Homogeneous Reaction Mechanisms Research Articles

Kinetics of free fatty acids esterification in waste frying oil using novel carbon-based acid heterogeneous catalyst derived from Amazonian Açaí seeds – Role of experimental conditions on a simpler pseudo first-order reaction mechanism

This study reports the kinetics of free fatty acids esterification in waste frying oil, based on a simpler non-conventional pseudo first-order homogeneous reaction mechanism using a highly-efficient acid heterogeneous catalyst derived from seeds of Açaí (Euterpe oleracea Mart.), subjected to changes in temperature, catalyst dosage, MeOH:Oil ratio, and stirring speed. Statistical analyses revealed significant effects all four conditions (p < .05) on the reaction's apparent rate constant (k1) over their different pre-defined levels. Reaction mechanism was inferred to be fundamentally acid ionic exchanges with the oil/water film on catalyst's surface, neglecting kinetically controlled liquid-to-liquid splitting and autocatalyzed esterification.

Fuel-rich hetero-/homogeneous combustion of C3H8/O2/N2 mixtures over rhodium

The catalytic (heterogeneous) and gas-phase (homogeneous) combustion of C3H8/O2/N2 mixtures over rhodium was investigated experimentally and numerically at 5 bar and at fuel-rich equivalence ratios φ = 2.0-3.5 relevant to propane Catalytic Partial Oxidation (CPO). In situ spatially-resolved Raman measurements of major gas-phase species concentrations and Planar Laser Induced Fluorescence (PLIF) of formaldehyde were applied in an optically accessible channel-flow reactor to monitor the catalytic and gas-phase processes, respectively, while accompanying 2D simulations were carried out with detailed hetero-/homogeneous chemical reaction mechanisms. Due to the high gas-phase reactivity of propane, homogeneous chemistry could not be ignored over most of the reactor's oxidation zone length (upstream zone where the deficient reactant oxygen is not fully consumed). The presence of gas-phase chemistry deteriorated the otherwise high catalytic syngas (H2 and CO) selectivities over the oxidation zone. Raman measurements of major gas-phase species concentrations over the restricted oxidation zone length without appreciable gas-phase chemistry showed that the catalytic reaction mechanism slightly underpredicted (overpredicted) the H2 (CO) formation. The same behavior was also attested over the remaining length of the oxidation zone where combined catalytic and gas-phase chemistry was present. The production of considerable amounts of H2 at the highest investigated equivalence ratio of 3.5 accelerated the onset of homogeneous ignition and the formation of strong flames. The discrepancies between measured and predicted homogeneous ignition distances were less than 6.8% in all cases, illustrating the validity of the employed hetero-/homogeneous kinetic schemes. Contrary to past methane CPO studies, the contribution of gas-phase chemistry and the formation of strong flames in propane CPO was detrimental to syngas production.

Photocatalytic Methane Conversion: Insight into the Mechanism of C(sp 3 )–H Bond Activation

Photocatalytic Methane Conversion: Insight into the Mechanism of C(sp ³ )–H Bond Activation

MXene enabled binder-free FeOF cathode with high volumetric and gravimetric capacities for flexible lithium ion batteries

The vital challenge of iron oxyfluoride (FeOF) as conversion-type cathode material is the low electronic conductivity and huge volume expansion. Design of binder-free film electrode architecture consisted of nanosized active materials and highly conductive matrix not only can resolve these issues, but also can satisfy the escalating needs of flexible and wearable electronics. Nevertheless, synthesis of nanostructured FeOF is still complicated and time-consuming to date. Here, we report the facile preparation of FeOF nanorods using FeF3•3H2O as precursor through a mixed alcohols-assisted solvothermal method based on a homogeneous reaction mechanism for the first time, which can greatly shorten the reaction time as well as lower the energy consumption. After that, a flexible Ti3C2Tx MXene and FeOF composite (denoted as FeOF/MXene) film with high strength and high conductivity is prepared by a rational combination of electrostatic self-assembly and vacuum-assisted filtration processes. As resulted binder-free FeOF/MXene cathode presents a high capacity of 365.5 mAh g − 1 at 100 mA g − 1 and stable high-rate capacity of 202.6 mAh g − 1 at 2000 mA g − 1 after 400 cycles, which are very prominent among these reported FeOF-based electrodes. The reliable synthesis method and film electrode fabrication procedure are both time-efficient, scalable and cost-effective, which can pave a pathway for the practical application of FeOF and high-performance flexible lithium-ion batteries.

