H2O Reaction Research Articles

CS@Cu2O and magnetic Fe3O4@SiO2-pAMBA-CS-Cu2O as heterogeneous catalysts for CuAAC click reaction

The recovery of agricultural and food wastes are one of the main areas of current research for optimal biowaste management to reduce greenhouse gas (GHG) emissions that are generated when it is not properly treated. Corn silk (CS) as biowaste from the agricultural sector is a rich source of natural compounds especially polysaccharides. We present here a chemical activation method to convert CS to values added heterogeneous catalyst for the synthesis of triazoles compounds via copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction. For this purpose, cuprous oxide coated CS ([email protected]2O) and multifunctional Fe3O4@SiO2–para-aminomethyl benzoic acid–CS–Cu2O composite (denoted as Fe3O4@SiO2‐pAMBA-CS‐Cu2O) were fabricated. Different analytical techniques have been used to describe the size, crystal structure, elemental composition and other physical properties of the fabricated catalysts. These heterogeneous catalysts showed excellent catalytic activities for the synthesis of 1,4-disubstituted-1,2,3-triazoles via click reaction in H2O at 70 °C under base and external-reductant-free conditions. The magnetic properties of the catalyst allowed easy separation after reaction by simply applying an external magnet. Other advantages of this work are the recyclability of the catalyst, the absence of reducing agent and base, besides utilisation of bio wastes for the production of heterogeneous catalyst.

Reaction between propionaldehyde and hydroxyperoxy radical in the atmosphere: A reaction route for the sink of propionaldehyde and the formation of formic acid

Understanding the chemical transformations of volatile organic compounds is particularly important for atmospheric modeling and elucidating their effects on atmospheric environment, where the key parameters are reaction mechanism and kinetics. Here, we report that the reaction mechanism and kinetics of propionaldehyde with hydroxyperoxy radical by using quantum chemical methods and reaction rate theory. In particular, we use our very recently developed dual-level strategy to obtain the high-pressure limit rate constants of the reaction of propionaldehyde (CH3CH2CHO) with hydroxyperoxy radical (HO2). We find that the enthalpy of activation at 0 K is only −1.86 kcal/mol in the CH3CH2CHO + HO2 reaction. The present results also uncover that the CH3CH2CHO + HO2 reaction depends on temperature and pressure and its high-pressure limit rate constant has negative temperature dependency with the value of 7.76 × 10−13 to 3.06 × 10−14 cm3 molecules−1 s −1 at 190–350 K. Moreover, the present findings also show that the reaction of propionaldehyde with hydroxyperoxy radical can make great contribution to the sink of propionaldehyde below 260 K and 1 atm when OH concentration is less than 8.4 × 104 molecules cm−3 at night and can not be ignored at 0–10 km altitude. We also find a potential route for the formation of formic acid by the reaction of propionaldehyde with hydroxyperoxy radical.

Two-dimensional ZnO/BlueP van der Waals heterostructure used for visible-light driven water splitting: A first-principles study

Solar driven water splitting for hydrogen generation has been considered as an important method for collecting clean energy. Herein, based on first-principles calculations, we propose that ZnO/BlueP van der Waals heterostructure can realize overall water splitting reaction for hydrogen generation. Strikingly, the band-gap of 1.83 eV is appropriate, and band alignments straddle the water redox potentials, ensuring the occurrence of hydrogenevolutionreaction and oxygen evolution reaction. Charge density distribution and carrier mobility exhibit significant charge separation and transfer. Visible-light response is improved compared with those of the isolated monolayers. Moreover, hydrogenevolutionreaction is actually realized on the ZnO layer, while oxygen evolution reaction is implemented on the BlueP layer. Through the investigation of the adsorption and dissociation reactions of H2O, we observe that two neighboring H*s prefer to combine to form H2 by overcoming a lowered energy barrier of 0.75 eV. Strain effect indicates that the lateral compressive strain of −4% to 0% and the vertical tensile strain of 0% to +6% can effectively tune band-gap and band alignments. The results indicate that ZnO/BlueP vdW heterostructure is probable highly efficient photoelectric material used for visible-light driven water splitting for hydrogen generation.

