Vehicle emissions abatement: NO oxidation and ammonia SCR

The design and the development of catalytic systems for reducing vehicle emissions is a complex task due to the variety of components in a wide range of gas flow and temperature. A complete system is, therefore, composed of a series of catalysts or catalytic systems, each of which is dealing with a particular aspect of the abatement process. A Diesel Oxidation Catalyst (DOC) is used for CO and hydrocarbon oxidation as well as the conversion of NO to NO2. The NO2 is used by the downstream processes, i.e. Diesel particulate filter (DPF) and NOx reduction catalyst. In the DPF the particulates are removed and the regeneration of the DPF is enhanced by the presence of NO2. One promising technique to remove the nitrogen oxides are urea selective catalytic reduction (SCR). Urea is decomposed to form ammonia, which reacts selectively with NOx over a catalyst. The SCR rate increases with 50% NO2 to NOx ratio, which again shows the importance of the NO oxidation process.In the first study, a model Pt-based DOC was studied for NO oxidation. The effect of aging in various conditions was examined. More specifically, the impact of the aging on the NO oxidation activity and platinum dispersion was investigated. Thermal aging caused a decrease in dispersion and an increase in NO oxidation performance. However, the aging behavior was strongly correlated with the nature of the aging atmosphere. It was found that aging at low temperatures in O2 promotes the activity to a greater extent than after aging in Ar, even though the dispersions are similar for the two samples. Aging in SO2 and O2 led to a rapid dispersion drop to a minimum value and tremendously enhanced the activity. A long-term aging in presence of SO2 at 250\ub0C confirmed the ability of SO2 to increase sintering rate and improved catalyst activity. The results clearly show that NO oxidation activity is controlled both by the dispersion as well as the atmosphere the platinum particles were aged in. The combination of SO2 and O2 during aging resulted in the highest NO oxidation activity. In the second study that was focused on NH3-Selective Catalytic Reduction, intra-catalyst measurements of reaction and NH3 storage were performed using a unique tool: the SpaciMS. The spatial conversion rates at three temperatures (200, 325 and 400\ub0C) were resolved showing a faster reaction at higher temperature. The same trend was observed for the direct oxidation of NO and NH3.The fraction of the catalyst, used to carry out the reaction until full conversion of NH3, was named “SCR zone” and became smaller at higher temperature and a higher reaction rate. During SCR, NH3 could store on the catalyst until complete saturation of the SCR zone. Surface NH3 was able to react with NO in the gas flow according to SCR reaction equation yielding production of N2 and the formation of a small amount of N2O. NH3 storage capacity during SCR (DC) was compared to the total NH3 storage capacity (TC). In the SCR zone, DC followed TC and no significant unused capacity (UC) was observed, indicating that, in the presence of NH3, storage sites are filled even during SCR operation in the SCR zone

Deactivation of Cu/SSZ-13 NH3-SCR catalyst by exposure to CO, H2, and C3H6

Lean nitric oxide (NOx)-trap (LNT) and selective catalytic reduction (SCR) are efficient systems for the abatement of NOx. The combination of LNT and SCR catalysts improves overall NOx removal, but there is a risk that the SCR catalyst will be exposed to high temperatures and rich exhaust during the LNTs sulfur regeneration. Therefore, the effect of exposure to various rich conditions and temperatures on the subsequent SCR activity of a Cu-exchanged chabazite catalyst was studied. CO, H2, C3H6, and the combination of CO + H2 were used to simulate rich conditions. Aging was performed at 800 \ub0C, 700 \ub0C, and, in the case of CO, 600 \ub0C, in a plug-flow reactor. Investigation of the nature of Cu sites was performed with NH3-temperature-programed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) of probe molecules (NH3 and NO). The combination of CO and H2 was especially detrimental to SCR activity and to NH3 oxidation. Rich aging with low reductant concentrations resulted in a significantly larger deactivation compared to lean conditions. Aging in CO at 800 \ub0C caused SCR deactivation but promoted high-temperature NH3 oxidation. Rich conditions greatly enhanced the loss of Br\uf8nsted and Lewis acid sites at 800 \ub0C, indicating dealumination and Cu migration. However, at 700 \ub0C, mainly Br\uf8nsted sites disappeared during aging. DRIFT spectroscopy analysis revealed that CO aging modified the Cu2+/CuOH+ ratio in favor of the monovalent CuOH+ species, as opposed to lean aging. To summarize, we propose that the reason for the increased deactivation observed for mild rich conditions is the transformation of the Cu species from Z2Cu to ZCuOH, possibly in combination with the formation of Cu clusters.\ua0\ua9 2019, MDPI AG. All rights reserved

