APPLIED CATALYSIS B-ENVIRONMENTAL
·
2024
·
IF 20.2
Chunxue Wang,Zhao Li,Xin Sun,Yuan Li,Lei Shi,Shunzheng Zhao,Kai Li,Ping Ning,Fei Wang
Ag-based catalysts show high activity in NH 3 -selective catalytic oxidation (NH 3 -SCO). The anchoring states of Ag species determines its valence and dispersion, thereby influencing the performance of Ag-based catalysts. Herein, we elucidated that the content and anchoring strength of the hydroxyl (OH) groups on support together affect the anchoring states of Ag. TiO 2 has few OH groups but high anchoring strength, the anchored Ag is in a highly dispersed oxidized state, while the unanchored Ag is aggregated in a metallic state (Ag 0 ), so it presents an unevenly sized dispersion and mainly in oxidized state. SiO 2 has abundant OH groups but weak anchoring, and can excessively agglomerate into large Ag 0 nanoparticles (Ag 0 NPs). Therefore, the introduction of SiO 2 can regulate the anchoring states of Ag on the TiO 2 support, making Ag presents highly dispersed Ag 0 NPs, thus following a reaction mechanism with lower energy barriers and significantly improving the NH 3 -SCO performance.
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF CHEMICAL ENGINEERING
·
2021
·
IF 3.171
Xin Yong,Hong Chen,Huawang Zhao,Miao Wei,Yingnan Zhao,Yongdan Li
The effects of SO 2 on an one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NO x by NH 3 were examined. The addition of SO 2 inhibited NO x conversion significantly below 300 °C, while no effect on NO x conversion was observed above 300 °C. TGA, TPD , and XPS results showed that the deactivation was caused by the formation of (NH 4 ) 2 SO 4 , SO 2 chemisorption on the isolated Cu 2+ ion sites, as well as the formation of CuSO 4 -like species. Among them, the site-blocking effect of (NH 4 ) 2 SO 4 on Cu 2+ was the primary reason for deactivation. Fortunately, 89% of deNO x activity of the poisoned catalyst was recovered after thermal treatment at 500 °C in air, where (NH 4 ) 2 SO 4 was completely decomposed. The activity was further recovered with regeneration temperature increasing to 600 °C, removing the adsorbed SO 2 on the Cu 2+ sites. The regeneration at 600 °C could not recover the activity completely, because of the high stability of CuSO 4 -like species.
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2024
·
IF 20.2
Hongchun Sun,Cui Dong,Chao Feng,Hui Wang,Zhenping Qu
Co 3 O 4 catalysts possess high activity in selective catalytic oxidation of NH 3 (NH 3 -SCO), but the low N 2 selectivity hinders their potential application. To enhance N 2 selectivity, the chemical bonded Nb-O-Co catalyst by the deposition of Nb species onto Co 3 O 4 (Nb/Co 3 O 4 -0.03) is constructed. It shows 100 % NH 3 conversion and 82 % N 2 selectivity at 180°C, and the N 2 selectivity is 2.2-fold higher than that of Co 3 O 4 (38 %). The failure of enhancement in N 2 selectivity for physically mixed Co 3 O 4 and NbO x (NbO x |Co 3 O 4 -0.03) further indicates the crucial role of chemical bonded Nb-O-Co in enhancing N 2 selectivity. In situ diffuse reflectance infrared Fourier transform spectra and NH 3 temperature-programmed desorption results show the formation of new NH 3 adsorption sites. Importantly, intermediates NO - stabled on Nb/Co 3 O 4 -0.03 tends to react with -NH 2 to produce N 2 through internal selective catalytic reduction (iSCR). This work offers insights into enhancing the N 2 selectivity in NH 3 -SCO and advances understanding of iSCR mechanism.
研究领域:
化学工程
·
环境科学
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Yangyang Guo,Yang Zheng,Yue Peng,Tao Yue,Tingyu Zhu
Simultaneous removal of NO x and CO from steel sintering has attracted great attention because it is difficult to balance the catalyst reducibility and surface acidity merely using metal oxides or zeolite catalysts. In this study, a mixed CuMn-HZSM-5 catalyst was prepared via an impregnation method. The optimized sample exhibited excellent performance with 90% NO conversion and 100% CO conversion at 175 °C. The activity window of the catalyst was coincident with the actual demand of sintering flue gas control at 150-250℃. The active component CuMn suppressed the excessive Lewis acid sites on the zeolite support for NH 3 adsorption, while the reducibility of the catalyst also decreased compared with that of pure CuMn metal oxides . This synergistic effect was beneficial for the reduction of NH 3 nonselective oxidation with O 2 . In addition, both the DFT and DRIFTS results revealed that NO conversion was improved by CO introduction at low temperature, since NO could adsorb on the CO-preadsorbed sites for the reduction to N 2 via the O atoms of Mn 3c sites, i.e., adsorbed CO could also serve as a reductant to reduce NO to N 2 , which provides another reaction pathway in SCR reactions. Moreover, the NO 2 − and N 2 O 2 − species were observed in the spectra as key intermediates to oxidize CO to CO 2 , which are also the promoters for CO control.
