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- Feigin, Valery L., et al.
(author)
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Global, regional, and national burden of stroke and its risk factors, 1990-2019 : a systematic analysis for the Global Burden of Disease Study 2019
- 2021
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In: Lancet Neurology. - : Elsevier. - 1474-4422 .- 1474-4465. ; 20:10, s. 795-820
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Journal article (peer-reviewed)abstract
- Background Regularly updated data on stroke and its pathological types, including data on their incidence, prevalence, mortality, disability, risk factors, and epidemiological trends, are important for evidence-based stroke care planning and resource allocation. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) aims to provide a standardised and comprehensive measurement of these metrics at global, regional, and national levels. Methods We applied GBD 2019 analytical tools to calculate stroke incidence, prevalence, mortality, disability-adjusted life-years (DALYs), and the population attributable fraction (PAF) of DALYs (with corresponding 95% uncertainty intervals [UIs]) associated with 19 risk factors, for 204 countries and territories from 1990 to 2019. These estimates were provided for ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage, and all strokes combined, and stratified by sex, age group, and World Bank country income level. Findings In 2019, there were 12.2 million (95% UI 11.0-13.6) incident cases of stroke, 101 million (93.2-111) prevalent cases of stroke, 143 million (133-153) DALYs due to stroke, and 6.55 million (6.00-7.02) deaths from stroke. Globally, stroke remained the second-leading cause of death (11.6% [10.8-12.2] of total deaths) and the third-leading cause of death and disability combined (5.7% [5.1-6.2] of total DALYs) in 2019. From 1990 to 2019, the absolute number of incident strokes increased by 70.0% (67.0-73.0), prevalent strokes increased by 85.0% (83.0-88.0), deaths from stroke increased by 43.0% (31.0-55.0), and DALYs due to stroke increased by 32.0% (22.0-42.0). During the same period, age-standardised rates of stroke incidence decreased by 17.0% (15.0-18.0), mortality decreased by 36.0% (31.0-42.0), prevalence decreased by 6.0% (5.0-7.0), and DALYs decreased by 36.0% (31.0-42.0). However, among people younger than 70 years, prevalence rates increased by 22.0% (21.0-24.0) and incidence rates increased by 15.0% (12.0-18.0). In 2019, the age-standardised stroke-related mortality rate was 3.6 (3.5-3.8) times higher in the World Bank low-income group than in the World Bank high-income group, and the age-standardised stroke-related DALY rate was 3.7 (3.5-3.9) times higher in the low-income group than the high-income group. Ischaemic stroke constituted 62.4% of all incident strokes in 2019 (7.63 million [6.57-8.96]), while intracerebral haemorrhage constituted 27.9% (3.41 million [2.97-3.91]) and subarachnoid haemorrhage constituted 9.7% (1.18 million [1.01-1.39]). In 2019, the five leading risk factors for stroke were high systolic blood pressure (contributing to 79.6 million [67.7-90.8] DALYs or 55.5% [48.2-62.0] of total stroke DALYs), high body-mass index (34.9 million [22.3-48.6] DALYs or 24.3% [15.7-33.2]), high fasting plasma glucose (28.9 million [19.8-41.5] DALYs or 20.2% [13.8-29.1]), ambient particulate matter pollution (28.7 million [23.4-33.4] DALYs or 20.1% [16.6-23.0]), and smoking (25.3 million [22.6-28.2] DALYs or 17.6% [16.4-19.0]). Interpretation The annual number of strokes and deaths due to stroke increased substantially from 1990 to 2019, despite substantial reductions in age-standardised rates, particularly among people older than 70 years. The highest age-standardised stroke-related mortality and DALY rates were in the World Bank low-income group. The fastest-growing risk factor for stroke between 1990 and 2019 was high body-mass index. Without urgent implementation of effective primary prevention strategies, the stroke burden will probably continue to grow across the world, particularly in low-income countries.
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- Olsson, Louise, 1974, et al.
