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The partial oxidation of acrolein and methacrolein on Mo/V/W-mixed oxides was studied by transient kinetic investigation with a new experimental technique. Within the so‑called HETKA (Homologue Exchange Transient Kinetic Analysis) experiments, acrolein (ACR) was stepwise replaced by methacrolein (MAC), and vice versa under constant reaction conditions. Conversion and yield decrease significantly when ACR is substituted by MAC. Evidence is given that the lower reaction rate with MAC is caused by the formation of coke deposits on the catalyst surface. Furthermore, a temperature programmed reaction (TP reaction) was carried out in which both aldehydes were fed at the same time. Compared with the TP reactions with only one aldehyde, the conversion and yield curves are shifted to higher temperatures. Regarding acrylic acid, the maximum yield and selectivity are not influenced by the contemporaneous presence of both aldehydes. On the contrary, the selectivity to methacrylic acid is increased significantly.

Manipulation of carbon surface functionalization and especially of oxygen surface groups has been demonstrated to be key for obtaining high performance materials in a multitude of applications. Although control of carbon surface chemistry offers large potential in many technical relevant applications, qualitative and quantitative analysis of surface oxides for amorphous and porous carbons remains challenging. In this study, we attempt selective, organic chemistry-based functionalization of a polymer-derived porous model carbon featuring high oxygen loadings, with the aim to establish analytical standards for temperature programmed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). In this context, quantitative chemical reduction of an oxidized carbon material with lithium aluminum hydride (LiAlH4) is utilized as the key for the synthesis of carbon materials with defined ensembles of oxygen surface groups (hydroxyl groups and ethers). Based on this reduction strategy, selective LiAlH4 reduction based on protection group chemistry leads to aldehydes, ketones and quinones as surface functional groups and chemical grafting is studied for the selective introduction of phenyl esters, methyl ethers and carboxylic acids. All materials are evaluated with respect to the applicability as analytical standard by DRIFT spectroscopy, TPD, X-ray photoelectron spectroscopy and titration methods.

Catalytic conversion of n-butanol to high-value-added product is considered as a highly important route towards biomass derived fine chemicals. The present work reports the applications of non-metallic multi-walled carbon nanotube (CNT) as bifunctional catalysts for oxygen assisted n-butanol conversion reactions. Oxidative dehydrogenation (ODH) and dehydration of n-butanol on CNT yielded aldehyde and alkene compounds via redox and acid catalytic routes, respectively. CNT exhibited high activity (over 50% n-butanol conversion) and stability (over 120 h) under gentle reaction conditions (

A liquid core waveguide membrane microreactor is a novel concept that allows in situ spectroscopy to be carried out in an optical microreactor, while enabling a very high gas-to-liquid mass transfer. The potential of this reactor concept to derive kinetics in gas/liquid reactions is demonstrated using the heteropoly acids catalyzed oxidation of biomass to formic acid (the ‘OxFA process’). For vanadium-substituted, Keggin-type heteropoly acids, the kinetics of the reduction and reoxidation step of the catalyst cycle was deduced using in situ UV/Vis spectroscopy. Reduction was studied from 40 to 80 °C: a strong dependency of the reduction kinetics was deduced. In combination with additional cyclic voltammetry and EPR characterization, it can be assumed that two active centers promote this reaction, while the existence and proportions of both types depends on the degree of vanadium substitution. The rapid mass transfer allowed transient response experiments to be carried out for the reoxidation step, which was studied up to 150 °C. Switching from anaerobic to aerobic conditions, an even stronger dependency of the reoxidation kinetics on the degree of vanadium substitution was revealed.

