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Decomposition Products (decomposition + products)
Selected AbstractsRare Earth Benzotriazolates: Coordination Polymers Incorporating Decomposition Products from Ammonia to 1,2-Diaminobenzene in,1[Ln(Btz)3(BtzH)] (Ln = Ce, Pr), ,1[Ln(Btz)3{Ph(NH2)2}] (Ln = Nd, Tb, Yb), and ,1[Ho2(Btz)6(BtzH)(NH3)],EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2006Klaus Müller-Buschbaum Abstract The solvent-free melt reactions of benzotriazole (BtzH, C6H4N2NH) with rare earth metals result in three different types of benzotriazolate coordination polymers. Early 4f metals yield ,1[Ln(Btz)3(BtzH)] [Ln = Ce (1), Pr (2)], from neodymium to ytterbium the type ,1[Ln(Btz)3{Ph(NH2)2}] is observed [Ln = Nd (3), Tb (4), Yb (5)], whereas the late 4f metal Ho gives ,1[Ho2(Btz)6(BtzH)(NH3)] (6). Depending on the reaction conditions and the respective rare earth element, ligand fragments originating from decomposition products are incorporated in the coordination polymers. Compounds 1,3 and 6 were obtained as single crystals and their crystal structures determined by single-crystal X-ray analysis, whilst 4 and 5 were obtained as powders. X-ray powder diffraction shows the isotypic character of polymers 3, 4, and 5. The benzotriazolates contain trivalent lanthanide ions with complete nitrogen coordination. Decomposition of the ligand accompanies the formation of the coordination polymers. X-ray analysis was combined with thermal analysis and mass spectrometry to investigate the influence of reaction temperatures on ligand decomposition. Ln-benzotriazolates exhibit aspects of materials science such as luminescence {5D4,7FJ, J = 4,6 for ,1[Tb(Btz)3{Ph(NH2)2}] (4)} without quenching by concentration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] High-Temperature Hydroxylation and Surface Corrosion of 2/1-Mullite Single Crystals in Water Vapor EnvironmentsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006Nadine Eils 2/1-mullite single crystal (001) plates with thicknesses between 0.9 and 1.9 mm were exposed for 1.5, 3, 6, and 12 h at 1670°C to a slowly flowing (100 mL/min) water-rich gas mixture (O2/H2O 80/20). Under the given experimental conditions, 2/1-mullite yielded significant amounts of structurally bound OH groups across the bulk and decomposition of the crystal surface on a micrometer scale. Decomposition products are (i) sodium-containing silicon-rich alumino silicate glass formed from melt and (ii) ,-alumina, which crystallizes within melt cavities. The crystal plates that are free of any OH absorption before the corrosion experiments show a steep increase in OH absorption intensity up to 3 h of corrosion and a flattening toward longer times of exposure. The evaluation of OH intensity profiles implies an effective diffusion coefficient DH in the range between 1.5 and 2.5 × 10,7 cm2/s. [source] Cracking study of pentakis(dimethylamino)tantalum vapors by Knudsen cell mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2010Perrine Violet Organometallic molecules are commonly used as gaseous precursors in Atomic Layer Deposition/Chemical Vapor Deposition (ALD/CVD) processes. However, the use of these molecules, which are generally thermally unstable at temperatures close to the deposition temperature, requires an understanding of their gas-phase chemical behavior. The thermal cracking of the gaseous precursor, pentakis(dimethylamino) tantalum (PDMAT), generally adopted in the ALD/CVD TaN deposition processes, has been studied in the temperature range from 343 to 723K using a specific reactor coupled with a high-temperature mass spectrometer. This reactor , built as tandem Knudsen cells , consists of two superimposed cells. The first stage reactor , an evaporation cell , provides an input saturated vapor flow operating from room temperature to 333K. The second stage cell, named the cracking cell, operated from 333 to 723K in the present study. Experiments showed the appearance of many gaseous species when the cracking temperature increased and, in particular, dimethylamine, corresponding to the saturated organic branches of PDMAT. Decomposition products of the HNC2H6 branch were observed at relatively high temperature, namely above 633K. This gas-phase study , as for the preceding saturated one , shows the presence of oxygen-containing molecules in PDMAT cracked vapor. Thus, it explains the systematic presence of oxygen contamination in the deposited TaN films observed in ALD/CVD industrial processes. Copyright © 2010 John Wiley & Sons, Ltd. [source] Microbiological evaluation of toxicity of three polycyclic aromatic hydrocarbons and their decomposition products formed by advanced oxidation processesENVIRONMENTAL TOXICOLOGY, Issue 3 2003Teresa Jamroz Abstract The toxicity of benzo[a]pyrene, chrysene, and fluorene and their decomposition products formed by advanced oxidation processes (AOPs) was investigated using biotests with Escherichia coli and Vibrio fischeri. The polycyclic aromatic hydrocarbons (PAHs) were not highly toxic to either bacterial strain; the toxicity of their degradation products depended on the method of chemical processing. Inhibition of more than 27% was observed with products formed by oxidation of the PAHs, by AOP methods without hydrogen peroxide. Toxicity as high as 100% was observed after the combined action of hydrogen peroxide and other oxidizing agents. