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.     

Identification of Thermal Decomposition Products and Reactions for Liquid Ammonium Nitrate on the Basis of Ab Initio Calculation

This work analyzed the thermal decomposition of ammonium nitrate (AN) in the liquid phase, using computations based on quantum mechanics to confirm the identity of the products observed in past experimental studies. During these ab initio calculations, the CBS‐QB3//ωB97XD/6–311++G(d,p) method was employed. It was found that one of the most reasonable reaction pathways is HNO₃ + NH₄⁺ → NH₃NO₂⁺ + H₂O followed by NH₃NO₂⁺ + NO₃^– → NH₂NO₂ + HNO₃. In the case in which HNO₃ accumulates in the molten AN, alternate reactions producing NH₂NO₂ are HNO₃ + HNO₃ → N₂O₅ + H₂O and subsequently N₂O₅ + NH₄⁺ → NH₂NO₂ + H₂O. In both scenarios, HNO₃ plays the role of a catalyst and the overall reaction can be written as NH₄⁺ + NO₃^– (AN) → NH₂NO₂ + H₂O. Although the unimolecular decomposition of NH₂NO₂ is thermodynamically unfavorable, water and bases both promote the decomposition of this molecule to N₂O and H₂O. Thus AN thermal decomposition in the liquid phase can be summarized as NH₄⁺ + NO₃^– (AN) → N₂O + 2H₂O.     

Thermal,spectroscopic and XRD studies on nitroaminoguanidine (NAG)

Nitroaminoguanidine (NAG) has been investigated as regards its thermal decomposition characteristics using simultaneous thermal analysis, infrared spectroscopy, X-ray diffraction and polarising microscopy. XRD studies show thatNAG crystal belongs to the tetragonal system. The crystal structure parameters are found to be:a=17.063±0.005Å,b=17.063±0.005Å,c=5.155±0.005Å andc/a axial ratio=0.302. Under non-isothermal conditions,NAG decomposed apparently in one stage with a loss in weight of 80%. But the thermal decomposition ofNAG in the solid phase under isothermal conditions proceeded through three stages. Both the first and the second stages obeyed theA-E (Avrami Erofee'v) equation forn=1. The 3rd stage is too slow and kinetics has not been attempted. The rate parameters for the first and second stages have been evaluated. Gaseous decomposition products detected using the IR gas cell are NH₃, NO₂, HCN, N₂O, CO and CO₂. High temperature IR studies indicate preferential deamination reaction initially indicating breaking of N?NH₂ and C?NH₂ bonds leading to NH₂ radical formation. Addition of diphenylamine, a known chain inhibitor, decelerated the thermal decomposition, supporting a radical chain reaction.     

Comparisons between experimental and calculated rate constants for dissociation and combination reactions involving small polyatomic molecules

The experimental results on decomposition and combination reactions involving O₃, HNO₃, NH₃, C₂N₂, and NO₂Cl over extended temperature and pressure ranges are compared with the deductions from RRKM calculations. Quantitative fits of the data over the entire range are possible only if the external (overall) rotations are assumed to be involved in the reactions. Recommended rate constants for the reactions O + O₂ + N₂ → O₃ + N₂ and OH + NO₂ + N₂ → HNO₃ + N₂ are presented.     

A molecular beam electric deflection study of clusters: acid and salt molecules in microscopic aqueous and ammonia clusters

Results of a molecular beam electric deflection study of the polarity of gas phase clusters comprised of HNO₃H₂O, HNO₃H₂ONH₃, and NH₄HSNH₃ are reported. No refocusing was observed for any species containing more than two molecular subunits. These results are contrasted with previous studies made in our laboratory which showed focusing for higher polymers of acetic acid; possible reasons are given for observed defocusing in the present systems where ion-pair formation is expected to occur.     

