Materials
·
2019
·Vol. 12
·期 22
·3654
·
IF 2.972
Mingxuan Ma,Xiaoyu Ma,Suping Cui,Tingting Liu,Yingliang Tian,Yali Wang
A series of MCM-41 molecular sieves with different molar ratio of template to silicon were synthesized through hydrothermal synthesis method by using cetyltrimethylammonium bromide (CTAB) as the template, diatomite as the silicon source. By using impregnation method, the Mn-Ce/MCM-41 SCR molecular sieve-based catalysts were prepared. The results observed that when the molar ratio of template to silicon was 0.2:1, the MCM-41 as catalyst carrier has the highest surface area and largest pore volume, it also presented typically ordered hexagonal arrays of uniform channels. The denitration catalytic material based on this carrier has a high number of Lewis acidic sites, and the denitration efficiency can reach more than 93%.
研究领域:
环境催化
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材料科学
·
化学工程
·
大气污染控制
·
无机多孔材料
✓ 已验证
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2020
·
IF 16.683
Shangchao Xiong,Jianjun Chen,Nan Huang,Tao Yan,Yue Peng,Junhua Li
The degradation of catalyst properties, rather than the deposition of NH 4 Cl, was the main reason for the deactivation of the MnCe low-temperature SCR (selective catalytic reduction) catalyst under HCl atmosphere. Cl ions prefer to be located at the oxygen vacancies around Mn cations on the MnCe surface. The adsorbed Cl ions could further promote the formation of oxygen vacancies. Therefore, the active Mn sites on the surface of MnCe would be quickly covered by Cl ions when HCl was present and thus promote the formation of Brønsted acid sites. However, the ionic NH 4 + adsorbed on the Brønsted acid sites of MnCe and MnCe − Cl were not fully utilized in the SCR reaction. Meanwhile, the reactivity of the coordinated NH 3 bonded with Lewis acid sites was significantly restrained by HCl due to the significant inhibition of the redox performance. Overall, HCl could obviously restrain the low-temperature SCR activity of MnCe.
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
FUEL
·
2018
·
IF 4.908
Jian Liu,Rui-tang Guo,Ming-yuan Li,Peng Sun,Shu-ming Liu,Wei-guo Pan,Shuai-wei Liu,Xiao Sun
Mn/TiO 2 catalyst is a promising candidate for future utilization in low-temperature NH 3 -SCR reaction, but its bad resistance to SO 2 is still a great challenge for practical application. In this study, Eu was successfully used as the additive to improve its resistance to SO 2 under SCR conditions, while the pretreatment of Mn/TiO 2 and MnEu/TiO 2 catalyst by SO 2 + O 2 had a strong deactivation effect on them. In situ DRIFT study clarified that the deactivation of Mn/TiO 2 -S (SCR + SO 2 ), Mn/TiO 2 -S (SO 2 + O 2 ) and MnEu/TiO 2 -S (SO 2 +O 2 ) were mainly originated from the inhibited adsorption of NH 3 and NOx species, as well as the formation of a large amount surface sulfate species on them, which had a strong blacking effect on the SCR reactions over the three catalysts via both E-R and L-H routes. After the addition of Eu, SCR reaction over MnEu/TiO 2 catalyst with the existence of SO 2 took place through L-H pathway, accompanied by the generation of less surface sulfate species, which brought about the excellent SO 2 tolerance of MnEu/TiO 2 catalyst under SCR conditions.
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
·
2020
·
IF 16.683
Juan Zhang,Yulong Shan,Ling Zhang,Jinpeng Du,Hong He,Shichao Han,Chi Lei,Sen Wang,Weibin Fan,Zhaochi Feng,Xiaolong Liu,Xiangju Meng,Feng-Shou Xiao
As a commerical catalyst of high silica CHA zeolite for NH 3 -SCR reaction, controllable Al sites in CHA framework for improving catalytic performance are rarely reported. In this work, two organic templates (TMAda + and DMCHA + ) were employed to prepare aluminosilicate CHA zeolite with similar Si/Al ratios, donated as CHA-T and CHA-D. Detailed characterizations demonstrate that two completely distinguishable crystallization pathways can be identified as the preferential formation of smaller D6R units for CHA-D with DMCHA + and larger 8MRs for CHA-T with TMAda + , resulting in spatially closer Al sites in CHA-D than CHA-T. As an interpretation, CHA-D with more paired Al atoms in 6MR generating more hydrothermally stable Cu 2+ -2Z sites contributes to higher activity than CHA-T at 400−550 °C. These results suggest that the crystallization pathways directed by rational choice of organic templates might be responsible for the controllable Al sites in the framework, which is important for designing efficient NH 3 -SCR catalysts.
