Ανάπτυξη καινοτόμων καταλυτικών συστημάτων μέσω της συνέργειας δομικών και επιφανειακών προωθητών για τον περιορισμό των εκπομπών υποξειδίου του αζώτου (N2O)

Nitrous oxide (N2O) is recognized as one of the six most powerful greenhouse gases and also as one of the most important ozone depleting agents. Among several after-treatment techniques developed for N2O abatement, direct catalytic decomposition of N2O (deN2O process) seems to be one of the most promising methods. The deN2O process has been studied on various catalytic systems, such as transition and noble metal catalysts, perovskites, hexaluminates, spinels, zeolites. In this thesis, the deN2O performance of noble and transition metal oxides supported on different carriers is systematically explored. The physicochemical characterisitics of the as prepared catalysts is appropriately adjusted by means of two different approaches (a) advanced synthesis routes and/or (b) electronic and/or structure promoters, toward the rational design of novel and highly active catalytic materials. In the first set of experiments the deN2O performance of Al2O3 supported, low content (0.25, 0.5 and 1.0 wt. %) noble metal (Pt, Pd, Ir) catalysts, is comparatively explored in the temperature range of 300-600ο C both in the presence and absence of oxygen excess. It was found that the deN2O activity of all catalytic samples is notably suppressed by the presence of oxygen in the feed stream, while it is generally increased upon increasing metal loading, a fact being more intense over Ir- and Pd-based catalysts. This can be ascribed to the formation of metal oxide phases (IrO2 and PdO), not easily susceptible to oxygen poisoning. Modification of alumina support with structure promoters (CeO2 and La2O3) was also investigated, demonstrating the optimum deN2O performance of CeO2-modified Ir/Al2O3 (Ir/AlCe) catalyst in the presence of oxygen. The superiority of Ir/AlCe sample is interpreted on the basis of the N2O decomposition mechanism which is enabled by the establishment of a certain Irδ+/Ιr0 ratio and oxygen vacant sites (Vο) concentration in ceria around very small Ir particles under oxidative reaction conditions. Finally, it was demonstrated that potassium-doping under oxygen excess conditions has a pronounced effect on the deN2O activity of Ir/Al2O3 catalyst, which is correlated to the increase of catalyst’s surface basicity as well as to the formation of IrO2, in which desorption of adsorbed oxygen species is facilitated.Taking into account the unique properties and the application of gold nanoparticles in several heterogeneous catalysis processes, the second part of the present thesis was devoted on the deN2O performance of Au-based nanoparticles (Au/MxOy). In particular, the effect of support nature (MxOy: Al2O3, CeO2, Fe2O3, TiO2 and ZnO) on the deN2O performance of Au-based catalysts is extensively explored. For comparison purposes the corresponding performance of bare oxides is also investigated. It was revealed that gold nanoparticle size distribution along with the formation of partially oxidized Au+ species, are accounted for the optimum deN2O performance of Au/Fe2O3 catalysts.Finally, the critical role of synthesis procedure and/or electronic promotion on the solid state properties and the deN2O performance of CuO-CeO2 mixed oxides were explored in Chapter V. CuO-CeO2 single or mixed oxides prepared by different routes, i.e., impregnation, precipitation and exotemplating were tested for N2O decomposition both in the absence and presence of O2 excess. CuO-CeO2 mixed oxides, prepared by co-precipitation demonstrated the optimum catalytic performance, in terms of activity, stability and oxygen tolerance. The potential of further adjusting the surface chemistry of the pre-optimized catalyst through the co-precipitation technique, by means of alkali (Cs) promotion was also investigated. The results revealed that alkali loading equal to 1.0 at Cs/nm2 can boost the deN2O performance. This can be ascribed to their excellent reducibility as well as to the facilitation of Ce4+/Ce3+ and Cu2+/Cu+ redox cycles.