Search

In this study, a remarkable offset deactivation effect of K and P on MnEuOx SCR catalyst has been found. Experimental results showed that the NO conversion over K−P poisoned catalyst was close to 80 % at 250 °C. Several characterization techniques containing NH3‐TPD, XPS, H2‐TPR, XRD and in situ DRIFT were used to reveal the mechanism of the offset effect. The characterization of NH3‐TPD and H2‐TPR suggested that the introduction of P on MnEuOx‐K could improve its surface acidity and redox ability. Moreover, the content of chemisorbed oxygen and Mn4+ were markedly restored under the situation that the toxic elements were coexistent on catalyst surface. The strong interaction between K and P might be the major reason for the offset deactivation effect. More specifically, PO3− species were preferentially bonded with the surface potassium species and released MnO2 active sites poisoned by K. Therefore, the highly active MnO2 sites might be protected and the catalytic activity could be restored. [ABSTRACT FROM AUTHOR]

A series of Sb-doped CeVO 4 samples were synthetized by hydrothermal method and used in selective catalytic reduction of NO with NH 3. Contrasted with other catalysts, Sb 2 CeVO 4 possessed superior NH 3 -SCR activity and excellent SO 2 tolerance. Besides, the characterization results testified that Sb species in Sb 2 CeVO 4 could reduce the crystallization of CeVO 4 , and improve the surface acidity and reducibility. Moreover, the existence of Sb3+ was beneficial to generate more surface adsorbed oxygen species. Based on the in situ DRIFT spectra, more ad-NH 3 and ad-NO x species with higher reactivity were obtainable on Sb 2 CeVO 4 catalyst compared with that on CeVO 4 catalyst, which also contributed to enhancing the SCR activity by Langmuir-Hinshelwood (L-H) mechanism effectively. Image 1 • Sb modification could improve the SCR performance of CeVO 4 catalyst. • Sb3+ was beneficial to generate more surface adsorbed oxygen species. • More active ad-NH 3 and ad-NO x species were available on Sb 2 CeVO 4 catalyst. [ABSTRACT FROM AUTHOR]

In this study, it was found that the CeVO4-CeO2 nanocomposite possessed remarkably selective catalytic reduction (SCR) performance and wider active temperature scope. And, the promotion principle was explored based on BET, XRD, XPS, H2-temperature-programmed reduction, NH3-temperature-programmed desorption, and in situ diffuse reflectance infrared Fourier transform (DRIFT) techniques. The characterization outcomes manifested that the CeVO4-CeO2 nanocomposite could inhibit its crystallinity and enhance the concentrations of chemisorbed oxygen species and Ce3+, which was advantageous to the SCR process. Moreover, the in situ DRIFT technique manifested that the NH3-SCR reaction over Ce0.75V0.25Oy was enhanced effectively through the mechanism of L-H. [ABSTRACT FROM AUTHOR]

Fe was used as the modifier to improve the performance of CeZr2Ox catalyst for the selective catalytic reduction (SCR) reaction with ammonia. Experimental results revealed that proper Fe species (Fe/Ce molar ratio = 2) could effectively improve the SCR activity of CeZr2Ox, along with the elevated resistance to SO2 and H2O. The characterization results including BET, XRD, H2-TPR and NH3-TPD confirmed that Fe species in Fe2CeZr2Ox catalyst could inhibit the formation of ZrO2 crystals and lead to higher reducibility and surface acidity. In addition, more Ce3+ and surface active oxygen species could be detected on Fe2CeZr2Ox compared with CeZr2Ox. By means of in situ DRIFT technique, it could be deduced that the SCR reaction process over Fe2CeZr2Ox was accelerated mainly through theL-H pathway due to the advanced adsorption of NH3 and NOx species, along with the promoted NO conversion to NO2. Therefore, the modification of CeZrOx catalyst by Fe had a significant stimulation effect on its low-temperature SCR performance. [ABSTRACT FROM AUTHOR]

