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Characterization And Performances Of Nanosized Bi Metallic Fe Based Zeolite Catalysts During Selective Catalytic Reduction Scr Of No By Nh3
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Book Synopsis Characterization and Performances of Nanosized Bi-metallic Fe-based Zeolite Catalysts During Selective Catalytic Reduction (SCR) of NO by NH3 by : 莎亞達
Download or read book Characterization and Performances of Nanosized Bi-metallic Fe-based Zeolite Catalysts During Selective Catalytic Reduction (SCR) of NO by NH3 written by 莎亞達 and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Characterization and Design of Zeolite Catalysts by : Miki Niwa
Download or read book Characterization and Design of Zeolite Catalysts written by Miki Niwa and published by Springer Science & Business Media. This book was released on 2010-08-17 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysis and catalyst is a key technology to solve the problems in energy and environment issues to sustain our human society. We believe that comprehensive understanding of the catalysis and catalyst provides us a chance to develop a new catalyst and contributes greatly to our society. However, the ?eld of heterogeneous catalyst is dif?cultto study andstill stays behindmoredeveloped?elds ofchemistry such as organic and physical chemistries. This is a dilemma to the chemists who study the catalysis and catalyst. While we can accomplish the progress in the - dustrial application, the scienti?c understandingis not complete yet. A gap between the useful application and incomplete scienti?c understanding, however, becomes smaller and smaller in recent years. Because zeolites are ?ne crystals, and the structure is clearly known, the study on the catalysis using the zeolites is easier than those encountered in other catalysts such as metals and metal oxides. Very fortunately, zeolites provide us the strong acidity with the ?ne distribution which enables various useful catalytic reactions. When some metals and cations are loaded in close to the acid sites, these loadede- ments show extraordinarycharacters, and many catalytic reactions proceed thereon.
Book Synopsis Modeling and Analysis of Performance on a Field-aged Fe-zeolite Catalyst by : Roxanna Moores
Download or read book Modeling and Analysis of Performance on a Field-aged Fe-zeolite Catalyst written by Roxanna Moores and published by . This book was released on 2014 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study a 1-dimensional computational model implementing conservation of mass, species and energy for both the gas phase and catalyst surface has been developed to predict the performance of an Fe-Zeolite selective catalytic reduction catalyst. This work investigates and analyzes the behavior of a fresh Fe-Zeolite catalyst as well as one that has been aged in a Heavy Duty Diesel engine performing in the field for 376k miles. The chemistry and performance for the two Fe-Zeolite configurations for the NH3 Storage, NH3 oxidation, NO Oxidation, Standard, Slow and Fast reactions are correlated and examined against synthetic gas rig test bench data and then subsequently verified with engine laboratory testing. It has been found that the Standard reaction was the most degraded reaction and the Fast reaction was the least affected by aging. As a result, in order to have the field-aged catalyst functioning to its optimized activity, the Fast reaction needs to be activated by keeping the NOx gas feed with a 50 % NO and 50 % NO2 gas composition.