Eine neue Synthesestrategie liefert “Nicht-nano”-Kohlenstoffmaterialien als Dehydrierungskatalysatoren, die eine ähnliche katalytische Leistung wie Nanokohlenstoffe aufweisen. Schlüsselelement sind hierbei Kohlenstoffpräkursoren auf Polymerbasis, die eine Soft-Templat-Strategie mit Ionenadsorption und katalytischer Graphitisierung kombinieren, um eine Kontrolle der makroskopischen Form, Textur und Kristallinität zu ermöglichen und nach der Pyrolyse einen hybriden amorph/graphitischen Kohlenstoff zu erhalten. Aus diesem Zwischenprodukt wird der aktive Kohlenstoffkatalysator hergestellt, indem die amorphen Anteile des Hybridkohlenstoffs durch selektive Oxidation entfernt werden. Die oxidative Dehydrierung von Ethanol wurde als Testreaktion gewählt. Die neuen Kohlenstoffkatalysatoren zeigen eine vergleichbar hohe Selektivität (82 %) wie ein Benchmark mit Kohlenstoffnanoröhren, jedoch mit 10-mal höheren Raum-Zeit-Ausbeuten bei 330 °C. Diese neuartigen Kohlenstoffmaterialien sind über einen technisch skalierbaren, reproduzierbaren Syntheseweg zugänglich und weisen kugelförmige Partikel mit Durchmessern um 100 μm auf, was eine unproblematische Handhabung ermöglicht.

Oxidation of acrolein to acrylic acid on a Mo/V/W mixed oxide catalyst was studied by transient (cyclic temperature-programmed (TP)) as well as steady-state methods. TP reactions (TPReactions) exhibit an activity hysteresis of the catalyst with respect to temperature. As a result of the steady-state measurements, the activity hysteresis is not related to multiple steady states and is exclusively a transient phenomenon. Generally, the dynamics of bulk oxygen plays a key role leading to a reversible oxidation/reduction of the catalyst surface which influences the activity. This means the bulk acts as oxygen buffer. In this context, a reaction model, which involves the participation of bulk oxygen, was deduced and verified by modeling.

Interest in energy storage technologies is still increasing in times of the excess of electricity that is generated by wind farms or solar plants. Solar electricity can be transformed to solar-hydrogen via water electrolysis. A crucial part of the energy storage technologies plays the efficient conversion of H2 and CO2 from renewable resources. Here, the process conditions for continuously catalytic hydrogenation of CO2 to CH3OH under supercritical conditions over lab-synthesized Cu/ZnO/Al2O3 catalysts were investigated. The impact of temperature (230 – 330 °C), residence time (0.5 - 2.2 s) at moderate pressure (150 bar) but even above the supercritical parameters of CO2 showed a selective CO2 hydrogenation. Higher H2 concentrations, respectively higher H2:CO2-ratios (H2:CO2 = 6), lead to an increased selectivity of CH3OH. A possible in situ phase separation of reaction products within the reactor due to the higher densities of the reaction mixture by the highered pressure could affect the kinectics and simplfy the down-stream processing. The combination of thermodynamic studies (phase separation phenomena) as well as the catalytic performance tests for the CO2 hydrogenation under supercritical conditions are discussed. Based on these data a process concept is presented.

Zur besseren Nutzung von Exzessenergien wurde ein Warmespeichersystem entwickelt, das sich aus einem Blockheizkraftwerk (BHKW) mit einem integrierten Langzeitwarmespeicher zusammensetzt. Aus okonomischen Grunden wird ein BHKW ganzjahrig bei optimalem Wirkungsgrad betrieben. Die Folge ist, dass Warmeenergie im Sommer sinnvollerweise gespeichert werden sollte, um sie in der Heizperiode zu nutzen. Hierbei wird als Warmespeichersystem ein binares System bestehend aus einem modifizierten Zeolith 5A und Ammoniak eingesetzt. Die abschliesende Auslegung zeigt, dass es als Kurz- und Langzeitwarmespeicher eingesetzt werden kann.

