NOx Storage-reduction Catalysts Research Articles

Ordered Nanostructure Catalysts Efficient for NOx Storage/Reduction (NSR) Processes

NOx emissions in the atmosphere can cause various environmental problems, which should be strictly controlled and regulated. Furthermore, because of the limited amount of crude oil resources in the world and severe global warming, the development of fuel-efficient vehicles has long been desired. Accordingly, efficient NOx storage and reduction catalysts have been developed over the decades, called NSR (NOx storage/reduction) catalysts. In the present article, recent advances in NSR catalysts which possess ordered nanostructures will be summarized, including our noble Pt/KNO3/K-titanate nanobelt (KTN), Pt-KNO3/CeO2 and Pt-KNO3/ZrO2 catalysts, as well as nanoporous Ni-phosphate (VSB-5) and Co-substituted VSB-5 catalysts.

Rh/CeO2+Pt/Ba/Mn/Al2O3 model NSR catalysts: Effect of Rh/Pt weight ratio

A series of model NOx storage-reduction (NSR) catalysts with different Rh/Pt weight ratios were prepared independently by wet impregnation and then mechanically mixed to investigate the effect of the Rh/Pt weight ratio on the overall NOx removal efficiency and nitrogen yield. XRD, EDS and H2-TPR studies indicated the coexistence of BaCO3, MnOx and BaMnO3 phases in the catalysts. Increasing Rh/Pt weight ratio enhanced NOx reduction under the rich phase, and improved overall N2-yield in the kinetic regime of NO conversion, but shows a negative effect in the equilibrium-limited regime above 400 °C.

High Performance of Mn-Doped MgAlOx Mixed Oxides for Low Temperature NOx Storage and Release

NOx storage-reduction (NSR) is a potential approach for the effective removal of NOx under the lean conditions in lean-burn engines. Herein, manganese-doped mixed oxides (Mn/MgAlOx) with high performance for low temperature NOx storage and release were derived from hydrotalcites precursors prepared by a facile coprecipitation method. The catalysts were characterized by X-ray diffraction (XRD), SEM, N2 adsorption-desorption, H2-TPR, FT-IR, and X-ray photoelectron spectroscopy (XPS) techniques. The Mn-doped MgAlOx catalysts exhibited high NOx storage capacity (NSC) at low temperature range (150–300 °C), which was related to their increased surface area, improved reducibility and higher surface Mn3+ content. The largest NSC measured, 426 μmol/g, was observed for NOx adsorption at 200 °C on Mn15 catalyst (the sample containing 15 wt% of Mn). The in situ DRIFTS spectra of NOx adsorption proved that the Mn-doped hydrotalcite catalysts are preferred for low temperature NOx storage and release due to their ability to store NOx mainly in the form of thermally labile nitrites. NSR cycling tests revealed the NOx removal rate of Mn15 sample can reach above 70% within the wide temperature range of 150–250 °C. Besides, the influence of CO2, soot, H2O and SO2 on NOx storage performance of Mn15 catalyst was also studied. In all, owning to their excellent NOx storage capacity, NSR cycling performance, and resistance to CO2, soot, SO2 and H2O, the Mn-doped MgAlOx NSR catalysts have broad application prospects in NOx control at low temperatures.

Al2O3-supported Pt/Rh catalysts for NOx removal under lean conditions

In this work the reactivity of Pt-Rh NOx storage-reduction (NSR) catalysts in the reduction of NOx under lean conditions is investigated. It is found that significant amounts of NOx are stored on both Rh- and Pt-based samples at all the investigated temperatures (in the range 150–350 °C). Mostly chelating nitrites are adsorbed at the lowest investigated temperature (150 °C), while nitrates (both bidentate and ionic) at higher temperatures. However, at all temperatures nitrites prevail at the beginning of the storage phase, while nitrates represent the most abundant adsorbed species after prolonged contact. Pt-containing catalysts (either monometallic Pt or bimetallic Pt/Rh) show higher NOx storage capacity than the Rh monometallic sample, possibly due to the higher dispersion of Pt vs. Rh and/or to the higher oxidizing capability of Pt vs. Rh.The stored NOx species show relevant thermal stability, and decompose to NOx and O2 upon heating. In particular, nitrites disproportionate to gaseous NO and nitrates; these latter then decompose to NOx and O2. On the Rh-Ba/Al2O3 catalyst the disproportionation reaction is observed with a higher temperature onset if compared to the Pt-based samples. The analysis of the reactivity of the stored NOx species (probed by isotopic labeling experiments and reduction with H2 and NH3) showed the lower reactivity of the Rh-Ba/Al2O3 sample; however Rh shows activity in the ammonia decomposition reaction to N2 and H2, unlike Pt. The lower reactivity of the Rh-Ba/Al2O3 sample is also pointed out by experiments under cyclic lean-rich conditions. However, the presence of Rh increases the reactivity of the catalyst in the steam reforming of hydrocarbons, especially at high temperature, and accordingly the reactivity of the bimetallic Pt/Rh sample at high temperatures is higher than that of the Pt and Rh monometallic catalysts.