Book Synopsis Accelerated Thermal Aging of Iron-zeolite SCR Catalyst on an Engine Bench by : Adam Lamar Foster
Download or read book Accelerated Thermal Aging of Iron-zeolite SCR Catalyst on an Engine Bench written by Adam Lamar Foster and published by . This book was released on 2008 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selective catalytic reduction (SCR) of NO[Subscript x] with urea/NH[Subscript 3] is a leading candidate to the impending more stringent emissions regulations for diesel engines. Currently, there is no consensus on the durability and the deactivation mechanisms associated with zeolite-based SCR catalysts, nor is there an established protocol for rapidly aging zeolite-based SCR catalysts that replicates the catalyst deactivation associated with field service. A 517 cc single-cylinder, naturally-aspirated direct injection (NA/DI) diesel engine is used to perform accelerated thermal aging on Fe-zeolite SCR catalysts. The engine is fitted with an exhaust aftertreatment system consisting of a DOC, a SCR catalyst and a DPF. Accelerated aging protocol established for the SCR catalyst utilizes high temperature exhaust gases during the active regeneration of the DPF. Accelerated aging is carried out at exhaust gas temperatures of 650, 750 and 850°C at the SCR inlet and at a gas hourly space velocity (GHSV) of approximately 40,000 h−1. The engine is maintained at 1500 rpm and supplemental fuel is injected upstream of the DOC to alter the temperature of the aftertreatment system. The aged Fe-zeolite SCR catalysts are evaluated for NO[Subscript x] performance in a bench-flow reactor and characterized by multiple surface characterization techniques for materials changes. The NO[Subscript x] performance of the front sections of the engine-aged catalysts is severely degraded. BET surface area measurements of the engine-aged catalyst indicate a severe reduction of catalyst surface area in the front sections of the catalysts aged at 750 and 850°C. However, the catalyst aged at 650°C has a catalyst surface area similar to that of a fresh catalyst; thereby ruling out reduction of catalyst surface area as the sole cause of the catalyst deactivation seen in the front sections of the engine-aged catalysts. The similar shape of the NO[Subscript x] conversion profiles observed with these catalyst sections even at different aging temperatures indicates some type of catalyst poisoning; however, the cause of catalyst degradation in these catalyst sections is not identified in this investigation. There is a good relationship between the NO[Subscript x] performance and catalyst aging temperature for the rear sections of the engine-aged catalysts - NO[Subscript x] performance decreases with increasing aging temperature. XRD patterns and NO oxidation experiments reveal evidence of zeolite dealumination in the engine-aged catalysts. BET surface area measurements show that catalyst surface area decreases with increasing aging temperature, which further supports the suggestion of zeolite dealumination as the cause of catalyst deactivation in the rear sections of the engine-aged catalysts. A comparison between the engine-aged and field-aged catalysts is conducted to assess the validity of the implemented accelerated thermal aging protocol in replicating the aging conditions observed in the field-aged catalyst. Bench-flow reactor evaluation is used to determine the NO[Subscript x] performance of the engine-aged and field-aged catalysts, and in depth surface studies are used to determine the deactivation mechanisms associated with each type of catalyst aging. SEM micrographs and BET surface area measurements of the aged catalysts show that the deactivation mechanism associated with catalyst aging is primarily physical damage to the zeolite washcoat for both the field-aged and engine-aged catalysts. Furthermore, X-ray diffraction and NO oxidation experiments identify zeolite dealumination as the underlying cause of the washcoat degradation. Finally, BFR evaluation shows that the NO[Subscript x] performance of the catalyst aged at 750°C for approximately 50 hours compares very well to that of the field-aged catalyst with a service life of 3 years. It is concluded that accelerated thermal aging on the engine bench is successful in bringing about similar catalyst changes to those seen with the field-aged catalyst.