Homogeneous ignition of H2/CO/O2/N2 mixtures over palladium at pressures up to 8 bar

The catalytic and gas-phase combustion of fuel-lean H2/CO/O2/N2 mixtures over palladium was investigated experimentally and numerically at a global equivalence ratio φ = 0.285, H2:CO volumetric ratios 1-4, pressures 1-8 bar and catalyst surface temperatures 950-1200 K. In situ planar laser induced fluorescence (PLIF) of the OH radical monitored homogeneous combustion inside a channel-flow catalytic reactor, while 1-D Raman measurements of main gas-phase species concentrations across the channel boundary layer assessed the heterogeneous processes. Simulations were carried out with a 2-D numerical code using detailed heterogeneous and homogeneous chemical reaction mechanisms and realistic transport. The simulated and measured transverse species profiles attested to a transport-limited catalytic conversion of H2 and CO at all operating conditions. The OH-PLIF measurements and the simulations confirmed the establishment of appreciable homogeneous combustion only for p < 4 bar, with progressively diminishing gas-phase contribution as the pressure increased from 4 to 8 bar. This strong pressure dependence reflected the complex pressure/temperature dependence of the homogeneous ignition chemistry as well as the competition between the catalytic and gaseous reaction pathways for H2 and CO consumption. Over the gaseous induction zones (x < xig), the wall temperatures were below the pressure-dependent upper temperature limit for the decomposition of PdO to metallic Pd. Even though palladium catalysts exhibited a “self-regulating” temperature effect due to the decomposition of PdO, the attained temperatures were still sufficient to ignite homogeneous combustion of the H2/CO/O2/N2 mixtures, in contrast to hydrocarbon fuels for which gas-phase combustion was largely suppressed over PdO in the pressure range 1-8 bar. The results indicated that for the elevated pressures and preheats of syngas-fueled hetero-/homogeneous combustion power systems, gas-phase chemistry cannot be ignored during reactor design.

Heterogeneous and homogeneous combustion of fuel-lean C3H8/O2/N2 mixtures over rhodium at pressures up to 6 bar

The heterogeneous and homogeneous combustion of C3H8/O2/N2 mixtures over Rh was investigated at pressures 1-6 bar, catalyst surface temperatures 680-1100 K and C3H8-to-O2 equivalence ratios 0.25-0.52. Non-intrusive laser-based measurements were applied in a channel-flow catalytic reactor and involved 1-D Raman spectroscopy of major gas-phase species across the channel boundary layer for assessing the catalytic reactivity and planar laser induced fluorescence (PLIF) of the OH radical for monitoring homogeneous combustion. Simulations were carried out with a 2-D numerical code that included detailed hetero-/homogeneous chemical reaction mechanisms. By comparing the Raman-measured and predicted transverse profiles of the limiting C3H8 reactant, the suitability of a detailed surface reaction mechanism was initially evaluated and subsequently a one-step reaction was constructed, which was applicable for the C3H8 total oxidation over Rh at pressures 1 to 6 bar. The catalytic reactivity of C3H8 over Rh displayed a ∼p0.14 pressure dependence, which was substantially lower than a previously reported ∼p0.70 dependence over Pt. The weak pressure dependence of the C3H8 reactivity on Rh suggested caution when selecting catalysts for high-pressure power systems (recuperative microreactors, small-scale turbines) fueled with C3H8 or LPG (liquefied petroleum gas). Comparisons of PLIF-measured and predicted distributions of the OH radical indicated that the employed gas-phase reaction mechanism captured the onset of homogeneous ignition at pressures greater than or equal to 3 bar as well as the ensuing flame shapes. Predicted and measured homogeneous ignition distances agreed within 2.5% at 6 bar. With decreasing pressure, the predictions yielded gradually increasing but still modest underpredictions (up to 11.2% at 3 bar) of the homogeneous ignition distances. The key gas-phase reactions affecting homogeneous combustion at various pressures were finally identified.

