Gas-phase Decomposition Products Research Articles

Decomposition of Benzene during Impacts in N2-dominated Atmospheres

Benzene is a simple neutral aromatic compound found in molecular clouds, comets, and planetary atmospheres. It has been confirmed on Jupiter, Saturn, Titan, and is expected on exoplanets. In this paper, the decomposition of benzene in a simulated asteroid or comet impact into an N2-dominated atmosphere was investigated. The impact plasma was simulated with laser-induced dielectric breakdown and the gas phase decomposition products were observed using high-resolution Fourier transform infrared spectroscopy. The gas phase decomposition products involve mainly HCN, C2H2, and smaller amounts of CH4 with yields of 3.1%–24.0%, 0–11.7%, and 0.5%–3.3%, respectively. Furthermore, in presence of water, benzene also produces CO and CO2 with yields of 2.4%–35.1% and 0.01%–4.8%, respectively. The oxidation state of the product mixture is proportional to the water content. Apart from that, a black-brownish solid phase is formed during the experiments, which makes up about 60% of the original carbon content. Our results therefore show that in anoxic N2-dominated planetary atmospheres, impacts might lead to the depletion of benzene and the formation of HCN, C2H2, and CH4 and, in the presence of water, to the formation of CO and CO2.

Passive Vaping from Sub-Ohm Electronic Cigarette Devices.

To investigate passive vaping due to sub-ohm electronic cigarettes (e-cigs), aerosol number size distribution measurements (6 nm–10 µm) were performed during volunteer-vaping sessions. E-liquids, with vegetable glycerin (VG) and propylene glycol (PG), with a VG/PG ratio of 50/50 (with nicotine) and 80/20 (without nicotine), were vaped with a double-coil, single aerosol exit hole at 25–80 W electric power, corresponding to 130–365 kW m−2 heat fluxes and with an octa-coil, four aerosol exit holes atomizers, at 50–150 W electric power, corresponding to 133–398 kW m−2 heat fluxes. At the lowest heat flux, lower particle number concentrations (NTot) were observed for the nicotine-liquid than for the nicotine-free liquid, also due to its higher content of PG, more volatile than VG. For the octa-coil atomizer, at 265 and 398 kW m−2, NTot decreased below the first-generation e-cig, whereas volume concentrations greatly increased, due to the formation of super micron droplets. Higher volume concentrations were observed for the 80/20 VG/PG liquid, because of VG vaporization and of its decomposition products, greater than for PG. For the double coil atomizer, increasing the electric power from 40 W (208 kW m−2) to 80 W (365 kW m−2) possibly led to a critical heat flow condition, causing a reduction of the number concentrations for the VG/PG 50/50 liquid, an increase for the 80/20 VG/PG liquid and a decrease of the volume concentrations for both of them. Coherently, the main mode was at about 0.1 µm on both metrics for both liquids. For the other tests, two main modes (1 and 2 µm) were observed in the volume size distributions, the latter becoming wider at 100 and 150 W (265 and 398 kW m−2), suggesting the increased emission of light condensable decomposition products. The lower aerosol emissions observed at 150 W than at 100 W suggest the formation of gas-phase decomposition products. The observation of low-count high-volume aerosols addresses the relevance of the volume metric upon measuring the second-hand concentration of the aerosols released by sub-ohm e-cigarettes.

Catalysis of the Thermal Decomposition of Transition Metal Nitrate Hydrates by Poly(vinylidene difluoride).

Poly(vinylidene difluoride) (PVDF) doped with transition metal nitrate hydrates are cast into thin films giving a high β-phase content. Analysis of the thermal behavior of the doped PVDF shows that the decomposition of the metal (II) nitrate hydrates to metal (II) oxides is catalyzed by the PVDF, as evidenced by reduction in the decomposition temperature by as much as 170 °C compared to the pure metal salts. In contrast, there is little to no apparent catalysis for the decomposition of the metal (III) nitrate hydrates. The FTIR spectra of the gas phase decomposition products show H2O and NO2 are the major components for both PVDF-doped material and the pure metal nitrate hydrates. A mechanism for the role of PVDF is proposed that uses the internal electric field of the ferroelectric phase to orient the nitrate ions and polarize the N–O bonds.