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 187,191, 2003 [source] Stability and detection of ,-pinene oxide in aqueous culture mediumENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2000Kimberly K. Kajihara Abstract Methane consumption by methanotrophic bacteria was previously shown to be temporarily inhibited by ,-pinene. Based on literature considerations, loss of inhibition may be due to bacterial degradation of the monoterpene to ,-pinene oxide, an anticipated metabolite. However, since ,-pinene oxide is unstable in aqueous media, detection of its production by methanotrophs or other bacteria is problematic. Therefore, we used gas chromatography-mass spectrometry analysis to study the chemical breakdown of ,-pinene oxide in various buffer systems (Tris[hydroxymethyl]am inomethane, 3-[N-morpholino]propanesulfonic acid, phosphate; pH 7-9) suitable for bacterial whole-cell and cell-free experiments. In every case, aqueous phase ,-pinene oxide was unstable and its disappearance was accompanied by the appearance of five decomposition products in a characteristic fingerprint that was in part buffer dependent. However, this fingerprint was adequately stable in phosphate buffer such that its appearance could be used to infer the intermediacy of ,-pinene oxide if produced by the bacteria at or near their optimal pH. [source] IR Laser-Induced Carbothermal Reduction of SilicaEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2008Markéta Urbanová Abstract Pulsed IR-laser irradiation of silica in the presence of gaseous hydrocarbons (benzene or ethyne) results in carbothermal reduction of silica by hydrocarbon decomposition products and allows deposition of amorphous solids which were analyzed by FTIR, Raman, X-ray photoelectron and Auger spectra and by electron microscopy and revealed as nanosized carbon,silicon oxycarbide composites containing crystalline silica domains. The reported IR laser-induced process is the first approach to deposition of nanosized carbon,silicon oxycarbide composites. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Electron-Sponge Behavior, Reactivity and Electronic Structures of Cobalt-Centered Cubic Co9Te6(CO)8 ClustersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008Mustapha Bencharif Abstract Extended investigations of the reaction sequence [Cp,2Nb(Te2)H]/CH3Li/[Co2(CO)8] (Cp, = tBuC5H4) led to the identification of Lin[3] {3 = [Co9Te6(CO)8]; n = 1, 2} salts through their transformation with [PPN]Cl into [PPN]n[3] (PPN = Ph3PNPPh3). These compounds form in the solid state columnar ([PPN][3]) or undulated 2D ([PPN]2[3]) supramolecular networks. Electrochemical studies of [Cp*2Nb(CO)2][3] (Cp* = C5Me5) or [Na(THF)6][3] revealed the presence of the redox couples [3],/[3]2,/[3]3,/[3]4,/[3]5, regardless of the nature of the cation, whereas in the anodic part oxidative degradation of the cluster takes place. This behavior is in agreement with the observation that [3], containing salts form with PPh3AuCl or dppe decomposition products like [(PPh3)2Au][CoCl3PPh3] or [Co(CO)2dppe]2(,-Te). A neutral cluster comprising the Co@Co8(,4 -Te)6 core formed in the reaction of [Cp*2Nb(CO)2][Co11Te7(CO)10] with PPh3AuCl, which gave [Co9Te6(CO)4(PPh3)4] (4) after oxidative cluster degradation and CO substitution. 4 was characterized by X-ray crystallography. DFT calculations carried out on all members of the [3]n (n = +1 to ,5) family and on related species indicate that there is no significant Jahn,Teller distortion (and therefore no connectivity change) for any of the considered electron counts. Magnetic investigations on [PPN][3] show that the ground state of [3], is a spin triplet with spins interacting antiferromagnetically in a 1D space.