A DFT Study of N2O Homogeneous and Heterogeneous Reduction Reaction by the Carbon Monoxide

ABSTRACT The mechanism of N2O homogeneous and heterogeneous reactions with CO were investigated using density functional theory (DFT). The M06-2X method with the 6–311 G(d) basis set were adopted for geometry optimization and energy calculations of each configuration (reactants, intermediates, transition states and products). Thermodynamic and kinetic analyzes were also conducted to study the influence of temperature on the reaction process. Calculation results showed that there are two channels for the homogeneous reaction between N2O and CO. In addition, the heterogeneous reduction reaction of N2O and CO has two possible reaction pathways due to the different adsorption configurations of CO on char surface. From thermodynamic analysis, the enthalpy difference (ΔH) and Gibbs free energy difference (ΔG) of the homogeneous and heterogeneous reactions are both negative, which indicates that the reaction of N2O and CO is an exothermic process and can take place spontaneously. For the both homogeneous and heterogeneous reactions between N2O and CO, the equilibrium constant of the N2O and CO reaction is always higher than 105 at 800 ~ 1800 K, suggesting that the reaction can be carried out completely. From the kinetic analysis, activation energy of the heterogeneous reaction (137.26 kJ/mol) is much lower than that of the homogeneous reactions (224.53 kJ/mol and 215.89 kJ/mol), which indicates that the reduction reaction of N2O with CO is more likely to take place on char surface. The calculation results explain the reaction mechanism of N2O and CO, which can provide a theoretical foundation for N2O emission.

The effect of CO on the transformation of arsenic species: A quantum chemistry study

To explore the effect of CO on the transformation of arsenic species, the reaction mechanism of homogeneous and heterogeneous reactions for arsenic oxides (AsO2 and As2O3) with CO were investigated via density functional theory (DFT). The geometries of reactants, intermediates, transition states and products for each reaction were optimized by using the B3LYP method in conjunction with the 6-31G(d) basis set, and the single-point energy of each structure was calculated at the B2PLYP/Def2-TZVP level. Also, thermodynamic and kinetic analyses were conducted to determine the reaction process. The results showed that the homogeneous reaction of AsO2 and CO has two channels and a transition state is found in each case. The homogeneous reaction process of As2O3 and CO undergoes two transition states and, finally, As2O3 is reduced to sub-oxides by CO. Char has a strong adsorption affinity for AsO2 and As2O3 in the presence of CO, and the adsorption mode of the AsO2 molecule on the char surface has a great influence on its reduction. The activation energy of the homogeneous reduction of As2O3 (75.9 kJ mol−1) is lower than the heterogeneous reduction (94.2 kJ mol−1), which suggests that As2O3 is more likely to react with CO in the flue gas. The calculation results revealed the mechanism for the influence of CO on arsenic behavior by density functional theory. These results are helpful for a molecular-level understanding of the transformation of arsenic species, which in turn provides a theoretical foundation for the emission and control of arsenic.

Systematic Application of the Principle of Detailed Balancing to Complex Homogeneous Chemical Reaction Mechanisms.

It is not uncommon for proposed complex reaction mechanisms to violate the principle of detailed balancing. Here, we draw attention to three ways in which such violations can occur: reversible reaction loops where the rate constants do not attain closure, illegal loops, and reversible steps having rate equations in the forward and reverse directions that are inconsistent with the equilibrium expressions. We present two simple methods to test whether a proposed mechanism is consistent with the first two aspects of the principle of detailed balancing. Both methods are restricted to closed homogeneous isothermal reactions having mechanisms that consist of stoichiometrically balanced reaction steps. The first method is restricted to mechanisms in which all reaction steps are reversible; values of Δf G° are assigned to all reaction species, equilibrium constants are then computed for all steps, and all rate constants for elementary steps are constrained by the relationship Keq = kf/ kr. The second method is applicable to mechanisms that can consist of a series of reversible and/or irreversible reaction steps. One first examines the subset of reversible steps to determine whether any of these steps are stoichiometrically equivalent to a combination of any of the other steps. If so, the forward and reverse rate expressions must yield equilibrium constants that are in agreement with the stoichiometric relationships. Next, the complete set of steps is examined to look for "illegal reaction loops". Both of these procedures are performed by constructing matrices that represent the stoichiometries of the various reaction steps and then performing row reductions to identify basis sets of loops. A method based on linear programming is described that determines whether a mechanism contains any illegal loops. These methods are applied in the analysis of several published reaction mechanisms.

