Detailed Reaction Mechanism Research Articles

Carboxylate-Assisted Carboxylation of Thiophene with CO2 in the Solvent-Free Carbonate Medium

Direct carboxylation of thiophene with CO2 has been achieved under a relatively mild solvent-free carbonate and carboxylate medium. This base-mediated medium can cleave the very weakly acidic C–H bond without using other limiting reagents, which is one indispensable step in the carboxylation reaction. Product yield varies with different carboxylate salts, and cesium pivalate is the most suitable base additive among targeted simple carboxylate salts. Furthermore, the detailed mechanism of this carboxylation reaction is studied, which involves initial proton abstraction, rendered by carbonate and C–C bond formation, by inserting CO2. The activation energy barrier of the C–H activation step is higher than the following CO2 insertion step, whether for the formation of the mono- and/or di-carboxylate, which indicates that the C–H deprotonation induced by the base is slow and the resulting carbon-centered nucleophile reacts rapidly with CO2.

Exploring the Mechanism of Cr(VI) Catalyzed Hypochlorous Acid Decomposition**

AbstractChlorate is produced through electrolysis of a chloride containing electrolyte in an undivided cell. Cr(VI) is added to the electrolyte in order to minimize the amount of oxygen formed through the homogeneous decomposition of hypochlorite. Despite the importance of Cr(VI) for the chlorate process we posses only very limited knowledge regarding the active Cr(VI) species and mechanisms through which it aids chlorate formation and inhibits O2 evolution. Using density functional theory (DFT) modeling we present for the first time a detailed reaction mechanism for the chromate catalyzed chlorate formation. Our calculations indicate, that the reaction is initialized by the formation of a Cr(VI)‐O−ClOCl species which forms Cr(VI)‐OClO intermediate. This step is found to be rate determining with a rate constant which is comparable to the disproportionation reaction without catalyst. Chlorate is then obtained either through an uncatalyzed oxidation of chlorite to chlorate or the nucleophilic attack of OCl− followed by a second Cl− elimination step. The comparison of the activity of the different Cr(VI) species reveals that only CrO42− is active whereas HCrO4− and Cr2O72− display sluggish kinetics.

Thermal and chemical analysis on the hetero-/homogeneous combustion characteristics of H2/Air mixture in a micro channel with catalyst segmentation

The heterogeneous-homogeneous combustion characteristics of premixed H2/Air mixture in a micro combustor with 2 mm platinum (Pt) catalyst segmentation are investigated by numerical simulation. The detailed chemical reaction mechanisms of gas-phase reaction and surface reaction of H2 are employed in a 2D CFD model by the verification. The characteristics in the catalytic combustor, such as temperature distribution, species concentration, kinetics reaction rate and heat transfer, are examined by varying inlet flow velocities. There is an interesting fact that an obvious demarcation line splits the channel into two regions at high velocities, which are dominated by heterogeneous reaction (Htr) and homogeneous reaction (Hr). In addition, there is a coupling heterogeneous-homogeneous reaction (HHr) in the 2 mm downstream of the catalytic region. These should be thoroughly deliberated using thermal and chemical analyses to determine that the gaseous flame is against the Htr in the catalytic combustor. The results can be shown that the heat flux into the upstream catalytic wall is primarily due to exothermicity induced by Htr. A low amount of heat feedback via the solid wall to inlet wall which is released by Hr. The heat fluxes from the gas–solid interface preheat the fresh gaseous mixture in the channel, thereby promoting the occurrence of Hr, increasing the heat release rate and kinetic reaction rate of Hr. Moreover, heat feedback from the heat release of Hr through the solid wall increases the reaction rates of Htr. The hydrogen conversion rate is improved by the effect of Htr in the catalytic combustor. In summary, the effect of introducing catalytic surface to induce the Htr could be well suitable for micro combustion schemes.