Alkene insertion reactions of nitrogen-coordinated acylpalladium(II) complexes. The crystal structure of the dicyclopentadiene insertion product [Pd(C10H12COMe)(bpy)]SO3CF3

The new acylpalladium(II) complex [PdI(COMe)(bpy)] (2b, bpy = 2,2′-bipyridyl) has been obtained by two routes; (i) by insertion of carbon monoxide into the PdC bond of [PdIMe(bpy)] (1b), and (ii) by ligand exchange from [PdI(COMe)(tmeda)] (2a, tmeda = N,N,N′,N′-tetramethylethanediamine). The cationic species obtained by reaction of 2a and 2b with AgOSO₂CF₃ both undergo alkene insertions into the PdC acyl bond that lead to remarkably stable products. The X-ray structure of the dicyclopentadiene insertion product [Pd(C₁₀H₁₂COMe)(bpy)]SO₃CF₃ (4b) shows the oxygen atom of the carbonyl group to be coordinated to the metal center (PdO = 2.026(3) Å).     

Pyrolysis mechanism of urazole by evolved gas analysis

In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry. The gases evolved from TO were determined as HNCO, HCN, N₂, NH₃, CO₂, and N₂O.     

Organoimido complexes of tungsten and rhenium: Oxo-imido and bis-imido complexes of tungsten(VI), and phenylimido complexes of rhenium(VI) and (V). The X-ray crystal structures of [W(NCMe3)(NPh)Cl2(bipy)] and [Re(NPh)Cl3(NH2CMe3)2]

Reaction of Me₃CNH₂ or Me₃SiNHCMe₃ with WOCl₄ gives a mixture containing [W(O)(NCMe₃)Cl₂(NH₂CMe₃)]_x which on further reaction with 2,2′-bipyridyl (bipy) gives [W(NCMe₃)₂Cl₂(bipy)] and insoluble oxo complexes. Reaction of WOCl₄ with p-MeC₆H₄N(SiMe₃)₂ and then bipy gives [W(NC₆H₄Me-p)₂Cl₂(bipy)] and [W(O)(NC₆H₄Me-p)Cl₂(bipy)]; [W(NPh)Cl₄]₂ reacts with p-MeC₆H₄N(SiMe₃)₂ and then bipy to give [W(NPh)(NC₆H₄Me-p)Cl₂(bipy)]. [W(NCMe₃)(μ-NPh)Cl₂(NH₂CMe₃)]₂ and bipy give [W(NCMe₃)(NPh)Cl₂(bipy)] (6). ReOCl₄ reacts with PhNCO to give [Re(NPh)Cl₄]_x which in tetrahydrofuran (THF) or MeCN give the adducts [Re(NPh)Cl₄(THF)] and [Re(NPh)Cl₄(MeCN)]. [Re(NPh)Cl₄]_x reacts with Me₄NCl to give [Me₄N][Re(NPh)Cl₅], with PPh₃ to give [Re(NPh)Cl₃(PPh₃)₂] and with Me₃ SiNHCMe₃ gives [Re(NPh)Cl₃(NH₂CMe₃)₂] (12). The complexes were characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopy. The structures of [W(NCMe₃)(NPh)Cl₂(bipy)] (6) and [Re(NPh)Cl₃(NH₂CMe₃)₂] (12) were determined by single-crystal X-ray diffraction methods. Crystals of (6) are orthorhombic, space group P2₁2₁2₁, with a = 8.879(3) Å, b = 13.036(3) Å, c = 18.837(4) Å; crystals of (12) are orthorhombic, space group Pbcn with a = 14.140(1) Å, b = 11.806(1), Å, c = 11.936(3) Å. Both structures were solved by Patterson and Fourier methods and refined to R values of 0.053 for the 2138 observed data for (6) and 0.035 for the 1108 observed data for (12). In complex (6) the tungsten atom is in a distorted octahedral environment comprising cis-t-butylimido and phenylimido groups, trans chlorides and bidentate bipy. The bipy nitrogens lie trans to the imid o functions. Observed distances are: WN_phenylimido 1.774(8) Å, WN_t-butylimido 1.754(10) Å, WCl 2.412(3) and 2.390(3) Å and WN_bipy 2.312(10) Å and 2.333(9) Å. Interaction between the t-butylimido methyl groups and bipy is relieved by lengthening of one WN_bipy bond. In complex (12) the rhenium atom is in a distorted octahedral environment comprising three chloride ligands, two trans-t-butylamine ligands and a phenylimido ligand. Observed distances are: ReN_phenylimido 1.709(11) Å, ReN_t-butylamine 2.187(7) Å, and ReCl 2.404(2) and 2.411(5) Å. The complex attains an 18-electron count without π-bonding from the chloro ligands.     

