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Preventing emission of pollutants in any kind, is a way to protect global environment. The objective of this study is to develop cobalt catalysts supported on alumina for the conversion of the toxic gas SO2 into elemental sulfur using methane. Although several useful catalysts have been proposed, there is still a need to synthesize a catalyst with a high sulfur yield that is also persistent during on-stream stability. To this end, four different catalysts were prepared using the wet impregnation technique, with Co3O4 content ranging from 0 to 15 wt%. Catalytic activity tests were carried out at atmospheric pressure and temperatures ranging from 550 to 800 °C. The Al2O3–Co (15 %) catalyst exhibited superior performance, with a sulfur yield of 98.1 % at 750 °C. The catalytic stability of the best catalyst was examined using a 20 h on-stream stability test under the optimized conditions including an SO2/CH4 molar feed ratio of 2 at 750 °C. The structural changes of the used catalyst after the stability test were investigated using XRD and TPO analyses. It was revealed that sulfidation of Co3O4 after a short while, results in decreasing the sulfur yield from 98.1 % to 89.8 %.

Presently, selective catalytic reduction (SCR), with either carbon monoxide, urea, hydrocarbons, hydrogen, or ammonia as a reductant, has become a nitrogen oxide (NOx) removal technology (NOx conversion) of many catalytic companies and diesel engine exhaust gas. Although, there exists a serious threat of low-temperature limitations. So far, certain scientists have shown that barium-based (Ba-based) catalysts have the potential to be highly effective at SCR of NOx at low temperatures when ammonia is used as the reducing agent. The process of NOx storage and reduction which alternate SCR is known as the Lean NOx trap. Herein, we give the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx, the advantages of BaO catalysts compared to the recently hot electrocatalysis, the stability of BaO catalyst materials, and the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx. These catalysts are viewed in the light of their preparation method, particulate, and posture in mixed oxides. Also, the characteristic features of Ba-based catalysts are carefully considered and briefed under the following areas: preparation method and precursor, crystallinity, calcination temperature, morphology, acid sites, the specific surface area for reaction, redox property, and activation energy of catalysts. More to these are the discussions on Eley–Rideal [E-R] and Langmuir–Hinshelwood [L–H] mechanisms, the H2O/SO2 and O2 permissiveness, and the NH3-SCR reaction mechanism over Ba-based catalysts highlighting their possible effects. Finally, we proposed the prospect and the likely future research plan for the low-temperature NH3-SCR of NOx. [ABSTRACT FROM AUTHOR]

Polyoxymethylene dimethyl ethers (OME) produced from methanol are considered as potential substitutes of Diesel fuel. Emissions of formaldehyde and other components have been observed, particularly under cold-start conditions in engine test-bench experiments with OME fuel. In this study, the reactivity of OME3 (CH3O(CH2O)3CH3) and its decomposition products was studied in the temperature range 80–450 °C in a model gas test bench over V2O5/WO3/TiO2 and Cu-CHA SCR catalysts, a platinum-coated V2O5/WO3/TiO2 ammonia slip catalyst (ASC) and two diesel oxidation catalysts (DOC), based on platinum and platinum-palladium. Already at 80 °C, OME3 was largely hydrolyzed to methanol and formaldehyde over all catalysts. At temperatures above 150 °C, V2O5/WO3/TiO2 oxidized methanol and formaldehyde to CO via formic acid as intermediate. The platinum ASC showed a similar behavior but oxidized the decomposition products to CO2. Whereas Cu-CHA hydrolyzed OME3 quantitatively to methanol and formaldehyde, it did not show oxidation activity in the studied temperature range. The data indicate that the release of significant amounts of OME from a catalytic converter can be virtually ruled out under cold start conditions, but also that low temperature hydrolysis produces formaldehyde and methanol emissions. [ABSTRACT FROM AUTHOR]

Microwave-assisted selective catalytic reduction of nitrogen oxides (NOx) was investigated over Ni-based metal oxides. The NiMn2O4 and NiCo2O4 catalysts were synthesized by the co-precipitation method and their activities were evaluated as potential candidate catalysts for low-temperature NH3-SCR in a microwave field. The physicochemical properties and structures of the catalysts were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), N2-physisorption, NO adsorption-desorption in the microwave field, H2-temperature programmed reduction (H2-TPR) and NH3-temperature programmed desorption (NH3-TPD). The results verified that microwave radiation reduced the reaction temperature required for NH3-SCR compared to conventional heating, which needed less energy. For the NiMn2O4 catalyst, the catalytic efficiency exceeded 90% at 70 °C and reached 96.8% at 110 °C in the microwave field. Meanwhile, the NiMn2O4 also exhibited excellent low-temperature NH3-SCR reaction performance under conventional heating conditions, which is due to the high BET specific surface area, more suitable redox property, good NO adsorption-desorption in the microwave field and rich acidic sites. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) is diesel aftertreatment using a reduction agent to reduce nitrogen oxides. Diesel engine regulations are being tightened; therefore, the diesel aftertreatment system should be operated efficiently. In the urea-SCR system, there is a possibility of various faults, e.g., catalyst deactivation by sulfur or hydrothermal aging and fault in urea injection system. These faults interfere with normal system operation and result in increase of NOx concentration at the tailpipe. To prevent this situation, it is necessary to detect system faults. In this study, a first-principle model for SCR system is presented based on mass and energy balance equations. Using the one-dimensional urea-SCR model, this research introduces a model-based fault detecting strategy for SCR system. The residuals are calculated as the difference between the model calculation and the actual catalyst system measurement with the system faults. The results of this research are used in fault diagnosis and fault tolerant control studies to meet diesel vehicle nitrogen oxide regulations even in the presence of catalyst faults. [ABSTRACT FROM AUTHOR]

