Search results for "Chemical decomposition"
showing 10 items of 31 documents
Electron Accumulative Molecules.
2018
With the goal to produce molecules with high electron accepting capacity and low reorganization energy upon gaining one or more electrons, a synthesis procedure leading to the formation of a B–N(aromatic) bond in a cluster has been developed. The research was focused on the development of a molecular structure able to accept and release a specific number of electrons without decomposing or change in its structural arrangement. The synthetic procedure consists of a parallel decomposition reaction to generate a reactive electrophile and a synthesis reaction to generate the B–N(aromatic) bond. This procedure has paved the way to produce the metallacarboranylviologen [M(C2B9H11)(C2B9H10)-NC5H4-…
Specifications for carbonate content quantification in recent marine sediments using Rock-Eval pyrolysis
2019
11 pages; International audience; The amount of CaCO3 in sediments and/or sedimentary rocks is usually measured by calcimetry while the nature of the carbonates is determined by X-ray diffraction. Recently, a carbonate recognition method based on the results of Rock-Eval pyrolysis was proposed in 2014 by Pillot et al. [1]. Rock-Eval pyrolysis is also widely used for the characterization of recent sediments. However, later in 2015 Baudin et al. [2] noticed that some of the characteristics of recent sediments tended to produce different results from those of more classical Rock-Eval analyses, causing bias in interpretations.In this study, the thermal stability of fossil and recent marine carb…
Influence of Phase Modifiers on the Degradation of Tri-n-octylamine/dodecane Extracting Mixture by an Acidic Solution of Vanadium (V)
2012
The kinetics of degradation of a mixture of tri-n-octylamine (extractant) and various alcoholic phase modifiers in n-dodecane in contact with acidic aqueous sulfate solutions containing vanadium (V) has been investigated. The nature of the modifier influences the kinetics of degradation and an improvement of the resistance against the chemical degradation is obtained when secondary alcohol (2-nonanol) or tertiary alcohols such as 9-octyl-9-heptadecanol are used as phase modifiers instead of 1-tridecanol. For instance, the kinetic constant of degradation is divided by one half when 9-octyl-9-heptadecanol is used as phase modifier instead of 1-tridecanol. On the contrary, the alcohols contain…
Pressure-induced chemical decomposition of copper orthovanadate (α-Cu3V2O8)
2021
The high pressure stability of α-Cu3V2O8 has been investigated via complementary high pressure synchrotron X-ray diffraction experiments and theoretical density functional theory calculations. The results of both experiment and theory are in close agreement. The main result of this work is that α-Cu3V2O8 undergoes a pressure-induced chemical decomposition into CuO and V2O5 at a modest pressure of ∼1.35 GPa according to the experimental observations, and at ∼2.45 GPa according to the calculations. The decomposition is investigated with enthalpy calculations and one of the main driving factors is the stability of the octhedral oxygen-coordination of the metal atoms in the decompositon product…
Volatile compounds extracted from polypropylene pellets by hot water: influence of the level of the peroxide agents
1992
To improve the quality level of plastic packaging materials, we determined the influence of chemical degradation of polypropylene (PP) upon the amount of volatile components extracted by hot water from PP pellets. Two formulations were analyzed and compared: PP CR (degraded) and PP (not degraded). After Likens-Nickerson's extraction of the pellets and concentration of the extract, an HPLC fractionation was made to collect three fractions of different poiarities: a pentane (A), a dichloromethane (B), and an ether (C) fraction. Fractions (B) and (C) were olfactively evaluated by GC sniffing to be most interesting. Their analysis by GC/MS coupling allowed the identification of different compon…
Nachweis des di-2-cyanoisopropylperoxides bei der zersetzung von azoisobuttersäuredinitril in gegenwart von sauerstoff
1970
Das Di-2-cyanoisopropylperoxid entsteht in etwa 5-proz. Ausbeute bei der Zersetzung von Azoisobuttersaredinitril unter Sauerstoff in Isobutyronitril als Losungsmittel. Thermisch zerfallt das Peroxid est oberhalb von 120°C mit mesbarer Geschwindigkeit in einer Reaktion erster Ordnung. Die Aktivierungsenergie, in Cumol als Losungsmittel, wurde zu 37,9 kcal · mol−1 bestimmt. Werte fur die Zerfallskonstante bei 140°C sind in Cumol 0,057 h−1, in tert-Butylbenzol 0,073 h−1, in Chlorbenzol 0,18 h−1 und in o-Dichlorbenzol 0,23 h−1. Di-2-cyanoisopropylperoxide is formed when azobisisobutyronitrile is decomposed under oxygen in isobutyronitrile as a solvent. The yield amounts to ca. 5%. Thermal decom…
Development of an ICP-IDMS method for accurate routine analyses of toxic heavy metals in polyolefins and comparison with results by TI-IDMS
2000
An inductively coupled plasma isotope dilution mass spectrometric (ICP-IDMS) method was developed as a suitable method - with respect to its sensitivity, precision, accuracy, and time-consumption - for the analysis of toxic heavy metal traces (Pb, Cd, Cr, and Hg) in polyolefins. Results for Pb, Cd, and Cr were compared with those obtained by thermal ionization isotope dilution mass spectrometry (TI-IDMS), which was used as a reference method. Because of its high first ionization potential and its high volatility mercury could not be determined by TI-IDMS. A multi-element spike solution, containing isotopically enriched 206Pb, 116Cd, 53Cr, and 201Hg, was used for the isotope dilution step. D…
A molecular electron density theory study of the Lewis acid–catalyzed decomposition reaction of nitroethyl benzoate using aluminum derivatives
2019
Photocatalytic behavior of mixed WO3/WS2 powders
2000
Polycrystalline mixed WO3/WS2 powders have been prepared by different methods. The samples have been characterized by bulk and surface techniques and tested as catalysts for the photodegradation of phenol. The results have indicated that the coupling of WO3 and WS2 leads to an enhanced rate of disappearance of the organic substrate. The effect is explained as the result of the simultaneous electron transfer from WS2 to WO3 and hole transfer from WO3 to WS2. The efficiency of the mixed WO3/WS2 systems strongly depends on the relative amounts of WO3 and WS2 in the various samples. A maximum of photoactivity is obtained when the surface WS2 and WO3 molar fraction is about 0.5.
Degradation half-life times of PCDDs, PCDFs and PCBs for environmental fate modeling.
2000
Literature search of the knowledge on the degradation of persistent organic pollutants (POPs) in environmental compartments air, water, soil and sediment was done in purpose to find properties of POPs of interest for modeling. One degradation process, hydrolysis (chemical degradation), was omitted as negligibly slow for POPs studied. The other two, photolysis and biodegradation processes, were considered separately in purpose to develop estimation procedures. The estimates can be given as pseudo first-order rate constants kP for photolysis and kB for biodegradation. For each compartment, an overall degradation rate is k(tot) = kP + kB and lifetime t(1/2) = ln 2/k(tot). The latter values, li…