Experimental and simulation study of the high pressure oxidation of dimethyl carbonate

An experimental and modeling study of the oxidation at high pressure of dimethyl carbonate (DMC) has been performed in a quartz tubular flow reactor. Experimental and simulated concentrations of DMC, CO, CO2 and H2 have been obtained for different temperatures (500–1073 K), pressures (20, 40, and 60 atm) and stoichiometries (λ = 0.7, 1, and 35). Both pressure and concentration of oxygen are important parameters for conversion of DMC. The simulations have been carried out using a detailed kinetic mechanism previously developed by the research group. In general, the model is able to reproduce the experimental trends of the different concentration profiles, although some discrepancies are observed between experimental and simulation results. The performance of the model was also evaluated through the simulation of literature data of the oxidation of DMC at atmospheric pressure in a flow reactor and of the DMC ignition delay times under low and high pressures. In this sense, this work contributes to the knowledge of the combustion process of DMC, by providing new experimental data on the conversion of DMC at high pressures and using a kinetic model for the interpretation of the results

Polycyclic aromatic hydrocarbons (PAHs) and soot formation in the pyrolysis of the butanol isomers

The formation of polycyclic aromatic hydrocarbons (PAHs) and soot from the pyrolysis of the four butanol isomers: 1-butanol, 2-butanol, iso-butanol and tert-butanol, at three reaction temperatures (1275, 1375 and 1475 K) has been studied. The identification and quantification of the sixteen PAHs, classified by the Environmental Protection Agency (EPA) as priority pollutants, were done using the gas chromatography–mass spectrometry (GC–MS) technique. The soot formed was collected at the reactor outlet. Light gases formed were also quantified. The harmful potential of the PAHs through the benzoa]pyrene equivalent, Ba]P-eq amount, has been evaluated. The main results show that the highest formation of light gases was obtained from the pyrolysis of iso-butanol at 1275 K. The formation of H2 increases significantly as the temperature increases, following the Hydrogen abstraction carbon addition (HACA) route that leads to form PAHs which subsequently form soot. The tendency to soot formation, under the experimental conditions of the present study, is ranked as follows: tert-butanol, 2-butanol, 1-butanol and iso-butanol. The highest PAHs amount and the highest toxic potential, expressed as Ba]P-eq amount, were found in the pyrolysis of all butanol isomers at 1275 K

Experimental and modeling study of the pyrolysis and combustion of 2-methyl-tetrahydrofuran

De Bruycker R, Tran L-S, Carstensen H-H, et al. Experimental and modeling study of the pyrolysis and combustion of 2-methyl-tetrahydrofuran. COMBUSTION AND FLAME. 2017;176:409-428.Saturated cyclic ethers are being proposed as next-generation bio-derived fuels. However, their pyrolysis and combustion chemistry has not been well established. In this work, the pyrolysis and combustion chemistry of 2-methyl-tetrahydrofuran (MTHF) was investigated through experiments and detailed kinetic modeling. Pyrolysis experiments were performed in a dedicated plug flow reactor at 170 kPa, temperatures between 900 and 1100 K and a N-2 (diluent) to MTHF molar ratio of 10. The combustion chemistry of MTHF was investigated by measuring mole fraction profiles of stable species in premixed flat flames at 6.7 kPa and equivalence ratios 0.7, 1.0 and 1.3 and by determining laminar burning velocities of MTHF/air flat flames with unburned gas temperatures of 298, 358 and 398 K and equivalence ratios between 0.6 and 1.6. Furthermore, a kinetic model for pyrolysis and combustion of MTHF was developed, which contains a detailed description of the reactions of MTHF and its derived radicals with the aid of new high-level theoretical calculations. Model calculated mole fraction profiles and laminar burning velocities are in relatively good agreement with the obtained experimental data. At the applied pyrolysis conditions, unimolecular decomposition of MTHF by scission of the methyl group and concerted ring opening to 4-penten-1-ol dominates over scission of the ring bonds; the latter reactions were significant in tetrahydrofuran pyrolysis. MTHF is mainly consumed by hydrogen abstraction reactions. Subsequent decomposition of the resulting radicals by beta-scission results in the observed product spectrum including small alkenes, formaldehyde, acetaldehyde and ketene. In the studied flames, unimolecular ring opening of MTHF is insignificant and consumption of MTHF through radical chemistry dominates. Recombination of 2-oxo-ethyl and 2-oxo-propyl, primary radicals in MTHF decomposition, with hydrogen atoms and carbon-centered radicals results in a wide range of oxygenated molecules. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved

