Showing papers on "Selective catalytic reduction published in 2017"
TL;DR: It is demonstrated that under reaction conditions, mobilized Cu ions can travel through zeolite windows and form transient ion pairs that participate in an oxygen (O2)–mediated CuI→CuII redox step integral to SCR.
Abstract: Copper ions exchanged into zeolites are active for the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia (NH3), but the low-temperature rate dependence on copper (Cu) volumetric density is inconsistent with reaction at single sites. We combine steady-state and transient kinetic measurements, x-ray absorption spectroscopy, and first-principles calculations to demonstrate that under reaction conditions, mobilized Cu ions can travel through zeolite windows and form transient ion pairs that participate in an oxygen (O2)-mediated CuI→CuII redox step integral to SCR. Electrostatic tethering to framework aluminum centers limits the volume that each ion can explore and thus its capacity to form an ion pair. The dynamic, reversible formation of multinuclear sites from mobilized single atoms represents a distinct phenomenon that falls outside the conventional boundaries of a heterogeneous or homogeneous catalyst.
594 citations
TL;DR: In this article, a series of transition metals (Co, Cu and Fe) were selected to decorate Ce-Ti mixed oxide to elevate the low-temperature activity of selective catalytic reduction of NO x by NH 3 (NH 3 -SCR) reaction.
Abstract: A series of transition metals (Co, Cu and Fe) were selected to decorate Ce-Ti mixed oxide to elevate the low-temperature activity of selective catalytic reduction of NO x by NH 3 (NH 3 -SCR) reaction, by adjusting the ratio of surface Ce 3+ species and oxygen vacancies. Among them, Co-Ce-Ti sample exhibited the excellent low-temperature activity and broadened temperature window, which could be attributed to the improvement of the physico-chemical properties and the acceleration of the reactions in the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Owing to the different ionic sizes of Co 2+ and Ce 4+ , the lattice distortion of Ce-Ti mixed oxide was greatly aggravated and subsequently increased the ratio of Ce 3+ and the surface adsorbed oxygen, which benefited the generation of adsorbed NO x species and improved the reaction in the L-H mechanism. Meanwhile, the coordinatively unsaturated cationic sites over the Co-Ce-Ti sample induced more Lewis acid sites and enhanced the formation of the adsorbed NH 3 species bounded with Lewis acid sites, which were considered as the crucial intermediates in E-R mechanism, and therefore facilitating the reaction between the adsorbed NH 3 species and NO molecules. The enhancements in both the reactions from L-H and E-R mechanisms appeared to directly correlated with the improved deNO x performance on the Co-Ce-Ti sample, and the L-H mechanism could be the dominate one at low temperatures due to its rapid reaction rate.
337 citations
TL;DR: In this article, a co-precipitation method for low-temperature selective catalytic reduction of NOx with NH3 (NOx-NH3-SCR) was proposed.
314 citations
TL;DR: This review mainly focuses on the effects of structure, morphology, and modified elements and on the role of catalyst supports in gaseous heterogeneous catalytic reactions.
Abstract: Manganese oxide has been recognized as one of the most promising gaseous heterogeneous catalysts due to its low cost, environmental friendliness, and high catalytic oxidation performance. Mn-based oxides can be classified into four types: (1) single manganese oxide (MnOx), (2) supported manganese oxide (MnOx/support), (3) composite manganese oxides (MnOx-X), and (4) special crystalline manganese oxides (S-MnOx). These Mn-based oxides have been widely used as catalysts for the elimination of gaseous pollutants. This review aims to describe the environmental applications of these manganese oxides and provide perspectives. It gives detailed descriptions of environmental applications of the selective catalytic reduction of NOx with NH3, the catalytic combustion of volatile organic compounds, Hg0 oxidation and adsorption, and soot oxidation, in addition to some other environmental applications. Furthermore, this review mainly focuses on the effects of structure, morphology, and modified elements and on the rol...
273 citations
TL;DR: In this article, the development of Cu-chabazite (CHA) catalysts represents a significant technology breakthrough for the removal of NOx by selective catalytic reduction (SCR) with ammonia.