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Rare Earth Benzotriazolates: Coordination Polymers Incorporating Decomposition Products from Ammonia to 1,2-Diaminobenzene in,1[Ln(Btz)3(BtzH)] (Ln = Ce, Pr), ,1[Ln(Btz)3{Ph(NH2)2}] (Ln = Nd, Tb, Yb), and ,1[Ho2(Btz)6(BtzH)(NH3)],EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2006Klaus Müller-Buschbaum Abstract The solvent-free melt reactions of benzotriazole (BtzH, C6H4N2NH) with rare earth metals result in three different types of benzotriazolate coordination polymers. Early 4f metals yield ,1[Ln(Btz)3(BtzH)] [Ln = Ce (1), Pr (2)], from neodymium to ytterbium the type ,1[Ln(Btz)3{Ph(NH2)2}] is observed [Ln = Nd (3), Tb (4), Yb (5)], whereas the late 4f metal Ho gives ,1[Ho2(Btz)6(BtzH)(NH3)] (6). Depending on the reaction conditions and the respective rare earth element, ligand fragments originating from decomposition products are incorporated in the coordination polymers. Compounds 1,3 and 6 were obtained as single crystals and their crystal structures determined by single-crystal X-ray analysis, whilst 4 and 5 were obtained as powders. X-ray powder diffraction shows the isotypic character of polymers 3, 4, and 5. The benzotriazolates contain trivalent lanthanide ions with complete nitrogen coordination. Decomposition of the ligand accompanies the formation of the coordination polymers. X-ray analysis was combined with thermal analysis and mass spectrometry to investigate the influence of reaction temperatures on ligand decomposition. Ln-benzotriazolates exhibit aspects of materials science such as luminescence {5D4,7FJ, J = 4,6 for ,1[Tb(Btz)3{Ph(NH2)2}] (4)} without quenching by concentration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Identification of organic eluates from four polymer-based dental filling materialsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2003Vibeke Barman Michelsen Elution from polymer-based dental filling materials may have a potential impact on the biocompatibility of the materials. Since information from the manufacturers about ingredients in the materials often is incomplete, analyses of eluates from the materials are necessary for a better knowledge about possible harmful compounds. The aim of this study was to identify organic eluates from polymerized samples of two composites, one compomer and one resin-reinforced glass ionomer cement. Samples were immersed in ethanol or Ringer's solution. Organic leachables were analyzed by gas chromatography,mass spectrometry. Identification was confirmed with reference substances, if available. Among components detected were monomers, co-monomers, initiators, stabilizers, decomposition products and contaminants. Thirty-two substances were identified and 17 were confirmed with reference substances. From elution in Ringer's we identified 13 eluates from Tetric Ceram, 10 from Z250, 21 from Dyract and six from Fuji II LC; HEMA, HC and CQ were found in all samples. From elution in ethanol 12 eluates from Tetric Ceram, 18 eluates from Z250, 19 from Dyract and 10 from Fuji II LC were identified. The diversity of eluates from the four materials under study is demonstrated. Owing to variation between the materials, the biocompatibility including the allergenic potential may be different. [source] Regioselective Spiroannulations of ,-Acetyl LactonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2003Jens Christoffers Abstract Monocyclic spiroannulation precursors 3a,c were obtained by Michael reactions of ,-acetyl lactones 6a,c with methyl vinyl ketone (7). The selective formation of either regioisomer of both ,-oxo (5a,c) and ,-oxo (4a,c) lactones from 3a,c was achieved by varying the reaction conditions. The ,-oxo lactones 4a,c were obtained under basic (buffered) conditions in a pyrrolidine/AcOH system. Under acidic conditions, the annulation reaction afforded ,-oxo lactones 5a,c. Byproducts 8b,c were identified to be the decomposition products of ,-oxo lactones 5b and 5c by comparison with the spectra of the alcohols 10b,c derived directly from ,-oxo lactones 4b and 4c by saponification/decarboxylation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] The effect of temperature and ventilation condition on the toxic product yields from burning polymersFIRE AND MATERIALS, Issue 1 2008A. A. Stec Abstract A major cause of death or permanent injury in fires is inhalation of toxic gases. Moreover, every fire is unique, and the range of products, highly dependant on fire conditions, produces a wide variety of toxic and irritant species responsible for the most fire fatalities. Therefore, to fully understand each contribution to the toxicity it is necessary to quantify the decomposition products of the material under the test. Fires can be divided into a number of stages from smouldering combustion to early well-ventilated flaming through to fully developed under-ventilated flaming. These stages can be replicated by certain bench-scale physical fire models using different fuel-to-oxygen ratios, controlled by the primary air flow, and expressed in terms of the equivalence ratio (the