Conditions Of Thermal Decomposition Research Articles

Thermal decomposition of rare earth complexes withm-aminobenzoic acid

The conditions of thermal decomposition of the m-aminobenzoates of Y, La, Ce(III), Pr, Nd and Sm-Lu, Ln(C6H4NH2COO)3.nH2O (n=4−6), have been studied.The hydrated compounds lose all molecules of crystallization water in one stage at 333–413 K. The anhydrous compounds are stable up to 570 K and are then decomposed exothermically to oxides.

Change in molecular characteristics during thermal decomposition of cellulose nitrate

The change in the molecular characteristics of cellulose nitrate as a result of the change in the conditions of thermal decomposition is studied. A decrease of MM and narrowing of the MMD in the flow system are observed, the MM is decreased in the closed system, whereas the MMD is broadened and becomes bimodal. A relation is obtained for calculating the mean number of macromolecule breaks during degradation of a polymer, which is accompanied by a change in its mass on thermal decomposition. It is established that in a flowing system the mean number of breaks ⋍4·0, i.e. the terminal macroradicals formed on thermal degradation recombine within the same cage. In the closed system the reactions occuring result in the formation of average macroradicals, the recombination of which with each other or with the terminal radicals is determined by the appearance of a high molecular MMD “tail”.

Thermal decomposition of scandium(III) o-nitrobenzoate, o-chlorobenzoate, o-methylbenzoate, o-hydroxybenzoate and o-aminobenzoate in air atmosphere

The conditions of thermal decomposition of scandium o-nitrobenzoate, o-chlorobenzoate, o-methylbenzoate, o-hydroxybenzoate and o-aminobenzoate were studied. On heating, the carboxylates decompose in two steps, only scandium anthranilate decomposes in one step. The hydrated complexes first lose water of crystallization and then are transformed to Sc2O3. The dehydration of the complexes is an endothermic process and the decomposition of anhydrous complexes is strongly exothermic. Scandium o-nitrobenzoate decomposes explosively.

Preparation and properties of yttrium, lanthanum and lanthanidep-nitrobenzoates

The conditions of the formation of rare earth elementp-nitrobenzoates were studied and their quantitative composition and solubilities in water at 298 K were determined (their solubilities are of the order of 10−3 mol dm−3). The IR and X-ray spectra for the prepared complexes and the dehydrated rare earthp-nitrobenzoates were recorded. All obtained complexes are crystalline compounds. The conditions of thermal decomposition of the complexes were also studied. It was found that on heating above 573 K the complexes decompose explosively and undergo a melting process at the same time. Therefore the thermal decomposition for complexes being investigated was carried out in the temperature range 273–573 K. From the obtained results it follows that during the dehydration process no transformation of the nitro group to nitrito occurs.

Thermal decomposition of Y, La and light lanthanide complexes of hippuric acid

The conditions of thermal decomposition of the hippurates of Y, La and the light lanthanides from Ce(III) to Gd have been studied. When heated, the Y, Ce(III), Pr and Gd complexes decomposed in two stages, those of La, Sm and Eu in three stages, and that of Nd in four stages, the oxides finally being formed. The complexes lost crystallization water to form anhydrous (Nd) or hydrated salts, and then decomposed to oxides directly (Y, Ce(III), Pr(III) and Gd) or with intermediate formation of Ln2O2CO3 (La, Nd, Sm and Eu). The temperature of oxide formation varied periodically with the ionic potential in the lanthanide series.

Thermal decomposition of yttrium, lanthanum and lanthanide complexes of square acid in air atmosphere

The conditions of thermal decomposition of the Y, La and lanthanide complexes of square acid in air atmosphere have been studied. On heating, the complexes of Y, La, Ce(III), Pr(III), Nd, Sm, Eu(III), Gd, Tb(III) and Ho decompose in two steps. First, the hydrated complexes lose crystallization water to form anhydrous salts. The complexes of Dy and Er decompose in three steps; they are dehydrated in two steps to form anhydrous salts. The complexes of Tm, Yb and Lu are dehydrated in three steps; in two steps they lose water molecules to form octahydrates, which in the third step are dehydrated during decomposition. On heating, the anhydrous complexes of Y, Ce(III), Pr(III), Eu(III), Gd, Tb(III), Dy, Ho and Er and the octahydrated salts of Tm, Yb and Lu decompose directly to the oxides Ln2O3, CeO2, Pr6O11 and Tb4O7. The anhydrous complexes of La, Nd and Sm decompose to Ln2O3 with intermediate formation of Ln2O2CO3.