Abstract: The development of Cu-chabazite (CHA) catalysts, i.e. Cu-SSZ-13 and Cu-SAPO-34, represents a significant technology breakthrough for the removal of NOx by selective catalytic reduction (SCR) with ammonia. Cu-CHA catalysts show an excellent hydrothermal stability towards high temperature aging and wide active temperature windows for the ammonia SCR reaction. This work summarizes the recent progress in the development of the Cu-CHA catalysts for the NH3-SCR reaction. The state of Cu in the reaction and the preparation methods on the catalytic performance are discussed. The advances in the understanding of the reaction mechanism are reviewed. The hydrothermal stability of the typical Cu-CHA catalysts are compared.
263 citations
TL;DR: In this paper, the authors summarized the studies about NOx emission reduction in diesel engines and discussed the benefits and constraints of different types of SCR, including Selective Catalytic Reduction (SCR), Lean NOx Trap (LNT), and SCR Filter (SCRF).
Abstract: NOx emissions have always been a main concern in the development of diesel engines. This paper summarizes the studies about NOx emission reduction in diesel engines. The need for meeting the stringent requirements with regard to NOx emissions in a diesel engine has led to the development of a range of after treatment techniques. After treatment methods are required to reduce NOx emissions that cannot be controlled by fuel composition and combustion phenomena. Current after treatment techniques that are being employed are Selective Catalytic Reduction (SCR), Lean NOx Trap (LNT) and SCR Filter (SCRF). The benefits and constraints of different types of SCR are discussed. Urea SCR is a prominent well proven technology. Urea SCR produces 96–99% conversion efficiency with the help of a reductant NH 3 . The operating parameters such as nature of catalyst, temperature range of catalyst, flow of DEF (Diesel Exhaust fluid) to injector and mixing of NH 3 and NOx are discussed. Hybrid SCR such as Cu-SCR + Fe-SCR, SCR + LNT moderates fuel consumption and augments the catalytic activity at low temperature. SCRF has low cell density (200–300 csi vs 400–600 csi for SCR), and also has lower deNOx efficiency for a number of reasons. Pre-stored NH 3 and Preheating helps in low temperature reaction of SCRF. Technical problems in aqueous urea systems have led to the evolution of solid SCR system (SSCR). This review incorporates the study of solid ammonium salts decomposition, temperature range of the salts and infrastructure required for SSCR.
165 citations
TL;DR: In this paper, a series of supported ceria-based catalysts for NH3-SCR were synthesized and then used as supports to prepare CeO2/TiO2-A, C O O O 2/Ti O 2-B, and C O 2 O 2O 2-R catalysts.
Abstract: Anatase (A) TiO2 is widely used as a support of the supported vanadium-based and non-vanadium-based catalysts for NH3-SCR reaction. However, there is lack of enough attention for brookite (B) and rutile (R) TiO2. Therefore, in the present work, we synthesize a series of TiO2-A, TiO2-B, and TiO2-R, and then used as supports to prepare CeO2/TiO2-A, CeO2/TiO2-B, and CeO2/TiO2-R catalysts with the purpose of clarifying the crystal form effect of TiO2 supports on the physicochemical properties and catalytic performance of these supported ceria-based catalysts for NH3-SCR reaction. Characterization results exhibit that H2 consumption (responding to reduction property), acid amounts, surface Ce3+ content, surface adsorbed oxygen species, and catalytic performance of these supported ceria-based catalysts give the order of CeO2/TiO2-R > CeO2/TiO2-B > CeO2/TiO2-A, which is related to the interaction (i.e., Ce3+ + Ti4+ ↔ Ce4+ + Ti3+) between CeO2 and TiO2 (anatase, brookite, and rutile). Especially, CeO2/TiO2-R catalyst exhibits the optimal catalytic performance for NH3-SCR reaction among these supported ceria-based catalysts owing to the most excellent reduction property as well as the largest amounts of acid sites, surface Ce3+ content, and surface adsorbed oxygen species.
160 citations
TL;DR: In this article, the best V2O5/Ce1-xTixO2 (3, 5, and 7 wt % V; x = 0, 0.5, 1) and bare supports were tested in the selective catalytic reduction (SCR) of NO by NH3 at different gas hourly space velocities (GHSVs) and were comprehensively characterized using XRD, pseudo in situ XPS, and UV-vis DRS as well as EPR and DRIFTS in in situ and operando mode.