Using sintering dust as a raw material, selective catalytic reduction (SCR) catalysts were pretreated with water and acid washing (HF, HCl, HNO3 and H2SO4) and then modified by different metal oxides (Ce, Cu, Eu, Nd and Mn) with an impregnation method. Based on this, the catalyst was supported by ZrO2, Al2O3 and TiO2. The catalysts were ascertained by various characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption analysis. The results showed that the main component of sintering dust was iron oxide (> 50 wt%), which is a feasible material for fabricating SCR catalysts. The catalysts pretreated by HF and modified by CeO2 improve the denitration efficiency. When modified with 10 wt% CeO2, the Ce10-PSDCHF catalyst sample exhibited the best NOx conversion rate, reaching 76.4% at 280 °C. The catalyst modified by ZrO2 was dispersed well and had best denitration efficiency. The denitration efficiency of SCR increased with the increase in ZrO2 loading and the NOx conversion rate of 0.25-Ce10-PSDCHF/ZrO2 catalyst reached 85% at 280 °C. The modification and support of metal oxides improve the denitration efficiency, which makes the sintering dust have promising industrial application prospects. This work would be timely technical guidance and valuable insights for the application of sintering dust. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) system is considered to be the most effective control method for reducing NOx in exhaust gas post-treatment of the diesel engine. Catalysts are the main factors affecting de-NOx efficiency in SCR reactions. In recent years, due to the excellent characteristics of copper zeolite catalysts, they have been widely studied as low-temperature NH3-SCR catalysts. However, the development of low-temperature SCR catalysts with high removal efficiency still faces severe challenges. This paper reviewed the latest research progress with copper zeolite catalysts at low temperature and compared the action mechanism of various copper zeolite catalysts in NH3-SCR reactions. Copper zeolite catalysts were studied from the aspects of catalytic performance, preparation strategy, broadening the operating temperature window, hydrothermal deactivation and resistance to H2O and SO2. Several solutions to the problems existing in low-temperature NH3-SCR reactions were discussed. In addition, this paper also puts forward some views on the future research direction of copper zeolite catalysts. Finally, the summaries and prospects of the development of low-temperature SCR copper zeolite catalysts were presented. Hopefully, more researchers can understand the current research status of copper zeolite catalysts and obtain better research achievements from copper zeolite catalysts in the future. This review could pave the way for similar studies to enable a wider variety of copper zeolite catalysts to be commercially available. [ABSTRACT FROM AUTHOR]

Chlorine species, widely presented in industrial flue gas such as the waste incineration plants, can poison the catalysts and affect the selective catalytic reduction (SCR) performance. In this work, effects of Cl on the SCR performance of V2O5–WO3/TiO2 (VW/Ti) catalysts were investigated by NH4Cl deposition. The results showed that the NOx conversion efficiency at low reaction temperature (< 300 °C) decreased with the loading of NH4Cl after calcination. It was found that instead of causing the chlorination of VW/Ti catalyst the NH4Cl decomposed into volatile Cl species due to the weak V–Cl bonding. Such decomposition reduced significantly the surface non-lattice oxygen species to inhibit NO adsorption and activation, but hardly affected the redox ability and acidity of VW/Ti catalyst. Time–resolved in situ DRIFTs results indicated that NH3 activation and the SCR process predominated by Eley–Rideal mechanism were not influenced with NH4Cl impregnation, while the SCR at low temperature following a Langmuir–Hinshelwood path was limited by the decreased and weaker binding sites for NO activation. [ABSTRACT FROM AUTHOR]

Chlorine species, widely presented in industrial flue gas such as the waste incineration plants, can poison the catalysts and affect the selective catalytic reduction (SCR) performance. In this work, effects of Cl on the SCR performance of V2O5–WO3/TiO2 (VW/Ti) catalysts were investigated by NH4Cl deposition. The results showed that the NOx conversion efficiency at low reaction temperature (< 300 °C) decreased with the loading of NH4Cl after calcination. It was found that instead of causing the chlorination of VW/Ti catalyst the NH4Cl decomposed into volatile Cl species due to the weak V–Cl bonding. Such decomposition reduced significantly the surface non-lattice oxygen species to inhibit NO adsorption and activation, but hardly affected the redox ability and acidity of VW/Ti catalyst. Time–resolved in situ DRIFTs results indicated that NH3 activation and the SCR process predominated by Eley–Rideal mechanism were not influenced with NH4Cl impregnation, while the SCR at low temperature following a Langmuir–Hinshelwood path was limited by the decreased and weaker binding sites for NO activation. [ABSTRACT FROM AUTHOR]

The International Maritime Organization has set forth strict regulations about the NOx emission limit of ships to address the pollution problem in the transportation sector. Selective catalytic reduction (SCR) is the most effective post-engine means to reduce emission, and the control of urea spray critically affects the SCR performance. This paper developed a predictive control strategy of the SCR system based on the state space model. Specifically, the block model of the SCR reactor was established based on the reaction mechanism of the SCR system, and the unknown model parameters were identified. Rapid prototyping of the SCR system was carried out using the dSPACE real-time simulation platform to optimize the control under steady-state conditions. The catalyst ammonia coverage was set as the control target to maximize the NOx conversion rate while maintaining the NH3 escape at the outlet less than 10 ppm. The cyclic test results showed that the control strategy can quickly respond to external disturbance and modify the control target to keep the ammonia coverage rate within the target range, to thus achieve high NOx conversion rate while maintaining the required ammonia escape. [ABSTRACT FROM AUTHOR]

The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study.

Activated red mud (RM) has been proved to be a promising base material for the selective catalysis reduction (SCR) of NOx. The inherent low reducibility and acidity limited its low–temperature activity. In this work, molybdenum oxide, tungsten oxide, and cerium oxide were used to reconfigure the redox sites and acid sites of red mud based catalyst. When activated red mud was reconfigured by cerium-tungsten oxide (Ce–W@RM), the NOx conversion kept above 90% at 219–480 °C. The existence of Ce3+/Ce4+ redox electron pairs provided more surface adsorbed oxygen (Oα) and served as a redox cycle. Positive interactions between Ce, W species and Fe oxide in red mud occurred, which led to the formation of unsaturated chemical bond and promoted the activation of adsorbed NH3 species. WO3 and Ce2(WO4)3 (formed by solid–state reaction between Ce and W species) could provide more Brønsted acid sites (W–O modes of WO3, WO or W–O–W modes of Ce2(WO4)3). CeO2 species could provide more Lewis acid sites. The Langmuir–Hinshelwood (L-H) routes and Eley-Rideal (E-R) routes occurred in the low-temperature SCR reaction on the Ce–W@RM surface. NH4+ species on Brønsted acid sites, NH3 species on Lewis acid sites, bidentate nitrate and bridging nitrate species were key active intermediates species.