During the acrylic acid (AA) storage a quality loss occurs due to the formation of by-products such as diacrylic acid (DiAA), triacrylic acid (TriAA) and higher oligomers. This problem intensifies in the presence of water since the formation rate of oligomers increases and further byproducts such as 3hydroxypropionic acid (3-HPA) and 3hydroxydiacryl acid (3-HDiAA) are formed. However, water is often essential during storage and transport to rise the flashpoint or to reduce the melting point. In the literature only the formation of DiAA has been investigated. In this work the formation kinetics are investigated for all mentioned components at 100 °C in pure and aqueous AA containing 5, 10 and 20 wt% water. The formation mechanisms of 3-HPA and 3-HDiAA are assumed as acid catalyzed ester hydrolyses of DiAA or TriAA. The hydration of AA to 3-HPA is excluded because the formation process does not exhibit a second order kinetic reaction. The introduced reactions are modelled with the measured kinetic data in order to confirm the proposed reactions.

Carbon surface oxides have been demonstrated to be crucial for high performing carbon materials in various applications. Diffuse reflectance infrared Fourier transform spectroscopy represents a powerful time-resolved method to study the surfaces of functional materials under process conditions. Due to the severe overlap of the contributions of individual surface groups in combination with compared to organic molecules shifted absorption maxima meaningful analysis remains challenging. Especially due to the unknown maxima, deconvolution of the superimposed bands is strongly hindered. In this study, we developed a procedure based on hydrolysis, thermal annealing or a combination thereof, which allows to disentangle carbonyl absorption maxima of carboxylic acids, anhydrides and lactones on carbon surfaces. In order to verify the proposed transformations, thorough characterization by temperature programmed desorption, X-ray photoelectron spectroscopy, potentiometric titration and Boehm titration was carried out. Applying this procedure for a polymer derived reference material, the carbonyl absorption maximum could be deduced, which are positioned for lactones at 1771 cm−1, for carboxylic acids between 1753 cm−1 and 1760 cm−1, and for carboxylic anhydrides at 1792 cm-1 and 1852 cm-1. This allowed deconvolution of the carbonyl band, paving the way for in situ time-resolved analyses.

To diversify energy sources and to address the impacts of global warming, the transformation of biomass, a renewable energy source, into fuels and chemicals is becoming increasingly necessary. The gasification technology is an efficient way of converting biomass via syngas into sustainable fuels. By-products, especially tar, are formed during the gasification process and need to be removed before further downstream processing. Mo/V/W-mixed oxides were found to be applicable for the catalytic tar oxidation in CO/H2 atmosphere by adding a stoichiometric amount of oxygen. In temperature-programmed experiments the reactivity of different tar model compounds during the selective oxidation on Mo/V/W-mixed oxides as well as the catalytic performances of V2O5, WO3, and MoO3 during the tar oxidation were investigated.

The partial oxidation of unsaturated aldehydes such as acrolein and methacrolein to the corresponding carboxylic acids is of big importance for the chemical industry. The heart of these production plants is the oxidation catalyst. Acrylic acid is produced via the selective oxidation of acrolein on Mo/V/W mixed oxides with an excellent catalytic performance (S > 90 %, X > 95 %, life time >3 a). Under the same conditions the conversion of methacrolein to methacrylic acid has a poor catalytic performance (S

This paper examines the activity of a platinum catalyst for the oxidation of CO under conditions of temperature cycling. Each cycle consists of an ignition and extinction curve obtained with a linear temperature ramp. It is shown that the catalyst activity is higher for the first ignition cycle than for the subsequent ones regarding CO conversion. The activity for the extinction portion of each cycle is the same for all cycles. It is proposed that the loss of catalyst activity results from the deposition of hydrocarbon residues during the extinction part of the cycle. The catalyst activity can be completely restored by heating the catalyst to 350 °C in the presence of oxygen and nitrogen.