Study on the mechanical behavior and micro-mechanism of concrete with coal gangue fine and coarse aggregate

Coal gangue is waste rock generated from coal mining, which results in vast land occupation in mines and severe environmental pollution. Owing to the similarity between coal gangue and natural aggregates, concrete preparation from coal gangue has been considered effective for solving gangue problems. In this study, to further improve the on-site utilisation rate of coal gangue, coal gangue was used to replace fine and coarse aggregates for preparing mortar and concrete. The macro and microscopic characteristics of coal gangue mortar (CGM) and coal gangue concrete (CGC) were investigated while considering the effects of coal gangue fine aggregate (CGFA) replacement ratio, curing time, and water-to-cement ratio. To investigate the macro properties, flexural, compressive, and splitting tensile tests were performed. The results show that CGM and CGC with an appropriate CGFA replacement ratio of 25% exhibited optimal performance. Additionally, by replacing all aggregates with CGFAs and coal gangue coarse aggregates, the 28 d compressive strengths of samples W0.5R100 and W0.4R100 were 44.8 and 52.24 MPa, respectively, which satisfied the C30–C50 concrete strength requirements. Moreover, a model is proposed for predicting the splitting tensile strength of the CGC to address the overestimation of existing national standards. For microscopic analysis, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy were conducted to illustrate the hydrated products and micromorphology of CGC under different conditions, as well as to discuss the effect of the mechanism on strength. Based on the micro analysis, the mechanism of CGFAs is summarised as a coal gangue–Ca(OH)2–H2O reaction system: volcanic-activated SiO2 and Al2O3 in CGFAs react with calcium hydroxide (CH) crystals, and more CH is consumed; subsequently, more calcium silicate hydrate gels and ettringite crystals are produced in the secondary hydration reaction, contributing to a denser microstructure and improvement in concrete strength at the late stage. In particular, gismondine is observed as a new hydration product in the reaction of CGC, which differs from that of normal concrete. This study provides a basis for the large-scale utilisation of coal gangue in situ.

Automatic high-pressure H2 generation up to 40 MPa through [formula omitted] enhanced Al–H2O reaction

For the practical application, storage, and transportation of hydrogen energy, compressed high-pressure H2 is generally required, which consumes large amounts of energy. In this research, an automatic high-pressure H2 production system based on the HCO3− enhanced Al–H2O reaction is established, in which, over 40 MPa H2 at 300 °C (25 MPa at 25 °C) is successfully obtained without using any compressing facilities. Energy balance calculation reveals that although this reaction requires a high temperature, it is highly exothermic (145.9 MJ/kg H2). Since heating the reactants to the desired reaction temperature only needs an energy of 55.3 MJ/kg H2, the energy requirement of this reaction can be self-supported. In addition, waste Al-can is further tested for the high-pressure H2 generation to realize a waste material recovery simultaneously, and over 40 MPa H2 at 300 °C can also be obtained with the addition of Na2CO3. This research proposes a new way of automatic high-pressure H2 production from renewable resources, which can promote the practical large-scale hydrogen energy utilization.

A catalyst-free co-reaction system of long-lasting and intensive chemiluminescence applied to the detection of alkalinephosphatase.

A catalyst-free co-reaction luminol-H2O2-K2S2O8 chemiluminescence (CL) system was developed, with long-life and high-intensity emission, and CL emission lasting for 6h. A possible mechanism of persistent and intense emission in this CL system was discussed in the context of CL spectra, cyclic voltammetry, electron spin resonance (ESR), and the effects of radical scavengers on luminol-H2O2-K2S2O8 system. H2O2 and K2S2O8 co-reactants can promote each other to continuously generate corresponding radicals (OH•, 1O2, O2•-, SO4•-) that trigger the CL emission of luminol. H2O2 can also be constantly produced by the reaction of K2S2O8 and H2O to further extend the persistence of this CL system. CL emission can be quenched via ascorbic acid (AA), which can be generated through hydrolysis reaction of L-ascorbic acid 2-phosphate trisodium salt (AAP) and alkaline phosphatase (ALP). Next, a CL-based method was established for the detection of ALP with good linearity from 0.08 to 5 U·L-1 and a limit of detection of 0.049 U·L-1. The proposed method was used to detect ALP in human serum samples.

Computational Study on the Reaction of β-Hydroxyethylperoxy Radical with HO2 and Effects of Water Vapor.

The reaction of β-hydroxyethylperoxy radical (β-HEP) and HO2 with and without water was studied using quantum chemistry and kinetic calculations. The main products are HOCH2CH2OOH and 3O2 for the reaction with and without water, while all other reaction channels can be neglected. The rate coefficients of the reaction follow negative temperature dependence. The pseudo-second-order rate coefficients are 2-4 orders of magnitude smaller for the reaction with saturated water vapor, indicating the negligible contribution of water in this reaction. This is probably also true for other peroxy radicals (except for HO2), indicating that a large part of previous results on the water enhancement of reaction rate coefficients might have overestimated the influence of water.