The different poisoning mechanisms of Cl and P on Mn/TiO 2 catalyst for selective catalytic reduction of NO x with NH 3 were investigated in this study. It was found that the poisoning effect of P was stronger than that of Cl, and the poisoning effect of Cl was very weak when the reaction temperature was over 250 °C. And the presence of Cl or P would weaken the poisoning effect of SO 2 and H 2 O. From the characterization results of temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS), the loading of P and Cl would lead to the decrease of reducible species and the loss of Mn 4+ and chemisorbed oxygen species, as a result, inhibiting the oxidation of NO to NO 2 .The results of temperature programmed desorption (TPD) study indicated that the presence of Cl only had a weak inhibition effect on the adsorption of NH 3 and NO x species over Mn/TiO 2 catalyst, while the addition of P on Mn/TiO 2 catalyst would greatly suppress the adsorption of NH 3 and NO x species. From the results of in situ DRIFT study, it could be found that the NH 3 –SCR reaction over Mn/TiO 2 catalyst was mainly controlled by L–H mechanism at lower temperature range (≤ 200 °C) and E–R mechanism at higher temperature range (≥ 250 °C). For Mn/TiO 2 Cl, the deactivation was mainly caused by the prohibited NO oxidation; while for Mn/TiO 2 P, the deactivation was mainly due to the seriously suppressed NO oxidation and NH 3 adsorption. [ABSTRACT FROM AUTHOR]

Ca salts in fly ash have a deactivation effect on SCR catalyst. In this study, the deactivation mechanism of Ca on Ce/TiO 2 catalyst was investigated in term of the in situ DRIFT study. The experimental results indicate that the poisoning effect increases with reaction temperature. From the results of in situ DRIFT study, it may be concluded that the NH 3 -SCR reaction over Ce/TiO 2 catalyst takes place though two pathways: the L -H mechanisms (<200 °C) and the E-R mechanism (>200 °C). For Ce/TiO 2 -Ca, the NH 3 -SCR reaction over it is mainly controlled by L -H mechanism. The deactivation of Ce/TiO 2 -Ca lies in the following two aspects: (1) the inhibited NH 3 adsorption and NO oxidation (<200 °C); (2) the greatly suppressed NH 3 adsorption and activation (>200 °C). [ABSTRACT FROM AUTHOR]

Heavy metals such as Zn have a poisoning effect on the catalyst for selective catalytic reduction of NO x with NH 3 . In this study, it was found that the modification of Mn/TiO 2 catalyst with Al 2 (SO 4 ) 3 could effectively enhance its Zn resistance. From the results of characterizations including XRD, H 2 -TPR, NH 3 -TPD and XPS, it could be concluded that the lower crystallinity, the higher reducibility, the generation of more acid sites, and the presence of more Mn 4+ and chemisorbed oxygen should mainly contribute to the good Zn resistance of Al 2 (SO 4 ) 3 -modified Mn/TiO 2 catalyst. The results of in situ DRIFT study indicated that the addition of Al 2 (SO 4 ) 3 did not change the mechanism of NH 3 -SCR reaction over Mn/TiO 2 catalyst, which was under the control of both Eley–Rideal and Langmuir–Hinshelwood mechanisms. [ABSTRACT FROM AUTHOR]

CeO-CuO catalysts were prepared by citric acid method at different calcination temperatures. The purpose of this study is to investigate the influence of calcination temperature on the catalytic activity of CeO2-CuO catalyst for the selective catalytic reduction of NO with NH3. As can be seen from the results, Ce-Cu(450) is of the best low temperature selective catalytic reduction (SCR) activity among the three catalysts, which may be resulted from its large surface area, good redox ability, strong NH3 adsorption capacity, and high concentration of Cu2+ and active oxygen species on the surface. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 385-389, 2014 [ABSTRACT FROM AUTHOR]

The deactivation mechanism of alkali metals on the SCR catalyst of Ce/TiO 2 was investigated by TPD and DRIFT studies. It could be found that the addition of Na or K on Ce/TiO 2 catalyst would restrict the adsorption of NH 3, accompanied by the generation of new sites for the adsorption of NO x species. But the new-absorbed NO x species were not active in the NH 3 -SCR reaction. The results of in situ DRIFT study indicated that the addition of Na and K did not change the SCR reaction mechanism, which was the combination of the Eley–Rideal and the Langmuir–Hinshelwood mechanisms. [ABSTRACT FROM AUTHOR]

The poisoning mechanism of Cl on Ce/TiO 2 catalyst was investigated based on temperature programmed desorption (TPD) and the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) studies. The results of NH 3 -TPD and NO-TPD indicated that the addition of Cl on Ce/TiO 2 catalyst would inhibit the adsorption of NH 3 species and NOx species on it. As can be seen from the results of in situ DRIFT study, the NH 3 -SCR reaction over Ce/TiO 2 and Ce/TiO 2 -Cl were all followed both the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism. And the decreased adsorption ability of NH 3 species and NOx species on the surface of Ce/TiO 2 -Cl should be mainly responsible for its low SCR activity. [ABSTRACT FROM AUTHOR]