Advanced catalytic upgrading of biomass pyrolysis vapor to bio-aromatics hydrocarbon: A review

In order to solve the energy crisis and environmental pollution, the production of bio-aromatics from renewable biomass resources has become an effective way. However, due to the complexity of the composition and structure of biomass resources, the conversion mechanism of bio-aromatics is relatively complex, and the problems such as low yield of target products, poor selectivity and deactivation of catalysts limit its further application. Therefore, it is necessary to understand deeply the mechanism of biomass conversion to highly selective bio-aromatics. Although considerable progress has been made in the development of bio-aromatics from biomass, the detailed process and reaction mechanism of bio-aromatics are still lack of a comprehensive summary. This paper reviews the latest progress in the development of biomass to bio-aromatics, including biomass raw materials and biomass-derived model compounds, catalysts, hydrogen-rich reagents, synergistic catalysis on aromatics selectivity. The effects of process conditions on the yield of bio-aromatics were discussed, and the advantages, disadvantages of various catalysts and product characteristics were compared in detail. The mechanism and pathways for bio-aromatic via different catalysts and hydrogen-rich reagents was discussed in detail. Some challenges and prospects were put forward for the existing problems of this technology, which provided an important theoretical basis for the preparation of high value-added bio-aromatics in the field of biomass catalytic pyrolysis in the future.

Mechanism and Kinetics of Methane Combustion. Part II: Potential Energy Surface for Hydrogen-Abstraction Reaction of CH4 + O(3P).

Methane combustion plays an important role in various fields such as combustion chemistry and atmospheric chemistry of the stratosphere. Highly accurate study of its initial reaction remains a key challenge. Here, through extensive studies with a state-of-the-art ab initio and neural network method, we present a potential energy surface of the O(3P) + CH4 → OH + CH3 reaction on the ground state 13A and the first excited state 23A. In this work, the energies of 10 167 points covering all important regions are obtained with state-averaged complete active space self-consistent field calculations and then fitted using the Levenberg-Marquardt algorithm with a root-mean-square error of 0.391 and 0.442 kcal/mol for the 13A and 23A states, respectively. This study explores the characteristics of the radical van der Waals (VdW) complex and reveals a detailed mechanism of the methane combustion initial reaction. Within the scope of this mechanism, this surface gives a fairly accurate description of the regions around the saddle point, conical intersection, and vdW wells in the entrance for efficient computational simulations. As a theoretical study on a prototypical polyatomic reaction, it is hopeful that this work will modify our understanding of the primary process in hydrocarbon combustion.

Study of combustion and NO chemical reaction mechanism in ammonia blended with DME

Ammonia (NH3) has been supposed to be the potential alternative energy source towards carbon neutrality. However, it has several unfavorable combustion characteristics, such as the slow combustion rate, poor combustion stability, high ignition energy and so on. As a renewable fuel, dimethyl ether (DME) is also considered to be a favorable carbon–neutral fuel, which can improve the combustion process of ammonia. To investigate the combustion and emission mechanism for the NH3/DME dual-fuel combustion, a detailed chemical reaction mechanism with 221 species and 1597 reactions was developed based on the previous relevant work. The laminar burning velocity (LBV) and ignition delay time (IDT) of ammonia, DME and NH3/DME combustion under a wide range of initial conditions were validated in 0-D and 1-D models. The process of NO formation and reduction reaction was also studied under the laminar burning combustion and ignition model, and it was found that fuel NOx still dominates the total NOx production in NH3/DME combustion, and the DME addition in ammonia up to 50% promotes the NO formation reaction, producing more NO. In order to analyze the effect of DME addition on NO formation mechanism, the analyses of chemical reaction pathway, sensitivity analysis on NO, typical active radical evolution behaviors and rate of production (ROP) were conducted in detail. In comparison with D50 (50%NH3/50%DME), D25(75%NH3/25%DME) with higher ammonia content generates more NH and NH2 radicals, and therefore, promoting the NO reduction reaction. Lower DME content in D25 also generates less H/O/OH active radicals, which inhibits the generation of NO. It is reduced by 9% approximately in total at equivalence ratio of 0.7. In addition, CH3 generated from DME could also partly promote the conversion of HNO and NO2 to NO, slightly increasing the NO production.

Non-catalytic direct conversion of CH4 and CO2 into high-quality syngas

Both partial oxidation and CO2 reforming can theoretically be used to produce syngas from natural gas. In this work, the possibility of combining the two methods is explored by the use of computational fluid dynamics with detailed chemical reaction mechanisms. It is showed that methane partial oxidation reactor being used industrially can be directly used to transfer CH4 and CO2 into syngas. The effect of the ratio, feed velocity and preheating temperature of the reactants are examined. The optimal overall ratio of reactants is 5:4:1 for CH4 to O2 to CO2, and the optimal preheating temperature and inlet velocity is 923 K and 200–300 m/s, respectively. The conversions of CH4 and CO2 are 99.88% and 46.85%, respectively, and the yields of CO and H2 are 90.8% and 65.13%, respectively. Cooling down the product can easily obtain the target product (syngas) from water vapor. These results suggest an economically competitive way to use the two greenhouse gases for the production of syngas.

