Abstract ：

控制大气中氮氧化物的排放对环境和人体健康有着至关重要的作用,应用于NOx去除的技术有很多,其中选择性催化还原(NH3-SCR)技术是去除NOx极有效的技术之一,利用CO去除NOx为烟气脱硝(CO-SCR)提供了 一种简单且低成本的技术,直接催化分解NOx被认为是去除NOx最理想、最环保的技术.Cu离子分子筛作为去除NOx的高效催化剂,具有宽温度窗口和良好的水热稳定性.本文综述了 Cu交换分子筛在去除NO领域的研究进展,讨论了 Cu离子分子筛在NH3-SCR、CO-SCR以及直接催化分解NO中的应用,着重总结了 Cu离子参与去除NO的反应机理,归纳了分子筛中Cu活性位点对脱硝性能的影响,还讨论了铜离子分子筛的抗H2O和SO2中毒性能,展望了 Cu离子分子筛未来可能的发展方向.

Keyword ：

CO-SCR NH3-SCR Cu离子分子筛 NO直接分解 NOx去除

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Selective catalytic reduction denitration technology, abbreviated as SCR, is essential for the removal of nitrogen oxide from the flue gas of coal-fired power stations and has been widely used. Due to the strong demand for energy and the requirements for environmental protection, a large amount of SCR catalyst waste is produced. The spent SCR catalyst contains high-grade valuable metals, and proper disposal or treatment of the SCR catalyst can protect the environment and realize resource recycling. This review focuses on the two main routes of regeneration and recycling of spent vanadium-titanium SCR catalysts that are currently most widely commercially used and summarizes in detail the technologies of recycling, high-efficiency recycling, and recycling of valuable components of spent vanadium-titanium SCR catalysts. This review also discusses in depth the future development direction of recycling spent vanadium-titanium SCR catalysts. It provides a reference for promoting recycling, which is crucial for resource recovery and green and low-carbon development.

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Sodium (Na) and potassium (K) are frequently encountered alkali metals in industrial exhaust gases, and their presence can significantly diminish the catalytic performance of the catalyst during the NH3-SCR reaction. Here, we prepared a catalyst using layered montmorillonite clay pillared with manganese and iron (termed Mn-Fe-PILC) as well as its niobium-modified counterpart (referred to as Nb/Mn-Fe-PILC). Furthermore, additional samples denoted as Mn-Fe-PILC-M and Nb/Mn-Fe-PILC-M (where M = Na or K) were synthesized using the impregnation method with a nitrate aqueous solution of Na or K. The results revealed an obvious enhancement in the catalytic activity of NH3-SCR upon the inclusion of Nb, with the best catalyst achieving a NOx conversion rate of 95% at 300 degrees C. Moreover, the resistance of the Mn-Fe-PILC catalyst to alkali metals was notably increased. Subsequent characterization demonstrated that the introduction of Nb to Mn-Fe-PILC led to an increase in the quantity of tetravalent manganese species present on the catalyst, alteration in reducibility, and augmentation in the number of acid sites, thereby enhancing the catalyst's resistance to alkali metals. Furthermore, in situ DRIFTS experiments revealed that the modification with Nb resulted in an amplified adsorption capacity for ammonia or nitric oxide, particularly influencing the formation of ammonia intermediates and nitrate species. These alterations proved beneficial in bolstering the alkali metal resistance of the catalyst.

Cite：

Copy from the list or Export to your reference management。

Abstract ：

NiCuFe layered double oxide (LDO) catalysts were synthesized using co-precipitation, impregnation, and urea hydrothermal methods. The NH3-SCR activity of NiCuFe-LDO catalysts was investigated to determine the effect of different synthesis methods. All NiCuFe-LDO samples exhibited good catalytic performance at low temperatures, with the sample synthesized using the urea hydrothermal method (NiCuFe-LDO-3) being the most efficient catalyst. The NiCuFe-LDO-3 catalyst achieved over 80% NO conversion in the temperature range of 180(degrees)C to 280 C-degrees, with a peak of 95.13% at 240(degrees)C. The physicochemical properties of the samples were systematically characterized using XRD, SEM, BET, NH3-TPD, H-2-TPR, XPS, and in-situ DRIFTS. The results showed that the NiCuFe-LDO-3 sample had the best crystallinity, as demonstrated by XRD and SEM. BET analysis revealed that the NiCuFe-LDO-3 sample had the largest specific surface area. The NiCuFe-LDO-3 sample was found to have more acidic sites and a better redox capacity than the other samples, according to the H-2-TPR and NH3-TPD results. In-situ DRIFTS analysis showed that the catalyst operates through both E-R and L-H reaction mechanisms.