Mechanistic Aspect of N2O Formation Over Pt\u2013Ba/\u03b3-Al2O3 Catalysts

NOX reduction in lean-burn gasoline or diesel engines is challenging in the oxidizing environment, and depending on the after-treatment technology, can lead to by-product, such as N2O or ammonia, formation. The current study focuses on possible N2O formation pathways over NOx storage/reduction (NSR) catalysts. More specifically, NH3 reactivity with catalyst surface species was investigated over a model Pt–Ba/γ-Al2O3 (1/20/100, w/w) NSR catalyst with and without NOx species stored (nitrites and nitrates). The NH3 originates from reduction of NOx in the regeneration phase. With NH3, two overall reactions can lead to N2 or N2O formation, namely 3NO + 2NH3 → 5/2 N2 + 3H2O and 4NO + NH3 → 5/2 N2O + 3/2H2O. These two are considered for catalyzed reaction between the entering NO and NH3. Surface nitrite and nitrate reduction reactions leading to N2 or N2O were also evaluated, all as a function of temperature and relative amount of NH3 in the gas phase. N2O was formed in the lower temperature range, and was more significant with lower NH3 concentrations. At higher temperatures, above 423 K, for NH3 concentrations higher than stoichiometric, only N2 was produced. In comparing the results from the samples with preformed nitrites/nitrates on the surface to those without, it is apparent that NH3 first reacts with gas-phase NO and then with pre-stored surface NOx species. Moreover, the reduction of surface nitrites/nitrates is complete only for high NH3/NO ratios, and when NH3 is the limiting reactant, they remain on the catalyst surface unreacted until temperatures higher than 623 K, where they decompose. In general, for all performed experiments, N2O was the dominant product at low temperature, when NO and NH3 conversions are low. At higher temperature, with increasing NO and NH3 conversions, N2 selectivity increases.

New insights on the adsorption, thermal decomposition and reduction of NOx over Pt- and Ba-based catalysts

In this study mechanistic aspects related to the adsorption of NOx over alumina-supported Pt, Ba and PtBa catalysts are deepened, that are of interest for NOx Storage-Reduction (NSR) catalysts and other applications involving the adsorption of NOx (e.g. Passive NOx Adsorbers, PNAs). NOx adsorption is investigated at low and high temperatures (150°C and 350°C, respectively); the thermal decomposition and the reactivity with H2 of the adsorbed species is also addressed. By coupling FT-IR spectroscopy and microreactor studies, new insights on the adsorption, decomposition and reactivity of the stored NOx are derived. In particular it is found that at 150°C nitrites are formed on all surfaces when starting from NO/O2; different species are formed onto the different storage sites (Ba vs. Al) that can be distinguished spectroscopically. Different routes for the storage of nitrites are highlighted, i.e. direct oxidative NO uptake and nitrite formation involving NO2 produced by oxidation of NO. Clear and novel evidence is herein provided that the direct NO oxidative uptake is much faster than the route involving the NO to NO2 oxidation. Both routes are catalyzed by Pt, although Ba is also able to store nitrites; the role of the interaction between Pt and the storage sites is discussed. When the NOx storage is carried out at higher temperatures (350°C), both routes are greatly favored although nitrites can hardly be observed being readily transformed into nitrates. Besides NO2 is also formed in significant amounts that may participate to the formation of nitrites/nitrates adspecies following a NO2 disproportion pathway for which clear and new spectroscopic evidences are herein provided.The adsorbed species (nitrites or nitrates) start to decompose above the adsorption temperature, i.e. 150°C and 350°C, respectively. In the presence of Pt, the decomposition of the stored nitrites leads to the formation of nitrates and NO due to the occurrence of a nitrite disproportion reaction. The formed nitrates show high thermal stability and decompose only at high temperatures, thus making these systems unappropriated for PNA applications. In the presence of a reductant, Pt catalyzes the reduction of the stored NOx at much lower temperatures than the adsorption; the role of the interaction between Pt and the storage sites on this step is herein discussed.

