A new approach for the detection of ethylene using silica-supported palladium complexes

The coordination of olefins to square-planar Pd(II) and Pt(II) complexes containing 2,9-dimethylphenanthroline (L1) often involves a change of color associated with a change of geometry at the metal center. In order to obtain suitable colorimetric detectors for ethylene gas, a series of new Pd(II) and Pt(II) compounds with a range of 2,9-disubstituted phenanthroline ligands [2,9-di-n-butyl-1,10-phenanthroline (L-2), 2,9-di-s-butyl-1,10-phenanthroline (L3), 2,9-diphenyl-1,10-phenanthroline (L4), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine, L5)] have been prepared and their reactivity toward ethylene investigated both in solution and after depositing the detector compounds on a variety of solid supports. The Pd(II) complex [PdCl2(L2)] supported on silica undergoes a clear color change upon exposure to ethylene, while remaining stable toward air and water, and forms the basis for new simple colorimetric detectors with potential applications in ethylene pipe-leak detection and the monitoring of fruit ripening. Encouragingly, the detector is able to discriminate between fruit at different stages of ripening. The response of the detector to other volatiles was also examined, and specific color changes were also observed upon exposure to aromatic acetylenes. The crystal structures of four new derivatives, including the ethylene-Pt(II) complex [PtCl2(C2H4)(L2)], are also described.

Deactivation and regeneration of ruthenium on silica in the liquid-phase hydrogenation of butan-2-one

A Ru/SiO2 catalyst was investigated for the liquid-phase hydrogenation of butan-2-one to butan-2-ol with water as a medium. Although excellent reactivity was observed, a gradual deactivation of the catalyst was found on recycle of the catalyst. The spent catalyst was characterized by using XRD, XPS, TEM, TPR, CO chemisorption, FTIR and ICP analyses. Formation of Ru(OH)(x) surface species is proposed to be the main cause of catalyst deactivation with no significant Ru leaching into the reaction mixture. Following catalyst regeneration, up to 85% of the initial catalytic activity could be recovered successfully. Moreover, adsorption of secondary aliphatic alcohols on the catalyst was found to significantly reduce the formation of Ru(OH)(x) during the reaction, thus protecting the catalyst from deactivation.

Characterization of silica-supported dodecatungstic heteropolyacids as a function of their dehydroxylation temperature

Dodecatungsto-silicic H4SiW12O40 and -phosphoric acids H3PW12O40 were deposited on silica by a classical impregnation technique. The resulting materials were studied by in situ Raman and infrared spectroscopy, XPS and by solid-state H-1 MAS NMR as a function of their dehydroxylation temperature. The data show that in the case of H3PW12O40 three silanol groups are protonated while in the case of H4SiW12O40 at least one acidic proton remains. Upon heating this proton reacts leading to a disordered structure and a broadening of the W-O Raman bands.

Liquid marble formation using hydrophobic powders

This work aims to investigate and quantitatively measure “liquid marble” phenomena using hydrophobic powders (granules). The hydrophobic powders based on a copper substrate were prepared by a silver deposition technique of particle sizes 9 µm, 20 µm and 320 µm and of contact angle with water approaching 160°. The hydrophobic powder poly-methylmethacralate (PMMA) particle size 42 µm and contact angle of 120° was also used to determine the effect of powder density on liquid marble stability. The experimental investigations indicated that for successful formation of liquid marbles a number of variables in addition to hydrophobicity need to be considered, namely: powder density; powder particle size; powder shape; liquid marble formation technique. It was found that liquid marbles were formed using all four powders to varying extents, with a low powder particle size forming more stable liquid marbles. In a series of gravimetric tests, adhered powder mass on liquid marbles was found to be directly proportional to the water droplet surface area. A more complete coverage of the water drops were found with PMMA powder than the hydrophobic granules. Moreover, a further procedure was developed to increase the mechanical strength of the liquid marble, by polymerising methylmethacrylate (MMA) on the surface of a PMMA powder – liquid marble, with the aim of maintaining water within a more robust PMMA – liquid marble shell. This technique may prove to be a novel way of encapsulating drug compounds, such as gentamicin sulphate, for PMMA bone cement.

Silica grain labelling and EDX spectroscopy; evidence for inter-grain diffusion of Pt(NH3)(4)(2+) species during Pt/SiO2 catalyst preparation by ionic exchange

Labelling of silica grains and energy dispersive X-ray spectroscopy (EDX) in a TEM-FEG (field emission gun) were used to demonstrate the migration of Pt(NH3)(4)(2+) species from one grain to another during Pt/SiO2 catalyst preparation by the ion-exchange procedure.