Abstract Vanadium-based catalysts have been used for several decades in ammonia-based selective catalytic reduction (NH3-SCR) processes for reducing NO x emissions from various stationary sources (power plants, chemical plants, incinerators, steel mills, etc.) and mobile sources (large ships, automobiles, etc.). Vanadium-based catalysts containing various vanadium species have a high NO x reduction efficiency at temperatures of 350–400 °C, even if the vanadium species are added in small amounts. However, the strengthening of NO x emission regulations has necessitated the development of catalysts with higher NO x reduction efficiencies. Furthermore, there are several different requirements for the catalysts depending on the target industry and application. In general, the composition of SCR catalyst is determined by the components of the fuel and flue gas for a particular application. It is necessary to optimize the catalyst with regard to the reaction temperature, thermal and chemical durability, shape, and other relevant factors. This review comprehensively analyzes the properties that are required for SCR catalysts in different industries and the development strategies of high-performance and low-temperature vanadium-based catalysts. To analyze the recent research trends, the catalysts employed in power plants, incinerators, as well as cement and steel industries, that emit the highest amount of nitrogen oxides, are presented in detail along with their limitations. The recent developments in catalyst composition, structure, dispersion, and side reaction suppression technology to develop a high-efficiency catalyst are also summarized. As the composition of the vanadium-based catalyst depends mostly on the usage in stationary sources, various promoters and supports that improve the catalyst activity and suppress side reactions, along with the studies on the oxidation state of vanadium, are presented. Furthermore, the research trends related to the nano-dispersion of catalytically active materials using various supports, and controlling the side reactions using the structure of shaped catalysts are summarized. The review concludes with a discussion of the development direction and future prospects for high-efficiency SCR catalysts in different industrial fields.

The combination of diesel oxidation catalyst (DOC), catalyzed diesel particulate filter (CDPF) and selective catalytic reduction (SCR) is the most effective way to reduce particulate emission and nitrogen oxide (NOx) from diesel engines. In this study, the effects of a DOC+CDPF+SCR system on the emissions including carbon monoxide (CO) total hydrocarbon (THC), NOx, particle number (PN) and particle mass (PM) from a heavy-duty diesel engine were evaluated. In addition, the influences of ammonia (NH3) slip catalyst (ASC) coating and SCR catalyst downsizing on the NOx conversion efficiency, nitrous oxide (N2O) emissions and NH3 slip were also investigated. Results showed that the installation of the after-treatment system had negligible effect on the power and BSFC of the engine. The upstream DOC reduced by an average of 97.0% of the CO and 67.5% of the THC, in combination with CDPF, the CO and THC emission further decreased with an average drop of 97.8% and 72.5%, respectively. In terms of particulate emissions, the single DOC reduced 48.0% of the PN and 50.9% of the PM, and the combination of DOC and CDPF led to a reduction of 98.0% in the PN and 96.9% in the PM on average. The SCR was effective in reducing NOx emission, but resulted in higher N2O emission by more than 3 times, meanwhile led to an average NH3 slip of 3.80 ppm. Downsizing the SCR length by 1/3 could still ensure a 91.9% conversion efficiency of NOx, and produced less N2O, but led to an increase of the NH3 slip by 2 times, reaching 7.63 ppm on average. By coating Pt-based ASC catalyst on the back end of the SCR could eliminate the NH3 slip. Considering the cost and performance, the combination of DOC, CDPF and a downsized SCR with ASC coating may be a better choice.

Selective catalytic reduction (SCR) has been one of the most efficient and widely used technologies to remove nitrogen oxides (NOx). SCR research has developed rapidly in recent years, which can be reflected by the dramatic increase of related academic publications. Herein, based on the 10,627 documents from 2001 to 2020 in Web of Science, the global research landscape and hotspots in SCR are investigated based on a comprehensive bibliometric analysis. The results show that SCR research has developed positively; the annul number of articles increase sharply from 246 in 2001 to 1092 in 2020. People's Republic of China and Chinese Academy of Sciences are the most productive country and institution, respectively. The global collaboration is extensive and frequent, while People's Republic of China and USA have the most frequent research cooperation. Applied Catalysis B-Environmental is the leading publication source with 711 records. Five major research areas on SCR are identified and elaborated, including catalyst, reductant, deactivation, mechanism, and others. Zeolite is the most widely studied SCR catalyst, while copper, silver, platinum, and iron are the most popular metal elements in catalyst. Ammonia (NH3) is dominated among various SCR reductants, while hydrocarbon reductant has gained more attention. Sulfur dioxide (SO2) and vapor are the two most concerned factors leading to catalyst deactivation, and catalyst regeneration is also an important research topic. Density functional theory (DFT), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and kinetics are the most widely used methods to conduct mechanism study. The studies on "low temperature," "atomic-scale insight," "elemental mercury," "situ DIRFTS investigation," "arsenic poisoning," "SPOA-34," "Cu-CHA catalyst," "TiO2 catalyst," and "Ce catalyst" have been the hotspots in recent years. [ABSTRACT FROM AUTHOR]

The power generation sector is considered one of the major contributors to nitrogen oxides (NOx) emissions which have serious impacts on air quality. An optimization model is developed to help decision‐makers determine the best strategy or mix of strategies for the electricity sector to meet a given NOx reduction target and electricity demand at a minimum cost. The model recommended the selective catalytic reduction (SCR) technology to be applied at higher NOx emissions and the reduction reached up to 80 %. This potential option provides promising prospects for NOx emissions control, which is in line with the economic demand for sustainable energy and environmentally friendly technologies. [ABSTRACT FROM AUTHOR]