Design of highly efficient NOx storage-reduction catalysts from layered double hydroxides for NOx emission control from naphtha cracker flue gases

Although there are many reports on the removal of NOx from vehicle and power plant emissions, little effort has been devoted to the removal of NOx from cracker flue gases. Here we report a systematic investigation on the design of highly efficient NOx storage-reduction (NSR) catalysts using highly dispersed aqueous miscible organic-layered double hydroxides (AMO-LDHs) derived mixed oxides (LDOs) for NOx emission control from naphtha cracker flue gases. For a series of binary M2+Al3+ LDOs, the influence of six divalent cations (Ca, Zn, Cu, Ni, Co, and Mg) on the NOx adsorption capacity, NO oxidation property, and the thermal stability of adsorbed NOx was systematically investigated. The optimal NOx storage temperature range for each binary LDO was also determined. Based on the fundamental findings of binary LDOs, a ternary LDH CoMgAl-CO3 derived LDO CoMgAlOx with a significantly improved NOx storage capacity was designed. By tuning the Co/Mg ratio, the NOx storage capacity was greatly improved from 0.14mmol/g for Mg3Al1Ox to 0.50mmol/g for Co1Mg2Al1Ox at 300°C. By further doping Pt and K2CO3, a new NSR catalyst composed of 1wt% Pt/15wt% K2CO3/Co1Mg2Al1Ox was obtained, which exhibited a very high NOx storage capacity of 1.2mmol/g. Finally, the NSR cycling performance, and the CO2, SO2 and H2O resistance of this catalyst were also investigated. Thanks for its superior NOx storage capacity, NSR cycling performance, and CO2, SO2 and H2O resistance, this new NSR catalyst showed great potential for the NOx control from cracker flue gases.

Development of a NOx Storage-Reduction Catalyst Based Min-NOx Strategy for Small-Scale NG-Fueled Gas Engines

Development of a NO_x Storage-Reduction Catalyst Based Min-NO_x Strategy for Small-Scale NG-Fueled Gas Engines

Clarification of NH3 Formation Mechanism on a Diesel Engine NOx Storage Reduction Catalyst Under Rich Conditions and Evaluation of the SCR Benefit at WLTC

Recent studies have shown that the combination of a NOx storage reduction catalyst (NSR) and a passive selective catalytic reduction catalyst (pSCR) would be a technical solution to meet post EU6 emission legislation for small passenger cars. In this case, NH3 formed during rich NSR regeneration is used to reduce remaining NOx on a SCR catalyst which is located downstream of the NSR. In this study, first, the NH3 formation mechanism of NSR under different emission λs, rich durations, and stored NOx values are clarified using a diesel engine operating under steady-state operation. Finally, NOx conversion and the associated fuel consumption penalty are clarified under the Worldwide harmonized light vehicle test cycle (WLTC). It was identified that NH3 starts to be produced by the NSR after oxygen storage capacity depletion. Next, a NH3 peak occurs as a result of the converted pre-stored and engine out NOx. If the rich operation is long enough, the pre-stored NOx contribution fades and NH3 concentration lowers to an equivalent level as the engine out NOx. From this understanding, several WLTC patterns were measured varying the number of rich operations and their duration in order to identify best regeneration strategy with a minimum fuel consumption penalty. The optimal pSCR benefit, in terms of fuel penalty, is achieved when the rich operation duration is (1) longer than the breakthrough time, (2) includes the initial NH3 peak resulting from the conversion of the pre-stored NOx.

Sulfation and Desulfation Behavior of Pt-BaO/MgO-Al2O3 NOx Storage Reduction Catalyst.

