Partial oxidation of methane to syngas in tubular oxygen-permeable reactor

A dense Ba0.5Sr0.5Co0.8Fe0.2O3-delta membrane tube was prepared by the extruding method. Furthermore, a membrane reactor with this tubular membrane was successfully applied to partial oxidation of methane (POM) reaction, in which the separation of oxygen from air and the partial oxidation of methane are integrated in one process. At 875degreesC, 94% of methane conversion, 98% of CO selectivity, 95% of H-2 selectivity, and as high as 8.8 mL/(min (.) cm(2)) of oxygen flux were obtained. In POM reaction condition. the membrane tube shows a very good stability.

Selective oxidation of m-phenoxytoluene to m-phenoxybenzaldehyde with methanol as an additive in acetic acid

With addition of methanol in acetic acid solvent, m-phenoxytoluene could be oxidized to m-phenoxybenzaldehyde selectively by a cobalt bromide catalyst. Paratemters such as the ratio of Co/Br and the reaction time of m-phenoxytoluene oxidation as well as visible spectra of cobalt bromide in acetic acid/methanol solvents, were also investigated. Addition of methanol caused the oxidation of aldehydes to proceed more slowly than it did solely in acetic acid solvent. The decrease of cobaltous-multibromides in acetic acid/methanol solvents was responsible for the improvement in the selective oxidation of m-phenoxytoluene. (C) 1999 Elsevier Science B.V. All rights reserved.

Different mechanisms for the formation of acetaldehyde and ethanol on the Rh-based catalysts

Different mechanisms for the formation of acetaldehyde and ethanol on the Rh-based catalysts were investigated by the TPR (temperature programmed reaction) method, and the active sites were studied by CO-TPD, TPSR (temperature programmed surface reaction of preadsorbed CO by H-2) and XPS techniques. The TPR results indicated that ethanol and acetaldehyde might be formed through different intermediates, whereas ethanol and methanol might result from the same intermediate. Results of CO-TPD, TPSR, and XPS showed that on the Rh-based catalyst, the structure of the active sites for the formation of C-2-oxygenates is ((RhxRhy+)-Rh-0)-O-Mn+ (M=Mn or Zr, x>>y, 2 less than or equal ton less than or equal to4). The tilt-adsorbed CO species is the main precursor for CO dissociation and the precursor for the formation of ethanol and methanol. Most of the linear and geminal adsorbed CO species desorbed below 500 K. Based on the suggested model of the active sites, detailed mechanisms for the formation of acetaldehyde and ethanol are proposed. Ethanol is formed by direct hydrogenation of the tilt-adsorbed CO molecules, followed by CH2 insertion into the surface CH2-O species and the succeeding hydrogenation step. Acetaldehyde is formed through CO insertion into the surface CH3-Rh species followed by hydrogenation, and the role of the promoters was to stabilize the intermediate of the surface acetyl species. (C) 2000 Academic Press.

Structure and properties of samarium overlayer and Sm/Rh surface alloy on Rh(100)

The structure and properties of Sm overlayer and Sm/Rh surface alloy have been investigated with Auger electron spectroscopy (AES), low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption spectroscopy (TDS). The growth of Sm on Rh(100) at room temperature (RT) appears following the Stranski-Krastanov growth mode and only the trivalent state Sm is observed from XPS results. Thermal treatment of the Sm film at 900 K leads to the formation of ordered surface alloy which shows the c(5 root2 x root2)R45 degrees and c(2 x 2) LEED patterns. Annealing the Sm film at temperature above 400 K makes the binding energy (B.E.) of Sm 3d(5/2) shift to higher energy by 0.7 eV, which indicates charge transfer from Sm to Rh(100) substrate, causing the increase of CO desorption temperature.

Strong effect of transitional metals on the sulfur resistance of Pd/HY-Al2O3 catalysts for aromatic hydrogenation