Tuning structural and electronic properties of recycled vanadium oxides via doping trace impurity for sustainable energy storage

To meet the urgent requirement of sustainable energy storage technologies, it is essential to incorporate efficient waste management into designing energy storage materials. Herein, we report an environmentally responsible pathway to utilize the recycled V2O5 from V-Cr slag leaching solution. Because of the fact that trace Cr are existed in the recycled V2O5 from initial leaching solution. Therefore, the Cr-doped V2O5 with different content of Cr was successfully synthesized and the effect of Cr on the structure and electronic characteristics of V2O5 was systematically investigated. The date arising from spectral analyses informs us that the trace Cr doping can result in an expansion of the V2O5 lattice, and lead to the decreasing of the work function values, so aiding in enhancing the electrochemical performance. Owing to the trace Cr doped into V2O5 lattice, the recycled V2O5 shows a high specific capacity of 405.5 mAh g−1 and excellent cycling stability over 2000 cycles. A detailed electrochemical reaction mechanism of Cr-doped V2O5 cathode is investigated through a series of in-depth analyses. Different from conventional recycled strategy, we use the impurity element Cr, which is very difficult to separate from V, and realize the enhancement of the electrochemical performance of the recycled V2O5. Moreover, the practicability of recycled V2O5 is exemplified by fabricating a flexible, quasi-solid-state zinc batteries, and the cell operates well upon deformation. This work provides a new strategy for recycling wasted materials into high value materials for sustainable battery systems.

A Tetraorganyl-Alumaborane with An Al-B σ-Bond and Two Adjacent Lewis-Acidic Centers.

A tetraorganyl-alumaborane (3) that contains an Al-B bond and twisted Al and B planes was synthesized and structurally characterized. UV-vis absorption spectroscopy, electrochemical measurement, and DFT calculations were employed to reveal the electronic properties of 3. The reactivity of 3 toward DMSO and CO was studied to demonstrate its deoxygenating abilities. On the basis of the results of the DFT calculations, a detailed reaction mechanism was developed, which highlighted the important role of the distinct Lewis acidity of the group-13 elements Al and B in 3.

SnSex (x = 1, 2) nanoparticles encapsulated in carbon nanospheres with reversible electrochemical behaviors for lithium-ion half/full cells

• SnSe x ⊂ CNSs (x = 1, 2) obtained by different in-situ selenation temperature. • SnSe x ⊂ CNSs show excellent electrochemical performances in half/full cells. • Reversible conversions of SnSe x ⊂ CNSs confirmed by ex-situ XRD. • More intermediate Li 2 Se in SnSe 2 ⊂ CNSs display excellent ion kinetics. • SnSe 2 ⊂ CNSs present batter electrochemical performance than SnSe ⊂ CNSs. Tin selenide materials, including SnSe and SnSe 2 , have larger interlayer spacing, weaker van der Waals forces still suffer undesirable volume changes as lithium-ion battery anodes. Herein, we successfully synthesized hierarchical SnSe x (x = 1, 2) nanoparticles encapsulated in carbon nanospheres (SnSe x ⊂ CNSs) by facile in-situ selenation method at different temperature. Partially diffused SnSe x nanoparticles form halo surrounding the SnSe x core with spare inner void space, coupled with thin carbon layer could enhance ionic transport and buffer volume expansion of SnSe x in Li + insertion/desertion processes. The SnSe ⊂ CNSs and SnSe 2 ⊂ CNSs anodes all deliver high initial coulombic efficiency, superior cycle stability and excellent rate capability. SnSe ⊂ CNSs//LiMn 2 O 4 and SnSe 2 ⊂ CNSs//LiMn 2 O 4 full cells also exhibit outstanding electrochemical properties. Furthermore, ex-situ X-ray diffraction patterns demonstrate the detailed reaction mechanisms and confirm the reversible conversions of SnSe ⊂ CNSs and SnSe 2 ⊂ CNSs. The comparison of dynamic behaviors of them by electrochemical impedance spectroscopy and cyclic voltammetry at different cycles confirm the existence of more intermediate Li 2 Se in SnSe 2 ⊂ CNSs, which could enhance the ion kinetics and improve rate capability. Thus, lower synthesis temperature, lower Li + migration energy barrier, outstanding electrochemical performance, and higher excellent ion kinetics of SnSe 2 ⊂ CNSs suggest that our synthesized SnSe 2 ⊂ CNSs are more suitable as LIB anodes to increase the energy density.