Different spinel composite oxide catalysts, LiMn2O4, ZnMn2O4 and CrMn2O4 are prepared and activities of the catalysts for selective catalytic reduction of NOx by NH3 (NH3-SCR) are tested at 50~450 ℃. The effects of catalyst structure, metal elements and valence states on NH3-SCR activity are investigated. The catalysts are characterized by physical adsorption instrument (BET), X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR), etc. The structure-activity relationship of spinel catalyst is also studied. The results show that： The LiMn2O4 spinel catalyst has the best activity with more than 90% NO conversion at the space velocity of 6×104 mL/(g∙h) at 150 ℃, and it shows more than 80% NO conversion at 100~400 ℃, demonstrating good low temperature activity and wide temperature range. However, the denitrification activity of ZnMn2O4 and CrMn2O4 is relative poor, and the two have similar activities. In the presence of water, the activity of LiMn2O4 decreased greatly, while the activities of ZnMn2O4 and CrMn2O4 decreases slightly, showing better water resistance. The conversion rate of ZnMn2O4 reach 90% at 150 ℃, which is better than that of CrMn2O4 in the presence of water. Spinel ZnMn2O4 has a good NO conversion rate in a wide temperature range and strong water resistance. [ABSTRACT FROM AUTHOR]

Novel yttrium-doped CeO2, MnOx, and CeMnOx composites are investigated as catalysts for low-temperature NH3-SCR. The study involves the preparation of unmodified oxide supports using a citrate method followed by modification with Y (2 wt.%) using two approaches, including the one-pot citrate method and incipient wetness impregnation of undoped oxides. The NH3-SCR reaction is studied in a fixed-bed quartz reactor to test the ability of the prepared catalysts in NO reduction. The gas reaction mixture consists of 800 ppm NO, 800 ppm NH3, 10 vol.% O2, and He as a balance gas at a WHSV of 25,000 mL g−1 h−1. The results indicate that undoped CeMnOx mixed oxide exhibits significantly higher deNOx performance compared with undoped and Y-doped MnOx and CeO2 catalysts. Indeed, yttrium presence in CeMnOx promotes the competitive NH3-SCO reaction, reducing the amount of NH3 available for NO reduction and lowering the catalyst activity. Furthermore, the physical-chemical properties of the prepared catalysts are studied using nitrogen adsorption/desorption, XRD, Raman spectroscopy, temperature-programmed reduction with hydrogen, and temperature-programmed desorption of ammonia. This study presents a promising approach to enhancing the performance of NH3-SCR catalysts at low temperatures that can have significant implications for reducing NO emissions. [ABSTRACT FROM AUTHOR]

The utilization of catalytic converters is one of the well-known strategies to clean the exhaust. The catalytic converters oxidize the destructive carbon monoxide and hydrocarbon emissions into harmless CO2 and water vapor. In this experiment, the essential objective is to develop a catalytic converter with combined methods like selective catalytic reduction, NOx storage and reduction (SCR-NSR) procedure and test its effectiveness in the NOx reduction from the exhaust of diesel engine. The combination of the SCR-NSR catalytic systems is proposed in this experimentation for building up an effective catalytic converter and distinguishing the optimal emission processes. The fabricated SCR-NSR catalytic converter is fitted to the exhaust system and the emission rates are estimated with the help of a gas analyzer. The testing is done by utilizing diesel as fuel in the Kirloskar TV1 engine with NSR, non-filter, and combined NSR–SCR system. The investigation is experienced for 20 trials with different emission parameters analyzed. For improving the discharge level in the engine, the test data are predicted with the proposed numerical model and tested in Mat Lab software. The invasive weed optimization and particle swarm optimization together with a recurrent neural network are utilized for the prediction and optimization process and parameters like compression ratio, input power, and load are utilized as input to the experimentation. In the 20 trials, a low level of discharge is attained in the 17th trial. Subsequently, the prediction goes for the 20 sets individually and compared with the 17th set and the experimental results demonstrate that the discharge rates acquired for consolidated NSR–SCR were observed to be 0.01% of CO, 3% of HC, 0.1% of CO2, 20.74% of O2, and 68 ppm of NOx. The point when compared to predicted outcomes demonstrates the ideal level of 0.001% of CO, 0.5% of HC, 0% of CO2, 21.76% of O2, and 60.6 ppm of NOx, respectively. The proposed invasive weed optimization and particle swarm optimization obviously reduce the emission rates of diesel engines more than the other comparative methods. [ABSTRACT FROM AUTHOR]

Based on the unique technique property of grate–kiln pellet production process and its demand of ultra-low emission of NOx, a low energy-consumed embedded selective catalytic reduction (SCR) denitration technology was proposed. The temperature of the NOx-containing tributary flue gas was 350–500 °C, which basically accorded with the temperature range of SCR by V2O5-based catalyst. Considering the potential inhibition effect of high SO2 concentration (8000–10000 mg/m3) and metal-containing dust in the pelletizing flue gas, the catalyst compositions were optimized to V2O5 (0.5%) and WO3 (5%), giving NO conversion over 90% with low yield of N2O by-product. Compared with the low-medium temperature SCR technology, it was no longer necessary to reheat the flue gas, showing a remarkable CO2 emission reduction effect. The CO2 emission reduction ratios were 94% and 66% contributed by the decrease of fuel and electricity consumption for the embedded SCR technology, respectively. The operating cost was also greatly reduced from 11.4 CNY/t-pellet to 3.1 CNY/t-pellet (Chinese Yuan). [ABSTRACT FROM AUTHOR]

Molecular sieve catalysts containing transition metals have been attracting attention for their potential applications in various fields, including environmental and industrial catalysis. A Cu-Ce-Zr/SAPO-34 series of molecular sieve catalysts were prepared by the impregnation method, and the effect of Zr introduction on the selective catalytic reduction of NO by Cu-Ce/SAPO-34 molecular sieve catalysts was explored. Through various characterization methods, the physical and chemical properties of the catalysts were analyzed, and the denitration mechanism of the molecular sieve catalyst was discussed. This study found that the total acid content of the acid sites on the catalyst surface decreased with the introduction of Zr, leading to a decrease in the denitration efficiency of the catalyst. At 350–400 °C, the denitration efficiency of the 4Cu-4Ce-4Zr/SAPO-34 catalyst was over 80%, and at 400–500 °C, it was over 99%. Moreover, excessive metal Zr could destroy its CHA structure and decrease the denitration efficiency of the catalyst. This study analyzed the reaction mechanism of NH3-SCR of Zr-modified polymetallic zeolites and the effect of Zr modification on the NH3-SCR reaction results. This study contributes to the understanding of the performance of molecular sieve catalysts containing transition metals. Reliable conclusions were obtained, which offer data support for future research in the field of NH3-SCR. [ABSTRACT FROM AUTHOR]