Differences in Formation and Oxidation of Colombian Coal Chars in Air and Oxy-fuel Atmospheres

The increasing interest towards more efficient and clean technologies, specially paying attention to CO2 neutral processes is encouraging the investigation of coal thermochemical conversion under oxy-fuel atmospheres (i.e. without N2). The process offers many advantages such as easy separation of the CO2 produced and low NOX/SOX emissions. While coal conversion in air is already well understood, full understanding of the influences of CO2-rich atmospheres is still required. A series of experiments in thermogravimetric analyser, drop-tube reactor and flat-flame burner were performed using a mid-range bituminous coal (Colombian coal) to understand the differences in the chars obtained after the pyrolysis step. Comparing the pyrolysis in N2 and CO2 atmospheres, significant differences were observed in the resulting chemical (composition) and physical properties of the chars, whereas mass loss was very similar for short residence times (< 130 ms). Afterwards, the chars obtained were submitted to oxidation and gasification, under several different operating conditions, in order to evaluate the difference in reactivity of these chars. Chars obtained under CO2 atmospheres revealed a lower reactivity, despite their higher surface area. These aspects cannot be explained and captured by a model which does not focus on some important details. In this paper, the results obtained in these experiments are summarized and discussed on the point of view of the POLIMI modelling approach for thermochemical conversion of solids. This model offers several advantages, such as being flexible to improvements, requiring simple experimental data of the fuel and offers an all-in-one solution for describing the kinetics of the whole process. The developments accounted for a wide range of experimental data, which allowed its calibration for several fuels, mostly in air combustion. It was first developed to describe the pyrolysis step, and later char oxidation/gasification was included in a simplified approach. The detailed mechanism of homogeneous gas phase reactions of the volatiles is also coupled. In order to extend the predictive capabilities of the model for oxy-fuel conditions, dedicated experiments must be considered for future improvements. In this work these missing effects are discussed, identifying the main necessary improvements, allowing this model to be extended and applied also for the designing of reactors that use oxy-fuel technologies.

Experiment and simulation on kinetic resolution of (R,S)-2-chloromandelic acid by enzymatic transesterification.

Optically pure 2-chloromandelic acid (ClMA) is a very important chiral drug intermediate for synthesis of (S)-clopidogrel, belonging to the platelet aggregation inhibitor. Enantioselective resolution of (R,S)-2-chloromandelic acid was carried out in organic solvent through irreversible transesterification catalyzed by lipase AK with vinyl acetate acting as the acyl donor. Effects of various conditions on enantioselectivity and activity of lipase were investigated, including organic solvents, temperature, water content, substrate ratio, enzyme loading, and reaction time. Based on homogeneous reaction and Ping-Pong bi-bi mechanism, a quantitative model was constructed to simulate and optimize the reaction process. Under the optimal conditions, excellent results were obtained with high conversion of (R)-2-ClMA (c R , ≥98.85%) and large enantiomeric excess of substrate (ee s , ≥98.15%). There is a good agreement between predicted values and experiment data, which indicates that the established method is a powerful tool for optimization of the enantioselective transesterification process for enantiomers separation.

Hetero-/homogeneous combustion of fuel-lean CH4/O2/N2 mixtures over PdO at elevated pressures

The heterogeneous and homogeneous combustion of fuel-lean CH4/O2/N2 mixtures over PdO was investigated experimentally and numerically at equivalence ratios φ = 0.27–0.44, pressures 1–12 bar and surface temperatures 710–1075 K. In situ Raman measurements of major gas-phase species concentrations across the boundary layer of a channel-flow catalytic reactor assessed the heterogeneous reactivity, while planar laser induced fluorescence (LIF) of the OH radical monitored homogeneous combustion. Simulations were performed using a 2-D code with detailed heterogeneous and homogeneous reaction mechanisms. Comparisons between Raman-measured and predicted transverse profiles of major species mole fractions attested the atmospheric-pressure suitability of a detailed surface mechanism and allowed for the construction of a global catalytic step valid in the range 1–12 bar. The methane catalytic reaction rate exhibited an overall pressure dependence ∼p1−n where the exponent n was itself a monotonically increasing function of pressure, rising from 0.58 at 3 bar to 1.02 at 12 bar. This resulted in a non-monotonic pressure dependence of the catalytic reaction rate in the range 1–12 bar, a behavior in stark contrast to other noble metals (Pt and Rh) where the methane reaction rates always increased with rising pressure. Surface temperatures remained well-below the PdO decomposition temperature at each corresponding pressure, owning largely to the “self-regulating” temperature effect of PdO, and this in turn mitigated homogeneous ignition. Simulations using the PdO decomposition temperatures as boundary conditions for the wall temperatures were further performed for practical CH4/air catalytic reactors in power generation systems. It was shown that for p < 7 bar (a range relevant to microreactors) homogeneous ignition was altogether suppressed. For higher pressures relevant to gas-turbine burners, however, gaseous combustion ought to be considered in the reactor design.

