Search results for "Formaldehyde"

Synthesis of phenol–formaldehyde resole resins in the presence of tetraalkylammonium hydroxides as catalysts

2000

Abstract We synthesised phenol–formaldehyde resole resins in the presence of tetraalkylammonium hydroxides as catalysts. The activity of these catalysts was compared with the activity of sodium hydroxide. Gas chromatography, thin layer chromatography, 13 C NMR spectrometry, potentiometric titration and a few simple physicochemical methods were used to estimate the composition of the obtained resins and their properties. It was concluded from these studies that tetraalkylammonium hydroxides are active catalysts and the resins obtained in their presence show some interesting properties.

Measurement report: Photochemical production and loss rates of formaldehyde and ozone across Europe

2021

Various atmospheric sources and sinks regulate the abundance of tropospheric formaldehyde (HCHO), which is an important trace gas impacting the HOx (≡ HO2 + OH) budget and the concentration of ozone (O3). In this study, we present the formation and destruction terms of ambient HCHO and O3 calculated from in situ observations of various atmospheric trace gases measured at three different sites across Europe during summertime. These include a coastal site in Cyprus, in the scope of the Cyprus Photochemistry Experiment (CYPHEX) in 2014, a mountain site in southern Germany, as part of the Hohenpeißenberg Photochemistry Experiment (HOPE) in 2012, and a forested site in Finland, where measurement…

"Partial oxidation of methane and methanol on FeOx-, MoOx- and FeMoOx -SiO2 catalysts prepared by sol-gel method: a comparative study"

2020

[EN] FeOx-, MoOx and FeMoOx-SiO2 materials prepared by a sol-gel procedure have been evaluated as catalysts for the partial oxidation of methane and methanol. The effect of decreasing the pH of the synthesis gel on the chemical nature of FeOx and MoOx species has been investigated. Characterization results show that low pH improves the dispersion of metal oxide species present in SiO2 matrix. For FeOx/SiO2 materials, the presence of dispersed FeOx species (rather than bulk Fe2O3) improves the selectivity to formaldehyde in the partial oxidation of methane and methanol. For FeMoOx/SiOx catalysts, dispersed species favor the selectivity to formaldehyde only for methane oxidation. In contrast,…

The Zwitterion [8,8′-μ-CH2O(CH3)-(1,2-C2B9H10)2-3,3′-Co]0 as a Versatile Building Block To Introduce Cobalt Bis(Dicarbollide) Ion into Organic Molecu…

2012

The synthesis of a new bridged [8,8′-μ-CH2O(CH3)-(1,2-C2B9H10)2-3,3′-Co]0 derivative (2), arising from the acid-catalyzed reaction of cobalt bis(1,2-dicarbollide)(1−) ion with formaldehyde, is reported. The proposed reaction path is supported by the isolation of side products including two zwitterionic compounds, the known bridged [8,8′-μ-(CH3O)-(1,2-C2B9H10)2-3,3′-Co]0 derivative (3), the new zwitterion [(8-(CH3)2O-1,2-C2B9H10)-(1′,2′-C2B9H11)-3,3′-Co]0 (4), and two anionic compounds—the known [(8,8′-Cl2-1,2-C2B9H10)2-3,3′-Co]− and the newly characterized dimethoxy derivative [(8,8′-(CH3O)2-1,2-C2B9H10)2-3,3′-Co]− of the cobalt bis(dicarbollide) ion. Compound 2 serves as a versatile buildi…

Visible-light driven oxidation of gaseous aliphatic alcohols to the corresponding carbonyls via TiO2 sensitized by a perylene derivative

2013

Sensitized P25 TiO2 was prepared by wet impregnation with a home-prepared perylene dye, i.e., N,N?-bis(2-(1- piperazino)ethyl)-3,4,9,10-perylene-tetracarboxylic acid diimide dichloride (PZPER). Energy levels of PZPER were found to be compatible with those of TiO2 allowing fast electron transfer. The obtained catalyst has been characterized and used in the gas-phase partial oxidation of aliphatic primary and secondary alcohols, i.e., methanol, ethanol, and 2- propanol. The reaction was carried out under cut-off (?> 400 nm) simulated solar radiation in O2 atmosphere. The perylene derivative allowed a good absorbance of visible radiation thanks to its low optical energy gap (2.6 eV) which was …