Book Synopsis New and Future Developments in Catalysis by : Zdenek Sobalik
Download or read book New and Future Developments in Catalysis written by Zdenek Sobalik and published by Elsevier Inc. Chapters. This book was released on 2013-07-17 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental and Kinetic Modeling Studies of Selective Catalytic Reduction of NOx with NH3 on Fe- and Cu-Zeolite Monolithic Catalysts by : Pranit Subhash Metkar
Download or read book Experimental and Kinetic Modeling Studies of Selective Catalytic Reduction of NOx with NH3 on Fe- and Cu-Zeolite Monolithic Catalysts written by Pranit Subhash Metkar and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The selective catalytic reduction (SCR) of NOx with NH3 is considered to be the most promising technique for the efficient reduction of highly detrimental NOx (to N2) emitted from diesel engine vehicles. Amongst the various catalysts available for SCR, Fe- and Cu-zeolite catalysts are found to be highly stable and efficient towards maximum NOx reduction over a wide temperature range. Cu-zeolites are more active at low temperatures ( 350 oC) while Fe-zeolites are more active at high temperatures ( 400 oC). We carried out a comprehensive experimental and kinetic modeling study of key SCR reactions on Fe- and Cu-zeolite catalysts and present a detailed understanding of mass transfer limitations and kinetics and mechanistic aspects of various SCR reactions on these catalysts. Experiments carried out on monolith catalysts having different washcoat loadings, washcoat thicknesses and lengths indicate the presence of washcoat (or pore) diffusion limitations at intermediate to high temperature range in all the SCR reactions. A detailed analysis of the effect of temperature on the transitions between various controlling regimes (kinetic, washcoat diffusion and external mass transfer) is presented. Agreement in the differential kinetics studies of NO oxidation and standard SCR (NO + O2 + NH3) reactions indicates NO oxidation is the rate determining step for standard SCR. A detailed kinetic model capturing key features of all the SCR reactions is developed. This model accurately predicts the experimentally observed NOx conversions over a wide temperature range and different feed conditions. Finally, a systematic study of various SCR reactions is carried out on a combined system of Fe- and Cu-zeolite monolithic catalysts to determine if a high NOx conversion could be sustained over a wider temperature range than with individual Fe- and Cu-zeolite catalysts. Amongst various configurations, a dual-layer catalyst with a thin Fe-zeolite layer on top of a thick Cu-zeolite layer resulted in a very high NOx removal efficiency over a broad temperature range of practical interest. The kinetic model accurately captures the experimental data with a combined system of Fe- and Cu-zeolite catalysts and provides further insights into the catalyst arrangements for maximum NOx reduction efficiency.
Book Synopsis Nano Catalysts for Diesel Engine Emission Remediation by :
Download or read book Nano Catalysts for Diesel Engine Emission Remediation written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project was to develop durable zeolite nanocatalysts with broader operating temperature windows to treat diesel engine emissions to enable diesel engine based equipment and vehicles to meet future regulatory requirements. A second objective was to improve hydrothermal durability of zeolite catalysts to at least 675 C. The results presented in this report show that we have successfully achieved both objectives. Since it is accepted that the first step in NOx conversion under SCR (selective catalytic reduction) conditions involves NO oxidation to NO2, we reasoned that catalyst modification that can enhance NO oxidation at low-temperatures should facilitate NOx reduction at low temperatures. Considering that Cu-ZSM-5 is a more efficient catalyst than Fe-ZSM-5 at low-temperature, we chose to modify Cu-ZSM-5. It is important to point out that the poor low-temperature efficiency of Fe-ZSM-5 has been shown to be due to selective absorption of NH3 at low-temperatures rather than poor NO oxidation activity. In view of this, we also reasoned that an increased electron density on copper in Cu-ZSM-5 would inhibit any bonding with NH3 at low-temperatures. In addition to modified Cu-ZSM-5, we synthesized a series of new heterobimetallic zeolites, by incorporating a secondary metal cation M (Sc{sup 3+}, Fe{sup 3+}, In{sup 3+}, and La{sup 3+}) in Cu exchanged ZSM-5, zeolite-beta, and SSZ-13 zeolites under carefully controlled experimental conditions. Characterization by diffuse-reflectance ultra-violet-visible spectroscopy (UV-Vis), X-ray powder diffraction (XRD), extended X-ray absorption fine structure spectroscopy (EXAFS) and electron paramagnetic resonance spectroscopy (EPR) does not permit conclusive structural determination but supports the proposal that M{sup 3+} has been incorporated in the vicinity of Cu(II). The protocols for degreening catalysts, testing under various operating conditions, and accelerated aging conditions were provided by our collaborators at John Deere Power Systems. Among various zeolites reported here, CuFe-SSZ-13 offers the best NOx conversion activity in 150-650 C range and is hydrothermally stable when tested under accelerated aging conditions. It is important to note that Cu-SSZ-13 is now a commercial catalyst for NOx treatment on diesel passenger vehicles. Thus, our catalyst performs better than the commercial catalyst under fast SCR conditions. We initially focused on fast SCR tests to enable us to screen catalysts rapidly. Only the catalysts that exhibit high NOx conversion at low temperatures are selected for screening under varying NO2:NOx ratio. The detailed tests of CuFe-SSZ-13 show that CuFe-SSZ-13 is more effective than commercial Cu-SSZ-13 even at NO2:NOx ratio of 0.1. The mechanistic studies, employing stop-flow diffuse reflectance FTIR spectroscopy (DRIFTS), suggest that high concentration of NO, generated by heterobimetallic zeolites, is probably responsible for their superior low temperature NOx activity. The results described in this report clearly show that we have successfully completed the first step in a new emission treatment catalyst which is synthesis and laboratory testing employing simulated exhaust. The next step in the catalyst development is engine testing. Efforts are in progress to obtain follow-on funding to carry out scale-up and engine testing to facilitate commercialization of this technology.
