Radical Chain Reaction Research Articles

Photocatalytic fuel cell assisted by Fenton-like reaction for p-Chloronitrobenzen degradation and electricity production through S-scheme heterojunction C3N5 modified TNAs photoanode: Performance, DFT calculation and mechanism

Photocatalytic fuel cell (PFC) is a promising technology to recover usable energy from wastewater through the degradation of pollutants, whereas the complex preparation procedures and high photogenerated carrier recombination efficiency of photoanode remains an urgent challenge to improve the PFC performance. Herein, PFC with S-scheme heterojunction C3N5/TNAs photoanode assisted by Fenton-like reaction (C3N5/TNAs-PFC-Fenton) system was built for p-Chloronitrobenzene degradation and electricity production. The working function confirmed the band bending of C3N5 and TNAs, and density functional theory calculations indicated the formation of internal electric field at heterojunction interface of C3N5 and TNAs, which promoted visible-light absorption capacity and charge transfer property of C3N5/TNAs photoanode. The incorporation of Fenton-like reaction into C3N5/TNAs-PFC-Fenton system could effectively enhance p-Chloronitrobenzene degradation and electricity production by participating in free radical chain reaction and stimulating electron transfer. The radical trapping experiments confirmed that •OH and photogenerated electron were main reactive species, and photogenerated hole, •O2− and 1O2 were also participated in p-Chloronitrobenzene degradation. The p-Chloronitrobenzene degradation pathway was interpreted and the overall toxicity of p-Chloronitrobenzene was relieved after treatment in C3N5/TNAs-PFC-Fenton system. The C3N5/TNAs-PFC-Fenton system exhibited fine universality for degradation of organic pollutants and electricity production.

Interrupted Homolytic Substitution Enables Organoboron Compounds to Inhibit Radical Chain Reactions Rather than Initiate Them.

The reactions of organoboranes with peroxyl radicals are key to their use as radical initiators for a vast array of radical chain reactions, particularly at low temperatures where high stereoselectivity or regioselectivity is desired. Whereas these reactions generally proceed via concerted homolytic substitution (SH2) mechanisms, organoboranes that bear groups that can stabilize tetracoordinate boron radical "ate" complexes (e.g., catecholboranes) undergo this reaction via a stepwise addition/fragmentation sequence and serve as useful stoichiometric alkyl radical precursors. Here we show that arylboronic esters and amides derived from catecholborane and diaminonaphthaleneborane, respectively, are potent radical-trapping antioxidants (RTAs). Mechanistic studies reveal that this is because the radical "ate" complexes derived from peroxyl radical addition to boron are sufficiently persistent to trap another radical in an interrupted SH2 reaction. Remarkably, the reactivity of these organoboranes as inhibitors of autoxidation was shown to translate from simple hydrocarbons to the phospholipids of biological membranes such that they can inhibit ferroptosis, the cell death modality driven by lipid autoxidation and relevant in neurodegeneration and other major pathologies. The unique mechanism of these organoboranes is one of only a handful of RTA mechanisms that are not based on H-atom transfer processes and provide a new dimension to boron chemistry and its applications.

Insight into the pyrolysis mechanism of α-O-4 linked lignin: The role of bimolecular interactions and substituents