Indefinitely stable iron(IV) cage complexes formed in water by air oxidation

2017

In nature, iron, the fourth most abundant element of the Earth's crust, occurs in its stable forms either as the native metal or in its compounds in the +2 or +3 (low-valent) oxidation states. High-valent iron (+4, +5, +6) compounds are not formed spontaneously at ambient conditions, and the ones obtained synthetically appear to be unstable in polar organic solvents, especially aqueous solutions, and this is what limits their studies and use. Here we describe unprecedented iron(IV) hexahydrazide clathrochelate complexes that are assembled in alkaline aqueous media from iron(III) salts, oxalodihydrazide and formaldehyde in the course of a metal-templated reaction accompanied by air oxidation…

Solid state NMR investigation of the roman Acqualadroni rostrum: tenth year assessment of the consolidation treatment of the wooden part

2020

Abstract: This work follows a previous one dealing with the state of conservation study of the wooden part of the roman Acqualadroni rostrum soon after its finding in the seabed of Acqualadroni (Messina, Italy). The archaeological survey and recovery were particularly relevant since this artefact is one of the two rostrums, nowadays known,found together with its wooden part. Following the recovery, it was consolidated by immersion in a melamine-formaldehyde resin (Kauramin) aqueous solution for eight months at the “Centro di Restauro del Legno Bagnato” (Pisa, Italy). The present investigation is aimed to determine at microscopic scale the wood state of conservation and to highlight interact…

2017

Abstract. Deep convection is an efficient mechanism for vertical trace gas transport from Earth's surface to the upper troposphere (UT). The convective redistribution of short-lived trace gases emitted at the surface typically results in a C-shaped profile. This redistribution mechanism can impact photochemical processes, e.g. ozone and radical production in the UT on a large scale due to the generally longer lifetimes of species like formaldehyde (HCHO) and hydrogen peroxide (H2O2), which are important HOx precursors (HOx =  OH + HO2 radicals). Due to the solubility of HCHO and H2O2 their transport may be suppressed as they are efficiently removed by wet deposition. Here we present a case …

Determination of DNA single strand breaks and selective DNA amplification by N-nitrodimethylamine and analogs, and estimation of the indicator cells'…

1986

N-nitrodimethylamine is metabolized oxidatively to N-nitrohydroxymethylmethylamine, which decomposes to yield formaldehyde and N-nitromethylamine. All four compounds and N-nitromethylamine were tested for their ability to induce DNA single strand breaks in hepatocytes and in SV 40-transformed Chinese hamster embryo cell lines. Only the two monoalkylnitramines were positive. They induced single strand breaks in hepatocytes, but were not effective in the other cells. Formaldehyde and N-nitrohydroxymethylmethylamine were toxic to the cells. None of the compounds tested was able to induce selective DNA amplification in the two transformed cell lines. Enzymes involved in drug metabolism were ass…

Draft genome of a novel methanotrophic Methylobacter sp. from the volcanic soils of Pantelleria Island

2021

AbstractThe genus Methylobacter is considered an important and often dominant group of aerobic methane-oxidizing bacteria in many oxic ecosystems, where members of this genus contribute to the reduction of CH4 emissions. Metagenomic studies of the upper oxic layers of geothermal soils of the Favara Grande, Pantelleria, Italy, revealed the presence of various methane-oxidizing bacteria, and resulted in a near complete metagenome assembled genome (MAG) of an aerobic methanotroph, which was classified as a Methylobacter species. In this study, the Methylobacter sp. B2 MAG was used to investigate its metabolic potential and phylogenetic affiliation. The MAG has a size of 4,086,539 bp, consists …