Το υποξείδιο του αζώτου (Ν2Ο) έχει αναγνωριστεί ως ένα από τα πλέον επικίνδυνα αέρια του θερμοκηπίου ενώ παράλληλα συμβάλλει στην αραίωση του στρατοσφαιρικού όζοντος. Μεταξύ των αντιρρυπαντικών τεχνολογιών που έχουν αναπτυχθεί για τον έλεγχο των εκπομπών Ν2Ο, η απευθείας καταλυτική διάσπαση αποδεικνύεται ως η πλέον υποσχόμενη και αποτελεσματική μέθοδος. Η καταλυτική διάσπαση του Ν2Ο έχει μελετηθεί σε πληθώρα καταλυτικών συστημάτων, μεταξύ των οποίων σε καταλύτες ευγενών μετάλλων και μετάλλων μετάπτωσης, περοβσκίτες, σπινέλια και ζεόλιθους. Στην παρούσα διατριβή μελετάται εκτενώς η διάσπαση του Ν2Ο σε καταλύτες ευγενών μετάλλων και μετάλλων μετάπτωσης, υποστηριγμένους σε διάφορους φορείς. Η βελτιστοποίηση των εγγενών χαρακτηριστικών των μεικτών οξειδίων επιτυγχάνεται δια μέσου δυο κυρίως διαφορετικών προσεγγίσεων, οι οποίες μπορούν να εφαρμοστούν ανεξάρτητα ή παράλληλα: εφαρμογή προηγμένων μεθόδων σύνθεσης ή/και χρήση κατάλληλων δομικών ή επιφανειακών ενισχυτών, με απώτερο σκοπό το σχεδιασμό καινοτόμων καταλυτών υψηλής ενεργότητας. Επιπλέον, η απευθείας καταλυτική διάσπαση του Ν2Ο χρησιμοποιείται ως αντίδραση-ιχνηλάτης συμβάλλοντας στη διερεύνηση της επίδρασης της μεθόδου παρασκευής στην αλληλεπίδραση μετάλλου-φορέα, στην κατανόηση του μηχανισμού δράσης των προωθητών και σε πιθανή σχέση δομής-ενεργότητας.Στα πρώτα πειράματα που διεξάχθηκαν μελετάται η διάσπαση του Ν2Ο παρουσία και απουσία περίσσειας Ο2, σε καταλύτες χαμηλής φόρτισης (0.25, 0.5 και 1% κ.β.) σε ένα μόνο ευγενές μέταλλο (Pt, Pd ,Ir) εναποτεθειμένους σε φορέα γ-Al2O3. Η ενεργότητα όλων των καταλυτών παρεμποδίζεται από την παρουσία οξυγόνου στο ρεύμα τροφοδοσίας ενώ διαπιστώνεται ότι ενισχύεται με την αύξηση της μεταλλικής φόρτισης. Διαπιστώνεται η ανωτερότητα των καταλυτών Pd και Ir, η οποία αποδίδεται στο σχηματισμό οξειδωμένων φάσεων (IrO2 and PdO) που ευνοούν την ταχύτερη απομάκρυνση των ροφημένων ειδών οξυγόνου και την απελευθέρωση ενεργών θέσεων για περαιτέρω αντίδραση. Η τροποποίηση της αλουμίνας δια μέσου σπάνιων γαιών (CeΟ2 ή/και La2Ο3) ανέδειξε την ευεργετική επίδραση των δομικών ενισχυτών στην deN2O απόδοση των καταλυτών. Οι ενισχυμένοι με CeO2 καταλύτες (Ir/AlCe) παρουσιάζουν υψηλή ενεργότητα ιδιαίτερα σε οξειδωτικές συνθήκες αντίδρασης. Η συμπεριφορά αυτή ερμηνεύεται με βάση τον όξειδοαναγωγικό μηχανισμό που ακολουθεί η διάσπαση του Ν2Ο, ο οποίος φαίνεται ότι ευνοείται από την επίτευξη συγκεκριμένης αναλογίας Irδ+/Ιr0, καθώς και από την ύπαρξη κενών θέσεων οξυγόνου (Vo) στο πλέγμα της CeO2, γύρω από τα μικρού μεγέθους σωματίδια ιριδίου. Τέλος, διαπιστώθηκε η ευεργετική δράση των ηλεκτροθετικών προωθητών σε καταλύτες Ir/Al2O3. Η προσθήκη 0.5 κβ % Κ σε καταλύτες Ir/Al2O3 ευνοεί τον σχηματισμό σωματιδίων IrO2, διευκολύνοντας την εκρόφηση των προσροφημένων ειδών οξυγόνου.Λαμβάνοντας υπόψη τις μοναδικές ιδιότητες και την ευρεία εφαρμογή των νανοσωματιδίων χρυσού σε διάφορες διεργασίες ετερογενούς κατάλυσης, τα επόμενα πειράματα διεξάχθηκαν σε νανοδομημένους καταλύτες χρυσού (Au/MxOy) με σκοπό να διερευνηθεί η επίδραση της φύσης του φορέα (MxOy: Al2O3, CeO2, Fe2O3, TiO2 and ZnO) καθώς και των αλληλεπιδράσεων μετάλλου-φορέα στην deN2O απόδοση των καθαρών και των μεικτών (Au/MxOy) οξειδίων. Τα αποτελέσματα υπέδειξαν ότι η βέλτιστη απόδοση των καταλυτών Au/Fe2O3 οφείλεται στην κατανομή μεγέθους των σωματιδίων χρυσού και το σχηματισμό μερικών οξειδωμένων ειδών Au+.Τέλος, μελετήθηκε η σημαντική επίδραση της μεθόδου σύνθεσης ή/και της ηλεκτρονιακής προώθησης στις επιφανειακές ιδιότητες του καθαρού CeO2 και των οξειδίων CuO-CeO2. Σε πρώτο στάδιο πραγματοποιήθηκε η σύνθεση απλών ή μεικτών οξειδίων CuO-CeO2 με διάφορες τεχνικές π.χ. εμποτισμός, συγκαταβύθιση, καθώς και με την τεχνική εξωτερικού σκληρού εκμαγείου (exotemplating). Τα υλικά που παρασκευάστηκαν ελέγχθηκαν ως προς την ενεργότητα τους στην αντίδραση διάσπασης του Ν2Ο παρουσία και απουσία περίσσειας Ο2. Τα μεικτά οξείδια που παρασκευάστηκαν με την μέθοδο της συγκαταβύθισης (Ce-Cu-pp), παρουσίασαν τη βέλτιστη deN2O συμπεριφορά καθώς και υψηλή σταθερότητα και αντοχή στην παρουσία οξυγόνου. Σε δεύτερο στάδιο διερευνήθηκε το ενδεχόμενο περαιτέρω τροποποίησης/ενίσχυσης της επιφανειακής χημείας των καταλυτών (Ce-Cu-pp) μέσω της χρήσης επιφανειακών ενισχυτών, και συγκεκριμένα αλκαλίων (Cs). Τα αποτελέσματα έδειξαν μια ισχυρή ενίσχυση της καταλυτικής διάσπασης του Ν2Ο σε καλύψεις προωθητή ~ 1.0 at/nm2, η οποία αποδίδεται στις εξαιρετικές αναγωγικές ιδιότητες αλλά και στη διευκόλυνση των Ce4+/Ce3+ and Cu2+/Cu+ οξειδοαναγωγικών κύκλων