Numerical Investigation of the Ignition Delay Time of Kerosene Premixed Combustion in an SI Engine

SI engines are installed widely in small aircrafts as they have good fuel economy. Currently, these SI engines are fueled with gasoline, although their safety can be improved if kerosene is used. However, the combustion performance of kerosene cannot fulfil the requirements due to the differences in physicochemical properties. This study investigates the ignition delay time of kerosene at a pressure range of 15–35 bar and a temperature range of 600–1000 K. A detailed chemical reaction mechanism is employed for the premixed combustion process. Under the initial conditions of 1000 K and 35 bar, with an equivalence ratio of 1, the total ignition delay time of kerosene is 0.401 ms. The NTC range of kerosene is determined as roughly 750–920 K. Subsequently, the chemical reaction paths with an equivalence ratio of 0.8, 1, and 1.2 and an initial pressure of 15, 20, and 25 bar were analyzed. The rate-determined elementary reactions were obtained based on a sensitivity analysis. The difference between kerosene and gasoline are also compared, and the rate-determining reactions that affect the ignition of kerosene and gasoline are discussed. The results of this study can provide a reference for the combustion performance improvement and knock suppression of SI engines fueled with kerosene.

Unexpected role of electron-transfer hub in direct degradation of pollutants by exoelectrogenic bacteria.

Exoelectrogenic bacteria (EEB) are capable of anaerobic respiration with diverse extracellular electron acceptors including insoluble minerals, electrodes and flavins, but the detailed electron transfer pathways and reaction mechanisms remain elusive. Here, we discover that CymA, which is usually considered to solely serve as an inner-membrane electron transfer hub in Shewanella oneidensis MR-1 (a model EEB), might also function as a reductase for direct reducing diverse nitroaromatic compounds (e.g. 2,4-dichloronitrobenzene) and azo dyes. Such a process can be accelerated by dosing anthraquinone-2,6-disulfonate. The CymA-based reduction pathways in S. oneidensis MR-1 for different contaminants could be functionally reconstructed and strengthened in Escherichia coli. The direct reduction of lowly polar contaminants by quinol oxidases like CymA homologues might be universal in diverse microbes. This work offers new insights into the pollutant reduction mechanisms of EEB and unveils a new function of CymA to act as a terminal reductase.

Density Functional Theory Study of the Oxygen Reduction Reaction Mechanism on Graphene Doped with Nitrogen and a Transition Metal.

The active centers of carbon nonplatinum catalysts doped with cobalt, iron, nickel, and copper have been simulated by quantum-chemical density functional theory methods. The thermodynamics of the electrochemical oxygen reduction reaction (ORR) on model catalysts has been determined. It was found that among the studied catalysts, graphene doped with cobalt and iron showed the best properties. A two-state reactivity effect has been found on a cobalt-containing catalyst, and a more detailed reaction mechanism has been proposed, including the stages of charging by an extra electron and association with water. The proposed mechanism explains several effects that have arisen during the modeling in relation to the classical mechanism.

Recent Advances in Catalytic [3,3]-Sigmatropic Rearrangements

Carbon–carbon bond formation by [3,3]-sigmatropic rearrangement is a fundamental and powerful method that has been used to build organic molecules for a long time. Initially, Claisen and Cope rearrangements proceeded at high temperatures with limited scopes. By introducing catalytic systems, highly functionalized substrates have become accessible for forming complex structures under mild conditions, and asymmetric synthesis can be achieved by using chiral catalytic systems. This review describes recent breakthroughs in catalytic [3,3]-sigmatropic rearrangements since 2016. Detailed reaction mechanisms are discussed to enable an understanding of the reactivity and selectivity of the reactions. Finally, this review is inspires the development of new cascade reaction pathways employing catalytic [3,3]-sigmatropic rearrangement as related methodologies for the synthesis of complex functional molecules.

Free-Energy Profile Analysis of the Catalytic Reaction of Glycinamide Ribonucleotide Synthetase.