Na has a serious deactivation effect on Mn/TiO 2 catalyst for selective catalytic reduction of NO with NH 3 . In this study, it was found that Sb had a promotion effect on the Na resistance of MnOx/TiO 2 catalyst. Then the promotion mechanism was investigated based on the characterization results of BET, XRD, H 2 -TPR, NH 3 -TPD, XPS and in situ DRIFT. The results of H 2 -TPR and NH 3 -TPD showed that the addition of Sb on MnOx/TiO 2 could enhance the redox ability and surface acidity respectively, and the results of DRIFT indicated that the addition of Sb on MnOx/TiO 2 could generate strong Lewis acid sites on the catalyst surface for NH 3 adsorption. Therefore, the doping of Sb has a promotion effect on the Na resistance of Mn/TiO 2 catalyst. [ABSTRACT FROM AUTHOR]

Heavy metals have been proven to be of deactivation effect on SCR catalyst. In this paper, the poisoning effect of heavy metals (Zn and Pb) on Mn/TiO 2 catalyst was investigated based on experimental and theoretical study. It was found that both of Zn and Pb had a poisoning effect on Mn/TiO 2 catalyst and the poisoning effect of Zn was more obvious. The characterization results indicated that the doping of heavy metals on Mn/TiO 2 surface would lead to a great decrease of reducibility, surface acidity and NO adsorption ability. The results of XPS characterization revealed the decrease of Mn 4+ atomic concentration and chemisorbed oxygen species caused by the doping of heavy metals. Based on the above mentioned unfavorable properties, the doping of heavy metals would cause a serious deactivation of Mn/TiO 2 catalyst. From the results of DFT calculations, it could be concluded that the doping of heavy metals on Mn/TiO 2 catalyst resulting in a great decrease of NH 3 adsorption capacity and NO adsorption ability, which agrees well with the experimental results. [ABSTRACT FROM AUTHOR]

• The effect of components in flue gas on commercial SCR catalyst was summarized. • The mechanisms of multifactorial synergism on VWT catalysts were first clarified. • Comprehensive approach to extend the lifetime of commercial catalysts was presented. • Concepts for catalyst lifetime prediction and management were reported. NO x does great harm to the environment and human beings. The selective catalytic reduction (SCR) of NO x with NH 3 is proven to be a mature technology to eliminate NO x from the waste gas, in which V 2 O 5 -WO 3 (MoO 3)/TiO 2 is the commercialized catalyst system. Lifetime is recognized as an important parameter to evaluate the practicality of the catalyst. However, this parameter is difficult to determine because of the variable flue gas conditions. Therefore, it is necessary to understand the impacts of different components on the deNO x performance of the catalysts so that rational lifetime management methods can be adopted. This advance would be introduced in this review first. Then the synergistic effects of multi-poisons on the catalysts would be summarized and illustrated. In accordance with these studies, some modification was conducted to enhance the catalyst's anti-poisoning ability to achieve the goal of prolonging the lifetime of the catalysts. Moreover, the latest research advances in the lifetime prediction of the SCR catalysts and the relevant management systems were summarized in the following section. This paper aims to provide theoretical guidance for simulating the catalyst deactivation process under actual conditions and shows a direction for constructing catalyst lifetime management systems. [ABSTRACT FROM AUTHOR]

Ce/TiO 2 is a prospective catalyst used for low temperature selective catalytic reduction (SCR) of NO with NH 3 . In this paper, the poisoning effect of Zn and Pb on the SCR performance of Ce/TiO 2 catalyst was investigated. Experimental results indicated that both Zn and Pb had a poisoning effect on Ce/TiO 2 catalyst, and Pb exhibited more poisoning effect than Zn in most of the reaction temperature range. Combined with the characterization results, we proposed that the enlargement of TiO 2 nanoparticles, the reduced chemisorbed oxygen content and surface acidity all contribute to the deactivation of Zn–Ce/TiO 2 and Pb–Ce/TiO 2 . [ABSTRACT FROM AUTHOR]

