The results showed that the mixture of 2%Pt-Ce0.9W0.1O2 and Pt/C E-TEK increases the CO tolerance in a single fuel cell operating at 85 ºC compared with Pt/C E-TEK.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.