Super-adiabatic temperature in homogenous ignition of CH4/O2/N2 mixtures

Methane-oxygen burning has promising application in future rocket engines used in low-cost space launch systems. In this study, the phenomenon of super-adiabatic temperature (SAT) in homogenous ignition process of methane-oxygen with and without nitrogen dilution is investigated. Simulations considering detailed chemistry are conducted for homogeneous ignition processes and premixed flames in CH4/O2/N2 mixtures. The objectives are to assess the effects of equivalence ratio, oxygen content in oxidizer, initial temperature and pressure on SAT and to identify the key elementary reactions involved in SAT for methane. It is found that the SAT changes non-monotonically with the equivalence ratio and there exists two regimes for SAT. The contribution of each elementary reaction to the post-ignition temperature decrement is quantified and the key reactions responsible for the occurrence of SAT are determined. It is found that the SAT in the homogenous ignition of CH4/O2/N2 mixtures is mainly caused by the endothermic dissociation reactions of H2O, H2, CO2 after thermal runaway. With the increase of initial temperature and oxygen content and decrease of pressure, the dissociation of H2O, H2 and CO2 becomes stronger and thereby SAT is larger. Moreover, the chemistry involved in the SAT for homogeneous ignition and premixed flames is compared. It is found that the same chemical kinetics is involved in the SAT for homogenous ignition process and premixed flames.

Conductive SnO2-x thin films deposited by thermal ALD with H2O reactant

In this study, SnO2-x films were deposited by a thermal atomic layer deposition (ALD) method with H2O as a reactant. The electrical property of the films was assessed with the intention of applying them as a channel for a back-end-of-line (BEOL) compatible transistor. Under the thermal budget constraint (<450 °C) required for a BEOL transistor, the effect of ALD process parameters and post-annealing conditions on the carrier concentration and mobility of the films was investigated. While the as-deposited films were amorphous, more distinctive recrystallization could be observed with the deposition temperature of 200 °C combined with the annealing ambient of N2. As a result, the mobility of 21.55 cm2/Vs and 3.3 × 1019 cm−3 carrier concentration were achieved with an 18-nm thick n-type SnO2-x film. However, it was also observed the mobility of the N2-annealed SnO2-x decreased by ∼50% of an initial value upon exposure to humidity for 2–3 days. 5-Nm Al2O3 on SnO2-x as a capping layer could prevent the degradation, suggesting the presence of a more conductive path near the surface. This work demonstrates SnO2-x deposited by a thermal ALD can exhibit an excellent electrical property suitable for various electronic devices such as a BEOL compatible transistor.

Deposition of nano-crystalline tungsten carbide powders from gaseous WO2(OH)2

Lower WC grain sizes in the nanometer range have positive effects on the properties of hardmetals (e.g., hardness), but the established production processes of WC are limited to grain sizes of about 150 nm. To produce WC powder with grain sizes in the lower nanometer range, an alternative WC production process based on the chemical vapor transport (CVT) reaction of WO3 and H2O forming gaseous WO2(OH)2 at about 1100 °C, followed by a carburation reaction with H2/CH4-gas mixtures was investigated. The influences of different process parameters such as furnace temperature, humidity and gas flows were investigated to improve the process. With the right set of parameters the produced powder consisted mainly of agglomerated WC grains with a size of about 5 nm. Beside the common hexagonal WC phase, the cubic WC1−x phase was stabilized due to the small crystallite sizes. In addition, a thin layer of amorphous carbon was present on the powder surface due to the catalytic methane decomposition on the WC surface. The amount of oxidic and metallic residues in the product powder was minimized with the parameter optimization and the powder yield was increased up to about 50%. With further optimization of the process parameters and usage of improved flow breakers, the purity and yield of the product powder can be further improved. Since an application in the hardmetal section is not realistic at the moment, applications in the catalysis sector could be considered due to the small grain size and good catalytic activity of the cubic WC1−x phase.

