Gaseous HC Research Articles

Infrared Emission from Photodissociation of Methyl Formate [HC(O)OCH3] at 248 and 193 nm: Absence of Roaming Signature.

Following photodissociation at 248 nm of gaseous methyl formate (HC(O)OCH3, 0.73 Torr) and Ar (0.14 Torr), temporally resolved vibration-rotational emission spectra of highly internally excited CO (ν ≤ 11, J ≤ 27) in the 1850-2250 cm-1 region were recorded with a step-scan Fourier-transform spectrometer. The vibration-rotational distribution of CO is almost Boltzmann, with a nascent average rotational energy (ER0) of 3 ± 1 kJ mol-1 and a vibrational energy (EV0) of 76 ± 9 kJ mol-1. With 3 Torr of Ar added to the system, the average vibrational energy was decreased to EV0 = 61 ± 7 kJ mol-1. We observed no distinct evidence of a bimodal rotational distribution for ν = 1 and 2, as reported previously [Lombardi et al., J. Phys. Chem. A 2016, 129, 5155], as evidence of a roaming mechanism. The vibrational distribution with a temperature of ∼13000 ± 1000 K, however, agrees satisfactorily with trajectory calculations of these authors, who took into account conical intersections from the S1 state. Highly internally excited CH3OH that is expected to be produced from a roaming mechanism was unobserved. Following photodissociation at 193 nm of gaseous HC(O)OCH3 (0.42 Torr) and Ar (0.09 Torr), vibration-rotational emission spectra of CO (ν ≤ 4, J ≤ 38) and CO2 (with two components of varied internal distributions) were observed, indicating that new channels are open. Quantum-chemical calculations, computed at varied levels of theory, on the ground electronic potential-energy schemes provide a possible explanation for some of our observations. At 193 nm, the CO2 was produced from secondary dissociation of the products HC(O)O and CH3OCO, and CO was produced primarily from secondary dissociation of the product HCO produced on the S1 surface or the decomposition to CH3OH + CO on the S0 surface.

Lateritic saprolite leaching in concentrated magnesium chloride media

Magnesium chloride brines present a number of potential advantages for the processing of lateritic saprolite ores for nickel production. Concentrated MgCl2 solutions enhance the activity of acid used, allow atmospheric leaching at elevated temperature, and inhibit magnesium dissolution, which reduces acid consumption and increases metal selectivity. However, with a chloride based leach it is economically requisite to recover hydrochloric acid, conventionally accomplished by pyrohydrolysis. This work was performed in conjunction with a novel flowsheet for the processing on saprolite ores, which recovers HCl by the precipitation and subsequent decomposition of magnesium hydroxychlorides, alleviating some of the issues with pyrohydrolysis. Leaching experiments have been conducted in concentrated MgCl2 brines, up to 4·5 m, to determine the amenable process conditions and explore the kinetics of the process. It was determined that >95% extraction of metals was possible using both aqueous and gaseous HCl, while suppressing the dissolution of Mg from the ore.Les saumures de chlorure de magnésium présentent un nombre d’avantages potentiels dans le traitement des minerais de saprolite latéritique pour la production du nickel. Les solutions concentrées de MgCl2 augmentent l’activité de l’acide utilisé, permettent la lixiviation atmosphérique à haute température, et inhibent la dissolution du magnésium, ce qui réduit la consommation d’acide et augmente la sélectivité du métal. Cependant, avec une lixiviation à base de chlorure, on doit récupérer l’acide hydrochlorique pour raison économique, ce qui est accompli conventionnellement par pyrohydrolyse. On a effectué ce travail en conjonction avec un nouveau schéma de procédé pour le traitement des minerais de saprolite, lequel récupère le HCl par précipitation et par décomposition subséquente des hydroxychlorures de magnésium, ce qui atténue certains des problèmes reliés à la pyrohydrolyse. On a effectué des expériences de lixiviation dans des saumures concentrées de MgCl2, jusqu’à 4·5 m, afin de déterminer les conditions favorables du procédé et d’explorer la cinétique du procédé. On a déterminé qu’il était possible d’extraire >95% des métaux en utilisant à la fois le HCl aqueux et gazeux, tout en supprimant la dissolution du Mg du minerai.