Abstract: Supported V2O5/Ce1–xTixO2 (3, 5, and 7 wt % V; x = 0, 0.1, 0.3, 0.5, 1) and bare supports have been tested in the selective catalytic reduction (SCR) of NO by NH3 at different gas hourly space velocities (GHSVs) and were comprehensively characterized using XRD, pseudo in situ XPS, and UV–vis DRS as well as EPR and DRIFTS in in situ and operando mode. The best V/Ce1–xTixO2 (x = 0.3, 0.5) catalysts showed almost 100% NO conversion and N2 selectivity already at 190 °C with a GHSV value of 70000 h–1, which belongs to the best performances observed so far in low-temperature NH3-SCR of NO. The corresponding bare supports still converted around 80% to N2 under the same conditions. On bare supports, SCR proceeds via a Langmuir–Hinshelwood mechanism comprising the reaction of adsorbed surface nitrates with adsorbed NH3. On V/Ce1–xTixO2, nitrate formation is not possible, and an Eley–Rideal mechanism is working in which gaseous NO reacts with adsorbed NH3 and NH4+. Lewis and Bronsted acid sites, though adsorption o...
152 citations
TL;DR: In situ DRIFT suggested that the NH3-SCR of NO over MnOx-FeOx nanoneedles follows both Eley-Rideal and Langmuir-Hinshelwood mechanisms.
Abstract: In this work, a novel porous nanoneedlelike MnOx–FeOx catalyst (MnOx–FeOx nanoneedles) was developed for the first time by rationally heat-treating metal–organic frameworks including MnFe precursor synthesized by hydrothermal method. A counterpart catalyst (MnOx–FeOx nanoparticles) without porous nanoneedle structure was also prepared by a similar procedure for comparison. The two catalysts were systematically characterized by scanning and transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, ammonia temperature-programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFT), and their catalytic activities were evaluated by selective catalytic reduction (SCR) of NOx by NH3. The results showed that the rationally designed MnOx–FeOx nanoneedles presented outstanding low-temperature NH3-SCR activity (100% NOx conversion in a wide temperature window from 120 to...
145 citations
TL;DR: In this article, a series of ultra-low content copper-modified TiO 2 /CeO 2 catalysts were prepared by wet impregnation method and tested for selective catalytic reduction of NO by NH 3.
Abstract: A series of ultra-low content copper-modified TiO 2 /CeO 2 catalysts were prepared by wet impregnation method and tested for selective catalytic reduction of NO by NH 3 . The catalyst with a Cu/Ce molar ratio of 0.005 showed the best low-temperature activity and excellent sulfur-poisoning resistance. It was worth noting that the very small amounts of copper addition can lead to three times the activity at low temperature. The prepared catalysts were characterized by XRD, BET, Raman, XPS, NH 3 -TPD and the results revealed that the introduction of copper increased the amount of surface adsorbed oxygen and Ce 3+ species on the catalyst surface and generated more Bronsted acid sites. The redox and surface acidic properties were also improved by the addition of Cu. All these factors played important roles in enhancing NH 3 -SCR performance of TiO 2 -CuO/CeO 2 catalysts. Furthermore, in situ DRIFT experiments demonstrated that Cu doping enhanced the adsorption capacity of NH 3 while the appearance of CuO weakened the adsorption ability of bridging nitrates, both the two factors synergistically facilitated the NH 3 -SCR reaction proceed smoothly via the Eley-Rideal pathway.
140 citations
TL;DR: In this paper, the first example of Mn(i)-catalysed hydrogenation of CO2 to HCOOH was reported, achieving TONs up to 10,000 and quantitative yields after 24 h using DBU as the base at 80 °C and 80 bar total pressure.