Mn/TiO 2 catalyst is of high activity for low temperature selective catalytic reduction (SCR) of NO with NH 3 . And the deposition of alkali metal would lead to the deactivation of Mn/TiO 2 catalyst. In this paper, the poisoning effect of Na and K on Mn/TiO 2 was investigated based on experimental and theoretical study. It was found that K had a stronger poisoning effect than that of Na. The bad performance of K–Mn/TiO 2 may be due to its small surface area, high crystallinity, weak surface acidity, low content of Mn 4+ and chemisorbed oxygen, and bad redox ability. The interpretation of the experimental results is supported by DFT calculations. [ABSTRACT FROM AUTHOR]

• Cr and Mn atoms are the main active sites over CrMn 1.5 O 4 (1 0 0) surface. • A reaction scheme for the reduction of NO on the surface of CrMn 1.5 O 4 catalyst is proposed. • The generation of N 2 is accomplished in two main steps. • The energy barrier for the reaction to generate NO 2 is extremely low and contributes significantly to the reduction of NO. A comprehensive study of the catalytic behavior of CrMn 1.5 O 4 catalysts in the selective catalytic reduction (SCR) of nitrogen oxides (NO x) using NH 3 as the reductant was presented. The active sites for NO x reduction and NH 3 adsorption on the CrMn 1.5 O 4 surface were identified by density functional theory (DFT) calculations. The study elucidates the mechanism of NH 3 dehydrogenation and NO reduction, revealing key intermediates and reaction pathways. DFT calculation results showed that the chromium and manganese atoms on the surface, participating in the specifically d − sp hybridization with NH 3 , NO, played a key role in adsorption, and that NH 3 dehydrogenation led to the formation of NH 2 , which was a key intermediate in the selective catalytic reduction reaction. To further understand the process of NO generation to NO 2 and N 2 O on the surface of CrMn 1.5 O 4 catalyst, the chain reaction steps of NO reduction were proposed. Among them, NO was oxidized to NO 2 , and the very low reaction energy barrier contributed greatly to the fast SCR reaction, while the generation of the unwanted product N 2 O had a relatively high energy barrier, so the reaction was not easy to occur. These findings contribute to a deeper understanding of the intricate catalytic behavior of CrMn 1.5 O 4 catalysts, which will aid in the development of better SCR catalysts for the effective removal of NO x in industrial settings. [ABSTRACT FROM AUTHOR]

A sequence of Cr-modified CeZr 2 O x catalysts were synthesized through the co-precipitation way and applied in selective catalytic reduction (SCR) of NO x with ammonia. The optimal catalyst (Cr 1 CeZr 2 O x) exhibited the excellent NH 3 -SCR activity and high SO 2 resistance. From the characterization results, Cr species in Cr 1 CeZr 2 O x could suppress the formation of ZrO 2 crystals, which could also contribute to stronger surface acidity and reducibility. Besides, more Ce3+ and surface adsorbed oxygen species were observed on Cr 1 CeZr 2 O x catalyst. On the basis of in situ DRIFT experiments, it could be confirmed that the NH 3 -SCR process on Cr 1 CeZr 2 O x was promoted through Langmuir-Hinshelwood (L-H) mechanism. Besides, the improved NO oxidation and more ad-NO x and ad-NH 3 also played a vital role for the superior low-temperature SCR activity of Cr 1 CeZr 2 O x. Unlabelled Image • Cr 1 CeZr 2 O x catalyst shows higher SCR activity and SO 2 tolerance. • The addition of Cr on CeZr 2 O x catalyst could generate more ad-reactants. • Cr in CeZr 2 O x catalyst could improve the reactivities of ad-reactants. [ABSTRACT FROM AUTHOR]

Ammonia selective catalytic reduction (NH 3 -SCR) of nitrogen oxides is an effective and well-established technology for NO x removal, but current commercial denitrification catalysts based on V 2 O 5 -WO 3 /TiO 2 have some obvious disadvantages, including narrow operating temperature windows, toxicity, poor hydrothermal stability, and unsatisfied SO 2 /H 2 O tolerance. To overcome these drawbacks, it is imperative to investigate new types of highly efficient catalysts. In order to design catalysts with outstanding selectivity, activity, and anti-poisoning ability, core-shell structured materials have been widely applied in the NH 3 -SCR reaction, which exhibits numerous advantages including the large surface area, the strong synergy interaction of core-shell materials, the confinement effect, and the shielding effect from the shell layer to protect the core. This review summarizes recent developments of core-shell structured catalysts for NH 3 -SCR, including basic classification, synthesis methods, and a detailed description of the performance and mechanisms of each type of catalyst. It is hoped that the review will stimulate future developments in NH 3 -SCR technology, leading to novel catalyst designs with improved denitrification performance. [Display omitted] • Core-shell structured materials have been widely applied in the NH 3 -SCR reaction. • Core-shell structured SCR catalyst shows high catalytic activity. • Core-shell structure could protect the active components from deactivation. [ABSTRACT FROM AUTHOR]

