Global Activation Energy Research Articles

Thermal Decomposition of Erythritol Tetranitrate: A Joint Experimental and Computational Study

Pentaerythritol tetranitrate (PETN) finds many uses in the energetic materials community. Due to the recent availability of erythritol, erythritol tetranitrate (ETN) can now be readily synthesized. Accordingly, its complete characterization, especially its stability, is of great interest. This work examines the thermal decomposition of ETN, both through experimental and computational methods. In addition to kinetic parameters, decomposition products were examined to elucidate its decomposition pathway. It is found that ETN begins its decomposition sequence by a unimolecular homolytic cleavage of the internal and external O–NO2 bonds, while the competing HONO elimination reaction is largely suppressed. The global activation energy for decomposition is found to be 104.3 kJ/mol with a pre-exponential factor of 3.72 × 109 s–1. Despite the ability to exist in a molten state, ETN has a lower thermal stability than its counterpart PETN.

Recovery of clean energy precursors from Bambara groundnut waste via pyrolysis: Kinetics, products distribution and optimisation using response surface methodology

This study presents first comprehensive thermochemical analysis of Bambara groundnut shell. Pyrolysis characteristics was examined under non-isothermal degradation in nitrogen atmosphere at different heating rates (10, 15 and 20 °C/min) using single-step global model kinetic model. The single-step global model average apparent activation energy was found to be 142.64 ± 5.7 kJ/mol. Pyrolysis was conducted in a fixed bed reactor. Effects of pyrolysis temperature (450–750 °C), heating rate (20–50 °C/min) and nitrogen flow rate (5–25 L/min) were investigated collectively. The process variables were optimized using response surface methodology with central composite design. Optimum bio-oil yield of 36.49 wt% was recorded at 600 °C, 50 °C/min and 11 L/min. The bio-oil, bio-char and non-condensable gas collected were comprehensively characterised. Energy analysis of the products was also evaluated. This study revealed that Bambara groundnut shell, a residue from food crop, is a potential source of energy precursors for development of a sustainable bioenergy system and biomaterials.

An ignition delay time and chemical kinetic study of ethane sensitized by nitrogen dioxide

Nitrogen dioxide (NO2) is a dominant component of NOx pollution in combustion of internal combustion engines and gas turbines. Its sensitization on ignition of ethane which is a main component of natural gas has been investigated in this experimental and kinetic study. Ignition delay times of NO2/C2H6/O2/Ar mixtures, with blending ratios of NO2:C2H6 of 0.3:1 and 1:1, were measured in a shock tube. Experimental conditions cover a range of pressures (1.2–20atm), temperatures (950–1700K) and equivalence ratios (0.5–2.0). Similarly to our previous work of CH4/NO2 (Deng et al., 2016) [14], NO2 addition promotes the reactivity of ethane and reduces the global activation energy particularly at higher pressures (p>5.0atm) and lower temperatures (T<1175K), whereas it only presents a limited effect at low pressure (1.0atm) and higher temperatures (T>1175K). Furthermore, an opposite effect of NO2 addition is observed in both the experiments and the simulations at different temperature regimes. Compared to fuel-rich mixture, NO2 addition exhibits more significantly promoting effect on the ignition of fuel-lean mixture under given NO2 concentration. Four literature kinetic mechanisms and an updated mechanism proposed in this study have been compared to simulate the new ignition delay time data and the literature data. Overall, the proposed model is capable of reproducing the experimental results measured by various facilities over a wide range of conditions. The proposed model is thus used to carry out the sensitivity and flux analyses to clarify the chemistry interaction between NO2 and ethane. Based on the kinetic analyses, the impact of NO2 has been expounded at different conditions.

CFD based reactivity parameter determination for biomass particles of multiple size ranges in high heating rate devolatilization

This work presents a methodology that combines experimental measurements and Computational Fluid Dynamics (CFD) modeling to determine the global reaction kinetics of high heating rate biomass devolatilization. Three particle size ranges of woody biomass are analyzed: small (SF), medium (MF) and large (LF) fractions. Devolatilization mass loss is measured for each fraction in a laminar Drop-Tube Reactor (DTR) in nitrogen atmosphere, using two nominal reactor temperatures of 873 and 1173 K. Single First Order Reaction (SFOR) kinetics are determined by coupling an optimization routine with CFD models of the DTR. The global pre-exponential factors and activation energies for the SF, MF and LF particles are 5880 1/s and 42.7 kJ/mol, 48.1 1/s and 20.2 kJ/mol, and 102 1/s and 24.8 kJ/mol, respectively. These parameters are optimized for the isothermal heat transfer model available in CFD programs, and it is recommended that the specific heat capacity that was used in the optimization (1500 J/kgK) is used together with the parameters. Using the SF kinetics for small wood particles and either of the MF or LF kinetics for large particles, it is expected that more accurate devolatilization predictions can be obtained for the whole fuel size distribution in large scale CFD simulations.

