China
Africa
Explore chapters and articles related to this topic
Catalytic Oxidations with Air for Clean and Selective Transformations of Polyols
Published in Mike G. Scaros, Michael L. Prunier, Catalysis of Organic Reactions, 2017
Pierre Gallezot*, Michèle Besson, Fabienne Fache
In the last few years we have conducted research on three catalytic oxidation reactions with air for the synthesis of specialty chemicals, namely: (i) the oxidative dehydrogenation of ethylene glycol into glyoxal on silver catalysts1 which is used concurrently with the nitric acid oxidation of acetaldehyde2, (ii) the glyoxal oxidation into glyoxylic acid on supported platinum catalysts3,4 which might substitute the nitric acid oxidation of glyoxal5, (iii) the glucose oxidation to gluconic acid on supported palladium catalysts6,7 which might soon replace the enzymatic route. In the present paper the main results of studies (ii) and (iii) will be reported and discussed.
New insights in sources of the sub-micrometre aerosol at Mt. Zeppelin observatory (Spitsbergen) in the year 2015
Published in Tellus B: Chemical and Physical Meteorology, 2019
Matthias Karl, Caroline Leck, Farshid Mashayekhy Rad, Are Bäcklund, Susana Lopez-Aparicio, Jost Heintzenberg
Observations show that dicarboxylic acids like oxalic acid are commonly found in the organic fraction of secondary aerosol in marine environments (e.g. Mochida et al., 2003). Oxal is one of the main identified single organic particle mass components. Oxal forms in cloud processing or chemical ageing of VOCs from biogenic and anthropogenic sources. In the marine atmosphere, the aqueous phase oxidation of glyoxal in clouds is an important pathway leading to particulate Oxal. Glyoxal results from the gas-phase oxidation of acetaldehyde and toluene and the oxidation of glycolaldehyde (Warneck, 2003), for which methylvinylketone (MVK) is the most important precursor. MVK is one of the main isoprene oxidation products. As shown by Lim et al. (2005) this pathway links isoprene, emitted from trees and to a smaller extent from oceanic phytoplankton (e.g. Spracklen et al., 2008), and oxalic acid. Chang et al. (2011) previously identified in the PMF analysis of the aerosol measurements using an aerosol mass spectrometer (AMS) during the Arctic Summer Cloud Ocean Study (ASCOS) expedition an aged organic component in a PMF-factor that they interpreted as continental source, consistent with aerosol that has been extensively oxidised in the atmosphere with long residence time (Ng et al., 2010).
5-Hydroxymethyl furfural modified melamine glyoxal resin
Published in The Journal of Adhesion, 2020
Xuedong Xi, Jingjing Liao, Antonio Pizzi, Christine Gerardin, Siham Amirou, Luc Delmotte
Compared to formaldehyde, glyoxal is less volatile (boiling point 51°C) and is non-toxic. Moreover, also its mature production technology, low cost, and easy biodegradation render it widely used in the clothing and paper industry as a wet-resistance enhancer and crosslinker.[7] In wood adhesives, glyoxal has been generally used to substitute partially or totally formaldehyde in biosourced adhesives such as tannin adhesives,[8,9] lignin adhesives and protein adhesives.[10,11] However, few works in the literature report the use of glyoxal alone for wood adhesives. Recently, glyoxal and urea have been successfully used to synthesize urea-glyoxal (UG) resins used as binders for plywood.[12] To solve the problem of high activation energy of curing of UG resins, acid ionic liquids have been used as hardeners, thus reducing the curing temperature of UG resins and improve their bonding performance to allow their use as particleboard binders.[13] However, as UF resins, UG resins still have the defect of presenting a relatively poor water resistance. Melamine is generally used to improve the bonding performance and water resistance of urea-based resins. Moreover, the synthesis and structure characterization of melamine-glyoxal (MG) resin have been studied, and an MG resin used for bonding plywood and particleboard has been developed.[14] The disadvantages of high curing temperature and poor water resistance are however still present. To obtain a better water resistance the MG resin was modified by reacting it with a small proportion of glutaraldehyde (G’) to yield a melamine-glyoxal-glutaraldehyde (MGG’) adhesive.[15] By the use of ionic liquids (IL) as resin hardeners and additives, plywood with good water resistance and bonding properties was prepared with it.[15] Due to the lower reactivity of glyoxal compared to formaldehyde, the performances of the MG resin alone was not as good as expected.