Solvation of 1-butyl-3-methylimidazolium hexafluorophosphate in aqueous ethanol - a green solution for dissolving 'hydrophobic' ionic liquids

The relatively hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate has been found to be totally miscible with aqueous ethanol between 0.5 and 0.9 mol fraction ethanol, whereas the ionic liquid is only partially miscible with either pure water or absolute ethanol; the ability to dissolve 1-butyl-3-methylimidazolium hexafluorophosphate in a 'green' aqueous solvent system has important implications for cleaning, purification, and separations using ionic liquids.

Hydrophobic ionic liquids incorporating N-alkylisoquinolinium cations and their utilization in liquid-liquid separations

The first examples of Room Temperature Ionic Liquids (RTIL) containing fused polycyclic N-alkylisoquinolinium cations ([C(n)isoq](+)) in combination with the bis(perfluoroethylsulfonyl) imide anion ([BETI](-)) have been synthesized, characterized, and utilized in liquid-liquid partitioning from water; these salts have unexpectedly low melting points and give high distribution ratios for aromatic solutes, especially chlorobenzenes, between the RTIL and water.

On the solubilization of water with ethanol in hydrophobic hexafluorophosphate ionic liquids

The solubility of water in the hydrophobic 1-alkyl-3-methylimidazolium hexafluorophosphate (alkyl = butyl, hexyl, and octyl) ionic liquids, can be significantly increased in the presence of ethanol as a co-solute. 1-Hexyl-3-methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium hexafluorophosphate are completely miscible with ethanol, and immiscible with water, whereas 1-butyl-3-methylimidazolium hexafluorophosphate is totally miscible with aqueous ethanol only between 0.5-0.9 mole fraction ethanol at 25degreesC. At higher and lower mole fraction of ethanol, the aqueous and IL components are only partially miscible and a biphasic system is obtained upon mixing equal volumes of the IL and aqueous ethanol. The observation of a large range of total miscibility between water and the IL in the three-component system has important implications for purifications and separations from IL.

Hydrophobic ionic liquids with strongly coordinating anions

Ionic liquids containing the hexafluoroacetylacetonate anion are immiscible with water and they exhibit strong metal-complexing ability.

Luminescent ionogels based on europium-doped ionic liquids confined within silica-derived networks

Luminescent ionogels were prepared by doping an europium( III) tetrakis beta-diketonate complex into an imidazolium ionic liquid, followed by immobilization of the ionic liquid by confinement in a silica network. The ionogels were obtained by a non-hydrolytic method as perfect monoliths featuring both the transparency of silica and the ionic conductivity performances of ionic liquids. The ionogels contain 80 vol % of ionic liquid. The organic-inorganic hybrid materials showed a very intense red photoluminescence under ultraviolet irradiation. The red emission has a very high coloric purity.

Optimization of Cement Grouts Containing Silica Fume and Viscosity Modifying Admixture

There is an increasing need to identify the effect of mix composition on the rheological properties of cementitious grouts using minislump, Marsh cone, cohesion plate, washout test, and cubes to determine the fluidity, the cohesion, and other mechanical properties of grouting applications. Mixture proportioning involves the tailoring of several parameters to achieve adequate fluidity, cohesion, washout resistance and compressive strength. This paper proposes a statistical design approach using a composite fractional factorial design which was carried out to model the influence of key parameters on the performance of cement grouts. The responses relate to performance included minislump, flow time using Marsh cone, cohesion measured by Lombardi plate meter, washout mass loss and compressive strength at 3, 7, and 28 days. The statistical models are valid for mixtures with water-to-binder ratio of 0.37–0.53, 0.4–1.8% addition of high-range water reducer (HRWR) by mass of binder, 4–12% additive of silica fume as replacement of cement by mass, and 0.02–0.8% addition of viscosity modifying admixture (VMA) by mass of binder. The models enable the identification of underlying factors and interactions that influence the modeled responses of cement grout. The comparison between the predicted and measured responses indicated good accuracy of the established models to describe the effect of the independent variables on the fluidity, cohesion, washout resistance and the compressive strength. This paper demonstrates the usefulness of the models to better understand trade-offs between parameters. The multiparametric optimization is used to establish isoresponses for a desirability function for cement grout. An increase of HRWR led to an increase of fluidity and washout, a reduction in plate cohesion value, and a reduction in the Marsh cone time. An increase of VMA demonstrated a reduction of fluidity and the washout mass loss, and an increase of Marsh cone time and plate cohesion. Results indicate that the use of silica fume increased the cohesion plate and Marsh cone, and reduced the minislump. Additionally, the silica fume improved the compressive strength and the washout resistance.