铁催化剂在碳—氧反应中的热重研究

采用动态TG－DTG，研究了铁催化剂的制备方法、前驱化合物的 种类及 热处理对其在碳－氧反应中催化活性的影响。观察到在干混法制备催化剂时，所用铁盐分解温度越低活性越高。此外还发现，热处理可明显提高由分解温度高的含氧铁盐制备的 催化剂的活性，但对于不含氧铁盐和分解温度低的含氧铁盐无影响。     

Sulfonation of arylamines: Part 12. Kinetics of thermal decomposition of dimethylanilinium sulfates

Three dimethylanilinium sulfates (DMAS) have been prepared and characterised by elemental and spectral studies. Thermal decomposition of these salts has been studied by TG and simultaneous TG-DTG technique and kinetic parameters were evaluated from both dynamic and isothermal TG data using mechanism based kinetic equations. The thermal decomposition pathways have also been suggested and it has been found that DMAS salts give dimethyl aminobenzenesulfonic acids (DMABSA) via solid state reaction. The primary step in the thermal decomposition involves proton transfer followed by sulfonation.This revised version was published online in November 2005 with corrections to the Cover Date.     

Eliminations competitives lors de la decomposition basique de sels de N-alcoxypyridinium—I: Competition entre intermediaires ylure ou anhydrobase et ions hydroxydes dans l'arrachement des protons en α ou β dans la chaine alcoxyle2

A novel mode of base-induced decomposition of N-alkoxypyridimum salts carrying a β-hydrogen in their alkoxy chain is described. In these compounds the N-oxide moiety can act as a leaving group in an elimination reaction yielding an ethylenic derivative, in competition with the classical decomposition to aldehyde and pyridine. This latter is predominant in salts 9 and 10 bearing a methyl group in 2 or 6 positions of the pyridine nucleus, whereas the new mode of decomposition becomes almost exclusive for salts 7 and 8 unsubstituted in these positions. Deuteration studies show that proton abstraction does not occur by transfer to an ylide during the decomposition by hydroxide ion, proton abstraction results from direct attack by hydroxide ion except for the α-proton of salts bearing at least one methyl group in 2 or 6 positions where it occurs by a transfer (essentially intramolecular) to an intermediary anhydrobase.     

4’-甲氧基-4-重氮二苯胺金属复盐稳定性的研究

本文研究了4′-甲氧基-4-重氮二苯胺(VB)金属复盐的稳定性,提出红外密度比值(D),热分解温度和光、热分解指数作为稳定性的量度。本文认为,4′-甲氧基-4-重氮二苯胺盐的分解为异裂反应。感光性能试验指出,感光胶片保存性参数与重氮盐稳定性参数之间有良好的相关性。     

Preparation, spectral and thermal studies of pyrazinecarboxylic acids and their hydrazinium salts

Some new hydrazinium 2-pyrazinecarboxylate and 2,3-pyrazinedi-carboxylate salts of the formulae N₂H₅pc, N₂H₅pc.H₂O (Hpc = 2-pyrazinecarboxylic acid), N₂H₅Hpdc, (N₂H₅)₂pdc.H₂O and N₂H₅(Hpdc).H₂pdc (H₂pdc = 2,3-pyrazinedi-carboxylic acid) have been prepared by neutralization of aqueous hydrazine hydrate with the respective acids in appropriate molar ratios. The free acids and their hydrazinium salts have been characterized by analytical, IR spectroscopic and thermal studies. IR spectra of all the salts show N-N stretching frequencies of the N₂H₅ ⁺ ion in the region 975–960 cm^-1. The thermoanalytical behaviour of the free acids and their salts has been investigated by simultaneous TG and DTA. While pyrazinecarboxylic acid shows single-step endothermic (229°C) complete decomposition, pyrazindi-carboxylic acid shows exothermic decarboxylation followed by identical endothermic decomposition as that of the former. Similarly, salts of the monocarboxylic acid show endothermic effects during pyrolysis, whereas salts of the dicarboxylic acid show endothermic followed by exothermic decomposition. The acids and their salts both undergo complete decomposition to gaseous products.     

