Suchergebnisse

Dieselruß ist einer der Hauptumweltschadstoffe, besonders in ökonomisch weit entwickelten Ländern, da dort die Zahl der Automobile mit Dieselmotor in den letzten Jahren ungemein zunimmt. Zwar waren Motorenveränderungen ausreichend um vorherige Verordnungen wie Euro 3 zu erfüllen, allerdings ist vorhersehbar, dass solche Veränderungen nicht ausreichend sein werden, um Zulassungen zukünftiger Dieselautos zu erlauben. Die Autoindustrie konzentriert ihre Anstrengungen nun auf die Entwicklung von Nachbehandlungssystemen. Der vielversprechendste Ansatz zur Entfernung von Dieselruß aus Dieselabgasen ist die Verwendung von Partikelfiltern zum Einfangen von Ruß aus Abgasen. Obwohl die Partikelfilter einen Durchbruch in Dieselrußentfernung mit sich brachten, musste dies mit einem Preis bezahlt werden, da der aufgefangene Ruß zur Erhöhung des Filterrückdruckes führt und als begleitender Nebeneffekt zu einem erhöhten Treibstoffverbrauch nachsichzieht. Ein raffinierter Weg um Filterverstopfung zu verhindern ist die Anwendung von Oxidationskatalysatoren im Filtersystem, die es erlauben werden den Filter zu regenerieren, bei im Abgas erreichbaren Temperaturen. Unser Ziel war die Suche nach edelmetallfreien Dieselruß-Oxidationskatalysatoren mit etablierten Methoden der kombinatorischen heterogenen Katalyse. Insgesamt wurden 1400 Materialien in 16 Bibliotheken auf die Oxidation von Ruß mittels Hochdurchsatzexperimenten untersucht. ; Diesel soot is one of the major environmental pollutants especially in the developed world where the number of cars running on diesel engine is tremendously on the raise. While engine modification was enough to allow diesel cars pass the previous legislation such as Euro 3, it is clear that such modifications are not enough to allow the certification of future diesel cars. The automobile industries are now concentrating their efforts in developing after-treatment systems. The most promising approach in eradicating diesel soot from diesel exhaust emission is the application of particulate filters that ...

[EN] The automotive industry is driven its efforts to cleaner internal combustion engines. As a result, the engine has become conditioned by the exhaust aftertreatment systems. The regeneration of wall-flow particulate filters (PFs) evidences such an interaction. The PFs prevent the soot emission whereas, as a counterpart, the fuel consumption increases. Consequently, passive and active regeneration strategies are needed to clean the filter back and limit the penalty in CO2. In this context, modelling tools play a key role to achieve a comprehensive understanding and control of the regeneration. In this work, a regeneration model coupled to a one-dimensional compressible unsteady flow solver for PFs is presented. The importance of the main physical and chemical steps related to the soot oxidation is discussed. The influence of the diffusion of gaseous reactants inside the primary soot particles is firstly addressed. The inclusion of this step into the definition of the reaction rate provides temperature dependence to the soot specific surface. Next, the reactants adsorption is analysed. This step leads to define a surface coverage, which behave as an equivalent reaction order. It allows figuring out the influence of the gaseous reactants concentration on the reaction rate and its dependence with the temperature. (C) 2019 Elsevier Ltd. All rights reserved. ; This research has been partially supported by FEDER and the Government of Spain through project TRA2016-79185-R. Additionally, the Ph.D. student Enrique José Sanchis has been funded by a grant from Universitat Politècnica de València with reference FPI-2016-S2-1355. ; Macian Martinez, V.; Serrano, J.; Piqueras, P.; Sanchis-Pacheco, EJ. (2019). Internal pore diffusion and adsorption impact on the soot oxidation in wall-flow particulate filters. Energy. 179:407-421. https://doi.org/10.1016/j.energy.2019.04.200 ; S ; 407 ; 421 ; 179