Edge type effect in the gasification mechanism of graphene clusters with H2O and/or CO2: armchair vs. zigzag

Reactions of carbon and oxygen containing molecules, such as O2, NO, H2O and CO2, are ubiquitous on earth and the universe. Through ab initio calculations, we study the reactions of H2O and CO2 with small graphene clusters containing armchair edges, both H- and non-H terminated, and compare with studies of zigzag carbon edges interacting with oxygen-containing molecules. Our results highlight the differences between armchair and zigzag sites and our mechanistic comparisons regarding carbon reactions with H2O and CO2, identify similarities and differences on their reactivity. In the case of H2O, adsorption is favored over armchair sites exhibiting no rotational process and the H2 desorption step is favored over zigzag sites. Regarding the CO2 reaction, chemisorption is favored on zigzag sites. Several adsorption mechanisms lead to the formation of lactone groups as the most stable structures. A specific armchair CO desorption path for stable functional groups exists, agreeing with experimental reports, and thus completing our explanations for this reaction, previously limited to zigzag sites. Finally, the reaction over armchair sites leads to direct formation of pentagonal rings, without an active site deactivation process and with low activation energies. This deeper understanding provides further possibilities for improving the control of carbon-oxygen reactions.

Influence of water molecule on active sites of manganese oxide-based catalysts for ozone decomposition

Developing an efficient approach to decompose ground-level O3 in humidity is crucial for preventing O3 pollution in practical application scenes. In this study, MnOx, CuO, and Cu/MnOx were synthesized to investigate the influence of H2O on the variation of active sites during O3 decomposition. The structural characterizations of the as-synthetic catalysts were measured by N2 physisorption, XRD, SEM, O2-TPD, H2-TPR, TG, and FT-IR analyses. In dry conditions, the elimination rate of O3 followed the sequence of MnOx > Cu/MnOx > CuO. The introduction of Cu to MnOx enhanced the surface area and pore volume of Cu/MnOx, accordingly diminishing the amounts of surface defects and the participation of sub-surface lattice oxygen for catalytic cycle, indicating that surface defects and oxygen vacancies (VO) determined the catalytic activity for O3 decomposition. In humid conditions, the elimination rate of O3 changed to the sequence of Cu/MnOx > MnOx > CuO, with a variation rate compared to dry conditions of −62.9% for MnOx, 14.2% for CuO, and 27.7% for Cu/MnOx. The decrease of participant sub-surface lattice oxygen and the accumulation of intermediates in humidity diminished the decomposition of O3 on MnOx, while the active species such as superoxide radicals generating from the reaction of H2O and Cu/MnOx facilitated the participation of VO and the desorption of O2 from the occupied active sites, accelerating the catalytic cycle on Cu/MnOx. This work developed a deeper understanding of the influence of H2O on catalytic activity, promoting the performance of MnOx-based catalysts for practical O3 decomposition.

Insights into bromate reduction by Fe(II): Multiple radicals generation and carbamazepine oxidation

• Reduction of BrO 3 − by Fe(II) produced HO•, O 2 • − and reactive bromine species. • HO• and O 2 • − were generated from decomposition of BrO 3 − and its intermediates. • BrO 3 − /Fe(II) system can efficiently degrade organics with diverse structures. • Degradation products of carbamazepine were identified in BrO 3 − /Fe(II) system. • Effect of reaction conditions and water matrices was studied. Reduction of bromate (BrO 3 − ) by various technologies has been extensively investigated, while the fate of oxygen and bromine atoms in BrO 3 − in these processes has been largely ignored. In this study, reduction of BrO 3 − by Fe(II) ions was investigated under various conditions via electron spin resonance (ESR), laser flash photolysis (LFP), probe of phenol and quenching experiments. It was found that reduction of BrO 3 − by Fe(II) ions produced HO•, O 2 • − and reactive bromine species (eg., Br• and Br 2 • − ). HO• and O 2 • − were generated from release of one/two oxygen atoms in BrO 3 − and its reduction intermediates (BrO 2 − and BrO − ) at one time, while Br• and Br 2 • − were generated from activation of hypobromous acid by Fe(II) and reactions of HO• with formed Br − . Due to the formation of these reactive species, the tested ten organic pollutants with diverse structures can be efficiently degraded, which including carbamazepine (CBZ), ibuprofen, phenol, benzoic acid, paracetamol, bisphenol a, 4-chlorophenol, oxcarbazepine, diclofenac and sulfamethoxazole. CBZ degradation intermediates by BrO 3 − /Fe(II) system were specially identified by liquid chromatography (LC)-mass spectrometry (MS), and three pathways of hydroxylation/nitrosylation, ring contraction-amine cleavage and bromination for CBZ degradation were proposed accordingly. This study might shed new fundamental insights to bromate reduction and its implication for transformation of co-existed organic pollutants.