Pyrolysis can convert lignin into various high-value phenolic derivatives, whereas the pyrolysis mechanism of lignin, particularly the α-O-4 linked lignin, has not been clearly revealed. Herein, unsubstituted α-O-4 lignin dimer benzyl phenyl ether (BPE) and Cα-substituted α-CH2OH-BPE, α-(CH2)2OH-BPE and α-CHOHCH2OH-BPE were employed to study the radical and concerted mechanisms of α-O-4 type lignin pyrolysis by density functional theory (DFT) calculation and electronic structure analysis. A pyrolysis system was constructed to carefully consider unimolecular and bimolecular reactions, and the influence of substituent groups was investigated. The results indicate that unsubstituted α-O-4 structure can only undergo unimolecular Cα–O homolysis without hydrogen transfer, while various substituents provide more hydrogen sites, leading to the occurrence of radical chain reactions and concerted reactions. Cβ–dehydrogenated radicals derived from substituted α-O-4 dimers can be easily generated by intermolecular Cβ–hydrogen abstraction, which tends to break the Cα–O bond. Similarly, hydroxyl-assisted hydrogen transfer (AHT) can promote Cα–O cleavage by inducing Cβ/Cγ–hydrogen exchange of substituted hydroxy groups. Comprehensively, both radical hydrogen abstraction and concerted hydroxyl-AHT interactions have positive effects on the Cα–O decomposition of α-O-4 linkage. This study provides a more reasonable explanation for the initial decomposition of α-O-4 linked lignin and the preliminary generation of phenolic hydroxy and phenoxy radical derivatives.

Firefighting Gel Polymer Electrolyte for Non-Flammable Li-Ion Batteries Based on Extremely Low Amount of a Cross-Linkable Polymer

Safety issues of lithium-ion batteries(LIBs) have caught a priority of concerns as the electric vehicle(EV) market expands dramatically and requires higher energy densities. To be free from a variety of unpredictable situations and environments triggering such a safety issue, materials that provide a mechanism to control the factors causing fire and explosion are required to be involved in LIB cells.In this work, we present a gel polymer electrolyte(GPE) characterized by nonflammability and fire-extinguishing capability by radical scavenging(Rs). This GPE was realized within battery cells by in situ crosslinking a small amount of a cross-linkable fluoro-functionalized cyanoethyl polyvinyl alcohol(F7) in conventional carbonate electrolytes having LiPF6. The cyanoethyl functional groups(-CN) is responsible for gelation by cross-linking while the fluorine-containing moiety terminated radical chain reactions triggering thermal runaway by Rs. The strong interaction between the polymer and solvent molecules restricted solvent volatility. The tiny solid content at 2 wt. % in GPE guaranteed a liquid-level ionic conductivity at 9 mS/cm, disallowing battery performances to be sacrificed. Formation of the LiF-dominant solid-electrolyte-interphase(SEI) layer on anodes was encouraged by the fluoro-moiety of F7.In previous research of our group, PVA-CN was used as cross-linkable polymer for enhancement of mechanical property with additional metal-chelating functional group. Hydroxy group of PVA-CN is useful to modify the functional group by DCC coupling mechanism. Herein, as same as previous modification, the Heptafluorobutyric acid(HFB) was used for non-flammability and battery performance. F7 was expected to not only increase thermal stability but also scavenge the radicals. In addition, LiF-rich SEI layers would be made by fluorine groups.First, GPE increase its thermal stability by strong interaction between cross-linked polymer matrix and organic solvents. The binding energy of ethylene carbonate (EC) and hydrogen of cyanoethyl side chain was 0.4 eV which is stronger compared with general hydrogen bond(0.2 eV). Therefore, the flammable gas generation was suppressed by strong interaction between solvents and polymer matrix.In addition, the flash point demonstrated the strong interaction in GPE. The flash point of GPE which contained different polymer contents was decreased as the ratio of polymer content was increased. The composition of the atmosphere in the devices changed into more flammable because of the higher ratio of EMC gas in the atmosphere within enough time to equilibrate. In other words, EC forms a greater number of strong interactions with the polymer matrix while the polymer contents increased. The SET test of 2 wt.% PVA-CN-based GPE(G2)(3.36 s/g) and 5 wt.% PVA-CN-based GPE(G5)(0 s/g) proved that higher contents of PVA-CN in GPE ensure the non-flammability.Second, to overcome the poor electrochemical ability of G5, Rs functionalized F7 was used instead of PVA-CN. Unlike G2, only with 2 wt. % of F7 guaranteed the 0 s/g of SET. Non-flammability of 2 wt.% F7-based GPE(FG2) is due to the fluorine moiety scavenge the O• or H•. In the nail penetration test, only the FG2 was not exploded and maintained charged voltage while the nail penetrates the whole pouch cell vertically because of its elasticity.The Rs capability was demonstrated by cyclic voltammetry(CV) with 2,2’-azobisisobutyronitrile(AIBN) and alpha-tocopherol(α-TOH). After α-TOH react with AIBN radicals at the 70 ℃, the oxidation current decreased because of consumption of α-TOH. The Rs capability was calculated by ratio of current retention of α-TOH oxidation current with a same amount of among scavenger additives. The Rs capability of F7 was 214%.Lastly, our findings suggest sufficient non-flammability without battery performances degradation. The capacity retention of FG2 was higher than LE at the 300th Cycles. This is because the fluorine moiety contributed to make LiF-rich SEI layers. The rigid SEI layers and GPE suppressed volume expansion of graphite. Also, the capacity fade was not observed in FG2 with higher current density. The reason for great rate capability is higher lithium-ion conductivity which is a multiplication of ionic conductivity and lithium-ion transference number(tLi+). FG2has 4.82 of lithium-ion conductivity, while 3.63 in LE. Therefore, the mass transfer resistance was not large on the electrode surface due to the higher lithium-ion mobility in FG2.In this work, the non-flammability and battery performance were successfully demonstrated by thermal stability and Rs capability without any battery performances degradation. The thermal stability was enhanced by strong intermolecular forces between polymer chain and polar organic solvents. The radical chain reaction was terminated by fluorine moiety of GPEs matrix. The capacity retention of FG2 was outstanding compared with LE. Therefore, due to the FG2, the battery will be able to ensure non-flammability without degradation of performance. Figure 1