In this work, Mo-modified Mn/TiO 2 catalysts synthetized by co-precipitation method were applied in the SCR abatement of NOx by NH 3 . Ranging from 50 to 400 °C, Mn/TiO 2 modified with Mo showed higher efficiency in SCR reaction than Mn/TiO 2 without Mo. Among Mn/TiO 2 catalysts with different Mo doping amount, MnMo/TiO 2 -0.04 catalyst showed not only the highest SCR activity but also the best N 2 selectivity. Furthermore, MnMo/TiO 2 -0.04 also exhibited stronger resistance to SO 2 poisoning compared with Mn/TiO 2 . On the basis of the characterization means including BET, XRD, H 2 -TPR, XPS and NH 3 -TPD, MnMo/TiO 2 -0.04 was characterized with the decreased crystallinity, the increased reducibility and more surface acid sites, along with the enrichment of surface adsorbed oxygen species and Mn 4+ species. Furthermore, the analysis results of in situ DRIFT study showed that Langmuir-Hinshewood (L-H) model should be employed in explaining the accelerated SCR reaction over MnMo/TiO 2 -0.04. [ABSTRACT FROM AUTHOR]

The bad resistance to SO 2 was still the primary defect of Mn/TiO 2 catalyst for selective catalytic reduction of NOx with NH 3 . To address that, a series of MnNb/TiO 2 catalyst samples with different Nb/Mn molar ratio were prepared by sol-gel method and used in NH 3 -SCR reaction. Experimental results indicated that the MnNb/TiO 2 -0.12 catalyst exhibited outstanding SCR activity and SO 2 resistance. The introduction of Nb into Mn/TiO 2 catalyst could promote the formation of more Mn 4+ and chemisorbed oxygen species on its surface, along with the generation of more NO 2 . In addition, the doping of Nb on Mn/TiO 2 catalyst could remarkably intensify its surface acidity. All these factors were conducive to improving the SCR performance of MnNb/TiO 2 -0.12 catalyst. The results of DRIFT study revealed that the NH 3 -SCR reaction over MnNb/TiO 2 -0.12 catalyst took place through both Eley–Rideal and Langmuir-Hinshelwood pathways, in which Eley–Rideal pathway was predominant. In the presence of SO 2 , it seemed that the NH 3 -SCR reaction over Mn/TiO 2 and MnNb/TiO 2 -0.12 mainly happened between adsorbed NO 2 and gaseous NH 3 (Eley–Rideal mechanism), thus the formation of more NO 2 over MnNb/TiO 2 -0.12 catalyst should mainly account for its super SO 2 tolerance. [ABSTRACT FROM AUTHOR]

Fe was used as the modifier to improve the performance of CeZr2Ox catalyst for the selective catalytic reduction (SCR) reaction with ammonia. Experimental results revealed that proper Fe species (Fe/Ce molar ratio = 2) could effectively improve the SCR activity of CeZr2Ox, along with the elevated resistance to SO2 and H2O. The characterization results including BET, XRD, H2-TPR and NH3-TPD confirmed that Fe species in Fe2CeZr2Ox catalyst could inhibit the formation of ZrO2 crystals and lead to higher reducibility and surface acidity. In addition, more Ce3+ and surface active oxygen species could be detected on Fe2CeZr2Ox compared with CeZr2Ox. By means of in situ DRIFT technique, it could be deduced that the SCR reaction process over Fe2CeZr2Ox was accelerated mainly through theL-H pathway due to the advanced adsorption of NH3 and NOx species, along with the promoted NO conversion to NO2. Therefore, the modification of CeZrOx catalyst by Fe had a significant stimulation effect on its low-temperature SCR performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • CeSm/TiO 2 catalyst exhibits high low-temperature SCR activity. • The SCR reaction over CeSm/TiO 2 catalyst was controlled by L-H mechanism (<200 °C). • The promoted NO oxidation and NH3 adsorption are mainly responsible for the excellent performance of CeSm/TiO 2 catalyst. CeSmOx mixed oxide catalysts supported on TiO 2 prepared by coprecipitation method were used for selective catalytic reduction of NOx with NH 3. The results showed that the addition of Sm could effectively enhance the low-temperature SCR activity and SO 2 /H 2 O resistance of Ce/TiO 2 catalyst, and the appropriate mole ratio of Sm to Ce was 0.3. Characterization results indicated that the introduction of Sm could promote the formation of Ce3+ and chemisorbed oxygen species on catalyst surface, which was favorable to the generation of NO 2. Moreover, the doping of Sm could also promote the adsorption of NH 3 and NOx species on Ce/TiO 2 catalyst. The results of in situ DRIFT study revealed that the NH 3 -SCR reaction over CeSm/TiO 2 -0.3 catalyst was mainly controlled by the Langmuir−Hinshelwood mechanism in the low temperature range (<200 °C). Thereafter, the promoted NO oxidation and the enhanced NH 3 adsorption should play a major role for the excellent low-temperature SCR performance of CeSm/TiO 2 -0.3 catalyst. [ABSTRACT FROM AUTHOR]