Keyword ：

NH3-SCR Urea Hydrothermal Heterogeneous catalysis LDO NiCuFeOx

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Mn-based spinel as a catalyst for low-temperature selective catalytic reduction with ammonia (NH3-SCR) has been widely studied. However, most researchers have focused on double transition metal Mn-based spinel and the reports about doping with non-transition metal are not common. Herein, Mg2+ and Zn2+ with similar ionic radii were used to prepare high purity MgMn2O4 and ZnMn2O4 (named MMO and ZMO) to study their structure and activity relationships in NH3-SCR. It was found that the denitration performance of the two showed significant differences at low temperature despite have a very similar crystal structure. A series of characterization methods and first-principles calculations demonstrates that the relatively weak bonding strength and basic adsorption sites of MMO catalyst are the key factors contributing to its superior reactivity at low temperatures. This work provides novel insights and ideas in comprehending the catalytic function of non-transition metaldoped Mn-based spinels in NH3-SCR reactions.

Keyword ：

NH3-SCR Structure-activity relationship Catalysts

Cite：

Copy from the list or Export to your reference management。

Abstract ：

CH 4 + NH 3 + NO x + N 2 O coupling system was proposed for high-effective simultaneous catalytic reduction of both NO and N 2 O from flue gas generated by nitric or adipic acid industries. The Fe-SSZ-13 catalyst performed both elegant activity for NO x and N 2 O at 400-600 degrees C. Based on experimental studies, the active Fe species were illustrated and the transforming of Fe species during the N 2 O decomposition ( de N 2 O) and selective catalytic reduction (SCR) processes was clarified. It found that de N 2 O could cause the main active sites of [Fe-O 2 -Fe] 2+ transform to [Fe-O-Fe] 2+ and consequently inhibited the NH 3 -SCR process over the Fe-SSZ-13 catalyst. Meanwhile, the alpha O* generated via N 2 O decomposition would strengthen NO oxidation to NO 2 , which is advantageous to NH 3 -SCR. More importantly, the functions of CH 4 for de N 2 O and NH 3 -SCR were also investigated. CH 4 could work as reductant to convert N 2 O over the Fe-SSZ-13. CH 4 could also facilitate the reduction of NO; however, NH 3 has stronger activity to NO than that of CH 4 . And CH 4 was easily oxidized by O 2 rather than N 2 O or NO, which significantly limit the CH 4 -SCR for N 2 O with present of O 2 . At the same time, CH 4 can also accelerate alpha O* consumption that somehow enhance deN 2 O efficiency. Moreover, the consumption of alpha O* by CH 4 prevent the transforming of [Fe-O 2 -Fe] 2+ to [Fe-O-Fe] 2+ , and CH 4 play an important role on turnover rates of [Fe-O 2 -Fe] 2+ and [Fe-O-Fe] 2+ active sites, guaranteeing both satisfactory purifying efficiency for NO and N 2 O. This work reveals the positive promoting effect of CH 4 on simultaneous reduction of NO x and N 2 O, and proposes a potential catalyst for implementation.

Keyword ：

N2O decomposition Coupling reaction Methane Mechanisms NH3-SCR

Cite：

Copy from the list or Export to your reference management。

Abstract ：

In this study, a series of gamma-Fe2O3-modified V2O5-MoO3/TiO2 (VMT) catalysts was prepared by wet impregnation method. The gamma-Fe2O3-modified catalysts exhibited excellent catalytic performance, and 1.25 wt% gamma-Fe2O3 content improved the deNOx efficiency at 150 degrees C from 54% (unmodified VMT catalyst) to 84% (modified catalyst). BET, XRD, XPS, NH3-TPD, H2-TPR, and in situ DRIFTs were employed to characterize the physicochemical properties and reaction mechanisms of the catalysts. The introduction of gamma-Fe2O3 increased the V5+/V4+ ratio, surface chemisorbed oxygen content, redox ability, and a number of acid sites in the prepared catalysts. XPS confirmed the addition of gamma-Fe2O3 introduced new charge transfer pathways (Fe3+/Fe2+ <-> V5+/V4+). In situ DRIFTs suggested that the addition of gamma-Fe2O3 to the catalyst significantly increased the adsorption capacity of catalyst for NH3 and NOx, while also exerting a strong activating effect on the adsorbed NH3. Furthermore, selective catalytic reduction over the VMT and 5PEG@1.25Fe-VMT catalysts followed the Eley-Rideal (E-R) mechanism. At temperatures above 200 degrees C, the 5PEG@1.25Fe-VMT catalyst also followed the Langmuir-Hinshelwood (L-H) mechanism.