Lean and rich aging of a Cu/SSZ-13 catalyst for combined lean NO x trap (LNT) and selective catalytic reduction (SCR) concept

\ua9 2019 The Royal Society of Chemistry. In the combined lean NO x trap (LNT) and selective catalytic reduction (SCR) concept, the SCR catalyst can be exposed to rich conditions during deSO x of the LNT. Aging of Cu/SSZ-13 SCR catalysts, deposited on a cordierite monolith, was therefore studied in rich, lean and cycling lean/rich operations at 800 \ub0C (lean condition: 500 ppm NO, 8% O 2 , 10% H 2 O and 10% CO 2 ; rich condition: 500 ppm NO, 1% H 2 , 10% H 2 O and 10% CO 2 ). The structure of the catalyst was investigated by X-ray diffraction (XRD), surface area measurements and scanning transmission electron microscopy (STEM). In general, aging decreased the SCR activity and NH 3 oxidation. However, rich conditions showed a very rapid and intense deactivation, while lean aging led to only a small low-temperature activity decrease. The XRD results showed no sign of structure collapse, but the number of active sites, as titrated by NH 3 temperature-programed desorption (NH 3 -TPD) and in situ DRIFTS, revealed an important loss of acid sites. NH 3 storage was significantly more depleted after rich aging than after lean aging. The Lewis sites, corresponding to exchange Cu 2+ , were preserved to some extent in lean conditions. Lean aging also decreased the enthalpy of NH 3 adsorption from -158 kJ mol -1 to -136 kJ mol -1 . Moreover, a comparison of aging in lean-rich cycling conditions with aging only in rich conditions revealed that adding lean events did not hinder or reverse the deactivation, and it was mainly the time in rich conditions that determined the extent of the deactivation. The STEM images coupled with elemental analysis revealed the formation of large Cu particles during rich aging. Conversely, Cu remained well dispersed after lean aging. These results suggest that the copper migration and agglomeration in large extra-framework particles, accelerated by the action of hydrogen, caused the observed severe deactivation

Comparative Study of SO2 and SO2/SO3 Poisoning and Regeneration of Cu/BEA and Cu/SSZ-13 for NH3 SCR

Two copper-exchanged zeolites, Cu/SSZ-13 and Cu/BEA, were studied as catalysts for the selective reduction of NOx by NH3 (NH3-SCR). Their activities for standard SCR (NOx = NO) and fast SCR (NOx = 50% NO + 50% NO2) were measured before and after sulfur poisoning at 250\ua0\ub0C. The effect of 30\ua0ppm SO2 and a mixture of 24\ua0ppm SO3 + 6\ua0ppm SO2 was evaluated. The repetition of subsequent activity measurements served as regeneration method in SCR conditions. SO2 deactivated Cu/SSZ-13 whereas Cu/BEA was only moderately affected. SO3 led to stronger deactivation of both catalysts than SO2. However, also for this case, the Cu/BEA was significantly less affected than Cu/SSZ-13, even though Cu/BEA contained larger amount of stored sulfur. One possible reason for this could be the large pores of Cu/BEA, where the sulfur species possibly resulted in less sterical hindrance than in the small pore SSZ-13 structure. NH3 temperature-programmed desorption (NH3-TPD) showed no loss of storage sites upon sulfur treatment and subsequent regeneration. Partial activity recovery was observed after a period in SCR conditions at 400\ua0\ub0C and 500\ua0\ub0C. Temperature at 300\ua0\ub0C was insufficient to regenerate the catalysts. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of NO adsorption suggested that SO2 interacts with the ZCuOH sites on Cu/SSZ-13, causing the strong poisoning

