Progress in Natural Science-Materials International
·
2012
·Vol. 22
·期 4
·265-272
·
IF 1.099
Lei Chen,Duan Weng,Zhichun Si,Xiaodong Wu
WO 3 –CeO 2 –TiO 2 catalysts for NO (nitrogen monoxide) reduction by ammonia were prepared by a sol–gel method. The catalysts were characterized by BET, XRD, Raman, NH 3 /NO adsorption and H 2 -TPR to investigate the relationships among the catalyst composition, structure, redox property, acidity and deNO x activity. WO 3 –CeO 2 –TiO 2 catalysts show a high activity in a broad temperature range of 200–480 °C. The low-temperature activity of catalysts is sensitive to the catalyst composition especially under low-O 2 -content atmospheres. It may be related to the synergistic effect between CeO x and WO x in the catalysts. On one hand, the interaction between ceria and tungsten oxide promotes the activation of gaseous oxygen to compensate the lattice oxygen consumed in NH 3 -SCR (selective catalytic reduction) reaction at low temperatures. Meanwhile, the Brønsted acid sites mainly arise from tungsten oxides, Lewis acid sites mainly arise from ceria. Both of the Brønsted and Lewis acid sites facilitate the adsorption of NH 3 on catalysts and improve the stability of the adsorbed ammonia species, which are beneficial to the NH 3 -SCR reaction.
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高影响因子
MOLECULES
·
2025
·Vol. 30
·期 13
·2691
·
IF 4.6
Jiuhu Zhao,Jingjing Jiang,Guanyu Chen,Meng Wang,Xiaoyuan Zuo,Yanjiao Bi,Rongshu Zhu
The selective catalytic reduction of NOxwith CH4(CH4-SCR) holds the potential to simultaneously abate harmful NOxand CH4greenhouse gases. In this study, a series of bimetallic M-In/H-SSZ-39 catalysts (where M represents Cr, Co, Ce, and Fe) were prepared via an ion exchange method and subsequently evaluated for their CH4-SCR activity. The influences of the preparation parameters, including the metal ion concentration and calcination temperature, as well as the operating conditions, such as the CH4/NO ratio, O2concentration, water vapor content, and gas hourly space velocity (GHSV), on the catalytic activity of the optimal Cr-In/H-SSZ-39 catalyst were meticulously examined. The results revealed that the Cr-In/H-SSZ-39 catalyst exhibited peak CH4-SCR catalytic performance when the Cr(NO3)3concentration was 0.0075 M, the In(NO3)3concentration was 0.066 M, and the calcination temperature was 500 °C. Under optimal operating conditions, namely GHSV of 10,000 h−1, 400 ppm NO, 800 ppm CH4, 15 vol% O2, and 6 vol% H2O, the NOxconversion rate reached 93.4%. To shed light on the excellent performance of Cr-In/H-SSZ-39 under humid conditions, a comparative analysis of the crystalline phase, chemical composition, pore structure, surface chemical state, surface acidity, and redox properties of Cr-In/H-SSZ-39 and In/H-SSZ-39 was conducted. The characterization results indicated that the incorporation of Cr into In/H-SSZ-39 enhanced its acidity and also facilitated the generation of InO+active species, which promoted the oxidation of NO and the activation of CH4, respectively. A synergistic effect was observed between Cr and In species, which significantly improved the redox properties of the catalyst. Consequently, the activated CH4could further interact with InO+to produce carbon-containing intermediates such as HCOO−, which ultimately reacted with nitrate-based intermediates to yield N2, CO2, and H2O.
