TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Programmed Temperature Vaporization Injection (PTV) in the Analysis by Gas Chromatography-Mass Spectrometry (GC-MS) of the Constituents of Landfill Gas

Abstract

Trace volatile compounds emitted from both domestic and industrial landfills have been identified by programmed temperature vaporization injection (PTV) coupled to gas chromatography with detection by ion-trap mass spectrometry (GC-ITD/MS). The PTV injection system has been developed using a combination of two six-port valves to achieve problems of interference in GC-MS while loading sample. A large volume of landfill gas was re-concentrated onto a sorbent trap, then rapidly liberated into the GC-ITD/MS system by programmed thermal desorption. Using this method, trace volatile compounds in gases from both domestic and industrial landfills such as aromatic hydrocarbons, terpenes, chlorinated hydrocarbons, and sulfur compounds can be identified and quantified.     

Thermal degradation studies on PMMA–HET acid based oligoesters blends

Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO₂, H₂O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented.     

Determination of chlorinated hydrocarbons in single and multi component test gases

Summary For comparing the efficiency of active and diffusive sampling methods two diffusive samplers with different properties were used to determine chlorinated hydrocarbons (CH₂Cl₂, CHCl₃, CCl₄) in single and multi component test gas mixtures. One of the chosen diffusive samplers can also be used for active sampling.In general, good correlations of all tested methods could be observed in the direct comparison of active and diffusive sampling and in the determination of the efficiencies.During the application of active and diffusive sampling methods in multi component test gases of the analytes possible interferences could not be ascertained.     

Thermal and thermo-oxidative degradation of poly(hydroxy ether of bisphenol-A) studied by TGA/FTIR and TGA/MS

The nature and the extent of degradation of poly(hydroxy ether of bisphenol-A) phenoxy resin were analysed by thermogravimetry (TGA/DTGA) under nitrogen and air atmosphere. Decomposition kinetics were elucidated according to Flynn-Wall-Ozawa, Friedman and Kissinger methods. The evolved gases during degradation were inspected by a thermogravimetry analyser coupled with Fourier Transform Infrared Spectrometer (TGA/FTIR) and also with a TGA coupled to a Mass Spectrometer (TGA/MS). Mass spectra showed that chemical species evolved in phenoxy decomposition in air were very similar to those assigned from degradation in nitrogen (water, methane, CO, CO₂, phenol, acetone, etc.). However, these species appear in different amount and at different temperatures in both atmospheres. FTIR analysis of the evolved products showed that water and methane were the beginning decomposition products, indicating that decomposition is initiated by dehydration and cleavage of C-CH₃ bond in the bisphenol-A unit of phenoxy resin. After this initial stage, random chain scission is the main degradation pathway. Nevertheless, in air atmosphere, previously the complete decomposition of the phenoxy obtaining fundamentally CO₂, and water, the formation of an insulated surface layer of crosslinked structures has been proposed.     

Reactions of chloroethenes with atomic chlorine in air at atmospheric pressure

Relative rate method at the temperature of 298 K and pressure of 1013 hPa and GC-MS detection were used for the study of kinetics of the reactions of Cl atoms with H₂C=CCl₂, cis-ClHC=CHCl, trans-ClHC=CHCl, ClHC=CCl₂, and Cl₂C=CCl₂. The reaction products were identified by FTIR spectroscopy. A mechanism for the atmospheric degradation of chloro-ethenes has been suggested.     

The effect of flame coal oxidation on the solid and soluble products of its extraction

Solid and soluble products of THF and CH₂Cl₂ extraction of flame coal oxidised by four different oxidising agents (peroxyacetic acid (PAA), 5% HNO₃, O₂/Na₂CO₃, air/125 °C) were studied by elemental analysis and FTIR. The extraction yield with THF was much higher than that with CH₂Cl₂ for all samples. The greatest changes in elemental composition were in the extracts from coal oxidised by nitric acid. The sulphur content was lowest in extracts from coal oxidised with 5% HNO₃ and PAA. FTIR confirmed that coal treatment with nitric acid incorporates nitrogen into the coal structure.     

Application of coupled TG-FTIR system in studies of thermal stability of manganese(II) complexes with amino acids.