Study on the liquid phase-derived activation mechanism in Al-rich alloy hydrolysis reaction for hydrogen production

Bulk Al-Ga-In-Sn alloys are potential on-demand hydrogen generation materials, and Ga, In, and Sn with fascinating liquid characteristics manifest extraordinary activation capabilities in an Al–H2O reaction for hydrogen production. In the present work, the hydrogen production performances of Al-rich alloys were explored and the corresponding activation mechanism was investigated. The actual composition of the grain boundary (GB) phase in each alloy was determined by the Ga-In-Sn ternary phase diagram. A significant morphological transformation in the grain boundary particles (GBPs) was observed. Based on the surface tension of GBPs, the “Marangoni effect” was used to explain the hydrogen release rates of different alloys during hydrolysis. In addition, a liquid phase-derived activation mechanism during Al hydrolysis was proposed. The as-cast Al-Ga-In-Sn alloys were also used as energy carriers, and the power-consuming load was successfully supplied through the on-demand hydrogen supply mode, verifying the feasibility of liquid phase-activated Al-rich alloys in hydrogen energy applications.

Atomic insights into the combustion behavior of Al nano-droplets with H2O vapor at high temperature

Al/H2O based fuel has been a hot research area in energy field. But the combustion behavior of molten Al nano-droplets (ANDP) and H2O vapor at high temperatures is unclear. Reactive molecular dynamic was used to reveal the reaction mechanism of molten ANDP and H2O vapor at high temperature from an atomic perspective. The effects of temperature, ANDP particle size and H2O vapor concentration on ANDP combustion were considered. In general, the combustion of ANDP particle is accompanied with the outward extending growth of the oxidized phase in shapes of withe, bough and micro-explosion. The reactions of ANDP and H2O can be divided into: (1) H2O + Al → O-Al + H2; (2) 2H2O + 2Al → 2OH-Al + H2; (3) H2O + Al → OH-Al + H or (H-Al); and (4) H2O + H-Al → OH-Al + H2. The branched oxidation of ANDP is mainly a heterogeneous reaction in which active Al converts into O-Al phase. The micro-explosion of ANDP leads to the gas phase combustion of Al, which can rapidly catapult the active Al into the H2O environment. The micro-explosion makes the H2O molecules to decompose in pathway (1). The micro-explosion of ANDP increases the consumption of H2O and the production of H2. Increasing the temperature, decreasing the particle size or increasing H2O vapor concentration can promote the micro-explosion of ANDP. The charge and temperature distributions indicate that ANDP micro-explosion brings about the rapid formation of hot spots, voids and large electrostatic potential differences. The uncovered details in the reaction process of molten nano-Al with H2O vapor are expected to guide the application of Al/H2O fuel and Al/H2O hydrogen production technology.

High-yield electrochemical upgrading of CO2 into CH4 using large-area protonic ceramic electrolysis cells

Electrochemical production of commodity chemicals via CO2–H2O co-electrolysis using solid oxide electrolysis cells presents a promising cost-effective energy-storage approach. Here, we harness the unique property of protonic ceramic electrolysis cells (PCEC) and demonstrate direct electrochemical production of CH4 from CO2–H2O in a PCEC unit-cell stack. An exceptional CH4-yield ratio of 34.6% from only CO2–H2O reactants and greater than 70% with exhaust H2 recycle were achieved under an electrolysis current of –1 A cm–2 at 450 °C. Additionally, the electrochemical co-conversion of CO2–H2O offered a higher CH4-yield ratio compared to the thermochemical conversion of CO2–H2 under certain operating conditions, indicating possible electrochemical promotion of catalytic CO2 methanation. Techno-economic analyses were conducted to reveal potential operating conditions that yield a promising levelized cost of fuel production. The demonstrated good performance of the unit-cell stack shows promising scalability of PCECs for practical application from a system-level viewpoint.

Charge Transfer Reactions between Water Isotopologues and Kr+ ions.

Astrochemical models often adopt capture theories to predict the behavior of experimentally unmeasured ion–molecule reactions. Here, reaction rate coefficients are reported for the charge transfer reactions of H2O and D2O molecules with cold, trapped Kr+ ions. Classical capture theory predictions are found to be in excellent agreement with the experimental findings. A crossing point identified between the reactant and product potential energy surfaces, constructed from high-level ab initio calculations, further supports a capture-driven mechanism of charge transfer. However, ion–molecule reactions do not always agree with predictions from capture theory models. The appropriateness of using capture theory-based models in the absence of detailed experimental or theoretical studies is discussed, alongside an analysis of why capture theory is appropriate for describing the likelihood of charge transfer between Kr+ and the two water isotopologues.