Preparation and properties of yttrium, lanthanum and lanthanideo-nitrobenzoates

The conditions of the formation of yttrium, lanthanum and lanthanideo-nitrobenzoates were studied and their quantitative composition and solubilities in water at 298 K were determined (their solubilities are of the order of 10−2 mol dm−3). The IR and X-ray spectra for the obtained complexes and the dehydrated rare earth elemento-nitrobenzoates were recorded; all prepared complexes are crystalline compounds. The conditions of thermal decomposition of the complexes were also studied. It was found that on heating above 523 K the complexes decompose explosively and undergo a melting process at the same time. Therefore the thermal decomposition for complexes being studied was carried out in the temperature range 273–523 K. From the results it appears that during the dehydration process or with the increase of temperature no transformation of the nitro group to nitrito occurs.

Thermal decomposition of rare earth complexes with o-aminobenzoic acid

The conditions of thermal decomposition of La, Ce(III), Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu anthranilates have been studied. The anhydrous La, Ce(III), Pr(III), Nd and Sm anthranilates decompose in one step directly to the oxides Ln2O3, CeO2 or Pr6O11. The monoand dihydrated anthranilates of the remaining rare earths first lose crystallization water when heated, and then decompose exothermally to the oxides Ln2O3 or Tb4O7.

Problems encountered in solid sampling-trace analysis of various geological samples by ETA-ZAAS

The determination of trace elements by solid sampling in geological samples presents many difficulties because the matrix is complex. We studied atomization and thermal decomposition conditions for solid sampling on soil, rock and sediment samples, using inverse Zeeman background correction. Each sample was ‘diluted’ with graphite powder. Both the sensitivity and accuracy were improved with the graphite dilutions.

Studies on thermal decomposition of 3-chlorobenzoates of rare earth elements in air atmosphere

The conditions of thermal decomposition of the 3-chlorobenzoates of Y, La and the lanthanides from Ce(III) to Lu have been studied. The complexes of La, Pr(III), Sm, Eu, Gd, Tb(III) and Dy were prepared as heptahydrates, those of Ce(III) and Y as pentahydrates, that of Nd as the tetrahydrate, that of Ho as the dihydrate and those of Er, Tm, Yb and Lu as anhydrous salts. On heating, these complexes decompose in three or two stages. They first lose some water molecules and then decompose to oxides through the intermediate formation of LnOCl. Cerium(III) 3-chlorobenzoate loses its crystallization water in two stages and yields the anhydrous salt, which is then transformed directly into CeO2. All these complexes melt before decomposition in the temperature range 441–513 K.

A literature review of the chemical nature and toxicity of the decomposition products of polyethylenes

AbstractThe literature on polyethylenes has been reviewed with an emphasis on the identification of gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to publications in English through 1984. The analytical chemical studies of the thermal decomposition products generated under vacuum, inert and oxidative experimental conditions are described. In oxidative atmosphere, which most closely simulate real fire conditions, carbon monoxide (CO) was found to be the predominant toxicant. Acrolein was another toxicant often noted in these reviewed studies. More acrolein was generated under non‐flaming than under flaming conditions. Results from seven different test procedures were considered in assessing the acute inhalation toxicity of combustion products from various polyethylene formulations. The combustion products generated from the polyethylenes studied in the non‐flaming mode appeared to be slightly more toxic than those produced in the flaming mode. In the non‐flaming mode the LC50 values ranged from 5 to 75 mg l−1. In the flaming mode the LC50 values ranged from 31 to 51 mg l−1. The toxicity of the degradation products of polyethylenes appears to be similar to that found for other common materials designed for the same end uses.

Thermal decomposition of 8-hydroxyquinoline complexes with aluminium, cobalt, manganese and nickel

The conditions of thermal decomposition of aluminium(III), cobalt(II), manganese(II) and nickel(II) 8-hydroxyquinoline complexes have been studied by TG-DSC analysis. The thermal decomposition of these complexes has two stages: dehydration and loss of 8-hydroxyquinoline. The final solid product is an oxide.

A review of the literature on the gaseous products and toxicity generated from the pyrolysis and combustion of rigid polyurethane foams

AbstractThe literature on rigid polyurethane foam has been reviewed with an emphasis on the gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to publications in English through 1984. Carbon monoxide (CO) and hydrogen cyanide (HCN) were the predominant toxicants found among more than a hundred other gaseous products. The generation of CO and HCN was found to increase with increasing combustion products from various rigid polyurethane foams. Lethality, incapacitation, physiological and biochemical parameters were employ as biological end points. In general, the combustion products generated from rigid polyurethane foam in the flaming mode appear from to be more toxic than those produced in the non‐flaming mode. The LC50 values for 30‐min exposures ranged from 10 to 17 mg l−1 in the flaming mode and were greater then 34 mg l−1 in the non‐flaming mode. With the exception of one case, in which a reactive type phosphorus containing fire retardant was used, the addition of fire retardants to rigid polyurethane foams does not appear to generate unusual toxic combustion products.

