Simple Reaction Scheme Research Articles

A Simplified Model for Prediction of Molecular Weight Distributions in Ethylene‐Hexene Copolymerization Using Ziegler‐Natta Catalysts

AbstractA simplified steady‐state model has been developed to predict molecular weight distributions and average compositions of ethylene‐hexene copolymers produced using heterogeneous Ziegler‐Natta catalysts in gas‐phase reactors. The model uses a simplified reaction scheme to limit the number of parameters that must be estimated. The number of parameters is further reduced by assuming that different types of active sites share common rate constants for some reactions. Estimates of kinetic parameters are obtained using deconvolution analysis of industrial copolymer samples produced using a variety of isothermal steady‐state operating conditions. The parameter estimates should prove useful as initial guesses for future parameter estimation in a non‐isothermal model.magnified image

Deterministic and stochastic models of enzymatic networks—applications to pharmaceutical research

The intracellular transducing device consists of complex networks of enzymatic reactions. Unfortunately, the mathematical models commonly used to describe them are still unsatisfactory and unreliable, even at the level of reproducing simple reaction schemes. The improvement of mathematical models is necessary and can follow different approaches still poorly employed, such as the modeling of spatial structures and phenomena, time delays, stochastic perturbations, only to cite the most relevant ones. In this paper we show some recent results related to the total quasi-steady-state approximation (tQSSA), in a deterministic scenario. Moreover, we show some possible applications of the tQSSA in a stochastic scheme.

Kinetic Study of the Thermal Oxidation of p-Xylene to Terephthaldehyde

Thermal oxidation of p-xylene to terephthaldehyde (TPAL) was investigated in a tubular reactor at 1 bar with various reaction variables, that is, temperature (803−863K), space time (10620−46980 L·s/mol), and feed concentration of p-xylene (2500 and 7500 ppm). A kinetic modeling was performed on the basis of a power-law rate equation using a proposed simplified molecular reaction scheme. The reaction scheme consists of three reaction pathways: (1) p-xylene to p-tolualdehyde (PTAL), (2) p-xylene to TPAL, and (3) p-xylene to COx (CO and CO2). Model parameters were estimated from the experimental data through minimization of the objective function. The activation energy for the formation of TPAL from p-xylene was 49.2 kJ/mol. The order of reaction was approximated to zero with respect to partial pressure of p-xylene. The kinetic model yields an excellent fit of the experimental data.

Unified Interpretation of Exciplex Formation and Marcus Electron Transfer on the Basis of Two-Dimensional Free Energy Surfaces

The mechanism of exciplex formation proposed in a previous paper has been refined to show how exciplex formation and Marcus electron transfer (ET) in fluorescence quenching are related to each other. This was done by making simple calculations of the free energies of the initial (DA*) and final (D+A-) states of ET. First it was shown that the decrease in D-A distance can induce intermolecular ET even in nonpolar solvents where solvent orientational polarization is absent, and that it leads to exciplex formation. This is consistent with experimental results that exciplex is most often observed in nonpolar solvents. The calculation was then extended to ET in polar solvents where the free energies are functions of both D-A distance and solvent orientational polarization. This enabled us to discuss both exciplex formation and Marcus ET in the same D-A pair and solvent on the basis of 2-dimensional free energy surfaces. The surfaces contain more information about the rates of these reactions, the mechanism of fluorescence quenching by ET, etc., than simple reaction schemes. By changing the parameters such as the free energy change of reaction, solvent dielectric constants, etc., one can construct the free energy surfaces for various systems. The effects of free energy change of reaction and of solvent polarity on the mechanism and relative importance of exciplex formation and Marcus ET in fluorescence quenching can be well explained. The free energy surface will also be useful for discussion of other phenomena related to ET reactions.

A comparative study of TiO 2 supported noble metal catalysts for the oxidation of formaldehyde at room temperature