研究领域:
材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2019
·
IF 8.456
Shanshan Liu,Hao Wang,Ying Wei,Runduo Zhang,Sebastien Royer
ZrO2 supports, with diverse morphologies (hollow sphere, star, rod, mesoporous), were produced using hydrothermal and evaporation-induced self-assembly methods. Zirconia-supported vanadium oxide catalysts were prepared by wet impregnation and used for the low-temperature selective catalytic reduction (SCR) of NO with ammonia. Characterization of catalysts includes N2 physisorption, elementary analysis, X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by H2, and temperature-programmed desorption of NH3. Significant differences in terms of activity are measured. 3 wt % V2O5 supported on mesoporous ZrO2 (V/MZ) presents excellent N2 yields (>90%, in the 200–400 °C interval), with a wide operating temperature window (NO conversion > 95%, in the 225–425 °C interval), and less interesting performances were obtained when vanadium oxide is supported over stars, hollow spheres, and rods. Surface characterization showed a content of tetravalent vanadium ion, when supported, decreasing in the order of mesoporous > hollow sphere > star > rod. This order is in perfect agreement with the order of performance of the catalyst in the NH3-SCR reaction. The impact of tetravalent ion’s presence on the surface is confirmed by diffuse reflectance infrared Fourier transform spectroscopy analysis, Brønsted acid sites generated on the surface, and the V4+-OH species involved in the reaction. The production of more important nitrite species over the tetragonal supported vanadium oxide catalyst could be another reason for the excellent NH3-SCR performance displayed by the V/MZ catalyst. When supported over monoclinic zirconia, like vanadium oxide over star-type morphology, the adsorbed NH3 species (NH4+ and coordinated NH3) reacted with NOx adsorption species (nitrate) to form ammonium nitrate. Ammonium nitrate can be decomposed to N2 and N2O (or NO2). Thus, NO conversion curves and N2 yield curves over tetragonal zirconia (MZ) at lower temperature were ahead of those over V/star ZrO2 because of the higher V4+ surface content and more active B acid sites associated with an easy formation of the nitrito intermediate.
研究领域:
催化化学
·
环境科学
·
材料科学
✓ 已验证
DOI
PubMed
高影响因子
AICHE JOURNAL
·
2019
·Vol. 65
·期 10
·e16684
·
IF 3.463
Lei Song,Kui Ma,Wen Tian,Junyi Ji,Changjun Liu,Siyang Tang,Wei Jiang,Hairong Yue,Bin Liang
A novel FeTiSO x catalyst prepared by a simple hydrolysis coprecipitation method was used for the selective catalytic reduction (SCR) of NO x with NH 3 , which exhibited high catalytic activity (NO x conversion of >97% and N 2 selectivity of >95%) and tolerance for both H 2 O and SO 2 at a broad temperature window of ~325–475°C. The characterization results showed that the formation of Fe–O–Ti and Fe–O–S species could significantly enhance the acidic sites of the catalyst, which play an important role in NH 3 absorption and their catalytic activity. The Fe 3+ ions in the bulk anatase TiO 2 could significantly enhance the redox properties for the SCR reaction and suppress the side reaction of NH 3 oxidation to NO or N 2 O. In addition, the reaction mechanism was discussed based on in situ diffuse reflectance infrared Fourier transform spectroscopy measurements and kinetic investigation, indicating that the reaction was dominated by the Eley–Rideal mechanism over the FeTiSO x catalyst.