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高影响因子
VACUUM
·
2026
·
IF 4.3
Yuhao Wang,Jacob Senior Atta Owusu,Min Cui,Mingyu Su,Huqin Zheng,Sameer Shahid,Bingtao Zhao,Jarosław Zuwała,Yaxin Su
To advance hydrocarbon-selective catalytic reduction (HC-SCR) of NOx, ternary mixed metal oxide catalysts (Ni x Co y Ce z -LDO) were synthesized through calcination of layered double hydroxide (LDH) precursors prepared via urea-assisted homogeneous precipitation. The trimetallic catalysts demonstrated enhanced low-temperature activity, improved redox properties, and superior sulfur resistance, attributed to synergistic interactions among Ni, Co, and Ce. In particular, Ni 0.48 Co 0.24 Ce 0.28 -LDO exhibited optimal performance, attaining 96.6% NO conversion with 98.25% N 2 selectivity at 225 °C, while maintaining high stability under 5% O 2 and 0.02% SO 2 . Characterization (XRD, ICP, SEM and BET) confirmed the formation of highly dispersed nanocrystallites with uniformly distributed metals and identified CeO 2 as the dominant crystalline phase, which provided abundant Lewis acid sites for C 3 H 6 activation. XPS and H 2 -TPR results indicated that the incorporation of Ce increased the Ni 3+ /Ni 2+ and Co 3+ /Co 2+ ratios, promoted oxygen vacancy formation, and enhanced catalyst reducibility, while the presence of Ni facilitated the generation of mobile surface oxygen species (O β ). Py-FTIR analysis further revealed that the synergistic interaction between Ni and Co enhanced Lewis acidity by increasing the density of unsaturated cationic sites, explaining why the trimetallic Ni 0.48 Co 0.24 Ce 0.28 -LDO catalyst exhibited the highest Lewis acid content. In-situ DRIFTS demonstrated that both Lewis and Brønsted acid sites promoted the formation of reactive nitrate species, while C 3 H 6 oxidation to formate and acetate intermediates drove the NO X reduction pathway. Based on these results, a reaction mechanism was proposed. Overall, this study provides valuable insights for designing efficient and low-cost catalysts for HC-SCR applications.
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JOURNAL OF THE ENERGY INSTITUTE
·
2018
·
IF 4.217
Shuai-wei Liu,Rui-tang Guo,Xiao Sun,Jian Liu,Wei-guo Pan,Zhi-ling Xin,Xu Shi,Zhong-yi Wang,Xing-yu Liu,Hao Qin
In present study, the poisoning mechanism of Cl on V/TiO 2 catalyst for SCR removal of NOx using NH 3 as the reductant was explored by in situ DRIFT technique. The experimental results revealed that the existence of Cl did not change the SCR reaction mechanism over V/TiO 2 catalyst, which was mainly under the control of both E-R and L-H mechanisms. The deactivation of V/TiO 2 catalyst by Cl was mainly resulted from the inhibited adsorption of NH 3 and NOx species, accompanied by the decrease of the reactivity of adsorbed NH 3 species.
研究领域:
环境科学
·
催化化学
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JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
·
2013
·
IF 2.145
Rui-tang Guo,Wen-long Zhen,Wei-guo Pan,Yue Zhou,Jie-nan Hong,Hong-jian Xu,Qiang Jin,Cheng-gang Ding,Shi-yi Guo
CeO 2 –CuO catalyst prepared by citric acid method was investigated for selective catalytic reduction of NO with NH 3 . The activity of the CeO 2 catalyst was enhanced about 8–27% in the temperature range of 125–225 °C at a space velocity of 28,000 h −1 by the addition of Cu. It was found that the state of Cu species had great impact on the SCR performance of CeO 2 –CuO catalyst. Cu 2+ can enhance the low temperature activity of SCR reaction, while CuO would promote NH 3 oxidation before SCR reaction at high temperature, which would cause the decrease of its high temperature SCR activity.
研究领域:
化学工程
·
环境科学
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2021
·
IF 3.764
Wenshuo Hu,Renzhi Zou,Yi Dong,Yu Zhang,Mingchu Ran,Qi Xin,Yang Yang,Hao Song,Weihong Wu,Shaojun Liu,Chenghang Zheng,Xiang Gao
Enhancement of the low-temperature (LT) performance of selective catalytic reduction (SCR) of NOx with NH3 has been a spotlight in environmental catalysis. Here, we use a bifunctional catalytic system mixing V–W/Ti with an oxidative component, i.e., MnOx/CeO2, to achieve both improved LT-SCR activity and N2 selectivity. An integrated approach of steady-state kinetic measurements, chemical trapping techniques, time-resolved in situ FTIR spectroscopy, and density functional theory (DFT) calculations reveals that such a synergistic enhancement is at a short distance and is significant when V–W/Ti and MnOx/CeO2 are in intimate contact. These findings further suggest a bifunctional LT-SCR pathway mediated by a short-lived, mobile nitrite-precursor intermediate, which is facilely generated on the oxidative component and then communicates with the adjacent SCR phase through reacting with the abundant NH3 adsorbates there. Assembling such a mechanism with commercial SCR catalysts, accordingly, acts as a promising way to enhance the LT-SCR performance.