Book Synopsis In Situ Mössbauer Spectroscopic Studies of Iron-exchanged Y-zeolite Catalysts for the Selective Catalytic Reduction (with Ammonia) and Direct Decomposition of Nitric Oxide by : Ralf Schmidt
Download or read book In Situ Mössbauer Spectroscopic Studies of Iron-exchanged Y-zeolite Catalysts for the Selective Catalytic Reduction (with Ammonia) and Direct Decomposition of Nitric Oxide written by Ralf Schmidt and published by . This book was released on 1991 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development and Characterization of Mixed Oxide Catalysts for the Selective Catlytic Reduction of Nitric Oxide from Stationary Sources Using Amonnia by :
Download or read book Development and Characterization of Mixed Oxide Catalysts for the Selective Catlytic Reduction of Nitric Oxide from Stationary Sources Using Amonnia written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Seven first row transition metals were deposited on various commercial TiO2, SiO2, and Al2 O3 supports to create mono- and bimetallic catalysts that were compared in the selective catalytic reduction of nitric oxide using ammonia at low temperatures ranging from 373-523 K. The catalyst with the highest activity both in the absence and presence of water in the feed was 20 wt.% Mn/Hombikat TiO2 synthesized from a nitrate precursor and calcined below 673 K. Under those conditions, it was capable of achieving 100% NO conversion at 393 K. Numerous surface characterization techniques were used to identify the surface properties that result in highly active and selective low temperature SCR catalysts. The deposition of manganese as MnO2, the ease of reducibility of the metal oxide, and the symmetric deformation of ammonia coordinated to Lewis acid sites at 1167 cm−1, were all found to be important for good catalytic performance. No synergistic effects were observed from combinations of the three most active transition metals. However, MnO x -NiO/TiO2 had an extended lifetime relative to MnO x /TiO2 in feeds containing SO2 . The extensive data collected from in-situ FTIR experiments in the presence of NO and NH 3 were used to propose a reaction mechanism for MnO x /TiO2 that begins with the coordination of NH3 over Mn4 species and proceeds through the formation of bridged nitrates. A combination of potentiometric titrations and UV/Vis spectroscopy were used to quantify the reduction of V5 to V4 after the addition of oxalic acid as the solution is aged. After approximately four hours, the aging vanadium oxalate solution reaches steady state, and the final distribution of the vanadium present is 89% V+4 and 11% V+5 . TiO2 supported monolayer catalysts synthesized from the aged (V+4) vanadium oxalate solution consistently outperformed catalysts made from freshly prepared (V+5) vanadium oxalate solutions. Surface characterization revealed that surface acid sites increase in strength and vanadia reduces more easily in catalysts synthesized from aged vanadium oxalate solutions, which enhances reaction mechanism depends upon acid sites and redox operation.
