2-methylfuran Oxidation in the Absence and Presence of NO

2-methylfuran (2-MF) has become of interest as biofuel because of its properties and the improvement in its production method, and also because it is an important intermediate in the conversion of 2, 5-dimethylfuran. In this research, an experimental and kinetic modelling study of the oxidation of 2-MF in the absence and presence of NO has been performed in an atmospheric pressure laboratory installation. The experiments were performed in a flow reactor and covered the temperature range from 800 to 1400 K, for mixtures from very fuel-rich to very fuel-lean, highly diluted in nitrogen. The inlet 2-MF concentration was 100 ppm. In the experiments in the presence of NO, the inlet NO concentration was 900 ppm. An interpretation of the experimental results was performed through a gas-phase chemical kinetic model. A reasonable agreement between the experimental trends and the modelling data is obtained. The results of the concentration profile of 2-MF as a function of temperature indicate that, both in the absence and in the presence of NO, the onset of 2-MF consumption is shifted to lower temperatures only under fuel-lean and very fuel-lean conditions. Furthermore, under these conditions the presence of NO also shifts the onset of 2-MF consumption to lower temperatures. The effect of the 2-MF presence on the NO reduction varies with the oxygen concentration. It is seen that under very fuel-rich and stoichiometric conditions NO is reduced basically by reburn reactions, while under fuel-lean and very fuel-lean conditions, the NO-NO2 interconversion appears to be dominant

Interaction soot-SO2. Experimental and kinetic analysis

This study aims to evaluate the capability of SO2 to interact with soot and to determine the kinetics of this reaction under conditions of interest for combustion. The conditions of the soot reactivity experiments were: 1% SO2 with nitrogen to balance, around 10 mg of soot, and different reaction temperatures for each run: 1275, 1325, 1375, 1425, and 1475 K. Results demonstrate that SO2 does interact with soot. The evaluation of the soot reactivity has been based on the calculation of the time for the complete conversion of carbon through the employment of the Shrinking Core Model equations for decreasing size particle with chemical reaction control. The reactivity of soot with SO2 increased by a factor of about 3 when increasing the reaction temperature of the test from 1275 K to 1475 K. Kinetics in terms of Arrhenius parameters showed that the activation energy of the interaction of soot with SO2 was around 82 kJ/mol

High pressure ammonia oxidation in a flow reactor

The present work deals with an experimental and modeling analysis of ammonia oxidation at high pressure (up to 40 bar), in the 600–1275 K temperature range using a quartz tubular reactor and argon as diluent. The impact of temperature, pressure, oxygen stoichiometry and presence of NO has been analyzed on the concentrations of NH3 and N2 obtained as main products of ammonia oxidation. The main results obtained indicate that increasing either pressure or stoichiometry results in a shift of NH3 conversion to lower temperatures. The effect of pressure is particularly significant in the low range of pressures studied. The main product of ammonia oxidation is N2, while NO, NO2 and N2O concentrations are below the detection limit for all the conditions considered. The experimental results are simulated and interpreted in terms of a literature detailed chemical kinetic mechanism, which, in general, predicts satisfactorily the experimental results

Effect of H2S on the S-PAH formation during ethylene pyrolysis

The effect of the H2S presence on the formation of six different sulphurated polycyclic hydrocarbons (S-PAH), during the pyrolysis of ethylene-H2S mixtures, has been studied in a tubular flow reactor installation. Experiments with different inlet H2S concentrations (0.3, 0.5 and 1%) and temperatures of reaction (between 1075 and 1475 K) have been carried out. The 16 compounds that the Environmental Protection Agency (EPA) has stated as EPA-PAH priority pollutants were also analysed. EPA-PAH compounds were the majority of quantified PAH, and also S-PAH were found and quantified. For temperatures studied, the S-PAH/EPA-PAH ratio values showed a maximum value at 1075 K and a minimum value at 1175 K. With respect to the effect of the inlet concentration of H2S, the S-PAH/EPA-PAH ratio values increased with the increase of the H2S concentration

Influence of the temperature and 2,5-dimethylfuran concentration on its sooting tendency

The sooting tendency of 2,5-dimethylfuran (2,5-DMF), as a proposed fuel or fuel additive, has been studied in a flow reactor at different reaction temperatures (975, 1075, 1175, 1275, 1375, and 1475 K) and inlet 2,5-DMF concentrations (5000, 7500, and 15,000 ppm) under pyrolytic conditions. The quantification of soot and light gases has been done. Additionally, the experimental results of the light gases have been simulated with a detailed gas-phase chemical kinetic model. The experimental results indicate that the temperature has a great influence on both the soot and gas yields, as well as on the concentration of the light gases of pyrolysis. The inlet 2,5-DMF con- centration influences the soot yield, whereas no significant effect is observed on the gas yield

