Reactivity studies, transition metal vanadium

Vanadium oxide dispersed on supporting oxides (Si02 Al Oo, Ti02, etc.) are frequently employed as catalysts in reactions like partial oxidation and ammoxidation of hydrocarbons, and NO reduction. The modifications induced on the reactive properties of transition metal oxides like V20 when they are supported on an oxide carrier has been the subject matter of recent study. There is much evidence showing that the properties of a thin layer of a transition metal oxide interacting with the support are strongly modified as compared to the properties of the bulk oxide (1-3). In the recent past, increasing attention has been focussed... 

In this way, the indenyl tethered NHC complexes of yttrium, lutetiiim and scandium were synthesised [135] each still bearing two potentially reactive trimethylsilylmethyl substituents. The potential as single component or cationic (after activation with MAO) catalysts for the polymerisation of olefins was pointed out by the authors, but no studies have as yet been reported. The same can of course be said about the corresponding early transition metal complexes of titanium, zirconium, vanadium and chromium [134,136] where the synthesis of the proligands and the transition metal complexes were reported, but no catalytic studies performed. 

As this review is intended to illustrate, the interplay between metal and oxygen leads to a richness of reactivity that is reflected in the surface structure of oxides. Much of this richness can be rationalised as varying proportions of ionic and covalent character in the metal-oxygen bonding, and is manifest in a variety of non-stoichiometric surfeces. We therefore focus on the prototypical transition metal oxide smface rutile Ti(>2 (1 1 0). This is contrasted with computational results for one of the most widely-studied p-block oxide surfaces - corundum Al2O3-(0 0 0 1) - and we refer also to computational surface studies on oxides of ruthenium, iron, vanadium, tin and silver, as well as ternary oxides. 

A review of recent advances in transition-metal-catalysed oxidations by molecular oxygen has highlighted the scope and limitations, as well as the meehanisms of these reactions. " " An overview of the fundamental studies on a new method of synthesis of nicotinic acid by the gas-phase catalytic oxidation of -picoline by oxygen has been presented. The reactivity of vanadium species has been considered in order to discover the nature of the active catalyst. Kinetic equations for -picoline oxidation on vanadia-titania catalysts have been discussed. " The effect of quaternary ammonium salts or macrocyclic ethers on the autoxidation of ethylbenzene or the decomposition of the a-phenylethyl hydroperoxide intermediate catalysed by Ni(II) or Fe(III) acetylacetonates has been reviewed. ... 

In eomparative in vitro and in vivo studies, oil ash is typically more toxic than other ashes, and its toxieity is largely related to its high content of transition metals, particularly iron, nickel, and vanadium (63,67). Hauser et al. (68) reviewed the literature on short-term effects of exposure to oil ash among boiler workers and reported a new prospective study of the effects of working on oil boilers on respiratory function. Exposure to oil ash causes reduced function measured by spirometry, but no ehanges were observed in airway reactivity. There is little epidemiological information on the long-term effects of occupational exposures to inhaled oil ash. 

Particle exposure has been specifically linked to induction of pulmonary inflammation. Amdur and Chen (25) reported increased neutrophil numbers and increased bronchoalveolar lavage (BAL) protein following exposure to acid-coated particles. Exposure to fly ash, a model of outdoor air pollution, induces severe pulmonary inflammation (26) marked by increased numbers of neutrophils (27) and increased lavageable protein (26). Interestingly, the observed pulmonary inflammation has been specifically related to the metal content of the fly ash particle, particularly iron, nickel, and vanadium (26). Other studies have pointed to the effectiveness of these transition metals in inducing reactive oxygen species (ROS) in lung cells (28,29). 

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