Catalytic Steam Cracking of a Deasphalted Vacuum Residue Using a Ni/K Ultradispersed Catalyst

Catalytic steam cracking (CSC) of heavy hydrocarbons is seen as an alternative for further improvement upon conventional thermal cracking performance. In this work, upgrading of an industrial deasphalted vacuum residue via CSC was assessed in a bench-scale pilot plant resembling a visbreaking unit. The performance of a 400 ppm of Ni and 300 ppm K ultradispersed catalyst (UDC) formulation previously used for CSC of vacuum residue was evaluated for this nonasphaltene containing fraction. Reactivity experiments were conducted at temperatures within 435–445 °C and liquid hourly space velocities (LHSV) of 3–5.5 h–1 and operating pressure of 300 psig. A preliminary reactivity evaluation using isotopic water spanning temperatures between 423 and 445 °C was carried out to determine the conditions at which water splitting was occurring. Finally, lumped kinetic modeling including asphaltenes generation in the process was evaluated, and results were compared with previously reported thermal cracking experiments. Operating variables (T, LHSV) were found to have similar effects on the reactivity, as in thermal cracking for CSC of DAO. Even though water splitting was evidenced at temperatures above 430 °C, no significant improvement in the physical bulk properties of the liquid products was obtained for the catalytic experiments using the current formulation. This is attributed to the high degree of condensation reactions triggered at the range of temperatures evaluated. A global activation energy for the conversion of DAO (560 °C+) of 175 kJ/mol and a modeling error of 4.23% were determined. Asphaltenes generation was evidenced at a similar extent as that of thermal cracking from a kinetic point of view.

The reduction kinetics of hematite particles in H2 and CO atmospheres

The reduction characteristics of hematite particles (i.e., Fe2O3) in H2 and CO atmospheres were experimentally investigated using isothermal thermo-gravimetric analysis (TGA). The mean diameter of the hematite powder (dP,m) was about 0.74μm. A mixture of pure hydrogen (H2) and carbon monoxide (CO) gases was used as a reductant at a fixed flow rate of 0.1lpm. Nitrogen (N2) was used as a diluent gas to control the mole fraction of the reductive mixture. The temperature for hematite particle reduction in the TGA (TR) was varied from 550 to 1300°C. Experimental results showed an increase in the reduction rate of iron oxide particles with an increase in the reductant mole fraction and surrounding temperature. The reduced particles displayed a sticking behavior at TR=1050 and 1300°C. The phenomenon of particle swelling was observed in a CO atmosphere. The global activation energy of the iron oxide particles was measured as 43.5kJ/mol for a H2 atmosphere and 2.3kJ/mol for a CO atmosphere at TR=800–1300°C.

Propanol isomers: Investigation of ignition and pyrolysis time scales

This study presents an investigation of the ignition and pyrolysis kinetics of the two propanol isomers. Experiments are carried out behind reflected shock waves at average pressures of 3.5, 5.0, and 11 atm over a temperature range of 1150–1550 K. Oxidation experiments are carried out using mixtures with equivalence ratios of 0.5, 1.0, and 2.0. Laser absorption measurement of CO is carried out near 4.6 µm on the basis of which a characteristic pyrolysis time scale is defined. By means of this pyrolysis time scale, the effects of reactor temperature, pressure, and fuel concentration on pyrolysis are established. Contrast is further made between the global kinetics of pyrolysis and purely oxidative kinetics during ignition. The measured ignition and pyrolysis time scales are also compared with predictions of three chemical kinetic models from the literature. The expected lower reactivity of iso-propanol relative to n-propanol during ignition and pyrolysis is observed. The study also reveals a distinctly higher global temperature sensitivity of the pyrolysis process (global activation energy > 60 kcal/mol) compared to the typical global activation energy of ignition (global activation energy in the range of 20–40 kcal/mol). This difference leads to a cross-over effect at a characteristic reactor temperature between ignition that is controlled by pyrolysis and one that is controlled by predominantly oxidative kinetics. While this is observed for the chosen molecular systems, the cross-over effect is a general feature of high-temperature fuel reaction kinetics. At lower temperatures the chemical time scales of predominantly pyrolytic reactions are much longer than the time scales of oxidative radical processes which dominate the ignition process whereas at higher temperatures the time scales of pyrolytic processes become shorter and dominate the global ignition kinetics. Selected CO concentration profiles obtained during pyrolysis are also compared with predictions of current chemical kinetic models, revealing varying degrees of agreement and discrepancies among the models. The study advances characterization of propanol combustion and demonstrates the use of global chemical time scales to characterize fuel pyrolysis kinetics.

