Observed Reaction Rate Research Articles

Sorption and desorption of BrF3 on NaF: Studies on thermodynamics and kinetics

Temperature dependence of bromine trifluoride vapor pressure over its adduct with sodium fluoride has been determined; the adduct normal dissociation temperature has been determined. Kinetics of sorption and desorption processes in BrF3(gas)–NaF(solid) system have been studied.The equation was proposed to illustrate the link between forward reaction rate (Ка) described by Arrhenius equation and experimental value (Ki):Ki= Kа⋅ (Pa/Peq)m,where Ki – observed reaction rate constant, Ka – forward reaction rate constant described by Arrhenius equation; Pa – partial pressure of BrF3; Peq – equilibrium pressure of BrF3 above BrF3⋅3NaF; m – factor characterizing the interaction area of BrF3 with NaF. The application of this equation makes possible to determine the true reaction rate values and reaction activation energy in chemisorption terms; it also helps to calculate the degree BrF3 sorption on NaF reaction at different temperatures and adsorbate pressures.The possibility of sorption-desorption separation of bromine trifluoride – uranium hexafluoride – iodine pentafluoride system with use of sodium fluoride was shown.

Rapid Self-Assembly of Metal/Polymer Nanocomposite Particles as Nanoreactors and Their Kinetic Characterization.

Self-assembled metal nanoparticle-polymer nanocomposite particles as nanoreactors are a promising approach for performing liquid phase reactions using water as a bulk solvent. In this work, we demonstrate rapid, scalable self-assembly of metal nanoparticle catalyst-polymer nanocomposite particles via Flash NanoPrecipitation. The catalyst loading and size of the nanocomposite particles can be tuned independently. Using nanocomposite particles as nanoreactors and the reduction of 4-nitrophenol as a model reaction, we study the fundamental interplay of reaction and diffusion. The induction time is affected by the sequence of reagent addition, time between additions, and reagent concentration. Combined, our experiments indicate the induction time is most influenced by diffusion of sodium borohydride. Following the induction time, scaling analysis and effective diffusivity measured using NMR indicate that the observed reaction rate are reaction- rather than diffusion-limited. Furthermore, the intrinsic kinetics are comparable to ligand-free gold nanoparticles. This result indicates that the polymer microenvironment does not de-activate or block the catalyst active sites.

Quantum Effects in Cold Molecular Collisions from Spatial Polarization of Electronic Wave Function.

The quantum phenomena of electronic and nuclear resonances are associated with structures in measured cross sections. Such structures were recently reported in a cold chemistry experiment of ground-state hydrogen isotopologues (H2/HD) colliding with helium atoms in the excited triplet P-state (He(23P)) [Shagam et al. Nature Chem. 2015, 7, 921], but a theoretical explanation of their appearance was not given. This work presents a quantum explanation and simulation of this experiment, which are strictly based on ab initio calculations. We incorporate complex potential energy surfaces into adiabatic variational theory, thereby reducing the multidimensional scattering process to a series of uncoupled 1D scattering "gedanken experiments". Our theoretical result, which is in remarkable agreement with the experimental data, manifests that the structures in the observed reaction rate coefficient are due to the spatial arrangement of the excited He p-orbitals with respect to the interaction axis, consequently changing the system from a normal two-rotor model to a three-rotor one. This theoretical scheme can be applied to explain and predict cross sections or reaction rate coefficients for any resonance-related phenomenon.

Kinetics and mechanism of reaction between carbon disulfide and novel aqueous amines solutions

The mechanism and kinetics of carbon disulfide (CS2) capture by aqueous solutions of well known alkanolamines ([monoethanolamine (MEA) and diethanolamine (DEA)] and novel cyclic mono- and polyamines [morpholine (MRPH), piperazine (PZ), n-methyl piperazine (NMPZ) and n-hydroxyethyl piperazine (NHEPZ)] were investigated by stopped-flow apparatus with conductivity detection. The observed reaction rate constants were obtained for a temperature range of 298.15-313.15 K and it was found that cyclic amines react much faster than others. A modified termolecular reaction mechanism was used to analyse the experimental kinetic data. The activation energies for all systems were also obtained by evaluating the Arrhenius equation.