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
RESEARCH ON CHEMICAL INTERMEDIATES
·
2018
·Vol. 44
·期 5
·3455-3474
·
IF 1.674
Sun Xiao,Guo Rui-tang,Li Ming-yuan,Sun Peng,Pan Wei-guo,Liu Shu-ming,Liu Jian,Liu Shuai-wei
Fe was used as the modifier to improve the performance of CeZr 2 O
x
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 CeZr 2 O
x
, along with the elevated resistance to SO 2 and H 2 O. The characterization results including BET, XRD, H 2 -TPR and NH 3 -TPD confirmed that Fe species in Fe 2 CeZr 2 O
x
catalyst could inhibit the formation of ZrO 2 crystals and lead to higher reducibility and surface acidity. In addition, more Ce 3+ and surface active oxygen species could be detected on Fe 2 CeZr 2 O
x
compared with CeZr 2 O
x
. By means of in situ DRIFT technique, it could be deduced that the SCR reaction process over Fe 2 CeZr 2 O
x
was accelerated mainly through theL–H pathway due to the advanced adsorption of NH 3 and NO
x
species, along with the promoted NO conversion to NO 2 . Therefore, the modification of CeZrO
x
catalyst by Fe had a significant stimulation effect on its low-temperature SCR performance.
研究领域:
催化化学
·
环境科学
✓ 已验证
DOI
高影响因子
PHYSICA SCRIPTA
·
2023
·Vol. 98
·期 11
·115027
·
IF 2.9
Deyang Ning,Jiaxiong He,Junqi Li,Zuoyu Liu,Renjie Liao,Yuanpei Lan,Fan Wang,Zhou Zou
In this work, three synthesis methods including photo-chemical, precipitation and hydrothermal were applied for synthesizing CeO2/TiO2 catalysts, and the catalytic performance including photodegradation degrees for organic pollutant and ammonia selective catalytic reduction (NH3-SCR) for NO removal were investigated. It was found that the photo-chemical synthesized CeO2-TiO2-PC exhibited the best photodegradation ability for methylene blue (MB), which had the degradation ratio of 91.21% and was approximately 23.92% higher than that with the matrix of rutile TiO2. The formed Ce-Ti heterojunction enhanced the separation of e−/h+ and further promoted the photocatalytic properties. Moreover, the CeO2-TiO2-PC, and the CeO2-TiO2-P which synthesized by the precipitation method showed better NH3-SCR properties than that of hydrothermal synthesized CeO2-TiO2-H below 300 °C, while the CeO2-TiO2-H owned an outstanding NH3-SCR performance above 300 °C. The difference on the NH3-SCR properties may be major attributed to the acid sites, pore structures and surface areas on the surface of different catalysts.
研究领域:
环境科学
·
材料科学
·
催化
✓ 已验证
DOI
高影响因子
NANO
·
2019
·
IF 1.293
Qian Sun,Chun Zeng,Meng-Meng Xing,Bo Chen,Dan Zhao,San-Guo Hong,Ning Zhang
Deliberately engineering oxide composites on constructing and manipulating interactive structures particularly in surface layers was highly desirable for heterogeneous catalysis. Herein, upon the redox replacement reaction between Ce(IV) precursor (Ce(NO 3 ) 6 2 − ) and Cu 2 O nano-substrate, an attempt to directly engineer the surface structure of Cu-based substrate was performed by the Ce(IV)–Cu 2 O etching-embedding process, then the obtained powders were thermo-treated to get a series of Ce–O–Cu catalysts with different Ce:Cu molar ratios for NH 3 selective catalytic reduction (NH 3 -SCR) of NO. Characterized by ICP-OES, XRD, Raman, XPS, SEM, BET, H 2 -TPR, NO- and NH 3 -TPD measurements, it was demonstrated that the Cu–O–Ce catalysts were structured as CuO matrix with an interactive surface composed by co-present Cu(I)–Cu(II) and Ce(III)–Ce(IV) species, even the introduction of Ce was confined in a quite low loading range (0.83–2.3 wt.%); such a surface exhibited the distinct synergistic effect with positively manipulated physical-chemistry properties such as active site distributions, redox features and surface reactivity compared to pure CuO and traditional Cu–Ce composite catalyst, leading to attractive catalytic performance such as ≥ 9 0 % NO conversion with ≥ 9 5 % N 2 selectivity and the two-fold TOF enhancement versus traditional catalysts, even SO 2 was present in reactant mixture on well-manipulated catalyst (Ce loading at 1.6 wt.%) These results indicated that the etching-embedding strategy illuminated in this work could be referred as a feasible method to directly engineer and construct interactive oxide composite surface for advanced application as well as current efficient Ce–O–Cu catalytic interface for heterogeneous catalysis.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of the Taiwan Institute of Chemical Engineers