Ceria Nanoparticles’ Morphological Effects on the N2O Decomposition Performance of Co3O4/CeO2 Mixed Oxides

Ceria-based oxides have been widely explored recently in the direct decomposition of N2O (deN2O) due to their unique redox/surface properties and lower cost as compared to noble metal-based catalysts. Cobalt oxide dispersed on ceria is among the most active mixed oxides with its efficiency strongly affected by counterpart features, such as particle size and morphology. In this work, the morphological effect of ceria nanostructures (nanorods (ΝR), nanocubes (NC), nanopolyhedra (NP)) on the solid-state properties and the deN2O performance of the Co3O4/CeO2 binary system is investigated. Several characterization methods involving N2 adsorption at −196 °C, X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (ΤΕΜ) were carried out to disclose structure–property relationships. The results revealed the importance of support morphology on the physicochemical properties and the N2O conversion performance of bare ceria samples, following the order nanorods (NR) > nanopolyhedra (NP) > nanocubes (NC). More importantly, Co3O4 impregnation to different carriers towards the formation of Co3O4/CeO2 mixed oxides greatly enhanced the deN2O performance as compared to bare ceria samples, without, however, affecting the conversion sequence, implying the pivotal role of ceria support. The Co3O4/CeO2 sample with the rod-like morphology exhibited the best deN2O performance (100% N2O conversion at 500 °C) due to its abundance in Co2+ active sites and Ce3+ species in conjunction to its improved reducibility, oxygen kinetics and surface area