The sensitizing effects of NO2and NO on methane low temperature oxidation in a jet stirred reactor

The oxidation of neat methane (CH4) and CH4doped with NO2or NO in argon has been investigated in a jet-stirred reactor at 107 kPa, temperatures between 650 and 1200 K, with a fixed residence time of 1.5 s, and for different equivalence ratios (Φ), ranging from fuel-lean to fuel-rich conditions. Four different diagnostics have been used: gas chromatography (GC), chemiluminescence NOxanalyzer, continuous wave cavity ring-down spectroscopy (cw-CRDS) and Fourier transform infrared spectroscopy (FTIR). In the case of the oxidation of neat methane, the onset temperature for CH4oxidation was above 1025 K, while it is shifted to 825 K with the addition of NO2or NO, independently of equivalence ratio, indicating that the addition of NO2or NO highly promotes CH4oxidation. The consumption rate of CH4exhibits a similar trend with the presence of both NO2and NO. The amount of produced HCN has been quantified and a search for HONO and CH3NO2species has been attempted. A detailed kinetic mechanism, derived from POLIMI kinetic framework, has been used to interpret the experimental data with a good agreement between experimental data and model predictions. Reaction rate and sensitivity analysis have been conducted to illustrate the kinetic regimes. The fact that the addition of NO or NO2seems to have similar effects on promoting CH4oxidation can be explained by the fact that both species are involved in a reaction cycle interchanging them and whose result is 2CH3+ O2= 2CH2O + 2H. Additionally, the direct participation of NO2in the NO2+ CH2O = HONO + HCO reaction has a notable accelerating effect on methane oxidation

Radial Diffusion and Penetration of Gas Molecules and Aerosol Particles through Laminar Flow Reactors, Denuders, and Sampling Tubes

Flow reactors, denuders, and sampling tubes are essential tools for many applications in analytical and physical chemistry and engineering. We derive a new method for determining radial diffusion effects and the penetration or transmission of gas molecules and aerosol particles through cylindrical tubes under laminar flow conditions using explicit analytical equations. In contrast to the traditional Brown method [Brown, R. L. J. Res. Natl. Bur. Stand. (U. S.) 1978, 83, 1-8] and CKD method (Cooney, D. O.; Kim, S. S.; Davis, E. J. Chem. Eng. Sci. 1974, 29, 1731-1738), the new approximation developed in this study (known as the KPS method) does not require interpolation or numerical techniques. The KPS method agrees well with the CKD method under all experimental conditions and also with the Brown method at low Sherwood numbers. At high Sherwood numbers corresponding to high uptake on the wall, flow entry effects become relevant and are considered in the KPS and CKD methods but not in the Brown method. The practical applicability of the KPS method is demonstrated by analysis of measurement data from experimental studies of rapid OH, intermediate NO3, and slow O3 uptake on various organic substrates. The KPS method also allows determination of the penetration of aerosol particles through a tube, using a single equation to cover both the limiting cases of high and low deposition described by Gormley and Kennedy ( Proc. R. Ir. Acad., Sect. A. 1949, 52A, 163-169). We demonstrate that the treatment of gas and particle diffusion converges in the KPS method, thus facilitating prediction of diffusional loss and penetration of gases and particles, analysis of chemical kinetics data, and design of fluid reactors, denuders, and sampling lines

Oxidation of Reduced Sulfur Species: Carbon Disulfide

Article on the oxidation of reduced sulfur species and carbon disulfide