A new experimental setup is introduced, enabling a preheated exhaust gas mixture to abruptly heat up an initially cold monolith catalyst and, thus, reproduce transient catalyst light-off behavior. With this setup, cold start experiments have been carried out on an aged monolithic Pd three-way catalyst (TWC). This study aims at systematically investigating the effect of diverse hydrocarbons, including methane, acetylene, ethene, ethanol, acetaldehyde, propane, propene, toluene, and xylene in TWC exhaust. It was shown that the commonly used model components propane and propene do not represent the behavior of aromatics and other hydrocarbons present in a typical TWC exhaust very well, since they do not account for their variability in inhibition strength and reactivity. Among the studied hydrocarbons, acetylene proved to be the strongest inhibitor; even at low concentrations of 70 ppm (a typical value found in TWC exhaust), acetylene inhibition increases CO cold-start emissions by 40 %. Furthermore, aromatic and liquid hydrocarbon species (like ethanol) first condense on the initially cold catalyst surface and evaporate again as the catalyst heats up, resulting in a desorption peak at the catalyst outlet.

In today’s vehicle applications, SCR ammonia dosing is completed using complex control algorithms that need to be parameterized for the individual catalyst technology. Owing to the complexity of the parameterization procedures, ammonia dosing is frequently completed using either oversimplified dosing strategies (e.g., constant NH 3 /NO x ratio) or strategies previously optimized for different catalysts during the early design phase’s simulation and laboratory studies. This paper presents a practical, model-based approach that allows for simulation and laboratory studies to be performed with an individually adapted dosing profile. The procedure is based on conventional feedback control strategies, where the average ammonia storage level is controlled using a temperature dependent setpoint (the desired storage level), which is interpolated from a look-up table. The approach of this paper is to optimize numerically the entries of this look-up table for a given test cycle such that the NO x conversion is maximized while the ammonia slip is kept below a defined level. Although the optimization is performed for a particular cycle, it is demonstrated that the dosing strategies obtained in this way also work reasonably well for other test cycles. The proposed procedure was applied in a catalyst screening simulation study that compared the performance of an Fe– and a Cu–zeolite catalyst for a given test cycle. It was demonstrated that each of the two catalysts appeared to have a better performance than the other catalyst when the specified catalyst’s optimized dosing profile was applied to both catalysts. The best catalyst was only identified when comparing both catalysts using their own respective optimized dosing profile. A second simulation study used the proposed dosing procedure to compare catalysts with different ammonia storage capacities. Again, the relative ranking of the catalysts’ performance was shown to depend on the dosing profile. Overall it is demonstrated that the true potential of a catalyst can only be determined when an individually adapted dosing strategy is used.

The effect of water on the selective gas phase oxidation of acrolein to acrylic acid on a Mo/V/W mixed oxide catalyst was studied by performing steady-state isotopic transient kinetic analysis experiments with H218O. Experiments were performed in the temperature range of 90–345 °C at ambient pressure. It could be shown that acrolein exchanges its carbonylic oxygen with oxygen from water even at low temperatures ( 200 °C), the oxygen atoms of the water molecules incorporate into all oxidation products such as acrylic acid, carbon monoxide, and carbon dioxide.

Oxidation of acrolein to acrylic acid on Mo/V/W-mixed oxide catalysts has been studied by means of the isotopic exchange method steady-state isotopic transient kinetic analysis (SSITKA). As a result of these isotopic exchanges performed with 16O2 and 18O2, some new mechanistic details could be obtained. Acrolein exchanges its oxygen with oxygen of the mixed oxide catalyst. Additionally, the kinetics of the different isotopologues is significantly influenced by oxygen exchange reactions between the surface and the bulk sites. From the SSITKA results, an extended reaction model has been deduced. Thus, the experimentally gained data of the individual isotopologue kinetics could be verified by modeling.