Using Mechanochemistry to Activate Commodity Plastics as Initiators for Radical Chain Reactions of Small Organic Molecules.

Radical initiators such as azo compounds and organic peroxides have been widely used to facilitate numerous transformations of free radicals, which enable the efficient synthesis of structurally complex molecules, natural products, polymers, and functional materials. However, these high-energy reagents are potentially explosive and thus often require special precautions or delicate operating conditions. We postulated that a more convenient and safer alternative for radical chain initiation could be developed by mechanical activation of thermodynamically stable covalent bonds. Here, we show that commodity plastics such as polyethylene and poly(vinyl acetate) are capable of acting as efficient initiators for radical chain reactions under solvent-free mechanochemical conditions. In this approach, polymeric mechanoradicals, which are generated by homolytic cleavage of the polymer chains in response to the applied mechanical energy provided by ball milling, react with tris(trimethylsilyl)silane to initiate radical chain dehalogenation of organic halides. Preliminary calculations support our proposed force-induced radical chain mechanism.

Enhancing lipid peroxidation via radical chain transfer reaction for MRI guided and effective cancer therapy in mice

Lipid peroxidation (LPO), the process of membrane lipid oxidation, is a potential new form of cell death for cancer treatment. However, the radical chain reaction involved in LPO is comprised of the initiation, propagation (the slowest step), and termination stages, limiting its effectiveness in vivo. To address this limitation, we introduce the radical chain transfer reaction into the LPO process to target the propagation step and overcome the sluggish rate of lipid peroxidation, thereby promoting endogenous lipid peroxidation and enhancing therapeutic outcomes. Firstly, radical chain transfer agent (CTA-1)/Fe nanoparticles (CTA-Fe NPs-1) was synthesized. Notably, CTA-1 convert low activity peroxyl radicals (ROO·) into high activity alkoxyl radicals (RO·), creating the cycle of free radical oxidation and increasing the propagation of lipid peroxidation. Additionally, CTA-1/Fe ions enhance reactive oxygen species (ROS) generation, consume glutathione (GSH), and thereby inactivate GPX-4, promoting the initiation stage and reducing termination of free radical reaction. CTA-Fe NPs-1 induce a higher level of peroxidation of polyunsaturated fatty acids in lipid membranes, leading to highly effective treatment in cancer cells. In addition, CTA-Fe NPs-1 could be enriched in tumors inducing potent tumor inhibition and exhibit activatable T1-MRI contrast of magnetic resonance imaging (MRI). In summary, CTA-Fe NPs-1 can enhance intracellular lipid peroxidation by accelerating initiation, propagation, and inhibiting termination step, promoting the cycle of free radical reaction, resulting in effective anticancer outcomes in tumor-bearing mice.