Shock tube study on ignition delay of hydrogen and evaluation of various kinetic models

H2/O2 chemistries are of great crucial for all hydrocarbon and syngas oxidations. Recent study showed that presence of residual H-atom in shock tubes may heavily influences experimental determination of ignition delay times in H2/O2 mixtures. Although numerous studies of hydrogen ignition delay times were reported, none of them discussed the residual H-atom in their studies which may impact the accuracy of their measurements. In this study, a systematic measurement related to the ignition delay times were conducted for H2/O2 mixtures diluted with argon over the temperatures from 850 K to 1500 K, the pressures from 1.2 to 16.0 atm, and the equivalence ratios of 0.5, 1.0 and 2.0. Special attentions were paid to eliminate the influence of residual H-atom on ignition delay time and the calculation showed that the residual H-atom in current shock tube shows no obvious effect on ignition delay time, which guarantees the present data more convincing. The measurements showed that the hydrogen mixtures have different global activation energies under different pressures. Thus, correlations were derived under different pressures based on all experimental data, which fit fairly well with the experimental data. A couple of detailed kinetic models from literature were validated against the present experimental results. The result shows that the mechanism of Kéromnès-2013 yields the best agreement with data from shock tube experiments at various pressures up to 16 atm, while Davis-2005, GRI 3.0, SanDiego-2011 and Li-2004 mechanisms present significant poor predictions at higher pressures. This investigation is contrary to the previous studies. Reaction pathway and sensitivity analysis indicated that reaction R10: H + O2 (+M) <=> HO2 (+M) is of significant important pressure-dependent reaction in controlling of hydrogen oxidation. It is inferred that significant differences of their rate constants among various mechanisms induce the difference of performance on hydrogen ignition predictions.

Pyrolysis of furan and its derivatives at 1100 °C: PAH products and DFT study

In this work, the pyrolysis of furans (furan, 2-methylfuran, furfuryl alcohol, and furfural) have been checked by Py-GC–MS at 1100°C to detect the decomposition of furans and the formation of benzene derivatives and PAH. From the Py-GC–MS results, different side chain functional groups on furan-ring lead to different kinds of products and product distributions, such as hydroxyl group leading to dimers, and aldehyde group leading to pyrans, but the mechanism for furan-ring opening and decomposition is universal for furans pyrolyzed in this study. In order to explain the experimental results and the formation of benzene derivatives and PAH, the formation of benzene from furan has also been calculated by B3LYP/6-31G++(d,p). Two possible benzene formation mechanisms, Diels-Alder and acetylene reaction mechanism, have been proposed and calculated. By comparison, it has been regarded that Diels-Alder reaction was more possible for PAH formation as this mechanism has a lower activation energy for initiation step, but acetylene reaction mechanism was more possible for benzene formation as this mechanism has a lower global activation energy.

Towards a kinetic understanding of the NOx promoting-effect on ignition of coalbed methane: A case study of methane/nitrogen dioxide mixtures