Uptake of Organic Acids on Ice Surfaces: Evidence for Surface Modification and Hydrate Formation

Abstract The uptake of gaseous HC(O)OH, CH3 C(O)OH and CF3C(O)OH on ice films at temperatures corresponding to the upper troposphere (UT) has been investigated using a coated-wall flow tube with mass spectrometric measurement of gas concentration. Uptake was largely reversible and followed Langmuir-type kinetic behavior, i.e. surface coverage increased with trace gas concentration approaching a maximum surface coverage at N max ~2 to 3×1014 molecules cm−3, corresponding to ~25% monolayer (ML). The partition constants, KLinC , were obtained from the experimental data by analysis using the simple Langmuir model and also using a simple one-dimensional numerical model to simulate individual uptake profiles and retrieve partition constants for specific conditions of temperature and concentration, over the temperature range 208–238 K. The analysis showed that Langmuir constants decreased at high surface coverages, possibly due to adsorbate-adsorbate interaction or modification of the ice surface. At low coverage, the following expressions described the temperature dependence of the partition coefficients (KLinC) for HC(O)OH (KLinC = (1.5±3.5 1.0)×10−8exp((5143±268)/T) cm), for CH3 C(O)OH (KLinC = (0.55±5.4 0.5)×10−8exp((5703±536)/T) cm), and CF3C(O)OH (KLinC = (512±1903 404)×10−8exp((309±331)/T) cm). For CF3C(O)OH there was an irreversible component of uptake, which was attributed to hydrate formation on the surface.

Polarizability anisotropies, magnetizability anisotropies and molecular quadrupole moments of acetylene, methylacetylene and dimethylacetylene

Measurements of the Rayleigh depolarization ratios (with and without inclusion of the vibrational Raman contributions), Cotton-Mouton effects and electric field-gradient induced birefringences of gaseous HCCH, HCCCH 3 and CH 3CCCH 3 at 632.8 nm are analyzed in conjunction with other data to obtain reliable values of the polarizability anisotropies, magnetizability anisotropies and quadrupole moments of these molecules.

The effects of combustion and injection systems on uuburnt HC and particulate emissions from a DI diesel engine.

This paper investigates the effects of combustion and infection systems on HC and particulate emissions from a DI diesel engine with a dish type combustion chamber. Diesel particulate was sampled using a mini-dilution tunnel. Gaseous HC was analysed with gas chromatography, and the PAH in SOF in the particulates was measured with liquid chromatography. The results show that the emission characteristics of the deep dish type chamber greatly differs from those of the shallow dish type chamber, depending on the number of nozzles, injection direction, and swirl intensity. The HC analysis shows that the main constituents of gaseous HC are carbon number HC, and there is a tending towards increasing polynucleation PAH in SOF corresponding to the increase in soot formation. Additionally it was found that the particulate concentration can be expressed as an exponential function of the Bosch smoke density for a wide range of engine combustion conditions.

AB Initio approach to the cyanoform problem

Relative stabilities of suggested components of gaseous HC 4N 3 have been calculated Ab Initio using a 7 s, 3 p basis set contracted to 4 s, 2 p. Molecular structures in accordance with experimental data for related molecules were assumed. The result is that cyanoform, HC(CN) 3, dominates the gas phase under conditions of equilibrium. A competing species, “di-cyanoketenimine”, HNCC(CN) 2, is ca. 10 kcal mol −1 higher in energy. According to (incomplete) ir data it may dominate the crystalline phase.

Infrared Spectra and Potential Constants of Some Monohaloacetylenes

The infrared spectra of gaseous HC≡CF, HC≡CCl, and HC≡CBr and their deutero-compounds have been obtained under prism dispersion between 250 and 3500 cm—1. All five fundamental vibrations have been identified for each of the hydrogen compounds and all but the lower bending mode for each of the deuterated compounds. Potential constants and vibrational amplitudes have been calculated.

Infra-red and Raman spectra of propynal

The infra-red spectra of gaseous HCCCHO, HCCCDO and DCCCHO and the Raman spectrum of liquid HCCCHO have been determined. Vibrational assignments are given and the spectra correlated.