The following research presents a numerical evaluation of existing and conceptual urea-mixing devices used in close-coupled (to the engine) selective catalytic reduction (SCR) systems. The analysis was aimed at the assessment of urea-mixing devices that could considerably enhance the reduction of nitrogen oxides from the diesel-engine combustion process under a wide range of operating conditions, including cold starts. The analysis showed that replacing blade-equipped static mixers with perforated stationary mixing devices may provide a more uniform spatial distribution of ammonia at the inlet to the SCR catalyst and reduce pressure drops generated by mixing devices. Moreover, the conceptual mixing devices, based on combinations of the blade and perforated mixers to develop intensive turbulence, enabled the increase of the mixing length leading to effective decomposition of the urea-water solution (UWS), and provided uniform spatial distribution of ammonia, even for the small-sized mixing systems. However, the intensive mixing was often associated with a significant rise in the pressure drop. [ABSTRACT FROM AUTHOR]

Objective: In order to control NOx in low‐temperature flue gases emitted from non‐power industries and to reduce the preparation cost of denitration catalysts, this study uses inexpensive blast furnace slag as raw material to prepare denitration catalysts. Methods: After cooling, drying and grinding, the blast furnace slag becomes a powder with considerable fineness and meets the requirements of activity index, which is called GGBS (ground granulated blast furnace slag). Using GGBS as denitration catalyst carrier, the active components M (M = Fe, Co, Ni, Cu and Ce) are loaded on Mn‐based GGBS catalyst using an impregnation method. Conclusions: The effect of different active components on the denitration performance and sulfur resistance of Mn‐based GGBS catalysts is investigated. The results show that the Mn‐Ce/GGBS catalyst has better denitration performance and sulfur resistance. The Mn‐Ce/GGBS catalyst has a significant denitration performance when load ratio is 2:1. The active component Ce improves the denitration performance of the catalyst, reduces sulfur poisoning and extends the life of the catalyst. The SO2 in the flue gas increases the acid sites on the catalyst surface and improves catalyst activity. The larger the ratios of Mn4+/Mn3+, Ce4+/Ce3+ and Oα/Oβ, the stronger the catalyst activity and the better the denitration performance. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

This work aims to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3. A series of SmxMn0.3−xTi catalysts (x = 0, 0.1, 0.15, 0.2, and 0.3) were prepared by co-precipitation. Activity tests indicated that the Sm0.15Mn0.15Ti catalyst showed superior performances, with a NO conversion of 100% and N2 selectivity above 87% at 180–300°C. The characterizations showed that Sm doping suppressed the crystallization of TiO2 and Mn2O3 phases and increased the specific surface area and acidity. In particular, the surface area increased from 152.2 m2·g−1 for Mn0.3Ti to 241.7 m2°g−1 for Sm0.15Mn0.15Ti. These effects contributed to the high catalytic activity. The X-ray photoelectron spectroscopy (XPS) results indicated that the relative atomic ratios of Sm3+/Sm and Oβ/O of Sm0.15Mn0.15Ti were 76.77at% and 44.11at%, respectively. The presence of Sm contributed to an increase in surface-absorbed oxygen (Oβ) and a decrease in Mn4+ surface concentration, which improved the catalytic activity. In the results of hydrogen temperature-programmed reduction (H2-TPR), the presence of Sm induced a higher reduction temperature and lower H2 consumption (0.3 mmol·g−1) for the Sm0.15Mn0.15Ti catalyst compared to the Mn0.3Ti catalyst. The decrease in Mn4+ weakened the redox property of the catalysts and increased the N2 selectivity by suppressing N2O formation from NH3 oxidation and the nonselective catalytic reduction reaction. The in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) revealed that NH3-SCR of NO over the Sm0.15Mn0.15Ti catalyst mainly followed the Eley—Rideal mechanism. Sm doping increased surface-absorbed oxygen and weakened the redox property to improve the NO conversion and N2 selectivity of the Sm0.15Mn0.15Ti catalyst. [ABSTRACT FROM AUTHOR]

Numerical analysis and experimental studies were conducted to evaluate the performance of a selective catalytic reduction (SCR) system according to the load of a 1.5-ton marine boiler. There are post-treatment methods for reducing the exhaust gas emitted from ships, such as low-sulfur oil, scrubber, a desulfurization device to remove sulfur oxides (SOx) and particulate matter, an exhaust gas recirculation system, and SCR agents to reduce nitrogen oxides (NOx). Furthermore, there are methods of using eco-friendly natural gas fuels, such as liquefied natural gas (LNG), methanol, liquefied petroleum gas, and ammonia. In the case of LNG, SOx and particulate matter are hardly emitted, and only a small amount of NOx is emitted compared to an internal combustion engine. Therefore, SCR system technology that can remove NOx needs to be applied. As a result of this study, the boiler load increased, and the flow velocity through the outlet decreased. In addition, the NOx emissions of diesel fuel and LNG fuel were reduced by 100% to 0 ppm when the boiler load ratio was 50%. When the load ratio was 75%, the NOx emissions of diesel fuel were reduced by 77.4% to 40 ppm, and those of LNG fuel were reduced by 64.1% to 24 ppm. When the load ratio was 100%, the NOx emissions of diesel fuel were reduced by 66.1% to 60 ppm, and those of LNG fuel were reduced by 47.8% to 24 ppm. In addition, the results of the numerical analysis according to boiler load were almost identical to the experimental results. Finally, this study could design an optimal SCR system through numerical analysis, according to the important parameters of the SCR system. [ABSTRACT FROM AUTHOR]