(author)
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A kinetic model for sulfur poisoning and regeneration of Cu/SSZ-13 used for NH3-SCR
- 2016
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 183, s. 394-406
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Journal article (peer-reviewed)abstract
- In this study, we have developed a multi-site kinetic model that describes the sulfur poisoning and gradual sulfur removal over Cu/SSZ-13 used for NH3-SCR. Sulfur poisoning was conducted under SCR conditions and thereafter, repeated SCR experiments were conducted to examine the effect of such poisoning and the subsequent gradual removal of sulfur. In addition, the effect of sulfur poisoning was examined on NH3 TPD and ammonia oxidation experiments. The following sites were used in the kinetic model: copper in the six-membered rings as described by S1Cu, copper in the larger cages with S2 and S3 as a site where physisorbed ammonia can attach. Further, ammonia was also adsorbed on the Brönsted sites, represented by S1Brön in the model, but in order not to further complicate the model, small amounts of ammonia storage on Brönsted sites were also lumped into S2. In the model, SO2 was adsorbed on the sites containing copper, which are S1Cu and S2. It should be noted that S1Cu and S2 represents hydrated copper sites. Interestingly, we observed experimentally that ammonia storage was larger after sulfur poisoning compared to before, which is why we added ammonia storage and desorption to the S1Cu-SO2 and S2-SO2 sites. However, ammonia was already adsorbing on the copper site; thus, these steps did not result in increased storage. Consequently, reaction steps were added where additional ammonia was adsorbed to form S1Cu-SO2-(NH3)2 and S2-SO2-(NH3)2 species, which could be interpreted as precursors to ammonium sulfates. Another aspect that must be addressed in the model is the observation in the literature that SO2 is more easily desorbed in SO2+NH3+O2 TPD than SO2+O2 TPD. Reversible reaction steps were therefore added whereby the S1Cu-SO2-NH3 and S2-SO2-NH3 species were decomposed to form SO2. A final reaction step was incorporated into the model to describe the SCR reaction with ammonia attached to the sulfur sites. The developed model could well describe the sulfur poisoning and gradual regeneration during repeated SCR experiments. In addition, the model well described the NH3 TPD and NH3 oxidation before and after sulfur poisoning.
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| 6. |
- Olsson, Louise, 1974, et al.
(author)
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A multi-site kinetic model for NH3-SCR over Cu/SSZ-13
- 2015
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 174, s. 212-224
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Journal article (peer-reviewed)abstract
- In this study, we have developed a kinetic model for ammonia-SCR over a well-characterized Cu/SSZ-13 catalyst. It was found that a three-site model was needed in order to describe the ammonia temperature programmed desorption (TPD) with adsorption at 50 and 150 degrees C as well as ammonia oxidation, and NH3-SCR up to 600 degrees C. Based on literature studies, where detailed characterization of Cu/SSZ-13 have been conducted using several experimental techniques', we suggest the following physical interpretation of the S1 and S2 sites in the model. The S1 sites are associated with copper located in a six-membered ring, possibly slightly distorted due to interactions with-water and ammonia while, the S2 sites represent copper in the large cages or CuxOy species. In addition, ammonia is also stored on Bronsted acid sites, but in order not to complicate the model further, it was lumped together in the S1 and S2 sites. Finally, S3 sites have been added in order to describe the large amount of physisorbed ammonia at low temperature. This three-site model was capable of adequately describing the ammonia TPD experiments with the initial temperature of 50 and 150 degrees C. The heats of adsorption of ammonia on the Si and S2 sites were determined using micro-calorimeter experiments. Further, the main SCR reaction in the model occurs on S1 sites and the main ammonia oxidation reaction on S2 sites. However, due to the complex behavior associated with ammonia oxidation, where the conversion slightly decreased when the temperature was increased from 350 to 400 degrees C, an ammonia oxidation reaction occurring at low temperature with low rate needed to be introduced on S1. In a similar way, an added step was needed for ammonia-SCR on S2, which occurred at high temperature where the ammonia coverage on Si was low resulting in low conversion. To summarize, the-three-site model developed was capable of well describing the ammonia storage and release, ammonia oxidation as well as SCR and N2O formation across a broad temperature interval (100-600 degrees C).
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| 7. |
- Supriyanto, , 1985, et al.
(author)
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Global kinetic modeling of hydrothermal aging of NH3-SCR over Cu-zeolites
- 2015
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 163, s. 382-392
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Journal article (peer-reviewed)abstract
- In this study, a kinetic model describing the effect of hydrothermal aging (at 500, 600, 700, 800 and 900 degrees C) on Cu-zeolites is developed. The model accounts for the impact of hydrothermal aging on key reactions such as ammonia adsorption/desorption, NH3 oxidation, NO oxidation, standard SCR, rapid SCR, and NO2 SCR. In addition, a mechanism for the complex N2O formation were developed. The effect of aging on ammonia adsorption and desorption were established using micro-calorimeter data. Thereafter, an aging factor model was developed containing two aging factors, one related to over-exchanged copper sites and the other to under-exchanged copper sites. This approach worked well for ammonia and NO oxidation up to an aging temperature of 800 degrees C, whereas for the SCR reactions only to 700 degrees C. According to UV-vis, fresh and mildly aged catalysts are dominated by copper hydroxyls, while after aging at high temperature copper oxides are observed. We therefore introduce one SCR reaction associated with copper oxides, simultaneously with one SCR reaction associated with ion-exchanged Cu sites and the updated model could describe the experimental findings well. The results from the model also suggest that the standard SCR reaction is more deactivated during aging compared to SCR with NO2 present in the feed. After the 900 degrees C aging the BEA structure had collapsed, resulting in that several parameters in the model needed to be retuned. The results from this modeling study clearly show how complex the hydro thermal aging is over copper zeolites.