A series of MnEuOx catalysts were prepared by the co-precipitation method and used for selective catalytic reduction of NOx with NH 3 . It was found that the modification of MnOx catalyst by Eu with a Eu/Mn molar ratio of 0.1 could greatly enhance its SCR activity and broaden its operating temperature window, accompanied by good resistance to SO 2 and H 2 O. From the characterization results of N 2 adsorption, XRD, XPS, H 2 -TPR, it could be concluded that the larger surface area resulted from the inhibited crystallization of MnOx, the enrichment of surface Mn 4+ and chemisorbed oxygen, and the higher reducibility all made a contribution to the high SCR activity of MnEuOx-0.1 catalyst. Furthermore, the results of in situ DRIFTS study revealed the NH 3 -SCR reactions over MnOx and MnEuOx-0.1 were mainly controlled by L-H mechanism (<150 °C) and E-R mechanism (>150 °C) respectively, and the contribution of E–R mechanism became more important with increasing reaction temperature. The enhanced NO oxidation and NH 3 adsorption should be mainly contribute to the distinguished SCR performance of MnEuOx catalyst in the lower temperature range (<150 °C) and higher temperature range (>150 °C) respectively. [ABSTRACT FROM AUTHOR]

Heavy metals (such as Zn and Pb) have a deactivation effect on the catalyst for selective catalytic reduction of NO with NH 3 . In this study, it was found that the modification of Mn/TiO 2 catalyst by Nb could greatly enhance its Zn resistance. From the characterization results of BET, XRD, H 2 -TPR, NH 3 -TPD, it may be concluded that the introduction of Nb into Mn/TiO 2 catalyst would lead to its lower crystallinity, more acid sites and higher concentrations of Mn 4 + and surface chemisorbed oxygen. The results of in situ DRIFT study reveal that the NH 3 -SCR reactions over Mn/TiO 2 and Mn-Nb/TiO 2 all obey both the Langmuir-Hinshelwood mechanism and the Eley–Rideal mechanism, and the doping of Nb on Mn/TiO 2 catalyst could promote the adsorption of NH 3 and NOx species on it. All these features make a contribution to the high SCR activity and good Zn resistance of Mn-Nb/TiO 2 catalyst. [ABSTRACT FROM AUTHOR]

A series of Mn/TiWO x catalysts were prepared and used in NH 3 -SCR reaction for NO x emission control. The experimental results showed that the SCR activities of Mn/TiWO x catalysts are higher than that of Mn/TiO 2 catalyst. After that, several characterization techniques including XRD, H 2 -TPR, NH 3 -TPD, XPS were used to investigate the effect of TiWO x support on the SCR performance of Mn/TiWO x (1:1) catalyst. The stronger reducibility and NH 3 adsorption capacity, and more surface chemisorbed oxygen of Mn/TiWO x (1:1) should all contribute to its better SCR performance. Moreover, Mn/TiWO x (1:1) catalyst shows higher N 2 selectivity, better SO 2 tolerance and stability than Mn/TiO 2 catalyst. The results of in situ DRIFT study revealed that the NH 3 -SCR reactions over Mn/TiO 2 and Mn/TiWO x (1:1) were all followed the Langmuir–Hinshelwood mechanism, in which the SCR reaction takes place between the adsorbed NH 3 species and NO x species. [ABSTRACT FROM AUTHOR]