The second step in the de novo biosynthetic pathway of purine is catalyzed by PurD, which consumes an ATP molecule to produce glycinamide ribonucleotide (GAR) from glycine and phosphoribosylamine (PRA). PurD initially reacts with ATP to produce an intermediate, glycyl-phosphate, which then reacts with PRA to produce GAR. The structure of the glycyl-phosphate intermediate bound to PurD has not been determined. Therefore, the detailed reaction mechanism at the molecular level is unclear. Here, we developed a computational protocol to analyze the free-energy profile for the glycine phosphorylation process catalyzed by PurD, which examines the free-energy change along a minimum energy path based on a perturbation method combined with the quantum mechanics and molecular mechanics hybrid model. Further analysis revealed that during the formation of glycyl-phosphate, the partial atomic charge distribution within the substrate molecules was not localized according to the formal charges, but was delocalized overall, which contributed significantly to the interaction with the charged amino acid residues in the ATP-grasp domain of PurD.

Development of a reduced n-heptane/toluene/unsaturated furans-PAH reaction mechanism for dual-fuel engine applications

Furan, 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) have gathered much attention in the research community. However, the reaction chemistry of the three unsaturated furans for the internal combustion engine (ICE) simulations remains scarce. Therefore, a reduced five-component reaction mechanism contains furan, MF, DMF, n-heptane and toluene was proposed for dual-fuel engine applications in present research. First, a detailed reaction mechanism for furanic fuels was reduced under a wide range of enginelike conditions by using combined reduction methods. Second, the reduced mechanism of furanic fuels was combined with an existing n-heptane/toluene mechanism containing the formation of polycyclic aromatic hydrocarbon (PAH) up to C16 to construct a combined mechanism. Third, the combined mechanism were optimized by adjusting the reaction rate constants of some significant reactions and the newly proposed reduced n-heptane/toluene/unsaturated furans-PAH mechanism comprising 98 species taking part in 253 reactions. Subsequently, the proposed mechanism was compared and evaluated with experimental measurements of ignition delay times and species mole fractions acquired from published papers. Meanwhile, new dual-fuel engine experiments were performed in a single-cylinder diesel engine, the experimental results were also used to validate the proposed mechanism. Overall, the predicted results obtained by this proposed n-heptane/toluene/unsaturated furans-PAH mechanism are in reasonable agreement with the available experimental data.

Multiscale Simulation of Solid Electrolyte Interface Formation in Fluorinated Diluted Electrolytes with Lithium Anodes.

Lithium metal batteries (LMBs) hold great promise in facilitating high-energy batteries due to their merits such as high specific capacity, low reduction potential, and so forth. However, the realizations of practical LMBs are hindered by severe problems such as undesirable dendrite growth, poor Coulombic efficiency, and so forth. A recently proposed fluorinated electrolyte based on 1 M lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in designed fluorinated 1,4-dimethoxybutane (FDMB) solvent has attracted significant attention because of its excellent electrochemical performance that origins from its superior physical and chemical properties, especially its unique ability in forming a robust, stable solid electrolyte interphase (SEI). However, the detailed structure and reaction mechanism of the SEI formation in such a novel electrolyte remains unclear. In this work, we carry out a hybrid ab initio and reactive molecular dynamics (HAIR) simulation to investigate the elementary reactions that regulate the formation of the primitive SEI, paying special attention to the process that involves FDMB, the fluorinated solvent. HAIR simulation reveals that both FSI- anion and FDMB provide F that is adequate to form a uniformed LiF layer that resembles the inorganic inner layer (IIL) of the SEI. N and S radicals from the FSI- anion, which do not deposit on the electrode interface to form lithium-containing inorganic substances, promote the polymerization reaction of unsaturated carbon chains produced by FDMB defluorination, forming the organic outer layer (OOL) of the SEI. The combination of the LiF-rich IIL and polymer-rich organic OOL explains the superior performance of the FDMB-based electrolyte in the device. The detailed reaction mechanism and SEI observed in this work provide insights into the atomic scale for the rational design of F-rich electrolytes in the near future.