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
JOURNAL OF CATALYSIS
·
2021
·
IF 7.92
Yue Ma,Songqi Cheng,Xiaodong Wu,Tongxi Ma,Liping Liu,Baofang Jin,Minghan Liu,Jianbo Liu,Rui Ran,Zhichun Si,Duan Weng
To improve the hydrothermal durability of Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, a thin Al 2 O 3 modification layer was coated on the external surface of Cu-SSZ-13 by a chemical liquid deposition (CLD) method. The high-temperature SCR activity of the Al-modified Cu-SSZ-13 can be maintained upon 750–800 °C hydrothermal aging, and over-oxidation of NH 3 is largely inhibited. Based on H 2 -TPR and EPR results, it is revealed that CuAl 2 O 4 -like species forms upon Al modification and converts further to CuAlO 2 -like species during aging, while the accumulation of CuO-like species is inhibited. The high affinity of Al-containing species ( i.e. , Al 2 O 3 and CuAl 2 O 4 -like species) with Cu(OH) 2 is suggested by DFT calculations, indicating that Cu(OH) 2 detached from ion-exchange sites are captured by Al to form CuAlO 2 -like species instead of CuO-like species. The passivation of detached Cu species by coated Al leads to somewhat weakened low-temperature SCR activity, but successfully preserves the high-temperature SCR performance upon aging, which can be applied to high-temperature SCR scenarios.
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
FUEL
·
2023
·
IF 7.4
Yuxin Sun,Yunshuo Wu,Yarong Bai,Xuanhao Wu,Haiqiang Wang,Zhongbiao Wu
Iridium nanocatalysts are ideal candidates for the selective catalytic reduction of NO x by CO (CO-SCR) in excess oxygen. Here, a high-performance Ir nanocatalyst supported on natural halloysite nanotubes (HNTs) was applied for the CO-SCR. The HNTs loaded with only 0.5 wt% Ir achieved 78 % NO x conversion at 250 °C in the presence of 5 % O 2 , which was the highest among catalysts with varied Ir loadings or reduction temperatures. It also possessed an excellent SO 2 and H 2 O tolerance during longevity tests. An interesting SO 2 -enhanced CO-SCR long-term stability was observed, which was ascribed to the inhibitory effects of SO 2 on the side reaction between CO and O 2 . The loading amount and the reduction temperature could modulate the size of Ir nanoparticles and the percent of Ir 0 , which were two key factors determining the CO-SCR activity. DRIFTS characterizations and DFT calculations coherently revealed the favorable adsorption sites of CO (top) and NO (hcp) on Ir nanoparticles. The Ir atoms served as a charge transfer bridge from the C atom of CO to the N atom of NO, leading to the enhanced breakage of N-O bonds. This work provides Ir/HNT as a promising CO-SCR material with high performance and robustness to tackle NO x pollution.
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
CHEMICAL ENGINEERING JOURNAL
·
2019
·
IF 8.355
Han Jiang,Bin Guan,Xuesong Peng,Reggie Zhan,He Lin,Zhen Huang
This study focuses on investigating the influence of ion-exchange method (ION-F and ION-A) and one-pot method (ONE-F and ONE-A) on catalytic properties and hydrothermal stability of Cu/SSZ-13. It was found that ONE-F catalyst showed better SCR activity, especially at low temperature range below 400 °C. After hydrothermal aging, ION-A exhibited higher low temperature efficiency than ONE-A. The effect of synthesis method on the physicochemical structure, acidity intensity, and Cu species migration or transformation of the fresh and aged Cu/SSZ-13 catalysts were comprehensively characterized by NH 3 -TPO, H 2 -TPR, NH 3 -TPD, ICP, XRF, BET, XRD, SEM, and TEM. ONE-F has more isolated Cu 2+ sites, higher ratio of active sites Cu 2+ -2Z/[Cu(OH)] + -Z, more Lewis acid sites, and smaller particle size than ION-F. However, hydrothermal aging had severe effect on Cu/SSZ-13 prepared by one-pot method, leading to particle aggregation and decrease of active copper sites. According to NH 3 -SCR kinetic studies, smaller particle size and more uniformly distributed active sites over ONE-F resulted in less effect of pore diffusion limitation. Furthermore, in situ DRIFTS results indicated that more monodentate nitrates adsorbed sites and Lewis acid sites existed in ONE-F. On the other hand, monodentate nitrates were identified to be the most active nitrate species, and Lewis acid sites were ascertained to be more active than Brønsted acid sites. Therefore, ONE-F showed more excellent SCR performance than ION-F. However, hydrothermal aging resulted in loss of majority of nitrate adsorbed sites and acid sites over catalyst prepared by one-pot method, leading to lower SCR performance. In conclusion, Cu/SSZ-13 prepared by ion-exchange method has higher hydrothermal stability, however, fresh Cu/SSZ-13 prepared by one-pot method has excellent catalytic properties.