Abstract: The catalytic reduction of carbon dioxide is of great interest for its potential as a hydrogen storage method and to use carbon dioxide as C-1 feedstock. In an effort to replace expensive noble metal-based catalysts with efficient and cheap earth-abundant counterparts, we report the first example of Mn(i)-catalysed hydrogenation of CO2 to HCOOH. The hydride Mn(i) catalyst [Mn(PNPNH-iPr)(H)(CO)2] showed higher stability and activity than its Fe(ii) analogue. TONs up to 10 000 and quantitative yields were obtained after 24 h using DBU as the base at 80 °C and 80 bar total pressure. At catalyst loadings as low as 0.002 mol%, TONs greater than 30 000 could be achieved in the presence of LiOTf as the co-catalyst, which are among the highest activities reported for base-metal catalysed CO2 hydrogenations to date.
TL;DR: In this paper, a series of Cux-Ce0.5 oxides catalysts with different Cu/Ce ratio were synthesized by citric acid method and the catalysts were characterized by XRD, BET surface area, H2-TPR, NH3-TPD, NO TPD, XPS and in-situ DRIFTS.
Abstract: A series of Cux-Ce0.5-x-Zr0.5 oxides catalysts with different Cu/Ce ratio were synthesized by citric acid method. The catalysts were characterized by XRD, BET surface area, H2-TPR, NH3-TPD, NO-TPD, XPS and in-situ DRIFTS. The synergistic effect between copper and cerium on the catalytic performance of Cux-Ce0.5-x-Zr0.5 for selective catalytic reduction of NO with ammonia was investigated. It was found that the Cu0.2-Ce0.3-Zr0.5 catalyst show the excellent SCR activity, N2 selectivity and H2O/SO2 durability in a low temperature range of 150–270 °C even at high gas hourly space velocity of 84,000 h−1. The strong interaction leads to the improvement of the acidity and the increase in the amount of active oxygen species (oxygen vacancy), which are responsible for the higher activity at low temperatures. The SCR reaction process over Cu0.2-Ce0.3-Zr0.5 was also examined using in-situ DRIFTS. The DRIFTS results indicate that abundant ionic NH4+ (Bronsted acid sites), coordinated NH3 on the Lewis acid sites, as well as highly active monodentate nitrate and bridging nitrate species were the key intermediates in the SCR reaction.
TL;DR: In this paper, the density functional theory (DFT) method was used to clarify the NO and NH3 adsorption abilities over the catalyst models of Fe2O3/TiO2{001} and Fe2 O3/NiO 2{101} for selective catalytic reduction of NO with NH3 (NH3-SCR).
Abstract: Anatase TiO2 nanosheets (TiO2-NS) and nanospindles (TiO2-NSP) have been successfully prepared with F– and glacial acetic acid as structure-directing agents, respectively. The Fe2O3/TiO2-NS and Fe2O3/TiO2-NSP nanocatalysts were prepared by a wet incipient impregnation method with a monolayer amount of Fe2O3. All the catalysts were employed for the selective catalytic reduction of NO with NH3 (NH3-SCR) in order to understand the morphology-dependent effects. It is interesting that the Fe2O3/TiO2-NS nanocatalyst exhibited better removal efficiency of NOx in the temperature range of 100–450 °C, which was attributed to more oxygen defects and active oxygen, acid sites, as well as adsorbed nitrate species based on Raman spectra, XPS, NH3-TPD, NO+O2-TPD, and in situ DRIFTS. The density functional theory (DFT) method was used to clarify the NO and NH3 adsorption abilities over the catalyst models of Fe2O3/TiO2{001} and Fe2O3/TiO2{101}. The results showed that the NH3 adsorption energy over the TiO2{001} (−2.00 eV...
TL;DR: A series of MnEuOx catalysts were prepared by the co-precipitation method and used for selective catalytic reduction of NOx with NH3.
