CATALYSIS TODAY
·
2018
·
IF 4.667
Xianghui Li,Yingnan Zhao,Huawang Zhao,Mengke Liu,Yuhan Ma,Xin Yong,Hong Chen,Yongdan Li
Two kinds of Cu-SAPO-34 catalysts, prepared with a one-pot technique using Cu- tetraethylenepentamine as co-template and an ion-exchange method, were hydrothermally treated at 750 °C for at least 16 h. The migration of Cu species during hydrothermal treatment and the corresponding effect on the selective catalytic reduction (SCR) of NO x were examined and characterized. A certain amount of CuO exists outside and inner the crystallites in the as prepared ion-exchanged sample, whereas copper is mainly atomically dispersed in the one-pot sample existing as isolated Cu 2+ . After hydrothermal treatment for 16 h, the amount of the inner nanosized CuO in the ion-exchanged sample reduced and the copper disperses to form more isolated Cu 2+ . However, surface CuO particles increase at the sacrifice of isolated Cu 2+ with extending the hydrothermal treatment to 24 h. Aggregation of Cu 2+ species also happens during the aging treatment over the one-pot prepared sample where the initial Cu is atomically dispersed as isolated Cu 2+ . The increase of the amount of the isolated Cu 2+ enhances the low-temperature (< 350 °C) performance. However, the increase of the amount of surface CuO particles in the aged samples promotes the nonselective NH 3 oxidation reaction in the high temperature range and results in the lowering of the SCR activity by limiting NH 3 supply.
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
Reaction Kinetics Mechanisms and Catalysis
·
2019
·Vol. 128
·期 2
·1065-1077
·
IF 1.428
Yu Qifan,Liu Xuesong,Chen Hongfeng,Liu Shuang,Jiang Peng
The regeneration mechanism of sulfated Cu/SAPO-34 catalysts in reducing atmospheres (5% H 2 /Ar and NH 3 /Ar at 600 °C) was investigated by using a series of characterization methods. Hydrogen regeneration improved the catalysts’ NH 3 -SCR activity from 150 to 550 °C remarkably, while ammonia regeneration exhibited relatively less obvious promotion effect. The TPR of hydrogen and EPR spectra data show that the regeneration process affects the amount and the coordination of the active isolated Cu 2+ species significantly. The desulfation increases the amount of isolated copper ions and improves the catalytic activity of SCR.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
Journal of Physical Chemistry C
·
2024
·
IF 3.3
Fumei Wang,Qi Cai,Xinhua He,Boxiong Shen,Leila Negahdar,Shuo Feng,Andrew M. Beale
Cu/SAPO-34 catalysts have been widely used for the reduction of NOx from diesel exhaust by ammonia-selective catalytic reduction (SCR). Sulfur poisoning remains a challenge for Cu/SAPO-34 catalysts in NH3–SCR, restricting its application. In this study, Cu/SAPO-34 samples containing a mixture of Cu species comprising isolated Cu2+ located in the 6MR, Cu(OH)+ in 8MR, CuO clusters/nanoparticles, and Cu+ species were prepared. The Cu speciation during SO2 and hydrothermal aging of Cu/SAPO-34 SCR catalysts was subsequently studied. While hydrothermal aging had little effect on catalytic activity, the sulfur-aged sample exhibited deterioration in NH3–SCR activity over the temperature range of 100–575 °C. The breakage and collapse of the zeotype framework and chemical deactivation of the Cu/SAPO-34 catalyst after exposure to SO2 and H2O took place. A combination of X-ray photoelectron spectroscopy (XPS) and TGA-DT-DSC revealed the presence of ammonium bisulfate, copper bisulfate/sulfate, aluminum sulfate, and sulfuric acid after SO2 and H2O copoisoning under SCR conditions. Furthermore, Cu(OH)+ tended to migrate to form isolated Cu2+ and Cu+, as well as agglomerate to form CuO particles. Density functional theory (DFT) calculations revealed that SO2 and O2 could readily be absorbed by CuO particles to form stable copper bisulfate/sulfate species with the following order of preference: CuO > Cu+ > Cu2+ > Cu(OH)+. In contrast, Cu(OH)+ was less prone to be poisoned by easily releasing SO3 than other Cu species sites.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
Journal of Environmental Sciences
·
2016
·
IF 2.208
Jixing Liu,Fuhong Yu,Jian Liu,Lifeng Cui,Zhen Zhao,Yuechang Wei,Qianyao Sun
A series of meso-microporous Cu-SAPO-34 catalysts were successfully synthesized by a one-pot hydrothermal crystallization method, and these catalysts exhibited excellent NH 3 -SCR performance at low temperature. Their structure and physic chemical properties were characterized by means of X-ray diffraction patterns (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N 2 sorption-desorption, nuclear magnetic resonance (NMR), Inductively Coupled Plasma-Atomic Emission spectrometer (ICP-AES), X-ray absorption spectroscopy (XPS), Temperature-programmed desorption of ammonia (NH 3 -TPD), Ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS) and Temperature programmed reduction (TPR). The analysis results indicate that the high activities of Cu-SAPO-34 catalysts could be attributed to the enhancement of redox property, the formation of mesopores and the more acid sites. Furthermore, the kinetic results verify that the formation of mesopores remarkably reduces diffusion resistance and then improves the accessibility of reactants to catalytically active sites. The 1.0-Cu-SAPO-34 catalyst exhibited the high NO conversion (> 90%) among the wide activity temperature window in the range of 150–425°C.
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
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
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）