The effect of HF treatment on the performance of ceria for selective catalytic reduction of NO with NH 3 was investigated in this study. The experimental results showed that HF treatment could greatly enhance the SCR performance of ceria within the temperature range of 100–400 °C. From the characterization results of Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), temperature programmed reduction of hydrogen (H 2 -TPR), temperature programmed desorption of ammonia (NH 3 -TPD) and X-ray photoelectron spectroscopy (XPS), the good performance of HF-treated ceria may be attributed to its lower crystallinity, better reducibility, higher NH 3 adsorption capacity, and the enrichment of surface chemisorbed oxygen. And the results of in situ DRIFT study indicate that the NH 3 -SCR reactions on CeO 2 and CeO 2 -F mainly follow the Eley–Rideal mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nb modification can promote the adsorption of reactants on CuCeO x catalyst. • The SCR reaction on CuCeNbO x -0.4 catalyst mainly follows the L-H and E-R mechanisms. • The formed dual redox cycle on CuCeNbO x -0.4 catalyst favors the low-temperature SCR reaction. CuCeO x and CuCeNbO x - k with different Nb doping ratios were obtained by the citric acid method and applied in NH 3 -SCR process. The activity test results elucidated that the addition of Nb effectively ameliorated the low-temperature SCR performance. Among them, CuCeNbO x -0.4 catalyst had the finest SCR activity (more than 90% in 185–370 °C), highest N 2 selectivity, excellent SO 2 &H 2 O resistance and thermal stability. Numerous characterization analysis demonstrated that CuCeNbO x -0.4 had the largest specific surface area, the strongest surface acidity and the most excellent redox properties. The conclusions of in situ DRIFT manifested the Nb modification generated more activated species, enhanced the reactivity of ad-NH 3 and ad-NO x species, and the SCR reaction on CuCeNbO x -0.4 mainly followed the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Furthermore, the Nb doping also formed the dual redox cycle (Cu2+ + Nb4+ ↔ Cu+ + Nb5+, Cu2+ + Ce3+ ↔ Cu+ + Ce4+), which facilitated the low-temperature SCR reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • MnCe/TiO 2 -FL shows fabulous SCR performance and superior resistance to SO 2 /H 2 O. • More ad-NH 3 and ad-NOx species are available on the surface of MnCe/TiO 2 -FL. • The redox cycle "Mn4+ + Ce3+ ↔ Mn3+ + Ce4+" greatly promote the SCR reaction over MnCe/TiO 2 -FL. In this work, a flower-like TiO 2 support was firstly synthesized via the hydrothermal method, and then Mn and Ce were loaded onto the synthesized flower-like TiO 2 carrier by impregnation for the selective catalytic reduction of NO with NH 3 (NH 3 -SCR). The activity test results manifested that the flower-like MnCe/TiO 2 (MnCe/TiO 2 -FL) catalyst exhibited marvelous SCR performance (almost 100% NO conversion in the range of 150–250 °C) and satisfactory resistance to SO 2 and H 2 O. Based on a series of characterization experiments, it could be found that the MnCe/TiO 2 -FL catalyst possessed a larger surface area, higher Ce3+ and Mn4+ content, superior surface acidity and redox performance, which greatly ameliorated to the SCR performance of the MnCe/TiO 2 -FL catalyst. Furthermore, the accelerated surface adsorbed oxygen mobility and the increased quantity of active species also promoted to the SCR activity of MnCe/TiO 2 -FL at low temperatures. [ABSTRACT FROM AUTHOR]

The effect of F and Cl on Mn/TiO 2 catalyst for selective catalytic reduction of NO with NH 3 was investigated in this study. It was found that the doping of F or Cl has a deactivation effect on Mn/TiO 2 catalyst. And the poisoning effect of Cl is more serious than that of F. The characterization results showed that the decrease of BET surface area, the increase of crystallinity, the reduced reducibility and surface acidity, and the decreased concentrations of surface Mn 4 + and chemisorbed oxygen should be responsible for the deactivation of Mn/TiO 2 catalyst by the doping of F or Cl. [ABSTRACT FROM AUTHOR]