actual fuel/air ratio divided by the stoichiometric fuel/air ratio). This work presents combustion product yields generated using a small-scale fire model. The Purser Furnace apparatus (BS7990 and ISO TS 19700) enables different fire stages to be created. Identification and quantification of combustion gases and particularly their toxic components from different fire scenarios were undertaken by continuous Fourier transform infrared spectroscopy. The relationship between type of the fire particularly the temperature and ventilation conditions and the toxic product yields for four bulk polymers, low-density polyethylene, polystyrene (PS), Nylon 6.6 and polyvinyl chloride (PVC) is reported. For all the polymers tested, except PVC, there is a dramatic increase in the yield of products of incomplete combustion (CO and hydrocarbons) with increase in equivalence ratio, as might be expected. For PVC there is a consistently high level of products of incomplete combustion arising both from flame inhibition by HCl and oxygen depletion. There is a low sensitivity to furnace temperature over the range 650,850°C, except that at 650°C PS shows an unexpectedly high yield of CO under well-ventilated conditions and PVC shows a slightly higher hydrocarbon yield. This demonstrates the dependence of toxic product yields on the equivalence ratio, and the lack of dependence on furnace temperature, within this range. Copyright © 2007 John Wiley & Sons, Ltd. [source] Photochemical cleavage of a tattoo pigment by UVB radiation or natural sunlightJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 7 2007Eva Engel Summary Background: Millions of people have at least one tattoo. Complex and light absorbing molecules are implanted in the skin. When tattooed skin receives UV radiation or natural sunlight, photochemical cleavage of the pigments may occur. As a first step, we dissolved pigments in a suitable solvent and analyzed them after light irradiation. Methods: The widespread Pigment Red 22 was dissolved in different solvents. The solutions were irradiated with either UVB radiation (up to 8 h) or with natural sunlight (110 days). After irradiation, the solutions were analyzed by means of liquid chromatography and mass spectrometry. Results: A clear cleavage of the pigment was detected in all solvents and the primary decomposition products were identified. In tetrahydrofuran and dioxane, the pigment concentration decreased significantly during UVB irradiation, whereas the pigment was completely destroyed during sunlight exposure. In chloroform and dichloromethane, the pigment concentration decreased slightly during UVB irradiation, whereas the pigment was almost completely destroyed during sunlight exposure. Conclusion: Since chloroform and dichloromethane do not affect the cleavage process, these solvents are optimal for such in vitro experiments. We have shown the cleavage of the tattoo pigment Red 22 when exposed to UVB radiation or natural sunlight. The decomposition products are hazardous showing a potential risk of being toxic or even carcinogenic. At present, a risk assessment is not feasible since the concentration of pigments and their decomposition products in skin are unknown. [source] A comparative in situ Rietveld refinement study: thermal decomposition and transformation of CoAl and CoZnAl layered double hydroxidesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2008Rune E. Johnsen Rietveld refinement based on in situ X-ray powder diffraction (XRPD) data was combined with thermogravimetric analysis (TGA) and mass spectrometry (MS) to study and compare the phase transformations, thermal stability, microstructural and structural changes of two cobalt-containing nitrate-based layered double hydroxides (LDHs) upon heating in a controlled inert atmosphere of nitrogen. The XRPD data were collected, using synchrotron X-ray radiation, with a time resolution of 107,s, which made it possible to carry out detailed structural studies of the initial layered double hydroxides as well as their decomposition products: spinel for a CoAl,NO3 LDH and spinel/zincite for a CoZnAl,NO3 LDH. Correlating these data with those from the TGA,MS analyses gives us information about the transformation mechanisms. Rietveld refinements of the two spinel phases reveal remarkable differences. The a axis of the spinel formed by decomposition of the CoAl,NO3 LDH increases almost linearly from approximately 598 to 1163,K, mainly due to the dominating thermal expansion, whereas the a axis of the spinel formed by decomposition of the CoZnAl,NO3 shows a more complex temperature dependency. Between approximately 698 and 1073,K, the a axis is almost constant due to pronounced chemical interaction with an additional amorphous