Effect of Chemisorption and Physisorption of Water on the Surface Structure and Stability of alpha-Alumina

Chemisorption and physisorption of water onto the {0001}, {1011}, {1120}, and {2243} surfaces of alpha-alumina have been studied via atomistic simulation techniques, using potentials that have been verified against the structures of hydrated ß-alumina and diaspore. Both physisorption and chemisorption of all surfaces are energetically favorable, especially the hydroxylation of dipolar oxygen-terminated planes. The equilibrium morphology is calculated, as a way to assess the change in surface energies, and the equilibrium morphologies agree with the experimentally observed crystal morphologies. The calculated energies of both physisorption and chemisorption agree well with experimentally obtained hydration energies.     

Hydrogenation of fatty acid methyl esters to fatty alcohols at supercritical conditions

Extremely rapid hydrogenation of fatty acid methyl esters (FAME) to fatty alcohols (FOH) occurs when the reaction is conducted in a substantially homogeneous supercritical phase, using propane as a solvent, over a solid catalyst. At these conditions, the limitations of hydrogen transport are eliminated. At temperatures above 240°C, complete conversion of the starting material was reached at residence times of 2 to 3 s, which is several orders of magnitude shorter than reported in the literature. Furthermore, formation of by-products, i.e., hydrocarbons, could be prevented by choosing the right process settings. Hydrogen concentration turned out to be the key parameter for achieving the above two goals. As a result of the supercritical conditions, we could control the hydrogen concentration at the catalyst surface independently of the other process parameters. When methylated rapeseed oil was used as a substrate, the hydrogenation catalyst was deactivated rapidly. However, by using methylated sunflower oil, a catalyst life similar to that obtained in industrial processes was achieved. Our results showed that the hydrogenation of FAME to FOH at supercritical conditions is a much more efficient method than any other published process.     

Influence of geometry and solids concentration on the hydrodynamics and mass transfer of a rectangular airlift reactor for marine sediment and soil bioremediation

Hydrodynamics and mass transfer characteristics of a three-phase airlift reactor were studied in a rectangular split-vessel reactor and using an air-seawater-marine sediment system. Experiments were conducted over a range of downcomer to riser cross-sectional area ratios (A_D/A_R = 0.65 to 1.0) for two-phase systems and for five sediment concentrations (5 to 25% w/v) using marine sediments. The influence of higher sediment concentrations (30 to 50% w/v) was examined for A_D/A_R = 1. The presence of fine sediment particles in the system had little effect on hydrodynamic and mass transfer parameters compared to the two-phase systems up to 25% loading, decreasing at higher loadings. The airlift reactor was found to meet the dissolved oxygen demand needed for a contaminated sediment treatment process. Axial distribution of the particles was uniform along the riser and the downcomer. Correlations were developed that described the hydrodynamic and mass transfer behaviour for all experimental conditions examined.     

Aromatic and hetero-aromatic compositional changes during catalytic hydrotreatment of shale oil

Oil shale from the Kimmeridge Clay, of Jurassic age from the UK was pyrolysed in a 5 kg fixed bed reactor at 525°C in a nitrogen atmosphere. The derived shale oil was then hydrotreated at 15.0 Mpa pressure and 400°C in a stirred reactor with a nickel–molybdenum (Ni–Mo) catalyst and residence times from 8 to 56 h. The shale oils were analysed for polycyclic aromatic hydrocarbons (PAH) and for nitrogen-PAH (PANH) and sulphur-PAH (PASH), before and after hydrotreatment. The results showed that generally the higher molecular weight three and four ring PAH decreased with increasing hydrotreatment time, however, single ring aromatic compounds and two ring PAH were increased. Nitrogen and sulphur containing PAH were significantly reduced in concentration in the oils with increasing hydrotreatment time to reach negligible concentrations after 56 h. The reduction in PANH and PASH coincided with a reduction in the overall nitrogen and sulphur contents of the oils.     

Simultaneous Disruption of Pheromone Communication in Choristoneura rosaceana and Pandemis limitata with Pheromone and Antagonist Blends

In British Columbia, trapping and wind-tunnel studies demonstrated that (Z)-9-tetradecenyl acetate (Z9–14:OAc), a minor component of the sex pheromone for Pandemis limitata, acted as a pheromone antagonist to a sympatric species, Choristoneura rosaceana. Addition of >1% Z9–14:OAc to the four-component C. rosaceana pheromone in a wind tunnel resulted in significant reductions in the proportion of male C. rosaceana that wing fanned, locked on to the plume in flight, oriented upwind, and made source contact, compared to the responses to the pheromone alone. Disruption of pheromone communication was tested in 33.3 × 33.3-m plots, at a release rate of 10 mg/ha/hr using Conrel fiber dispensers. Z9–14:OAc applied alone did not disrupt orientation to virgin-female-baited traps for either C. rosaceana or P. limitata. A 1:1 mixture of Z9–14:OAc and the four-component C. rosaceana pheromone was as effective as the pheromone alone at disrupting orientation of C. rosaceana males to virgin-female-baited traps, demonstrating that disruption apparently did not occur through false-trail following. The 1:1 mixture of Z9–14:OAc and the C. rosaceana pheromone also reduced catches of P. limitata males in virgin-female-baited traps, but not significantly more than the 83% disruption caused by the pheromone alone. Therefore, the C. rosaceana pheromone could be used alone or with Z9–14:OAc to disrupt communication and, presumably, mating in both leafrollers simultaneously.     

A water-activated cuprous bromide battery

In this work a water-activated copper(I) bromide battery was developed and investigated. CuBr combined with sulphur as the reactive cathode material was compared with the CuCl-sulphur combination, the anode being in both cases a magnesium alloy. Battery characteristics were tested at room temperature and in an atmosphere simulation chamber because water-activated batteries are mostly used in meteorological radiosondes. Heat evolution was studied calorimetrically, and the potentials of the single electrodes were measured in half-cell experiments. The practical voltages remained significantly lower than the theoretical ones. The low actual voltages of the batteries were found to be caused by the potential loss at the magnesium anode. The heat evolution power of the CuBr battery was approximately 20% lower than the power of the CuCl battery as a result of bromide ions that catalyse the exothermic corrosion reaction of magnesium less than chloride ions. The CuBr battery is environmentally preferable to the CuCl battery because the reaction that produces harmful Cu²⁺ ions does not progress with CuBr. The problem when using CuBr is the slow activation, which can be accelerated by adding soluble salts to increase the conductivity of the electrolyte.     

Synthesis and nonlinear optical properties of PMMA copolymers having novel benzoxazole chromophores attached with various electron-withdrawing groups

For improvements of thermal stability and nonlinear optical (NLO) activity of chromophores, we newly synthesized a series of NLO chromophores incorporating aromatic benzoxazole unit as a π-conjugated bridge with various electron-withdrawing groups, such as nitrophenyl, nitrothiophene, nitrofuran, dicyanovinylphenyl, and nitrophenylethenyl group. Polymethylmethacrylate copolymers (PMBz) containing these benzoxazole chromophores were synthesized and their properties were investigated by thermogravimetry and ultraviolet-visible spectroscopy. The PMBz copolymers exhibited better thermal and ultraviolet stabilities than the corresponding copolymer with general stilbene chromophores (PMSt). Moreover, temporal stability of nonlinear optical coefficient (d₃₃) of PMBz copolymer increased in comparison with that of PMSt. The copolymer with benzoxazole–nitrothiophene chromophores had the largest d₃₃ value of 153 pm/V (at 1.064 mm) and nonresonant d₃₃ calculated by the two-level model was 21.3 pm/V.