The comparative study between Pt-BaO/Al2O3 and Pt-BaO/MgO-Al2O3 gives the information about the effect of MgO addition to Al2O3 support on the sulfation and desulfation behavior of Pt-BaO/MgO-Al2O3 NOx storage reduction catalyst. The sulfated two samples were analyzed by using element analysis (EA), X-ray diffraction (XRD), H2 temperature programmed reaction (H2 TPRX) and NOx uptake measurement. The amount of sulfur uptake on 2 wt% Pt-20 wt% BaO/Al2O3 and 2 wt% Pt-20 wt% BaO/MgO-Al2O3 are almost identical as 0.45 and 0.40 of S/Ba, respectively, which yields the drastic decrease in NOx uptake for both sulfated samples. However, after desulfa- tion with H2 at 600 degrees C, the residual sulfur amount on MgO-Al2O3 supported catalyst is three times larger than that on Al2O3 supported one, indicating that sulfur species formed on the former are more stable than those on the latter. It is also well corresponding to the H2 TPRX results where the main H2S peak from MgO-Al2O3 supported sample is observed at higher temperature than Al2O3 supported one, resulting in the lower NOx uptake activity of former sample than the latter one. Meanwhile, after desulfation of MgO-Al2O3 supported sample at 700 degrees C and 800 degrees C, the activity is recovered more significantly due to the removal of the large amount of sulfur while Al2O3 supported one decreases monotonically due to the sintering of Pt crystallite and the formation of BaAl2O4 phase. It is summarized that MgO-Al2O3 supported catalyst enhances the thermal stability of the catalyst, however, forms the stable sulfate species, which needs to be improved to develop the more sulfur resistant NSR catalyst system.

Study of N2O Formation over Rh- and Pt-Based LNT Catalysts

In this paper, mechanistic aspects involved in the formation of N2O over Pt-BaO/Al2O3 and Rh-BaO/Al2O3 model NOx Storage-Reduction (NSR) catalysts are discussed. The reactivity of both gas-phase NO and stored nitrates was investigated by using H2 and NH3 as reductants. It was found that N2O formation involves the presence of gas-phase NO, since no N2O is observed upon the reduction of nitrates stored over both Pt- and Rh-BaO/Al2O3 catalyst samples. In particular, N2O formation involves the coupling of undissociated NO molecules with N-adspecies formed upon NO dissociation onto reduced Platinum-Group-Metal (PGM) sites. Accordingly, N2O formation is observed at low temperatures, when PGM sites start to be reduced, and disappears at high temperatures where PGM sites are fully reduced and complete NO dissociation takes place. Besides, N2O formation is observed at lower temperatures with H2 than with NH3 in view of the higher reactivity of hydrogen in the reduction of the PGM sites and onto Pt-containing catalyst due to the higher reducibility of Pt vs. Rh.

Impact of soot‐NSR catalyst contact depending on reactive gas composition on NOx storage

Interaction between a model soot (carbon black) and a model NOx storage reduction catalyst (Pt‐Ba/Al2O3) is investigated as a function of the strength of the carbon–catalyst contact and the presence or not of H2O in the reactive gas flow. Experiments performed at laboratory scale, using a fixed bed reactor, revealed that the inhibiting effect of carbon on the NOx storage capacity (NSC) of the catalyst increases with the strength of carbon–catalyst contact and affects NOx adsorption on both Al sites and Ba sites, whereas the oxidative function of the catalyst (Pt sites) is not affected. In the presence of water in the reactive gas flow, it was observed that carbon prevents the inhibition of the oxidative function of the catalyst by H2O. On the other hand, the inhibiting effect of carbon on NSC decreases. Hence, a noncumulative effect of carbon and H2O impacts on NSC is observed. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 14–19, 2016

Model sulfur-resistant NSR catalysts: An XPS study of the interaction of BaO/TiO2-ZrO2 and Pt-BaO/TiO2-ZrO2 with NO2

The interaction of NO2 with BaO/TiO2-ZrO2 and Pt-BaO/TiO2-ZrO2 model NO x storage-reduction (NSR) catalysts prepared on the surface of FeCrAl alloy substrates has been investigated by X-ray photoelectron spectroscopy. The action of nitrogen dioxide on these catalysts at room temperature causes the consecutive formation of surface barium nitrite and nitrate. Supposedly, NO2 reduction yielding barium nitrite at the early stages of the interaction is due to the oxidation of amorphous carbon impurities. The introduction of platinum into the catalyst accelerates nitrogen dioxide sorption. On being exposed to NO2 for a long time, platinum oxidizes to PtO2. This process is more pronounced in the sample containing freshly deposited platinum. Heat treatment of this sample in a vacuum, which coarsens the platinum particles, makes them more resistant to oxidation.