• The chemical deactivation mechanisms of Mn-based SCR catalysts are analyzed. • The methods for improving the poisoning resistance of Mn-based SCR catalysts are discussed. • The regeneration of manganese-based SCR catalysts are probed. As a high-performance technology currently developed, selective catalytic reduction (SCR) of NO x with NH 3 has been universally employed to remove NO x from stationary sources. The traditional applied V 2 O 5 -based catalysts are proverbially applicable for medium-temperature range but unsuitable for NH 3 -SCR operated in the low-temperature conditions. Through massive research of theory and experiments, low-temperature NH 3 -SCR has drawn substantial attention due to the extensive demand for industrial furnaces and their energy-saving characteristics. During the past few years, Mn-based catalysts have been extensively investigated in NH 3 -SCR reaction for their high catalytic activity at low temperatures. In this paper, the deactivation mechanisms of SO 2 , H 2 O, alkali/alkaline earth metals (K, Na, Ca), and heavy metals (As, Pb, etc.) over Mn-based catalysts are discussed in detail. This review summarizes the methods to improve the anti poisoning of manganese-based catalysts, such as specific preparation methods, adding active components, doping additions and carrier modification, etc. Finally, different regeneration methods of poisoning caused by various poisons were analyzed and compared The obtained results can help researchers provide insight into the optimization of Mn-based SCR catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ce doping could improve the SCR activity effectively for Cu-SSZ-13 catalyst. • The highly active Cu2+ sites might be protected and the catalytic activity could be restored after the addition of Ce. • More ad-NH 3 and ad-NO x species with higher reactivity are available on Ce-Cu-SSZ-13 catalyst. Potassium has a deactivation effect on Cu-SSZ-13 catalyst for selective catalytic reduction of NO with NH 3 (NH 3 -SCR). It was demonstrated that the modification of Cu-SSZ-13 catalysts by Ce could improve its K resistance. The characterization of NH 3 -TPD and H 2 -TPR suggested that the introduction of Ce on Cu-SSZ-13 could improve its surface acidity and redox ability. Moreover, the content of Cu2+ and chemisorbed oxygen were markedly restored under the situation that Ce and K elements were coexistent on catalyst surface. The synergetic effect between Ce and Cu might be the major reason for the great K resistance and the excellent SCR performance. [ABSTRACT FROM AUTHOR]

• MnCrO x -UL shows superior NH 3 -SCR performance and high resistance to SO 2. • More ad-NH 3 and ad-NO x species are available on the surface of MnCrO x -UL. • The ad-NH 3 and ad-NO x species over MnCrO x -UL are of higher reactivity. A novel urchin-like catalyst (MnCrO x -UL) was successfully synthesized by hydrothermal redox reaction. In addition, a reference sample (MnCrO x) was prepared by co-precipitation process for comparison. Experimental results revealed that MnCrO x -UL showed superior NH 3 -SCR performance in the temperature range of 150–350 °C and high resistance to SO 2. The results of characterization demonstrated that MnCrO x -UL showed larger surface area, more acidic sites, higher redox capacity and more oxygen vacancies compared with MnCrO x. Additionally, more activated adsorbed species over MnCrO x -UL sample surface could also effectively improve the NH 3 -SCR performance at low temperature. [ABSTRACT FROM AUTHOR]

• The ball-flowerlike structure of CoMnO x -BF catalyst could remarkably enhance its low-temperature SCR activity. • More ad-NH 3 and ad-NO x species with higher reactivity are available on the surface of CoMnO x -BF catalyst. • The redox cycle "Mn4+ + Co2+ ↔ Mn3+ + Co3+" greatly promotes the low-temperature SCR reaction over CoMnO x -BF catalyst. A novel ball-flowerlike catalyst (CoMnO x -BF) was developed by hydrothermal method for the selective catalytic reduction (SCR) of NO x by NH 3. Besides, a counterpart sample (CoMnO x) was prepared by coprecipitation way for comparison. The activity test results demonstrated that CoMnO x -BF catalyst exhibited admirable SCR performance and N 2 selectivity in a broad temperature range of 150–350 °C, along with an excellent resistance to SO 2 and high durability. Based on characterization experiments, it could be found that the superior surface area resulted from suppressed crystallization, the enrichment of surface labile oxygen and Mn4+, the stronger surface acidity and redox ability were all beneficial to the NH 3 -SCR performance of CoMnO x -BF catalyst. Additionally, the enhanced NO oxidation and more activated ad-reactants on catalyst surface could also conduce to the outstanding SCR activity of CoMnO x -BF at low temperature. [ABSTRACT FROM AUTHOR]