Abstract: A series of MnEuOx catalysts were prepared by the co-precipitation method and used for selective catalytic reduction of NOx with NH3 It was found that the modification of MnOx catalyst by Eu with a Eu/Mn molar ratio of 01 could greatly enhance its SCR activity and broaden its operating temperature window, accompanied by good resistance to SO2 and H2O From the characterization results of N2 adsorption, XRD, XPS, H2-TPR, it could be concluded that the larger surface area resulted from the inhibited crystallization of MnOx, the enrichment of surface Mn4+ and chemisorbed oxygen, and the higher reducibility all made a contribution to the high SCR activity of MnEuOx-01 catalyst Furthermore, the results of in situ DRIFTS study revealed the NH3-SCR reactions over MnOx and MnEuOx-01 were mainly controlled by L-H mechanism ( 150 °C) respectively, and the contribution of E–R mechanism became more important with increasing reaction temperature The enhanced NO oxidation and NH3 adsorption should be mainly contribute to the distinguished SCR performance of MnEuOx catalyst in the lower temperature range ( 150 °C) respectively
TL;DR: In this paper, a sea urchin-like Ni nanoparticles embedded in N-doped carbon nanotubes (CNTs) supported on porous carbon (Ni@N-C) 3D materials derived from waste biomass were prepared via pyrolysis and employed as an environmentally friendly, easy available and cost-effective catalyst for removal of toxic pollutants.
Abstract: Novel “sea urchin”-like Ni nanoparticles embedded in N-doped carbon nanotubes (CNTs) supported on porous carbon (Ni@N-C) 3D materials derived from waste biomass were prepared via pyrolysis and employed as an environmentally friendly, easy available and cost-effective catalyst for removal of toxic pollutants. The characterizations indicated that Ni0 catalyzed the growth of intertwined CNTs on carbon layers, affording abundant porous structures and larger specific surface area. With the synergistic effect of embedded Ni0 nanoparticles, nitrogen doping, hierarchical micro-mesopores, and interconnected CNTs, Ni@N-C displayed a superior catalytic capability for the oxidation of organic pollutants using peroxymonosulfate as an oxidant, and catalytic reduction of toxic CrVI to nontoxic CrIII by formic acid as a reducing agent. It was found that pyrolysis temperatures affected the compositions, morphologies, and catalytic properties of Ni@N-C. Inactive oxidized N species have transformed to the highly active graphitic N, pyridinic-N, and Ni-O-N clusters, thereby improving the catalytic activity. Moreover, Ni@N-C maintained good physicochemical structure and stable activity even after several cycles of reactions. The simple synthetic strategies, 3D structure, and remarkable performance of Ni@N-C composites make them serve as alternative environmentally friendly catalysts for removal of pollutants.
Abstract: In this work, highly efficient Cux–Mn composite catalysts (0 ≤ x ≤ 020) were synthesized by an improved hydrothermal–citrate complex method and tested in the catalytic total oxidation of CO and the removal of NO by CO The influence of Cu on manganese oxide materials was characterized by several techniques, including FESEM, HRTEM, XRD, BET analysis, H2 TPR, O2 TPD, XPS, and DRIFTS Possible reaction mechanisms for the NO + CO model reaction and CO oxidation were also tentatively proposed The Cu-modified manganese oxide materials showed higher catalytic activity in CO oxidation and the selective catalytic reduction (SCR) of NO with CO than pure MnOx materials The improved catalytic activity in CO oxidation observed for the copper–manganese oxide catalyst was associated with a greater amount of adsorbed oxygen species and high lattice oxygen mobility due to the formation of a Cu15Mn15O4 spinel active phase (Cux2+–Mnx3+–[O(y–z)⊙z] species) Furthermore, in terms of the CO-SCR model reaction, the surface
TL;DR: In this paper, a comprehensive review of the synergistic mechanism between bi-metal or multi-metal oxides is presented, and several possible directions for further research are presented finally.
Abstract: Atmospheric pollutants of nitrogen oxides (NOx) can be reduced by selective catalytic reduction (SCR). SCR of NOx with ammonia (NH3) at low temperatures has attracted much interest for high nitric oxide (NO) conversion, and this method is dominated by catalysts. Manganese (Mn)-containing oxide catalysts exhibit high activity and selectivity for the unique redox property of manganese oxides (MnOx). The reaction mechanisms and deactivation processes are summarized in this review. SCR of NOx with NH3 follows both the Langmuir–Hinshelwood and the Eley–Rideal mechanisms, which also contribute to the nitrous oxide formation. Fast SCR has a higher reaction rate than standard SCR. Mn-containing catalysts could also be deactivated by sulfur oxides and water vapor. The deactivation process of sulfur dioxide can be classified into two categories: deposition of (NH4)2SO4 and sulfation of active sites. The deactivation caused by water vapor can be attributed to the competitive adsorption. The adsorption of water on catalysts' surface blocked the active sites, which are provided for the adsorption of NH3 and NO. Alkali, alkaline earth and heavy metal ions existing in fine fly ash can also damage the catalysts' acid sites. A notable improvement on performance was obtained when Mn-containing catalysts were doped with a transition metal, for these enhanced its adsorption capacity and oxidation ability. Furthermore, this review gives a comprehensive discussion of the synergistic mechanism between bi-metal or multi-metal oxides. Major conclusions and several possible directions for further research are presented finally.