Detailed thermal analysis of manganese(II) complexes with a-amino acids were carried out. The thermal degradation is multi-stage. Dehydration of complexes is the first mass loss step. Anhydrous compounds are unstable and decompose to Mn₃O₄ in air or to MnO in inert atmosphere. The intermediate solid products were identified by TG method and TG/FTIR combined technique. Among others solid residues, the presence of MnSO₄, MnBr₂ and Mn(CH₃COO)Cl was found. In the gaseous products of decomposition of organic ligand H₂O, NH₃, CO₂, CO, aromatic and non-aromatic hydrocarbons and very probably cyanoacetic acid and dimethyl sulfide occurred. Inorganic ions, i.e. Cl^-, Br^-or So₄ ^2-remain in the solid products of decomposition or are lost as HCl, HBr or SO₂. This revised version was published online in July 2006 with corrections to the Cover Date.     

TG/DSC/FTIR characterization of linear geranyl diesters

The synthesis, thermal behavior, and characterization of the decomposition products of linear geranyl diesters: digeranyl succinate, digeranyl glutarate, digeranyl adipinate, and digeranyl sebacinate were presented. The linear geranyl diesters were prepared in direct esterification process of a molar stoichiometric ratio of geraniol and suitable acidic reagent in solvent-free medium at 130 °C using butylstannoic acid as a catalyst. Their structure was confirmed based on FTIR, ¹H- and ¹³C-NMR spectra. It was proved that the use of tin catalyst allowed decreasing the reaction time and increasing the final conversion of substrates when compared to non-catalyzed process. It considerably simplifies the processing by reduction of the preparation cost and thus this new method of synthesis of aroma diesters may be attractive for practical applications. The thermal behavior of prepared compounds was studied by TG/DSC/FTIR coupled method. TG analysis showed that diesters are thermally stable up to temperatures above 200 °C. The DTG curves confirmed that these decomposition run as a single-stage process. The T _max1 were in the range of 294.5–313.8 °C depending on the aliphatic chain length (–CH₂–)_n in the structure of aroma diesters, which was in accordance with DSC data. The analysis of the gases evolved during heating of diesters in inert atmosphere indicated on the asymmetrical disrupt of their bonds. The cleavage of ester bond and O-geranyl bond was expected. It resulted in production of the mixture of derivatives of geraniol (acyclic and alicyclic monoterpene hydrocarbons) like myrcene, ocimene, or limonene as main decomposition products. In addition, the formation of anhydride, lactone, or ketone functionalities among the degradation products clearly confirmed the proposed degradation path of studied diesters.     

Synthesis and characterization of polyesteramides derived from an oxazoline-functional alcohol and dicarboxylic acid anhydrides

Novel polyesteramides were synthesized by copolymerization in bulk of 5-(4,5-dihydro-1,3-oxazol-2-yl)-1-pentanol and various cyclic dicarboxylic acid anhydrides at temperatures varying between 120 and 200°C. The polymers resulting from polycondensation were characterized by means of ¹H–NMR, FTIR, MALDI–TOF–MS, SEC, and DSC. The glass transition temperatures, T_g, of the copolymers were varied between −28 and +31°C as a function of the anhydride type. Molecular weights, M_w, were dependent on reaction temperature, reaction time, and anhydride type. Spectroscopic investigation of reaction products and esteramide model compounds provided evidence for imide by-product formation, which accounts for the low degree of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3367–3376, 1999     

Evolved gas analysis of coal-derived pyrite/marcasite

The products evolved during the thermal decomposition of the coal-derived pyrite/marcasite were studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR–MS) technique. The main gases and volatile products released during the thermal decomposition of the coal-derived pyrite/marcasite are water (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved product H₂O is mainly released at below 300 °C; (2) under the temperature of 450–650 °C, the main evolved products are SO₂ and small amount of CO₂. It is worth mentioning that SO₃ was not observed as a product as no peak was observed in the m/z = 80 curve. The chemical substance SO₂ is present as the main gaseous product in the thermal decomposition for the sample. The coal-derived pyrite/marcasite is different from mineral pyrite in thermal decomposition temperature. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanations have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials.     

Liquid chromatography–high-resolution mass spectrometry for identifying aqueous chlordecone hydrate dechlorinated transformation products formed by reaction with zero-valent iron

