ACS Omega
·
2023
·
IF 4.1
Shasha Huang,Yulong Shan,Xiaoyan Shi,Zhongqi Liu,Qiang Wang,Hong He
In the present work, we report on two passive NOx adsorber (PNA) material candidates: the novel support CeSnOx with and without Pd loading. The NOx adsorption and storage capacities of fresh and hydrothermally aged CeSnOx and Pd/CeSnOx were investigated. The results show that CeSnOx exhibits a rather large NOx uptake and storage capacity (28.9 μmol/g), while the loading of Pd on CeSnOx can further increase the storage capacity to 37.6 μmol/g and affect the desorption temperature of NOx. It was found that the NOx desorption temperature of Pd/CeSnOx was compatible with the efficient operating window of selective catalytic reduction (SCR) catalysts. After a hydrothermal aging treatment at 800 °C for 12 h, the NOx adsorption and storage capacities of CeSnOx and Pd/CeSnOx increased, indicating excellent hydrothermal stability. The interaction of Pd with CeSnOx, the state of Pd species, and the structure of CeSnOx and Pd/CeSnOx are studied by combination of the characterization results.
研究领域:
化学
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材料科学
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环境科学
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DOI
PubMed
高影响因子
ChemCatChem
·
2022
·Vol. 14
·期 17
·e202200476
·
IF 5.497
Shuangxi Li,Weiwei Hu,Ziqiang Xu,Huijun Yu,Tianwei Lan,Lupeng Han,Dengsong Zhang
Graphical Reaction pathway ? More adsorption of NH 3 /NH 4 + species and the higher reactivity with gaseous NO maintain the process of E−R reaction path, leading to a satisfactory SCR activity of K poisoned NbFeVO x /TiO 2 . Whereas the decreased adsorption and reactivity of NH 3 /NH 4 + and NO x restrains the process of L−H reaction path, thus showing inferior SCR activity of K poisoned FeVO 4 /TiO 2 . FeVO 4 -based catalysts with a wide temperature window and high SO 2 tolerance have attracted increasing attention for the selective catalytic reduction of NO x with NH 3 . However, the alkali-resistance of FeVO 4 -based catalysts is still challenging. In this study, the K-resistance of FeVO 4 /TiO 2 was markedly improved via the Nb modification. It was demonstrated that the adsorption and reactivity of NH 3 /NH 4 + and NO x species on K poisoned FeVO 4 /TiO 2 both decreased, which restrained the process of Langmuir-Hinshelwood reaction path. As a comparison, more adsorption of NH 3 /NH 4 + species and the higher reactivity with gaseous NO maintain the process of Eley-Rideal reaction path, leading to a satisifactory SCR activity. This work demonstrated an effective route to improve alkali-resistance via modulating reactivity and reaction path of adsorbed NH 3 /NH 4 + and NO x species over Nb modified vanadate catalysts, which presented a new point for the development of high-performance alkali-resistant SCR catalysts.
研究领域:
环境科学
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催化化学
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DOI
高影响因子
ACS Catalysis
·
2021
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IF 13.084
Dongdong Chen,Huarong Lei,Wuwan Xiong,Ying Li,Xiang Ji,Jia-Yue Yang,Baoxiang Peng,Mingli Fu,Peirong Chen,Daiqi Ye
Phosphorus (P) originating from lubricant oil additives or biofuels is an emerging chemical poison in catalytic systems for automotive exhaust after-treatment. Here, we demonstrate that P-poisoning led to severe deactivation of small-pore Pd-SSZ-13 zeolites (with CHA framework) as passive NOx adsorbers (PNA) and CO oxidation catalysts for cold-start exhaust purification applications. Deactivation mechanisms of P-poisoning were unraveled by comparatively examining the P-free and P-loaded Pd-SSZ-13 zeolites using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), temperature-programmed reduction by hydrogen (H2-TPR), CO pulse adsorption, temperature-programmed desorption using NH3 as a probe molecule (NH3-TPD), ultraviolet/visible light (UV/vis) spectroscopy, and in situ diffuse relectance infrared Fourier transform spectroscopy (DRIFTS). The loss of isolated Pd sites─namely, [Pd(OH)]+ and Pd2+ (located in the eight- and six-membered rings of CHA framework, respectively)─was revealed to be largely responsible for the deactivation of Pd-SSZ-13 in passive NOx adsorption and catalytic CO oxidation. In situ DRIFTS studies using NO or CO as a probe molecule suggest that [Pd(OH)]+ was more susceptible to P-poisoning than Pd2+. Specifically, P-poisoning led to a migration of [Pd(OH)]+ from cationic exchange sites to the zeolite surface, forming inactive metaphosphate (i.e., [Pd(OH)]+PO3–) and bulk PdOx species at high temperatures. In contrast, P-poisoning of Pd2+ sites proceeded via a sequential transformation to [Pd(OH)]+ first, and then to [Pd(OH)]+PO3– and bulk PdOx. This study provides a comprehensive mechanistic understanding on the deactivation of Pd-SSZ-13 by P-poisoning, and may guide the design of high-performance, phosphorus-resistant Pd-zeolite catalysts for cold-start exhaust after-treatment.
