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

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

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

Singular Riemannian Foliations, variational problems and Principles of Symmetric Criticalities

A singular foliation $\mathcal{F}$ on a complete Riemannian manifold $M$ is called Singular Riemannian foliation (SRF for short) if its leaves are locally equidistant, e.g., the partition of $M$ into orbits of an isometric action. In this paper, we investigate variational problems in compact Riemannian manifolds equipped with SRF with special properties, e.g. isoparametric foliations, SRF on fibers bundles with Sasaki metric, and orbit-like foliations. More precisely, we prove two results analogous to Palais' Principle of Symmetric Criticality, one is a general principle for $\mathcal{F}$ symmetric operators on the Hilbert space $W^{1,2}(M)$, the other one is for $\mathcal{F}$ symmetric integral operators on the Banach spaces $W^{1,p}(M)$. These results together with a $\mathcal{F}$ version of Rellich Kondrachov Hebey Vaugon Embedding Theorem allow us to circumvent difficulties with Sobolev's critical exponents when considering applications of Calculus of Variations to find solutions to PDEs. To exemplify this we prove the existence of weak solutions to a class of variational problems which includes $p$-Kirschoff problems.Comment: 54 page

A molecular "screw-​clamp": accelerating click reactions in miniemulsions

The interface as a “screw clamp”: the copper-free 1,3-dipolar azide–alkyne cycloaddition at the interface of nanodroplets in miniemulsions was studied in detail by NMR spectroscopic methods. The reaction at the oil–water interface proved to exhibit higher rate constants, increased molecular weights and high regioregularity compared to the reaction in solutio

Clostridia Initiate Heavy Metal Bioremoval in Mixed Sulfidogenic Cultures

Sulfate reducing bacteria (SRB) are widely used for attenuating heavy metal pollution by means of sulfide generation. Due to their low metal tolerance, several SRB species depend on associated bacteria in mixed cultures to cope with metal-induced stress. Yet the identity of the SRB protecting bacteria is largely unknown. We aimed to identify these associated bacteria and their potential role in two highly metal-resistant mixed SRB cultures by comparing bacterial community composition and SRB activity between these cultures and two sensitive ones. The SRB composition in the resistant and sensitive consortia was similar. However, whereas the SRB in the sensitive cultures were strongly inhibited by a mixture of copper, zinc, and iron, no influence of these metals was detected on SRB growth and activity in the resistant cultures. In the latter, a Gram-positive population mostly assigned to Clostridium spp.initiated heavy metal bioremoval based on sulfide generation from components of the medium (mainly sulfite) but not from sulfate. After metal levels were lowered by the Clostridium spp. populations, SRB started sulfate reduction and raised the pH of the medium. The combination of sulfite reducing Clostridium spp. with SRB may improve green technologies for removal of heavy metals

Physicochemical and toxicity investigation of chitosan-based dsRNA nanocarrier formation.

Thus, the present study is focused on the chitosan-dsRNA interactions and the physicochemical properties of the dsRNA-loaded nanoparticles, including cytotoxicity and hemolysis assays. dsRNA molecules homologous to a partial genome of the phytopathogenic tomato mosaic virus (ToMV) were used as the model virus. The combination of chitosan's antimicrobial properties and its delivery capability provides a potential for ds-RNA-nanoparticles to deliver dsRNA as a tool for virus disease control in crops