scholarly journals Kinetics and Langmuir–Hinshelwood mechanism for the catalytic reduction of para-nitrophenol over Cu catalysts supported on chitin and chitosan biopolymers

2021 ◽  
Author(s):  
Chadia Mounir ◽  
Hammou Ahlafi ◽  
Mustapha Aazza ◽  
Hamou Moussout ◽  
Soufiane Mounir
Keyword(s):  
Catalytic Reduction ◽  
Langmuir Hinshelwood Mechanism ◽  
Cu Catalysts ◽  
Chitin And Chitosan

Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

2019 ◽  
Author(s):  
Julian Rudolph ◽  
Christoph R. Jacob
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Zeolite Catalysts ◽  
Reaction Pathways ◽  
Half Cycle ◽  
Computational Results ◽  
Comprehensive Picture ◽  
Cu Catalysts ◽  
Reduction Of Nox

<div> <div> <div> <p>We computationally investigate the mechanism of the reduction half-cycle of the selective catalytic reduction (SCR) of nitrogen oxides with ammonia. We compare both Fe- and Cu-doped zeolite catalysts and aim at exploring all accessible reaction pathways. From our calculations, a comprehensive picture emerges that unifies sev- eral previous mechanistic proposals. We find that both for Fe and for Cu catalysts, different reaction pathways are feasible, but some of the possible reaction pathways differ in these two cases. Our computational results provide a basis for the inter- pretation of in situ spectroscopic investigations that can possibly distinguish the different mechanistic pathways. </p> </div> </div> </div>

scholarly journals Comparative analysis of biological versus chemical synthesis of palladium nanoparticles for catalysis of chromium (VI) reduction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mpumelelo T. Matsena ◽  
Evans M. N. Chirwa
Keyword(s):  
Rate Constant ◽  
Catalytic Reduction ◽  
Anthropogenic Activities ◽  
Cost Effective ◽  
Addition Product ◽  
Pd Nanoparticles ◽  
Product Inhibition ◽  
Chromium Vi ◽  
Langmuir Hinshelwood Mechanism ◽  
The One

AbstractThe discharge of hexavalent chromium [Cr(VI)] from several anthropogenic activities leads to environmental pollution. In this study, we explore a simple yet cost effective method for the synthesis of palladium (Pd) nanoparticles for the treatment of Cr(VI). The presence of elemental Pd [Pd(0)] was confirmed by scanning electron microscope (SEM), electron dispersive spectroscopy and X-ray diffraction (XRD). We show here that the biologically synthesized nanoparticles (Bio-PdNPs) exhibit improved catalytic reduction of Cr(VI) due to their size being smaller and also being highly dispersed as compared to chemically synthesized nanoparticles (Chem-PdNPs). The Langmuir–Hinshelwood mechanism was successfully used to model the kinetics. Using this model, the Bio-PdNPs were shown to perform better than Chem-PdNPs due to the rate constant (kbio = 6.37 mmol s−1 m−2) and Cr(VI) adsorption constant (KCr(VI),bio = 3.11 × 10−2 L mmol−1) of Bio-PdNPs being higher than the rate constant (kchem = 3.83 mmol s−1 m−2) and Cr(VI) adsorption constant (KCr(VI),chem = 1.14 × 10−2 L mmol−1) of Chem-PdNPs. In addition, product inhibition by trivalent chromium [Cr(III)] was high in Chem-PdNPs as indicated by the high adsorption constant of Cr(III) in Chem-PdNPs of KCr(III),chem = 52.9 L mmol−1 as compared to the one for Bio-PdNPs of KCr(III),bio = 2.76 L mmol−1.

Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

2019 ◽  
Author(s):  
Julian Rudolph ◽  
Christoph R. Jacob
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Zeolite Catalysts ◽  
Reaction Pathways ◽  
Half Cycle ◽  
Computational Results ◽  
Comprehensive Picture ◽  
Cu Catalysts ◽  
Reduction Of Nox

<div> <div> <div> <p>We computationally investigate the mechanism of the reduction half-cycle of the selective catalytic reduction (SCR) of nitrogen oxides with ammonia. We compare both Fe- and Cu-doped zeolite catalysts and aim at exploring all accessible reaction pathways. From our calculations, a comprehensive picture emerges that unifies sev- eral previous mechanistic proposals. We find that both for Fe and for Cu catalysts, different reaction pathways are feasible, but some of the possible reaction pathways differ in these two cases. Our computational results provide a basis for the inter- pretation of in situ spectroscopic investigations that can possibly distinguish the different mechanistic pathways. </p> </div> </div> </div>

Efficiently Engineering Cu-Based Oxide by Surface Embedding of Ce for Selective Catalytic Reduction of NO with NH3