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| 8. |
- Wijayanti, Kurnia, 1979, et al.
(author)
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Deactivation of Cu-SSZ-13 by SO2 exposure under SCR conditions
- 2016
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In: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 6:8, s. 2565-2579
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Journal article (peer-reviewed)abstract
- A deactivation study of Cu-SSZ-13 has been conducted using SO2 exposure under SCR conditions and examining its effect on different reactions involving NH3-SCR. Several reactions, including NH3 storage/TPD, NO/NH3 oxidation, standard SCR, fast SCR and SCR with 75% NO2, as well as NH3-NO2 storage/TPD, were investigated at a temperature range of 100-400 degrees C after exposing the catalyst to 30 ppm SO2 under SCR conditions at 300 degrees C for 90 min. The catalyst was characterized using XRD, BET, ICP-SFMS and H-2-TPR. The BET surface area and pore volume decreased after the sulfur treatment presumably due to blocking by sulfur and/or ammonium-sulfur species. It was found that sulfur was not uniformly deposited along the monolith channel. The deposition occurred from the inlet towards the outlet, as evident from ICP-SFMS measurements. Part of the sulfur was removed after an SCR experiment up to 400 degrees C. However, this removal was observed only in the inlet half of the sample and not in the outlet. Ammonia TPD experiments revealed that the sulfur poisoning resulted in additional sites that were capable of adsorbing ammonia, resulting in increased ammonia storage. Moreover, standard SCR was significantly deactivated by SO2 poisoning under SCR conditions. Due to the site-blocking effect of the ammonium-sulfur species, fewer copper sites are likely available for the redox SCR cycle. Furthermore, the effect of sulfur poisoning on NH3 oxidation and NO2-SCR as well as N2O production in various SCR reactions were observed. Finally, it was found that the conditions for the sulfur poisoning were critical in which SO2 deactivation under SCR conditions (NH3 + NO+ O-2 + H2O) was more severe compared to SO2 poisoning in O-2 + H2O alone.
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| 9. |
- Wijayanti, Kurnia, 1979, et al.
(author)
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Impact of sulfur oxide on NH3-SCR over Cu-SAPO-34
- 2015
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 166, s. 568-579
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Journal article (peer-reviewed)abstract
- An investigation into the impact of sulfur oxide on the activity of Cu-SAPO-34 towards selective catalytic reduction of NOx by NH3 has been conducted to clarify the possible mechanism of deactivation induced by sulfur. Several reactions including NH3 storage/TPD, NO/NH3 oxidations, standard and fast SCR, as well as SCR with an NO2/NOx ratio of 75% were performed at temperature range of 150-500 degrees C over the fresh Cu-SAPO-34 after it had been sulfated at 300 degrees C with 30 ppm SO2 in the presence of 8% O-2 and 5% H2O for 90 min. The catalyst is characterized by using XRD, BET, ICP-AES, H-2-TPR and micro-calorimetry. The BET surface area as well as the pore volume decreased after sulfur poisoning, hence some pores in the zeolite were blocked by sulfur. The standard SCR reaction was significantly influenced by the sulfur poisoning. The H-2-TPR data showed that there is less available copper that could undergo the redox cycle for the sulfated sample compared to the fresh sample and this could be the main reason for the deactivation seen. The conversion for NO during standard SCR showed a more pronounced decrease in activity compared to that of fast SCR and the smallest effect of the sulfur poisoning was observed for SCR with the 75% NO2/NOx. Hence, the SCR reactions in the presence of NO2 are less influenced by the sulfur on the surface and it is likely that the mechanism is different for SCR in the presence of NO2. Cu-SAPO-34 produced very small amounts of N2O and its production correlated with the amount of NO2 in the feed. From the calorimeter experiment, it was observed that the binding of SO2 is very strong on the catalyst sites, most likely the copper sites, and the heat of adsorption of SO2 was higher in the presence of O-2.