CO2 Hydrogenation over Nanoceria-Supported Transition Metal Catalysts: Role of Ceria Morphology (Nanorods versus Nanocubes) and Active Phase Nature (Co versus Cu)

In this work we report on the combined impact of active phase nature (M: Co or Cu) and ceria nanoparticles support morphology (nanorods (NR) or nanocubes (NC)) on the physicochemical characteristics and CO2 hydrogenation performance of M/CeO2 composites at atmospheric pressure. It was found that CO2 conversion followed the order: Co/CeO2 > Cu/CeO2 > CeO2, independently of the support morphology. Co/CeO2 catalysts demonstrated the highest CO2 conversion (92% at 450 °C), accompanied by 93% CH4 selectivity. On the other hand, Cu/CeO2 samples were very selective for CO production, exhibiting 52% CO2 conversion and 95% CO selectivity at 380 °C. The results obtained in a wide range of H2:CO2 ratios (1–9) and temperatures (200–500 °C) are reaching in both cases the corresponding thermodynamic equilibrium conversions, revealing the superiority of Co- and Cu-based samples in methanation and reverse water-gas shift (rWGS) reactions, respectively. Moreover, samples supported on ceria nanocubes exhibited higher specific activity (µmol CO2·m−2·s−1) compared to samples of rod-like shape, disclosing the significant role of support morphology, besides that of metal nature (Co or Cu). Results are interpreted on the basis of different textural and redox properties of as-prepared samples in conjunction to the different impact of metal entity (Co or Cu) on CO2 hydrogenation process

Remarkable efficiency of Ni supported on hydrothermally synthesized CeO2 nanorods for low-temperature CO2 hydrogenation to methane

project code: T1EDK-00094 IF/01381/2013/CP1160/CT0007 UIDB/50020/2020 UIDB/50006/2020Nickel particles deposited on hydrothermally synthesized ceria nanorods (CeO2-NR) were found to be highly active and stable for CO2 methanation. A CO2-to-CH4 yield of 92% was achieved at 300 °C. The impact of various operational parameters was explored in conjunction with a thermodynamic analysis. The superior performance of Ni/CeO2-NR was demonstrated through a comparison with i) CeO2 and Ni/CeO2 commercial products, ii) various M/CeO2-NR lab-synthesized catalysts (M = Cu, Co, Fe), and iii) state-of-the-art literature catalysts. The results revealed that a unique combination of Ni with ceria nanorods is required for boosting the reducibility and in turn the methanation efficiency.authorsversionpublishe

Erratum: Effect of alkali (Cs) doping on the surface chemistry and CO2hydrogenation performance of CuO/CeO2catalysts [Journal of CO2 Utilization (2021) 44 (101408) DOI: 10.1016/j.jcou.2020.101408)

The publisher regrets that the printed version of the above article contained a number of typo errors inserted during proofing process. The publisher would like to apologise for any inconvenience caused. In particular: • The units throughout the text must be in the form A/B instead of A/ B-1, i.e., cm3/min, °C/min, μmol/g, gcat/m3, mol/m3, m2/s instead of cm3/min-1, °C/min-1, μmol/g-1, gcat/m-3, mol/m-3, m2/s-1, respectively. • In the definition of turnover frequency (Eq. (6)) the term B must be defined as the total CO2uptake in μmol/g, i.e. "⋯derived by the total CO2uptake in μmol/g (B) calculated by CO2-TPD measurements" instead of "⋯derived by the total CO2uptake in 40 μmol/g (B) calculated by CO2-TPD measurements". • The y-axis in Figure 7 must be dimensionless, i.e., ln(TOF) instead of ln(TOF) (s-1).publishersversionpublishe

MODEL2BIO. Modelling tool for giving value to agri-food residual streams in bio-based industries

