The continuous-flow preparation of biodiesel using a commercially available scientific microwave apparatus offers a fast, easy route to this valuable biofuel. The methodology allows for the reaction to be run under atmospheric conditions and performed at flow rates of up to 7.2 L/min using a 4 L reaction vessel. It can be utilized with new or used vegetable oil with methanol and a 1:6 molar ratio of oil/alcohol. Energy consumption calculations suggest that the continuous-flow microwave methodology for the transesterification reaction is more energy-efficient than using a conventional heated apparatus.

Exceptionally high hydrogen permselectivity, exceeding that of any polymeric or porous inorganic systems, is achieved using an ionically crosslinked multilayer polymer thin film.

The kinetics of phenylacetylene hydrogenation over Pt/γ-Al 2 O 3 catalyst was investigated using stirred semibatch reactors over a range of temperatures, pressures, and initial phenylacetylene concentrations. Analysis verified that the results were obtained in the absence of transport limitations. Equations for the rates of change for phenylacetylene, styrene, and ethylbenzene were derived from a system of elementary reactions and tested against experimental data. The model was found to accurately predict rate dependencies on catalyst weight, initial concentration, and pressure. The kinetic parameters were determined by minimizing the error between the model predictions and the experimental results, and the obtained activation energy values compared favorably with those reported in the literature.

In this paper, the authors present the first demonstration of a liquid-tin anode solid-oxide fuel cell (LTA-SOFC) operating on pure biodiesel (B100) prepared via base-catalyzed transesterification of virgin and waste cooking oils. The LTA-SOFC was able to convert the biodiesel to electricity at commercially viable power densities, i.e., greater than 100 mW cm−2. The peak power for each cell was 3.5 W over an active area of 30 cm−2, which translates to a power density of 117 mW cm−2 and current density of 217 mA cm−2. The peak power densities correspond to ∼80% fuel use at the liquid-tin anode surface and overall cell efficiencies of >40%. These findings demonstrate the flexibility in operating a solid-oxide fuel cell capable of internal reforming from a blend of petroleum- and biomass-derived diesels for greater resource flexibility. Cells were operated for short times (∼4.5 h), owing to the experimental nature of the balance of plant. Results support future efforts in developing an efficient balance-of-plant system for demonstrating long-term (>1000 h) power generation from biodiesel using the LTA-SOFC design.

The performance of a perforated micromembrane device employing thin palladium-based films for hydrogen purification is reported. The perforated support provides mechanical strength, allowing the use of nanometer film thicknesses (200 nm) that significantly reduce internal diffusion resistance, and allows efficient heating of the active film. Steady-state operation of pure and 23 wt % silver-alloyed palladium films at 350 °C, with a feed hydrogen partial pressure of 10.1 kPa (∆p H 2 ) 9.6 kPa), results in hydrogen fluxes of 3-4 mol/m 2 /s and hydrogen-to-argon selectivities approaching 1000:1, much larger fluxes than typically achieved with conventional macroscopic equipment. Chemical resistance to ammonia, carbon dioxide, and carbon monoxide is also reported. Ammonia and carbon dioxide are both found to have a minimal effect upon the device performance. Exposure to carbon monoxide results in a loss of hydrogen permeation, with silver-palladium films showing a partially recoverable loss of ∼40% initial hydrogen flux at a carbon monoxide concentration of 9000 ppm. Our results demonstrate that these microdevices could be part of an integrated portable hydrocarbon to electrical power system.

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Our pre®ious theoretical work predicted the possibility of enhancing three-phase packed-bed reactor performance by operating in the pulsing-flow regime. This article deals with the experimental study of the beneficial effect of pulsing flow on reaction outcome. Hydrogenation of phenylacetylene, dissol®ed in n-tetradecane o®er Ptralumina catalyst, was chosen as the experimental reaction system. This is a triangular reaction, with styrene and ethylbenzene as the desired intermediate and final products, respecti®ely. With properly designed experiments, the reaction performance in pulsing flow and trickling-flow regimes was compared directly. The effects of process ®ariables such as temperature, feed flow rates, and reactant concentration on reaction beha®ior were studied. A simplified model to describe the qualitati®e trends was also de®eloped. Both experiments and calculations show that the yield of styrene is higher in pulsing flow than in trickling flow, which confirms the ad®antages of pulsing-flow operation predicted by the theoretical work. IntroductionMultiphase reactions, in which gas and liquid reactants are selectively converted into desired products using solid catalysts, provide the basis for a large number of chemical, petro-Ž chemical, biochemical, and polymer processes Mills et al., . 1992;Dudukovic et al., 1999 . A common configuration for carrying out such reactions is a three-phase packed bed reactor, involving a stationary packed-bed of catalyst over which gaseous and liquid reactants flow in either a cocurrent or countercurrent manner. Due to complexity of this type of operation, many factors influence reactor behavior. These include liquid distribution, contacting efficiency and partial wetting, which have received prior attention in the literature ŽJiang et al. 1999;Al-Dahhan and Dudukovic, 1995; Watson . and Harold, 1994 . In cocurrent three-phase packed-bed reactors, four major flow regimes have been identified: trickling flow, pulsing flow, Ž . spray flow, and bubble flow Ng and Chu, 1987 , depending on factors such as gas and liquid flow rates, physical properties, and the nature of the reactor packing. These flow regimes Ž . result in different behavior such as holdup and transport Correspondence concerning this article should be addressed to A. Varma. Current address of R. Wu: Novartis Pharma, 59 Route 10, East Hanover, NJ 07936. around the catalyst, which could affect the overall reaction outcome. Specifically, when the reactor is operated in puls-Ž . ing-flow regime, liquid-rich slug pulse and gas-rich slug Ž . base regions are formed, and they move down the column alternatingly. The strong interactions between the phases within the pulses result in significant enhancement in overall Ž mass and heat transfer rates Blok and Drinkenburg, 1982; . Chou et al., 1979 , and be enhanced by operating the reactor in pulsing-flow regime and that optimization is possible by ''tuning'' the pulsing frequency prudently.In the present work, an experimental demonstration of the beneficial effe...

In an effort to impart light gas (i.e., H2 and He) barrier to polymer substrates, thin films of polyethylenimine (PEI), poly(acrylic acid) (PAA), and montmorrilonite (MMT) clay are deposited via layer-by-layer (LbL) assembly. A five "quadlayer" (122 nm) coating deposited on 51 μm polystyrene is shown to lower both hydrogen and helium permeability three orders of magnitude against bare polystyrene, demonstrating better performance than thick-laminated ethylene vinyl-alcohol (EVOH) copolymer film and even metallized polyolefin/polyester film. These excellent barrier properties are attributed to a "nanobrick wall" structure. This highly flexible coating represents the first demonstration of an LbL deposited film with low hydrogen and helium permeability and is an ideal candidate for several packaging and protection applications.