XPS evidence for structure-performance relationship in selective hydrogenation of crotonaldehyde to crotyl alcohol on platinum systems supported on natural phosphates.

Natural phosphates are an important natural resource in Morocco, which needs to be valorised. They can be used not only as fertilisers but also as catalysts. Here, we report for the first time on its use as support for platinum and the application of the resulting systems to the liquid-phase selective hydrogenation of an α,ß-unsaturated carbonyl compound (crotonaldehyde) to the corresponding unsaturated alcohol (crotyl alcohol), a process of interest in the production of pharmaceuticals, agrochemicals and fragrances. Catalytic results are related to the surface solid structure as determined by XPS. Therefore, the most active systems showed new surface interactions as evidenced by the appearance of new P, O, Ca, F and C peaks and the shift of Pt ones to lower binding energies. Further modification of the most active system with FeCl(2) led to 70% selectivity to crotyl alcohol at 34% conversion.

A nuclear magnetic resonance (1H and 13C) and isotope ratio mass spectrometry (delta13C, delta2H and delta18O) study of Andalusian olive oils.

We have determined delta(13)C, delta(2)H and delta(18)O isotopic abundances in Andalusian olive oils. In addition, the fatty acid composition and the distribution of isomers at positions 1,3 and 2 of glycerol were determined by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy, respectively. Isotopic results obtained for four series of oil samples extracted from olives harvested in the 2004/05 and 2005/06 seasons are discussed in terms of olive variety, ripeness, geographical origin, fatty acid composition and growing altitude. A distinction was also established between olives grown in irrigated and in dry land by studying selected samples of the previous series and others from the 2005/06, 2006/07, 2007/08 and 2008/09 seasons. The results showed that olive ripeness does not influence the abundance of any of the three isotopes studied. On the other hand, the olive variety influences the abundance of the oxygen and hydrogen isotopes, and also, less markedly, that of carbon. No clear-cut effect of height or latitude on isotope values is observed, probably because the olive variety also changes with height and latitude, thus masking such influences. The oil samples from dryland-grown olives had increased delta(13)C values relative to irrigation-grown olives. In addition, no definite relationship appears to exist between isotope distribution and fatty acid composition. Finally, oil samples from olives harvested in the 2005/06 season in Italy could be distinguished from those from Spain in terms of their isotopic values (delta(2)H mainly).

A study on the potential application of natural phosphate in photocatalytic processes.

In an attempt at increasing surface area of the resulting solids, different titanium-based systems were synthesized on natural phosphate through the sol-gel process using diverse ageing conditions (reflux, magnetic stirring, sonication or microwaves) and tested for gas-phase selective photooxidation of propan-2-ol. The best results were obtained for the system aged under ultrasounds which was ascribed to its lower band-gap energy. Moreover, the synthesis of TiO(2) on natural phosphate seemed to produce retardation in crystallization as well as a change in titanium and phosphorus electronic environments (as determined by XPS) which in the case of the sonicated system resulted in an improved catalytic behavior as compared to pure titania. All in all, the present piece of research shows that provided that its surface area can be increased natural phosphate can be used as support for a photocatalytic active phase thus widening the scope of its application.

Sustainable preparation of supported metal nanoparticles and their applications in catalysis.

Metal nanoparticles have attracted much attention over the last decade owing to their unique properties as compared to their bulk metal equivalents, including a large surface-to-volume ratio and tunable shapes. To control the properties of nanoparticles with particular respect to shape, size and dispersity is imperative, as these will determine the activity in the desired application. Supported metal nanoparticles are widely employed in catalysis. Recent advances in controlling the shape and size of nanoparticles have opened the possibility to optimise the particle geometry for enhanced catalytic activity, providing the optimum size and surface properties for specific applications. This Review describes the state of the art with respect to the preparation and use of supported metal nanoparticles in catalysis. The main groups of such nanoparticles (noble and transition metal nanoparticles) are highlighted and future prospects are discussed.

Preparation of highly active and dispersed platinum nanoparticles on mesoporous Al-MCM-48 and their activity in the hydroisomerisation of n-octane.

Platinum nanoparticles supported on Al-MCM-48 materials have been prepared. The resultant catalysts have been characterized by means of XRD, N2 physisorption experiments, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), and diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS). The activity of these nanoparticles has been tested in relation to the hydroisomerisation of n-octane. The catalytic activities were typically 50 %, with selectivities in the isomerisation process in excess of 70 %, favouring the formation of the 3-methylheptane isomer with respect to the 2- and 4-methylheptanes.

Oxygen-18 measurement of Andalusian olive oils by continuous flow pyrolysis/isotope ratio mass spectrometry.

We report a method for the determination of delta(18)O isotopic abundance in olive oils. The results obtained by applying the method to various Andalusian oil samples obtained in the 2004/05 and 2005/06 seasons are discussed in relation to olive variety, geographical origin, climate and ripeness index. Application of the method to samples of assured varietal purity exposed the influence of olive variety and origin but not of the ripeness index. The delta(18)O values for the 2005/06 season are higher on average than those obtained in the colder 2004/05 season. Results obtained for samples of the Picual and Hojiblanca varieties in Córdoba and Málaga in the 2005/06 season suggest a correlation between enrichment in heavy isotopes and latitude whereas no clear-cut effect of altitude was observed.