Thermal Decomposition of Ni(II) and Fe(III) Nitrates and their Mixture

The thermal decompositions of nickel(II) nitrate hexahydrate and iron(III) nitrate nonahydrate were followed. It was found that the final decomposition products were NiO at 623 K and Fe2O3 at 523 K, respectively. The two salts exhibited only endothermic peaks and a loss in mass until constant mass was attained. The decomposition reactions and the compounds corresponding to each reaction were established. A heating rate of 1 K min-1 revealed several intermediates; higher heating rates shifted the peaks to higher temperatures. The use of an air flow during decomposition shifted the reactions to lower temperatures. The DTA for the mixed salts was found to be an overlap and the TG a summation of the results for the two individual salts. At 773 K, the decomposition products were composed of three phases: NiO, Fe2O3 and NiFe2O4. When these products were heated to 1773 K, only NiFe2O4 was identified by X-ray diffraction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Homolytic aromatic acetylation. A new substitution reaction of arenediazonium salts

The homolytic decomposition of arenediazonim salts induced by thermal, photochemical or redox (iron(II) salts or copper) sources in the presence of biacetyl gives substituted acetophenones with complete positional selectivity by a free-radical chain or a redox process.     

Treatment of off-gas evolved from thermal decomposition of sludge waste

Korea Atomic Energy Research Institute (KAERI) started a decommissioning program of a uranium conversion plant. The treatment of the sludge waste, which was generated during the operation of the plant, is one of the most important tasks in the decommissioning program of the plant. The major compounds of sludge waste are nitrate salts and uranium. The sludge waste is denitrated by thermal decomposition. The treatment of off-gas evolved from the thermal decomposition of nitrate salts in the sludge waste is investigated. The nitrate salts in the sludge were decomposed in two steps: the first decomposition is due to the ammonium nitrate, and the second is due to the sodium and calcium nitrate and calcium carbonate. The components of off-gas from the decomposition of ammonium nitrate at low temperature are NH₃, N₂O, NO₂, and NO. In addition, the components from the decomposition of sodium and calcium nitrate at high temperature are NO₂ and NO. Off-gas from the thermal decomposition is treated by the catalytic oxidation of ammonia and selective catalytic reduction (SCR). Ammonia is converted into nitrogen oxides through the oxidation catalyst and all nitrogen oxides are removed by SCR treatment besides nitrous oxide, which is greenhouse gas. An additional process is needed to remove nitrous oxide, and the feeding rate of ammonia in SCR should be controlled properly for evolved nitrogen oxides.     

The decomposition of aryl diazonium borofluorides in nitrobenzene and ethyl benzoate in the presence of the free metal,copper powder

Summary In the presence of copper powder the decomposition of aryl diazonium borofluorides in nitrobenzene and ethyl benzoate gives products of homolytic splitting of the diazonium salts. The synthesis of metalloorganic compounds from diazonium salts in the presence of metals occurs by a homolytic mechanism.     

Etude par analyse thermique des sels de calcium de quelques acides alcanesulfoniques

Calcium salts of some alkanesulphonic acids have been prepared. Most of them are new. Their dehydration and the decomposition of anhydrous salts have been studied by thermogravimetric analysis (TG) and by thermal differential analysis (DTA) under ordinary pressure. In an inert atmosphere the sulphides formed indicate that carbon-sulphur and oxygen-sulphur bonds have been broken. The mechanism of decomposition of the calcium alkanesulphonates seems to be more complicated than that of the corresponding carboxylates.     

Thermolysis of hydrogen sulphate,nitrate and perchlorate salts of diphenylamine. Part LXVIII

Hydrogen sulphate, nitrate and perchlorate salts of diphenylamine have been prepared and characterized by elemental, spectral and gravimetric analyses. Thermal decomposition of these salts has been evaluated by TG (static air) and DSC (inert atmosphere). The proton transfer reaction plays a major role during thermolysis of these salts. The diphenylammonium hydrogen sulphate under thermal and microwave irradiation forms 4-(phenylamino) benzenesulphonic acid by sulphonation process, whereas nitrate and perchlorate salts do not form corresponding nitro and perchloro derivatives, rather they ignite and explode, respectively, to form gaseous products along with a residual carbon .     

Vaporization and thermal decomposition of transition metal salts in flameless atomic absorption spectrometry with a carbon tube atomizer

Vaporization and thermal decomposition of Cr, Mn, Fe, Co, Ni and Cu salts were investigated by measuring the absorption spectra observed when aqueous solutions of these salts were heated in the carbon tube atomizer. Gaseous metal halides are vaporized in the atomizer at temperatures above 300–500° C. SO₂ and NO are produced by thermal decomposition of metal sulfates and nitrates, respectively. The vaporization of metal halides is also confirmed by the spectra for solutions of metals in hydrochloric acid and for mixtures of metal nitrates and ammonium halides.     

Thermoanalytical properties of analytical-grade reagents-IVA: sodium salts

Thirteen sodium salts have been investigated derivatographically. The weight change, rate of weight change and enthalpy change of the salts have been measured as a function of temperature. The temperatures at which the salts may be dried without decomposition are given. Some of the curves are explained in terms of the effects of heat and gaseous products on the structure of the salts.     