Kinetics and Mechanism of Reaction between Carbon Disulfide and Novel Aqueous Amines Solutions

The mechanism and kinetics of carbon disulfide (CS2) capture by aqueous solutions of well known alkanolamines ([monoethanolamine (MEA) and diethanolamine (DEA)] and novel cyclic mono- and polyamines [morpholine (MRPH), piperazine (PZ), n-methyl piperazine (NMPZ) and n-hydroxyethyl piperazine (NHEPZ)] were investigated by stopped-flow apparatus with conductivity detection. The observed reaction rate constants were obtained for a temperature range of 298.15-313.15 K and it was found that cyclic amines react much faster than others. A modified termolecular reaction mechanism was used to analyse the experimental kinetic data. The activation energies for all systems were also obtained by evaluating the Arrhenius equation.

Mathematical modeling of oscillating CO oxidation on Pt-group metals at near atmospheric pressure: Activity of metallic and oxidized surfaces

This article is a theoretical and numerical analysis of experimental results concerning the oscillatory and steady-state behavior during CO oxidation on Pd(100) and Pt(110) catalysts in continuous flow and batch reactors at near atmospheric pressure conditions. In the literature there is disagreement about which mechanism describes the reaction of CO oxidation. Some authors suggested that the oxidized phase is more active than the metallic phase with chemisorbed oxygen and that the Mars-van Krevelen mechanism and not the traditional Langmuir-Hinshelwood mechanism is required to describe the catalytic reaction. To study this disagreement in data interpretation, we apply a slight modification of a well-known kinetic model suggested by Sales, Turner, and Maple, which is based on the Langmuir-Hinshelwood mechanism. We show that in a high-activity state the calculated concentration of the oxide can exceed 0.9 ML. However, this does not mean that the oxide phase is more active than the metallic phase, because oxide-free sites of the partially oxidized catalyst may be responsible for the observed reaction rate. Available experimental results, including oscillatory behavior, can be explained on the basis of the Langmuir-Hinshelwood mechanism. We conclude that there is no need to introduce the Mars-van Krevelen mechanism to model CO oxidation on Pt-group metals.

Perovskite-like photocatalyst, PbBiO2Br/PbO/g-C3N4: Synthesis, characterization, and visible-light-driven photocatalytic activity

Abstract Lead bismuth oxybromide (PbBiO2Br) is a powerful perovskite-like semiconductor that can be used with visible light. PbBiO2Br is a perovskite-like photocatalyst that has recently received scholarly attention. Until now, scholars have not published studies regarding PbBiO2Br/PbO/g-C3N4-mediated crystal violet (CV) dye and 2-Hydroxybenzoic Acid (HBA) photodegradation under irradiation with visible light. The current paper reports the first composite isolation of PbBiO2Br/PbO/g-C3N4; characterization was realized through XRD, TEM, FE-SEM-EDS, HR-XPS, FI-IR, PL, BET, and UV-DRS. Photocatalytic efficiency observation proved that using PbBiO2Br/PbO/g-C3N4 produced the highest observed reaction rate, namely 0.1981 h−1. This derivation exceeded the derivations for the PbBiO2Br, PbO, g-C3N4 photocatalysts, and PbBiO2Br/PbO by 1.23, 34.2, 4.3, and 1.2 times, respectively. Four scavengers demonstrated quenching effects. The O2•− radical was critical to HBA degradation, whereas the •OH radical and 1O2 species played minor roles in the observed CV dye degradation. The present paper proposes and explains possible photocatalytic degradation mechanisms. This study's methods of PbBiO2Br/PbO/g-C3N4 synthesis and photocatalytic degradation of CV can be useful for future treatment of wastewater.

Computational insight into the mechanism of O2 to H2O2 reduction on amino-groups-containing g-C3N4

First-principles DFT calculations were conducted to investigate the mechanism of O2 to H2O2 reduction on both amino-group-containing (g-C3N4-NH2) and defect-free g-C3N4. The theoretical results obtained were directly compared with the experimental findings reported by Li et al. [Appl. Catal., B 190, 26–35, (2016)]. It was found that the defective system with one amino and one imine group is more stable than that with two amino groups. By studying different adsorption structures using O2 and H2O2 molecules, we determined the most stable adsorption configurations. Finally, we calculated the energy barrier for O2 reduction for both the systems. We found that the oxygen reduction process proceeds via two different mechanisms on g-C3N4-NH2 and g-C3N4, which was in agreement with the experimental results. Our results indicate that the energy barrier for oxygen reduction for the defective system is higher than that for a defect-free system; hence, we determined and discussed other factors that may impact the observed reaction rates. The influence of carbon vacancy defects combined with hydrogen saturation on electronic properties was also investigated.