Book Synopsis Reactivity and Characterization of Supported Noble Metal Catalysts by : Keishla R. Rivera-Dones
Download or read book Reactivity and Characterization of Supported Noble Metal Catalysts written by Keishla R. Rivera-Dones and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytically driven processes account for over ninety percent of industrial chemical manufacturing today. Developments in manufacturing processes are largely driven by continued improvements in catalytic materials, which aim to increase production volumes while minimizing costs along with safety and environmental hazards. In order to achieve these goals, however, a rational approach in catalyst design must be pursued that aims to understand and build upon the fundamental structural, electronic, and chemical properties governing catalytic performance. To that purpose, the work presented in this dissertation makes use of kinetic experiments, theoretical models, and advanced characterization techniques to generate a fundamental understanding of noble metal surfaces employed in a variety of catalytic reaction systems. In Chapter 2, we discuss the use of N2 physisorption, CO chemisorption, and NH3 temperature programed desorption to evaluate the effect of support acidity on the reactivity profiles of various zeolite-supported Pt and Pt-Sn catalysts for the non-oxidative coupling of methane to ethylene and aromatics. Reactivity studies for Pt-Sn/H-ZSM-5 catalysts at 973 K showed that, while all catalysts produced ethylene as the primary product, increasing support acidity led to an increase in naphthalene selectivity at the expense of benzene selectivity. Volcano-shaped profiles observed for the generation of aromatic products suggest that the formation of a reactive hydrocarbon pool on acidic support surfaces could be responsible for the oligomerization of ethylene. Notably, the Pt-Sn/H-ZSM-5 (SiO2:Al2O3 = 50) catalyst was found to be comparable to the state-of-the-art Mo/H-ZSM-5 catalysts in terms of carbon product generation and resistance to coke formation. In Chapter 3, x-ray absorption spectroscopy (XAS) was used to highlight the effect of local electronic and structural environments in specially synthesized metallic catalysts. The local coordination and nearest-neighbor distance of Pd species were evaluated to understand metal dispersion and the effect of catalyst support on the extent of bimetallic particle formation in Pd, AgPd, CuPd, and AuPd catalysts synthesized by controlled surface reactions (CSR) for a variety of amination, hydrodechlorination, and hydrogenation reactions. Near-edge structure analyses were also used on these Pd catalysts, as well as on a set of Mo-containing multi-metallic catalysts prepared by atomic layer deposition (ALD) for synthesis gas conversion, to understand catalyst reducibility along with potential support and hydrogen spillover effects on the extent of metal reduction. Chapter 4 evaluates the effects of catalyst support and pretreatment conditions on the hydrogenation of acetone over SiO2-, Al2O3-, and ZSM-5-supported platinum catalysts. Pt/ZSM-5 catalysts were found to have specific conversion rates and turnover frequencies that were 2 - 3 orders of magnitude higher than those observed over Pt/SiO2 and Pt/Al2O3 catalysts, regardless of zeolite acidity or pretreatment conditions. For Pt/ZSM-5 catalysts, the higher activity was achieved by increasing calcination and decreasing reduction temperatures, likely due to the effects of these treatments on the morphology of the platinum particles. CO-FTIR measurements showed a shift to higher frequencies of the Pt-CO band in Pt/ZSM-5 catalysts compared to Pt/SiO2, which alluded to the interactions between Pt and the porous zeolite structure as a source of the activity enhancements observed. Chapter 5 introduces the use of transient kinetics studies and theoretical modeling to explore the importance of surface coverage effects in the hydrogenation of acetone over platinum. Transient models based on steady-state microkinetics using static and dynamic inclusion of surface coverage via the Langmuir and Bragg-Williams approximations, respectively, predicted notable differences in the decay profiles of the most abundant reactive intermediate (MARI) from the catalytic surface. Experimental studies using steady-state isotopic transient kinetic analysis (SSITKA) methods served to validate the theoretical predictions for transients induced by complete acetone removal from or its substitution in the reactant feed and provided tangible evidence for the importance of surface coverage effects in understanding the reactivity of platinum catalysts for acetone hydrogenation. Lastly, Chapter 6 addresses possible future research directions in the field of transient kinetics studies.