In order to improve the sulfur resistance of noble metal catalysts in the aromatic hydrogenation of diesel fuel, the alloying effect of non-noble metals with Pd was studied. Toluene hydrogenation over Pd and Pd-M bimetallic catalysts (M = Cr, W,La, Mn, Mo, Ag) on a mixed HY-Al2O3 support was investigated in the presence of 3000 ppm sulfur as thiophene in the feedstock. The results showed that the addition of the second metals strongly affected the activity of toluene hydrogenation, which suggests that the sulfur resistibility of Pd-M bimetallic catalysts is much different from single Pd. La, Mn, Mo and Ag decreased the sulfur resistance of the palladium catalysts. For example, the toluene conversion at 553 K was observed to decrease sharply from 39.4 wt.% on Pd to 1.6 wt.% on Pd-Ag, which is by a factor of 25. One of the important findings in this article is that Cr and W increase hydrogenation activity of Pd catalysts. The reactions occurring on these catalysts include hydrogenation, isomerization and hydrocracking, The addition of the second metals has no noticeable effects on the hydrogenation and isomerization selectivity, but it slightly suppresses hydrocracking reactions. The four typical catalysts, Pd-Cr, Pd-W, Pd-Ag and Pd were characterized by infrared (IR) spectroscopy of pyridine and CO. LR spectra of CO revealed the strong interaction between Pd and the second metal as Cr, W and Ag (or their oxide), indicating that the improvement in sulfur resistance originates from electron-deficient Pd with the addition of second metals. (C) 2001 Elsevier Science B.V. All rights reserved.

Enhancement of the catalytic performance of supported-metal catalysts by pretreatment of the support

We report an interesting finding that the catalytic performance of supported Ag/SiO2 catalysts toward selective catalytic oxidation of CO in hydrogen at low temperatures can be greatly enhanced by pretreatment of the SiO2 support before catalyst preparation. Calcination of SiO2 at appropriate temperatures preferentially removes the H-bonded SiOH, which results in the highly dispersive Ag/SiO2 catalyst and thus improves the catalytic performance. (c) 2005 Elsevier Inc. All rights reserved.

Reversible regeneration of molybdenum carbonyl species on an alumina thin film

The thin alumina film-supported metallic molybdenum model catalyst was prepared by thermal decomposition of MO(CO)6, and CO chemisorption on the catalyst was investigated in-situ by thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). The results showed that a molybdenum-carbonyl-like species was formed on the alumina surface at low temperature by high coordination of CO with the surface metallic molybdenum nanoparticles, indicating a reversible regeneration of molybdenum carbonyl on the alumina surface. CO chemisorption on the model catalyst surface caused the Mo 3d XPS peak to shift toward higher binding energy. The formed molybdenum carbonyl species appeared at about 240 K in the TDS. The supported metallic molybdenum nanoparticles were quite different from the bulk molybdenum in chemical properties, which indicated a prominent particle-size effect of the clusters.

Selenium-catalyzed reductive carbonylation of 2-nitrophenols to 2-benzoxazolones

2-Benzoxazolones or 2-benzimidazolones are synthesized in moderate to good yields in the presence of a base (KOH, NaOH, KOAc, NEt3, DBU) at atmospheric pressure or under a high pressure of CO by one-pot reductive carbonylation of 2-nitrophenols or 2-nitroanihne in the presence of selenium as catalyst. Besides the effect of base, the effects of solvent and temperature on the reaction were investigated at high or atmospheric pressure. Contrasting results were obtained for 2-benzoxazolones or 2-benzimidazolone at high and atmospheric pressures. Moreover, phase-transfer catalysis was exhibited. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).

A trait specific model of competition in a spatially structured plant community

John Warren and Chris Topping (2004). A trait specific model of competition in a spatially structured plant community. Ecological Modelling, 180 pp.477-485 RAE2008

