JOURNAL OF CATALYSIS
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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
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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
FUEL
·
2019
·
IF 5.128
Han Jiang,Bin Guan,He Lin,Zhen Huang
This study focuses on investigating the influence of Si/Al ratio on the performance of hydrothermally aged Cu/SSZ-13 catalysts prepared by in situ hydrothermal synthesis method. It was found that NH 3 -SCR performance and hydrothermal stability of Cu/SSZ-13 decreased with increasing Si/Al ratio. Fresh and hydrothermally aged Cu/SSZ-13 with Si/Al ratio of 6.5 showed the best SCR activity and N 2 selectivity in a broad temperature of 200–500 °C, in which more than 90% NO x was reduced with superior N 2 selectivity above 95%. The effect of Si/Al ratio on the properties of the physicochemical structure, the change of acidity intensity, and Cu species migration or transformation of the fresh and aged Cu/SSZ-13 catalysts were comprehensively characterized by NH 3 -TPO, NH 3 -TPD, H 2 -TPR, N 2 physisorption, XRD, ICP-AES, and XPS. The increase of the surface CuO species, the decrease of the amount of Cu 2+ in active sites, the chemisorption NH 3 species, the specific surface area, the total pore volume, and the increase of average pore diameter, may be the main reasons for performance deterioration over high-Si/Al-ratio catalysts after hydrothermal aging. Furthermore, in situ DRIFTS indicate that, with the increasing Si/Al ratio, the zeolitic structure was easy to collapse, and that the surface acid sites, the active copper species, as well as the adsorbed surface nitrate, decreased after hydrothermally aged. After hydrothermal aging, the amount of isolated Cu 2+ decreased, and more CuO species were aggregated, mainly coming from the conversion of the unstable isolated Cu 2+ species in D6R or CHA cages. The decrease of isolated Cu 2+ and CuO species aggregation were significant in Cu/SSZ-13 with high Si/Al ratios. The CuO leaded to the instability of the SSZ-13 skeleton structure and NH 3 oxidation promotion, resulting in catalysts deactivation.
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
APPLIED CATALYSIS B-ENVIRONMENTAL
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2019
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IF 14.229
Huawang Zhao,Yingnan Zhao,Mengke Liu,Xianghui Li,Yuhan Ma,Xin Yong,Hong Chen,Yongdan Li
Phosphorus is introduced to modify the Cu-SSZ-13 catalyst via incipient wetness impregnation, with P/Cu-SSZ-13 = 1 and 2 wt.%, and Si/Al = 4, for selective catalytic reduction of NOx with NH 3 . N 2 physisorption and XRD results show the incorporation of phosphorus as phosphate acid enhanced the hydrothermal stability of Cu-SSZ-13 significantly, during hydrothermal aging in 10 vol.% H 2 O/air at 750 °C for 16 h. NMR and Raman results suggest that phosphate ions migrate and coordinate with the framework-bonded Al species, forming a framework silicoaluminophosphate interface, thus impeding further dealumination and structure collapse. Before the hydrothermal aging, the isolated Cu 2+ ions partly interact with the phosphate ions, forming Cu-phosphate species and reducing the SCR performance. Nevertheless, the appropriate content of phosphate ions can prevent the structure collapse caused by the hydrothermal aging, remaining the isolated Cu 2+ ions as well as excellent SCR performance.
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
AICHE JOURNAL
·
2022
·Vol. 68
·期 11
·e17834
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IF 4.167
Wuyuan Liu,Zhaoying Wang,Ming Sun,Jiajian Gao,Lifeng Wang,Zihan Gao,Yingying Xu,Xiangyun Zhao,Cheng Zhang,Lin Yu
A series of CeO 2 modified Cu-SSZ-13 monolith catalysts were prepared by embedding CeO 2 into the washcoat of Cu-SSZ-13 monolith catalyst through solvent combustion method. These CexCu-SSZ-13 catalysts were studied in the selective catalytic reduction (SCR) of NO with NH 3 , among which the Ce2Cu-SSZ-13 catalyst exhibited the best low-temperature activity, hydrothermal stability, and sulfur resistance. The physicochemical properties of the catalysts were characterized using multiple methods. Results showed that the acidity, redox capacity, and ammonia adsorption capacity significantly enhanced after CeO 2 modification, thus leading to the high performance of Ce2Cu-SSZ-13 catalyst. Furthermore, the introduction of CeO 2 induced the fast SCR reaction by promoting the oxidation of NO to NO 2 . Analog calculation suggested that the porous structure generated via solvent combustion in the washcoat effectively increased the diffusion rate of reaction. In situ diffuse reflectance infrared Fourier transform spectroscopy ( in situ DRIFT) analysis showed that Brønsted acid sites were the main active center and the reaction followed Eley–Rideal mechanism.
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
危险品化学品经营许可证（带存储）