Upcoming legislation will most likely require the introduction of particulate filters for gasoline engines. One attractive technical solution combines the three way catalytic functionality and the filter in one device, the so called ‘catalysed Gasoline Particulate Filter’. The current study uses temperature step experiments and CO oxidation as a test reaction to compare the catalysed particulate filter and the conventional flow-through monolith with respect to their dynamic cold-start behaviour. Despite the fact that the two reactor configurations are tested with identical washcoat formulation, precious metal loading and thermal mass, experiments show a significantly delayed cold-start for the particulate filter. The resulting cumulated CO emissions of the catalysed filter exceed those of the open monolith by 190–300% in the temperature range between 250 °C and 325 °C. The experimental results are analysed by means of numerical simulation. In a first step a kinetic model of the CO oxidation is parameterised using only experimental data obtained for the conventional flow-through catalyst. The resulting kinetics are implemented in a model of the wall-flow filter. Without further modification of the kinetic parameters, this model quantitatively predicts the cold-start behaviour of the catalysed filter. Finally, the numerical model is used in a sensitivity analysis to identify and quantify the individual physical effects contributing to the experimentally observed difference in the light-off behaviour. It is shown that a part of the observed difference in the cold-start performance can be traced back to differences in cell density and the heat capacity of the plugs. Even at identical cell density and without the plug effect the filter shows significantly higher CO emissions. It is shown that this intrinsic difference between the filter and the conventional monolith can be quantitatively explained by differences in heat transfer, internal mass transfer and external mass transfer.

Die hydrothermale Carbonisierung (HTC) ist in Hinblick auf die energetische Verwertung von Biomasse eine vielversprechende Methode. Trotz der langen Historie dieses Verfahrens sind Mechanismus und Kinetik nur unzureichend verstanden. In den hier vorgestellten Experimenten wurde mithilfe der Kombination von Analysenmethoden die Umsetzung von Kohlenhydraten mit sauren und basischen Zusatzen untersucht. Dabei konnte vor allem der Einfluss von Saure auf die Hydrolyse von Cellulose beobachtet werden. Die HTC von Glucose hingegen bleibt weitestgehend von den Zusatzen wie Saure oder Base unbeeinflusst. Durch Veranderung der Reaktionsbedingungen wie der Heizrate konnen die Biokohle-Eigenschaften wie z. B. die Aciditat der Kohle variiert werden. In terms of energy recovery, the hydrothermal carbonization (HTC) is a promising method. Despite the long history of this process, the mechanism and kinetics are poorly understood. For tracing the reaction kinetics a combination of analysis methods has been used. In the presented study the HTC of carbohydrates is examined with addition of acid and base. Thereby, a major influence of acids on the hydrolysis of cellulose can be observed. The HTC of glucose, however, remains largely unaffected by these additives. Furthermore, it was observed that reduced heating rates lead to changes in the biochar acidity.

This paper demonstrates that the use of a solution-mapping approach can accelerate the simulation of a dual-layer ammonia oxidation catalyst by several orders of magnitude. In a first step, a 1-D + 1-D model of the dual-layer catalyst is set up. The results of this model are compared to the numerical solution of a 2-D model, and it is shown that the 1-D + 1-D model provides an accurate approximation of the full 2-D solution. In a second step, spline interpolation functions are constructed that map the solution of the mass balance equations for one axial volume element of the 1-D + 1-D model as a function of the inlet concentrations, temperature and residence time. During the runtime of the simulation, concentration profiles can be computed by simple successive calls of the interpolation function without the need for a numerical solver. The 5-dimensional spline functions reproduce the output concentrations of a reactor model with 35 axial volume elements with an accuracy of better than 1.25%. The use of the solution mapping reduces the computation time for a steady-state solution of the monolith model from 97.5 s down to 10 ms.

The influence of water on the selective gas phase oxidation of acrolein to acrylic acid on Mo/V/W-mixed oxides was investigated by means of temperature-programmed experiments. In the presence of water, the rate of the acrylic acid formation is significantly pronounced. Selectivity- and yield-maxima are broadened and shifted towards lower temperatures. Nonetheless, the combustion remains unaffected. Furthermore, the catalysts stability remains likewise unaffected within the range of the experiments.

