scholarly journals Effect of Hydrothermal Aging Treatment on Decomposition of NO by Cu-ZSM-5 and Modified Mechanism of Doping Ce against This Influence

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 888 ◽  
Author(s):  
Xiao Yang ◽  
Xiaofei Wang ◽  
Xiaolei Qiao ◽  
Yan Jin ◽  
Baoguo Fan
Keyword(s):  
Flue Gas ◽  
Copper Ions ◽  
Aging Treatment ◽  
Sample Surface ◽  
Decomposition Temperature ◽  
Active Centers ◽  
Hydrothermal Aging ◽  
Exchange Method ◽  
Active Aluminum ◽  
Decomposition Of No

Cu-ZSM-5 and Ce-doped Cu-Ce-ZSM-5 samples were prepared by liquid-phase ion exchange method. The two catalysts were subjected to hydrothermal aging treatment in the simulated flue gas of a coal-fired power station at an ageing temperature of 650–850 °C. The denitration experiment found that the activity of the aged Cu-ZSM-5 was 19.6% to 41% lower than that of the fresh Cu-ZSM-5 at the optimal decomposition temperature of NO at 550 °C, while the aged Cu-Ce-ZSM-5 had only a 14.8% to 31.5% reduction in activity than the fresh Cu-Ce-ZSM-5. The samples were characterized by XRD, BET, H2-TPR, XPS, NO-TPD, etc. The results showed that hydrothermal aging treatment leads to the dealumination of the ZSM-5 framework and reduces the specific surface area and pore volume of the micropore in the sample. It also exacerbates the isolated Cu2+, and the active center {Cu2+-O2−-Cu2+}2+ dimers migrate towards the sample surface and form inactive CuO. Doping with Ce can promote the dispersion of Cu(OH)+, which was the precursor of {Cu2+-O2−-Cu2+}2+. Ce3+ can preferentially occupy the less active bridged hydroxyl exchange sites, so that copper ions occupy the more active aluminum hydroxyl sites, thereby inhibiting the migration of active centers.

scholarly journals The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 99
Author(s):  
Guanghao Cheng ◽  
Gurong Shen ◽  
Jun Wang ◽  
Yunhao Wang ◽  
Weibo Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Aging Time ◽  
Reaction Path ◽  
Aging Treatment ◽  
Hydrothermal Stability ◽  
Hydrothermal Aging ◽  
Strongly Interacting

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.

scholarly journals Fabrication and Characteristics of Mn@ Cu3(BTC)2 for Low-Temperature Catalytic Reduction of NOx with NH3

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Zhuo Yao ◽  
Dianli Qu ◽  
Yuxiang Guo ◽  
Yujing Yang ◽  
Hong Huang
Keyword(s):  
Catalytic Reduction ◽  
Copper Ions ◽  
Structural Characteristics ◽  
Exchange Method ◽  
Pore Sizes ◽  
Structure Surface ◽  
Metal Organic ◽  
Reduction Of Nox ◽  
Reduced Water ◽  
Catalytic Performances

Novel catalysts with high activity for the selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures are highly demanded. In this study, mixed-node metal-organic frameworks (MOFs), e.g. Mn@CuBTC with controlled Mn composition in Cu3(BTC)2, were fabricated using postsynthetic exchange method and their structural characteristics and catalytic performances for NH3-SCR reaction were assessed. A series of analyses in terms of structure, surface morphology, texture, and chemical state determined that Mn ions were successfully incorporated into the Cu3(BTC)2 crystal lattice as well as adsorbed on the walls of nanopores in the framework. The pore sizes can be finely tuned in the presence of Mn ions in the cages, which significantly suppressed water adsorption. The NH3-SCR activity of Mn@CuBTC exhibited nearly 100% NOx conversion rate in the temperature range (230–260°C). The superior NH3-SCR performance is attributed to the proper pore sizes, reduced water content, and the synergistic effect between manganese and copper ions in the MOF structure, which enhanced NH3 bound to the active Lewis sites.

scholarly journals Effect of Ion-Exchange Sequences on Catalytic Performance of Cerium-Modified Cu-SSZ-13 Catalysts for NH3-SCR

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 997
Author(s):  
Yan Wang ◽  
Zhaoqiang Li ◽  
Zhiyong Ding ◽  
Na Kang ◽  
Rongrong Fan ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Copper Ions ◽  
Reduction Process ◽  
Catalytic Performance ◽  
Adsorbed Species ◽  
Exchange Method ◽  
Coordination Environment ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Acidic Sites

Cerium-modified Cu-SSZ-13 catalysts were prepared by an aqueous ion-exchange method, and Ce and Cu were incorporated through different ion-exchange sequences. The results of NH3-SCR activity evaluations displayed that Cu1(CeCu)2 catalyst presented excellent catalytic activity, and over 90% NOx conversion was obtained across the temperature range of 200–500 °C. The characterization results showed that the ion-exchange sequence of Cu and Ce species influenced the crystallinity of the zeolites and the coordination of Al. A small amount of Ce could participate in the reduction process and change the location and coordination environment of copper ions. Furthermore, Ce-modified Cu-SSZ-13 catalysts possessed more acidic sites due to their containing replacement of Ce and movement of Cu in the preparation process. The cooperation of strong redox abilities and NH3 storage capacity led to the increase of active adsorbed species adsorption and resulted in better activity of Cu1(CeCu)2.