Nitrogen dioxide (NO2) is an important impurity in coal-bed methane (CBM) and a dominant component of NOx pollution in practical engines. Its promoting effect on methane ignition has been studied in the current experimental and kinetic study. Ignition delay times of NO2/CH4/O2/Ar mixtures, with blending ratios of NO2:CH4 of 30:70, 50:50 and 70:30 for stoichiometric methane mixtures were measured in a shock tube. Experiments cover a range of pressures (1.2–10.0atm) and temperatures (933–1961K). Under all tested pressures, NO2 addition promotes the reactivity of methane and reduces the global activation energy at all pressures, and these effects are most significant for the mixtures with highest NO2 concentrations, at the highest pressures and at the lowest temperatures. To simulate the experimental measurements, five literature NOx sub-mechanisms were integrated with AramcoMech 1.3. The simulations demonstrate that, for the mixtures with low levels of NOx concentrations, the five models agree well with the experimental ignition delay times. For the mixtures with high NOx content, however, all five models are unable to reproduce the measured data, and the level of disagreement increases with increasing NO2 concentration. An updated mechanism is proposed, based on modifications made as a result of sensitivity and reaction flux analyses performed to quantitatively determine the chemical reasons for NO2 promoting methane ignition. The results indicate that, NO2 addition perturbs the branching ratio of key reaction pathways by affecting the structure of the free radical pool at the initial ignition stage of methane oxidation. A new reaction cycle via the following sequence of reactions ĊH3+NO2⇔CH3Ȯ+NO, CH3Ȯ+M⇔CH2O+Ḣ+M, NO2+Ḣ⇔NO+ȮH, and CH4+ȮH⇔ĊH3+H2O is proposed to explain the observed effect of NO2 addition on the promotion of methane ignition.

Ignition Delay Time and Chemical Kinetic Study of Methane and Nitrous Oxide Mixtures at High Temperatures

Ignition delay times of N2O/CH4/O2/Ar mixtures with varying N2O mixing ratios (N2O/CH4 mole blending ratio = 0:100, 30:70, 50:50, and 70:30) were measured behind reflected shock waves at pressures of 1.2–16 atm, equivalence ratios of 0.5–2.0, and temperatures of 1220–2336 K. At currently investigated conditions, the reactivity of methane is significantly promoted by N2O addition, resulting in an obvious reduction of the ignition delay time, and this effect becomes more pronounced at the fuel-rich condition and high pressure. However, N2O addition only results in a slight reduction in the global activation energy. To eliminate the effect of different hydrocarbon mechanisms, a widely accepted kinetic mechanism, Aramco Mech 1.3, is used to combine with three available NOx submodels (Gersen et al., Konnov, and Mathieu et al.) and simulate the measured ignition delay times. Generally, the three assembled models give a similar prediction performance and agree well with the experimental data for a low level of N2O addition, but they exhibit a discrepancy for a high level of N2O addition. Sensitivity analysis and radical pool analysis are conducted to interpret the kinetic effect of N2O addition on methane ignition chemistry. Results indicate that the promoting effect of N2O addition on methane ignition is mainly attributed to the contribution of the following three reactions: N2O + M = N2 + O• • + M, N2O + H• = N2 + •OH, and N2O + •CH3 = CH3O• + N2, which can significantly increase the concentration of the radical pool and accelerate the peak of the radical pool.

Kinetic and thermodynamic analysis of the polymerization of polyurethanes by a rheological method

As part of an investigation into the mechanism and chemorheology of linear segmented polyurethane (PU) systems, this paper presents the kinetic and thermodynamic characterization of the reaction between an advanced functional metallo-polyol derivative of hydroxyl-terminated polybutadiene (HTPB), (ferrocenylbutyl)dimethylsilane grafted HTPB, and isophorone diisocyanate (IPDI). The evolution of viscoelastic properties, such as the storage modulus (G′), was recorded in bulk under isothermal conditions at four different temperatures between 50 and 80°C, and a resin curing degree profile was obtained for this elastic modulus. The use of the Kamal-Sourour autocatalytic kinetic model was proposed, describing the overall curing process perfectly. All the kinetic and thermodynamic parameters, including reaction orders, kinetic constants and activation energy, were determined for the polyaddition reaction under study. A relevant autocatalysis effect, promoted by the urethane group, has been found. The isoconversion method was also used to analyze the variation of the global activation energy with conversion. The global activation energy increases slightly as the curing reaction proceeds with a maximum value reached at approximately 30% conversion. In addition, the Eyring parameters were calculated from the obtained kinetic data.