Today, platinum based ammonia oxidation catalysts are applied in automotive exhaust systems to avoid ammonia slip from the SCR catalyst. In this paper we present a dual layer catalyst design with an additional SCR layer on top of the Pt/Al2O3 layer. Laboratory experiments show that the additional SCR layer significantly reduces NO formation, improves N2 selectivity but also reduces the overall NH3 conversion. A mechanistically based kinetic model for NH3 oxidation on platinum is presented. The model is parameterised using experiments with a single layer Pt/Al2O3 catalyst and well describes the NH3 conversion and the selectivities for the products N2, N2O and NO. Additionally NO oxidation to NO2 is included in the model. Based on the mechanistic model for the platinum layer and a previously published model for the SCR layer, a 2-D model of the dual layer catalyst is set up. This model takes into account the diffusion and reaction in the two washcoat layers of one monolith channel. The 2-D model reproduces the experimental data well, with the mechanisms for the two layers parameterised in separate experiments and no additional parameters adjusted for the dual layer model. Finally, the model is used to study the effect of some design parameters such as catalyst size, NO oxidation capacity of the Pt-layer and the thickness or diffusion coefficient of the SCR layer.

Mittels der Isotopenaustauschmethode SSITKA (steady-state isotopic-transient kinetic analysis) ergaben sich Ruckschlusse zum Mechanismus der Partialoxidation von Acrolein zu Acrylsaure an Mo/V/W-Mischoxidkatalysatoren. Der Isotopenaustausch erfolgte mit den beiden Sauerstoffisotopen 16O2 und 18O2. Dabei findet am Katalysator ein Austausch des Carbonylsauerstoffs im Acrolein mit Festkorpersauerstoff statt. Zusatzlich wird die Kinetik der unterschiedlichen Isotopologenspezies durch eine Austauschreaktion von Sauerstoff zwischen belegten und unbelegten Zentren an der Oberflache und in der Volumenphase des Katalysators signifikant beeinflusst. Gestutzt durch einen erweiterten Modellvorschlag zum Mechanismus konnten uber Simulationen die experimentell gewonnenen Isotopologenkinetiken verifiziert werden. The partial oxidation of acrolein to acrylic acid on Mo/V/W-mixed oxide catalysts has been studied by means of the isotopic exchange method SSITKA (steady-state isotopic-transient kinetic analysis). In the scope of isotopic exchanges performed with the oxygen isotopes 16O2 and 18O2 some new details could be gained regarding the mechanism. Acrolein exchanges its oxygen with oxygen of the solid catalyst. Additionally the kinetics of the different isotopologues is influenced by another exchange reaction of oxygen between vacant and occupied surface and bulk sites. From the SSITKA results an extended model has been deduced. So, the experimentally gained data of the individual isotopologue kinetics could be verified by simulation.

For a safe storage and handling of acrylic acid (AA), a lot of knowledge is necessary. In the present work, investigations were made in order to describe the stabilization processes during the inhibition period (IP) of AA more exactly. The oxygen and p-methoxyphenol consumption was determined for AA at 70 and 80 °C in an enhanced parameter range and simulated with a kinetic model, using the software Presto Kinetics (R). In the simulation accelerated stabilizer consumptions at 80 °C could be confirmed. The known stabilization mechanism must be enhanced with autocatalytic steps, which lead to an accelerated stabilizer consumption. Furthermore, the stability of AA was examined as a function of the dissolved oxygen mass fraction and the temperature in isoperibolic reactors. The IP follows an Arrhenius behavior; therefore, an extrapolation from higher reaction temperatures to storage conditions is possible. These measurements also confirm the nonlinear stabilizer consumption during the IP at temperatures over 75 °C.

Summary: Acrylic monomers are important intermediates for the chemical industry. Especially acrylic acid (AA) is the basis for various reactions, such as polymerizations and esterifications and is, therefore, responsible for high product diversity. Spontaneous polymerization is a safety problem during the transportation and storage of acrylic monomers. In the production process, polymerization leads to blockages in the apparatus. For the prevention of these issues, special stabilizer systems are used such as hydroquinone monomethyl ether (MeHQ)/oxygen and phenothiazine (PTZ). The reactions of these stabilizer systems are not well understood at the moment. Therefore a lot of expertise and experience are necessary to guarantee safe handling. In this paper some methods for the investigation of stability related reaction kinetics are presented. A better comprehension of the mechanism of the polymerization inhibition is generated by the kinetic simulation with these data.