·
2022
·
IF 5.477
Kaiwen Ni,Yuewang Peng,Geyu Dai,Huawang Zhao,Zhiwei Huang,Xiaomin Wu,Guohua Jing,Wei Feng,Ye Yuan
Background Ammonia bisulfate (ABS) deposition on the active sites of the catalyst surface is the main reason for SO 2 poisoning in low-temperature NH3-selective catalytic reduction (SCR). Accelerated ABS decomposition efficiently enhances the SO 2 resistance. Methods In this work, ceria was specifically chosen to decorate V 2 O 5 -WO 3 /TiO 2 catalyst (Ce-VW/Ti) to activate ABS decomposition in low-temperature NH 3 -SCR. Significant findings The optimal 7Ce-VW/Ti catalyst accelerated the decomposition of ABS and had superior SO 2 tolerance at 250°C. The additive CeO 2 improved the specific surface area and surface acidity, favoring the NH 3 -SCR catalytic activity. ABS was preferentially deposited on the additive CeO 2 on the surface of the 7Ce-VW/Ti catalyst and generated cerium sulfate, eventually protecting the active V 2 O 5 sites and TiO 2 support. Moreover, high quantity of V 5+ and charge transfer between active species V 2 O 5 and support TiO 2 could be maintained due to CeO 2 protection, subsequently maintaining the high NH 3 -SCR performance and enhancing the SO 2 tolerance.
研究领域:
催化
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CATALYSIS
·
2024
·
IF 6.5
Yin Che,Xuezhen Liu,Lifei Liu,Yali Du,Xia An,Xu Wu
Arranging an ammonia oxidation process after the selective catalytic reduction of NO x by NH 3 (NH 3 -SCR) system is an effective way for ensuring the DeNO x efficiency and controlling the slip ammonia. To improve operability and reduce operating costs in ammonia selective catalytic oxidation (NH 3 -SCO), developing feasible and efficient catalysts becomes meaningful. Herein, focusing on the dilemma of Ag/Al 2 O 3 catalysts in NH 3 -SCO applications, Ag/MgAlO x catalysts with different support different crystalline phase structures (5 %Ag/MgAl-LDO and 5 %Ag/MgAl 2 O 4 ) were innovatively synthesized and systematically evaluated application potential in NH 3 -SCO. Results indicated that the introduction of Mg apparently broadened reaction temperature window and catalytic performance of 5 %Ag/MgAl 2 O 4 was higher than 5 %Ag/MgAl-LDO, while the N 2 selectivity was completely opposite. The combination of series characterization and density functional theory (DFT) calculations revealed that 5 %Ag/MgAl 2 O 4 surface has more Ag 0 species with small particle size, which is favorable for ammonia adsorption and activated dehydrogenation to further promote reaction of NO x species, resulting in a higher NH 3 -SCO activity. In contrast, 5 %Ag/MgAl-LDO readily induces oxidized Ag species and Ag 0 is more inclined to be present in large particle sizes, which is more conducive to dissociation of O 2 to produce reactive O species (O*) leading to the peroxidation of ammonia to nitrate and thus, positively affects the improvement of N 2 selectivity. Model catalyst 5 %Ag/MgAl-650 (mixed-phase) was prepared by controlling the roasting conditions and exhibited excellent catalytic performance in NH 3 -SCO with almost 93 % of NH 3 oxidized at 250 °C (N 2 selectivity up to 71 %). This work could afford theoretical support for the optimization and application of catalysts with high performance at low temperatures in selective catalytic oxidation of slip ammonia.