Theoretical Reassessment and Model Validation of Some Kinetic Parameters Relevant to Si/Cl/H Systems.

The increasing demand for silicon-based materials requires the optimization of silicon deposit manufacturing processes and therefore a better understanding of the gas-phase reactivity of silicon precursors such as silicon tetrachloride (SiCl4). In the present work, hydrogen atom resonance absorption spectroscopy (H-ARAS) has been used to investigate the high-temperature reactivity of SiCl4 behind reflected shock waves at ∼1.5 atm in the presence of either ethyl iodide or molecular hydrogen, used as H atom precursors. Several key reactions of SiCl4 and its main gas-phase decomposition products (SiCl3, Cl, SiHCl3, SiHCl2) have been determined theoretically. The structures and vibrational frequencies of reactants, products, and tight transition states were determined at the B2PLYP-D3/aug-cc-pVTZ level and final single-point energies refined from extrapolated RCCSD(T)/aug-cc-pVnZ (n = D, T, and Q) calculations. The minimum-energy paths of barrierless reactions were calculated at the NEVPT2 level. Final rate constants were then derived from the transition-state theory (TST) and the variational TST/master equation analysis within the rigid rotor harmonic oscillation framework. A kinetic mechanism was assembled, based on the present ab initio calculations, to successfully model and interpret the experimental absorption profiles. Sensitivity analysis unambiguously highlighted the need to account for pressure dependence in the SiCl4 decomposition (SiCl4 ⇄ SiCl3 + Cl) while discarding previous theoretical and experimental determinations of this rate constant.

Fire and explosion hazards of ionic liquid 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide

Low volatility materials that do not emit sufficient vapor to form a combustible mixture with air, under temperate conditions, are considered a lower fire hazard than materials with higher volatility. Because ionic liquids have very low volatility, they are widely considered to be green alternatives to organic solvents and have long been considered nonflammable. However, recent research has indicated some ionic liquids are flammable because of the auto-ignition of their thermal decomposition products rather than the combustion of the vapors itself. Ionic liquid 1-methyl-1-propylpyrrolidine bis(trifluoromethanesulfonyl)imide has been reported to be an electrolyte base candidate for lithium batteries, and many electrochemical characteristics of this ionic liquid have been extensively investigated. Characteristics about its fire and explosion hazards, however, are still not reported in the literature. It is obvious that such information is indispensable to safely use this ionic liquid.In this study, the fire and explosion hazards of ionic liquid 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide are investigated via auto-ignition tester, TGA/DSC and TGA-FTIR. It is found that the auto-ignition temperature of this ionic liquid is 441 °C with the ignition delay time of 38.2 s. The decomposition process of this ionic liquid is found to be endothermic in the nitrogen atmosphere, but it is exothermic in the air atmosphere. Further TGA/DSC experiments indicate that in the air atmosphere the amount of heat release will increase as the reaction gas purge rate increases, but in the nitrogen atmosphere the amount of heat absorbed is independent of the reaction gas purge rate. It is also found from TGA-FTIR experiments that in the air atmosphere the concentration of carbon dioxide in the evolved gas was much higher than that in the nitrogen atmosphere. Moreover, carbon monoxide is observed in the air atmosphere, but is not observed in the nitrogen atmosphere. If in the air atmosphere the spontaneous combustion of the gas-phase decomposition products occurs, aforementioned observations can be reasonably explained.