A series of BaFe1−xCuxO3 catalysts (x = 0, 0.1, 0.3 and 0.4) have been synthetized, characterized and used for soot oxidation in gasoline direct injection (GDI) exhaust conditions. The characterization of the catalysts (by BET, ICP-OES, XRD, XPS, H2-TPR and O2-TPD) reveals that copper is incorporated into the perovskite lattice leading to: (i) the distortion of the original hexagonal perovskite structure for the lowest copper content catalyst (BFC1) and the modification of the structure, from hexagonal to cubic, for the catalysts with higher copper content (BFC3 and BFC4), (ii) the generation of a BaOx–CuOx oxide as minority segregated phase for BFC4 catalyst, (iii) the increase in the amount of oxygen surface vacancies for BFC3 and BFC4 catalysts, and (iv) the decrease in the total amount of O2 released during O2-TPD experiments. All the BaFe1−xCuxO3 perovskites are active for soot oxidation under the highest demanding GDI exhaust conditions (regular stoichiometric GDI operation, i.e., 0% O2). The catalyst with the highest copper content (BFC4) shows the highest soot conversion, related to its largest amount of β-oxygen evolved, and, to the presence of a high amount of copper species (as BaOx–CuOx oxide) on its surface. ; The authors thank Generalitat Valenciana (PROMETEO/2018/076), Spanish Government (MINECO Project CTQ2015-64801-R) and UE (FEDER Founding) for the financial support. V. Torregrosa-Rivero thanks the Generalitat Valenciana for her Ph.D. Grant (ACIF 2017/221).

Y-doped ceria–zirconia (Ce0.8Zr0.12Y0.08O2-d, CZY) and ceria–lanthana (Ce0.8La0.12Y0.08O2-d, CLY) ternary oxide solid solutions were synthesized by a facile coprecipitation method. Structural, textural, redox, and morphological properties of the synthesized samples were investigated by means of X-ray diffraction (XRD), inductively coupled plasma-optical emission spectroscopy (ICP– OES), Raman spectroscopy (RS), UV–visible diffuse re- flectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H2-TPR), high resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller surface area (BET SA) techniques. The formation of ternary oxide solid solutions was confirmed from XRD, RS, and UV–vis DRS results. ICP–OES analysis confirmed the elemental composition in the ternary oxide solid solutions. HRTEM images revealed irregular morphology of the samples. RS, UV–vis DRS, and XPS results indicated enhanced oxygen vacancies in the Y doped samples. H2- TPR profiles confirmed a facile reduction of CZY and CLY samples at lower temperatures. BET analysis revealed an enhanced surface area for CZY and CLY samples than the respective CZ and CL undoped mixed oxides. All these factors contributed to a better CO and soot oxidation performance of CZY and CLY samples. Particularly, the CLY sample exhibited highest catalytic activity among the various samples investigated. ; We gratefully acknowledge Department of Science and Technology (DST), New Delhi for financial support of this work (SERB Scheme SB/S1/PC-106/2012). D.D. thanks the Department of Education, Australian Government for providing Endeavour Research Fellowship.

Y-doped ceria–zirconia (Ce0.8Zr0.12Y0.08O2-d, CZY) and ceria–lanthana (Ce0.8La0.12Y0.08O2-d, CLY) ternary oxide solid solutions were synthesized by a facile coprecipitation method. Structural, textural, redox, and morphological properties of the synthesized samples were investigated by means of X-ray diffraction (XRD), inductively coupled plasma-optical emission spectroscopy (ICP–OES), Raman spectroscopy (RS), UV–visible diffuse re- flectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H2-TPR), high resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller surface area (BET SA) techniques. The formation of ternary oxide solid solutions was confirmed from XRD, RS, and UV–vis DRS results. ICP–OES analysis confirmed the elemental composition in the ternary oxide solid solutions. HRTEM images revealed irregular morphology of the samples. RS, UV–vis DRS, and XPS results indicated enhanced oxygen vacancies in the Y doped samples. H2- TPR profiles confirmed a facile reduction of CZY and CLY samples at lower temperatures. BET analysis revealed an enhanced surface area for CZY and CLY samples than the respective CZ and CL undoped mixed oxides. All these factors contributed to a better CO and soot oxidation performance of CZY and CLY samples. Particularly, the CLY sample exhibited highest catalytic activity among the various samples investigated. ; We gratefully acknowledge Department of Science and Technology (DST), New Delhi for financial support of this work (SERB Scheme SB/S1/PC-106/2012). D.D. thanks the Department of Education, Australian Government for providing Endeavour Research Fellowship.