γ-Fe2O3 is considered to be a promising catalyst for the selective catalytic reduction (SCR) of nitrogen oxide (NOx). In this study, first-principle calculations based on the density function theory (DFT) were utilized to explore the adsorption mechanism of NH3, NO, and other molecules on γ-Fe2O3, which is identified as a crucial step in the SCR process to eliminate NOx from coal-fired flue gas. The adsorption characteristics of reactants (NH3 and NOx) and products (N2 and H2O) at different active sites of the γ-Fe2O3 (111) surface were investigated. The results show that the NH3 was preferably adsorbed on the octahedral Fe site, with the N atom bonding to the octahedral Fe site. Both octahedral and tetrahedral Fe atoms were likely involved in bonding with the N and O atoms during the NO adsorption. The NO tended to be adsorbed on the tetrahedral Fe site though the combination of the N atom and the Fe site. Meanwhile, the simultaneous bonding of N and O atoms with surface sites made the adsorption more stable than that of single atom bonding. The γ-Fe2O3 (111) surface exhibited a low adsorption energy for N2 and H2O, suggesting that they could be adsorbed onto the surface but were readily desorbed, thus facilitating the SCR reaction. This work is conducive to reveal the reaction mechanism of SCR on γ-Fe2O3 and contributes to the development of low-temperature iron-based SCR catalysts. [ABSTRACT FROM AUTHOR]

The thermal analysis kinetic method was employed to solve the activation energies of the thermal decomposition reactions of urea and cyanuric acid, with the purpose of understanding the formation of deposits in the diesel engine SCR system. The deposit reaction kinetic model was established by optimizing the reaction paths and reaction kinetic parameters based on the thermal analysis test data of the key components in the deposit. The result shows that the established deposit reaction kinetic model can accurately describe the decomposition process of the key components in the deposit. Compared to the Ebrahimian model, the simulation precision of the established deposit reaction kinetic model is significantly improved above 600 K. The activation energies of the urea and cyanuric acid decomposition reactions are 84 kJ/mol and 152 kJ/mol, respectively, after model parameters identification. The identified activation energies were closest to those of the Friedman one-interval method indicating that the Friedman one-interval method is reasonable to solve the activation energies of deposit reactions. [ABSTRACT FROM AUTHOR]

The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study. [ABSTRACT FROM AUTHOR]

Measurements and modeling studies were conducted on the evaporation and decomposition rates of urea adsorbed on a SCR catalyst using a lab-scale atmospheric pressure flow reactor system. For the evaporation behavior, an equilibrium concentration equation for urea in the vapor phase was derived. For the decomposition behavior, a first-order decomposition rate constant equation for the adsorbed urea was obtained. Using these experimental equations, an evaporation/decomposition model for urea based on the BET adsorption equation has been developed. [ABSTRACT FROM AUTHOR]

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Though NOx emissions from on-road heavy duty vehicles (HDVs) have reduced drastically over the past three decades, upcoming North American regulations may call for further reductions. Lowering NOx emissions below current levels is challenging, especially at lower operating loads such as idling and/or colder climates when the exhaust gas temperature is insufficient for high NOx conversion in the HDV's exhaust after treatment (EAT) system. This paper investigates the impact of various engine operating parameters on the three-way trade-off between NOx emissions, exhaust temperature, and fuel consumption using a single-cylinder, heavy-duty diesel engine outfitted with a conventional EAT system and diesel exhaust fluid (DEF) injection. The engine parameters investigated include exhaust gas recirculation (EGR) ratio, intake pressure, intake temperature, injection pressure, multiple injections, and engine fluid temperatures. In order to simulate cold climate operation, the baseline intake air, coolant, and lubricating oil temperatures are maintained at 10°C, 40°C, and 50°C, respectively. Results show that using a moderate level of EGR has the dual benefit of reducing the engine-out NOx and increasing the intake charge temperature. Increasing the intake or injection pressure does not result in significant benefit in improving the three-way trade-off. However, using double injection with the second injection at the start of the expansion stroke can help reduce NOx emissions and increase exhaust temperature with marginal impact on fuel efficiency. Based on the parametric study, three particular engine operating conditions are chosen for further investigation with the EAT online. At an identical DEF dosing rate, the rates of NOx reduction in the SCR are similar for the three conditions (∼96%), and the lowest tail-pipe NOx observed for this study is 0.032 g/kWh. [ABSTRACT FROM AUTHOR]

With the increasing awareness of global marine environmental protection, the emission of ship exhaust pollutants is strictly restricted. Selective catalytic reduction (SCR) technology is the mainstream technology to reduce ship NOx emission and make it meet IMO tier III regulations. A SCR reaction kinetic model based on Modelica language was established by Dymola software to predict the denitration efficiency, ammonia slip rate, and other parameters of SCR system. According to the functional structure of marine SCR system, the SCR system model is divided into urea injection module, mixer module, and SCR reactor module. The model was verified by SCR system bench test of WD10 diesel engine, which proved that the model can preferably reflect the actual situation. Using the established model, the effects of temperature, flow rate, NH3/NOx Stoichiometric Ratio (NSR), and cell density on the denitration performance of SCR system were analyzed. The results showed that the exhaust gas temperature and NSR have a great influence on the denitration efficiency. The injection amount of urea solution in marine SCR system should be based on the exhaust gas temperature and exhaust flow rate. [ABSTRACT FROM AUTHOR]

This paper deals with the possibility of improving the urea dosage control for the Selective Catalytic Reduction Systems (SCR) of an Euro VI d diesel light commercial vehicle in order to increase N O x after-treatment reduction performance. To this aim, first, we assess the effective emissions abatement performance for the appraised diesel vehicle via real-world experimental campaign, carried out according to the Real Driving Emissions (RDE) tests on urban, extra-urban and motorway road sections in Naples, Italy. Based on these real-world data, we derive a parameterized control-oriented model for the SCR system which is, then, exploited for the designing of an alternative urea injection logic which could be able to maximize the N O x reduction efficiency while minimizing tailpipe ammonia slip. Specifically, the optimal AdBlue injection rate is designed according to a Nonlinear Model Predictive Control Approach which allows obtaining a proper trade-off between the N O x abatement and the urea overdosing problem. The effectiveness of the proposed controller is evaluated by comparing the performance assessed for the appraised SCR system during the experimental tests with the ones achievable if the Euro VI diesel would be equipped with the proposed control strategy. Numerical simulation discloses the effectiveness of the NMPC controller in ensuring improved N O x reduction with performance complying with the emissions norms, main in avoiding excessive ammonia slip and in guaranteeing a reduced feed ratio w.r.t. to the standard industrial SCR controller mounted on the vehicle. [ABSTRACT FROM AUTHOR]