From Theory to Practice: Leveraging Chemical Principles To Improve the Performance of Peroxydisulfate-Based In Situ Chemical Oxidation of Organic Contaminants.

In situ chemical oxidation (ISCO) using peroxydisulfate has become more popular in the remediation of soils and shallow groundwater contaminated with organic chemicals. Researchers have studied the chemistry of peroxydisulfate and the oxidative species produced upon its decomposition (i.e., sulfate radical and hydroxyl radical) for over five decades, describing reaction kinetics, mechanisms, and product formation in great detail. However, if this information is to be useful to practitioners seeking to optimize the use of peroxydisulfate in the remediation of hazardous waste sites, the relevant conditions of high oxidant concentrations and the presence of minerals and solutes that affect radical chain reactions must be considered. The objectives of this Review are to provide insights into the chemistry of peroxydisulfate-based ISCO that can enable more efficient operation of these systems and to identify research needed to improve understanding of system performance. By gaining a deeper understanding of the underlying chemistry of these complex systems, it may be possible to improve the design and operation of peroxydisulfate-based ISCO remediation systems.

Evaluation of the photosensitizer activity of hydrophobic phosphorus(V)porphyrins using the absorption spectral change of 1-benzyl-1,4-dihydronicotinamide

Under visible light irradiation, water-insoluble P(V)porphyrins oxidized 1-benzyl-1,4-dihydronicotinamide (BNADH), a model compound for nicotinamide adenine dinucleotide, and diminished the typical absorption of BNADH at around 340 nm. A singlet oxygen quencher, sodium azide, partially inhibited photosensitized BNADH oxidation. This BNADH oxidation photosensitized by P(V)porphyrins in the presence of sodium azide can be explained by electron transfer oxidation from BNADH to the photoexcited P(V)porphyrins. The quantum yields of BNADH oxidation via electron transfer by these P(V)porphyrins were larger than those of a singlet oxygen mechanism. Redox potential measurements supported the electron transfer mechanism from a thermodynamic point of view, and fluorescence lifetime measurement also suggests this mechanism. The process of this electron transfer oxidation involves the radical formation of BNADH and the further reaction of this radical to the oxidized form (cationic form of BNADH). Analysis of the quantum yields of BNADH photooxidation by P(V)porphyrins suggests that the photoinduced electron transfer from BNADH to photoexcited P(V)porphyrins triggers the radical chain reaction of BNADH oxidation. The electron transfer rate coefficient and this efficiency were increased with an increase in the Gibbs energy of electron transfer from tryptophan to photoexcited P(V)porphyrins (−ΔG). However, the BNADH oxidation quantum yield via electron transfer decreased with an increase in the -ΔG of electron transfer. These results suggest that reverse electron transfer inhibits the decomposition of BNAD radicals. This assay using BNADH can be used to evaluate the photosensitizer activity of water-insoluble compounds. These P(V)porphyrins may be used as photosensitizers for photodynamic therapy in a relatively hydrophobic environment in cancer tissues.