<p>The agri-food industry generates around 50% of global waste, of which only 36% is recycled, although the potential recovery could be as high as 60%. These residual streams can be used as feedstock for the bio-based industry (BBI), provided that the composition, logistics and volume are carefully analysed. Within the framework of the European Model2Bio project (H2020-BBI-JTI-2019. No 887191), the authors are developing a Decision Support System (DSS) tool for the management of residual streams produced in agrifood companies. This will be an innovative concept that using predictive models will be able to select the best routes for valorising these streams considering their composition, seasonality, and industry location, among other factors. This innovative MODEL2BIO-DSS tool is based on the interconnection of three complementary elements (simulation module, optimisation algorithm and LCA module). </p><p>The main advantage of the tool is the possibility of giving a holistic solution or prioritisation. Although there are many commercial programs for the simulation of industrial processes, these are mainly based on the analysis of specific facilities, and not on broader analyses with various industries, in which logistics plays a key role. Model2Bio will simulate the entire value chain providing recommendations from a holistic perspective (technical, economic, environmental and social), with the prioritisation of the valorisation possibilities through technical-economic criteria and the final decision through holistic criteria. Within the framework of the Model2Bio project, the tool is being tested in 3 European areas (Spain, Greece, Belgium) with the aim of analysing different management systems, with different degrees of development of valorisation technologies. To show the potential of this new concept for waste management, the final work will present the analysis and optimisation of the agri-food residual streams valorisation in La Rioja (Spain) carried out with the Model2Bio-DSS tool. In this analysis, a comparison of the current agri-food residual streams management and the optimised management will be presented, considering economic and holistic aspects. </p&gt

Nitrous oxide decomposition over Al2O3 supported noble metals (Pt, Pd, Ir): Effect of metal loading and feed composition

Δημοσίευση σε επιστημονικό περιοδικόSummarization: The N2O decomposition (de-N2O) performance of Al2O3 supported, low content (0.25, 0.5 and 1.0 wt.%) noble metal (Pt, Pd, Ir) catalysts, is comparatively explored in the present study. The effect of metal content, operation temperature and feed composition on de-N2O performance is investigated. Characterization studies involving BET, XRD, TEM and H2-TPR were also carried out to reveal the impact of metal entity and content on the structural, morphological and redox characteristics of the catalysts. The catalytic results imply that the de-N2O performance is in general increased upon increasing metal loading, a fact being more intense over Ir-based catalysts. Under oxygen deficient conditions, N2O conversions as high as ∼100% and ∼80% are reached at 600 °C over Ir- and Pd-based catalysts, respectively, instead of only ∼30%, achieved over Pt-based catalysts. A moderate degradation in oxygen excess conditions is observed with Ir and Pd catalysts, while Pt-based catalysts are almost fully depressed. The superior de-N2O performance of Ir-, Pd-based catalysts can be mainly interpreted by taking into account the formation of metal oxide phases, not easily susceptible to oxygen poisoning. For Ir-based catalysts the active phase seems to be mainly the metal oxide phase (IrO2), as revealed by H2-TPR, XRD and TEM experiments. In the case of palladium catalysts two different metal phases, i.e. PdO and metallic Pd0 were detected. On the other hand, platinum catalysts presented only metallic Pt0 species, which are prone to poisoning by strongly adsorbed oxygen atoms.Παρουσιάστηκε στο: Journal of Environmental Chemical Engineerin

Effect of alkali promoters (K) on nitrous oxide abatement over Ir/Al2O3 catalysts

Summarization: The promoting impact of potassium (0–1 wt% K) on nitrous oxide (N2O) catalytic decomposition over Ir/Al2O3 is investigated under both oxygen deficient and oxygen excess conditions. All samples were characterized by means of X-ray powder diffraction (XRD), temperature-programmed reduction (H2-TPR), ammonia desorption (NH3-TPD) and Fourier Transform Infrared Spectroscopy of pyridine adsorption (FTIR-Pyridine). The results reveal that the K-free Ir/Al2O3 catalyst consists mainly of the IrO2 phase, exhibiting also significant Lewis acidity, which is gradually eliminated by the addition of K. Catalytic performance results showed that the deN2O performance in the absence of O2 in the feed mixture is negatively affected upon increasing potassium loading. However, under oxygen excess conditions, a pronounced effect of K is observed. Although the catalytic performance of the un-doped catalyst is drastically hindered by the presence of O2, the K-promotion notably prohibits the oxygen poisoning. The optimum deN2O performance under oxygen excess conditions is obtained with potassium loading of 0.5 wt% K, which offers complete conversion of N2O at 580 °C, instead of the corresponding 50 % N2O conversion achieved with the un-modified sample. On the basis of characterization results, it was concluded that alkali-doping in combination with oxygen excess conditions are required towards the formation of active Ir entities.Presented on: Topics in Catalysi