Book Synopsis Enhanced Activity of Nanocrystalline Zeolites for Selective Catalytic Reduction of NOx by : Vicki H. Grassian
Download or read book Enhanced Activity of Nanocrystalline Zeolites for Selective Catalytic Reduction of NOx written by Vicki H. Grassian and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline zeolites with discrete crystal sizes of less than 100 nm have different properties relative to zeolites with larger crystal sizes. Nanocrystalline zeolites have improved mass transfer properties and very large internal and external surface areas that can be exploited for many different applications. The additional external surface active sites and the improved mass transfer properties of nanocrystalline zeolites offer significant advantages for selective catalytic reduction (SCR) catalysis with ammonia as a reductant in coal-fired power plants relative to current zeolite based SCR catalysts. Nanocrystalline NaY was synthesized with a crystal size of 15-20 nm and was thoroughly characterized using x-ray diffraction, electron paramagnetic resonance spectroscopy, nitrogen adsorption isotherms and Fourier Transform Infrared (FT-IR) spectroscopy. Copper ions were exchanged into nanocrystalline NaY to increase the catalytic activity. The reactions of nitrogen dioxides (NO{sub x}) and ammonia (NH{sub 3}) on nanocrystalline NaY and CuY were investigated using FT-IR spectroscopy. Significant conversion of NO{sub 2} was observed at room temperature in the presence of NH{sub 3} as monitored by FT-IR spectroscopy. Copper-exchanged nanocrystalline NaY was more active for NO{sub 2} reduction with NH{sub 3} relative to nanocrystalline NaY.
Download or read book Ecocatalysis written by Claude Grison and published by Elsevier. This book was released on 2015-08-19 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reconquest of biodiversity; remediation of degraded and anthropic areas, prevention of environmental health risks; eco-innovation; Green industry ... The current French ambitions are closely related to an interdisciplinary approach to scientific ecology, all of which participate in the expected industrial renewal.Ecocatalysis explores the unusual combination of phytotechnologies adapted to pollution, ecological rehabilitation of polluted sites and enhancement of these processes through innovative green chemistry, all of which contribute to the development of scientific priorities; economic, ecological innovation and current environmental, of biomass conversion and transition from fossil fuels to renewable.
Book Synopsis Selective Catalytic Reduction of NOx by NH3 Over a Fe Zeolite Monolith Catalyst by : Nelson Salazar
Download or read book Selective Catalytic Reduction of NOx by NH3 Over a Fe Zeolite Monolith Catalyst written by Nelson Salazar and published by . This book was released on 2009 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Recent advances in shape selectivity of MFI zeolite and its effect on the catalytic performance by : Lan Zhang
Download or read book Recent advances in shape selectivity of MFI zeolite and its effect on the catalytic performance written by Lan Zhang and published by OAE Publishing Inc.. This book was released on 2023-01-01 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: MFI zeolite characterized by uniform pore size, adjustable acidity, and high-temperature resistance has a broad application prospect in catalytic reactions. However, controlling the product distribution of zeolite as a catalyst is still confronting great challenges and applications. It is considered as an effective way to control the product distribution by developing and improving new zeolites to modulate their shape selective effect. In recent years, researchers have achieved remarkable successes in investigating the shape selective modulation of zeolites on catalytic reaction and molecular diffusion. The microporous channels of MFI zeolite are the main places for the entry and exit of reactants or product molecules. This review provides the research progress of the shape-selective modulation of MFI zeolite channels and its influence on a series of catalytic performances in recent years. The shape-selective modulation of microporous channels of zeolite, encapsulation of micropores to metals, catalysis of mesoporous zeolite, and the distribution of framework Al were all systematically discussed. The development of advanced catalysts still faces great challenges and potential applications. Finally, we discussed the problems to be addressed urgently in the field of zeolite catalysts in the future.