A series of BaMnO3 solids (BM-CX) were prepared by a modified sol-gel method in which a carbon black (VULCAN XC-72R), and different calcination temperatures (600–850 °C) were used. The fresh and used catalysts were characterized by ICP-OES, XRD, XPS, FESEM, TEM, O2-TPD and H2- TPR-. The characterization results indicate that the use of low calcination temperatures in the presence of carbon black allows decreasing the sintering effects and achieving some improvements regarding BM reference catalyst: (i) smaller average crystal and particles size, (ii) a slight increase in the BET surface area, (iii) a decrease in the macropores diameter range and, (iv) a lower temperature for the reduction of manganese. The hydrogen consumption confirms Mn(III) and Mn(IV) are presented in the samples, Mn(III) being the main oxidation state. The BM-CX catalysts series shows an improved catalytic performance regarding BM reference catalyst for oxidation processes (NO to NO2 and NO2-assisted soot oxidation), promoting higher stability and higher CO2 selectivity. BM-C700 shows the best catalytic performance, i.e., the highest thermal stability and a high initial soot oxidation rate, which decreases the accumulation of soot during the soot oxidation and, consequently, minimizes the catalyst deactivation. ; This research was funded by the Generalitat Valenciana (PROMETEO/2018/076), Spanish Government (PID2019-105542RB-I00) and the EU (FEDER Founding).

A series of BaMn0.7Cu0.3O3 solids were prepared by a modified sol-gel method in which carbon black (VULCAN XC-72R), and different calcination temperatures (BMC3-CX, where X indicates the calcination temperature) have been used. The fresh and used catalysts were characterized by ICP-OES, XRD, XPS, FESEM, TEM, O2-TPD and H2-TPR. The presence of a carbon black during sol-gel synthesis of BMC3 mixed oxide allows diminishing the calcination temperature needed to achieve the perovskite structure, but it hinders the formation of the BaMnO3 polytype. The use of low calcination temperatures during synthesis reduces the sintering effects, and the mixed oxides present lower particle size, slightly higher BET surface areas and macropores with lower diameter than BMC3. The distribution of copper in BMC3-CX catalysts depends on the calcination temperature and copper insertion into the perovskite structure is promoted as the calcination temperature increases. All BMC3-CX catalysts are active for NO to NO2 and NOx-assisted soot oxidation processes, but only BMC3-C600 and BMC3-C700 show higher catalytic activity than BMC3 reference catalyst. BMC3-C600 presents the best performance as it features a high amount of surface copper and oxygen vacancies that increase during reaction. The comparison between the performance of the two best catalysts of the BM-CX series (BM-C700) and the BMC3-CX series (BMC3-C600) suggests that the unique advantage of using copper in the modified sol-gel synthesis is an additional decrease of 100 °C in the calcination temperature used for the synthesis of the best catalyst, which is 700 °C for BM-CX and 600 °C for BMC3-CX. ; This research was funded by Spanish Government (PID2019-105542RB-I00) and EU (FEDER Founding).

The activity for NO oxidation and for NO2-assisted diesel soot removal of a BaMn1−xCuxO3 (x = 0, 0.1, 0.2, 0.3) perovskite-type catalyst has been tested by Temperature Programmed Reaction (TPR) and isothermal experiments at 450 °C. Fresh and used catalyst characterization by ICP-OES, N2 adsorption, XRD, XPS, IR spectroscopy and H2-TPR was performed. Results showed that: (i) manganese is partially substituted by copper in the perovskite structure leading to the formation of a manganese-deficient perovskite with a new hexagonal structure, (ii) in BaMn1−xCuxO3 catalysts, manganese seems to be mainly Mn(III) and, as a consequence, the amount of oxygen vacancies increases gradually with the copper content and (iii) the presence of copper into the perovskite structure enhances the reducibility of the catalyst and increases the mobility of lattice oxygen. BaMn0.7Cu0.3O3 is the most active catalyst for NO2 generation and, consequently, shows the lowest T50% value, the highest CO2 selectivity, the best performance during TPR cyclic experiments, and the highest soot oxidation rate at 450 °C. This behavior is a result of the enhancement of the redox properties of the catalyst due to the replacement of Mn(III)/Mn(IV) by Cu(II) in the perovskite structure. ; The authors thank Spanish Government (MINECO project CTQ2015-64801-R), the European Union (FEDER) and the Generalitat Valenciana (Project PROMETEOII/2014/10) for the financial support. Vicente Albaladejo-Fuentes thanks the University of Alicante for his Ph.D. grant and Veronica Torregrosa-Rivero thanks SECAT for her "Introduction to Research" grant.