研究领域:
催化材料
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环境科学
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化学工程
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DOI
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2025
·
IF 9
Liuyang Yang,Meiqing Shen,Xinhua Li,Liwei Jia,Feng Gao,Wei Li,Xinyu Li,Gurong Shen
Passive NO x adsorbers (PNAs) are promising materials for mitigating cold-start NO x emissions, yet their performance is often limited by poor adsorption kinetics and insufficient hydrothermal durability. Herein, we report a triethanolamine (TEOA)-assisted synthesis strategy for Mn/CeZrO x PNAs that enables highly dispersed MnO x species with strengthened Mn-support interactions. Compared with conventionally prepared Mn/CeZrO x , the TEOA-modified materials exhibit (i) faster NO x adsorption rates during the initial cold-start relevant stage, (ii) a higher nitrate formation rate and a more suitable nitrate decomposition window (200–400 °C) in which the downstream selective catalytic reduction unit utilizing Cu-SSZ-13 SCR catalysts typically displays optimized NO x reduction efficiency, and (iii) enhanced hydrothermal stability with reduced MnO x agglomeration after aging. A combination of spectroscopic and microscopic techniques (XPS, UV–vis, DRIFTS, TEM/EDS) reveal that TEOA modulation promotes uniform MnO x dispersion, increases surface O ads species, and shifts MnO x speciation toward more active states. These structural and chemical modifications collectively account for the improved PNA performance. This work demonstrates a simple yet effective synthesis approach to optimize Mn-based PNAs, providing new insights into the design of thermally robust, precious-metal-free cold-start NO x control materials.
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高影响因子
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
·
2017
·Vol. 19
·期 7
·5333-5342
·
IF 4.123
Shu-xian Wang,Rui-tang Guo,Wei-guo Pan,Ming-yuan Li,Peng Sun,Shu-ming Liu,Shuai-wei Liu,Xiao Sun,Jian Liu
It was well recognized that Pb had a poisoning effect on a SCR catalyst. In this study, the deactivation mechanism of Pb on the Ce/TiO2 catalyst was investigated based on the characterization results of TPD and in situ DRIFT studies. It was found that the addition of Pb on the Ce/TiO2 catalyst not only inhibited the adsorption and activation of NH3 species, but also led to the decrease of the activity of adsorbed NH3 species in the SCR reaction. The adsorption of NOx species and the oxidation of NO by O2 over the Ce/TiO2 catalyst were also suppressed by the addition of Pb, while the reactivity of adsorbed NO2 species did not decrease. Moreover, the results revealed that the NH3-SCR reaction over the Ce/TiO2 catalyst followed both the E–R and L–H mechanisms, while the NH3-SCR reaction over Ce/TiO2-Pb was mainly controlled by the L–H mechanism. The contributions of the L–H mechanism to the SCR reactions over Ce/TiO2 and Ce/TiO2-Pb decreased with increasing reaction temperature. The deactivation of Ce/TiO2-Pb was mainly attributed to the suppressed NH3 adsorption and activation, accompanied by the inhibited NO oxidation and the decrease of Brønsted acid sites.
研究领域:
环境催化
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大气污染控制
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材料化学
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表面科学
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物理化学
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DOI
高影响因子
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