Thermocatalytic Studies on Municipal Solid Waste

Abstract The goal of this study was to upgrade the decomposition products of municipal solid waste applying different catalysts during slow and high heating rate pyrolysis. The municipal waste studied was a mixture of biomass and plastics in a ratio of 1:1. Different zeolites (β- and Y-zeolites, ZSM-5 and FCC catalysts) and nickel-molybdenum (NiMo/Al 2 O 3 ) catalysts were tested in order to upgrade the quality of the decomposition product mixture. The applied sample-catalyst ratio was 2:1. The evolution profiles of the gas phase decomposition products were monitored by thermogravimetry/mass spectrometry (TG/MS). The product distribution was analyzed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) technique. The effect of the catalysts on the biomass part of the waste sample is very similar. The thermal decomposition of the plastic fraction is catalyzed mainly by β-zeolite and ZSM-5, as the thermogravimetric and the mass spectrometric data indicate. The pyrolysis results unambiguously show the cracking effects of the applied catalysts on the composition of the evolving hydrocarbon mixture. The yield of the aromatic products is increased significantly.

Thermal Decomposition Products and Pathways of Novel Organosilicon Electrolytes for Lithium-Ion Batteries

Conventional lithium-ion battery carbonate-based electrolytes have displayed thermal instability and decomposition, leading to performance fade and concerns about the safety of these energy storage devices. In collaboration with the University of Wisconsin, Silatronix, Inc. has developed a novel class of organosilicon solvents for battery electrolytes which have enhanced thermal stability, long cycle lifetime, and decreased electrolytic gas evolution. We have studied the thermal stability of electrolyte systems with organosilicon solvents in comparison with conventional carbonate electrolytes. We report the quantitative analysis of solution and gas phase decomposition products over the course of several weeks under conditions of high heat and artificially increased water content. Our comparative studies of carbonate and organosilicon electrolyte thermal hydrolysis include discovery of an important donor-acceptor complex, computational modeling to identify key decomposition intermediates, and the development of kinetic degradation models. These studies help us to understand what gives rise to the superior thermal stability of these electrolyte solvents.

Transformation of Mo and W thiosalts into unsupported sulfide catalysts: A temperature dependent in-situ spectroscopic investigation

The thermal decomposition of ammonium thiomolybdate (ATM), ammonium thiotungstate (ATT), tetramethylammonium thiomolybdate (TMATM) and tetramethylammonium thiotungstate (TMATT) are investigated as a function of temperature by using thermogravimetric analysis (TGA), temperature-programmed decomposition with mass spectroscopy (TPS–MS), in-situ Fourier transform infrared (FTIR) and Raman spectroscopies, and X-ray photoelectron spectroscopy (XPS). The results allow for correlations to be made between the changes in the bulk and surface structures of the materials, and the evolution of gas-phase decomposition products. The major difference between the ammonium and tetramethylammonium precursors is the complexity of the thermal decomposition profile, which is found to follow two steps over a wide temperature range for the former, but one step over a relatively narrow range for the latter materials. Raman and FTIR spectra reveal the decomposition of the ammonium and tetramethylammonium groups, along with the decomposition of the initial sulfide structures to metal disulfides. For both sets of precursors, XPS results show that the surface of the resulting materials at various temperatures of treatment does not track directly with the state of the bulk material. While the ATM, TMATM, and TMATT-derived material surfaces are reduced to the 4+ state at the highest temperature, indicating disulfides, the ATT-derived materials still retained a significant amount of W6+ state consistent with the starting precursor.