Direct numerical simulations of turbulent catalytic and gas-phase combustion of H2/air over Pt at practically-relevant Reynolds numbers

Three-dimensional direct numerical simulations of turbulent catalytic and gas-phase H2/air combustion at a fuel-lean equivalence ratio φ=0.18 were performed in platinum-coated planar channels at two industrially-relevant flow conditions (inlet friction Reynolds numbers Reτ= 182 and 385) using detailed hetero-/homogeneous chemical reaction mechanisms. The preferential diffusion of hydrogen and oxygen, which was responsible for creating significantly higher surface equivalence ratios φw compared to the bulk gas-phase φ, was appreciably suppressed by turbulence at Reτ= 385. The higher turbulence intensity at this Reτ resulted in larger near-wall hydrogen excess that in turn yielded shorter homogeneous ignition distances compared to the lower Reτ case. Gas-phase ignition proceeded from isolated ignition kernels that subsequently formed axially elongated flames confined close to the catalytic walls. The coupling of catalytic and gas-phase chemistry inhibited homogeneous ignition, since at the vicinity of the ignition kernels the OH, H and O radical fluxes to the underlying catalytic wall were net-adsorptive and furthermore hydrogen was depleted by the catalytic reactions. The flame topology included alternating vigorously-burning and extinguished elongated streamwise stripes at Reτ=182 or islands at Reτ=385. The extinguished gas-phase reaction zones at Reτ=385 were characterized by underlying intense catalytic reaction rates. The flame topology and spatiotemporal correlation of the isolated burning and extinguished gaseous zones indicated that significant surface temperature non-uniformities could be obtained in practical catalytic reactors.

A Kinetic Assessment of Entrained Flow Gasification Modeling

A kinetics assessment of the quasi-global homogeneous and heterogeneous reaction mechanisms is carried out for entrained flow coal gasification modeling. Accurate closure of the chemical source term in gasification modeling necessitates a detailed study of turbulence-chemistry interaction. Toward this end, a time-scale analysis of the homogeneous reactions is discussed using eigenvalue analysis of the reaction rate Jacobian matrix. A singular value decomposition (SVD) of the stoichiometric reaction matrix is performed to assess the behavior of the homogeneous reactions in a reduced species vector space. The significant factors affecting the heterogeneous char reactions are assessed, and the relative importance of bulk diffusion and inherent char kinetics is analyzed in a gasifier. The overall study is carried out using numerical and experimental results of an actual pilot scale gasifier.

Advancing Fenton and photo-Fenton water treatment through the catalyst design

The review is devoted to modern Fenton, photo-Fenton, as well as Fenton-like and photo-Fenton-like reactions with participation of iron species in liquid phase and as heterogeneous catalysts. Mechanisms of these reactions were considered that include hydroxyl radical and oxoferryl species as the reactive intermediates. The barriers in the way of application of these reactions to wastewater treatment were discussed. The following fundamental problems need further research efforts: inclusion of more mechanism steps and quantum calculations of all rate constants lacking in the literature, checking the outer sphere electron transfer contribution, determination of the causes for the key changes in the homogeneous Fenton reaction mechanism with a change in the reagents concentration. The key advances for Fenton reactions implementation for the water treatment are related to tremendous hydrodynamical effects on the catalytic activity, design of ligands for high rate and completeness of mineralization in short time, and design of highly active heterogeneous catalysts. While both homogeneous and heterogeneous Fenton and photo-Fenton systems are open for further improvements, heterogeneous photo-Fenton systems are most promising for practical applications because of the inherent higher catalyst stability. Modern methods of quantum chemistry are expected to play a continuously increasing role in development of such catalysts.

Equilibrium of liquid-liquid extraction of 2-phenylbutyric acid enantiomers: Experiment and model

Abstract The utilization of liquid–liquid extraction for the separation of 2-phenylbutyric acid (2-PBA) enantiomers was proposed. Factors affecting the extract process were investigated, including organic solvents, β-cyclodextrin derivatives, cyclodextrin concentration, pH and temperature. A model was proposed to describe the separation process based on the homogeneous phase reaction mechanism. Important parameters of this model were determined experimentally. The physical distribution coefficients for molecular and ionic 2-PBA were 0.129 and 7.455, respectively. The equilibrium constants of the complexation reactions were 89.36 and 36.78 L·mol − 1 for (+)− and (−)-2-PBA, respectively. The model was verified by experiments and proved to be an excellent means to optimize the separation system. Through modeling prediction and experiment, the best conditions ( e.g. , pH value of 3.00, extractant concentration of 0.1 mol·L − 1 , temperature of 5.0 °C) were acquired. Under this condition, the maximum enantioselectivity (2.096) was obtained.