Structure and performance of zeolite supported Pd for complete methane oxidation

The influence of zeolite support materials and their impact on CH oxidation activity was studied utilizing Pd supported on H-beta and H-SSZ-13. A correlation between CH oxidation activity, Si/Al ratio (SAR), the type of zeolite framework, reduction-oxidation behaviour, and Pd species present was found by combining catalytic activity measurements with a variety of characterization methods (operando XAS, NH -TPD, SAXS, STEM and NaCl titration). Operando XAS analysis indicated that catalysts with high CH oxidation activity experienced rapid transitions between metallic- and oxidized-Pd states when switching between rich and lean conditions. This behaviour was exhibited by catalysts with dispersed Pd particles. By contrast, the formation of ion-exchanged Pd and large Pd particles appeared to have a detrimental effect on the oxidation-reduction behaviour and the conversion of CH . The formation of ion-exchanged Pd and large Pd particles was limited by using a highly siliceous beta zeolite support with a low capacity for cation exchange. The same effect was also found using a small-pore SSZ-13 zeolite due to the lower mobility of Pd species. It was found that the zeolite support material should be carefully selected so that the well-dispersed Pd particles remain, and the formation of ion-exchanged Pd is minimized. 4 4 3 4 4 2+ 2+ 2

Kinetic modeling of NH3-SCR over a supported Cu zeolite catalyst using axial species distribution measurements

In this study, a kinetic model is developed for NH3-SCR over a honeycomb-monolith-supported Cu-zeolites using intra-catalyst axial species distribution measurements. An ammonia TPD experiment, together with micro calorimetry data were used for tuning the ammonia adsorption and desorption properties. The spatial distribution for NO oxidation, NH3 oxidation and NH3 "Standard" SCR were modeled between 200 and 400 degrees C. Four-step protocol measurements were employed in order to validate the transient functions of the model. The resulting kinetic model provides good spatiotemporal simulation of the SCR reaction and component reactions throughout the monolith catalyst system

Impact Assessment of Disruptive Technologies on Electronic Identities (eID) for the Improvement of Digital Public Services for Citizens

Public services are increasingly being transformed into smart public services, also known as digital public services or eGovernment. In several cases, access to specific services is personal and non-transferable, thus requiring secure and trustful identification as well as management of the so called “digital identities”. In this context, it is obvious that citizens and public services in particular would benefit greatly from digital identity management technology, as new and emerging technologies have strong potential to empower existing eID systems. Yet, while opportunities enabled by these technologies are undeniable, challenges also exist, including technological and social implications, as well as barriers, risks and limitations. In addition, the establishment of standards for these ecosystems and compliance with framework conditions, including national and European regulations are essential points that must be considered. Based on these observations, the IMPULSE (Identity Management in PUblic SErvices) project, funded under the Horizon 2020 programme, was launched in early 2020. IMPULSE aims to perform a multidisciplinary evaluation of the disruptive transformation of electronic identity (eID) management in public services enabled by Distributed Ledger Technology (DLT) and Artificial Inteligence (AI). Overall, this paper will present the research pathway set up to answer the question of how a single adaptive eID solution can be useful to the whole city ecosystem, from the micro-citizen level to the macro-governmental perspective, by focusing on the main achievements of the IMPULSE project so far