Physicochemical properties of ceramic tape involving Ca<Subscript>0.05</Subscript> Ba<Subscript>0.95</Subscript> Ce<Subscript>0.9</Subscript>Y<Subscript>0.1</Subscript>O<Subscript>3</Subscript> as an electrolyte designed for electrolyte-supported solid oxide fuel cells (IT-SOFCs)

Energetic materials such as a mixture of guanidine nitrate (GN)/basic copper nitrate (BCN) are used as gas generators in automotive airbag systems. However, at the time of the airbag inflation, the gas generators release toxic combustion gases such as CO, NH₃, and NO_x. In this study, we investigated the combustion and thermal decomposition behaviors of GN/BCN mixture, focusing primarily on their exhaust gas composition. As a result, when the exhaust gas of the combustion under constant pressure in an inert gas stream was analyzed using a detection tube, the amount of NO_x (mainly NO) yielded greater decrease with increasing atmospheric pressure as compared to the amounts of CO and NH₃. Thus, provided GN/BCN is ignited in a closed container, a large amount of NO_x is presumed to have been released during the initial stage of combustion, which yielded comparatively low pressure. Results of the thermogravimetry–differential scanning calorimetry–Fourier transform infrared spectroscopy (TG/DSC/FTIR) indicated that the GN/BCN mixture caused endothermic decomposition at 170 °C and exothermic decomposition at 208 °C, which was accompanied by 66% mass loss. The decomposition gases, CO₂, N₂O, and H₂O, were detected via FTIR spectrum. Because N₂O was not detected in the combustion gas, it was suggested that the detected N₂O was generated at a low temperature and decomposed in high-temperature combustion.     

The thermal decomposition of the new energetic material ammoniumdinitramide (NH4N(NO2)2) in relation to Nitramide (NH2NO2) and NH4NO3

This qualitative study examines the response of the novel energetic material ammonium dinitramide (ADN), NH₄N(NO₂)₂, to thermal stress under low heating rate conditions in a new experimental apparatus. It involved a combination of residual gas mass spectrometry and FTIR absorption spectroscopy of a thin cryogenic condensate film resulting from deposition of ADN pyrolysis products on a KCl window. The results of ADN pyrolysis were compared under similar conditions with the behavior of NH₄NO₃ and NH₂NO₂ (nitramide), which served as reference materials. NH₄NO₃ decomposes into HNO₃ and NH₃ at 182°C and is regenerated on the cold cryostat surface. HNO₃ undergoes presumably heterogeneous loss to a minor extent such that the condensed film of NH₄NO₃ contains occluded NH₃. Nitramide undergoes efficient heterogeneous decomposition to N₂O and H₂O even at ambient temperature so that pyrolysis experiments at higher temperatures were not possible. However, the presence of nitramide can be monitored by mass spectrometry at its molecular ion (m/? 62). ADN pyrolysis is dominated by decomposition into NH₃ and HN(NO₂)₂ (HDN) in analogy to NH₄NO₃, with a maximum rate of decomposition under our conditions at approximately 155°C. The two vapor phase components regenerate ADN on the cold cryostat surface in addition to deposition of the pure acid HDN and H₂O. Condensed phase HDN is found to be stable for indefinite periods of time at ambient temperature and vacuum conditions, whereas fast heterogeneous decomposition of HDN at higher temperature leads to N₂O and HNO₃. The HNO₃ then undergoes fast (heterogeneous) decomposition in some experiments. Gas phase HDN also undergoes fast heterogeneous decomposition to NO and other products, probably on the internal surface (ca. 60°C) of the vacuum chamber before mass spectrometric detection. © 1993 John Wiley & Sons, Inc.     

Molecular structural of the gauche and trans conformers of ethylamine as studies by gas electron diffraction

The geometrical parameters for the two conformers, gauche (g) and trans (t), of ethylamine have been determined by a joint analysis of the electron diffraction intensity measured in the present study and the rotational constants reported in the literature. The optimized geometries estimated by an SCF MO calculation with a 4-31G(N*) basis set were also used in the analysis to complement the experimental data. The bond lengths (r_g) and the bond angels (r_z) determined are r(CH)_av = 1.107(6) Å r(CN)_t = 1. 470(10)Å, r(CN)_g = 1.475(10) Å r(CC)_t = 1.531(6) Å r (CC)_g = 1.524(6) Å , ∠CCN)_t = 115.0(3)°, and ∠CCCN_g = 109.7(3)°. The uncertainties represent estimated limits of error. The difference between the CCN_g and CCN_g angles predicted by a previous ab initio calculation is confirmed. The enthalpy difference,ΔH(gt), is determined to be 306(200) cal mol⁻¹ using the abundance of the trans conformer, 46(10)%.     

