Characterization of crosslinked,macroporous, monosized polymer particles

Macroporous, monosized poly(meta‐divinylbenzene) and poly(para‐divinylbenzene) beads have been prepared by the two‐step activated swelling method with toluene or 2‐ethylhexanoic acid as pore‐forming agents. The type of divinylbenzene isomer as well as the type of porogen has a large effect on both physical and chemical properties of the monodisperse beads. Large pores are obtained with 2‐ethylhexanoic acid as porogen while beads prepared in the presence of toluene consist of only small pores and exhibit a shrinking behavior upon drying. The beads have considerable amounts of residual vinyl groups at the end of polymerization, as determined by bromination and Fourier transform IR analysis. The morphology and texture of the particles have been investigated by scanning electron microscopy and atomic force microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 152–169, 2000     

Ru@Pt core–shell nanoparticles for methanol fuel cell catalyst: Control and effects of shell composition

The present work presents a method to encapsulate pre-synthesised Ru nanoparticles (NPs) by Pt using a polyol method without capping agents at various pH values (6, 7, 8 and 10). The structural and surface properties of the catalysts were characterised using X-ray diffraction, transmission electron microscopy, CO stripping, and energy-dispersive X-ray spectroscopy. The studies suggest that the pH during encapsulation of Ru by Pt plays an important role in controlling of shell composition. A core–shell catalyst with an alloy shell was obtained at a pH of 6, whereas a monometallic Pt shell was obtained at a pH of 10. The core–shell catalysts gave higher steady-state current for methanol oxidation: 10-fold higher for alloy shells and 5-fold higher for Pt-enriched shells compared to the pure Pt catalyst. It is suggested that the highest catalytic enhancement of the core–shell catalysts is obtained through the bi-functional character that dominates the alloy shells rather than the ligand-effect-promoted Pt-enriched shells.     

A liquefied energy chain for transport and utilization of natural gas for power production with CO2 capture and storage – Part 3: The combined carrier and onshore storage

A novel energy and cost effective transport chain for stranded natural gas utilized for power production with CO₂ capture and storage is developed. It includes an offshore section, a combined gas carrier and an integrated receiving terminal. The combined carrier will transport liquid carbon dioxide (LCO₂) and liquid nitrogen (LIN) outbound, where natural gas (NG) is cooled and liquefied to LNG by vaporization of LIN and LCO₂ onboard the carrier. The same carrier is used to transport the LNG onshore, where the NG can be used for power production with CO₂ capture. The combined carrier consists of 10 cylindrical tanks with a diameter of 9.2 m and varying lengths from 14 to 40 m. The total ship volume is 13,000 m³. Assuming 85% capture rate of the CO₂, the maximum ship utilization factor (SUF) is 63.4%. Due to the combined use of the storage tanks, the SUF is decreased with 1.4% points to 62%. The ship is equipped with a bi-directional submerged turret loading for anchoring and loading of NG and unloading of CO₂. Two ships can deliver NG to and remove CO₂ from a 400 MW_net power plant, and still obtain continuous production of LNG offshore without intermediate storage. The investment cost for each gas carrier is 40 million EUR giving total transport cost of 16.9 EUR/tonne LNG. The cost for the offshore transfer system is 6.6 million EUR per tonne LNG, whereas the cost for onshore storage and loading system is 3.1 and 0.8 million EUR per tonne LNG, respectively. The total specific costs for the ship transport, including onshore storage, loading shipping and offshore unloading are 27.5 EUR per tonne LNG for a roundtrip of 5 days, including voyage, production of LNG, unloading, connecting and berthing.     

Survey of air pollution in Cotonou, Benin--air monitoring and biomarkers

Exposure to genotoxic compounds present in ambient air has been studied in Cotonou, Benin, a city where two-stroke motorbikes are the major form of transportation and gasoline quality is poor. Personal monitoring and biomarkers were used to assess the exposure. Non-smoking taxi-moto drivers (city) and village residents were the study subjects. Benzene exposure was significantly higher in the city, as compared to the village (76.0+/-26.8 microg/m(3) versus 3.4+/-3.0, p=0.0004). Urinary excretion of benzene and S-phenylmercapturic acid (S-PMA) were also highest in subjects living in the city, whereas 1-hydroxypyrene was not different. The level of total polycyclic aromatic hydrocarbons (PAHs), associated with particles, ranged from 76.21 to 103.23 in Cotonou versus 1.55 ng/m(3) for the village. Determination of DNA damage in lymphocytes showed that subjects from the city had elevated number of lesions compared to subjects in the village in terms of bulky DNA adducts, 8-hydroxy-2'-deoxyguanosine and 5-methylcytosine, whereas DNA fragmentations analysed by alkaline gel electrophoresis was not different between the subjects. In conclusion, this study shows that air pollution is pronounced in Cotonou, Bénin and is associated with elevated levels of DNA damage in residents of the city compared to people living in a non-polluted rural village.     

