Richard P. K. Wells

A comparison of cortical and trabecular bone from C57 Black 6 mice using Raman spectroscopy.

Cortical and trabecular bone are both produced and maintained by the same cell types. At the microscopic scale they have a similar lamellar structure but at a macroscopic scale they are very different. Raman microscopy has been used to investigate compositional differences in the two bone types using bone from standard laboratory mice in physiological conditions. Clear differences were observed when complete spectra were compared by principal component analysis (PCA). Analysis of individual bands showed cortical bone to have compositional characteristics of older bone when compared with trabecular material, possibly due to the higher bone turnover traditionally reported in the trabecular compartment.

Enantioselective hydrogenation of pyruvate esters in the mesoporous environment of Pt-MCM-41

Pt-MCM-41 catalysts having loadings of up to 2% Pt have been synthesised using three strategies: (i) direct synthesis from a Pt2+-containing gel, (ii) exchange of Na+ in Al-MCM-41 (containing 8% aluminium) for Pt2+, (iii) exchange of H+ in H-MCM-41 (containing 1% aluminium) for Pt2+. HRTEM confirmed the retention of the mesoporous structure in the active catalysts and gave information on Pt particle size and location. 27Al NMR provided information on the movement of aluminium within the structure during catalyst preparation. Enantioselective hydrogenation of methyl and ethyl pyruvate was catalysed by cinchonidine-modified Pt-MCM-41 at 293 K and elevated hydrogen pressures; performance was compared to that provided by the standard reference catalyst EUROPT-1. Catalysts prepared by strategies (i) and (ii) performed best, giving values of the enantiomeric excess comparable to those afforded by EUROPT-1 at rates moderated by an order of magnitude by mass transfer effects. Performance was impaired when Pt particle size in the mesopores was so small that conditions favoured racemic reaction.

Photocatalytic Activity of Doped and Undoped Titanium Dioxide 32 Nanoparticles Synthesised by Flame Spray Pyrolysis

*Email: felicity.sartain@bio-nano-consulting.com The photocatalytic activities of a series of titanium dioxide (TiO2) based nanoparticles, synthesised via flame spray pyrolysis (FSP), have been investigated and compared with the commercially available Evonik Aeroxide TiO2 P 25 (P 25). The effects of metal ions aluminium, tin and platinum, respectively, on the physical and chemical properties of the TiO2 nanoparticles are reported. The set of six samples were characterised by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma-mass spectrometry (ICP-MS) and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. Specific surface areas were determined using nitrogen adsorption and desorption measurements. Subsequent photocatalytic studies of the degradation of methyl orange (MO) dye under UV irradiation demonstrated that addition of Al and Sn had a negative effect on catalytic performance, whereas the addition of ≤0.7 at% Pt to each sample enhanced photocatalytic activity. Most interestingly, the Pt-doped composite samples (TiO2-Sn/Pt and TiO2-Al/Pt) both showed a significantly higher rate of degradation of MO, when compared to P 25. All Pt-doped samples show an increased visible photon absorption capacity. The relationships between the physical and chemical characteristics are discussed in relation to photocatalytic performance.

Remediation of a chlorinated aromatic hydrocarbon in water by photoelectrocatalysis

Photoelectrocatalysis driven by visible light offers a new and potentially powerful technology for the remediation of water contaminated by organo-xenobiotics. In this study, the performance of a visible light-driven photoelectrocatalytic (PEC) batch reactor, applying a tungsten trioxide (WO(3)) photoelectrode, to degrade the model pollutant 2,4-dichlorophenol (2,4-DCP) was monitored both by toxicological assessment (biosensing) and chemical analysis. The bacterial biosensor used to assess the presence of toxicity of the parent molecule and its breakdown products was a multicopy plasmid lux-marked E. coli HB101 pUCD607. The bacterial biosensor traced the removal of 2,4-DCP, and in some case, its toxicity response suggests the identification of transient toxic intermediates. The loss of the parent molecule, 2,4-DCP determined by HPLC, corresponded to the recorded photocurrents. Photoelectrocatalysis offers considerable potential for the remediation of chlorinated hydrocarbons, and that the biosensor based toxicity results identified likely compatibility of this technology with conventional, biological wastewater treatment.

High temperature preparation of vanadium phosphate catalysts using water as solvent

Vanadium phosphate catalysts prepared in aqueous solution at elevated temperature (145 °C) using either H3PO3 or V2O4 as reactants are described and discussed. This methodology produces catalysts with a much higher surface area (ca. 20 m2g−1) compared with those prepared using aqueous routes using HCl as reducing agent (ca. 4 m2g−1). The materials were characterised using a combination of powder XRD, BET surface area measurement, laser Raman spectroscopy, TGA, electron microscopy and 31P spin echo mapping NMR spectroscopy. Refluxing the precursors in water prior to activation was crucial in obtaining high surface area materials, and 31P spin echo mapping NMR together with electron microscopy data indicate that the water reflux step influences the relative amounts of V4+ and V5+ phases present in the catalyst, as well as reducing the size of the crystallites. A correlation between the activity of the catalyst and the surface area is observed. However, a small group of catalysts display a higher activity than that expected from this correlation, and this increased activity is discussed in terms of the interaction of V4+ and V5+ phases.