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Alkali metals bring great challenges to the elimination of NOx from stationary emissions in the selective catalytic reduction (SCR) reaction. The FeCu catalyst, as an eco-friendly and high-efficiency catalyst for NOx removal possesses wide application prospects. However, the poisoning effect of potassium is not clear. Therefore, the potassium poisoning catalyst was obtained by the wet impregnation means. The XRD, H2-TPR, NH3-TPD, XPS and DRIFT technologies were performed to study the influence of K poisoning. The results indicate that potassium causes damage to Cu-O-Fe construction. Then the Cu2+ in lattice of Fe2O3 separate out from Fe2O3 and form CuO which leads to the decline of acid sites and excessive NH3 oxidation. And it finally leads to the catalyst deactivation. After K poisoning, NO2, monodentate nitrates and nitrites cannot generate. Only bidentate nitrates can generate and then react with NH3 species on the Lewis acid sites to produce H2O and N2. Hence, the reaction rate has a slide.

Cu-CHA zeolites have proven to be effective for NOx reduction, but a drawback in using CHA zeolites is the cost associated with using expensive organic structure-directing agents. To overcome this drawback, we are reporting here the synthesis of Cu-CHA zeolite catalysts in both their NH4-form as well as K-form that do not require the use of organic structure-directing agents. After comprehensive characterization by XRF, XRD, 27Al NMR spectroscopy, FE-SEM, SEM/EDS, N2-adsorption/desorption, NH3-TPD, H2-TPR, and XPS, the zeolite catalysts were tested for NOx conversion by NH3-selective catalytic reduction (NH3-SCR). Cu-NH4-CHA zeolite catalysts exhibited remarkable activity and thermal stability over a wide temperature window, outperforming their counterpart K-forms. Among the NH4-forms of CHA zeolite catalysts, the 0.1 M Cu-NH4-CHA showed the best catalytic performance, achieving 50% NOx conversion at a temperature as low as 192 °C, and reaching full conversion of NOx at 261 °C. These Cu-based CHA zeolite catalysts are promising thanks to their environmentally friendly synthesis and offer the opportunity of maximizing DeNOx strategies in applications for NOx pollution abatement.

With increasingly stringent emissions legislation, such as that stipulated by the International Maritime Organization, for nitrogen oxide emission reduction in marine diesel engines, the imperative of curtailing nitrogen oxide emissions from marine diesel engines is intensifying. Consequently, the significance of aftertreatment technologies, including diesel particulate filters (DPFs) and selective catalytic reduction (SCR), is poised to grow substantially. In particular, a redesign is required to reduce the size of DPF and SCR systems for application in small ships. In this study, we varied the shape of the filters in DPF and SCR systems, aiming to achieve a distinct flow pattern and enable overall miniaturization. The performance metrics, including the nitric oxide (NO) reduction rate, NH3 slip rate, and pressure drop, of the redesigned models were compared with those of the conventional model. Computational fluid dynamics simulations were used to compare the performance of the redesigned model with that of the conventional model in terms of NO reduction and pressure drop. The redesigned system achieved a NO reduction rate of 6.9% below that of the conventional system, offering additional noteworthy benefits such as a 50% reduction in both pressure and overall length.

Cu-SSZ-39 zeolite with an AEI structure exhibits excellent hydrothermal stability and can be a potential alternative to Cu-SSZ-13 zeolite SCR catalysts for NOx removal in diesel vehicles. However, the inferior low-temperature performance of Cu-SSZ-39 leads to substantial NOx emissions during the cold-start period, impeding its practical application. In this study, Ce-Mn oxide-modified Cu-SSZ-39 catalysts (CeMnOx/Cu-SSZ-39) and references (CeO2/Cu-SSZ-39 and MnOx/Cu-SSZ-39) were prepared by the ion-exchange of Cu ions followed by impregnation of the oxide precursors, with the aim of enhancing the NH3-SCR performance at low temperatures. The modified catalysts exhibited improved low-temperature activity and hydrothermal stability compared to the unmodified counterpart. In particular, CeMnOx/Cu-SSZ-39 showed the highest activity among the three catalysts and achieved NOx conversions above 90% within the temperature range of 180 °C to 600 °C, even after undergoing hydrothermal aging at 800 °C. Experimental results indicated that the synergistic effect between Ce and Mn in CeMnOx improves the redox properties and acidity of the catalyst due to the presence of Ce3+, Mn4+, and abundant adsorbed oxygen species, which facilitate low-temperature SCR reactions. Furthermore, the interaction of CeMnOx with Cu-SSZ-39 stabilizes the zeolite framework and hinders the agglomeration of Cu species during the hydrothermal aging process, contributing to its exceptional hydrothermal stability. The kinetics and NO oxidation experiments demonstrated that CeMnOx provides access to fast SCR reaction pathways by oxidizing NO to NO2, resulting in a significant increase in low-temperature activity. This study provides novel guidelines for the design and preparation of Cu-SSZ-39 zeolite with outstanding SCR performance over a wide temperature range.

Rational development of high-performance catalysts for selective catalytic reduction (SCR) is important for NOx removal. As the most widely used commercial catalysts, coated monolithic catalysts need to adapt to the harsh external conditions, which make researchers concerned about maintaining structural integrity, catalytic activity, and toxicity resistance in services. Herein, we seek solutions by clarifying the influences of coating process parameters on these three concerns, and trying to tackle the technical difficulties of coated monolithic catalysts in SCR applications. The insights presented in this paper are beneficial to the synthesis optimization and engineering innovations for SCR catalysts.