Mit der fortschreitenden Verschärfung der Abgasgrenzwerte für PKW mit Dieselmotor gewinnen die Verfahren zur nachmotorischen Abgasreinigung immer weiter an Bedeutung. Diesel-Partikelfilter erlauben zusammen mit innermotorischen Maßnahmen eine nahezu vollständige Reduktion von Partikeln in dieselmotorischen Abgasen. Ziel der vorliegenden Arbeit war es daher, Abgasreinigungssysteme mit Diesel-Oxidationskatalysator (DOC) und nachgeschaltetem monolithischem Wall-flow Diesel-Partikelfilter eingehend zu untersuchen und modellmäßig zu beschreiben. Der Schwerpunkt lag dabei auf der Regeneration von katalytisch beschichteten (CDPF) sowie unbeschichteten (DPF) Partikelfiltern. Als Oxidationskomponenten wurden O2 und NO2 betrachtet. Auch auf das Potenzial eines Systems, in dem ein katalytisch beschichtetes Partikelfilter die Funktionen eines DOC vollständig übernimmt, wurde eingegangen. Um die physikalischen und chemischen Vorgänge im Oxidationskatalysator und in den Partikelfiltern bestmöglich verstehen und beschreiben zu können, wurden sowohl experimentelle Untersuchungen als auch dynamische Simulationsrechnungen durchgeführt. Es wurden hierzu u. a. Filterproben mit Modellruß beladen und anschließend unter isothermen und definierten synthetischen Abgasbedingungen in einem speziell dafür entwickelten Kinetikprüfstand regeneriert. Ausgehend von diesen Reaktionsanalysen und Reaktionsanalysen zu weiteren ausgewählten Stoffkomponenten, die das dieselmotorische Abgas repräsentieren, wurden Bruttoreaktionskinetiken für die Stoffumsetzungen im DOC und im Diesel-Partikelfilter abgeleitet. Zur qualitativen und quantitativen Beschreibung der Schadstoff- und Rußumwandlung wurde für den Katalysator und das Partikelfilter jeweils ein eindimensionales Simulationsmodell entwickelt. Die Modelle erlauben dynamische Vorhersagen zur Schadstoffumsetzung und Temperaturentwicklung längs der axialen Katalysator- sowie der axialen Filterkoordinate und ermöglichen somit Systemanalysen zu unterschiedlichen Abgasreinigungsanlagen. Das Filtermodell unterscheidet dabei die Modellphasen Einlass- und Auslasskanal sowie Rußschicht und Filterwand. Auch das komplexe Zusammenspiel zwischen Rußoxidation und heterogen katalysierten Reaktionen in katalytisch beschichteten Partikelfiltern konnte so in die Untersuchungen und in das Simulationsmodell mit einbezogen werden. Die Ergebnisse der vorliegenden Arbeit machen deutlich, dass für ein gesamtes Abgasreinigungssystem, bestehend aus einem Oxidationskatalysator und einem Partikelfilter, die Temperatur die wesentliche Steuergröße darstellt. Es ist somit auf möglichst geringe Wärmeverluste zu achten. Bei Verwendung eines beschichteten Partikelfilters kann je nach Systemauslegung auch ein verkleinerter DOC zum Einsatz kommen. Neben den Wärmeverlusten kommt auch der Wärmekapazität der einzelnen Abgasnachbehandlungskomponenten eine entscheidende Rolle zu. Abschließend lässt sich festhalten, dass mit den hier entwickelten Modellen und den Reaktionsgeschwindigkeitsansätzen nicht nur die Rußabbrandraten und die lokalen Temperaturentwicklungen im DOC und im Partikelfilter, sondern auch erstmals die Produktselektivitäten sowie die Abbrandinitiierung vorhergesagt werden können. Es stehen somit Berechnungsmethoden zur Verfügung, die sowohl eine grundlagenorientierte Betrachtung der einzelnen physikalischen und chemischen Vorgänge im Partikelfilter als auch Systemanalysen zu Gesamtabgasreinigungssystemen mit Diesel-Oxidationskatalysator und Diesel-Partikelfilter erlauben. ; As the legislation concerning the emission limits for passenger cars with diesel engines is getting more and more restrictive, systems for exhaust gas aftertreatment will become increasingly important. Diesel particulate filters combined with special measures for the internal combustion process are able to reduce soot particulates in diesel exhaust gas almost completely. Therefore, the intention of this work is to investigate exhaust gas aftertreatment systems consisting of a diesel oxidation catalyst (DOC) and a particulate filter (DPF) or a catalytically coated particulate filter (CDPF) and to build up one-dimensional models to describe the most dominant processes. The main focus regards the regeneration processes within the particulate filters. According to recent exhaust purification concepts, the oxidation catalyst is not only reducing the raw emissions of the engine, but it will be supporting soot oxidation by post injected diesel fuel in order to provide the required high filter regeneration temperatures. The catalyst also generates NO2 from exhaust NO. NO2 acts as an oxidant for soot at lower temperatures. A catalytically coated filter comprises the function of a catalyst within the filter itself and promotes the oxidation of soot. In order to regenerate particulate filters, the loaded soot can be oxidized by the exhaust gas components O2 and NO2. The filter regeneration with O2 requires high temperatures well above 600°C to oxidize the soot within acceptable times. Due to the high O2 concentration the resulting reaction rates can be much higher than those obtained by NO2, which, on the other hand, can be used for soot oxidation at lower temperatures above 280°C. In order to analyse and understand the coupled physical and chemical processes within a catalyst and a particulate filter, both experimental investigations and dynamic simulations were performed and examined. Therefore a special test bench for reaction kinetics was developed and built up where the reactions could be investigated under defined, isothermal, synthetical and stationary conditions in a flat bed reactor. The catalyst samples as well as the filter samples were cut from real monoliths for passenger cars. Thus the results derived from the test bench can be easily transfered to real exhaust gas aftertreatment systems. On the basis of the experimental results obtained by the reaction analysis the reaction kinetics and parameters were determined. Furthermore, two one-dimensional mathematical models were developed to predict the conversion of the exhaust gas components and the soot oxidation within the catalyst and the filter both qualitatively and quantitatively. With these models dynamic calculations of the conversion of the gas pollutants as well as the developments of the temperature at every axial position of the catalyst and the filter can be performed. The model for the oxidation catalyst was set up as a two-phase model in order to exactly describe the mass and heat transfer between the gas phase and the catalytical solid phase. The model for the particulate filter is divided into four model phases: inlet and outlet channel as well as soot layer and filter wall. So, the complex interactions between soot burning and the catalytical reactions within catalytically coated particulate filters could be included in the investigations and simulations. The results of this work reveal that temperature is the key parameter to control the regeneration processes in an exhaust aftertreatment system consisting of an oxidation catalyst and a particulate filter. So, the heat losses should be reduced as much as possible. By using a catalytically coated filter it is also possible to employ a DOC of smaller size depending on the overall system design. However, not only the heat losses, but also the heat capacity of the single components of the aftertreatment system plays an important role with regard to the overall temperature management. Concluding, the models developed in this work and the reaction kinetics not only allow to predict the rates of soot burning and the development of the local temperature within oxidation catalysts and particulate filters but also to predict the selectivity of the reaction products and the initiation of the soot oxidation process. Thus, methods and simulation tools were provided which allow deeper insight into the single physical and chemical processes within a particulate filter for research topics and which allow the analysis of complete exhaust aftertreatment systems consisting of an oxidation catalyst and a particulate filter.

