scholarly journals Poisoning Effects of Alkali and Alkaline Earth Metal Doping on Selective Catalytic Reduction of NO with NH3 over the Nb-Ce/Zr-PILC Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 329
Author(s):  
Chenxi Li ◽  
Jin Cheng ◽  
Qing Ye ◽  
Fanwei Meng ◽  
Xinpeng Wang ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Alkaline Earth ◽  
Catalytic Reduction ◽  
Earth Metal ◽  
Alkaline Earth Metal ◽  
X Ray ◽  
Nh3 Adsorption ◽  
Temperature Programmed ◽  
Redox Ability

The poisoning effects of alkali metals (K and Na) and alkaline earth metals (Ca and Mg) on catalytic performance of the 2Nb4Ce/Zr-PILC catalyst for the selective catalytic reduction of NOx with NH3 (NH3-SCR) were investigated, and physicochemical properties of the catalysts were characterized by means of the X-ray diffraction XRD (XRD), Brunner−Emmet−Teller (BET), hydrogen temperature-programmed reduction (H2-TPR), X-ray Photoelectron Spectroscopy (XPS), ammonia temperature-programmed desorption (NH3-TPD), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) techniques. Doping of M (M = K, Na, Ca, and Mg) deactivated the 2Nb4Ce/Zr-PILC catalyst according to the sequence of 0.8 K > 0.8 Na > 0.8 Ca > 0.8 Mg (M/Ce molar ratio = 0.8). The characterization results showed that the decreases in redox ability, NH3 adsorption, Ce3+/Ce4+ atomic ratio, and amount of the chemisorbed oxygen (Oβ) were the important factors influencing catalytic activities of the alkali metal-and alkaline earth metal-doped samples. Consequently, compared with the Mg- and Ca-doped samples, doping of K caused the 2Nb4Ce/Zr-PILC sample to possess the lowest redox ability, NH3 adsorption, and amount of the Oβ species, which resulted in an obvious deactivation effect.

scholarly journals Effect of SO2 on the Selective Catalytic Reduction of NOx over V2O5-CeO2/TiO2-ZrO2 Catalysts

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2534
Author(s):  
Yaping Zhang ◽  
Peng Wu ◽  
Ke Zhuang ◽  
Kai Shen ◽  
Sheng Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Selective Catalytic Reduction ◽  
Volume Fraction ◽  
Catalytic Reduction ◽  
Surface Measurement ◽  
X Ray ◽  
Nox Conversion ◽  
Nh3 Adsorption ◽  
Reduction Of Nox

The effect of SO2 on the selective catalytic reduction of NOx by NH3 over V2O5-0.2CeO2/TiO2-ZrO2 catalysts was studied through catalytic activity tests and various characterization methods, like Brunner−Emmet−Teller (BET) surface measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), hydrogen temperature-programmed desorption (H2-TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS). The results showed that the catalyst exhibited superior SO2 resistance when the volume fraction of SO2 was below 0.02%. As the SO2 concentration further increased, the NOx conversion exhibited some degree of decline but could restore to the original level when stopping feeding SO2. The deactivation of the catalyst caused by water in the flue gas was reversible. However, when 10% H2O was introduced together with 0.06% SO2, the NOx conversion was rapidly reduced and became unrecoverable. Characterizations indicated that the specific surface area of the deactivated catalyst was significantly reduced and the redox ability was weakened, which was highly responsible for the decrease of the catalytic activity. XPS results showed that more Ce3+ was generated in the case of reacting with SO2. In situ DRIFTS results confirmed that the adsorption capacity of SO2 was enhanced obviously in the presence of O2, while the SO2 considerably refrained the adsorption of NH3. The adsorption of NOx was strengthened by SO2 to some extent. In addition, NH3 adsorption was improved after pre-adsorbed by SO2 + O2, indicating that the Ce3+ and more oxygen vacancy were produced.

Strategies of In Situ Generated Magnesium Catalysis in Asymmetric Reactions

Synlett ◽  
2021 ◽  
Author(s):  
Dongxu Yang ◽  
Linqing Wang
Keyword(s):  
Asymmetric Synthesis ◽  
Alkaline Earth ◽  
Earth Metal ◽  
Asymmetric Reactions ◽  
Chiral Ligands ◽  
Alkaline Earth Metal ◽  
Enantioselective Reactions ◽  
Earth's Crust

AbstractMagnesium (Mg) is a cheap, non-toxic, and recyclable alkaline earth metal that constitutes about 2% weight in the Earth’s crust. The use of magnesium catalysts to forge chiral moieties in molecules is highly attractive. Based on our work in recent years, we describe the current progress in the development of in situ generated magnesium catalysts and their application in asymmetric synthesis. In this perspective, a critically concise classification of in situ generated magnesium catalytic modes, with relevant examples, is presented, and representative mechanisms of each category are discussed. Building on the established diverse strategies, one can foresee that more innovative and structurally creative magnesium catalysts that are generated in situ will be developed to overcome more formidable challenges of catalytic enantioselective reactions.1 Introduction2 Magnesium Catalysts Generated in Situ from Chiral Ligands Containing Dual Reactive Hydrogens3 Magnesium Catalysts Generated in Situ from Monoanionic Chiral Ligands4 Bimetallic and Polymetallic Magnesium Catalysts Assembled in Situ5 Summary and Outlook