Chlordecone (CLD) is a persistent toxic chlorinated pesticide which contaminates different ecosystems in French West Indies. A soil remediation process including zero-valent iron (ZVI) has produced promising results but failed to completely degrade CLD, and the analytical procedures used yielded little information on the transformation products. To fill these gaps, dechlorination of aqueous CLD by micrometric particles of ZVI has been investigated. Aliquots of water with 25% (v/v) of acetone spiked with 100 ppm CLD were taken at different times during a 30-day ZVI treatment and directly analysed by ultra-high-performance liquid chromatography in negative electrospray ionisation mode. CLD has been totally transformed after 14 days into 14 dechlorinated degradation products, including 9 isomeric compounds. The maximum chloride concentrations appearing in the medium represent 44% of that which would result from total dechlorination of CLD. The CLD transformation products identified by accurate mass measurements on an ultra-high-resolution Q-TOF mass spectrometer (Q-TOF-MS) were C₁₀H₃Cl₉O₂, C₁₀H₄Cl₈O₂, C₁₀H₅Cl₇O₂, C₁₀H₆Cl₆O₂ and C₁₀H₇Cl₅O₂. The results show the interest of LC-Q-TOF-MS for identifying transformation products of organic contaminants, and the effectiveness of micrometric ZVI particles to totally transform CLD into less chlorinated products.     

Halocarbons in Aqueous matrices from the Rennick Glacier and the Ross Sea (Antarctica)

Aqueous matrices from Antarctica were analysed for three volatile chlorinated hydrocarbons (VCHCs): tetrachloromethane (CCl₄), trichloroethylene (C₂HCl₃) and tetrachloroethylene (C₂Cl₄). The matrices analysed were snow from Rennick Nèvè and Rennick Glacier sampled during the Italian Expeditions of 1995/96 and 1996/97, respectively, and seawater, pack ice, sea-microlayer, subsuperficial water and freshwater, collected during the Italian Expedition of 1997/98. Extractions from the aqueous matrices were carried out in Antarctica (the laboratories of the Italian Base, Terra Nova Bay). Because of the critical space–time conditions in these laboratories, an extraction procedure was developed, suitable for large volumes of water (10?L), in order to combine the extraction of other classes of organic compounds (polychlorinated biphenyls, polycyclic aromatic hydrocarbons and chlorinated pesticides) with those of our direct interest. The VCHC organic extracts were analysed in Italy by GC-ECD and GC-MS. The analyses confirmed the presence of the three halocarbons in Antarctica in quantities ranging from units to some dozens of nanograms per kilogram. The results were evaluated with respect to the local distribution of these compounds and their diffusion on a global scale.     

Synthesis and structures of C<Subscript>60</Subscript> fullerene chlorides

Systematic study of chlorination of fullerene C₆₀ with inorganic chlorides SbCl₅, VCl₄, MoCl₅, and KICl₄ was carried out. Higher chlorofullerenes, viz., T _h -C₆₀Cl₂₄, C₆₀Cl₂₈, C ₂-C₆₀Cl₃₀, and D _3d -C₆₀Cl₃₀, can be prepared depending on the temperature and time of chlorination. The molecular and crystal structures of C₆₀Cl₂₄⋅VOCl₃, C₆₀Cl₃₀⋅2CS₂, and C₆₀Cl₃₀O_1.22 were determined by single-crystal X-ray diffraction. Fullerenes C₆₀Cl₂₈ and C ₂-C₆₀Cl₃₀ were shown to be only kinetically stable, whereas D _3d -C₆₀Cl₃₀ is a thermodynamically stable product. Transformations of less chlorinated fullerenes into more chlorinated products are accompanied by substantial changes in the addition patterns. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1608–1618, July, 2005.     

Thermal degradation and evolved gas analysis of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) during pyrolysis and combustion

The thermal degradation of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) was investigated by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy and mass spectroscopy (TG–FTIR–MS). Thermogravimetric analysis revealed that the thermal degradation process can be subdivided into three stages: sample drying (<200 °C), main decomposition (200–500 °C), and further cracking (>500 °C) of the polymer. The compound reached almost 800 °C during pyrolysis and combustion. The activation energy at the second step during combustion was slightly higher than that of pyrolysis emissions of carbon dioxide, aliphatic hydrocarbons, carbon monoxide, and hydrogen cyanide, and other gases during combustion and pyrolysis were detected by FTIR and MS spectra. It was observed that the intensities of CO₂, CO, HCN, and H₂O were very high when compared with their intensities during pyrolysis, and this was attributed to the oxidation of the decomposition product.     