The TiO 2 supported noble metal (Au, Rh, Pd and Pt) catalysts were prepared by impregnation method and characterized by means of X-ray diffraction (XRD) and BET. These catalysts were tested for the catalytic oxidation of formaldehyde (HCHO). It was found that the order of activity was Pt/TiO 2 ≫ Rh/TiO 2 > Pd/TiO 2 > Au/TiO 2 ≫ TiO 2. HCHO could be completely oxidized into CO 2 and H 2O over Pt/TiO 2 in a gas hourly space velocity (GHSV) of 50,000 h −1 even at room temperature. In contrast, the other catalysts were much less effective for HCHO oxidation at the same reaction conditions. HCHO conversion to CO 2 was only 20% over the Rh/TiO 2 at 20 °C. The Pd/TiO 2 and Au/TiO 2 showed no activities for HCHO oxidation at 20 °C. The different activities of the noble metals for HCHO oxidation were studied with respect to the behavior of adsorbed species on the catalysts surface at room temperature using in situ DRIFTS. The results show that the activities of the TiO 2 supported Pt, Rh, Pd and Au catalysts for HCHO oxidation are closely related to their capacities for the formation of formate species and the formate decomposition into CO species. Based on in situ DRIFTS studies, a simplified reaction scheme of HCHO oxidation was also proposed.

The antimalarial drugs quinine, chloroquine and mefloquine are antagonists at 5‐HT3 receptors

The antimalarial compounds quinine, chloroquine and mefloquine affect the electrophysiological properties of Cys-loop receptors and have structural similarities to 5-HT(3) receptor antagonists. They may therefore act at 5-HT(3) receptors. The effects of quinine, chloroquine and mefloquine on electrophysiological and ligand binding properties of 5-HT(3A) receptors expressed in HEK 293 cells and Xenopus oocytes were examined. The compounds were also docked into models of the binding site. 5-HT(3) responses were blocked with IC (50) values of 13.4 microM, 11.8 microM and 9.36 microM for quinine, chloroquine and mefloquine. Schild plots indicated quinine and chloroquine behaved competitively with pA (2) values of 4.92 (K (B)=12.0 microM) and 4.97 (K (B)=16.4 microM). Mefloquine displayed weakly voltage-dependent, non-competitive inhibition consistent with channel block. On and off rates for quinine and chloroquine indicated a simple bimolecular reaction scheme. Quinine, chloroquine and mefloquine displaced [(3)H]granisetron with K (i) values of 15.0, 24.2 and 35.7 microM. Docking of quinine into a homology model of the 5-HT(3) receptor binding site located the tertiary ammonium between W183 and Y234, and the quinoline ring towards the membrane, stabilised by a hydrogen bond with E129. For chloroquine, the quinoline ring was positioned between W183 and Y234 and the tertiary ammonium stabilised by interactions with F226. This study shows that quinine and chloroquine competitively inhibit 5-HT(3) receptors, while mefloquine inhibits predominantly non-competitively. Both quinine and chloroquine can be docked into a receptor binding site model, consistent with their structural homology to 5-HT(3) receptor antagonists.

Effect of stratospheric O 3 depletion on tropospheric SO 2 column in Antarctica

When ozone is depleted in the stratosphere during ozone-hole period, UV-B radiation, which is normally absorbed in this region, penetrates into the troposphere. As a result, the behavior of several species in the troposphere, which interact with UV-B radiation, is likely to change. Sulfur dioxide is predominantly found in the troposphere. To study the behavior of sulfur dioxide during this event, a Brewer spectrophotometer was installed at Maitri (70.7°S, 11.7°E) in Antarctica in July 1999. With this instrument, the vertical column density of SO 2 was measured from September 1999 to December 2003. We have observed an increase in SO 2 column density during an ozone-hole event. The magnitude of increase is different in different years, on average, by a factor of ∼5 (from ∼0.5 to ∼2.5 DU). Simultaneously, the maximum value of UV-B flux at the ground was also measured. We have observed that during the ozone-hole period, the UV-B flux also increased by different amounts during different years, by a factor of ∼3–5. Good correlation has been found between SO 2 column and UV-B flux but no correlation has been found between O 3 column and UV-B flux from the middle of September to the middle of November. Using a simple steady-state chemical reaction scheme, an attempt has been made to examine whether the increase in UV-B flux could increase the SO 2 column during the ozone-hole period.

A detailed chemistry model for transient hydrogen and carbon monoxide catalytic recombination on parallel flat Pt surfaces implemented in an integral code

A detailed chemistry model has been adapted and developed for surface chemistry, heat and mass transfer between H 2/CO/air/steam/CO 2 mixtures and vertical parallel Pt-coated surfaces. This model is based onto a simplified Deutschmann reaction scheme for methane surface combustion and the analysis by Elenbaas for buoyancy-induced heat transfer between parallel plates. Mass transfer is treated by the heat and mass transfer analogy. The proposed model is able to simulate the H 2/CO recombination phenomena characteristic of parallel-plate Passive Autocatalytic Recombiners (PARs), which have been proposed and implemented as a promising hydrogen-control strategy in the safety of nuclear power stations or other industries. The transient model is able to approach the warm-up phase of the PAR and its shut-down as well as the dynamic changes within the surrounding atmosphere. The model has been implemented within the MELCOR code and assessed against results of the Battelle Model Containment tests of the Zx series. Results show accurate predictions and a better performance than traditional methods in integral codes, i.e. empirical correlations, which are also much case-specific. Influence of CO present in the mixture on the PAR performance is also addressed in this paper.