Selective catalytic reduction of NO by Co-Mn based nanocatalysts

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Vahid Zabihi ◽  
Mohammad Hasan Eikani ◽  
Mehdi Ardjmand ◽  
Seyed Mahdi Latifi ◽  
Alireza Salehirad
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Energy Dispersive ◽  
Diffraction Field ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
Acidic Sites ◽  
Temperature Window ◽  
Temperature Programmed

Abstract One of the most significant aspects in selective catalytic reduction (SCR) of nitrogen oxides (NOx) is developing suitable catalysts by which the process occurs in a favorable way. At the present work SCR reaction by ammonia (NH3-SCR) was conducted using Co-Mn spinel and its composite with Fe-Mn spinel, as nanocatalysts. The nanocatalysts were fabricated through liquid routes and then their physicochemical properties such as phase composition, degree of agglomeration, particle size distribution, specific surface area and also surface acidic sites have been investigated by X-ray diffraction, Field Emission Scanning Electron Microscope, Energy-dispersive X-ray spectroscopy, energy dispersive spectroscopy mapping, Brunauer–Emmett–Teller, temperature-programmed reduction (H2-TPR) and temperature-programmed desorption of ammonia (NH3-TPD) analysis techniques. The catalytic activity tests in a temperature window of 150–400 °C and gas hourly space velocities of 10,000, 18,000 and 30,000 h−1 revealed that almost in all studied conditions, CoMn2O4/FeMn2O4 nanocomposite exhibited better performance in SCR reaction than CoMn2O4 spinel.

Insights into sulfur poisoning and regeneration of Cu-SSZ-13 catalysts: In situ Cu and S K-edge XAS studies

2021 ◽  
Author(s):  
Vitaly Mesilov ◽  
Sandra Dahlin ◽  
Susanna Liljegren Bergman ◽  
Peter Sams Hammershøi ◽  
Shibo Xi ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Catalytic Reduction ◽  
Sulfur Poisoning ◽  
X Ray ◽  
Scr Catalysts ◽  
X Ray Absorption

In situ Cu and S K-edge X-ray absorption spectroscopy (XAS) was used for the investigation of sulfur-poisoned and regenerated Cu-SSZ-13 selective catalytic reduction (SCR) catalysts. Sulfur in the oxidation state...

scholarly journals Effect of Organic Assistant on the Performance of Ceria-Based Catalysts for the Selective Catalytic Reduction of NO with Ammonia

Catalysts ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 357 ◽  
Author(s):  
Huang ◽  
Li ◽  
Qiu ◽  
Chen ◽  
Cheng ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Ball Milling ◽  
Catalytic Reduction ◽  
Temperature Programmed Desorption ◽  
Milling Process ◽  
X Ray ◽  
Ball Milling Process ◽  
Nh3 Scr ◽  
Temperature Programmed ◽  
Catalytic Performances

In the present study, a series of CeO2/TiO2 catalysts were fabricated by dry ball milling method in the absence and presence of organic assistants, and their catalytic performances for the selective catalytic reduction (SCR) of NO by NH3 were investigated. It was found that the addition of organic assistants in the ball milling process and the calcining ambience exerted a significant influence on the catalytic performances of CeO2/TiO2 catalysts. The nitrogen sorption isotherm measurement (BET), powder X-ray diffraction (XRD), Raman spectra, high-resolution transmission electron microscopy (HR-TEM), hydrogen temperature-programmed reduction (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), sulfur dioxide temperature-programmed desorption (SO2-TPD), thermogravimetric analysis (TG), Fourier transform infrared (FT-IR) and X-ray photoelectron spectra (XPS) characterizations showed that the introduction of citric acid in the ball milling process could significantly change the decomposition process of the precursor mixture, which can lead to improved dispersion and reducibility of cerium species, surface acidity as well as the surface microstructure, all which were responsible for the high low temperature activity of CeTi-C-N in an NH3-SCR reaction. In contrast, the addition of sucrose in the milling process showed an inhibitory effect on the catalytic performance of CeO2/TiO2 catalyst in an NH3-SCR reaction, possibly due to the decrease of the crystallinity of the TiO2 support and the carbon residue covering the active sites.

scholarly journals Nanosized V-Ce Oxides Supported on TiO2 as a Superior Catalyst for the Selective Catalytic Reduction of NO

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 202
Author(s):  
Long Lu ◽  
Xueman Wang ◽  
Chunhua Hu ◽  
Ying Liu ◽  
Xiongbo Chen ◽  
...  
Keyword(s):  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Photoelectron Spectroscopy ◽  
Catalytic Reduction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Redox Capacity ◽  
Scr Of No ◽  
Temperature Programmed

Nanosized V-Ce oxides supported on TiO2 (VCT) were prepared and utilized in the low-temperature selective catalytic reduction (SCR) of NO with NH3. Compared with the other V-Ce oxides-based catalysts supported on Al2O3, ZrO2, and ZSM-5, VCT showed the best SCR activity in a low-temperature range. The NOx conversion of 90% could be achieved at 220 °C. Characterizations including X-ray diffraction (XRD), scanning election micrograph (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption with NH3 (NH3-TPD), and temperature-programmed reduction with H2 (H2-TPR) showed that V1.05Ce1/TiO2 exhibited a good dispersion of V2O5, enrichment of surface Ce3+ and chemical-absorbed oxygen, and excellent redox capacity and acidity, which resulted in the best SCR performance at low temperature.

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