Ab initio kinetics of OH-initiated oxidation of cyclopentadiene

This work computationally reports a detailed kinetic mechanism of the OH-initiated reaction of 1,3-cyclopentadiene (CPDN), a key intermediate during the oxidation processes of aromatic and acyclic compounds, in the wide range of T = 298 – 2000 K and P = 0.76 – 7600 Torr. The temperature- and pressure-dependent behaviors of the title reaction were simulated using the RRKM-based Master Equation rate model on the potential energy profile explored at M06-2X/aug-cc-pVTZ level. The model reveals that the OH-addition on Cα of CPDN to form adduct 5-hydroxycyclopent-2-en-1-yl dominates at low temperatures (e.g., T ≤ 1000 K at 760 Torr), while the direct H-abstraction channels from Cα and Cβ of CPDN become predominant at high temperatures (e.g., T > 1000 K at 760 Torr). The observed U-shaped temperature-dependent behaviors and slightly positive pressure dependence at low temperatures (e.g., T ≤ 1000 K &P = 760 Torr) of the total rate constants are described by a double modified Arrhenius expression as ktot(T) = 1.61 × 109 × T−6.67 × exp[-1627.6 K/T] + 3.87 × 10-17 × T2.08 × exp[-2519.9 K/T] (cm3/molecule/s) for T = 298 – 2000 K &P = 760 Torr. Discrepancies in ktotal(T, P) between the early calculations and measurements in low- and high-temperature regimes are also resolved. Also, the thermodynamically consistent mechanism is provided to advance modeling and simulation of any CPDN-related applications.

Three-Dimensional Numerical Analysis of Longitudinal Thermoacoustic Instability in a Single-Element Rocket Combustor

This study numerically investigated the thermoacoustic combustion instability characteristics of a scaled rocket combustor based on a hybrid of the Reynolds-averaged Navier–Stokes and large–eddy simulation method. The turbulence–combustion interactions were treated using flamelet generated manifold approach. An unstable case was simulated with detailed reaction mechanisms (GRI-Mech 3.0). The obtained results agree well with experiment data from Purdue University, in terms of pressure oscillations frequency and power spectral density spectrum. The combustion instability mode was identified to be coupled with the first longitudinal acoustic mode of the combustion chamber by dynamic model decomposition method. According to Rayleigh index analysis, the unstable driving source was found to be located near the combustor step, which was further confirmed by time-averaged flow fields. Detailed three-dimensional vortex ring shedding evolutions at the combustor step were tracked with fine time resolution. Results indicate that the combustion instability arises from periodic vortex ring shedding at the combustor step and interacting with the chamber wall. The unburnt reactants were rolled up by the shedding vortex ring, which would not break up until impact with the chamber wall. Therefore, the mixing performance was significantly enhanced, leading to sudden heat release. Consequently, the thermal energy is added to the acoustic field, and the first longitudinal mode is thus reinforced, giving rise to large amplitude axial velocity oscillations which prompt the generation of the new vortex ring. The results of the present investigation will support the design and development of high-performance rocket engines.

Numerical and experimental study of product gas characteristics in premixed ammonia/methane/air laminar flames stabilised in a stagnation flow

The adoption of ammonia/hydrocarbon fuel blends can be viewed as an intermediate step towards a hydrogen economy, hence the characterization of methane/ammonia flame product gas trends is essential for designing combustors for a broader range of low-carbon fuel blends while fulfilling strict NOx requirements. This paper describes the product gas content of laminar premixed ammonia/methane flames for a range of equivalence ratios and ammonia heat ratios ranging from 10% to 60%, using a strain stabilized burner at atmospheric pressure and room temperature. The optimal condition to reduce NOx emissions while maintaining below 100 ppm of unburnt NH3 emissions was found to be at equivalence ratio of 1.20 for higher ammonia ratios, moving incrementally closer over 1.35 as the methane fuel content was increased. Meanwhile, the highest measured NO values were ∼6,950 ppm at an equivalence ratio of 0.9, peaking at heat ratios of 30% to 40% at this equivalence ratio. Detailed reaction mechanisms were evaluated against the experimental data and rate constants of NO production/consumption steps featuring both NH and HNO intermediates and thermal NOx reactions were updated for Okafor's mechanism. Changes in reaction rate constants improved the mechanism accuracy for NO emissions in lean to stoichiometric flames. Meanwhile, in the rich region, modelled NO values were less responsive to changes in reaction constants, suggesting the need for an alternative approach to improve NO predictions for rich, high methane content flames. However, N2O performance in the rich region could be improved, highlighting the significance of the HNO+CO→NH+CO2 reaction.