The Galactose Switch in Kluyveromyces lactis Depends on Nuclear Competition between Gal4 and Gal1 for Gal80 Binding

The Gal4 protein represents a universally functional transcription activator, which in yeast is regulated by protein-protein interaction of its transcription activation domain with the inhibitor Gal80. Gal80 inhibition is relieved via galactose-mediated Gal80-Gal1-Gal3 interaction. The Gal4-Gal80-Gal1/3 regulatory module is conserved between Saccharomyces cerevisiae and Kluyveromyces lactis. Here we demonstrate that K. lactis Gal80 (KlGal80) is a nuclear protein independent of the Gal4 activity status, whereas KlGal1 is detected throughout the entire cell, which implies that KlGal80 and KlGal1 interact in the nucleus. Consistently KlGal1 accumulates in the nucleus upon KlGAL80 overexpression. Furthermore, we show that the KlGal80-KlGal1 interaction blocks the galactokinase activity of KlGal1 and is incompatible with KlGal80-KlGal4-AD interaction. Thus, we propose that dissociation of KlGal80 from the AD forms the basis of KlGal4 activation in K. lactis. Quantitation of the dissociation constants for the KlGal80 complexes gives a much lower affinity for KlGal1 as compared with Gal4. Mathematical modeling shows that with these affinities a switch based on competition between Gal1 and Gal4 for Gal80 binding is nevertheless efficient provided two monomeric Gal1 molecules interact with dimeric Gal80. Consistent with such a mechanism, analysis of the sedimentation behavior by analytical ultracentrifugation demonstrates the formation of a heterotetrameric KlGal80-KlGal1 complex of 2:2 stoichiometry.

06/02080 NO x, formation in natural gas combustion - a new simplified reaction scheme for CFD calculations : Löffler, G. et al. Fuel, 2006, 85, (4), 513–523.

06/02080 NO x, formation in natural gas combustion - a new simplified reaction scheme for CFD calculations : Löffler, G. et al. Fuel, 2006, 85, (4), 513–523.

Experimental and detailed kinetic modeling study of the high pressure oxidation of methanol sensitized by nitric oxide and nitrogen dioxide

The perturbation of the combustion by NO x is important in several practical systems (recent NO x -reduction strategies, combustion with exhaust-gas recirculation in diesel and HCCI engines and for mild combustion). New experimental results were obtained for the oxidation of methanol in absence and in presence of NO or NO 2 in a fused silica jet-stirred reactor operating at 10 atm, over the temperature range 700–1100 K. Probe sampling followed by on-line FTIR analyses and off-line GC-TCD/FID analyses permitted to measure the concentration profiles of the reactants, stable intermediates and the final products. A detailed chemical kinetic modeling of the present experiments was performed. An overall good agreement between the present data and this modeling was obtained. The oxidation of methanol is significantly sensitized by NO 2, whereas the effect of NO is more limited. According to the proposed model, the mutual sensitization of the oxidation of methanol and NO proceeds through the NO to NO 2 conversion by HO 2. The increased production of OH resulting from the oxidation of NO by HO 2 promotes the oxidation of the fuel. A simplified reaction scheme can be proposed for the NO-seeded oxidation of methanol: NO + HO 2 ⇒ NO 2 + OH followed by OH + CH 3OH ⇒ H 2O + CH 2OH and CH 3O. The enhanced oxidation of methanol by addition of NO 2 is also due to additional OH production through: NO 2 + HO 2 ⇒ HONO + O 2, NO 2 + H ⇒ NO + OH and HONO ⇒ NO + OH followed by OH + CH 3OH ⇒ CH 2OH and CH 3O. The further reactions CH 2OH + O 2 ⇒ CH 2O + HO 2; CH 3O ⇒ CH 2O + H; CH 2O + OH ⇒ HCO; HCO + O 2 ⇒ HO 2 and H + O 2 ⇒ HO 2 complete the sequence whether NO or NO 2 is added.