Catalytic ability of a cationic Ru(II) monochloro complex for the asymmetric hydrogenation of dimethyl itaconate and enamides.

The synthesis of two Ru chloro complexes, Ru(III)Cl(3)(bpea), 1, and cis-fac-Delta-[Ru(II)Cl{(R)-(bpea)}{(S)-(BINAP)}](BF(4)), cis-fac-Delta-(R)-(S)-2, (bpea = N,N-bis(2-pyridylmethyl)ethylamine; (S)-BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl), is described. Complex 2 is characterized in solution through UV-vis, cyclic voltammetry (CV), and 1D and 2D NMR spectroscopy. X-ray diffraction analysis indicates that in the solid state it possesses the same structure as in solution, as expected for a low-spin d(6) Ru(II)-type complex. The molecular structure of cis-fac-Delta-(R)-(S)-2, consists of a nonsymmetric complex, where the Ru metal center has a significantly distorted octahedral-type coordination because of the bulkiness of the (S)-BINAP ligand. cis-fac-Delta-(R)-(S)-2 has a remarkable catalytic performance at P = 6.8 atm of H2 and T = 70 degrees C toward the hydrogenation of prochiral double bonds both from efficiency and from stereoselectivity viewpoints. As an example, prochiral olefins of technological interest such as dimethyl itaconate, methyl 2-acetamidoacrylate or methyl 2-acetamidocinnamate are catalytically hydrogenated by cis-fac-Delta-(R)-(S)-2, with conversions higher than 99.9% and ee > 99. Furthermore, cis-fac-Delta-(R)-(S)-2, also catalyzes the selective hydrogenation of beta-keto esters, although the reaction rates are lower than those found with the former substrates.

Poly(ethylene oxide)-based surfactants as templates for the synthesis of mesoporous silica materials.

Various mesoporous silica solids were prepared by using poly(ethylene oxide)-based surfactants as templates in a neutral, fluoride, or moderately acidic medium, and their properties examined by different physical techniques. Precipitation in an acid or neutral medium provided materials of pore size in between those of micropores and mesopores irrespective of the molecular size of the surfactant. On the other hand, syntheses in a fluoride-containing medium yielded mesoporous materials with pore diameters over the range 36-84 A that increased with increasing surfactant size. All materials possessed specific surface areas above 650 m(2)g(-1) and high pore volumes-particularly those obtained in a fluorinated medium. The conditions used in the syntheses and the fact that all produced highly disordered porous materials suggest that their mechanism of formation is essentially of the N(0)I(0) neutral type. The materials obtained in the presence of fluoride ion, which promote the condensation of siliceous species, retain greater amounts of surfactant and exhibit increased cross-linking and decreased particle sizes, which results in textural mesoporosity.

Synthesis and Characterization of Basic Catalysts Based on Sodium-Magnesium Mixed Phosphates and Their Use in the Conversion of 2-Hexanol.

Various catalysts consisting of sodium-magnesium mixed orthophosphates were synthesized and characterized in structural terms using X-ray diffraction, thermogravimetric analysis, differential thermal analysis, diffuse reflectance infrared spectroscopy, and solid-state (31)P NMR spectroscopy. In addition, the surface properties of the solids were determined from N(2) adsorption-desorption isotherms and their chemical properties characterized with various titrants. One of the solids obtained consists of NaMgPO(4)/Mg(2)P(2)O(7) and the rest of NaMgPO(4)/MgO. Their surface chemical properties vary depending on the particular synthetic procedure used; thus, the NaMgPO(4)/MgO systems exhibit similar populations of acid and basic sites, whereas the NaMgPO(4)/Mg(2)P(2)O(7) systems contain many more acid sites than basic sites. All the solids obtained exhibit substantial dehydrogenating activity in the conversion of gaseous 2-hexanol; in fact, some of the NaMgPO(4)/MgO systems are even more active and selective than a MgO solid tested under identical reaction conditions. Copyright 2001 Academic Press.

Activity of Basic Catalysts in the Meerwein-Ponndorf-Verley Reaction of Benzaldehyde with Ethanol.

The Meerwein-Ponndorf-Verley (MPV) reaction of benzaldehyde with ethanol in the liquid phase in the presence of basic catalysts consisting of magnesium oxide, calcium oxide, and mixed oxides obtained by calcination of layered double hydroxides, was studied. The catalysts were characterized using various techniques including X-ray diffraction and gas adsorption (viz nitrogen physisorption to determine textural properties and carbon dioxide chemisorption to elucidate surface basic properties). The catalyst consisting of calcium oxide, which was that possessing the highest density of basic sites, was found to be the most active in the process; the MPV reaction was accompanied by two other, competing reactions (viz aldol condensation and the Tishchenko cross-reaction). The MPV reaction of benzaldehyde with other alcohols was also examined, the highest conversion being obtained with secondary alcohols as hydrogen sources. Copyright 2001 Academic Press.