Difference points in reactive and extractive cascades: IV—Feasible regions for multisection columns with kinetic reactions and side streams

The feasibility of three component distillation columns containing kinetically controlled chemical reactions and side streams is addressed through the use of difference points. We decompose complex columns into sections and identify feasible regions in composition space where each section operates. These regions enclose sectional profiles for the full range of operating parameters and are bounded by profiles constructed under extreme conditions. We efficiently determine the bounding profiles without computing interior compositions. We also develop a graphical feasibility test to connect sections and construct full columns using feasible regions. Finally, we present a technique to characterize the feasible regions and quantify how much reaction or side stream may be placed on any stage of a column section. The first three papers in this series [Hauan et al., 2000. Difference points in extractive and reactive cascades. I—Basic properties and analysis. Chemical Engineering Science 55 (16) 3145–3159; Lee et al., 2000. Difference points in extractive and reactive cascades. II—Generating design alternatives by the lever rule for reacting systems. Chemical Engineering Science 55 (16) 3161–3174; Hoffmaster and Hauan, 2004. Difference points in extractive and reactive cascades. III—Properties of column section profiles with arbitrary reaction distribution. Chemical Engineering Science 59 (17) 3671–3693] derive the fundamental properties of difference points, develop a lever rule to facilitate full column design, and analyze the properties of sectional profiles in reactive cascades. This fourth paper develops the necessary feasibility analysis tools for systematic identification of reactive distillation design alternatives.     

Deposition of Au colloids on plasmachemically modified carbon nanofibers

The surface properties of fishbone (FB) carbon nanofibers (CNFs) were altered. This was achieved by H₂O-plasma treatment (FB-plasma) and oxidation in HNO₃ (FB-HNO₃). By zeta-potential measurements, the surfaces of as-grown and acid treated CNFs were found to be negatively charged at all pHs. Meanwhile, basic entities were introduced by H₂O-plasma treatment, indicated by an isoelectric point of pH 4.6. Ultraviolet-visible measurements indicated the successful deposition of negatively charged Au colloids on FB-plasma, and incomplete deposition on FB-HNO₃. The nature of the basic sites accommodating colloid deposition is discussed based on X-ray photoelectron spectroscopy (XPS) results. The XPS study indicated significant differences in the type and amount of surface groups. Also, a variation in the fraction of defect and/or edge sites was found. The possible sites responsible for colloid immobilization are discussed based on the XPS results. Plasma treatment is demonstrated as a simple and effective procedure for altering the surface characteristics of CNFs.     

Cryogenic helium gas circulation system for advanced characterization of superconducting cables and other devices

A versatile cryogenic test bed, based on circulating cryogenic helium gas, has been designed, fabricated, and installed at the Florida State University Center for Advanced Power Systems (FSU-CAPS). The test bed is being used to understand the benefits of integrating the cryogenic systems of multiple superconducting power devices. The helium circulation system operates with four sets of cryocooler and heat exchanger combinations. The maximum operating pressure of the system is 2.1 MPa. The efficacy of helium circulation systems in cooling superconducting power devices is evaluated using a 30-m-long simulated superconducting cable in a flexible cryostat. Experiments were conducted at various mass flow rates and a variety of heat load profiles. A 1-D thermal model was developed to understand the effect of the gas flow parameters on the thermal gradients along the cable. Experimental results are in close agreement with the results from the thermal model.     

Flowsheet simulation of aqueous two‐phase extraction systems for protein purification

BACKGROUND: Aqueous two‐phase extraction (ATPE) has many advantages as an efficient, inexpensive large‐scale liquid–liquid extraction technique for protein separation. However, the realization of ATPE as a protein separation technology at industrial scales is rather limited due to the large, multidimensional design space and the paucity of design approaches to predict phase and product behavior in an integrated fashion with overall system performance. This paper describes a framework designed to calculate suitable flowsheets for the extraction of a target protein from a complex protein feed using ATPE. The framework incorporated a routine to set up flowsheets according to target protein partitioning behavior in specific ATPE systems and a calculation of the amounts of phase‐forming components needed to extract the target protein. The thermodynamics of phase formation and partitioning were modeled using Flory‐Huggins theory and calculated using a Gibbs energy difference minimization approach. RESULTS: As a case study, suitable flowsheets to recover phosphofructokinase from a simple model feedstock using poly(ethylene glycol)‐dextran (PEG6000‐DxT500) and poly(ethylene glycol)‐salt (PEG6000‐Na₃PO₄) two‐phase systems were designed and the existence of feasible solutions was demonstrated. The flowsheets were compared in terms of product yield, product purity, phase settling rate and scaled process cost. The effect of the mass flowrates of phase‐forming components on product yield and purity was also determined. CONCLUSION: This framework is proposed as a basis for flowsheet optimization for protein purification using ATPE systems. Copyright © 2010 Society of Chemical Industry     

Hydrogen from natural gas without release of CO2 to the atmosphere

The “Hydrogen economy”, in which hydrogen will be a main carrier of energy from renewable sources, is a long term prospect. In the near and medium term increasing demand for hydrogen--also as an energy carrier in special niches--will probably be covered by hydrogen from fossil sources, mainly natural gas. This can be acceptable from an environment as well as an economical point of view, since hydrogen can be produced from natural gas at acceptable costs, without release of CO₂ to the atmosphere. There are two main options for this: (1) hydrogen from natural gas by conventional technology (e.g. steam reforming) including CO₂ sequestration; (2) high temperature pyrolysis of natural gas, yielding pure hydrogen and carbon black. Technologies for industrial scale realisation of these options have been developed and evaluated in Norway, which is a large producer and exporter of natural gas. The economy and market opportunities are discussed in the paper. It appears that renewable energy costs must come down considerably from present levels before hydrogen from renewables can compete with hydrogen from natural gas without release of CO₂ to the atmosphere.