Photoluminescence spectroscopy of 2-nitrotoluene and its photo and photothermal decomposition derivatives

Abstract 2-Nitrotoluene (2-NT) is subjected to thermal, photo, and photothermal aging to determine its gas-phase decomposition products via GC/MS. Besides 2-nitrotoluene, the following decomposition products are detected in the gas phase: toluene, 2-nitrosotoluene, 2-cresol, and 2-toluidine. Time resolved laser spectroscopy is used to identify the spectroscopic signatures of these gas-phase products. 2-Nitrotoluene photodissociates during the measurement, leading to the formation of NO and atomic carbon C I, and the observation of their characteristic spectroscopic signatures. Energy transfer between molecular nitrogen and NO is observed. A spectroscopic signature from 2-nitrotoluene in nitrogen with concentrations as low as about 100 ppt is observed. The toluene spectra show a broad emission centered at about 280 nm. The spectroscopic signature of 2-nitrosotoluene is similar to that of 2-NT, and the spectrum is dominated by emission from NO. However, unlike for 2-nitrotoluene, no C I is observed and energy transfer from nitrogen is not apparent. Even with a poorly matched excitation wavelength, the spectrum of 2-cresol shows a strong and broad emission peak centered at about 300 nm, which is promising for the detection of aged 2-nitrotoluene. No useful spectroscopic signatures are seen in the spectra of 2-toluidine.

Thermal decomposition course of Eu(CH 3COO) 3·4H 2O and the reactivity at the gas/solid interface thus established

The thermal decomposition course of europium acetate tetrahydrate (Eu(CH 3COO) 3·4H 2O) was probed on heating up to 1000 °C in a dynamic atmosphere of air by thermogravimetry and differential thermal analysis. The solid- and gas-phase decomposition products were identified by X-ray diffractometry, ex- and in situ infrared spectroscopy and mass spectrometry. Results obtained showed the acetate to dehydrate stepwise at 145–283 °C, and then decompose stepwise to yield eventually cubic-Eu 2O 3 at ≥663 °C encompassing the formation of intermediate oxycarbonate (Eu 2O(CO 3) 2/Eu 2O 2(CO 3) solid products (at 347–466 °C)) and H 2O, (CH 3) 2CO and CO 2 as primary gaseous products. A considerable enhancement of the production of the primary gas phase products at 400–450 °C and the emergence of (CH 3) 2C CH 2, CH 4 and CO molecules in the gas phase are ascribed to reactions occurring at the gas/solid interface at the expense of some of the primary products. These interfacial activities impart application-worthy adsorptive and catalytic functions for the associated solid products.

Theoretical Study of the Primary Processes in the Thermal Decomposition of Hydrazinium Nitroformate

The primary reactions of the thermal decomposition of hydrazinium nitroformate (HNF) as well as ammonium nitroformate (ANF) were investigated theoretically using the G3 multilevel procedure. Calculations were performed for the reactions in the gas phase and in the melt using a simplified model of the latter. The influence of the melt on the reaction barriers was taken into account by calculation of the solvation free energies using a PCM model. In contrast with many other energetic salts, the ionic salt structures of the HNF and ANF were found to be minima on the PES. However, the most energetically favorable structures of the HNF and ANF in the gas phase are H-bonded complexes. In the melt, on the contrary, the ionic structure is lowest in free energy because of solvation effects. In both the gas phase and melt, the HNF decomposes preferably to nitroform and hydrazine. This fact agrees well with the experimentally observed absence of HNF among the gas-phase decomposition products. Thermolysis of HNF occurs mainly through the intermediacy of nitroform; computations do not support the suggestion that the aci-nitroform is an important intermediate of HNF thermolysis. The primary dissociation reactions of ANF resemble those of the HNF.

Kinetic study of decomposition of peroxypropionic acid in liquid phase through direct analysis of decomposition products in gas phase

Decomposition of peroxypropionic acid (PPA) takes place in the liquid phase, but the main products of decomposition, carbon dioxide and oxygen are transferred to gas phase. An analytical method was developed to determine the decomposition of PPA in liquid phase by means of chemical analysis of gas phase. The method is based on on-line mass spectroscopy (MS). A mathematical model for the semi-batch gas–liquid system was developed. The model comprised both kinetic and mass transfer effects. A comparison between experimental results and results predicted from the mathematical model revealed that the model can describe the essential effects of decomposition kinetics.