Study on the catalysis of copper-based compounds on coal spontaneous combustion and its mechanism

ABSTRACTTo study the effect of the copper element in coal on the spontaneous combustion process of coal, corresponding copper-containing compounds were added to the coal-based on their occurrence state, and thermodynamic experiments and in-situ diffuse reflectance infrared spectroscopy experiments were conducted. Thermodynamic oxidation experiments have shown that the catalytic effects of Cu (NO3)2, CuCl2, CuCl, and Cu2O on three types of coal with different degrees of metamorphism are mainly reflected in the accelerated oxidation stage. After adding copper-containing compounds, the ignition temperature of coal decreased by 22.1°C to 134.4°C, the heat release increased by 1.33 to 3.19 times, and the CO emission and oxygen consumption rate also increased. CuCl has the greatest impact on the ignition point temperature of coal and increases the oxygen consumption rates of DNH and TS by 2.32 and 1.51 times that of raw coal. CuCl2 has the strongest catalytic effect on coal oxidation heat release. Through in-situ diffuse reflectance infrared spectroscopy experiments, it was found that the reaction rate of fatty hydrocarbons in the oxidation process of three types of coal with the addition of copper-containing compounds increased to 1.3–3 times that of raw coal, and the oxidation rate of oxygen-containing functional groups also significantly increased, while the cracking temperature of aromatic structures significantly decreased. This is because copper ions, as strong free radicals, induce free radical chain reactions in coal and exhibit a strong promoting effect on the coal oxygen reaction process.

Explosion suppression characteristics of modified ABC powder driven by argon/CO2

This paper changed ABC powder and performed a comparison on the suppression of methane explosions between pure modified powder under various operating circumstances and cold aerosols induced by various inert gases (argon, CO2). The results show that the maximum explosion pressure and flame velocity greatly decrease when inert gases act as catalytic gases. Different inert catalytic gases have various inhibitory effects on cold aerosols. Argon can delay the arrival of explosion overpressure. CO2 gas can produce bidirectional inhibitory effects from inerting and free radical chain reactions. It not only delays the occurrence of explosion overpressure, but also enhances explosion suppression ability. The most effective inhibitor is the cold aerosol, which contains 0.06 g/L of modified powder and 24% CO2 gas. Finally, under the influence of inert gases (argon, CO2), the modified ABC powder creates a cold aerosol that can more effectively suppress methane explosions.

Dry water consisting of nano SiO2 modified by fluorinated surfactant: Applied to AlH3 explosion suppression

AlH3 has a high explosion risk due to rapid hydrogen evolution, and explosion suppression is necessary to reduce explosion hazard. Herein, we apply a common fire extinguishing agent, fluorinated surfactant, to suppress hydrogen in AlH3. This stable composite suppressant has a structure resembling dry water, a dilute aqueous solution of FS-50 encapsulated by fumed phase SiO2, which not only improves suppression effect but also significantly reduces the damage of fluorine to the environment. Fluorinated intermediate radicals F, CF, CF3, CHF, CHF2, etc. produced by decomposition of FS-50 interrupt the chain reaction of flame radicals H, O, OH to produce (-CH2-CF2-)n and stable product HF. Additionally, the outflow of fluorinated compounds mixes with water and SiO2 to form a cladding layer, which prevents heat propagating from the reaction zone to preheating zone. Our work will pave the way for the widespread and safe application of light metal hydrogen storage materials.

Photocatalyzed Perfluoroalkylation of Endoglycals.

The visible light-induced perfluoroalkyl (RF) radical reactions on peracetylglycals derived from hexoses and pentoses (galactal, glucal, arabinal, and xylal derivatives) were investigated. Various photocatalysts and perfluoroalkyl iodides (RF-I) were employed as sources of RF radicals with LEDs as the irradiation source. Particularly noteworthy was the use of an Iridium photocatalyst, Ir[dF(CF3)ppy]2(dtbpy))PF6, which yielded two distinct product types when applied to glucal. On the one hand, the 2-RF-substituted glucal was formed, a trend observed even when utilizing organic dyes as photocatalysts. On the other hand, the unexpected addition product, namely the 1-RF-2-iodo-α-manno-configured C-glycosyl derivative, was also obtained, as a result of a highly regioselective addition reaction of the RF moiety into the anomeric carbon, followed by attachment of the iodine atom on C-2 in axial disposition. This result contrasted with other radical reactions carried out on 2-unsubstituted glycals, where the incipient radical adds to C-2, generating a stabilized 1-glycosyl radical. The photocatalyzed radical perfluoroalkylations of peracetyl glycals derived from galactose, arabinose, and xylose all afforded the 2-RF-substituted glycals in good yields as a result of the expected vinylic substitution reaction. Mechanistic studies revealed that the 1-RF-2-iodo-α-manno-configured C-glycosyl derivatives arise from a radical chain reaction, whereas the 2-RF-substituted glycals proceed from inefficient chain processes.