Traveling ion channel density waves affected by a conservation law

A model of mobile, charged ion channels embedded in a biomembrane is investigated. The ion channels fluctuate between an opened and a closed state according to a simple two-state reaction scheme whereas the total number of ion channels is a conserved quantity. Local transport mechanisms suggest that the ion channel densities are governed by electrodiffusionlike equations that have to be supplemented by a cable-type equation describing the dynamics of the transmembrane voltage. It is shown that the homogeneous distribution of ion channels may become unstable to either a stationary or an oscillatory instability. The nonlinear behavior immediately above threshold of an oscillatory bifurcation occurring at finite wave number is analyzed in terms of amplitude equations. Due to the conservation law imposed on ion channels, large-scale modes couple to the finite-wave-number instability and have thus to be included in the asymptotic analysis near the onset of pattern formation. A modified Ginzburg-Landau equation extended by long-wavelength stationary excitations is established, and it is highlighted how the global conservation law affects the stability of traveling ion channel density waves.

AN EQUATION-FREE APPROACH TO NONLINEAR CONTROL: COARSE FEEDBACK LINEARIZATION WITH POLE-PLACEMENT

We present an application of equation-free computation to the coarse-grained feedback linearization problem of nonlinear systems described by microscopic/stochastic simulators. Feedback linearization with pole placement requires the solution of a functional equation involving the macroscopic (coarse-grained) system model. In the absence of such a closed-form model, short, appropriately initialized bursts of microscopic simulation are designed and performed, and their results used to estimate on demand the quantities required for the numerical solution of the (explicitly unavailable) functional equation. Our illustrative example is a kinetic Monte Carlo realization of a simplified heterogeneous catalytic reaction scheme.

Receptor-Agonist Interactions in Service-Theoretic Perspective, Effects of Molecular Timing on the Shape of Dose-Response Curves

Service-theoretic concepts and methods, widely used in other fields (e.g., telecommunication and operations research), are useful also in a biochemical setting because the treatment of biocatalysts (enzymes, receptors) as servers and their ligands as customers, based on the established formal methods of service or queuing theory, may lead to insights and results unobtainable by conventional, mass-action-law-based theories. In this article, we apply the service-theoretic approach to receptor-agonist systems and show how by changing the stochastic time pattern of “operationally relevant” point events (e.g., instants of agonist arrival, instants of postclimax agonist departure) a great variety of dose-response curves may be generated, even in very simple reaction schemes, which, according to mass action kinetics, invariably lead to hyperbolic r(A) curves (r and A stand for response and agonist concentration, respectively). The molecular timing inherent to a hyperbolic response system is not optimal: for instance, at the agonist concentration A50, half of the agonist molecules are rejected (“lost”) because of unfortunate timing of the arrival events. The fraction of lost arrivers can be diminished considerably if the arrivals are better timed: “sub-Poisson” arrivals improve the timing and, thus, convert hyperbolic r(A) curves into “lifted” nonhyperbolic ones. Conversely, “super-Poisson” arrivals make the nonoptimal timing in hyperbolic response systems even worse and, thus, convert hyperbolic r(A) curves into “depressed” nonhyperbolic ones. Furthermore, under special timing conditions, nonhyperbolic r(A) curves can be generated, which are partly lifted, partly depressed relative to the reference hyperbola, and which resemble in shape well-known nonhyperbolic forms of enzyme and receptor kinetics (negatively cooperative, positively cooperative, and sigmoidal kinetics). In addition unusual (undulatory and sawtooth-like) r(A) curves can be generated solely by changing the temporal pattern of arrival and service completion instants. Virtually any shape of dose-response curves may be obtained by allowing for probability distributions whose characteristic shape varies with their mean; we call such distributions“variomorphic” and apply them to the arrival process of agonist molecules.

Lower hepatitis C virus infections in seropositive patients between 1999 and 2003

Progress in the development of carbon nanotubes (CNTs) has stimulated great interest among industries providing new applications. Meanwhile, toxicological evaluations on nanomaterials are advancing leading to a predictive exposure limit for CNTs, which implies the possibility of designing safer CNTs. To pursue safety by design, the redox potential in reactions with CNTs has been contemplated recently. However, the chemical reactivity of CNTs has not been explored kinetically, so that there is no scheme to express a redox reaction with CNTs, though it has been investigated and reported. In addition, the reactivity of CNTs is discussed with regard to impurities that consist of transition metals in CNTs, which obfuscates the contribution of CNTs to the reaction. The present work aimed at modeling CNT scavenging in aqueous solution using a kinetic approach and a simple first-order reaction scheme. The results show that CNTs follow the redox reaction assumption in a simple chemical system. As a result, the reaction with multiwalled CNTs is semiquantitatively denoted as redox potential, which suggests that their biological reactions may also be evaluated using a redox potential scheme.