Investigation on the stability of copper modification of SAPO-34 catalysts in NH3-SCR reaction after hydrothermal aging

2020 ◽  
Vol 98 (5) ◽  
pp. 236-243
Author(s):  
Xiaoxin Wu ◽  
Jiaxi Peng ◽  
Shaoming Yang ◽  
Wenyuan Xu
Keyword(s):  
Ion Exchange ◽  
Copper Oxide ◽  
Structural Stability ◽  
Solid State Nmr ◽  
Impregnation Method ◽  
Hydrothermal Aging ◽  
Exchange Method ◽  
Nh3 Scr ◽  
Ion Exchange Method ◽  
The Stability

The influence of hydrothermal aging on the structural stability of Cu-modified SAPO-34 prepared by ion-exchange and impregnation methods was studied. XRD, Ar adsorption at −196 °C, solid-state NMR, UV–vis, H2-TPR, and EPR were used to probe the structural properties of the catalysts. It was found that the precipitation of crystalline AlPO4 and SiO2, the appearance of mesopores, the migration of silicon to form siliceous islands, and the formation of copper oxide crystallites occurred in aged catalysts. Furthermore, more siliceous islands and copper oxide crystallites were present in the aged samples prepared by the impregnation method than in those prepared by the ion-exchange method. Therefore, the impregnated catalysts show a much poorer structural stability than the ion-exchanged catalysts, which leads to more serious deterioration in the NH3-SCR reaction after hydrothermal aging.

Study on Catalytic Decomposition of N2O over Modified Zeolites

2012 ◽  
Vol 550-553 ◽  
pp. 145-148
Author(s):  
Xing Yong Liu ◽  
Wei Wei
Keyword(s):  
Ion Exchange ◽  
Metal Ions ◽  
Catalytic Decomposition ◽  
Decomposition Temperature ◽  
Exchange Method ◽  
Ion Exchange Method ◽  
Modified Zeolites

A series of Beta, ZSM-5 and MCM-22 zeolites modified with metal ions (such as Fe 3+ , Co 2+ , Ce 3+ , Ni 2+ and Cu 2+ ) for catalytic decomposition of N2O were prepared by using wet ion exchange method. The effects of different metal ions, the contents of metal ions and silicon aluminum ratio on catalytic decomposition activities of N2O were investigated, respectively. The results indicated that Beta with a SiO2/Al2O3=30 and 1% Fe 3+ have better catalytic decomposition activities to N2O, the completed catalytic decomposition temperature to 35% N2O in the condition of 4000 h-1 GVSH is 350 0 C.

Growth Characteristics of Hydride for Aging Treated U-5.5wt.%Nb Alloy

2014 ◽  
Vol 881-883 ◽  
pp. 87-92 ◽  
Author(s):  
He Fei Ji ◽  
Jiang Rong Yang ◽  
Gui Chao Hu ◽  
Chun Li Jiang
Keyword(s):  
Metal Matrix ◽  
Laser Scanning ◽  
Aging Treatment ◽  
Sample Surface ◽  
Growth Characteristics ◽  
Initial Growth ◽  
Preferential Growth ◽  
Laser Scanning Confocal Microscope ◽  
Before And After

The hydriding behavior of as-quenched U-5.5Nb alloy followed by 400 °C×3h aging treatment has been studied at 100 °C with the hydrogen pressure specially chosen at 1.0 bar. The pitting and initial growth of hydride was in-situ monitored by hot stage microscope. The morphology and positions of hydrides on sample surface were then carefully studied by the laser scanning confocal microscope (LSCM) and scanning electron microscope (SEM) which were also applied for investigating the microstructure changes before and after the aging treatment. It is clearly found that the acicular phase all over the metal matrix caused by the 400 °C, 3 hr heat-treatment determined the preferential growth of the hydride in specific directions.

scholarly journals Screening of Metal Modified HKUST-1 to Enhance Mercury Removal Efficiency

2021 ◽  
Vol 261 ◽  
pp. 02032
Author(s):  
Mingjie Zhang ◽  
Hongzhe Li ◽  
Gang Yang ◽  
Jiahui Yu ◽  
Yipei Chen
Keyword(s):  
Removal Efficiency ◽  
Flue Gas ◽  
Removal Rate ◽  
Sample Surface ◽  
Acid Sites ◽  
Manganese Chloride ◽  
Mercury Removal ◽  
Brønsted Acid Sites ◽  
Common Component ◽  
Brönsted Acid

In this work, HKUST-1 and different metal modified HKUST-1 materials were investigated in Hg0 removal performance under air condition. Results showed that the pristine HKUST-1 only has a mercury removal rate of around 20%. After metal modification of HKUST-1, the removal efficiency was significantly improved. Among different modification materials employed in this study, HKUST-1 modified by manganese chloride exhibited the highest Hg0 removal efficiency of 95% at 250 oC. This value is relatively high compared with most previously reported catalysts. In addition, this study reveals that the enhanced Hg0 removal efficiency results from the increase of Brønsted acid sites on the sample surface, which is vital to Hg0 removal. Furthermore, it is found that SO2 produced little toxicity to Mn(Cl)/HKUST-1 in the presence of O2. This is beneficial to remove Hg0 in the industrial flue gas, where SO2 is a common component. Therefore, Mn(Cl)/HKUST-1 synthesized here is a promising catalyst for Hg0 removal.

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