Effect of alkyl‐chain unsaturation on the antioxidant potential of chlorogenic acid derivatives in food and biological systems

SummaryChlorogenic acid (CGA) was modified using acyl chlorides with different levels of unsaturation (C18:0–C18:3) to enhance the lipophilicity and promote its application. The antioxidant activity of CGA derivatives in food and biological models was evaluated. All CGA derivatives had significantly greater antioxidative activity than CGA in fish oil and β‐carotene/linoleic acid emulsions (P < 0.05), but there was no linear relationship between antioxidative activity and unsaturation. The effectiveness of CGA‐C18:0 was significantly greater than that of CGA in scavenging H2O2 and reducing copper‐induced human low‐density lipoprotein (LDL) oxidation (P < 0.05). Furthermore, the H2O2 scavenging activity, inhibitions of copper‐induced human LDL oxidation and hydroxyl or peroxyl radical‐induced DNA oxidation were all linearly related to the unsaturation of the alkyl chains, mainly with the free radical chain reactions of the unsaturated bonds. Our findings showed that CGA derivatives could potentially be used as antioxidants in food and biological systems.

The Deposition of Isolated Fe(3+) Species in Mesoporous Silicon for Oxidation of Cyclohexane

AbstractThe balance of activity and selectivity in liquid alkane oxidation is challenging for the design of supported Fe catalysts. When Fe species leach to the solvent, uncontrolled free radical chain reactions happen. Herein, isolated Fe(3+) species were constructed by forming a strong Fe−O−Si bond for the selective oxidation of cyclohexane to cyclohexanone by H2O2. Compared to the supported FeOx clusters, the strong Fe−O−Si bond between isolated Fe(3+) species and SiO2 prevents the leaching of Fe in strong oxidation (H2O2) reaction conditions and dominates the non‐free radical mechanism. The turnover frequency over 10FeOx/SBA‐15 reached 15.2 h−1, higher than for reported Fe‐based catalysts. High selectivity of cyclohexanone is maintained at different conversions. Moreover, the (SiO)xFe3+(OH)3‐x−OOH active species were detected by Raman and FTIR and are generated from the oxidation of isolated Fe species. The strong Fe−O−Si bond and non‐free‐radical mechanism by (SiO)xFe3+(OH)3‐x−OOH active species induce high activity and selectivity for the oxidation of many other alkanes.

Characterization of elementary reactions inducing coal spontaneous combustion

Twenty-five reactions involving R⋅, ⋅OH, ⋅OOH, R–CH2OH, R–COOH, R–CHO, R–CH3, ROO⋅, R–CH2O⋅, R–C(=O)–O⋅, and R–Ċ=O reactive tissues were studied by computational chemistry to reveal the microscopic mechanism of coal spontaneous combustion (CSC). Results showed that R⋅ chemisorbed oxygen to form ROO⋅. Then, ROO⋅ captured the H atom from alkane or self-structure to generate ⋅OH and R⋅. Accordingly, a cyclic reaction centered on R⋅ was formed. In addition, the reaction of the reactive groups (R–CH3, R–CH2OH, R–COOH and R–CHO) with hydroxyl radicals, which requires low activation energy and is accompanied by exotherm, is the main pathway to produce R⋅, R–CH2O⋅, R–C(=O)–O⋅, and R–Ċ=O. Subsequently, condensation reactions occurred between ⋅OH and R⋅, ⋅OOH and R–Ċ–OH, R–CO⋅ and R⋅, and R–C(=O)–O⋅ and R⋅, which can spontaneously proceed and release large amounts of heat, accelerating the self-heating of the coal. O2 can directly capture the H atom on the alkyl group to generate R⋅ and ⋅OOH as the coal body temperature reaches 30 °C–70 °C.⋅OOH can also capture the H atoms on the alkyl group to generate R⋅. Consequently, another small cycle of radical reactions centered on R⋅ is formed. Meanwhile, the reactions of ⋅OOH and R⋅ with R–CH2OH, R–COOH, and R–CHO provide two additional pathways to generate R–CH2O⋅, R–C(=O)–O⋅, and R–Ċ=O. Finally, the decomposition reactions of R–CH2O⋅, R–C(=O)–O⋅ and R–Ċ=O are the main pathways to produce R⋅, CO2, and CO, respectively. Accordingly, a macrocycle chain reaction of free radicals is formed. Therefore, removal of ⋅OH, R⋅, ⋅OOH, and ROO⋅ is the key to break the chain reaction of the CSC cycle.