A comparative study of the H2-assisted selective catalytic reduction of nitric oxide by propene over noble metal (Pt, Pd, Ir)/γ-Al2O3 catalysts

Summarization: The impact of H2 as additional reducing agent on the SCR of NO with C3H6 in excess oxygen, was comparatively explored over low noble metal loading (0.5 wt%), Pt/γ-Al2O3, Pd/γ-Al2O3, Ir/γ-Al2O3 catalysts. To gain insight into the role of H2, the reactions NO + C3H6 + O2 (R#1), NO + C3H6 + O2 + H2 (R#2), NO + H2 + O2 (R#3) were employed. In respect to propene oxidation, the Pd > Pt > Ir sequence was obtained under R#1, since they exhibit complete conversion at 220, 250, 325 °C, respectively; all metals exhibit moderate deNOx performances (XNO, <40%). H2 co-presence (R#2) promotes both the NO and C3H6 conversions, which is valid in the whole temperature interval investigated (50-400 °C), being more substantial for Pt/γ-Al2O3 and Ir/γ-Al2O3, less beneficial for Pd/γ-Al2O3. A two-maxima feature is obtained on XNO pattern (at ∼100 and ∼230 °C) of Pt and Pd during R#2. The low temperature maximum-attributed to NO reduction by H2-is substantially more pronounced on Pt than Pd, offering XNO ∼90% and SN2 ∼85%; the high temperature maximum-attributed to NO reduction by C3H6-is higher by ∼15% on both Pt and Pd, in respect to the values obtained during R#1, while SN2 remained unaffected. Different XNO pattern with one maximum is obtained over Ir, implying a synergistic interaction between H2 and C3H6. This synergy is accompanied by a substantial widening of the NO reduction window toward lower temperatures and a considerable increase on both XNO,max and SN2 (from XNO ∼30% with SN2 ∼55% during R#1 to XNO ∼70% with SN2 ∼95% during R#2). The specific features of all reactions and metals employed are comparatively discussed.Presented on: Journal of Environmental Chemical Engineerin

N2O decomposition over ceria-promoted Ir/Al2O3 catalysts: the role of ceria

Περίληψη: The impact of CeO2 in the Al2O3-20wt% CeO2 support prepared by the co-precipitation method on the Ir particle size, morphology and oxidation state, and in turn on the deN2O catalytic activity (1000ppmN2O) of supported Ir catalysts were investigated in the absence and presence of excess O2 (2vol%) conditions. It was demonstrated that the deN2O activity of Ir/Al2O3 is notably suppressed by the presence of oxygen in the feed stream, namely, the N2O conversion at 600°C is declined to 65% in the presence of oxygen as compared to 100% in the absence of oxygen. A similar detrimental catalytic effect was also observed for the Ir/CeO2 solid. On the contrary, the deN2O performance of CeO2-modified Ir/Al2O3 catalyst is only slightly affected by the presence of oxygen. An extensive characterization study involving surface texture analysis (N2 adsorption-desorption at -196°C), temperature-programmed reduction in H2 (H2-TPR), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption and desorption (CO-DRIFTS) was carried out to gain insight into the origin of the CeO2-induced promotional effect. The characterization results revealed the existence of IrO2 phase (H2-TPR, XRD, HRTEM, EELS and CO-DRIFTS) as well as of very small isolated particles of Ir on the Al2O3, CeO2 and CeO2-Al2O3 supports (STEM) but to a notably different extent. The coexistence of large IrO2 particles of perfect crystallite structure and very small Ir particles located at the Ir-ceria interface was revealed only in Ir/AlCe. The establishment of a certain Irδ+/Ιr0 ratio and oxygen vacant sites (VO) concentration in ceria around very small Ir particles under oxidative reaction conditions seem to largely promote N2O adsorption and subsequent decomposition into N2 and O2 over the CeO2-promoted Ir/Al catalyst. In the case of Ir/Al, a different deN2O decomposition mechanism occurs, where the site reactivity of Irδ+/Ιr0 established under oxidizing conditions is reduced significantly.Presented on: Applied Catalysis B: Environmenta