Structural characterization of mono- and bisphosphonium salts by fast atom bombardment mass spectrometry and tandem mass spectrometry

Positive-ion fast atom bombardment (FAB) mass spectra are reported for a representative series of mono- and bisphosphonium halides derived from triphenylphosphine. The mass spectra of the monoalkyltriphenylphosphonium salts typically contain abundant intact cations that can be used to establish the cationic relative molecular mass and diagnostic fragment ions that allow the characterization of structural subgroups. Depending on the functional group substitution on the alkyl group, additional fragment ions are observed which are formed by loss of small neutral molecules from the intact cation and that can be used for the differentiation of isomeric phosphonium salts. Molecular dication are typically observed in the FAB mass spectra of the bisphosphonium salts when they are analysed in 3-nitrobenzyl alcohol. In addition, production of singly charged ions by clustering with a counter ion, decomposition involving removal of one of the charge centres and one-electron reduction are generally observed. Structurally diagnostic fragments are also obtained. The fragmentation pathways of the ions derived from the phosphonium salts were elucidated by precursor ion and product ion tandem mass spectrometric experiments. For the phosphonium salts containing a long-chain hydrocarbon alkyl group, high-energy collision-induced decomposition of the intact cation is needed to obtain unambiguous structural information.     

Pyrolysis—gas chromatography of quaternary ammonium salts in aqueous solution

The pyrolysis of a range of simple quaternary ammonium salts in aqueous solution has been studied by gas chromatographic procedures. The results indicate that the structure of the cation governs the thermal stability and breakdown pattern of the salts, the nature of the anion having no apparent effect on the process. The mechanism of the decomposition is discussed as is the potential of aqueous pyrolysis—gas chromatography for analytical studies of quaternary ammonium salts in general.     

Gas chromatographic study of the pyrolysis of potassium salts of xanthic acids

A pyrolysis apparatus was developed for studies over a wide temperature range. Potassium salts of xanthic acids were pyrolysed between 200 degrees and 1225 degrees . The decomposition temperatures were compared with the DTA curves of the corresponding salts.     

Preparation, crystal structure, and thermolysis of phenylenediammonium diperchlorate salts

Three salts of phenylenediammonium diperchlorate have been prepared and characterized by X-ray crystallography. Their thermal decomposition has been studied by thermogravimetry (TG), differential thermal analysis (DTA), and explosion delay (DE) measurements. The kinetics of thermal decomposition was evaluated by model fitting and isoconversional methods using TG data. The oxidation-reduction reactions near the surface of thermolysing perchlorates may be responsible for the decomposition followed by explosion. The possible pathways of thermolysis have also been proposed.     

Free-radical reactions of diazonium salts with α,β-unsaturated carbonyl compounds. A new synthesis of 1,4-diarylpyrazole derivatives

Free-radical decomposition of diazonium salts catalyzed by titanous or titanous and ferrous salts in the presence of β-substituted α,β-unsaturated carbonyl compounds leads to 1,4-diarylpyrazole derivatives. The reaction occurs via an intermediate azo compound ( 1 ), which can be reduced by the metal salt or can be isolated and hydrogenated to pyrazole derivatives.     

The use of thermal desorption GC/MS to study weight loss in thermogravimetric analysis of di-acid salts

Thermal desorption gas chromatograph mass spectrometry (TD GC/MS) was used to study weight loss in thermogravimetric analysis (TGA). The technique of thermal desorption utilizes the same temperature heating rate as the TGA to thermally desorb volatiles from solid sample matrices. Volatiles were cryo-trapped at −60 °C. After thermal desorption is complete, the trapped volatiles are separated by a GC capillary column and identified by mass spectrometry. In this study, the TD GC/MS was applied in pharmaceutical development to understand the chemical reactions attributed to the weight loss in the thermal decomposition of two dicarboxylic acid salts of a drug substance. These two salts exhibited different thermal stabilities. The thermally induced chemical reactions obtained from these two salts included dehydration and decarboxylation. Thermal degradation compounds were identified and reaction pathways for decomposition were proposed. The stability of the salts is dependent on the identity of the dicarboxylic acids from which they were generated. The information obtained from TD GC/MS helps better understand the weight loss process in thermogravimetric analysis.     

Kinetic studies of the effects of cobalt salts on tyrosine nitration induced by peroxynitrite

The activation energies for tyrosine nitration and peroxynitrite decomposition catalyzed by cobalt salts were measured. Using these data, the catalysis mechanism was explored and clarified.