Sooting propensity of dimethyl carbonate, soot reactivity and characterization

Oxygenated compounds have gained interest in the last few years because they represent an attractive alternative as additive to diesel fuel for reducing soot emissions. Although dimethyl carbonate (DMC) seems to be a good option, studies about its propensity to form soot, as well as the knowledge of the characteristics of this soot are still missing. For that reason, this paper focuses on the potential of DMC to form soot, as well as on the reactivity and characterization of this soot. Results from pyrolysis experiments performed in an atmospheric pressure flow reactor at different temperatures (1075-1475 K) and inlet DMC concentrations (approximately 33, 333 and 50, 000 ppm) show that both soot and gas yields are affected by the pyrolysis temperature, while an increase in the inlet DMC concentration only affects slightly the soot yield, without notable influence on the gas yield. DMC shows a very low tendency to produce soot because the CO/CO2 formation is favoured and thus few carbon atoms are available for soot formation. A chemical kinetic model developed, without incorporating soot particles dynamics, can predict well the gas-phase trends. The comparison of the soot amount profile obtained with the PAH amount profile determined by the model suggests a good first approach toward a model including soot formation. The soot reactivity study toward O2 (500 ppm) and NO (2000 ppm) at 1475 K, as well as its characterization, show that the higher the temperature and the inlet DMC concentration of soot formation, the lower the reactivity of the soot

High pressure oxidation of dimethoxymethane

The oxidation of dimethoxymethane (DMM) has been studied under a wide range of temperatures (373-1073 K), pressures (20-60 bar) and air excess ratios (¿ = 0.7, 1 and 20), from both experimental and modeling points of view. Experimental results have been interpreted and analyzed in terms of a detailed gas-phase chemical kinetic mechanism for describing the DMM oxidation. The results show that the DMM oxidation regime for 20, 40 and 60 bar is very similar for both reducing and stoichiometric conditions. For oxidizing conditions, a plateau in the DMM, CO and CO2 concentration profiles as a function of the temperature can be observed. This zone seems to be associated with the peroxy intermediate, CH3OCH2O2, whose formation and consumption reactions appear to be important for the description of DMM conversion under high pressure and high oxygen concentration conditions

Dimethoxymethane oxidation in a flow reactor

The simultaneous reduction of NOx and soot emissions from diesel engines is a major research subject and a challenge in today’s world. One prospective solution involves diesel fuel reformulation by addition of oxygenated compounds, such as dimethoxymethane (DMM). In this context, different DMM oxidation experiments have been carried out in an atmospheric pressure gas-phase installation, in the 573–1373 K temperature range, from pyrolysis to fuel-lean conditions. The results obtained have been interpreted by means of a detailed gas-phase chemical kinetic mechanism. Results indicate that the initial oxygen concentration slightly influences the consumption of DMM. However, certain effects can be observed in the profiles of the main products (CH4, CH3OH, CH3OCHO, CO, CO2, C2H2, C2H4, and C2H6). Acetylene, an important soot precursor, is only formed under pyrolysis and reducing conditions. In general, a good agreement between experimental and modeling data was observed

Interaction of NH3 and NO under combustion conditions. Experimental flow reactor study and kinetic modeling simulation

The interaction between ammonia and NO under combustion conditions is analyzed in the present work, from both experimental and kinetic modelling points of view. An experimental systematic study of the influence of the main variables for the NH3sbnd]NO interaction is made using a laboratory tubular flow reactor installation. Experiments are performed at atmospheric pressure and variables analyzed include: temperature in the 700–1500 K range, air stoichiometry, from pyrolysis to very oxidizing conditions, and the NH3/NO ratio, in the 0.7–3.5 range. Nitrogen and argon have been used as diluent gas. A literature reaction mechanism has been used to simulate the present experimental results and discuss the main findings. Reaction path analysis has allowed the identification of the reaction routes under the studied conditions. The simulations reflect the main experimental trends observed. Main results show that NO reduction by NH3 occurs at any conditions studied, but is more intense under oxygen excess conditions. Interactions of NH3 and NO proceeds in a molar basis with optimum conversions of NO of up to almost 100%. © 202

High-pressure ethanol oxidation and its interaction with NO

Ethanol has become a promising biofuel, widely used as a renewable fuel and gasoline additive. Describing the oxidation kinetics of ethanol with high accuracy is required for the development of future efficient combustion devices with lower pollutant emissions. The oxidation process of ethanol, from reducing to oxidizing conditions, and its pressure dependence (20, 40 and 60 bar) has been analyzed in the 500–1100 K temperature range, in a tubular flow reactor under well controlled conditions. The effect of the presence of NO has been also investigated. The experimental results have been interpreted in terms of a detailed chemical kinetic mechanism with the GADM mechanism (Glarborg P, Alzueta MU, Dam-Johansen K and Miller JA, 1998) as a base mechanism but updated, validated, extended by our research group with reactions added from the ethanol oxidation mechanism of Alzueta and Hernández (Alzueta MU and Hernández JM, 2002), and revised according to the present high-pressure conditions and the presence of NO. The final mechanism is able to reproduce the experimental trends observed on the reactants consumption and main products formation during the ethanol oxidation under the conditions studied in this work. The results show that the oxygen availability in the reactant mixture has an almost imperceptible effect on the temperature for the onset of ethanol consumption at a constant pressure, but this consumption is faster for the highest value of air excess ratio (¿) analyzed. Moreover, as the pressure becomes higher, the oxidation of ethanol starts at lower temperatures. The presence of NO promotes ethanol oxidation, due to the increased relevance of the interactions of CH3 radicals and NO2 (from the conversion of NO to NO2 at high pressures and in presence of O2) and the increased concentration of OH radicals from the interaction of NO2 and water