Experimental and numerical simulation study of hydrogen explosion suppression by a small amount of ethylene

Hydrogen safety is the foundation of hydrogen energy industry, but there is presently a shortage of high-efficiency safety protection technologies for hydrogen. Through a combination of experiment and simulation methods, this paper reveals the effective performance of ethylene in suppressing the hydrogen explosion behaviors in a 14 L closed spherical vessel at normal temperature and pressure. The experimental and simulation results show that a small amount of ethylene can increase the hydrogen generation path in the lean hydrogen chain reaction, thus enhancing the concentration of active free radicals and causing flame instability, which ultimately leads to an increase in explosion overpressure and laminar burning velocity. But on the whole, with the increase in ethylene volume fraction, the explosion parameters show a monotonically decreasing trend. This is because the addition of ethylene makes the hydrogen-oxygen chain reaction gradually transition to the inactive free radical chain reaction, resulting in the conversion of the active free radical to the inactive free radical, and the chain reaction rate is weakened. Finally, the explosion cannot occur. This result provides a novel idea for the research of new and efficient hydrogen explosion suppression materials.

Simulation analysis of soot formation and laminar combustion characteristics of 2,5-dimethylfuran/air at different initial pressures and temperatures

In this research, we studied the soot formation and laminar combustion characteristics of 2,5-dimethylfuran (25DMF) at different initial temperatures and initial pressures, and conducted reactive force field molecular dynamics (ReaxFF MD) simulation and dynamical simulation method with a one-dimensional laminar combustion model through CHEMKIN's PREMIXED Code. The full process of soot formation during 25DMF combustion was revealed by ReaxFF MD simulation. There are three stages from the formation of the initial ring, the growth of polycyclic aromatic hydrocarbons (PAHs) and the formation and growth of the initial soot. The growth mechanism of polycyclic aromatic hydrocarbons was mainly divided into 4 types, which were hydrogen-abstraction-C2H2-addition (HACA), carbon-addition-hydrogen-migration (CAHM), clustering of hydrocarbons by radical-chain reactions (CHRCR) mechanism and internal ring formation. For the dynamical model of 25DMF combustion, the initial temperatures (Tu) were set to 298 K, 358 K, 393 K and 423 K, and the initial pressures (pu) were set to 1 atm, 3 atm, 5 atm and 10 atm. The results showed that the laminar burning velocities (LBVs) increased along with the increase of the initial temperature. The LBVs decreased with the increase of initial pressure. Both the increase of the initial temperature and pressure led to a decrease in flame thickness. Studies on soot precursors showed that C2H2, i-C4H5, C4H2, and C6H6 shift upstream in peak molar fraction with increasing initial pressure. C4H2 and C6H6 moved downstream first, then upstream and finally downstream with the increase of initial temperature. C2H2 and i-C4H5 shifted upstream and then downstream with increasing initial temperature.

Facile Borylation of Alkenes, Alkynes, Imines, Arenes and Heteroarenes with N-Heterocyclic Carbene-Boranes and a Heterogeneous Semiconductor Photocatalyst.