Book Synopsis Selective Catalytic Reduction of NOx by NH3 (NH3-SCR) in Small Pore Cu-exchanged Chabazite (CHA) Catalysts by : Di Wang
Download or read book Selective Catalytic Reduction of NOx by NH3 (NH3-SCR) in Small Pore Cu-exchanged Chabazite (CHA) Catalysts written by Di Wang and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrogen oxides, NOx (NO+NO2), are considered significant air pollutants. Selective catalytic reduction of NOx with NH3 (NH3-SCR) is a leading technology candidate for NOx emissions control for diesel engine vehicles. Recently, the Cu-exchanged chabazite framework type zeolite with small pores, such as SAPO-34 and SSZ-13, has received a great deal of attention due to exceptional hydrothermal durability and enhanced SCR activity. I have carried out a systematic study over both Cu-SAPO-34 and Cu-SSZ-13 catalysts to elucidate the reaction mechanisms, acid properties, Cu structures, active centers and deactivation modes. First, the intrinsic mechanism of the SCR reaction over a Cu-exchanged SAPO-34 catalyst at low temperature was studied by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), coupled with a mass spectrometer to measure inlet and outlet gas concentrations. The evolution of the surface intermediates, as well as the reactivity of NH3 with surface NOx species and NOx with surface NH3 species, was evaluated. Second, a series of SAPO-34 catalysts with various Cu loadings (ranging 0.7-3.0 wt%) was prepared by a solid state ion exchange method (SSIE). The acid properties as well as the Cu structures were characterized by XRD, NH3-TPD, UV-vis, DRIFTS and H2-TPR. Third, a SSIE method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the SSIE process, the SSZ framework structure and surface area was maintained. DRIFTS and NH3-TPD experiments provide evidence that Cu ions were successfully exchanged with Brønsted acid protons in the pores. Fourth, the hydrothermal stability of Cu-SAPO-34 and Cu-SSZ-13 was studied. Their different evolutions of zeolite framework, acidity and Cu structure during the hydrothermal aging were probed by XRD, DRIFTS and NH3-TPD. The results suggest that Cu-SAPO-34 is more resistant to hydrothermal aging in comparison to Cu-SSZ-13. Last, the SO2 poisoning effect over Cu-SAPO-34 catalyst was investigated by using in-situ DRIFTS combined with temperature programmed desorption (TPD) experiments. It was found that the low temperature deactivation mechanism involved the formation of ammonium sulfate species as well as the competitive adsorption SO2 with NOx.
Book Synopsis In Situ Characterization During the Synthesis and Reaction of Ceria-based Mesoporous Catalysts for NH3-selective Catalytic Reduction (SCR) Applications by : Jun Shen
Download or read book In Situ Characterization During the Synthesis and Reaction of Ceria-based Mesoporous Catalysts for NH3-selective Catalytic Reduction (SCR) Applications written by Jun Shen and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Computational Insights Into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Exchanged Zeolite Catalysts by : Julian Rudolph
Download or read book Computational Insights Into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Exchanged Zeolite Catalysts written by Julian Rudolph and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We computationally investigate the mechanism of the reduction half-cycle of the selective catalytic reduction of nitrogen oxides with ammonia. We compare both Fe- and Cu-exchanged zeolite catalysts and aim at exploring all accessible reaction pathways. From our calculations, a comprehensive picture emerges that unifies several previous mechanistic proposals. We find that both for Fe and for Cu catalysts different reaction pathways are feasible but some of the possible reaction pathways differ in these two cases. Our computational results provide a basis for the interpretation of in situ spectroscopic investigations that can possibly distinguish the different mechanistic pathways.