Vanadium(V) phosphate prepared using solvent-free method

A solvent-free method of preparation of a vanadium(V) phosphate is described and discussed. Reaction of V2O5 with H3PO4 in the absence of water at 150 °C leads to the formation of a new catalytic material that is designated as “anhydrous” VOPO4. The material readily hydrates to form VOPO4⋅2H2O and has been characterised using powder X-ray diffraction, in situ Raman spectroscopy and 31P MAS NMR spectrometry. On activation in dry N2 followed by reaction with butane/air another novel material is formed that has an intrinsic activity for maleic anhydride that is similar to catalysts derived from VOHPO4⋅0.5H2O under comparable conditions. Activation of VOPO4⋅2H2O under comparable conditions leads to the formation of αI-VOPO4 which exhibits no partial oxidation activity. Reaction of “anhydrous” VOPO4 with alcohols leads to the exclusive formation of VO(H2PO4)2 in further contrast to VOPO4⋅2H2O which under similar conditions leads to the synthesis of VOHPO4⋅0.5H2O.

Dehydration of butan-2-ol using modified zeolite crystals

Modification of zeolite H-Y by dithiane oxides is shown to enhance significantly the rate of dehydration of butan-2-ol to butenes. Reaction of racemic butan-2-ol over zeolite H-Y modified with (R)-1,3-dithiane-1-oxide indicates that the high activity catalyst is enantiomerically discriminating, as one enantiomer reacts preferentially to the other, although both are present within the micropores under the reaction conditions. The origins of the rate enhancement have been investigated spectroscopically using FTIR and MAS NMR. The enhanced activity is considered to result from a specific interaction between the sulfoxide modifier with the Bronsted acid sites associated with framework hydroxyl groups together with a strong interaction with an extra-framework aluminium species. This combination results in the formation of a rigid high activity site. Investigations using the amino acid cystine as an alternative to 1,3-dithiane-1-oxide have indicated that in this case the modifier is more weakly bound within the zeolite pores and exhibits considerable molecular motion, leading to the modified catalyst demonstrating no enantioselectivity or rate enhancement.

Gold modified cobalt-based Fischer-Tropsch catalysts for conversion of synthesis gas to liquid fuels

The addition of Au as a promoter/modifier for alumina supported Co catalyst has been studied by combined in-situ high temperature, high pressure Fourier transform infrared (FTIR) and on-line gas chromatography. The combination of these tools permitted the state of the active catalyst surface to be monitored while following the elution of reaction products during the first 5–7 h on stream of the catalyst. The catalysts under study were a 10%Co/Al2O3 and a 2.5%Au/10%Co/Al2O3. Samples were characterised before use using Raman and temperature programmed reduction (TPR). During the initial stages of reaction, hydrocarbons were built up on the surface of the catalyst as monitored by FTIR and the nature and amount of these species were assessed in terms of CH2/CH3 ratio and the density of these alkyl fragments by employing absorption coefficients for the individual components. The nature and reducibility of the Co particles were modified by the presence of Au while the later also shifted the CO/H2 balance by acting as an effective water-gas shift catalyst during the early stages of reaction. This characteristic was lost during reaction as a consequence of redistribution of the two metallic phases.

Observation of high enantioselectivity for the gas phase hydrogenation of methyl pyruvate using supported Pt catalysts pre-modified with cinchonidineElectronic supplementary information (ESI) available: use of the Kelvin equation and reactant partial pressure to estimate the effective partial pressure for condensation as a function of pore radius. See http://www.rsc.org/suppdata/cc/b3/b304976k/

Pt supported on alpha-Al2O3, gamma-Al2O3 and SiO2 pre-modified with cinchonidine gives over 50% ee in the hydrogenation of methyl pyruvate to methyl lactate using gas phase reactants at 40 degrees C giving the first clear observation of high enantioselection at the gas/solid interface.

Premodification of Pt/γAl2O3 with cinchonidine for the enantioselective hydrogenation of ethyl pyruvate: effect of premodification conditions on reaction rate and enantioselection

The premodification of a 5 wt% Pt/γ-Al2O3 catalyst with cinchonidine (0.01 and 0.2 g g-1catalyst) is described and discussed. Premodification is carried out by treating the catalyst with a solution of cinchonidine followed by solvent removal. Catalysts premodified in this way give the same ee and initial rate of reaction for the enantioselective hydrogenation of ethyl pyruvate as those using the standard in situ modification procedure. Investigations of different solvents for premodification and reaction (dichloromethane, ethanol) show that it is the solvent used for the reaction that controls the observed enantioselection. Premodified catalysts also display the initial transient behavior typically observed with in situ modified catalysts in which the ee increases with conversion in the early part of the reaction. Premodified catalysts show an enhanced rate of reaction when ethanol is used as the reaction solvent compared with in situ modified catalysts under the same conditions. Premodification using aerobic conditions gives the best results and premodified catalysts can be stored prior to use for up to a week without loss of catalytic performance.