Adiabatic Calorimetric Decomposition Studies of 35 Mass% Hydroxylamine Hydrochloride/water

AbstractThe HH (35 mass% hydroxylamine hydrochloride/water solution) and HH‐ind (stabilized 35 mass% hydroxylamine hydrochloride/water solution for industrial use) decomposition reaction has an onset temperature of ∼145°C. The measured gas phase decomposition products are 0.25 mol N2 and 0.06 mol O2 per mol of hydroxylamine hydrochloride with small quantities of N2O and H2, and a trace amount of NO for a total noncondensable gas production of ∼0.39 mol/mol of hydroxylamine hydrochloride. The reaction system is tempered by the evaporation of the solvent (water) and the reaction is drastically catalyzed by stainless and carbon steel.

Structural Investigation of the Thermal Decomposition of Ammonium Heptamolybdate by in situ XAFS and XRD.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Decomposition Products of 50 Mass% Hydroxylamine/Water Under Runaway Reaction Conditions

I n the present work, the gaseous and liquid decomposition products of 50 mass% hydroxylamine/water solution were measured for samples subsequent to a thermally induced runaway reaction. The noncondensablegas phase composition was approximately 70 mol% N2, 24 mol% N2O, 4mol% NO, and 2 mol% H2, and ammonia was detected in the liquid residue. Based on analysis of the gas phase decomposition products, the following overall decomposition reaction (summation of several series and parallel reaction mechanisms taking place during the experiment) was determined: 157NH2OHliq → 61NH3gas + 35N2gas + 12N2Ogas + 2NOgas + 143H2Ogas + H2gas This reaction has an associated theoretical standard heat of reaction of −124 kJ mol−1(−29.6 kcal mol−1), which is consistent with −117 kJ mol−1 (−28 kcal mol−1) estimated for the hydroxylamine overall heat of decomposition reported previously.

Characterization of lanthanum oxide formed as a final decomposition product of lanthanum acetylacetonate: thermoanalytical, spectroscopic and microscopic studies

The porous and high surface area of lanthanum oxide was obtained as a final decomposition product of lanthanum acetylacetonate tetrahydrate. The decomposition course in dry nitrogen was thoroughly studied. Thermal processes occurring throughout the decomposition range (100–800 °C) were monitored by thermogravity; differential thermal analysis and infrared spectroscopy gaseous products. These processes were characterized on the basis of the solid products analyses, using X-ray diffractometry and IR-spectrometry. The results showed La(C 5H 7O 2) 3 completely decomposed to La 2O 3 at 730 °C, through amorphous and unstable intermediates La(CH 3COO)(C 5H 7O 2) 2 at 190 °C, La(CH 3COO) 2(C 5H 7O 2) at 225 °C, La(CH 3COO) 3 at 285 °C, La 2(CO 3) 3 at 390 °C and crystalline and stable La 2O 2(CO 3) at 430 °C. Gas phase decomposition products included propyne, acetone, carbon oxides, methane and isobutene. Methane and isobutene resulted from interfacial reactions involving the initial product (acetone). The ultimate products, La 2O 3 at 700 °C and 800 °C, are crystalline porous solids and having a surface area of 21 and 45 m 2/g respectively.

Physicochemical investigation of the decomposition products of ammonium metal carboxylates: ammonium ferric citrate hydrate

The thermal decomposition up to 400 °C of ammonium ferric citrate hydrate, of unknown structure and formula weight, was studied by thermogravimetry, differential thermal analysis, infrared (IR) spectroscopy and X-ray diffractometry. The possible identities of the formula weight and the intermediate products of calcination are discussed. The results revealed that the parent material is amorphous and contains two moles of water and two moles of ammonia. Decomposition takes place via six weight-loss processes, three endothermic (90–230 °C) and three exothermic (240–298 °C), leading eventually to the formation of Fe 2O 3. The intermediate solid products are mainly unstable amorphous oxycarbonates, as indicated by X-ray and IR spectroscopies. The gas-phase decomposition products identified by IR spectroscopy are NH 3, CO 2, CO, CH 3COCH 3, CH 4 and NH 4OH. Surface area measurement and scanning electron microscopy showed that Fe 2O 3, the final product at 400 °C, hada surface area of 40 m 2/g and good crystalline and porous character.