TL;DR: In this article, a V 2 O 5 -decorated Mn-Fe/attapulgite (V@MnFe/ATP) with high SO 2 tolerance was used for selective catalytic reduction of NO by NH 3 (NH 3 -SCR).
TL;DR: In this paper, mesoporous TiO2 spheres supported MnCeW mixed oxide catalysts for selective catalytic reduction of NOx with NH3 were prepared by a wet impregnation method.
Abstract: In this work, mesoporous TiO2 spheres supported MnCeW mixed oxide catalysts (MnCeW/m-TiO2) for selective catalytic reduction of NOx with NH3 were prepared by a wet impregnation method. It is interesting that the MnCeW/m-TiO2 catalysts exhibited excellent SCR activity and N2 selectivity in a wide temperature range, even under the high gas hourly space velocity. From in situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTs) studies of desorption, it could be concluded that the addition of tungsten brought about more Bronsted acid sites and reduced the energy barrier of NOx species adsorbed on the surface. At high temperature range, there were still some Bronsted acid sites and NOx species including bidentate nitrate and nitro compounds in MnCeW/m-TiO2, therefore more intermediates could take part in the SCR reactions as well as better catalytic performance. Besides, the in situ DRIFTs of transient reactions indicated that the formed NH3 species and NOx species of MnCeW/m-TiO2 were more re...
TL;DR: [Ar2N3]Mo(N)(O-t-Bu) serves as a catalyst or precursor for the catalytic reduction of molecular nitrogen to ammonia in diethyl ether between -78 and 22 °C in a batchwise manner with CoCp*2 as the electron source and Ph2NH2OTf as the proton source.
Abstract: [Ar2N3]Mo(N)(O-t-Bu), which contains the conformationally rigid pyridine-based diamido ligand, [2,6-(ArNCH2)2NC5H3]2– (Ar = 2,6-diisopropylphenyl), can be prepared from H2[Ar2N3], butyllithium, and (t-BuO)3Mo(N). [Ar2N3]Mo(N)(O-t-Bu) serves as a catalyst or precursor for the catalytic reduction of molecular nitrogen to ammonia in diethyl ether between −78 and 22 °C in a batchwise manner with CoCp*2 as the electron source and Ph2NH2OTf as the proton source. Up to ∼10 equiv of ammonia can be formed per Mo with a maximum efficiency in electrons of ∼43%.
TL;DR: In this paper, a series of V-Ce(SO4)2/Ti catalysts for selective catalytic reduction (SCR) of NO with ammonia are prepared by impregnation method.
Abstract: A series of V-Ce(SO4)2/Ti catalysts for selective catalytic reduction (SCR) of NO with ammonia are prepared by impregnation method. Low temperature SCR activity and alkali resistance of the optimal V-0.5Ce(SO4)2/Ti sample are found to be better than on the commercial V-W/Ti catalyst. Also, V-0.5Ce(SO4)2/Ti shows an excellent durability in the presence of SO2 and H2O, indicating to have prospects for the industrial application. Based on catalysts characterization and in-situ DRIFTS studies, a higher proportion of surface active oxygen generated by the introduction of Ce and a much faster H2 reduction point out the improved redox properties of V-0.5Ce(SO4)2/Ti, which results in a stronger NO oxidative activation and is confirmed by a more abundant formation of surface NO+ and NO3− species. When exposed to SCR conditions where both NH3 and NO are present, this enhanced NO activation can produce more reactive nitrite and/or NO+ intermediates which then readily react with adsorbed NH3 and decompose to N2 and H2O, accounting for the improved SCR activity of V-0.5Ce(SO4)2/Ti at low temperatures. The addition of Ce(SO4)2 also provides abundant reactive acid sites and adsorbed NH3 species thus increase. Even after Na poisoning, adequate surface acidity and redox properties still remain. Furthermore, relatively higher contents of V-OH are preserved owing to the interaction between Na and O S O, acting as a protection for the active sites. These promotional effects contribute to the better alkali resistance of V-0.5Ce(SO4)2/Ti. Therefore, all the results suggest that V-0.5Ce(SO4)2/Ti is a promising candidate as a catalyst for NH3-SCR in coal-fired power plants, especially under high Na-content conditions.