Vehicle emissions abatement: NO oxidation and ammonia SCR

The design and the development of catalytic systems for reducing vehicle emissions is a complex task due to the variety of components in a wide range of gas flow and temperature. A complete system is, therefore, composed of a series of catalysts or catalytic systems, each of which is dealing with a particular aspect of the abatement process. A Diesel Oxidation Catalyst (DOC) is used for CO and hydrocarbon oxidation as well as the conversion of NO to NO2. The NO2 is used by the downstream processes, i.e. Diesel particulate filter (DPF) and NOx reduction catalyst. In the DPF the particulates are removed and the regeneration of the DPF is enhanced by the presence of NO2. One promising technique to remove the nitrogen oxides are urea selective catalytic reduction (SCR). Urea is decomposed to form ammonia, which reacts selectively with NOx over a catalyst. The SCR rate increases with 50% NO2 to NOx ratio, which again shows the importance of the NO oxidation process. In the first study, a model Pt-based DOC was studied for NO oxidation. The effect of aging in various conditions was examined. More specifically, the impact of the aging on the NO oxidation activity and platinum dispersion was investigated. Thermal aging caused a decrease in dispersion and an increase in NO oxidation performance. However, the aging behavior was strongly correlated with the nature of the aging atmosphere. It was found that aging at low temperatures in O2 promotes the activity to a greater extent than after aging in Ar, even though the dispersions are similar for the two samples. Aging in SO2 and O2 led to a rapid dispersion drop to a minimum value and tremendously enhanced the activity. A long-term aging in presence of SO2 at 250°C confirmed the ability of SO2 to increase sintering rate and improved catalyst activity. The results clearly show that NO oxidation activity is controlled both by the dispersion as well as the atmosphere the platinum particles were aged in. The combination of SO2 and O2 during aging resulted in the highest NO oxidation activity. In the second study that was focused on NH3-Selective Catalytic Reduction, intra-catalyst measurements of reaction and NH3 storage were performed using a unique tool: the SpaciMS. The spatial conversion rates at three temperatures (200, 325 and 400°C) were resolved showing a faster reaction at higher temperature. The same trend was observed for the direct oxidation of NO and NH3.The fraction of the catalyst, used to carry out the reaction until full conversion of NH3, was named “SCR zone” and became smaller at higher temperature and a higher reaction rate. During SCR, NH3 could store on the catalyst until complete saturation of the SCR zone. Surface NH3 was able to react with NO in the gas flow according to SCR reaction equation yielding production of N2 and the formation of a small amount of N2O. NH3 storage capacity during SCR (DC) was compared to the total NH3 storage capacity (TC). In the SCR zone, DC followed TC and no significant unused capacity (UC) was observed, indicating that, in the presence of NH3, storage sites are filled even during SCR operation in the SCR zone

Fundamental studies of catalytic systems for diesel emission control

Due to global lean exhaust gas and new emission regulations, exhaust aftertreatment systems of diesel engines are more and more sophisticated and composed of a series of catalytic units. In the present work, two of these catalytic systems were studied with different approach. A model diesel oxidation catalyst (DOC), used to convert nitric oxide into nitrogen dioxide and hydrocarbons and CO into CO2, was examined in flow reactor experiments. A Cu-exchanged zeolite catalyst, devoted to the lean NOx reduction by ammonia was studied with SpaciMS in operating conditions. Since longevity and resistance to poisoning are two major challenges for automotive catalysts, the effect of thermal aging in reactive atmosphere on NO oxidation activity was addressed and correlated to platinum dispersion. Our experiments revealed the promotion of Pt sintering by SO2 as well as the improvement of oxidation ability. Sintering in argon to obtain similar Pt dispersion did not result in similar performance indicating the important role of aging atmosphere in subsequent activity. The DOC was subjected to SO2 treatment in order to characterize the sulfur species formed during SO2 poisoning and their impact on the oxidation of NO and C3H6. Two types of sulfur species that differ in stored amount and impact on the activity were distinguished by TPR experiment. However, both have a detrimental effect on the DOC performance. Finally, modification of the DOC formulation by incorporation of acidity enhancer groups was carried out. The introduction of chlorine and sulfate to increase the acidic nature of the support yielded suppression of catalyst deactivation due to platinum oxide formation. However, this effect disappeared after aging and subsequent TPR to 800\ub0C, suggesting a loss of these acidity-promoters. The study of the NOx reduction catalyst was performed to evaluate its activity, NH3 storage capacity and NH3 and NO oxidation ability. Intra-catalyst measurements were achieved with SpaciMS at Oak Ridge National Laboratory. This technique provides insight of the reaction evolution throughout the monolithic catalyst and showed the diminishing of the zone used for SCR reaction as the temperature increased from 200 to 400\ub0C. The intra-catalyst concentration profiles are valuable data, acquired in realistic flow and temperature conditions and was utilized to develop a kinetic model for standard NH3-SCR. The model accounts for the N2O production according to two routes and predicts well the transient phenomena resulting from changes in gas composition