Kinetics of Catalytic Wet Peroxide Oxidation of Phenolics in Olive Oil Mill Wastewaters over Copper Catalysts

During olive oil extraction, large amounts of phenolics are generated in the corresponding wastewaters (up to 10 g dm–3). This makes olive oil mill wastewater toxic and conventional biological treatment challenging. The catalytic wet peroxide oxidation process can reduce toxicity without significant energy consumption. Hydrogen peroxide oxidation of phenolics present in industrial wastewaters was studied in this work over copper catalysts focusing on understanding the impact of mass transfer and establishing the reaction kinetics. A range of physicochemical methods were used for catalyst characterization. The optimal reaction conditions were identified as 353 K and atmospheric pressure, giving complete conversion of total phenols and over 50% conversion of total organic carbon content. Influence of mass transfer on the observed reaction rate and kinetics was investigated, and parameters of the advanced kinetic model and activation energies for hydrogen peroxide decomposition and polyphenol oxidation were estimated.

Investigation of fixed-bed photocatalytic membrane reactors based on submerged ceramic membranes

Though having been studied for more than four decades, photocatalysis is still hardly applied in large-scale water and wastewater treatment. This is mainly due to the low energy efficiency of conventional photocatalytic reactors. A recently introduced reactor concept, the fixed-bed photocatalytic membrane reactor (FPMR), can potentially overcome this shortcoming. Its performance for the degradation of organic compounds is examined for different modes of operation. For this purpose, FPMRs based on commercial submerged ceramic membranes were used, which are covered by a photocatalytic layer of pyrogenic titania. The FPMRs were performed in two operational modes: closed-loop reactor and continuous-flow reactor. Oxalic acid was used as a model organic compound to conduct photocatalysis. The influence of light intensity and catalyst layer thickness as well as mass transfer inside the layer were thoroughly studied. The evaluation of the reactors was based on the apparent quantum yield, the photocatalytic space–time yield and specific energy consumption. The results demonstrate that the FPMRs are considerably more efficient than other reported reactor concepts. Its apparent quantum yield can reach up to 11.1%. Furthermore, its specific light energy consumption is merely around 0.1 kWh/g (TOC). The results also reveal that closed-loop FPMRs achieve higher efficiencies than continuous-flow FPMRs. Last but not least, a quantitative model for calculating the reaction rate constant of a photocatalytic membrane from observed reaction rate constant of a photocatalytic membrane reactor was developed and experimentally verified.

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane.

During the pulsed-electron beam direct grafting of neat styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) substrate, the radiolytically-produced styryl and carbon-centered FEP radicals undergo various desired and undesired competing reactions. In this study, a high-dose rate is used to impede the undesired free radical homopolymerization of styrene and ensure uniform covalent grafting through 125-μm FEP films. This outweighs the enhancement of the undesired crosslinking reactions of carbon-centered FEP radicals and the dimerization of the styryl radicals. The degree of uniform grafting through 125-μm FEP films increases from ≈8%, immediately after pulsed electron irradiation to 33% with the subsequent thermal treatment exceeding the glass transition temperature of FEP of 39°C. On the contrary, steady-state radiolysis using 60Co gamma radiolysis, shows that the undesired homopolymerization of the styrene has become the predominant reaction with a negligible degree of grafting. Time-resolved fast kinetic measurements on pulsed neat styrene show that the styryl radicals undergo fast decays via propagation homopolymerization and termination reactions at an observed reaction rate constant of 5 × 108 l · mol-1 · s-1. The proton conductivity of 25-μm film at 80°C is 0.29 ± 0.01 s cm-1 and 0.007 s cm-1 at relative humidity of 92% and 28%, respectively. The aims of this work are: 1. electrolyte membranes are prepared via grafting initiated by a pulsed electron beam; 2. postirradiation heat-treated membranes are uniformly grafted, ideal for industry; 3. High dose rate is the primary parameter to promote the desired reactions; 4. measurement of kinetics of undesired radiation-induced styrene homopolymerization; and 5. The conductivity of prepared membranes is on par or higher than industry standards.

Kinetics of Ethylene Epoxidation on a Promoted Ag/α-Al2 O3 Catalyst-The Effects of Product and Chloride Co-Feeds on Rates and Selectivity.