Optimisation of chemoenzymatic processes in asymmetric synthesis

This thesis describes the optimisation of chemoenzymatic methods in asymmetric synthesis. Modern synthetic organic chemistry has experienced an enormous growth in biocatalytic methodologies; enzymatic transformations and whole cell bioconversions have become generally accepted synthetic tools for asymmetric synthesis. Biocatalysts are exceptional catalysts, combining broad substrate scope with high regio-, enantio- and chemoselectivities enabling the resolution of organic substrates with superb efficiency and selectivity. In this study three biocatalytic applications in enantioselective synthesis were explored and perhaps the most significant outcome of this work is the excellent enantioselectivity achieved through optimisation of reaction conditions improving the synthetic utility of the biotransformations. In the first chapter a summary of literature discussing the stereochemical control of baker’s yeast (Saccharomyces Cerevisae) mediated reduction of ketones by the introduction of sulfur moieties is presented, and sets the work of Chapter 2 in context. The focus of the second chapter was the synthesis and biocatalytic resolution of (±)-trans-2-benzenesulfonyl-3-n-butylcyclopentanone. For the first time the practical limitations of this resolution have been addressed providing synthetically useful quantities of enantiopure synthons for application in the total synthesis of both enantiomers of 4-methyloctanoic acid, the aggregation pheromone of the rhinoceros beetles of the genus Oryctes. The unique aspect of this enantioselective synthesis was the overall regio- and enantioselective introduction of the methyl group to the octanoic acid chain. This work is part of an ongoing research programme in our group focussed on baker’s yeast mediated kinetic resolution of 2-keto sulfones. The third chapter describes hydrolase-catalysed kinetic resolutions leading to a series of 3-aryl alkanoic acids. Hydrolysis of the ethyl esters with a series of hydrolases was undertaken to identify biocatalysts that yield the corresponding acids in highly enantioenriched form. Contrary to literature reports where a complete disappearance of efficiency and, accordingly enantioselection, was described upon kinetic resolution of sterically demanding 3-arylalkanoic acids, the highest reported enantiopurities of these acids was achieved (up to >98% ee) in this study through optimisation of reaction conditions. Steric and electronic effects on the efficiency and enantioselectivity of the biocatalytic transformation were also explored. Furthermore, a novel approach to determine the absolute stereochemistry of the enantiopure 3-aryl alkanoic acids was investigated through combination of co-crystallisation and X-ray diffraction linked with chiral HPLC analysis. The fourth chapter was focused on the development of a biocatalytic protocol for the asymmetric Henry reaction. Efficient kinetic resolution in hydrolase-mediated transesterification of cis- and trans- β-nitrocyclohexanol derivatives was achieved. Combination of a base-catalysed intramolecular Henry reaction coupled with the hydrolase-mediated kinetic resolution with the view to selective acetylation of a single stereoisomer was investigated. While dynamic kinetic resolution in the intramolecular Henry was not achieved, significant progress in each of the individual elements was made and significantly the feasibility of this process has been demonstrated. The final chapter contains the full experimental details, including spectroscopic and analytical data of all compounds synthesised in this project, while details of chiral HPLC analysis are included in the appendix. The data for the crystal structures are contained in the attached CD.

Potential impacts of leakage from deep CO2 geosequestration on overlying freshwater aquifers.

Carbon Capture and Storage may use deep saline aquifers for CO(2) sequestration, but small CO(2) leakage could pose a risk to overlying fresh groundwater. We performed laboratory incubations of CO(2) infiltration under oxidizing conditions for >300 days on samples from four freshwater aquifers to 1) understand how CO(2) leakage affects freshwater quality; 2) develop selection criteria for deep sequestration sites based on inorganic metal contamination caused by CO(2) leaks to shallow aquifers; and 3) identify geochemical signatures for early detection criteria. After exposure to CO(2), water pH declines of 1-2 units were apparent in all aquifer samples. CO(2) caused concentrations of the alkali and alkaline earths and manganese, cobalt, nickel, and iron to increase by more than 2 orders of magnitude. Potentially dangerous uranium and barium increased throughout the entire experiment in some samples. Solid-phase metal mobility, carbonate buffering capacity, and redox state in the shallow overlying aquifers influence the impact of CO(2) leakage and should be considered when selecting deep geosequestration sites. Manganese, iron, calcium, and pH could be used as geochemical markers of a CO(2) leak, as their concentrations increase within 2 weeks of exposure to CO(2).

The impact of anxiety-inducing distraction on cognitive performance: a combined brain imaging and personality investigation.

BACKGROUND: Previous investigations revealed that the impact of task-irrelevant emotional distraction on ongoing goal-oriented cognitive processing is linked to opposite patterns of activation in emotional and perceptual vs. cognitive control/executive brain regions. However, little is known about the role of individual variations in these responses. The present study investigated the effect of trait anxiety on the neural responses mediating the impact of transient anxiety-inducing task-irrelevant distraction on cognitive performance, and on the neural correlates of coping with such distraction. We investigated whether activity in the brain regions sensitive to emotional distraction would show dissociable patterns of co-variation with measures indexing individual variations in trait anxiety and cognitive performance. METHODOLOGY/PRINCIPAL FINDINGS: Event-related fMRI data, recorded while healthy female participants performed a delayed-response working memory (WM) task with distraction, were investigated in conjunction with behavioural measures that assessed individual variations in both trait anxiety and WM performance. Consistent with increased sensitivity to emotional cues in high anxiety, specific perceptual areas (fusiform gyrus--FG) exhibited increased activity that was positively correlated with trait anxiety and negatively correlated with WM performance, whereas specific executive regions (right lateral prefrontal cortex--PFC) exhibited decreased activity that was negatively correlated with trait anxiety. The study also identified a role of the medial and left lateral PFC in coping with distraction, as opposed to reflecting a detrimental impact of emotional distraction. CONCLUSIONS: These findings provide initial evidence concerning the neural mechanisms sensitive to individual variations in trait anxiety and WM performance, which dissociate the detrimental impact of emotion distraction and the engagement of mechanisms to cope with distracting emotions. Our study sheds light on the neural correlates of emotion-cognition interactions in normal behaviour, which has implications for understanding factors that may influence susceptibility to affective disorders, in general, and to anxiety disorders, in particular.