Mass-spectrometric determination of product branching probabilities for the NH2 + NO2 reaction at temperatures between 300 and 990 K

The product branching ratio, α, for N₂O formation in the reaction of NH₂ with NO₂ has been studied by mass spectrometry at seven temperatures between 300 and 990 K. The value of α was determined by kinetic modeling of the absolute yield of N₂O. α was found to be 0.19 ± 0.02 without significant temperature dependence, assuming the total rate constant for NH₂ + NO₂ to be k_t = 1.8 × 10⁻¹² × T^0.11 exp (+ 597/T) cm³/molecule·s in the temperature range studied. The effect of k_t on α has been discussed. © 1996 John Wiley & Sons, Inc. Inc.     

Plasma reactions of methane in nitrogen and nitrogen/oxygen carriers by matrix isolation FTIR spectroscopy

The plasma-induced reactions of traces of methane in nitrogen and nitrogen/oxygen carriers have been investigated by freezing the products onto a 10 K CsI substrate and performing FTIR analysis on the product mixture. Isotopic substitution studies have been used to assist in identification of reaction intermediates and final products. A combination of low (10 mTorr) and high (2 Torr) pressure discharges has also been used to help in the identification of these products. Oxygen concentration was increased in a stepwise fashion to determine its effect on the reaction product distribution. In the present work, methyl radical was the principal product in low-pressure N₂/CH₄ plasmas, and small amounts of HCN and NH₃ were also produced. In the higher-pressure plasmas, HCN and NH₃ were the principal products. As O₂ was added to the plasmas, CO, H₂O, CO₂, N₂O, NO, O₃, HONO, and HNO₃ were produced in approximately the order shown, i.e., CO was formed in good yield at low oxygen partial pressures, but HNO₃ was produced only in slight yield even at the highest oxygen pressures used in this work. These results are discussed in terms of the development of a plasma device having potential application for destruction of environmentally hazardous materials and how trace organic pollutants might react in such a system.     

Thermal behavior and evolved gases analysis of 1,2,4-triazole-3-one derivatives

In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry. The gases evolved from TO were determined as HNCO, HCN, N₂, NH₃, CO₂, and N₂O.     

A diphosphide adduct of ditungsten-hexaisopropoxide: X-ray crystal structure of W2(OPri)6(py)(μ-P2)

From the reaction between W₂(OPrⁱ)₆(py)₂ and CO₂(μ-P₂)(CO)₆ in hexane at room temperature a black crystalline product has been shown to be W₂(OPrⁱ)₆(py)(μ-P₂) by a single crystal X-ray determination. There is a central pseudo tetrahedral W₂P₂ moiety with WW = 2.695(1) Å, PP = 2.154(4) Å and WP = 2.45(2) Å (averaged) corresponding to essentially single bond distances. This new compound is an analogue of the ethyne adducts W₂(OR)₆(py)(μ-C₂H₂), where R = Bu^t and CH₂Bu^t, and these in turn are related to CO₂(CO)₆(μ-X) compounds (X = P₂, C₂R₂) by isolobal relationships.     

Thermal degradation and evolved gas analysis of thiourea-formaldehyde resin (TFR) during pyrolysis and combustion

Thiourea formaldehyde resin (TFR) has been synthesized by condensation of thiourea and formaldehyde in acidic medium and its thermal degradation has been investigated using TG-FTIR-MS technique during pyrolysis and combustion. The results revealed that the thermal decomposition of TFR occurs in three steps assigned to drying of the sample, fast thermal decomposition of polymers, and further cracking. The similar TG and DTG characteristics were found for the first two stages during pyrolysis and combustion. The combustion process was almost finished at 680?°C, while during pyrolysis a total mass loss of 93 wt% is found at 950?°C. The release of volatile products during pyrolysis are NH₃, CS₂, CO, HCN, HNCS, and NH₂CN. The main products in the second stage are NH₃ CO₂, CS₂, SO₂, and H₂O during combustion. In the next stage, the combustion products mentioned above keep on increasing, but some new volatiles such as HCN, COS etc., are identified. Among the above volatiles, CO₂ is the dominant gaseous product in the whole combustion process. It is found that the thermal degradation during pyrolysis of TFR produced more hazardous gases like HCN, NH₃, and CO when compared with combustion in similar conditions.     