研究领域:
环境科学
·
催化材料
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2025
·
IF 13.2
Junfei Chen,Zhihao Yu,Jinwei Wu,Zhao-Bin Ding,Lin Lang,Lining Fang,Xiuli Yin,Zebao Rui
Selective catalytic oxidation of ammonia (NH 3 -SCO) is considered an efficient and environmentally friendly technology to remove trace ammonia pollutants. The Cu-based and Ag-based catalysts have been taken as among the most promising choices for NH 3 -SCO. However, the insufficient NH 3 catalytic activity of Cu-based catalysts and poor N 2 selectivity of Ag-based catalysts restrict their commercial applications. Herein, we report a facile stepwise induced loading method to obtain anatase titania-supported Cu-Ag composite catalysts with well Cu-Ag nanoparticles dispersion and interaction. The enhanced dispersion of Cu-Ag nanoparticles promotes their interaction with TiO 2 support, improves the stability and reducibility of active sites, and finally leads to appropriate chemical states and synergy of the Cu-Ag complex active sites for improving NH 3 conversion and N 2 selectivity. The as-designed CuO x /AgO y /TiO 2 shows outstanding NH 3 -SCO low-temperature catalytic performance with a (>)99 % NH 3 conversion and 83 % N 2 selectivity under 12000 mL g -1 h −1 at 175 °C as well as satisfied long-term stability.
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
Catalysis Science & Technology
·
2020
·Vol. 10
·期 19
·6583-6598
·
IF 5.721
Jialing Chen,Gang Peng,Wei Zheng,Wenbo Zhang,Li Guo,Xiaoqing Wu
A superior Fe-containing MCM-22 zeolite prepared by a one-pot synthesis method (OP-Fe/M22) showed excellent NH3 selective catalytic reduction (NH3-SCR) activity and almost 100% N2 selectivity in a wide temperature window (200–500 °C). To investigate the effects of preparation strategies on the NH3-SCR reaction, other three Fe/MCM-22 zeolites with similar iron content (4.4–4.8 wt%) were prepared by solid-state ion exchange (SSIE-Fe/M22), incipient wetness impregnation (IM-Fe/M22) and mechanical mixing (MM-Fe/M22) methods, respectively. Catalytic results in NH3-SCR demonstrate that OP-Fe/M22 gives significantly higher activity in the whole temperature range (100–550 °C) than the other three post-synthesized catalysts. As revealed by XRD, UV-vis, H2-TPR, NH3-TPD, and Py-IR experiments, OP-Fe/M22 has the highest concentrations of isolated Fe3+ species and acid sites, and the lowest concentration of Fe2O3 nanoparticles among the four catalysts, which ensures its highest activity in the NH3-SCR reaction. Besides, OP-Fe/M22 exhibits the higher activity both in NH3 oxidation and NO oxidation reactions than IM-Fe/M22, indicating the better NO oxidation ability and NH3 storage capacity of OP-Fe/M22 which also facilitates the NH3-SCR process. In contrast with Cu-based MCM-22 zeolite obtained from the incipient wetness impregnation method at similar metal content (5% Cu/M22), OP-Fe/M22 shows comparable activity with 5% Cu/M22 in the low-temperature range (100–300 °C) while obviously higher activity at high temperatures (300–550 °C). Moreover, by removing part of undesired iron oxides in OP-Fe/M22 through mild acid post-treatments, the NH3-SCR activity of OP-Fe/M22 in the medium and high temperature ranges (200–550 °C) can be further improved, suggesting that OP-Fe/M22 is a potential catalyst with highly-efficient NH3-SCR activity in a wide temperature window.
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2024
·
IF 8.1
Yu Zhang,Rui Wang
NH 3 ‑selective catalytic reduction as the fascinating technology for complete NO x removal, the key in practical applications is to explore advanced catalysts with high catalytic reactivity and stability at low temperature. Herein, a series of hollow spherical AMnO x (A = Ce, Cu, Ni) catalysts was fabricated by using carbon nanospheres as sacrificial template. Characterization analysis including XRD, ICP, BET, SEM, TEM, H 2 -TPR, NH 3 -TPD, XPS, in situ DRIFTS together with kinetic studies were applied to acquire knowledge of the morphological structure and surface features of the catalysts as-prepared. We also performed a comparative study on three samples with regard to their SCR activity at low temperatures. Notable, the catalytic activity of the NiMnO x catalyst (95.9 %) was vastly superior to that of the CeMnO x (85.4 %) and CuMnO x (30.5 %) at 100 °C. This enhanced low-temperature activity of NiMnO x are correlated against hollow structure with more active sites, wider pore distribution, higher surface Mn content and the enhancement in surface acidity and reducibility. Even with 5 vol% H 2 O in the reaction gas fraction, the catalytic performance of NiMnO x hollow spheres was superior to the other two catalysts. Besides, it can be used for six consecutive runs without suffering a substantial activity loss. Additionally, the impact of various crucial process variables, including space velocity, H 2 O, SO 2 , and metal poisons, on the denitrification efficiency of NH 3 -SCR was examined. The current researches have a positive guiding role in the development of high-efficiency low-temperature NH 3 -SCR denitrification catalysts to boost NO x degradation.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
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