Mechanism of phthalic anhydride formation in the oxidation of n-pentane on a vanadium-phosphorus oxide catalyst

The reaction paths of product formation in the partial oxidation of n-pentane on vanadium-phosphorus oxide (VPO) and VPO-Bi catalysts are considered. The condensed products of n-pentane oxidation were analyzed by chromatography-mass spectrometry, and the presence of C₄ rather than C₅ unsaturated hydrocarbons was detected. It was found that the concentration of phthalic anhydride in the products increased upon the addition of C₄ olefins and butadiene to the n-pentane-air reaction mixture. With the use of a system with two in-series reactors, it was found that the addition of butadiene to a flow of n-butane oxidation products (maleic anhydride, CO, and CO₂) resulted in the formation of phthalic anhydride. The oxidation of 1-butanol was studied, and butene and butadiene were found to be the primary products of reaction; at a higher temperature, maleic anhydride and then phthalic anhydride were formed. The experimental results supported the reaction scheme according to which the activation of n-pentane occurred with the elimination of a methyl group and the formation of C₄ unsaturated hydrocarbons. The oxidation of these latter led to the formation of maleic anhydride. The Diels-Alder reaction between maleic anhydride and C₄ unsaturated hydrocarbons is the main path of phthalic anhydride formation.     

Physicochemical studies on solid products of reactions of chromyl chloride and chromyl acetate with alkylaromatics. Part I. Infrared spectra and magnetic measurements

Summary Reaction of chromyl chloride, CrO₂Cl₂, with various alkylaromatics leads to solid products of composition 2CrO₂Cl₂ · HR (where HR is an alkylaromatic); however, they are not the simple adducts as the oxidation state of chromium appears to be reduced from VI to IV. The products of chromyl acetate reactions with the same hydrocarbons are monochromo(IV)- and dichromo(IV)-hydroxyacetates depending on the method of preparation. Infrared spectra and magnetic measurements were interpreted as showing that none of these compounds are the adducts of chromyl chloride or chromyl acetate but that all contain chromium(IV).     

The effect of polymer side chains on vapor sorption in polyacrylate and polymethacrylate solutions

The segment fraction Ψ₁ activity coefficients, a₁/Ψ₁, of solvents have been determined by the piezoelectric sorption method for 0.1 ≤ Ψ₁ ≤ 0.5 in binary solutions of chlorinated methanes [carbon tetrachloride (CCl₄), chloroform (CHCl₃), and dichloromethane (CH₂Cl₂)] with aromatic hydrocarbons (benzene and toluene) in poly(methyl methacrylate), poly(methyl acrylate), poly(ethyl methacrylate), and poly(n-butyl acrylate) at 23.5°C. The present results for toluene in PMMA agree with previously published values obtained by gas-liquid chromatography. For CCl₄ and the aromatic hydrocarbons, the polymer–solvent interaction parameter χ is positive and constant, while for the polar solvents (CHCl₃ and CH₂Cl₂), χ is negative and increases with increasing Ψ₁. The effect of the polymer side chains on vapor sorption in nonpolar and polar solvent systems is discussed in terms of the χ parameter.     

Investigation of radiochemical conversions in extraction systems based on tributyl phosphate

The use of halogenated organic compounds under the effect of ionizing radiation requires a comprehensive knowledge of their radiation stability. There is little experimental evidence on the radiolysis of fluorine-containing organic compounds in the literature, while a theoretical generalization enabling one to predict the main radiolysis pathways is completely lacking. This paper is concerned with the identification of stable radiolysis products of trichloromethyl-1,1,2-trifluoro-2,2-dichloroethyl ether (C₃F₃Cl₅ O), γ-irradiated separately and the extraction system based on tributyl phosphate. Practically all the C₃F₃Cl₅O radiolysis products were identified with the aid of gas-liquid chromatography, GC-MS, IR, UV and NMR spectroscopy and elemental analysis. Upon C₃F₃Cl₅O radiolysis, the formation of CCl₄, Cl₂, COCl₂, C₂ Cl₆, freons of various composition and long-chained ethers like CFCl₂−CF₂−O−CCl₂−CCl₃ takes place. The identification of radiolysis products allows to draw well-founded conclusions on the mechanism of C₃F₃Cl₅O radiolysis, representing a wide class of chlorine- and fluorine-containing organic compounds.     

An FTIR study of the Cl atom-initiated oxidation of CH2Cl2 and CH3Cl

The Cl atom-initiated oxidation of CH₂Cl₂ and CH₃Cl was studied using the FTIR method in the photolysis of mixtures typically containing Cl₂ and the chlorinated methanes at 1 torr each in 700 torr air. The results obtained from product analysis were in general agreement with those reported by Sanhueza and Heicklen. The relative rate constant for the Cl atom reactions of CH₂Cl₂ and CH₃Cl was determined to be k(Cl +CH₃Cl)/k(Cl + CH₂Cl₂) = 1.31 ± 0.14 (2σ) at 298 ± 2 K.