TL;DR: In this article, a dicationic and rigid organic structure directing agent (OSDA) was used to fit within the large cavities of high-silica ERI and AFX zeolites and showed good activity for the selective catalytic reduction (SCR) of nitrogen oxide using ammonia.
Abstract: It has been possible to efficiently synthesize high-silica ERI and AFX zeolites with nano-sized primary crystallites (30–200 nm) This was achieved by using a dicationic and rigid organic structure directing agent (OSDA) that fits within the large cavities of these zeolites, and the use of FAU zeolites as initial Si- and Al-sources Cu- and Fe-based ERI and AFX materials were prepared following both post-synthetic cation exchange and direct synthesis methodologies, showing good activity for the selective catalytic reduction (SCR) of nitrogen oxide using ammonia Accelerated hydrothermal ageing of the zeolites at high temperature (ie 750 °C) shows the necessity of removing the alkali cations remaining in the zeolites to obtain stable materials Furthermore, the catalytic performance of the prepared Cu- and Fe-containing AFX catalysts, both before and after ageing treatment, approaches the catalytic activity of Cu- and Fe-CHA
TL;DR: In this paper, a real diesel engine installed with DOC and DPF was investigated under various operating conditions, and it was found that the Fe-zeolite and V2O5-WO3/TiO2 catalysts were noticeably affected by the NO2/NOx ratio and exhaust temperature.
TL;DR: In this article, a series of NixMn1−xTi10 (x = 0.0-0.5) catalysts were synthesized using a one-pot sol-gel method for selective catalytic reduction (SCR) of NO with NH3.
TL;DR: In this paper, a sub-micron Cu/SSZ-13, obtained by modifying an existing synthesis procedure, was shown to be an effective and stable catalyst for selective catalytic reduction of NO.
Abstract: For the first time, sub-micron Cu/SSZ-13, obtained by modifying an existing synthesis procedure, was shown to be an effective and stable catalyst for selective catalytic reduction of NO. Characterization of the materials with X-ray diffraction, N2-physisorption and 27Al MAS NMR shows that hydrothermal aging, which simulates SCR reaction conditions, is more destructive for smaller particles in a sodium form. After Cu exchange, however, the catalytic performance and hydrothermal stability for Cu/SSZ-13 is independent of the particle size. In particular, a clear positive correlation is found between remaining tetrahedral framework Al and isolated Cu-ion concentrations in aged Cu/SSZ-13 catalysts of comparable Al and Cu contents. This indicates that (1) isolated Cu-ion and paired framework Al configurations display remarkable hydrothermal stabilities; and (2) paired-Al contents can be varied via modifying the synthesis procedures, which appear to have a more critical influence on stabilizing isolated Cu-ions during harsh hydrothermal aging than the particle size. This study is of high interest for applications in vehicular DeNOx technologies where high loadings of active species on wash coats can be achieved by using sub-micron Cu/SSZ-13.
TL;DR: The critical review of the recent research progress for development of novel catalysts used for the reduction of 2-nitroaniline has been provided and different catalytic systems reported for reduction under various reaction conditions have been discussed.
Abstract: 2-nitroaniline (2-NA) is highly toxic and environmental contaminant. It is reduced to less toxic and environmental benign product o-phenylenediamine by using different reducing agents like sodium borohydride, potassium borohydride, or hydrazine hydrate in the presence of various catalytic systems. These catalytic systems have various advantages and drawbacks. Silica-supported gold nanoparticles are frequently reported catalyst for the reduction of 2-nitroaniline in aqueous medium. In this review article, different catalytic systems reported for reduction of o-nitroaniline under various reaction conditions have been discussed. The critical review of the recent research progress for development of novel catalysts used for the reduction of 2-nitroaniline has been provided here.