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| 10. |
- Leistner, Kirsten, 1984, et al.
(author)
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Comparison of Cu/BEA, Cu/SSZ-13 and Cu/SAPO-34 for ammonia-SCR reactions
- 2015
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In: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 258, s. 49-55
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Journal article (peer-reviewed)abstract
- In this study, the ammonia-SCR process was investigated using 2.5 wt.% Cu/BEA, 2.6 wt.% Cu/SAPO-34 and 3.1 wt.% Cu/SSZ-13. Several reactions such as NO oxidation, ammonia oxidation, standard SCR, fast SCR and NO2 SCR were studied to understand the effect of zeolite type. It was found that the small-pore zeolites/silicoaluminophosphates with CHA structure (Cu/SAPO-34 and Cu/SSZ-13) exhibited higher SCR activity at 150°C and lower selectivity toward N2O formation during standard SCR conditions than Cu/BEA. However, formation of ammonium nitrate species during fast SCR conditions at 150°C occurred over Cu/CHA catalysts, which resulted in a gradual decrease of the NOx conversion. Such blocking was also observed over Cu/BEA, albeit to a minor extent. The ammonium nitrate formation and its decomposition temperature regimes resulted in that the Cu/BEA was catalytically more active at lower temperature than either Cu/SAPO-34 or Cu/SSZ-13 during fast SCR conditions. Additionally, our results show that the ammonium nitrate species were more stable on the small-pore zeolites than on Cu/BEA. Comparing the two Cu/CHA catalysts, Cu/SAPO-34 and Cu/SSZ-13, it was found that ammonia oxidation at high temperatures and ammonia SCR at 150°C was higher on Cu/SAPO-34. Further, TPR experiments showed that Cu in Cu/SAPO-34 is more easily reduced compared to Cu/SSZ-13. This can facilitate the redox processes and can thereby be a reason for the higher activity at 150°C for Cu/SAPO-34. In addition, Cu/SAPO-34 forms less N2O and this might be a result of the formation of more stable ammonium nitrates. To conclude, the choice of the type of zeolite/silicoaluminophosphates affects the activity and selectivity of the different steps in the SCR process.
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| 11. |
- Leistner, Kirsten, 1984, et al.
(author)
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Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34
- 2017
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In: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 10:4
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Journal article (peer-reviewed)abstract
- We developed a procedure for aqueous ion exchange to obtain different Cu loadings of Cu/SAPO-34 (between 0 and 2.6 wt %). The catalysts were washcoated on monoliths and characterised with respect to their activity and selectivity under standard selective catalytic reduction (SCR), fast SCR, NH3 oxidation and NO oxidation reactions. They were further characterised using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), H-2-temperature programmed reduction (H-2-TPR), ultraviolet (UV)-vis spectroscopy and NH3 adsorption. As expected, activity of all reactions increased with copper loading, due to increased number of active sites. However, the N2O formation during standard and fast SCR yielded interesting mechanistic information. We observed that N2O formation at low temperature increased with copper loading for the standard SCR reaction, while it decreased for fast SCR. The low-temperature N2O formation during fast SCR thus occurs predominantly over Bronsted sites. Species responsible for N2O formation during standard SCR, on the other hand, are formed on the copper sites. We further found that the fast SCR reaction occurs to a significant extent even over the H/SAPO-34 form. The Bronsted sites in SAPO-34 are thus active for the fast SCR reaction.
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| 12. |
- Wijayanti, Kurnia, 1979, et al.
(author)
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Effect of gas compositions on SO2 poisoning over Cu/SSZ-13 used for NH3-SCR
- 2017
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 219, s. 142-154
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Journal article (peer-reviewed)abstract
- This study focuses on the effect of gas composition during SO2 poisoning over Cu/SSZ-13 for NH3-SCR application and was performed by conducting SO2-TPD experiments in a variety of lean gas compositions. In addition, the poisoned monoliths were characterized in detail using ICP-SFMS, UV–vis and XPS. During SO2 poisoning under dry and lean conditions, two different sulfur species were found, which were assigned to weakly bound SO2 and copper sulfate like species. Moreover, a significantly larger amount of copper sulfates was present in humid environment. The presence of NH3 during the poisoning resulted in the formation of ammonium sulfate species which were decomposed at the same temperature independently if the poisoning with SO2 was conducted in ammonia oxidation conditions or under standard or fast SCR conditions. Moreover, if the temperature ramp was conducted with O2 and H2O compared to Ar alone, more stable sulfate species were formed. In addition, SO2 poisoning under standard SCR conditions resulted in mostly ammonium sulfate formation at 200 °C, whereas copper sulfates were predominant after poisoning at 400 °C. After hydrothermal aging at 800 °C, more reducible copper species were noticeable and UV–vis showed that copper oxides had been formed. Sulfur poisoning of the hydrothermally aged sample resulted in the additional formation of copper sulfates during poisoning at 200 °C, which was not the case for poisoning of the fresh catalyst. Thus, the copper oxide species enhanced the copper sulfate formation.