Chemical reactions in H2O:CO interstellar ice analogues promoted by energetic heavy-ion irradiation

ABSTRACT H2O:CO, at concentrations of (3:2) and (10:1), was condensed on CsI substrate at 15 K and irradiated with 46-MeV 58Ni11 + ion beam. Radiolysis induced by fast heavy ions was analyzed by infrared spectroscopy (FTIR). The formation of nine molecular species: CO2, H2O2, HCOOH, HCO, H2CO, 13CO2, CH3OH, O3, and C3O2 was observed. For both concentrations, carbon dioxide (CO2), formaldehyde (H2CO), formic acid (HCOOH), and hydrogen peroxide (H2O2) are the most abundant products species, and tricarbon dioxide (C3O2) is much less abundant. Precursor destruction cross-sections and formation cross-sections of products are determined. The CO destruction cross-section for the (3:2) concentration is almost five times higher than that of water, while those for the (10:1) concentration are practically the same. Atomic sputtering yields are estimated for the two ice films, the total mass sputtered is approximately 2.5 × 106 u per impact. These results contribute to figure out the chemical pathways of compounds synthesized from the two most abundant organic species (H2O and CO) observed in the ices of grain mantles of the circumstellar envelopes and interstellar medium. In additional, the finding results reveal that molecular astronomical percentages are comparable to those obtained after 15 eV molec−1 of deposited dose in current experiments compared with the relative concentration of molecules in solid phase observed in MYSO, LYSO, BG Stars, and Comets.

Effect of Water and Formic Acid on ·OH + CH4 Reaction: An Ab Initio/DFT Study

In this work, we used ab initio/DFT method coupled with statistical rate theory to answer the question of whether or not formic acid (HCOOH) and water molecules can catalyze the most important atmospheric and combustion prototype reaction, i.e., ·OH (OH radical) + CH4. The potential energy surface for ·OH + CH4 and ·OH + CH4 (+X) (X = HCOOH, H2O) reactions were calculated using the combination of hybrid-density functional theory and coupled-cluster theory with Pople basis set [(CCSD(T)/ 6-311++G(3df,3pd)//M06-2X/6-311++G(3df,3pd)]. The results of this study show that the catalytic effect of HCOOH (FA) and water molecules on the ·OH + CH4 reaction has a major impact when the concentration of FA and H2O is not included. In this situation the rate constants for the CH4 + HO···HCOOH (3 × 10−9 cm3 molecule−1 s−1) reaction is ~105 times and for CH4 + H2O···HO reaction (3 × 10−14 cm3 molecule−1 s−1 at 300 K) is ~20 times higher than ·OH + CH4 (~6 × 10−15 cm3 molecule−1 s−1). However, the total effective rate constants, which include the concentration of both species in the kinetic calculation has no effect under atmospheric condition. As a result, the total effective reaction rate constants are smaller. The rate constants when taking the account of the FA and water for CH4 + HO···HCOOH (4.1 × 10−22 cm3 molecule−1 s−1) is at least seven orders magnitude and for the CH4 + H2O···HO (7.6 × 10−17 cm3 molecule−1 s−1) is two orders magnitude smaller than ·OH + CH4 reaction. These results are also consistent with previous experimental and theoretical studies on similar reaction systems. This study helps to understand how FA and water molecules change the reaction kinetic under atmospheric conditions for ·OH + CH4 reaction.

Mechanism of H2-O2 reaction in supercritical water

H2-O2 reaction in supercritical water has been widely studied due to its promising application in industry. The global rate of this reaction was found independent of O2 with equivalence ratio ranging from 0.042 to 4.1 in the literature. Aim of current study is to examine intermediates interaction responsible for properties of the O2 independence and others. The study involves experiment re-examining the oxygen independence phenomenon and simulation centering on reduced mechanisms derived by quasi-steady-state approximation. The experiment with equivalence ratio ranging from 3.5 to 7.2 produces similar temperature increases, signifying a global reaction rate independent of oxygen. The phenomenon of oxygen independence was then inspected by a three-step reduced mechanism and is attributed to a special role of H + O2 + M → HO2 + M. This particular reaction dominating H and O2 consumption with a fast rate is responsible for the concurrence of independences of its reaction coefficient, H, and O2 to global reaction rate. Another property that HO2 quantity indicates reactive intensity was investigated by a two-step reduced mechanism and is credited to a small activation energy of reaction HO2 + HO2 → H2O2 + O2 and a thermal system.