研究领域:
环境催化
·
材料科学
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高影响因子
CATALYSIS TODAY
·
2018
·
IF 4.667
Chaoqun Bian,Fang Chen,Ling Zhang,Weiping Zhang,Xiangju Meng,Stefan Maurer,Daniel Dai,Andrei-Nicolae Parvulescu,Ulrich Müller,Feng-Shou Xiao
High silica chabazite zeolite (CHA) is very important for selective catalytic reduction of NOx with ammonia (NH 3 -SCR), but its synthesis is time-consuming under conventional hydrothermal conditions (160 °C for 90–120 h). Herein, we report a novel strategy for highly efficient synthesis of CHA zeolite by means of fast crystallization at high temperatures in the absence of water solvent (240 °C for 1.5 h). X-ray diffraction, N 2 -adsorption isotherms, inductively coupled plasma, scanning electron microscopy, 29 Si and 27 Al MAS NMR, as well as thermogravimetry-differential thermal analysis suggest that the samples have high quality. This concept significantly enhances the space-time yields (STY) for CHA zeolite prepared from high-temperature synthesis in the absence of water solvent (almost two orders of magnitude higher than those of conventional hydrothermal synthesis). Moreover, compared with hydrothermal synthesis, the samples obtained from fast crystallization at higher temperatures (Si/Al = 12, 2.0% Cu loading) shows enhanced catalytic performance at 350–550 °C in NH 3 -SCR.
研究领域:
材料化学
·
催化化学
·
无机合成
·
环境化学
·
能源化学
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高影响因子
JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY
·
2024
·
IF 2.8
Bo Wang,Qiaowen Yang,Ting Li,Sifan Cui,Pengqiang Feng,Xuan Hou
BACKGROUND Selective catalytic reduction (SCR) can effectively remove NO x from flue gas in a coal-fired power plant. As the core of SCR technology, the catalyst has a limited lifespan. The process of reducing acid leaching and roasting water leaching can efficiently extract vanadium and tungsten from spent SCR catalyst. For vanadium recovery in solution, the traditional vanadium precipitation process by NH 4 Cl has the disadvantages of consuming high precipitant dosage and producing large amounts of waste water. RESULTS This study focused on the vanadium precipitation process using a solution containing vanadium obtained from adopting some steps to handle the spent SCR catalyst. First, melamine was screened out as the vanadium precipitant. Then, the vanadium precipitation conditions were optimized as follows: solution pH value of 1.0, n (C 3 H 6 N 6 )/ n (V) = 0.8, 110 °C and 30 min. Under the best precipitation conditions, the vanadium precipitation efficiency of melamine can reach 99.32%. Finally, the mechanisms of vanadium precipitation by NH 4 Cl and melamine were discussed, respectively. CONCLUSION The results showed that the vanadium precipitation process by NH 4 Cl followed the chemical reactions between NH 4 + and vanadium ions, while the vanadium precipitation process by melamine followed the redox and complexation reactions which essentially belonged to the types of chemical adsorption. The vanadium precipitation product was roasted at 550 °C for 2 h to obtain the vanadium product. The main component of the vanadium product was V 2 O 5 , with a purity of 93.27 wt%. The total recovery efficiency of vanadium from spent SCR catalyst was 78.24%. © 2024 Society of Chemical Industry (SCI).
研究领域:
环境科学
·
化学工程
·
材料科学
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高影响因子
CATALYSIS LETTERS
·
2020
·Vol. 151
·期 4
·966-979
·
IF 2.482
Liu Qinglong,Yang Jingchao,Luo Mingsheng,Yang Zhi,Zhao Qiuna
Abstract A series of Mn–Ti oxide catalysts were synthesized by the sol–gel method and the effects of different synthesis conditions were investigated in sequence. The microstructures and properties of the catalysts were characterized by using N 2 adsorption–desorption, XRD, SEM, H 2 -TPR, NH 3 -TPD, Raman and XPS. The catalytic performance over Mn–Ti oxide catalysts prepared under different synthesis conditions for the low-temperature SCR of NO with NH 3 were also comparatively evaluated. The results reveal that the calcination temperature and metal source play a significant role in the characteristics and the SCR activities of the catalysts. A relatively low calcination temperature is beneficial to low-temperature SCR activity. Manganese nitrate or manganese acetate as the Mn source combining with tetrabutyl titanate as Ti source can achieve high SCR activities. The excellent low-temperature NH 3 -SCR activity can be ascribed to the appropriate textural properties, amorphous Mn-oxides with equal ratio of Mn 3+ /Mn 4+ , good low-temperature reducibility and abundant surface B-acid sites. Graphic Abstract
研究领域:
环境科学
·
催化化学
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JOURNAL OF HAZARDOUS MATERIALS
·
2019
·
IF 7.65
Guangpeng Yang,Xuesen Du,Jingyu Ran,Xiangmin Wang,Yanrong Chen,Li Zhang,Vladislav Rac,Vesna Rakic,John Crittenden
SCR activity of Cu-SAPO-34 catalyst was reduced by alkali metal ions. The alkali metals ions (Li + , Na + and K + ) have shown irregular influences on Cu-SAPO-34. The order of poisoning strengths under 400 °C was found to be: Na + > K + > Li + , which is not consistent with the basicities of their corresponding metals. Experimental results and calculations showed that the alkali metal ions readily replace H + and Cu 2+ /Cu + ions. These exchanges result in the loss of Brønsted acid sites and migration of isolated Cu 2+ ions in Cu-SAPO-34, which decrease the NH 3 -SCR activity. Both the basicity and ion diameter will affect the exchanging behavior of an alkali ion. Na + and Li + ions will influence both H + and Cu 2+ /Cu + ions but K + ions only preferably replace the H + . We hypothesize that K + cannot enter into a small ring (6-membered ring) to replace a Cu 2+ /Cu + ion because of its large ion diameter. The displaced Cu 2+ /Cu + ions will transfer to adjacent unbonded Al site to form a CuAlO 2 species.