Keyword ：

V2O5-MoO3/TiO2 NH3-SCR Low-temperature gamma-Fe2O3

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Amorphous metal oxides have aroused extensive research interest in heterogeneous catalysis owing to their high surface area and rich surface defects. In this work, we synthesized a series of non-crystalline derivatives of Mn-BTC-BM MOF using a mechanochemical approach for NH3-selective catalytic reduction (SCR). The thermal decomposition of Mn-BTC-BM at 400gases yielded Mn (II, III) oxide (Mn-BTC-BM-400) with retained non-crystalline characteristics, which exhibited a smaller grain size and lower Mn-O bond energy than derivatives obtained through hydrothermal methods and other temperatures. This results in increased surface defects and acidic sites, promoting the release of lattice oxygen and leading to optimal low-temperature NH3-SCR activity. The Mn-BTC-BM-400 achieved an impressive 90 % conversion rate for NO at 170 celcius, and exhibited the lowest apparent activation energy (E-a=18 kJ/mol) among the six catalysts. This study presents a simple synthesis approach for non-crystalline MnOx catalysts, with mechanochemical synthesis offering promising improvements in catalytic performance.

Keyword ：

low-temperature NH3- SCR Acidic sites Mechanochemical Metal-organic frameworks Surface defects

Cite：

Copy from the list or Export to your reference management。

Abstract ：

By controlling preparation conditions, a series of catalysts were synthesized. Among them, ST-400 presented primary CuMn2O4 spinel phase and expectant denitration efficiency at low temperature. Then, various concentrations Hexadecyl trimethyl ammonium Bromide (hereinafter referred to as CTAB) were added into ST-400. Among them, 0.3C-ST-400 showed higher NO removal rate, more acid sites and greater redox performance. What's more, due to the strong interaction and electron transfer of metal ions, there was equilibrium: 2Mn(3+) -><- Mn2+ + Mn4+ and Cu2+ + Mn3+ -><- Cu+ + Mn4+, and the addition of CTAB could promote the equilibrium to the right. More concentration of Mn4+ and chemisorbed oxygen would be the facilitation for catalytic activity at low temperatures. In situ DRIFT experiments indicated that Langmuir-Hinshelwood mechanism plays a major role over both ST-400 and 0.3C-ST-400. However, compared with ST-400, the addition of CTAB results in the present of Eley-Rideal mechanism over 0.3C-ST-400. Besides, the CTAB promotes the adsorption intensity of NH3 and nitrate species as well as the conversion to active nitrate species, which will markedly stimulate the effect of Langmuir-Hinshelwood mechanism. In consequence, the propre addition of CTAB is a novel strategy in favor of NH3-SCR activity-enhancement research.

Keyword ：

Calcination temperature NH3-SCR CTAB Reaction mechanism CuMn2O4

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Low-temperature selective catalytic reduction (SCR) of NO by NH3 over supported NdV/Ti-x% (x = 1, 5, and 10) catalysts has been assessed in a microwave field. The NO conversion of NdV/Ti-10% catalyst reached above 85% in three cycles at temperatures ranging from 120 to 200 degrees C, with a N-2 selectivity of ca. 90%. The catalysts before and after activity evaluation were characterized by means of XRD, TEM, H-2-TPR, TPD, in situ DRIFTs etc. The results suggested that the catalysts exhibited excellent stability in the microwave field. It also showed that catalysts after microwave irradiation possessed an enhanced formation of oxygen species, monodentate nitrite and bridging bidentate nitrates on the catalysts' surface, which favored the generation of gaseous NO2 to promote the "fast SCR" process. Additionally, the results implied that oxygen species activation and NO oxidation to NO2 over the catalyst were favored in the microwave field, which facilitated NH3-SCR reaction at low temperatures.

Cite：

Copy from the list or Export to your reference management。