Experimental and Kinetic Study on Ignition Delay Times of Dimethyl Ether at High Temperatures

An experimental investigation was performed on the effects of the temperature, pressure, equivalence ratio, and fuel concentration on ignition delay times of dimethyl ether (DME)/O2/Ar mixtures behind the reflected shock wave. Experimental conditions used temperatures over 1000–1600 K, pressures of 1.2–20 atm, and equivalence ratios of 0.5–2.0, with fuel concentrations of 0.5–2.457%. The measurements showed that the DME mixtures have different global activation energies under different equivalence ratios. Thus, correlations were derived under different equivalence ratios based on all experimental data, which fits fairly well with the experimental data. Four recently developed models were compared to the measurements, and their predictabilities were thoroughly discussed. Finally, a systematic kinetic chemical analysis was performed to chemically interpret the observed equivalence ratio dependence and to ascertain the key reactions that control ignition of DME, which are the potential candidates for improvement of LLNL DME Mech.

Rh assisted catalytic oxidation of jet fuel surrogates in a meso-scale combustor

Abstract Oxidation behavior of dodecane and two mixtures of dodecane and m-xylene (90/10 wt.% and 80/20 wt.%) over an Rh catalyst in a meso-scale heat recirculating combustor was examined to isolate the effect of aromatic content on performance. The fuel conversion, product selectivities, and reaction kinetics were calculated, and the global combustion behavior observed. The results showed that increasing the amount of m-xylene in the fuel increased the fuel conversion from 85% (pure dodecane) to 92% (90/10) and further to 98% (80/20). The presence of xylene also significantly increased CO 2 /H 2 O selectivity and decreased CO/H 2 selectivity. Global activation energy increased linearly with increase in xylene content, supporting that addition of aromatic species to fuel lowers the overall reactivity. The non-catalytic reaction was also simulated using Chemkin software to determine the effect of the Rh catalyst on the combustor performance and to analyze the difference in chemical mechanisms. The results revealed that the catalyst promotes total oxidation over partial oxidation, and lowers the global activation energy by up to 70%.

Diffusive-thermal instabilities in premixed flames: Stepwise ignition-temperature kinetics

This study is motivated by the observation that in combustion of hydrogen–oxygen/air and ethylene–oxygen mixtures the global activation energy appears to be high at low enough temperatures and low at high enough temperatures, reflecting the complex nature of the underlying chemistry. Stability analysis of a uniformly propagating planar premixed flame controlled by a stepwise ignition-temperature kinetics (representing the activation energy temperature-dependence) is carried out. It is shown that, for all its schematic nature, the diffusive-thermal model based on the ignition-temperature kinetics reproduces quite successfully the basic features of both cellular and pulsating instabilities typical of low and high Lewis number mixtures.

An Investigation on Sensitivity of Ignition Delay and Activation Energy in Diesel Combustion

The auto-ignition process plays a major role in the combustion, performance, fuel economy, and emission in diesel engines. The auto-ignition quality of different fuels has been rated by its cetane number (CN) determined in the cooperative fuel research engine, according to ASTM D613. More recently, the ignition quality tester (IQT), a constant volume vessel, has been used to determine the derived cetane number (DCN) to avoid the elaborate, time consuming, and costly engine tests, according to ASTM D6890. The ignition delay (ID) period in these two standard tests and many investigations has been considered to be the time period between start of injection (SOI) and start of combustion (SOC). The ID values determined in different investigations can vary due to differences in instrumentation and definitions. This paper examines the different definitions and the parameters that effect ID period. In addition, the activation energy dependence on the ID definition is investigated. Furthermore, results of an experimental investigation in a single-cylinder research diesel engine will be presented, while the charge density is kept constant during the ID period. The global activation energy is determined and its sensitivity to the charge temperature is examined.

A shock tube study of the autoignition characteristics of RP-3 jet fuel

Autoignition delay time measurements were performed for gas-phase RP-3/air mixtures behind reflected shock waves at temperatures of 650–1500K, pressures of 1–20atm, and equivalence ratios of 0.2, 1.0, and 2.0. Ignition delay times were determined using electronically excited CH∗ and/or OH∗ emissions and reflected shock pressure monitored through the shock tube sidewall. The dependence of the ignition delay times upon temperature, pressure and equivalence ratio has been investigated at high temperatures. Correlation expressions for the ignition delay under different equivalence ratios and pressures have been deduced separately. The global activation energy for RP-3/air varies significantly as the ignition pressure changes. A negative temperature coefficient (NTC) effect for RP-3 at 10atm was observed in the temperature range of 750–850K. Current results were compared with available Jet-A ignition data, showing good agreement with previous results of Jet-A. Based on the composition identification of RP-3, a mixture of 88.7% n-decane and 11.3% 1,2,4-trimethylbenzene by mole has been proposed as a surrogate for RP-3. Surrogate mechanism simulations were performed by using the mechanism proposed by Peters et al. (2009). The simulations show good agreement with the experimental data over wide ignition conditions. Sensitivity analyses were carried out to identify the important reactions in the ignition process and to explain the experimental phenomena. Current work provides a fundamental database for the development and validation of surrogate kinetic models for RP-3 jet fuel.