研究领域:
环境科学
·
催化化学
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PubMed
高影响因子
Journal of Physical Chemistry C
·
2015
·
IF 4.772
Weiyuan Yao,Yue Liu,Xiaoqiang Wang,Xiaole Weng,Haiqiang Wang,Zhongbiao Wu
In this paper, a sol–gel made Ce–O–P catalyst (referred to as Ce–O–P-SG) was employed for selective catalytic reduction (SCR) of NOx with NH3, which was directly compared with two other Ce–O–P samples as synthesized via hydrothermal and coprecipitation routes (referred to as Ce–O–P-HT and Ce–O–P-CP, respectively). Experimental results revealed that the Ce–O–P-SG catalyst yielded a more than 90% NO conversion at 200 °C in the presence of 10 vol % H2O, whereas Ce–O–P-HT and Ce–O–P-CP catalysts only showed 50% and 20% NO conversions under the same conditions, respectively. After subjected to a series of characterization technologies (e.g., XRD, BET-BJH, XPS, NH3-TPD, py-IR, and H2-TPR), it was found that more enriched surface Ce(4+) species were formed except for the two main CePO4 phases (monazite and rhabdophane phases) of the Ce–O–P-SG catalyst compared to the other two samples, resulting in the increase of surficial active oxygen ions content. This could lead to an enhancement in surface acidity and redox capacity of the Ce–O–P-SG catalyst, effectively promoting the NH3–SCR activity of the catalyst. Further analyses on SO2 and H2O tolerance revealed that the Ce–O–P-SG possessed a higher sulfur resistance than the other two samples, which could be attributed to the SO2 trapping effect by the abundant active oxygen species over Ce–O–P-SG catalyst.
研究领域:
环境科学
·
催化化学
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JOURNAL OF RARE EARTHS
·
2022
·
IF 4.632
Ningyuan Wang,Xiaoqiang Wang,Yue Liu,Zhongbiao Wu
Traditional vanadium-based selective catalytic reduction (SCR) deNO x catalyst can hardly adapt to the gas conditions (much high NO 2 /NO x ratio at lower temperature) of the start-up and low loading periods for a gas turbine . Therefore, a W–Ti-CeO x catalyst with NO x storage and reduction (NSR) function was developed in this work for gas turbine exhaust NO x elimination. The experimental results reveal that W–Ti-CeO x catalyst exhibits high NO 2 adsorption capacity at relatively low temperature while that is quite low for V–W/TiO 2 . The abundant surface Ce 3+ species can be mainly responsible for its high adsorption ability owing to the reaction between NO 2 and Ce 3+ to form nitrate/nitrite species and NO. Meanwhile, the adsorption capacity of W–Ti-CeO x can easily regenerate at medium–high temperature and NH 3 -SCR reaction. Furthermore, W–Ti-CeO x also shows good NH 3 -SCR activity, which can fulfill the deNO x process at high temperature. The addition of W and Ti into ceria can enhance the surface acidity and redox ability, thereby increasing the SCR activity. This work proposes a novel storage-reduction strategy for NO x elimination throughout the operation of gas turbines.
研究领域:
环境工程
·
催化
·
能源工程
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高影响因子
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