Search results for "DIOXIDE"

ChemInform Abstract: Homogeneous Metal-Based Catalysis in Supercritical Carbon Dioxide as Reaction Medium

2016

Above 31.1 °C and 73.8 bar, carbon dioxide reaches the supercritical state, being transformed into a fluid (scCO2) that has attracted interest in the last few decades as reaction medium for several transition-metal-catalyzed organic transformations. The main feature of this fluid rests on its capability to dissolve large amounts of other gases such as hydrogen, carbon monoxide, ethylene, or even methane and light alkanes. In this manner, very high concentrations of these reactants are available for catalysis. In this contribution a review of the main achievements of the use of transition-metal complexes as catalysts in scCO2 is presented.

Carbon Dioxide as Chemical Feedstock. Edited by Michele Aresta.

2010

Recent Scientific and Technological Developments in Electrochemical Carboxylation Based on Carbon Dioxide

2010

Electrochemical Syntheses Involving Carbon Dioxide

1990

The recent developments of electrosynthetic processes involving carbon dioxide are reviewed. Both processes involving carbon dioxide alone and electrocarboxylations are taken under consideration. The first of these two fields, mainly projected towards the production of basic chemicals such as methanol or carbon monoxide, is at present at a stage of fundamental research. Some interesting developments have recently appeared in the literature, concerning the use of electrode materials, or of transition metal complexes with particular catalytic activity. Electrocarboxylations are at a stage of more applicative development: some processes have reached the stage of pilot plant, and other have int…

Photoinduced Charge Separation of Self-Organized Semiconducting Superstructures Composed of a Functional Polymer-TiO2 Hybrid

2013

Defects in oxide glasses

2005

An insight into the present understanding of point defects in the simplest and the most radiation-resistant oxide glass, glassy silicon dioxide (silica) is presented. The defects and their generation processes in glassy and α-quartz forms of silicon dioxide are significantly different. The only defect, confirmed to be similar in both materials, is oxygen vacancy. In silica, additional defects of dangling bond type are generated from precursor sites formed by strained Si-O bonds, and by modifier ions. The optical absorption spectra of silica are dominated by paramagnetic dangling bond type defects: silicon dangling bond (“E′-center”) and oxygen dangling bond (“non-bridging oxygen hole center…

Biosilica

2012

Biomineralization, biosilicification in particular (i.e. the formation of biogenic silica, SiO(2)), has become an exciting source of inspiration for the development of novel bionic approaches following 'nature as model'. Siliceous sponges are unique among silica-forming organisms in their ability to catalyze silica formation using a specific enzyme termed silicatein. In this study, we review the present state of knowledge on silicatein-mediated 'biosilica' formation in marine demosponges, the involvement of further molecules in silica metabolism and their potential applications in nano-biotechnology and bio-medicine. While most forms of multicellular life have developed a calcium-based skel…

CO2 as a C1-Building Block for Dialkyl Carbonate Synthesis

2002

Carbon dioxide, one of the major man-made greenhouse gas, is a renewable resource of carbon which can be viewed as a C1 synthon to build valuable chemicals. The development of new applications is of major interest considering CO2 conversion and environmentally friendly reactions. As chemical catalysis offers interesting options, we are studying the molecular design of catalysts for the formation of dialkyl carbonates from alcohols and CO2. This paper reports results on the mechanistic approach for dialkyl carbonate formation with alkoxybutyl tin(IV) compounds. The insertion of CO2 into Sn-OR bonds (R = Me, 1Pr) occurs at atmospheric pressure and room temperature leading to alkylcarbonato ti…

ChemInform Abstract: Baeyer-Villiger Oxidation of Ketones with a Silica-Supported Peracid in Supercritical Carbon Dioxide under Flow Conditions.

2009

[2-Percarboxyethyl]-functionalized silica reacts with ketones in supercritical carbon dioxide at 250 bar and 40 °C under flow conditions to yield the corresponding esters and lactones. The solid reagent can be easily recycled through treatment with 70% hydrogen peroxide in the presence of an acid at 0 °C. This procedure not only simplifies the isolation of the reaction products, but has the advantage of using only water and carbon dioxide as solvents under mild conditions.

Taurine and the Lung

2003

Taurine (TAU) is the most abundant free amino acid in many tissues and in particular in proinflammatory cells like polymorphonuclear leukocytes and tissues exposed to elevated levels of oxidants1. Furthermore, orally administered TAU has been reported to reduce lung oxidant damage from exposure to ozone, nitrogen dioxide, paraquat, amiodarone and bleomycin in animal models2–5.