The overall chloriding effectiveness factor (Z*), defined as the ratio of ethyl chloride concentration in parts per million to the sum of ethylene and ethane concentration in mole percent multiplied by a weighting factor to account for their efficacy in removing chlorine-adatoms from the surface, was used as a parameter to account for the effects of chlorine on the kinetics of ethylene epoxidation on a highly promoted 35 wt % Ag/α-Al2 O3 catalyst. An increase in O2 order (≈0.7 to 1) and a decrease in C2 H4 order (≈0.5 to <0) with increasing Z* (Z*=2.1, 3.4, 5.2, and 8.9) was observed implicating kinetic relevance of O2 activation on chloride-promoted silver catalysts. Carbon dioxide co-feed (1-5 mol %) was found to promote ethylene oxide selectivity as CO2 co-feed reversibly inhibits CO2 synthesis rates (-0.6 order) more than ethylene oxide synthesis rates (-0.49 order) at all Z* values. Ethylene oxide and CO2 rates were found to be invariant with ethylene oxide (0-0.5 mol %) and acetaldehyde (0-1.7 ppm) co-feeds, suggesting that there is minimal product inhibition under reaction conditions. A model involving a common reaction intermediate for ethylene oxide and carbon dioxide synthesis and two types of atomically adsorbed oxygen species-nucleophilic and electrophilic oxygen-is proposed to plausibly describe the observed reaction rate dependencies and selectivity trends as a function of the chloriding effectiveness.

Electrochemical Methods for Assessing Kinetic Factors in the Reduction of CO2 to Formate: Implications for Improving Electrocatalyst Design

Thermochemical insights are often employed in the rationalization of reactivity and in the design of electrocatalysts for CO2 reduction reactions targeting C–H bond-containing products. This work identifies experimental methods for assessing kinetic aspects of reactivity. These methods are illustrated using [Fe4N(CO)12]−, which produces formate from CO2 at −1.2 V versus SCE in either a MeCN/H2O solvent (95:5) or pH 6.5 buffered water. Elementary rates for each reaction step are identified along with the rate-determining step (RDS) as C–H bond formation. Transition state kinetics were determined from an Eyring analysis for the rate-determining C–H bond formation step using temperature-dependent electrochemical measurements. A lower measured ΔG⧧ (298 K, 12.3 ± 0.1 kcal mol–1) in a pH 6.5 aqueous solution, compared with a ΔG⧧(298 K) of 15.0 ± 0.1 kcal mol–1 in a MeCN/H2O solvent (95:5), correlates with faster observed reaction rates and provides a kinetic rationalization for the solvent-dependent chemistry. ...

Understanding Electrocatalytic Hydrogenation of Phenol and Benzaldehyde on Platinum Group Metals for Fuel Production

Despite the ability of aqueous-phase electrocatalytic reduction (hydrogenation) to produce fuels,1 pharmaceuticals, food and other commodity chemicals, the mechanisms of the metal-catalyzed reactions are not always well-understood. Understanding these reactions would allow us to develop improved electrocatalysts and processes to enable sustainable production of important fuels and chemicals. One major challenge in understanding the surface electrochemistry is that the characterization of the electrocatalyst surface is difficult in the presence of water. There are several techniques that can be used to understand the reactant coverages (under reacting conditions), and in this talk a brief overview will be given of spectroscopic techniques (including infrared, Raman, X-ray absorption) and cyclic voltammetry as ways to probe the electrocatalyst surface. In this talk, phenol and benzaldehyde hydrogenation (to cyclohexanol and benzyl alcohol, respectively) on Pt/C and Pd/C will be analyzed using i) experimental and theoretical X-ray absorption spectroscopy and ii) cyclic voltammetry to understand reactant coverages and explain observed reaction rates. Understanding these two models reactants will lead to improved electrocatalysis for not only phenol and benzaldehyde, but also similar compounds that exist in in waste bio-oil, which can be converted to transportation fuel-grade hydrocarbons. The effect of applied potential, reactant and product concentration, and pH on both electrocatalyst surface (including adsorbates) and reaction rate will be discussed. A brief discussion of these results with respect to gas-phase hydrogenation will also be included. References (1) Song, Y.; Gutiérrez, O. Y.; Herranz, J.; Lercher, J. A. Appl. Catal. B Environ. 2016, 182, 236.