Copper catalysis proceeds with multiple steady states and oscillations in several oxidation reactions. The understanding of such kinetic phenomena is essential for the control of copper-catalyzed industrial scale processes. Information about the reasons and the ranges of the parameters causing these kinetic effects will be given from results gained by concentration programmed reaction (CP-reaction) experiments. Elemental copper was used as unsupported catalysts and the oxidation of hydrogen and ethanol were introduced as model reactions. CP-reaction experiments were performed in a tubular reactor as well as in a differential thermal gravimetric analyzer (TG/DTA). The application of a TG/DTA as a reactor gave the opportunity for a simultaneous measurement of the activity and the grade of oxidation of the copper catalyst.

This paper demonstrates how pre-computed rate data can be used to enable the numerically efficient implementation of mechanistic kinetics in a reactor model for an automotive ammonia slip catalyst. In a pre-processing step the source terms for the gas species are mapped as a function of gas composition and temperature. From this map (80,000 data points), a spline interpolation function is constructed. The spline function approximates the numerical steady state solution of the kinetic model with an average error of less than 1%. Application of the rate mapping procedure results in a speedup of about two orders of magnitude. The spline approximation is implemented in a 2-dimensional model of a monolith reactor channel that includes diffusion in the washcoat layer. Depending on the channel diameter and the washcoat thickness, diffusion limitations in the open channel and in the washcoat can have a significant influence on the NH 3 conversion. Surprisingly, the selectivity for the products N 2 , N 2 O and NO is not sensitive to diffusion effects in the gas phase or in the washcoat.

The aim of this investigation is to quantify surface oxygen groups on an activated carbon by combining the results from temperature programmed desorption (TPD) and diffuse reflectance FT-IR spectroscopy (DRIFTS). A commercial activated carbon was oxidized with ozone to form surface oxygen groups. Afterwards the samples were heated in TPD experiments up to 500 °C. The evolved gases were detected and quantified via IR spectroscopy and DRIFT spectra were collected from the heat-treated samples. Simulation of the DRIFT spectra with a set of Gauss functions led to identification of four surface oxygen groups in the range of 1500–1950 cm −1 . Specific concentrations of the four groups can be calculated with the conversion factors obtained by combining TPD and DRIFTS information.

It is shown that a platinum catalyst operated under a transient temperature profile exhibits a hysteresis behavior. The catalytic activity during heat-up phases exceeds the activity of the cool down phases. This effect is the opposite of the well-known hysteresis that can be caused by the existence of multiple steady states or the thermal inertia of the catalyst. It is therefore referred to as ‘inverse hysteresis’. If the catalyst is operated at one temperature for a longer time, a steady state activity is observed that is in-between the higher activity of the transient heat-up and the lower activity of the transient cool down. The most likely explanation for the observed hysteresis behavior is a reversible oxidation of the platinum surface by NO2 and a reduction of the platinum surface by NO. A micro-kinetic surface mechanism including the reversible surface oxidation has been developed and implemented in a monolith reactor model. The observed hysteresis effects can be quantitatively reproduced by the numerical model. If the feed contains CO/NO/O2 an inverse hysteresis is observed for NO and CO oxidation. This means that in the presence of NO the hysteresis behavior of the CO oxidation switches from the typical standard hysteresis to an inverse hysteresis.

The setup of a detailed model for the NH3-SCR process on iron exchanged zeolite catalysts is described, which takes into account the reactions of NH3, NO and NO2 occurring under typical exhaust conditions. Validation experiments for a standard SCR gas mixture show that the model is able to describe the dynamic behaviour of this system at transient temperature conditions. The model is used for the parameterization of an ammonia dosing controller. To prove the functionality of this controller it was implemented on a synthetic gas test bench and tested by a dynamic temperature experiment. This setup allows the evaluation of the parameterized controller without any disturbances from engine or injection effects.

A microkinetic model is developed for the NO-oxidation on platinum. The approach we followed employs semi-empirical methods, optimization of the parameters of elementary-like reactions, and thermodynamic constraints. The model is capable of capturing reasonably light-off experimental data.