This paper proposes a gain-scheduling (GS) control strategy for selective catalytic reduction (SCR) systems in diesel engines, to minimize both nitrogen oxides (NOx) emissions and ammonia (NH3) slip downstream of the SCR catalyst. The proposed GS controller switches among multiple linear time-invariant H∞ controllers based on the engine's operating condition, and adopts three measurable GS parameters, that is, the amount of NOx entering the SCR catalyst, exhaust gas temperature in the catalyst, and ammonia slip measurement. While switching surfaces for the first two GS parameters are determined by simply dividing their operating ranges, to find optimal switching surfaces for the ammonia slip GS parameter, a novel method called Violation-Time-based Decision method is proposed. The efficiency of the proposed GS SCR controller is validated in simulations using real experimental data obtained from a diesel engine in the Non-Road-Transient Cycle (NRTC). [ABSTRACT FROM AUTHOR]

In this experimental investigation, a procreation approach was used to produce a catalyst based on SnO2@rGO nanocomposite for use in a selective catalytic reduction (SCR) system. Plastic waste oil is one such alternative that helps to ensure the survival of fossil fuels and also lessens the negative impacts of improper waste disposal. The SnO2@rGO nanocomposite was prepared by fine dispersion of SnO2 nanoparticles on monolayer-dispersed reduced graphene oxide (rGO) and carefully investigated for its potential in adsorbing CO, CO2, NOX, and hydrocarbon (HC). The as-synthesized SnO2@rGO nanocomposite was characterized by Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction spectroscopy, thermogravimetry, and surface area analyses. Then, the impact of catalysts inside the exhaust engine system was evaluated in a realistic setting with a single-cylinder, direct-injection diesel engine. As a result, the catalysts reduced harmful pollution emissions while marginally increasing brake-specific fuel consumption. The nanocomposite was shown to exhibit higher NOX adsorption efficiencies when working with different toxic gases. Maximum reductions in the emission of NOX, hydrocarbons, and CO were achieved at a rate of 78%, 62%, and 15%, respectively. These harmful pollutants were adsorbed on the active sites of catalyst and are converted to useful fuel gases through catalytic reduction thereby hindering the trajectory of global warming. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vessel emissions have contributed a great deal to air quality deterioration in China. Hence, the Chinese government has promulgated a series of stringent emission regulations. It is in this context that vessel emission control technology research is in full swing. In particular, during the 13th Five-Year Plan, the air pollution control technology of vessels has greatly improved. Vessel emission control has followed two main governance routes: source emission reduction and aftertreatment technology. Source control focuses on alternative fuels, with two main directions, the development of new fuels and the modification of existing fuels. Moreover, after-treatment technologies have also been developed, including wet desulfurization technology using seawater or alkaline liquids as wet washing liquids and selective catalytic reduction (SCR) for the control of NO x emission. Due to China's increasingly stringent emissions standards and regulations, work on the development of clean alternative fuels and further upgrading the collaborative application of after-treatment technologies to meet the near-zero-emissions requirements of vessels is still necessary. [Display omitted] [ABSTRACT FROM AUTHOR]

Effective adsorption and speedy surface reactions are vital requirements for efficient active sites in catalysis, but it remains challenging to maximize these two functions simultaneously. We present a solution to this issue by designing a series of atom‐pair catalytic sites with tunable electronic interactions. As a case study, NO selective reduction occurring on V1−W1/TiO2 is chosen. Experimental and theoretical results reveal that the synergistic electron effect present between the paired atoms enriches high‐energy spin charge around the Fermi level, simultaneously rendering reactant (NH3 or O2) adsorption more effective and subsequent surface reactions speedier as compared with single V or W atom alone, and hence higher reaction rates. This strategy enables us to rationally design a high‐performance V1−Mo1/TiO2 catalyst with optimized vanadium(IV)‐molybdenum(V) electronic interactions, which has exceptional activity significantly higher than the commercial or reported catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Manganese-based catalysts are characterized by electron paramagnetic resonance. • Superoxide radical (O 2 *) is observed in all samples. • O 2 * is born of accepting electrons through overlapped orbits of Mn-d and O-p. • O 2 * produces nitrogen-containing free radicals during SCR. • Ce and La doping increase the number of O 2 *, thus increasing SCR performances. Manganese-based catalysts attract extensive attentions in low-temperature selective catalytic reduction (SCR) of nitrogen oxide (NO x). However, seldom work focuses on the existence of free radicals and their roles in SCR. In this work, electron paramagnetic resonance spectrometer and density functional theory are combined to reveal surface characterizations of manganese oxide and Ce/La-doped manganese oxides. As a result, superoxide radical (O 2 *) exists on manganese-oxide surface, produces nitrogen-containing free radical, and functions as electron transfer between NO x and NH 3 at 100 °C, resulting in good NO x conversion as well as N 2 selectivity at the same time. The O 2 * is born of accepting electrons on adsorbed oxygen through overlapped orbits of Mn-d and O-p. Additional metal doping increases the percentage of O 2 * among all oxygen species from 2.9 % to 6.9 % (Ce doping) and 5.1 % (La doping). The order of O 2 * percentage is consistent with the NO x -conversion order at 100 °C, i.e., Ce doping (91.6 %) > La doping (55.7 %) > catalyst without doping (27.5 %). Above result helps to understand interface behaviors of manganese-based catalyst in SCR. This work is also in favor of developing more effective low-temperature catalysts. [ABSTRACT FROM AUTHOR]

The purpose of this study is to improve the simultaneous reduction of NOX and CO, harmful gases emitted from internal combustion engines, at low temperatures using a Pt/TiO2 H2-SCR catalyst. A better NOX/CO reduction performance was observed upon loading 2 wt% of the additive catalyst CeO2 on the main catalyst Pt because the oxygen storage capacity improved. In the presence of CO, the water gas reaction was promoted, resulting in the NOX conversion rate by the 0.5Pt−2CeO2/TiO2 SCR catalyst of 42 % at 75 °C and 70 % at 100 °C; this was a 15 ∼ 20 % higher NOX conversion as compared to without CO at low temperatures. The NOX reduction performance by the 0.5Pt−2CeO2−2ZrO2/TiO2 SCR catalyst was the highest at temperatures below 100 °C. At an appropriate amount of the additive catalyst ZrO2, the reaction rate improved because the acid point of the catalyst surface and the intensity of adsorption are adjusted. The optimum reduction temperature for NOX/CO reduction performance by the H2-SCR catalyst was 400 °C. Our results also indicate that the Pt species has a significant impact. [ABSTRACT FROM AUTHOR]