Opportunities for ceria-based mixed oxides versus commercial platinum-based catalysts in the soot combustion reaction. Mechanistic implications

The aim of this paper is to study the activities of ceria–zirconia and copper/ceria–zirconia catalysts, comparing with a commercial platinum/alumina catalyst, for soot combustion reaction under different gas atmospheres and loose contact mode (simulating diesel exhaust conditions), in order to analyse the kinetics and to deduce mechanistic implications.Activity tests were performed under isothermal and TPR conditions. The NO oxidation to NO2 was studied as well. It was checked that mass transfer limitations were not influencing the rate measurements. Global activation energies for the catalysed and non-catalysed soot combustion were calculated and properly discussed.The results reveal that ceria-based catalysts greatly enhance their activities under NOx/O2 between 425°C and 450°C, due to the “active oxygen”-assisted soot combustion. Remarkably, copper/ceria–zirconia shows a slightly higher soot combustion rate than the Pt-based catalyst (under NOx/O2, at 450°C).

Increased Flame Reactivity of a Lean Premixed Flame Through the Use of a Custom-Built High-Voltage Pulsed Plasma Source

High-voltage (HV) nonthermal pulsed plasma sources at atmospheric pressure are currently studied for combustion enhancement applications. The sub-microsecond electrical discharges produce reactive species that reduce the global activation energy of the combustion processes and increase the flame propagation speed while limiting gas heating. Current pulses of duration <;100 ns are produced through the discharge of a capacitor-charging HV dc power supply. Time-integrated intensified charge-coupled device images, filtered at 430 nm, of a lean premixed CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /air laminar flame under the influence of pulsed HV electrical discharges are presented as clear evidence of plasma-assisted combustion.

Kinetic study of 4-nitrophenol photocatalytic degradation over a Zn2+ doped TiO2 catalyst prepared through an environmentally friendly aqueous sol–gel process

• Kinetic study of 4-NP photocatalytic degradation under artificial light was performed. • A pseudo-first order kinetic model was adjusted on the experimental data. • Apparent reaction rate constant and global apparent activation energy were estimated. • A mechanism was proposed to describe the reaction at a molecular scale. • Statistical validations of the pseudo-first order model was successfully performed. A kinetic study of the photocatalytic degradation of 4-nitrophenol (4-NP) under UV–visible light (330 nm < λ < 800 nm) has been performed via a rigorous chemical engineering approach over a Zn 2+ doped TiO 2 catalyst prepared through an environmentally friendly aqueous sol–gel process. The experiments have been performed at three temperatures to enable the global activation energy to be estimated. The influence of the illumination intensity has also been considered. The possibility of internal and external diffusion limitations has been studied and the results obtained demonstrated that there is no diffusional limitation during the photocatalytic degradation of the 4-NP using the selected catalyst. Therefore, the apparent specific reaction rate measured corresponds to the actual reaction rate of the chemical reaction. Parameter adjustments show that the kinetic model that provides the best fit to the experimental data corresponds to a first order reaction. A sequence of elementary steps has been considered and a pseudo-steady state approach based upon the stationary state hypothesis for reaction intermediates has been applied to obtain a kinetic rate expression in agreement with the experimental data. The mean values of the reaction rate constant found at 283 K, 288 K and 293 K are respectively equal to k ‾ 1 = 0.094 ± 0.003 m 3 h −1 kg catalyst - 1 ; k ‾ 2 = 0.119 ± 0.004 m 3 h −1 kg catalyst - 1 and k ‾ 3 = 0.150 ± 0.023 m 3 h −1 kg catalyst - 1 and the global activation energy of the degradation reaction was evaluated as 40 kJ mol −1 . A phenomenological kinetic mechanism is proposed to describe the reaction at a molecular scale. Finally, statistical validations and residuals analysis have been performed to confirm that the first order model is suitable to represent the 4-NP photocatalytic degradation over time. Such studies are essential to design a reactor for water pollutant degradation on an industrial scale.