Although the development of radical chain and photocatalytic borylation reactions using N-heterocyclic carbene (NHC)-borane as boron source is remarkable, the persistent problems, including the use of hazardous and high-energy radical initiators or the recyclability and photostability issues of soluble homogeneous photocatalysts, still leave great room for further development in a sustainable manner. Herein, we report a conceptually different approach toward highly functionalized organoborane synthesis by using recoverable ultrathin cadmium sulfide (CdS) nanosheets as a heterogeneous photocatalyst, and a general and mild borylation platform that enables regioselective borylation of a wide variety of alkenes (arylethenes, trifluoromethylalkenes, α,β-unsaturated carbonyl compounds and nitriles), alkynes, imines and electron-poor aromatic rings with NHC-borane as boryl radical precursor. Mechanistic studies and density functional theory (DFT) calculations reveal that both photogenerated electrons and holes on the CdS fully perform their own roles, thereby resulting in enhancement of photocatalytic activity and stability of CdS.

Facile Borylation of Alkenes, Alkynes, Imines, Arenes and Heteroarenes with N‐Heterocyclic Carbene‐Boranes and a Heterogeneous Semiconductor Photocatalyst

AbstractAlthough the development of radical chain and photocatalytic borylation reactions using N‐heterocyclic carbene (NHC)‐borane as boron source is remarkable, the persistent problems, including the use of hazardous and high‐energy radical initiators or the recyclability and photostability issues of soluble homogeneous photocatalysts, still leave great room for further development in a sustainable manner. Herein, we report a conceptually different approach toward highly functionalized organoborane synthesis by using recoverable ultrathin cadmium sulfide (CdS) nanosheets as a heterogeneous photocatalyst, and a general and mild borylation platform that enables regioselective borylation of a wide variety of alkenes (arylethenes, trifluoromethylalkenes, α,β‐unsaturated carbonyl compounds and nitriles), alkynes, imines and electron‐poor aromatic rings with NHC‐borane as boryl radical precursor. Mechanistic studies and density functional theory (DFT) calculations reveal that both photogenerated electrons and holes on the CdS fully perform their own roles, thereby resulting in enhancement of photocatalytic activity and stability of CdS.

Study on the microcosmic mechanism of inhibition of coal spontaneous combustion by antioxidant diphenylamine

Diphenylamine has been applied to suppress coal spontaneous combustion with good results, but its microscopic reaction mechanism is not clear. In this paper, the free radical reaction process of coal spontaneous combustion is calculated more systematically, and the quantum chemical method is applied to analyze in detail the process of diphenylamine depletion of reactive free radicals in coal from three perspectives: hydrogen atom transfer, direct radical capture, and regeneration cycle chain. By destroying the molecular structure of coal to generate free radicals as the initial condition of coal spontaneous combustion, the oxidation process of the free radical chain reaction was analyzed, the thermodynamic data of all reactions were calculated, the microscopic mechanism of free radical capture by diphenylamine was revealed, and the transition state structure model of the reaction process was given. The active sites of each reactant were determined by quantitative molecular surface analysis, the spontaneity of the reaction was measured by the free energy change, and the interaction relationship between different conformations was graphically represented by applying the IRI (interaction region indicator) method. The results show that most of the free radical reactions during the spontaneous combustion of coal are exothermic, and they provide heat for the spontaneous combustion of coal, which can react directly with oxygen when accumulated to a certain temperature. Diphenylamine can break the N-H bond, allowing hydroxyl radicals and carbon radicals to obtain hydrogen atoms to form stable compounds, and the generated diphenylamine radicals can reduce the content of free radicals in coal by direct capture. In addition, the process of diphenylamine inhibition of coal spontaneous combustion has a circular regeneration chain, which can indeed effectively reduce the content of reactive radicals and inhibit the spontaneous combustion of coal, which is reflected in the macroscopic level of reducing the generation of coal spontaneous combustion indicator gas, which is consistent with the experimental results.