phase and the zincite phase, whereas from 1073 up to 1163,K it increases linearly. Calculations, based on the results of the Rietveld refinements, of the size of the octahedral and tetrahedral coordination polyhedra in the spinel show that the octahedra shrink and the tetrahedra expand with increasing temperature. The unusual thermal behaviour of the octahedra is discussed and attributed to the low formation temperature of the cobalt aluminium spinel phase. Finally, the intensity of a low-angle scattering (LAS) signal observed in the XRPD patterns was correlated with the decomposition of the LDH, and determination of the specific surface areas gave the temperature-dependent BET surface areas. [source] Full Characterization and some reactions of 1-(2-adamantyl)-3-(1-adamantyl)aziridin-2-oneJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2008István Lengyel We found that 1-(2-adamantyl)-3- tert -butylaziridin-2-one (5a) is unstable. It slowly decomposes at room temperature, although detectable by IR spectroscopy (1840 cm,1 band in CCl4). On the other hand, a closely related analogue, 1-(2-adamantyl)-3-(1-adamantyl)aziridin-2-one (5b), is very stable, in concurrence with an earlier report [1]. We fully characterized aziridinone 5b, identified its thermal decomposition products (7 and 8) and reacted it with two aprotic ionic (tBuO, and HO,) and one protic non-ionic nucleophile (benzylamine). All three products (9b, 10, and 11) result from exclusive cleavage of the lactam (1-2) bond. [source] The role of the cyclic imide in alternate degradation pathways for asparagine-containing peptides and proteinsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2007Michael P. DeHart Abstract Peptides and proteins exhibit enhanced reactivity at asparagine residues due to the formation of a reactive succinimide intermediate that produces normal and isoaspartyl deamidation products along with significant racemization. This study examines the potential for attack of amine nucleophiles at the succinimide carbonyls to generate alternate decomposition products, depending on the nucleophile involved in the reaction. The reactions of the model peptides Phe-Asn-Gly (FNG) and Phe-isoAsn-Gly (FisoNG) were explored as a function of pH (8.5,10.5) in the presence and absence of ammonia buffer (0.2,2 M) using an isocratic HPLC method to monitor reactant disappearance and product formation. In addition to deamidation to form isoAsp and Asp peptides, two additional types of reactions were found to occur via the succinimide intermediate under these conditions. Back-reaction of the succinimide with ammonia led to peptide backbone isomerization while intramolecular attack by the amino terminus produced diketopiperazines. A kinetic model assuming a central role for the succinimide intermediate was derived to fit the concentration versus time data. These studies implicate the cyclic imide as a key intermediate in the formation of alternate peptide and protein degradants, including possible covalent amide-linked aggregates that may form from intermolecular attack of the cyclic imide by neighboring amino groups. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2667,2685, 2007 [source] 68 A new paradigm for the aphanizomenon bloom problem in upper klamath lakeJOURNAL OF PHYCOLOGY, Issue 2003E. C. Henry Upper Klamath Lake (UKL) is the largest lake in Oregon (area 287 km2, avg. depth 4.2 m). It is naturally eutrophic and regularly suffers nuisance summer blooms of cyanobacteria, principally Aphanizomenon flos-aquae (AFA). Sediment coring studies show that AFA was absent or minimal until about 1880 when a steady increase began, culminating in the blooms of recent decades. These studies show concomitant increases in sediment N (,20%) and P (,50%) along with shifts in the algal flora indicating increased eutrophication. These changes correlate with increased human impacts, such as deforestation, construction, roadbuilding etc., and especially the ditching, diking and draining of adjacent wetlands for conversion to agriculture. Agricultural nutrient runoff, especially P, has been often cited as the cause of the AFA blooms, and most attention has been focused on the dynamics of UKL during the summer bloom. We propose that a more significant factor may be the loss of early-season suppression of AFA because of the loss of the lake-associated wetlands, which originally constituted 42% of the lake area, and which have declined in area by 66.3% since the late 1800's. The melting of snow and ice in the spring would flush into the lake a surge of wetland plant decomposition products, most significantly organic acids and humic substances. We propose that formerly these wetland effluents caused a complex of effects on