Mutual Sensitization of the Oxidation of Nitric Oxide and a Natural Gas Blend in a JSR at Elevated Pressure: Experimental and Detailed Kinetic Modeling Study

The mutual sensitization of the oxidation of NO and a natural gas blend (methane-ethane 10:1) was studied experimentally in a fused silica jet-stirred reactor operating at 10 atm, over the temperature range 800-1160 K, from fuel-lean to fuel-rich conditions. Sonic quartz probe sampling followed by on-line FTIR analyses and off-line GC-TCD/FID analyses were used to measure the concentration profiles of the reactants, the stable intermediates, and the final products. A detailed chemical kinetic modeling of the present experiments was performed yielding an overall good agreement between the present data and this modeling. According to the proposed kinetic scheme, the mutual sensitization of the oxidation of this natural gas blend and NO proceeds through the NO to NO2 conversion by HO2, CH3O2, and C2H5O2. The detailed kinetic modeling showed that the conversion of NO to NO2 by CH3O2 and C2H5O2 is more important at low temperatures (ca. 820 K) than at higher temperatures where the reaction of NO with HO2 controls the NO to NO2 conversion. The production of OH resulting from the oxidation of NO by HO2, and the production of alkoxy radicals via RO2 + NO reactions promotes the oxidation of the fuel. A simplified reaction scheme was delineated: NO + HO2 --> NO2 + OH followed by OH + CH4 --> CH3 + H2O and OH + C2H6 --> C2H5 + H2O. At low-temperature, the reaction also proceeds via CH3 + O2 (+ M) --> CH3O2 (+ M); CH3O2 + NO --> CH3O + NO2 and C2H5 + O2 --> C2H5O2; C2H5O2 + NO --> C2H5O + NO2. At higher temperature, methoxy radicals are produced via the following mechanism: CH3 + NO2 --> CH3O + NO. The further reactions CH3O --> CH2O + H; CH2O + OH --> HCO + H2O; HCO + O2 --> HO2 + CO; and H + O2 + M --> HO2 + M complete the sequence. The proposed model indicates that the well-recognized difference of reactivity between methane and a natural gas blend is significantly reduced by addition of NO. The kinetic analyses indicate that in the NO-seeded conditions, the main production of OH proceeds via the same route, NO + HO2 --> NO2 + OH. Therefore, a significant reduction of the impact of the fuel composition on the kinetics of oxidation occurs.

Reactions of trans-[RuCl 2(CO) 2(PEt 3) 2] with 1,1-dithiolates: Stepwise formation of cis-[Ru(CO)(PEt 3)(S 2X)] (X = CNMe 2, CNEt 2, COEt, P(OEt) 2, PPh 2)

Trans-[RuCl 2(CO) 2(PEt 3) 2] reacts with two equivalents of a series of 1,1-dithiolate ligands to form the bis(dithiolate) complexes, cis-[Ru(CO)(PEt 3)(S 2X) 2] (X = CNMe 2, CNEt 2, COEt, P(OEt) 2, PPh 2). Two intermediates have been isolated; trans-[Ru(PEt 3) 2Cl(CO){S 2P(OEt) 2}] and trans-[Ru(PEt 3) 2(CO)(η 1-S 2COEt)(η 2-S 2COEt)], allowing a simple reaction scheme to be postulated involving three steps; (i) initial replacement of cis carbonyl and chloride ligands, (ii) substitution of the second chloride, (iii) loss of a phosphine. Thermolysis of cis-[Ru(CO)(PEt 3)(S 2CNMe 2) 2] with Ru 3(CO) 12 in xylene affords trinuclear [Ru 3(μ 3-S) 2(PEt 3)(CO) 8] as a result of dithiocarbamate degradation. Crystal structures of cis-[Ru(CO)(PEt 3)(S 2X) 2] (X = NMe 2, COEt), trans-[Ru(PEt 3) 2Cl(CO){S 2P(OEt) 2}], trans-[Ru(PEt 3) 2(CO)(η 1-S 2COEt)(η 2-S 2COEt)] and [Ru 3(μ 3-S) 2(PEt 3)(CO) 8] are reported.

