Impact of Tetrabutylammonium on the Oxidation of Bromide by Ozone
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ABSTRACT:
SUBMITTER: Chen S
PROVIDER: S-EPMC8607506 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Deep eutectic solvents have quickly attracted the attention of researchers because they better meet the requirements of green chemistry and thus have the potential to replace conventional hazardous organic solvents in some areas. To better understand the nature of these mixtures, as well as expand the possibilities of their use in different industries, a detailed examination of their physical properties, such as density, viscosity, the nature of the interactions between their constituents, the phase diagrams, depression of their melting point, and interpretation of these results is necessary. In this work, the mixtures of tetrabutylammonium bromide (TBAB) and nonanoic acid (NA) in different molar ratios are theoretically and experimentally investigated by applying a phase diagram constructed on the basis of differential scanning calorimetry measurements and COSMO-RS model. Spectral properties are investigated based on Fourier transform infrared spectroscopy and density functional theory. The observed eutectic point indicates the formation of a DES in the TBAB-NA system in a 1:2 molar ratio. This is due to the presence of hydrogen bonds between the carboxyl group from the NA molecule and the bromine atom from the TBAB molecule. Other eutectic mixtures are most likely the solutions of TBAB in NA, in which hydrogen bonds predominate between acid molecules.
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Project description:A rapid, transition metal-free, high-yielding, tetrabutylammonium bromide-promoted method of N-arylation is reported within. The optimized conditions tolerated a wide range of secondary amines and was equally effective with bromo- and chlorobenzene-including substituted aryl halides. The developed method is found to be effective for N-arylation when compared to earlier methods which involve harsh conditions, transition metals, lack of scalability, and long reaction times. Our method utilizes conventional heating only; it is readily scalable; and the products are facile to purify.
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Project description:The removal of NO x (approximately 90% of which is NO) from flue gas is a crucial process for clean power generation from coal combustion. Oxidation of NO to NO2 followed by NO2 absorption using sorbents is considered to be a promising technology alternative to selective catalytic reduction (SCR). This study investigated the absorption of NO2 in flue gas by ethylene glycol (EG)-tetrabutylammonium bromide (TBAB) deep eutectic solvents (DESs) under a range of experimental conditions. The effects of experimental conditions including molar ratio of EG to TBAB, operating temperature, residence time, and the O2 and steam partial pressure in the flue gas on the denitrification performance of EG-TBAB DESs were systematically analyzed. The concentrations of NO2 in the inlet and outlet were evaluated using a flue gas analyzer. The chemical structure changes of DESs after denitrification were characterized using Fourier transform infrared (FT-IR) spectroscopy. The obtained analysis signified that maximum denitrification efficiency and capacity were achieved at a EG/TBAB molar ratio of 5:1, 50 °C, and 6 s residence time. EG-TBAB DESs were able to maintain a stable denitrification performance after five absorption-desorption cycles. The results of quantum chemical calculation and 1H NMR spectra of EG-TBAB DES show that bromide anions in the EG-TBAB DES maintained strong interactions with NO2 via hydrogen bonding, leading to increased NO2 adsorption. The presence of O2 and steam in the flue gas improved the absorption of NO2 in EG-TBAB DESs due to chemical reactions and formation of nitrate.
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Project description:Ozone was injected into a coal-water suspension, and an HRTEM test was carried out on the separated oxidation products. The results show that from the perspective of visualization the macromolecular network structure of coal contains a large number of graphite-like structures. However, the chemical reaction mechanism between the coal surface and O3 is not clear, and the microscopic formation mechanism of oxygen-containing functional groups in carbon quantum dots has not been explained. As a result, the reaction process between O3 and methylene on the coal surface was studied by the DFT method. We found that OH• generated by O3 in water can oxidize two adjacent carbon atoms in methylene into double bonds (C=C), and finally, aldehydes and carboxylic acids were generated. By calculation of thermodynamic parameters ΔG and ΔH, it is found that all reactions are spontaneous exothermic processes. The above chemical reaction is based on the physical adsorption of OH• with Ar-(CH2)6-Ar and O3 with Ar-CH2-CH=CH-(CH2)3-Ar. The calculated adsorption energies of the two systems are -9.41 and -12.55 kcal/mol, respectively. Then, the charge transfer and atomic orbital interaction before and after adsorption are analyzed from the perspectives of Mulliken charge, density of states, deformation density, and total charge density. The results show that the electrostatic attraction is the main driving force of adsorption. The ether bond (C-O-C) in coal is finally oxidized to an ester group (RCOOR'), the hydroxyl group (CH2-CH-OH) on the aliphatic chain is oxidized to a carbonyl group (CH2-C=O), and the benzene with two OH• forms phenol hydroxyl and one molecule of water. Finally, the coal and the corresponding coal-based carbon quantum dots were investigated by infrared spectroscopy; the difference in functional groups before and after oxidation was clarified, and the result was in good agreement with the simulation.
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Project description:Methanesulfinic acid (MSIA) is an important intermediate in the oxidation of dimethyl sulfide (DMS) in the marine boundary layer. The oxidation of MSIA by ozone in the gas phase to form methanesulfonic acid (MSA) was investigated using theoretical calculations in this paper. Three pathways can be found for the reaction of MSIA with ozone. The highest energy barrier is 13.02?kcal?mol-1 in the most favorable pathway. By comparing the reaction rate of MSIA?+?O3 with that of MSIA?+?OH, it can be concluded that the oxidation of MSIA by O3 to form MSA is of minor significance relative to its oxidation by OH radical in the gas phase. This study can provide some information for the theoretical and experimental studies in the significantly heterogeneous and aqueous-phase oxidation of MSIA by O3.
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Project description:This study used two kinetic mechanisms to evaluate the oxidation processes of NO and SO2 by ozone. The performance of the two models was assessed by comparisons with experimental results from previous studies. The first kinetic mechanism was a combined model developed by the author that consisted of 50 species and 172 reactions. The second mechanism consisted of 23 species and 63 reactions. Simulation results of both of the two models show under predictions compared with experimental data. The results showed that the optimized reaction temperature for NO with O3 ranged from 100~200 °C. At higher temperatures, O3 decomposed to O2 and O, which resulted in a decrease of the NO conversion rate. When the mole ratio of O3/NO was greater than 1, products with a higher oxidation state (such as NO3, N2O5) were formed. The reactions between O3 and SO2 were weak; as such, it was difficult for O3 to oxidize SO2.
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