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| 13. |
- Wilken, Norman, 1983, et al.
(author)
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Mechanistic investigation of hydrothermal aging of Cu-Beta for ammonia SCR
- 2012
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 111, s. 58-66
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Journal article (peer-reviewed)abstract
- The selective catalytic reduction of NO with NH3 over a Cu-BEA catalyst was studied after hydrothermal aging between 500 and 900 degrees C. The corresponding catalyst was characterized using XPS and XRD techniques in the aging interval of 500, 700 and 800 degrees C. No structural changes during the aging process were observed. However, the oxidation state of copper changed during aging and more Cu2+ was formed. We suggest that one of the deactivation mechanisms is the decrease of the Cu+ species. The NO oxidation and NH3 oxidation activity was decreased with increasing aging temperature. Further, we observed that the ammonia oxidation was decreased faster compared to the SCR reactions at low aging temperatures. The experiments from the calorimeter as well as from the ammonia TPD investigations indicate a trend towards more weakly bound ammonia with higher aging temperatures. From the results of the SCR experiments using different NO2/NOx ratios and ammonia oxidation experiments we suggest that most of the N2O is coming from side reactions of the SCR mechanism and not from reactions between NH3 and O-2 alone. Interestingly, we observe that after the 900 degrees C aging a quite large activity remained for the case with 75% NO2/NOx ratio. The N2O production shows a maximum at 200 degrees C, but increases again at higher temperatures. However, the N2O formed at low temperature is decreased after hydrothermal aging while the high temperature N2O is increased. We propose that the different reactions examined in this work do not all occur on the same type of sites, since we observe different aging trends for some of the reactions.
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| 14. |
- Wilken, Norman, 1983, et al.
(author)
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The effect of accelerated hydrothermal aging on NH 3-SCR over Cu-Hbea catalyst
- 2011
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In: 11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings. - 9780816910700
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Conference paper (peer-reviewed)abstract
- Diesel engines have good fuel efficiency. However, the excess of oxygen that is fed into the engine is also present in the exhaust stream. This disables the selectivity of the standard three-way catalyst towards NO x. The influence of hydrothermal aging on the SCR mechanism was studied. A trend towards less strong bound ammonia for higher aging temperatures is observed, which agreed with TPD experiments. Ammonia SCR is an important technique for reducing NO x from diesel and lean burn gasoline engines. Zeolite based catalysts are a good choice for this reaction. However, they can be hydrothermally aged. This is an abstract of a paper presented at the 2011 AIChE Annual Meeting (Minneapolis, MN 10/16-21/2011).
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| 15. |
- Xie, Kunpeng, 1985, et al.
(author)
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Influence of phosphorus on Cu-SSZ-13 for selective catalytic reduction of NOx by ammonia
- 2017
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In: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 297, s. 46-52
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Journal article (peer-reviewed)abstract
- The influence of phosphorus on Cu-SSZ-13 NH3-SCR catalysts was investigated in order to reveal the deactivation behavior of Cu-SSZ-13 in the presence of phosphorus-containing poisons in the exhaust of diesel engines. The phosphorus-poisoning was simulated by treating the Cu-SSZ-13 catalysts with (NH4)(2)HPO4 aqueous solution using incipient wetness impregnation method. The focus of the study was the effect of phosphorous on the different reactions occurring on the SCR catalyst, including ammonia oxidation, NO oxidation and standard SCR using monolith catalysts. Moreover, characterization such as ICP-SFMS, N-2-physisorption, and NH3-TPD were employed for the evaluation of the physical and chemical properties of the P-impregnated catalysts. Physically blocking of pores and poisoning of acidic sites were observed on the P-impregnated catalysts. In addition, we observed that phosphorus severely suppressed ammonia oxidation and NO oxidation, while its impact on standard SCR reaction was nearly negligible below 300 degrees C. Interestingly, a promotive effect was found at higher temperatures, likely due to the severely inhibiting effect on NH3 oxidation caused by the formation of copper phosphates in the large cages (i.e. 8-membered rings) of Cu-SSZ-13.
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