研究领域:
催化材料
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
·
2022
·
IF 7.926
Wei Li,Xuesen Du,Zhi Li,Yaqin Tao,Jingyu Xue,Yanrong Chen,Zhongqing Yang,Jingyu Ran,Vladislav Rac,Vesna Rakić
Vanadia-based catalysts are widely used in selective catalytic reduction (SCR) reaction for reducing nitrogen oxides emissions, however, they only exhibit sufficient DeNO x efficiency within a narrow temperature window. In this study, a catalyst embedded with electrothermal alloy was prepared. The catalyst surface temperature could be heated using the electrothermal alloy, in order to widen the operating temperature window of the V 2 O 5 -WO 3 /TiO 2 catalyst. Experimental results revealed that the electrothermal alloy embedded V 2 O 5 -WO 3 /TiO 2 catalyst can maintain superior NH 3 -SCR performance and high resistance to H 2 O in a wide gas temperature range of 100–400 °C by controlling the surface temperature. In the meantime, the NH 4 HSO 4 poisoned catalyst could be efficiently regenerated through electric heating, and NO x conversion can be restored to the level of fresh samples. Additionally, the effect of additives including methylcellulose and glass fiber , on the physicochemical properties of the plate-type catalyst was also investigated, and the catalyst samples were characterized by means of BET, XRD , NH 3 -TPD, H 2 -TPR, TG and SEM-EDS. This study proves the electric heating strategy is a promising way to enhance the performance of the V 2 O 5 -WO 3 /TiO 2 during wide temperature SCR applications.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
APPLIED CATALYSIS A-GENERAL
·
2018
·
IF 4.521
Li Cao,Lei Chen,Xiaodong Wu,Rui Ran,Tengfei Xu,Ze Chen,Duan Weng
The CeO 2 /TiO 2 catalyst was prepared by a deposition-precipitation method, which exhibited high low-temperature activity under the fast SCR condition. By using transient reaction analysis (TRA), the steps in the fast SCR, including NO 2 adsorption and decomposition, reaction between nitrates and NO, ammonium nitrate formation and reduction by NO, were investigated. Diffuses reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments, via NO + O 2 or NO + NO 2 adsorption, ammonium species reaction with NO x and NO reaction with NH 4 NO 3 , were designed to identify the roles of NO, NO 2 and NH 3 in fast SCR. Based on L-H mechanism, the NH 4 NO 3 formation played an important role in low-temperature SCR reaction. Compared with the behavior in standard SCR, the higher activity in the presence of NO 2 was ascribed to the faster NH 4 NO 3 formation rate and larger amounts of nitrates/nitrites. This phenomenon provided a basis for developing Ce-based catalysts as SCR catalysts for diesel exhaust aftertreatment.
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
Journal of Physical Chemistry C
·
2021
·
IF 4.126
Yanye Zhu,Fangyuan Zhou,Xiaoqiang Wang,Yue Liu,Zhongbiao Wu
The NH3–SCR process could provide cobenefits for VOCs abatement from industrial sources. Ceria-based catalysts have received considerable attention for NOx removal at low-medium temperatures. In this study, the reaction behaviors of the simultaneous control of NOx and methanol over the Sb0.5CeZr2Ox catalyst were investigated. It was found that the presence of methanol reduced NOx conversion at low temperatures, while the methanol mineralization rate was promoted in the SCR reaction environment. This effect weakened as the temperature increased, and both NOx and methanol could be effectively removed (with efficiencies more than 90%) within 250–350 °C at a CH3OH/NO ratio of no more than 1:1. NO adsorption and oxidation were greatly suppressed by methanol, thereby inhibiting the SCR reaction via the Langmuir–Hinshelwood (L-H) mechanism. Meanwhile, the formation of formamide via NH3 and intermediates of methanol oxidation was also responsible for the deactivation effect on the SCR reaction at low temperatures. The presence of NO was found to be the main reason for enhanced methanol deep oxidation as NO can promote the rehealing process of active oxygen 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
危险品化学品经营许可证（带存储）