lake pH, solar UV transparency, photochemical interactions, nutrient availability, and Daphnia grazing dynamics, which would have combined to prevent the development of any AFA bloom. [source] Kinetics of Urea Decomposition in the Presence of Transition Metal Ions: Ni2+JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Bora Mavis The literature on kinetics of the urea decomposition reaction was reviewed for the 333,373 K range of temperature. Possible reactions in the pH range of 5,9 were identified. Kinetic simulations indicated significant accumulation of the cyanate intermediate in the pH-time,temperature range that was studied. The effects of Ni2+ hydrolysis and complexation with the urea decomposition products were incorporated into the simulations. The kinetic simulation of the rate of Ni2+ removal from the solutions was compared against the experimental data. The experimental results indicated an agglomerative growth mechanism for the precipitation process. Chemical analyses showed that the composition of the precipitate varies with digestion time, in agreement with the predictions of the kinetic simulation. [source] Tattoo removal by non-professionals , medical and forensic considerationsJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 7 2010S Karsai Abstract Tattoos are common phenomena in the western world and the demand for their removal has become widespread in the recent years. The introduction of quality-switched lasers has provided an effective removal method that is increasingly being exploited by tattoo studios themselves. Dermatologists, however, are frequently confronted with complications and side effects of tattoo removals that were performed by non-professionals. The objective of this study is to assess potential risks and pitfalls of laser tattoo removal when performed by medical laymen. The methods followed are systematic and evidence-based review of the literature. Four major problem areas were identified: rare but potentially severe allergic or toxic effects of decomposition products of the tattoo pigments; bodily harm caused by out-of-specification usage of the laser devices; malignant disease that is obscured within the area of a tattoo and requires meticulous dermatological diagnosis; and insufficient pre-operative consultation of patients about the risks, side effects and realistic expectations on the therapeutic outcome. We came to a conclusion that tattoo laser removal by medical laymen is unacceptable from the point of view of patient safety and the laws need to ban this practice swiftly. [source] Chlorinated poly(vinyl chloride) and plasticized chlorinated poly(vinyl chloride),thermal decomposition studiesJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2002Peter Carty The thermal decomposition of chlorinated poly(vinyl chloride) and three plasticized chlorinated poly(vinyl chloride) systems has been investigated. The routes of decomposition of these systems have been elucidated by investigating char formation and by using a combination of thermogravimetric analysis (TGA) and prolysis/gas chromatography/mass spectroscopy methods (Py/GC/MS). The effects of the charforming/smoke-suppressing iron(III) compound FeOOH in these polymer systems has also been investigated. The structure of both CPVC polymer and plasticzer determine the path of thermal decomposition and also the quantity and nature of the decomposition compunds formed. Changes in oxygen index and the formation of smoke during burning in these systems have been related to the char that is formed and also to the chemical nature of the decomposition products. [source] Determining the Vapor Pressures of Diacetone Diperoxide (DADP) and Hexamethylene Triperoxide Diamine (HMTD)PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2009Jimmie Abstract The vapor signature of diacetone diperoxide (DADP) and hexamethylene triperoxide diamine (HMTD) were examined by a gas chromatography (GC) headspace technique over the range of 15 to 55,°C. Parallel experiments were conducted to redetermine the vapor pressures of 2,4,6-trinitrotoluene (TNT) and triacetone triperoxide (TATP). The TNT and TATP vapor pressures were in agreement with the previously reported results. Vapor pressure of DADP was determined to be 17.7,Pa at 25,°C, which is approximately 2.6 times higher than TATP at the same temperature. The Clapeyron equation, relating vapor pressure and temperature, was LnP (Pa)=35.9,9845.1/T (K) for DADP. Heat of sublimation, calculated from the slope of the line for the Clapeyron equation, was 81.9,kJ mole,1. HMTD vapor pressure was not determined due to reduced thermal stability resulting in vapor phase decomposition products. [source] An Investigation on Thermal Decomposition of