Absorption rates of carbon dioxide in amines in hydrophilic and hydrophobic solvents

The rate of absorption of CO2 into amines in hydrophilic and hydrophobic solvent mixtures was studied in this work using a stopped-flow apparatus and a stirred-tank reactor. Monoethanolamine (MEA, primary amine) and N-methyl benzylamine (NMBZA, aromatic secondary amine) are chosen for this study and diluted in hydrophobic or hydrophilic solvents at different temperatures (295–343 K) and concentrations (0.01–4 kmol.m−3). It was found that the reaction rate between the secondary amine and CO2 in water is faster than the reaction with the linear primary amine (MEA); however, in an ethereal hydrophobic non-aqueous system the NMBZA-CO2 reaction is slower than the reaction of CO2 with MEA. With respect to amine, the reaction orders were found to be 0.9 and 1.2 for hydrophilic systems (MEA + H2O, NMBZA + H2O). For hydrophobic system they were found to be 0.6 and 2.7 (NMBZA + ethereal hydrophobic solvent, NMBZA + MePhOH + ethereal hydrophobic solvent). When amine was mixed with hydrophilic solvent (H2O), the activation energy of amine (NMBZA) to react with CO2 was found to be 27.66 kJ.mol−1 and decreased to 10.37 kJ.mol−1 when mixed with hydrophobic solvent (ethereal hydrophobic solvent). The activation energy of hydrophobic solvent was found to increase by adding an alcohol to the solvent (MePhOH + ethereal hydrophobic solvent). Both the zwitterion and termolecular mechanism were applied to the experimental data. It was found that deprotonation of the zwitterion and deprotonation of the loosely bound complex was the rate limiting step for the zwitterion and termolecular mechanism, respectively.Additionally, activators such as water, piperazine (PZ), and 4-hydroxy piperidinol (HPIP) were added to the ethereal hydrophobic non-aqueous solvent to determine the effect on the reaction rate. It was found that the water- and amine-based activators lead to an increase in the observed reaction rates as the concentration of the activators increased. The reaction of NMBA with CO2 and PZ exhibited a higher reaction rate but the PZ was insoluble in the non-aqueous NMBZA system, whereas HPIP remained soluble and offered a similar reaction rate. The activation energy of ethereal hydrophobic non-aqueous solvent to react with CO2 increased from 27.98 to 32.83 kJ.mol−1 by adding PZ and 33.51 kJ.mol−1 by HPIP and remained by adding H2O (26.78 kJ.mol−1). From this work, it was found that the non-aqueous solvent plays an important role in the reaction rate of CO2 with amines. Activators and solvents can be selected to increase the reaction rate with CO2.

Geochemical Effects of Millimolar Hydrogen Concentrations in Groundwater: An Experimental Study in the Context of Subsurface Hydrogen Storage.

Hydrogen storage in geological formations is one of the most promising technologies for balancing major fluctuations between energy supply from renewable energy plants and energy demand of customers. If hydrogen gas is stored in a porous medium or if it leaks into a shallow aquifer, redox reactions can oxidize hydrogen and reduce electron acceptors such as nitrate, FeIII and MnIV (hydro)oxides, sulfate, and carbonate. These reactions are of key significance, because they can cause unintentional losses in hydrogen stored in porous media and they also can cause unwanted changes in the composition of protected potable groundwater. To represent an aquifer environment enclosing a hydrogen plume, laboratory experiments using sediment-filled columns were constructed and percolated by groundwater in equilibrium with high (2-15 bar) hydrogen partial pressures. Here, we show that hydrogen is consumed rapidly in these experiments via sulfate reduction (18 ± 5 μM h-1) and acetate production (0.030 ± 0.006 h-1), while no methanogenesis took place. The observed reaction rates were independent from the partial pressure of hydrogen and hydrogen consumption only stopped in supplemental microcosm experiments where salinity was increased above 35 g L-1. The outcomes presented here are implemented for planning the sustainable use of the subsurface space within the ANGUS+ project.

The effect of exhaust gas composition on the kinetics of soot oxidation and diesel particulate filter regeneration

Experimental investigation of the effect of water vapor on non-catalyzed carbon oxidation with NO2 has shown a promoting effect of about a factor 2. The promoting effect of water increases with decreasing temperature. Similarly, water was observed to promote carbon oxidation with molecular oxygen. Furthermore, a synergistic effect was observed when NO2, water and oxygen were all present in the gas phase. Evidences have been found suggesting that the promoting effect of water proceeds via an interaction with surface oxygen complexes. Implementing the results of this study in the control unit of diesel vehicles will increase the efficiency of filter regeneration. Therefore, the fuel penalty associated with active regeneration cycles can be minimized. To this end, a global kinetic model was developed that can successfully fit the observed reaction rates over the entire range of carbon conversion. The model can be used to optimize filter regeneration by predicting the required exhaust condition for maintaining a balance between soot accumulation and burn-off. A population balance model was formulated that makes it possible to keep track of age distribution in a reactor channel or in a soot filter.