Non-thermal plasma injection-CeO2-WO3/TiO2 catalytic method for high-efficiency oxidation of elemental mercury in coal-fired flue gas

The combined method of non-thermal plasma injection and 3%CeO2-WO3/TiO2 catalysis system was proposed to enhance Hg0 oxidation in flue gas. Compared with the plasma system, the combined system had excellent oxidation performance. Approximately 86.6% of Hg0 was oxidized and energy yield reached 32.9µgkJ−1 at 2.6JL−1 and 110°C . The combined system widened the temperature windows of CeO2-WO3/TiO2 catalyst (80–300°C), showed good resistance to H2O and SO2, and also overcame the inhibitory effect of NO on Hg0 oxidation in the plasma system·NH3 inhibited the Hg0 oxidation; however, the coexistence of NO with NH3 significantly mitigated the inhibition. In the combined system, the CeO2-WO3/TiO2 catalyst could catalytically decompose the ozone generated by gas discharge, and increased the production of high adsorbed active oxygen, which was favorable for Hg0 oxidation process. The Hg0 oxidation process followed the homogeneous reaction mechanism and the Mars-Maessen mechanism in NTP injection system and CeO2-WO3/TiO2 system, respectively.

Modular Flow-Through Platform for Spectroelectrochemical Analysis.

A new type of flow platform for electrochemical and spectroelectrochemical measurements is presented. Finite element method simulations confirm that the hydrodynamic profile within the device is not turbulent and provides an analytical platform for the investigation of homogeneous kinetics, radical lifetimes, and reaction mechanisms. The modular "plug and play" configuration of the platform allows one to carry out electrochemistry and spectroscopy individually or simultaneously. Specific demonstrations of electroanalytical measurements using the flow system platform includes voltammetric analysis of organometallic compounds and quantitative analysis of ascorbic acid in commercial orange juice samples. Combined spectroelectrochemical demonstrations include electrochemical luminescence of ruthenium compounds and ligand exchange reactions of iron complexes using UV-vis spectroscopy.

Study on the Extraction Kinetics of Ketoconazole with Hydroxypropyl-β-Cyclodextrin as a Selector

This paper reports on the kinetics of extraction of ketoconazole enantiomers in a Lewis cell, which accompanies by an inclusion reaction. The mass transfer model of the extraction process is established based on the homogeneous reaction mechanism and two-film theory. Factors such as stirring speed, phase contact area, and ketoconazole concentration are separately investigated. The obtained data show the inclusion reaction is a fast reaction. The reactions have been found to be first order for ketoconazole enantiomers and second order for hydroxypropyl-β-cyclodextrin with forward rate constants of 1.716 × 10−3 m6/(mol2·s) for (−)-ketoconazole and 2.067 × 10−3 m6/(mol2·s) for (+)-ketoconazole.

Kinetic interplay between hydrogen and carbon monoxide in syngas-fueled catalytic micro-combustors

The combined oxidation of hydrogen and carbon monoxide over platinum in micro-combustors at catalytic surface temperatures below 600 K was studied numerically, using a two-dimensional computational fluid dynamics (CFD) model with detailed heterogeneous and homogeneous reaction mechanisms and multicomponent transport. Simulations were performed at different surface temperatures and feed compositions to study the kinetic interplay between hydrogen and carbon monoxide. A sensitivity analysis of the heterogeneous reaction mechanism was performed to identify the rate-controlling steps. Finally, possible mechanisms for the observed behavior were discussed. It was shown that there is significant kinetic interplay between hydrogen and carbon monoxide. Carbon monoxide significantly inhibits the catalytic oxidation of hydrogen. In contrast, the presence of hydrogen was found to promote the catalytic oxidation of carbon monoxide, with the largest effect shown for the small addition of hydrogen, then this effect progressively decreases with the further increase of hydrogen concentration. Accordingly, the apparent reaction order with respect to hydrogen changes from positive to negative, then to zero. The promoting effect of hydrogen can be attributed to the carboxyl pathway, which is crucial to describe the process.