DNTF-CMDB PropellantsPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2007Wei Zheng Abstract The thermal decomposition of DNTF-CMDB propellants was investigated by pressure differential scanning calorimetry (PDSC) and thermogravimetry (TG). The results show that there is only one decomposition peak on DSC curves, because the decomposition peak of DNTF cannot be separated from that of the NC/NG binder. The decomposition of DNTF can be obviously accelerated by the decomposition products of the NC/NG binder. The kinetic parameters of thermal decompositions for four DNTF-CMDB propellants at 6,MPa were obtained by the Kissinger method. It is found that the reaction rate decreases with increasing content of DNTF. [source] Enzymatic digestion of liquid hot water pretreated hybrid poplarBIOTECHNOLOGY PROGRESS, Issue 2 2009Youngmi Kim Abstract Liquid hot (LHW) water pretreatment (LHW) of lignocellulosic material enhances enzymatic conversion of cellulose to glucose by solubilizing hemicellulose fraction of the biomass, while leaving the cellulose more reactive and accessible to cellulase enzymes. Within the range of pretreatment conditions tested in this study, the optimized LHW pretreatment conditions for a 15% (wt/vol) slurry of hybrid poplar were found to be 200oC, 10 min, which resulted in the highest fermentable sugar yield with minimal formation of sugar decomposition products during the pretreatment. The LHW pretreatment solubilized 62% of hemicellulose as soluble oligomers. Hot-washing of the pretreated poplar slurry increased the efficiency of hydrolysis by doubling the yield of glucose for a given enzyme dose. The 15% (wt/vol) slurry of hybrid poplar, pretreated at the optimal conditions and hot-washed, resulted in 54% glucose yield by 15 FPU cellulase per gram glucan after 120 h. The hydrolysate contained 56 g/L glucose and 12 g/L xylose. The effect of cellulase loading on the enzymatic digestibility of the pretreated poplar is also reported. Total monomeric sugar yield (glucose and xylose) reached 67% after 72 h of hydrolysis when 40 FPU cellulase per gram glucan were used. An overall mass balance of the poplar-to-ethanol process was established based on the experimentally determined composition and hydrolysis efficiencies of the liquid hot water pretreated poplar. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Kinetic Modeling of Breweryapos;s Spent Grain AutohydrolysisBIOTECHNOLOGY PROGRESS, Issue 1 2005Florbela Carvalheiro Isothermal autohydrolysis treatments of breweryapos;s spent grain were used as a method for hemicellulose solubilization and xylo-oligosaccharides production. The time course of the concentrations of residual hemicelluloses (made up of xylan and arabinan) and reaction products were determined in experiments carried out at temperatures in the range from 150 to 190 °C using liquid-to-solid ratios of 8 and 10 g/g. To model the experimental findings concerning to breweryapos;s spent grain autohydrolysis several kinetic models based on sequential pseudo-homogeneous first-order reactions were tested. Xylan and arabinan were assumed to yield oligosaccharides, monosaccharides (xylose or arabinose), furfural, and other decomposition products in consecutive reaction steps. The models proposed provide a satisfactory interpretation of the hydrolytic conversion of xylan and arabinan. An additional model merging the two proposed models for xylan and arabinan degradation assuming that furfural was formed from both pentoses was developed and the results obtained are discussed. The dependence of the calculated kinetic coefficients on temperature was established using Arrhenius-type equations. [source] Crystal Structures and Characterizations of Bis (pyrrolidinedithiocarbamato) Cu(II) and Zn(II) ComplexesCHINESE JOURNAL OF CHEMISTRY, Issue 1 2003Jian Fang-Fang Abstract The structures of [Cu (S2CN (CH2)4)2] (1) and [Zn2(S2CN-(CH2)4)4] (2) have been determined by X-ray crystallography analysis. They are all isomorphous and triclinic, space group of P1,, with Z = 1. The lattice parameters of compound 1 is: a = 0.63483(2) nm, b = 0.74972(3) nm, c=0.78390(1) mn, , = 75.912(2)°, , = 78.634(2)° and , = 86.845(2)°; compound 2: a = 0.78707(6) nm, b=0.79823(6) nm, c = 1.23246(9) nm, , = 74.813(2)°, , = 73.048(2)° and , = 88.036(2)°. The copper atom is located on a crystallographic inversion center and zinc atom lies across centers of symmetry. The Cu(II) ion has a square-planar geometry while Zn(II) has a distorted tetrahedral geometry. The thermal gravity (TG) data indicate that no structural transitions in the two compounds were abserved and the decomposition products can adsorb gas. Also they all have a high thermal stability. [source] | |||||||||||||||||||||||||||||||