BaFe1-xCuxO3 perovskites (x = 0, 0.1, 0.3 and 0.4) have been synthetized, characterized and tested for soot oxidation in both Diesel and Gasoline Direct Injection (GDI) exhaust conditions. The catalysts have been characterized by BET, ICP-OES, SEM-EDX, XRD, XPS, H2-TPR and O2-TPD and the results indicate the incorporation of copper in the perovskite lattice which leads to: i) the deformation of the initial hexagonal perovskite structure for the catalyst with the lowest copper content (BFC1), ii) the modification to cubic from hexagonal structure for the high copper content catalysts (BFC3 and BFC4), iii) the creation of a minority segregated phase, BaOx-CuOx, in the highest copper content catalyst (BFC4), iv) the rise in the quantity of oxygen vacancies/defects for the catalysts BFC3 and BFC4, and v) the reduction in the amount of O2 released in the course of the O2-TPD tests as the copper content increases. The BaFe1-xCuxO3 perovskites catalyze both the NO2-assisted diesel soot oxidation (500 ppm NO, 5% O2) and, to a lesser extent, the soot oxidation under fuel cuts GDI operation conditions (1% O2). BFC0 is the most active catalysts as the activity seems to be mainly related with the amount of O2 evolved during an. O2-TPD, which decreases with copper content. ; This research was funded by the Generalitat Valenciana (PROMETEO/2018/076 and Ph.D. Grant ACIF/2017/221 for V.Torregrosa-Rivero), Spanish Government (MINECO Project CTQ2015-64801-R), and EU (FEDER Founding).