Modeling the Transient Kinetics of the L1 Metallo-β-Lactamase.

The transient absorption spectroscopy of hydrolysis of the chromogenic substrate nitrocefin by the L1 metallo-β-lactamase (MβL), a bacterial enzyme responsible for destruction of β-lactam antibiotics molecules, showed formation and decay of a plausible red-shifted reaction intermediate. We propose a mechanism of this important reaction consistent with the transient kinetic data. Quantum mechanics/molecular mechanics (QM/MM) simulations of the reaction pathway revealed occurrence of two reaction intermediates (I1, I2) between the enzyme-substrate (ES) and enzyme-product (EP) complexes. The vertical S0-S1 transition energies calculated at the minimum energy structures (ES, I1, I2, EP) using the time dependent DFT (TD-DFT) method allowed us to assign the experimental absorption bands to all reacting species. We numerically solved the equations of chemical kinetics with the rate constants of all elementary steps evaluated with the transition state theory and simulated the kinetic curves as well as the evolution of the absorption bands of ES, I2, and EP. Direct comparison to the experimental data allowed us to identify the I2 intermediate as the transient red-shifted species detected experimentally. In agreement with the experimental observations, the recomputed energy profiles for the D120N and D120C mutants of L1 reacting with nitrocefin showed absence of a stable intermediate I2. According to the consistent experimental and theoretical results, the breakdown of the intermediate I2 corresponds to the rate-limiting stage of the chemical transformations in the active site of the L1 metallo-β-lactamase. On this basis, we established a QSAR-type correlation between the observed reaction rates (kcat) of three cephalosporin antibiotics (cefotixin, nitrocefin, cefepime) showing different hydrolysis rates by the L1 metallo-β-lactamase and different structures of the corresponding intermediates of the I2 type. This correlation can be employed for a rational design of novel antibiotics, which are not decomposed by metallo-β-lactamases.

Selective alkylation of T-T mismatched DNA using vinyldiaminotriazine-acridine conjugate.

The alkylation of the specific higher-order nucleic acid structures is of great significance in order to control its function and gene expression. In this report, we have described the T–T mismatch selective alkylation with a vinyldiaminotriazine (VDAT)–acridine conjugate. The alkylation selectively proceeded at the N3 position of thymidine on the T–T mismatch. Interestingly, the alkylated thymidine induced base flipping of the complementary base in the duplex. In a model experiment for the alkylation of the CTG repeats DNA which causes myotonic dystrophy type 1 (DM1), the observed reaction rate for one alkylation increased in proportion to the number of T–T mismatches. In addition, we showed that primer extension reactions with DNA polymerase and transcription with RNA polymerase were stopped by the alkylation. The alkylation of the repeat DNA will efficiently work for the inhibition of replication and transcription reactions. These functions of the VDAT–acridine conjugate would be useful as a new biochemical tool for the study of CTG repeats and may provide a new strategy for the molecular therapy of DM1.

On the influence of different experimental systems on measured heterogeneous gasification kinetics

The objective of this study was to gain further insight into the characteristic behavior of reaction systems for establishment of intrinsic and effective particle gasification kinetics. A wood-derived char was subjected to the carbon dioxide-containing atmospheres of four different reaction systems: a thermogravimetric analyzer (TGA), a fluidized-bed reactor (FBR), a fixed-bed reactor (FFB) and a drop-tube reactor (DTR). All systems contained the same CO2 partial pressure of 800 mbar at atmospheric pressure. A temperature span from 700 to 1600 °C and residence times from 200 ms to over 8 h were investigated. Reactivities spanning five orders of magnitude were observed. The gasification experiments resulted in the identification of four fundamentally different reaction domains; two were classified as true particle behavior, while the observed reaction rates of the other two domains are mainly dominated by the characteristics of the reaction system applied. The domains were referred to as: chemical control, particle diffusion control, bed diffusion control, and system response control. Within the present work, the occurrence of these reaction domains is discussed in regard to the physical nature of the experiments, and implications towards the measurement of reliable particle kinetics are formulated.