Mathematical modelling of the injection of coke oven gas into a blast furnace tuyere

A fundamental mathematical model of the tuyere in a blast furnace has been developed earlier. In this study, the model is mainly used to predict the combustion reactions in the tuyere when coke oven gas is injected through lances located inside the tuyere. The combustion reaction is modelled using a simple reaction scheme with 3 possible reactions that can occur. The influence of the following parameters on the predicted velocities, temperatures and composition of the gas at the tuyere outlet is studied in this paper: (i) injection amount of coke oven gas, (ii) the use of 1 or 2 injection lances and (iii) the influence of the injection angles when using 2 injection lances. It is concluded that the maximum injecting amount using 1 and 2 lances is 10,000 nm3/h and 15,000 m3/h, respectively. The combustion conditions are better when using 2 injection lances are compared to 1 injection lance and the predicted results are not affected to a large degree when the injection angles are changed.

Ultrafast and Low Barrier Motions in the Photoreactions of the Green Fluorescent Protein

Green fluorescent protein (GFP) fluoresces efficiently under blue excitation despite major electrostatic rearrangements resulting from photoionization of the chromophore and neutralization of Glu-222. A competing phototransformation process, which ionizes the chromophore and decarboxylates Glu-222, mimics the electrostatic and structural changes in the fluorescence photocycle. Structural and spectroscopic analysis of the cryogenically stabilized photoproduct at 100 K and a structurally annealed intermediate of the phototransformed protein at 170 K reveals distinct structural relaxations involving protein, chromophore, solvent, and photogenerated CO2. Strong structural changes of the 100 K photoproduct after decarboxylation appear exclusively within 15 angstroms of the chromophore and include the electrostatically driven perturbations of Gln-69, Cys-70, and water molecules in an H-bonding network connecting the chromophore. X-ray crystallography to 1.85 angstroms resolution and static and picosecond time-resolved IR spectroscopy identify structural mechanisms common to phototransformation and to the fluorescence photocycle. In particular, the appearance of a 1697 cm(-1) (+) difference band in both photocycle and phototransformation intermediates is a spectroscopic signature for the structural perturbation of Gln-69. This is taken as evidence for an electrostatically driven dynamic response that is common to both photoreaction pathways. The interactions between the chromophore and the perturbed residues and solvent are decreased or removed in the T203H single and T203H/Q69L double mutants, resulting in a strong reduction of the fluorescence quantum yield. This suggests that the electrostatic response to the transient formation of a buried charge in the wild type is important for the bright fluorescence.

NO x formation in natural gas combustion—a new simplified reaction scheme for CFD calculations

Computational fluid dynamics is a widely used tool in optimizing natural gas burners, for instance, for emission issues. Especially, a further reduction of NO x emissions is of interest. However, due to computational efforts calculating three-dimensional turbulent flames, there is the necessity for simplified models in order to simulate the combustion reactions and the NO x formation, respectively. Hitherto, models describing thermal NO and prompt NO formation, respectively, were applied in a post-processing step. Beforehand, the flow field including combustion has been determined in the three-dimensional geometry. However, in the former work, it was shown that prompt NO formation is of minor significance. For temperatures higher than 1600 °C, thermal NO formation is dominating. At lower temperatures, the N 2O/NO and NNH route have significant contribution. Though, the widely applied prompt NO model captures the observed trends acceptable, it lacks of physical bases. Besides low temperature NO formation is more related to N 2O/NO and NNH route, it assumes the prompt NO formation to be proportional to the fuel concentration. The detailed reaction mechanism show NO formation more related to fuel oxidation rate, i.e. radical concentration. Thus, in this work, a new simplified model combining thermal NO formation, N 2O/NO, and NNH route is proposed. It applies steady-state approximation for the intermediate species, i.e. N, N 2O, NNH, and NH. In this way, their concentrations can be obtained by four algebraic equations and rate of NO formation can be calculated without any model parameter, solely based on reaction kinetics. Moreover, the concentrations of O 2, N 2, H 2, and H 2O as well as the radicals O, H, OH, and HO 2 have to be known from combustion calculations. The model was evaluated against the predictions of a detailed reaction mechanism, showing good agreement in a wide range of conditions. Neglecting prompt NO formation affects predicted NO emissions only under very fuel rich conditions. Under these circumstances, total NO formation is low, anyway. Thus, the performance of the presented model is not influenced by the lack of prompt NO formation.