Search

Sb-modified Mn/TiO 2 catalyst synthetized by sol–gel method exhibited outstanding performance in simultaneous Hg0 oxidation and NO reduction under SCR conditions at low temperature. NO removal (>90%) and Hg0 oxidation (>80%) were simultaneously obtained over MnSb/TiO 2 -0.25 catalyst in 200–300 °C with a GHSV of 54,000 h−1. Moreover, MnSb/TiO 2 -0.25 catalyst exhibited excellent tolerance to SO 2 and H 2 O. Characterization results suggested that the well-dispersed Mn, Sb and Ti species, along with the enriched Mn4+ and surface oxygen species on Mn-Sb/TiO 2 -0.25 catalyst should play a critical role in its excellent catalytic performance. The formed HgO had little inhibition effect on NO reduction over MnSb/TiO 2 -0.25 catalyst. And the coexistence of NO and O 2 has a promotion effect on Hg0 oxidation, while NH 3 exhibited an inhibition effect on oxidation of Hg0. In SCR reaction process, the Hg0 oxidation efficiency was suppressed, but this effect could be basically eliminated by using a relatively low GHSV value. Thus using MnSb/TiO 2 -0.25 for simultaneous Hg0 oxidation and NO reduction in SCR reactor may be workable in coal-burning power plants. Based on the results of experiments and characterizations, the mechanism of synchronous removal of Hg0 and NO on MnSb/TiO 2 -0.25 catalyst could be described as:Hg0(ad)+O α (O β)→HgO(ad), NO(g)+NO 2 (ad)+NH 3 (ad)→N 2 +H 2 O. Image 1 • NO removal (>90%) and Hg0 oxidation (>80%) are achieved on MnSb/TiO 2 -0.25 catalyst. • MnSb/TiO 2 -0.25 catalyst exhibits good SO 2 /H 2 O resistance. • The reaction mechanism of simultaneous removal of NO and Hg0 is proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sb doping could improve the SCR activity and SO 2 resistance effectively for Cu/TiO 2 catalyst. • The addition of Sb on Cu/TiO 2 catalyst could promote the adsorption of NH 3 and NOx species. • Sb in CuSb/TiO 2 -0.4 catalyst could enhance the reactivities of adsorbed reactants. Abstract The Cu/TiO 2 catalysts modified by Sb were compounded through the sol-gel way and put into use for the selective catalytic reduction (SCR) of NOx with NH 3. Experimental results suggested that CuSb/TiO 2 -0.4 exhibited the excellent NOx conversion and SO 2 tolerance. Subsequently, the relationship between surface physicochemical properties and catalytic performance was also investigated by different characterization methods. From characterizations, the introduction of Sb for Cu/TiO 2 could promote the generation of more Cu2+, surface adsorbed oxygen species and surface acid sites on CuSb/TiO 2 -0.4 catalyst. Furthermore, Sb species on CuSb/TiO 2 -0.4 could contribute to the formation of more surface ad-NOx and ad-NH 3 species, which would enhance the NH 3 -SCR process effectively through both the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. [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]

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]

In this study, it was found that the doping of Co on Mn/TiO 2 catalyst could enhance its K resistance. The characterization results showed that the modification of Mn/TiO 2 catalyst by Co could increase its reducibility and the adsorption of NH 3 and NO x species on it. From the results of in situ DRIFT study, the NH 3 -SCR reaction over Mn/TiO 2 catalyst obeyed the Langmuir–Hinshelwood mechanism. And the addition of K on Mn–Co/TiO 2 had little inhibition effect on NO x adsorption. These features made Mn–Co/TiO 2 catalyst show better K resistance than Mn/TiO 2 . [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 CeOx@MnOx catalyst with a core–shell structure was prepared and used for catalytic oxidation of NO. It was found that CeOx@MnOx catalyst showed higher intrinsic catalytic activity than CeMnOx catalyst prepared by citric acid method. Based on the characterization results of N 2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (H 2 -TPR) and X-ray photoelectron spectroscopy (XPS), we may conclude that the excellent catalytic performance of CeOx@MnOx catalyst is related to its low crystallinity, good reducibility, and high concentrations of Mn 4 + and active oxygen species. [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]

CeO2–CuO/Al2O3catalysts were prepared by three different methods and their activities for selective catalytic reduction (SCR) of NO with NH3were investigated. As can be seen from the experimental results, the catalyst prepared by the single-step sol–gel (SG) method showed the best SCR activity and resistance to SO2and H2O. In order to investigate the relationship between the preparation method and the performance of SCR catalysts, the catalysts were characterized by using Brunauer–Emmett–Teller, X-ray diffraction, temperature programmed reduction with hydrogen, temperature programmed desorption with ammonia, X-ray photoelectron spectroscopy, Fourier transform infrared and thermo-gravimetric analysis techniques. It was found that the excellent performance of CeO2–CuO/Al2O3catalyst prepared by the single-step SG method should be resulted from its large surface area, low crystallinity, high oxygen storage capacity, high NH3adsorption capacity, high concentration of surface chemisorbed oxygen, weak sulphation process and weak water absorption. [ABSTRACT FROM PUBLISHER]

• 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]

Sb was used as the additive to enhance the NH 3 -SCR performance of MnTiO x catalyst. Experimental results revealed that MnSbTiO x -0.2 demonstrated outstanding NH 3 -SCR activity in a wide temperature window (100–400 ℃) and high resistance to SO 2 . Characterization results indicated the introduction of Sb into MnTiO x catalyst could improve the dispersity of active species and generate more surface acid sites, Mn 4+ and surface adsorbed oxygen species. In situ DRIFT spectra proved that the presence of Sb in MnSbTiO x -0.2 catalyst could form new Brønsted acid sites, along with the increased surface Lewis acidity. The improved adsorption of NH 3 and NO x species over MnSbTiO x -0.2 catalyst had a stimulating effect on the NH 3 -SCR reaction over it through Langmuir−Hinshelwood (L-H) route. Moreover, Sb species in MnSbTiO x -0.2 could improve the reactivities of ad-NH 3 and ad-NO x species in SCR reaction. All these factors contributed to the excellent performance of MnSbTiO x -0.2 catalyst. [ABSTRACT FROM AUTHOR]