Thermal decompositions of scandium(III) m-nitrobenzoate, m-chlorobenzoate, m-hydroxybenzoate and m-aminobenzoate in air atmosphere

The conditions of thermal decomposition of scandium(III) m-nitrobenzoate, m-chlorobenzoate, m-hydroxybenzoate and m-aminobenzoate were studied. On heating, most of these carboxylates decompose in two steps; only scandium(III) 3-aminobenzoate decomposes in one step. The hydrated complexes first lose crystallization water and are then transformed to Sc2O3. The hydration of the complexes is accompanied by an endothermic effect, and the decomposition of the anhydrous complexes by a strong exothermic effect. Scandium(III) 3-nitrobenzoate decomposes explosively.

Thermal decomposition of thorium(IV) benzenedicarboxylates in air atmosphere

The conditions of thermal decomposition of Th(IV) benzenedicarboxylates have been studied. On heating, thorium(IV) phthalate and isophthalate are dehydrated and the anhydrous complexes decompose to ThO2 with intermediate formation of a mixture of ThOCO3 and carbon. Th(IV) terephthalate obtained at room temperature loses crystal water and then decomposes directly to ThO2, while the complex isolated from a hot solution on heating is first dehydrated, and the anhydrous complex is decarboxylated and then decomposed to ThO2 with the intermediate formation of ThOCO3. The activation energies of dehydration have been calculated for the Th(IV) benzenedicarboxylates.

Thermal decompositions of Y, La and lanthanide 3-hydroxybenzoates in air and nitrogen atmospheres

The conditions of thermal decomposition of heavy lathanide complexes with 3-hydroxybenzoic acid in air and nitrogen atmospheres have been studied. On heating, the complexes of Gd, Dy, Ho, Yb and Lu decompose in three stages. First, the hydrated complexes lose crystallization water and the anhydrous salts heated in air are then transformed to Ln2O3, or in a nitrogen atmosphere to Ln2O3 and C. Complexes of Tb(III), Ho and Er are dehydrated in two stages during heating, and the anhydrous complexes are converted in air to Ln2O3 and Tb4O7, and in a nitrogen atmosphere to a mixture of oxides and C. The carbon content in the decomposition product ranges between 9.7% for Gd and 19.6% for Ho.

Thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere

The conditions of thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere at heating rates of 10 and 5 deg·min−1 were studied. At 10 deg · min−1, the hemimellitate and trimesinate of copper(II) lose crystallization water and then decompose directly to CuO, whereas at 5 deg·min−1 they decompose to CuO through Cu2O. The trimellitate of copper(II) heated at various rates decomposes in the same way: it loses 1 water molecule and then decomposes directly to CuO.

Thermal decompositions of Y, La and light lanthanide thiodiglycolates

The conditions of thermal decomposition of the thiodiglycolates of Y, La and light lanthanides from Ce to Gd have been studied. On heating, these complexes decompose in various ways. Hydrated thiodiglycolates of La,Ce(III), Pr(III) and Gd lose crystallization water in one step, while those of Y, Nd, Sm and Eu(III) do so in two steps. The anhydrous complexes subsequently decompose in several steps to the oxysulfates Ln2O3−x((SO4)x.

Thermal decomposition of rare earth pyromucates in air atmosphere

The conditions of thermal decomposition of Y, La and lanthanide (from Ce(III) to Lu) pyromucates have been studied. On heating, these complexes decompose in various ways: La, Pr, Nd and Sm pyromucates in four stages, Ce, Eu, Gd, Dy, Ho and Er pyromucates in three stages, and Tm, Yb, Lu and Y pyromucates in two stages, the oxides finally being formed. The hydrated complexes (from La to Er) lose crystallization water to form anhydrous salts. The anhydrous complexes of La, Pr, Nd and Sm decompose to oxides through the intermediate formation of unstable oxypyromucates and Ln2O2CO3, whereas the anhydrous complexes of Ce(III), Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu decompose to the oxides through the intermediate formation of oxypyromucates. The temperatures of dehydration and oxide formation change periodically with increasing atomic number in the lanthanide series.

Analysis of autoxidized fats by gas chromatography‐mass spectrometry. IX. Homolytic vs. Heterolytic cleavage of primary and secondary oxidation products

AbstractTo elucidate the genesis of volatile lipid oxidation products, thermal homolytic and acid heterolytic decomposition processes were compared. Secondary oxidation products were decomposed thermally (200 C), and the volatiles formed were identified by capillary gas chromatography‐mass spectrometry (GC‐MS). Oxidation products also were decomposed in the presence of HCl‐methanol, and the resulting dimethyl acetals were identified by GC‐MS. The volatile thermal decomposition products were those expected by homolytic β‐scission on both sides of the hydroperoxide group. No dialdehydes were identified under our thermal decomposition conditions. In contrast, the acetals formed by acid decomposition were those expected by selective heterolytic scission between the hydroperoxide group and the allylic double bond. Dialdehydes identified from acid decomposition of cyclic peroxides and dihydroperoxides included malonaldehyde and 2,4‐hexadienedial.