Composition dependent performance of alumina-based oxide supported WO3 catalysts for the NH3-SCR reaction and the NSR + SCR coupled process

Among the specific technologies to reduce NOx from automobile lean exhaust gases, the NOx storage reduction (NSR) and the selective catalytic reduction (SCR) by urea/NH3 are the two main effective proposed processes. During the short rich excursions of the NSR process, emissions of undesired NH3 can occur and the combination of the NSR and a NH3-SCR catalyst has been proposed to improve the global treatment efficiency. With the aim to develop non zeolite SCR catalysts, materials based on modified alumina were prepared by sol–gel method. Necessary acidic and redox properties were expected by incorporation of metal ions such as cerium (for oxygen mobility), zirconium, titanium, and silica (acidic behavior). The influence of each element incorporated in the host alumina and their combination were evaluated in NH3-SCR before and after 9wt% WO3 impregnation. Among the 15 synthetized supports, three WO3 supported catalysts exhibited promising SCR activities were selected (WO3/Al0.2Ce0.4Ti0.4, WO3/Al0.2Ce0.16Zr0.32Ti0.32 and WO3/Al0.1Si0.1Ce0.16Zr0.32Ti0.32) and characterized (N2 adsorption, XRD analysis, NH3-SCO reactivity, NH3 storage capacity, pyridine adsorption monitored by IR spectroscopy, H2-TPR, OSC) and then associated downstream to a model Pt/Ba/Al2O3 NSR catalyst. The use of ammonia emitted from the NSR catalyst during the rich pulses was studied taking into accounts three possibilities: the NH3-SCR reaction (NH3+NOx→N2), the NH3-SCO reaction (NH3+O2→N2) and the unconverted NH3. Only the NH3-SCR reaction occurs at 200°C; whereas the three pathways take place at 300 and 400°C. In addition, a lack of strong acidic storage sites results in unconverted ammonia at high temperature.

Enhanced NOx conversion by coupling NOx storage-reduction with CO adsorption-oxidation over the combined Pd−K/MgAlO and Pd/MgAlO catalysts

NOx conversion was enhanced by coupling NOx storage-reduction (NSR) with CO adsorption-oxidation (CAO), which was observed in NSR lean-rich cycle tests with CO as a reductant on catalysts of Mg-Al mixed oxides supported Pd (Pd/MgAlO) and Pd–K (Pd–K/MgAlO). CO was adsorbed on Pd sites in the rich condition and then oxidized by gaseous NOx via Eley–Rideal mechanism during the transition from the rich condition to the lean condition, which results in an enhanced NOx conversion. This is confirmed by different configuration experiments of Pd–K/MgAlO and Pd/MgAlO, acting as NSR and CAO catalysts, respectively. The intimate mixture of Pd–K/MgAlO and Pd/MgAlO showed much higher activity due to the resultant coupling effect of NSR with CAO in comparison with a zone-arranged catalyst system no matter whether Pd–K/MgAlO or Pd/MgAlO was in the front. The coupling also worked in the presence of H2O and CO2 despite that the efficiency were spoiled. This strategy is ease to be implemented and thereby is potential for the practical after-treatment technology for lean-burn and diesel engines.

Pt/CexPr1−xO2 (x = 1 or 0.9) NOx storage–reduction (NSR) catalysts

Model Pt/Ce0.9Pr0.1O2 and Pt/CeO2 NOx storage–reduction catalysts were prepared via nitrate calcination, co-precipitation and carbon-templating routes. Raman spectroscopic data obtained on the catalysts indicated that the introduction of praseodymium into the ceria lattice increased the concentration of defect sites (vacancies), arising from the higher reducibility of the Pr4+ cation compared to Ce4+. For the Pr-promoted samples, H2-TPR profiles contained high temperature bulk reduction peaks which were less pronounced compared with their ceria analogs, indicating that the presence of praseodymium enhances oxygen mobility due to the creation of lattice defects. Under lean-rich cycling conditions, the cycle-averaged NOx conversion of the Pt/Ce0.9Pr0.1O2 samples was in each case substantially higher than that of the Pt/CeO2 analog, amounting to a difference of 10–15% in the absolute NOx conversion in some cases. According to DRIFTS data, a double role can be assigned to Pr doping; on the one hand, Pr accelerates the oxidation of adsorbed NOx species during the lean periods. On the other hand, Pr doping destabilizes the adsorbed NOx species during the rich periods, and the kinetics of nitrate decomposition are faster on Pt/Ce0.9Pr0.1O2, leading to improved catalyst regeneration. These results suggest that ceria-based mixed oxides incorporating Pr are promising materials for NOx storage–reduction catalysts intended for low temperature operation.