Formation of praseodymium oxide from the thermal decomposition of hydrated praseodymium acetate and oxalate

Thermogravimetry, differential thermal analysis, infrared spectroscopy, X-ray diffractometry and surface area measurements were used to characterize the thermal decomposition of the hydrated acetate and oxalate of praseodymium in air. Non-isothermal kinetic parameters ( A, Δ E) were determined for the thermal events monitored throughout the decomposition course. The results showed that Pr(CH 3COO) 2·H 2O became dehydrated at 180°C, melted at 270°C and decomposed to PrO 1.833 at 575°C through intermediate oxy-carbonate compounds. In contrast, Pr 2(C 2O 4) 3·10H 2O dehydrates completely in three steps by 390°C, and then decomposes similarly to PrO 1.833. The oxide formed from the acetate precursor has a higher surface area (18 M 2/g) than that obtained from the oxalate precursor (8 m 2/g). The gas-phase decomposition products identified by infrared spectroscopy are acetone, acetic acid, carbon oxides, methane and isobutene. Some of these were initial decomposition products, whereas others (methane and isobutene) were interfacial reaction products involving initial ones.

Synthesis of new mixed-alkyl rhenium(VII) organoimido complexes and a new facile route to Me 3SiORe(NBu t) 3

Alkylation of the rhenium(VII) dichloro compound of the formula MeRe(NR′) 2 Cl 2Py ( 1) with MeMgCl, Et 2Zn and Pr iMgCl yields the d 0 trialkyl diimido complexes of the formula MeR 2Re(NR′) 2 ( 2a–c) (R = Me, Et, Pr i; R′ = 2,6-dimethylphenyl). Compound 2a is stable at 25°C, while compounds 2b and c decompose within a few hours. In a similar manner the alkylation of the new tert-butyl imido derivative MeRe (NBu t) 2Cl 2 ( 4) [prepared from MeRe(NBu t) 3 ( 3) by hydrochlorination] yields the trialkyl complexes of the formula MeR 2Re(NBu t) 2 ( 5a–c) (R = Me, Et and Pr i), of which the mixed-alkyl species are again thermolabile. Analysis of the gas-phase decomposition products revealed a rather complex decomposition pathway, in which the β-hydrogen elimination is likely to play a minor role. Reaction of the polymeric oxo species of the formula Me 3SnOReO 3 ( 6) with the silylamine Bu tNHSiMe 3 gives, surprisingly cleanly, the monomeric tris-imido compound of the formula Me 3SiORe(NBu t) 3 ( 7 in 93% yield.

Optical monitoring of deposition and decomposition processes in MOCVD and MBE using reflectance anisotropy

A series of experiments have been performed in order to assess the ability of reflection anisotropy (RA) to follow the MBE growth of GaAs and AlAs on (001) GaAs, combined RA/RHEED measurements reveal a layer-by-layer growth mechanism as indicated by periodic RA oscillations. For the growth of the lattice mismatched GaAs/InAs heterostructure large RA transients are observed which are found to reach their maximum during the growth of the first monolayer and before the onset of 3D growth. RA studies have also been carried out during the MOCVD decomposition of triethylgallium (TEGa) on (001) GaAs at several temperatures ranging from 300 to 425°C. Results obtained suggest that TEGa begins to fully decompose at 350°C which is found to correlate with the formation of TEGa gas phase decomposition products. Results are also presented which may indicate a change in surface reconstruction under MOCVD conditions on moving from a Ga-rich to an As-rich surface state.