Intracellular Cytokine Staining and Flow Cytometry: Considerations for Application in Clinical Trials of Novel Tuberculosis Vaccines.

Intracellular cytokine staining combined with flow cytometry is one of a number of assays designed to assess T-cell immune responses. It has the specific advantage of enabling the simultaneous assessment of multiple phenotypic, differentiation and functional parameters pertaining to responding T-cells, most notably, the expression of multiple effector cytokines. These attributes make the technique particularly suitable for the assessment of T-cell immune responses induced by novel tuberculosis vaccines in clinical trials. However, depending upon the particular nature of a given vaccine and trial setting, there are approaches that may be taken at different stages of the assay that are more suitable than other alternatives. In this paper, the Tuberculosis Vaccine Initiative (TBVI) TB Biomarker Working group reports on efforts to assess the conditions that will determine when particular assay approaches should be employed. We have found that choices relating to the use of fresh whole blood or peripheral blood mononuclear cells (PBMC) and frozen PBMC; use of serum-containing or serum-free medium; length of stimulation period and use of co-stimulatory antibodies can all affect the sensitivity of intracellular cytokine assays. In the case of sample material, frozen PBMC, despite some loss of sensitivity, may be more advantageous for batch analysis. We also recommend that for multi-site studies, common antibody panels, gating strategies and analysis approaches should be employed for better comparability.

Colloidal microgel in removal of water from biodiesel

A series of poly(N-isopropylacrylamide) [pNIPAM]-based homo-polymer and co-polymer microgel particles were prepared by surfactant-free emulsion polymerisation. The co-monomers were acrylic acid. 4-vinylpyridine. butyl acrylate, 4-vinylbiphenyl and vinyl laurate. Co-monomers were added at a concentration of 10% (w/w) relative to the base monomer pNIPAM for the preparation of each co-polymer microgel. The co-monomers chosen vary by their organic chain length, polarity and pH sensitivity, as these should influence how the particles behave in aqueous and non-aqueous solvents. The effect of adding different types of co-monomer into the microgel structure was investigated with respect to their dispersibility in different solvents. These microgel particles have shown useful application in the removal of water from biodiesel prepared from rape seed. Karl Fischer experiments showed that microgel particles can be used to reduce the water content in biodiesel to an acceptable level for incorporation into internal combustion engines. (C) 2008 Elsevier B.V. All rights reserved.

Cyclic voltammetry and spectroelectrochemical study of nickel and cobalt diphenyltetraazaannulene complexes

The absorption spectra. cyclic voltammetry and spectroelectrochemistry of [Ni(II)DPTAA] and [Co(II)DPTAA] (DPTAA = 6,13-diphenyldibenzo[b,i][1,4,8,11] tetraaza[14]annulene) complexes in DMF are reported in detail. The ligand oxidation is observed for [Ni(II)DPTAA] at +0.70 V vs. SCE whereas Ni2(+/+) occurs at - 1.60 V. For [Co(II)DPTAA], a ligand oxidation redox couple is seen at +0.56 V while the Co2+/+ and Co2+/3+ redox couples appear at -1.21 and +0.24 V, respectively. All observed redox couples are assigned to reversible one-electron processes on account of peak separations and scan-rate dependency. These processes were further investigated by spectroelectrochemistry for [Co(II)DPTAA]. For [Co(II)DPTAA], axial ligation of pyridine was found to shift the Co2+/3+ redox couple more negative. while the ligand oxidation was shifted to more positive potentials. From a spectrophotometric titration of [Co(II)DPTAA] with pyridine an equilibrium constant, K-f, was determined for the binding of pyridine to [Co(II)DPTAA]. This was found to be 10.2 dm(3) mol(-1), slightly lower than that of [Co(II)TAA], indicating the influence of the phenyl groups. From this value and shifts in the Co2+/3+ redox couple upon ligation, an equilibrium constant for the binding of pyridine to [Co(III)DPTAA], K'(f), was found to be 5.06 x 10(6) dm(3) mol(-1). (c) 2007 Elsevier B.V. All rights reserved.