Origin of double dinitrogen release feature during fast switching between lean and rich cycles for NOx storage reduction catalysts

The performance of NOx storage and reduction over 1.5wt% Pt/20wt% KNO3/K2Ti8O17 and 1.5wt% Pt/K2Ti8O17 catalysts has been investigated using combined fast transient kinetic switching and isotopically labelled 15NO at 350°C. The evolution of product N2 has revealed two significant peaks during 60s lean/1.3s rich switches. It also found that the presence of CO2 in the feed affects the release of N2 in the second peak. Regardless of the presence/absence of water in the feed, only one peak of N2 was observed in the absence of CO2. Gas-phase NH3 was not observed in any of the experiments. However, in the presence of CO2 the results obtained from in situ DRIFTS-MS analysis showed that isocyanate species are formed and stored during the rich cycles, probably from the reaction between NOx and CO, in which CO was formed via the reverse water–gas shift reaction.

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

Automotive Three-Way Catalysts (TWC) were introduced more than 40 years ago. Despite that, the development of a sustainable TWC still remains a critical research topic owing to the increasingly stringent emission regulations together with the price and scarcity of precious metals. Among other material classes, perovskite-type oxides are known to be valuable alternatives to conventionally used TWC compositions and have demonstrated to be suitable for a wide range of automotive applications, ranging from TWC to Diesel Oxidation Catalysts (DOC), from NOx Storage Reduction catalysts (NSR) to soot combustion catalysts. The interest in these catalysts has been revitalized in the past ten years by the introduction of the concept of catalyst regenerability of perovskite-based TWC, which is in principle well applicable to other catalytic processes as well, and by the possibility to reduce the amounts of critical elements, such as precious metals without seriously lowering the catalytic performance. The aim of this review is to show that perovskite-type oxides have the potential to fulfil the requirements (high activity, stability, and possibility to be included into structured catalysts) for implementation in TWC.

Electrochemically-assisted NOx storage–reduction catalysts

Supported noble-metal catalysts are extensively used in industry, particularly for car exhaust treatments. The challenge is to maximize the catalytic efficiency while minimizing the noble metal loading. Recent advances from the literature propose the use of electropromoted nanodispersed catalysts in order to assist catalytic reactions with electrochemical mechanisms: this type of catalyst design, inspired from fuel cells, combines electrochemical promotion of catalysis and high metallic active site availability. This paper explores whether electrochemical effects can improve the catalytic performances of nanodispersed NOx storage and reduction (NSR) catalysts deposited in the porosity of SiC mini-DPFs. NSR catalysts were elaborated employing Pt and Rh nanoparticles as electrodes, supported on yttria stabilized zirconia (YSZ) or gadolinium doped cerium oxide (GDC) nanoparticles (electrolyte), and used for NOx abatement in diesel exhaust gas conditions. Improved NOx removal efficiency was obtained. Comparison of YSZ (ionic conductor) and GDC (mixed ionic and electronic conductor) electrolytes showed that GDC-based catalytic nano-cells present the highest catalytic activities. A detailed analysis of the reaction products showed that electrochemical reactions can take place on nano-electrodes, in addition to catalytic reactions.

Sulfation and lean/rich desulfation of a NOx storage reduction catalyst: Experimental and simulation study

A detailed study of the sulfation and desulfation phenomena of a NOx storage reduction catalyst using synthetic gas bench is presented. The experimental observations and results were put together, in order to develop a model, which can simulate the NOx storage reduction catalyst behavior during the sulfation and desulfation conditions. The target is to use the model for simulation of the lean/rich desulfation strategies, in order to comprehend the complicated phenomena and ultimately predict the sulfur speciation at the outlet of the NOx storage reduction catalyst. Sulfation tests in the presence and in the absence of O2 at different temperatures were conducted, in order to identify the different sulfation sites. Desulfation tests with constantly rich conditions and lean/rich oscillation, using H2 as the reducing gas, were performed in order to investigate the reaction pathways of the decomposition of the sulfates. Additionally, some preliminary investigation was performed using CO and decane in the reducing gas mixture, in order to evaluate the NOx storage reduction behavior under more realistic gas composition for diesel exhaust gas. The important role of the accurate prediction of sulfur axial distribution at the desulfation onset was identified. It was found that cerium oxides play a critical role in the sulfation process by increasing the sulfur capacity of the NOx storage reduction catalyst. Finally, it was clarified that the oxygen stored on cerium oxides strongly affects the selectivity of the desulfation products by oxidizing H2S and controlling H2 availability.