The oxidation of ammonia on a Pt/Al2O3 coated monolith has been studied under automotive NH3-slip catalyst conditions. Ammonia conversion as well as the selectivities towards the products N2, N2O and NO are well described by a mechanistic model that is based on reaction mechanisms originally developed for NH3 oxidation in nitric acid production plants.

BaCO 3 and Pt/BaCO 3 nanoparticles with high specific surface area (SSA) were prepared by flame spray pyrolysis (FSP). Their structure and behaviour during NO x storage were investigated with special focus on the mechanistic and kinetic details. NO exposure of BaCO 3 (BET: 45 m 2 g −1 ) at various temperatures resulted in simple NO adducts. Low NO storage rate and NO x storage capacity (NSC) were observed up to 400 °C. In the presence as well as the absence of oxygen, NO was stored on BaCO 3 showing the same IR-adsorption bands at 100–300 °C. Higher NSC and storage rates were observed for NO 2 adsorption. DRIFT spectra showed that NO 2 adsorption is accompanied by the formation of small amounts of NO which could be stored and subsequently oxidised again to NO 2 adducts. Pt/BaCO 3 prepared under identical conditions resulted in higher SSA (110 m 2 g −1 ) and showed increased NSC especially at higher temperatures. Enhanced DRIFT adsorption bands indicated the same NO adducts as obtained for the Pt-free BaCO 3 during NO treatment. In the presence of oxygen and above the light-off temperature for NO oxidation, the consecutive reaction of stored nitrite to nitrate could be observed by in situ DRIFTS. NO 2 adsorption led again to the highest NSC and storage rate. An optimal operation temperature window around 300 °C was found where the NO 2 storage rate was high and the catalysed competing NO 2 conversion to NO was low enough to afford maximal NSC. Structural investigations indicate that only prolonged NO x treatment leads to bulk barium nitrate: solid state conversion occurs after few hours. This supports the contention that the main contribution to NO x storage during technical application in NSR catalysis occurs in the surface and subsurface regions of BaCO 3 .

For the partial oxidation of acrolein to acrylic acid, a series of catalysts with the general formula Mo 8 V 2 W c O x and a varying amount of tungsten (0 ≤ c ≤ 5) was investigated. Catalysts were prepared starting from aqueous solutions of ammonium heptamolybdate, metavanadate and metatungstate, which were dried, employing spray drying and crystallisation followed by calcination. The resulting precursors and catalysts were characterised by XRD, SEM and TG/DTA–MS. Additionally, kinetic experiments were applied. Spray drying results in the formation of amorphous structures, whose temperature stability shows a tendency to rise with an increasing amount of tungsten. Spray dried samples in general show a better catalytic performance than crystallised ones. In TP-reactions the spray dried mixed oxides were investigated with regard to their catalytic properties: conversion of acrolein, yield and selectivity regarding the partial oxidation to acrylic acid. The best performance could be assigned to the minor tungsten doped catalysts. The oxygen pathways were investigated with the so-called steady state isotopic transient kinetic analysis (SSITKA). After the replacement of 16 O 2 against 18 O 2 in the feed gas, the rate of oxygen incorporation into the reactants and the isotopic distribution of the oxidation products were analysed depending on temperature and tungsten content. Tungsten doping has a significant influence on the amount of 16 O removed from the catalyst under 18 O 2 . The amount of oxygen made available by the catalysts correlates with the catalysts’ activity.

The storage of NO, NO/O2-mixtures and NO2 on CeO2 and BaO/CeO2 was investigated by in situ DRIFT-spectroscopy. The NOx-storage capacity, as well as the kinetic and the mechanism of the NOx-storage process are influenced by the temperature and the BaO-loading as well as the oxygen partial pressure. The addition of oxygen into NO containing gas mixtures results in the oxidation of the stored nitrite to nitrate species. Adsorption of NO2 leads to in the formation of nitrite and nitrate species, where the nitrite species are completely oxidized to nitrate in the progress of storage.