利用温度跃升傅立叶变换红外原位分析技术对斯蒂酚酸碳酰肼和斯蒂酚酸氨基脲快速热解反应的研究

Flash pyrolysis of （CHZ）2TNR and （SCZ）2TNR was conducted by T-jump/FTIR spectroscopy under 0.1 MPa Ar atmosphere. The results show that eleven IR-active gas products obtained during flash pyrolysis process of the two title compounds are NO, CO, HCN, NH3, NO2, N2O, HNCO, HNO2, CO2, H2O and HCHO, of which NO and CO are the main gas products. The molar fraction of the individual product in the pyrolysis gas mixture was described as a function of time. At least some of the NO2, N2O and H2O can result from the oxidization reaction of NH3 during flash pyrolysis of （CHZ）2TNR. It can be concluded that the two compounds are not worthy of further in-depth consideration of the adoption in detonators as eco-friendly primary explosive, and should not be used as gas generation composition of automobile crash airbag system taking into account the toxicity.     

Metallorganische diazoalkane : XIII. Reaktionen metallorganischer diazoalkane mit P(NMe2)3 zu metallorganischen phosphazinen LnM(R)CNNP(NMe2)3

Staudinger reactions of 20 organometallic diazoalkanes and of their parent compounds CH₂N₂, HC(N₂)CO₂Et, HC(N₂)C(O)Me and HC(N₂)C(O)Ph with a strong basic phosphine P(NMe₂)₃ are described and were classified into five groups 1–5 of different reactivity.Mono-diazomethanes L_nMCHN₂ (for L_nM = Me₃Si, Me₂As) react to give (cis, trans) isomers of the corresponding phosphazines L_nMC(H)NNP(NMe₂)₃; a stepwise reaction of functional diazogroups in organometallic bis-diazoalkanes, e.g. Hg[C(N₂)CO₂Et]₂, has been observed.Different reactivity of organometallic diazoalkanes cannot be rationalized by known spectroscopic data but can be interpreted by steric effects. In analogy to reactions of isoelectronic azides a transition state of the Staudinger reaction is suggested with an attack of the basic phosphine at the electrophilic α-nitrogen atom and following rearrangement into the N_β-Staudinger adduct.Trimethylgermaniumdiazomethane, Me₃GeCHN₂, was obtained as a novel monosubstituted organometallic diazoalkane and is fully characterized.     

High-pressure range of the recombination O + O2 → O3

The recombination reaction O + O₂ → O₃ was studied by laser flash photolysis of pure O₂ in the pressure range 3–20 atm, and of N₂O? O₂ mixtures in the bath gases Ar, N₂, (CO₂, and SF₆) in the pressure range 3–200 atm. Fall-off curves of the reaction have been derived. Low-pressure rate coefficients were found to agree well with literature data. A high-pressure rate coefficient of k_∞ = (2.8 ± 1.0) × 10^?12 cm³ molecule^?1 s^?1 was obtained by extrapolation.     

A dichromium(II) compound with an elongated metal-metal bond: Cr2(oxindolate)4(oxindole)2

The title compound has been prepared by reaction of (C₅H₅)₂Cr with oxindole (indole with CO in place of CH₂ at the 2-position). Red single crystals belong to space group P2₁/c with a = 10.107(4) Å, b = 22.496(7) Å, c = 9.210(3) Å, β = 93.26(3)°, V = 2091(2), and Z = 2. The centrosymmetric molecule has a CrCr distance of 2.495(4) Å. The mean CrO and CrN distances for the bonds to bridging oxindolate anions are 2.024(7) and 2.065(8) Å, respectively. There is an oxindole molecule bound at each end with a CrO axial bond of length 2.341(8) Å and a hydrogen bond from the oxindole NH group to an equatorial oxygen atom of length 2.83(1) Å. The significance of this compound with respect to CrCr bonding is discussed.