TL;DR: 3D nanoscale reconstructions of two Cu-containing zeolite catalysts are created, providing a complete picture of their deactivation mechanisms during aging, and identification of nanometer scale heterogeneities that lead to catalytic activity and material deactivation.
Abstract: Copper-exchanged zeolite chabazite (Cu-SSZ-13) was recently commercialized for the selective catalytic reduction of NO X with ammonia in vehicle emissions as it exhibits superior reaction performance and stability compared to all other catalysts, notably Cu-ZSM-5. Herein, the 3D distributions of Cu as well as framework elements (Al, O, Si) in both fresh and aged Cu-SSZ-13 and Cu-ZSM-5 are determined with nanometer resolution using atom probe tomography (APT), and correlated with catalytic activity and other characterizations. Both fresh catalysts contain a heterogeneous Cu distribution, which is only identified due to the single atom sensitivity of APT. After the industry standard 135,000 mile simulation, Cu-SSZ-13 shows Cu and Al clustering, whereas Cu-ZSM-5 is characterized by severe Cu and Al aggregation into a copper aluminate phase (CuAl2O4 spinel). The application of APT as a sensitive and local characterization method provides identification of nanometer scale heterogeneities that lead to catalytic activity and material deactivation.
TL;DR: In this article, the authors presented a complete catalytic mechanism describing both the Standard and the Fast selective catalytic reduction (SCR) reactions in their correct stoichiometric form on a vanadia titania (anatase 001 facet) based catalyst model.
TL;DR: In this paper, a noble metal-free copper nickel oxysulfide (CuNiOS) nanoparticles have been successfully fabricated by using a simple, cost-effective, and eco-friendly solution-based approach.
Abstract: In this study, novel and noble metal-free copper nickel oxysulfide (CuNiOS) nanoparticles have been successfully fabricated by using a simple, cost-effective, and eco-friendly solution-based approach, with copper oxysulfide (CuOS) as a comparative The CuOS and CuNiOS catalysts with various Ni contents were investigated by different techniques The catalytic activities of the samples were assessed by the catalytic reduction of organic dyes such as 4-nitrophenol (4-NP), methylene blue (MB), and rhodamine-B (RhB) together with NaBH4 in an aqueous solution The results obtained from ultraviolet-visible (UV-vis) spectroscopy indicated that CuNiOS-06 prepared with a Cu : Ni precursor mole ratio of 1 : 06 had the best catalytic performance for the reduction of 4-NP, MB, and RhB in comparison to the other CuNiOS catalysts and the monometallic catalyst (CuOS) due to synergistic effects In addition, the CuNiOS-06 catalyst is also better than other CuNiOS ones due to the presence of optimum amounts of Ni in the CuNiOS sample Thus, the present approach provides a promising way to fabricate different noble metal free bimetallic oxysulfide catalysts for extensive applications in catalysis and reduction/removal of other organic pollutants
TL;DR: Mn/Ce/Nb/Ti catalysts were synthesized using a precipitation method and their catalytic activities for NO selective reduction with NH 3 at low temperatures were evaluated as mentioned in this paper.
Abstract: Mn/Ce/Ti and Mn/Ce/Nb/Ti catalysts were synthesized using a precipitation method and their catalytic activities for NO selective reduction with NH 3 at low temperatures were evaluated. Nb doping not only improved the activity of the catalyst over a wide temperature range but also restricted the generation of NO 2 and N 2 O. The Mn/Ce/Nb/Ti catalyst displayed 100% NO conversion from 150 to 250 °C and >90% N 2 selectivity below 250 °C. The specific surface area of the catalyst was increased and its surface acidity was strengthened after Nb doping. Moreover, Nb doping increased the NO oxidation ability and lowered the NH 3 oxidation activity of the catalyst. All the above factors contributed to enhancing the overall NH 3 -SCR performance of the Mn/Ce/Nb/Ti catalyst compared with that of the Mn/Ce/Ti one. The long-term stability and resistance to H 2 O and SO 2 of the Mn/Ce/Nb/Ti catalyst were also evaluated.