NANO ◽  
2019 ◽  
Vol 14 (06) ◽  
pp. 1950079 ◽  
Author(s):  
Qian Sun ◽  
Chun Zeng ◽  
Meng-Meng Xing ◽  
Bo Chen ◽  
Dan Zhao ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Surface Reactivity ◽  
Composite Catalyst ◽  
Composite Surface ◽  
Molar Ratios ◽  
Interactive Surface ◽  
Cu Catalysts

Deliberately engineering oxide composites on constructing and manipulating interactive structures particularly in surface layers was highly desirable for heterogeneous catalysis. Herein, upon the redox replacement reaction between Ce(IV) precursor (Ce(NO[Formula: see text] and Cu2O nano-substrate, an attempt to directly engineer the surface structure of Cu-based substrate was performed by the Ce(IV)–Cu2O etching-embedding process, then the obtained powders were thermo-treated to get a series of Ce–O–Cu catalysts with different Ce:Cu molar ratios for NH3 selective catalytic reduction (NH3-SCR) of NO. Characterized by ICP-OES, XRD, Raman, XPS, SEM, BET, H2-TPR, NO- and NH3-TPD measurements, it was demonstrated that the Cu–O–Ce catalysts were structured as CuO matrix with an interactive surface composed by co-present Cu(I)–Cu(II) and Ce(III)–Ce(IV) species, even the introduction of Ce was confined in a quite low loading range (0.83–2.3[Formula: see text]wt.%); such a surface exhibited the distinct synergistic effect with positively manipulated physical-chemistry properties such as active site distributions, redox features and surface reactivity compared to pure CuO and traditional Cu–Ce composite catalyst, leading to attractive catalytic performance such as [Formula: see text]% NO conversion with [Formula: see text]% N2 selectivity and the two-fold TOF enhancement versus traditional catalysts, even SO2 was present in reactant mixture on well-manipulated catalyst (Ce loading at 1.6[Formula: see text]wt.%) These results indicated that the etching-embedding strategy illuminated in this work could be referred as a feasible method to directly engineer and construct interactive oxide composite surface for advanced application as well as current efficient Ce–O–Cu catalytic interface for heterogeneous catalysis.

Catalytic reduction of nitrates and nitrites in water solution on pumice-supported Pd–Cu catalysts

2000 ◽  
Vol 24 (3-4) ◽  
pp. 265-273 ◽  
Author(s):  
F Deganello ◽  
L.F Liotta ◽  
A Macaluso ◽  
A.M Venezia ◽  
G Deganello
Keyword(s):  
Catalytic Reduction ◽  
Water Solution ◽  
Cu Catalysts ◽  
Supported Pd

Iron oxide-based catalysts for low-temperature selective catalytic reduction of NOx with NH3

2019 ◽  
Vol 35 (2) ◽  
pp. 239-264 ◽  
Author(s):  
Naveed Husnain ◽  
Enlu Wang ◽  
Kai Li ◽  
Muhammad Tuoqeer Anwar ◽  
Aamir Mehmood ◽  
...  
Keyword(s):  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Acid Sites ◽  
Future Research ◽  
Engine Exhaust ◽  
Scr Of No ◽  
Langmuir Hinshelwood Mechanism ◽  
Removal Technology ◽  
And Performance

Abstract Selective catalytic reduction (SCR) is now an established NOx removal technology for industrial flue gas as well as for diesel engine exhaust gas. However, it is still a big challenge to develop a novel low-temperature catalyst for NH3-SCR of NOx, especially at a temperature below 200°C. In the past few years, many studies have demonstrated the potential of iron (Fe)-based catalysts as low-temperature catalysts for NH3-SCR of NOx. Herein, we summarize the recent progress and performance of Fe-based catalysts for low-temperature NH3-SCR of NOx. Catalysts are divided into three categories: single FexOy, Fe-based multimetal oxide, and Fe-based multimetal oxide with support catalysts. The catalytic activity and selectivity of Fe-based catalysts are systematically analyzed and summarized in light of some key factors such as activation energy, specific surface area, morphology, crystallinity, preparation method and precursor, acid sites, calcination temperature, other metal dopant/substitute, and redox property of catalysts. In addition, H2O/SO2 tolerance and the NH3-SCR reaction mechanism over Fe-based catalysts, including Eley-Rideal and Langmuir-Hinshelwood mechanism, are emphasized. Lastly, the perspectives and future research directions of low-temperature NH3-SCR of NOx are also proposed.

scholarly journals A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts

2015 ◽  
Vol 329 ◽  
pp. 490-498 ◽  
Author(s):  
Hai-Ying Chen ◽  
Zhehao Wei ◽  
Marton Kollar ◽  
Feng Gao ◽  
Yilin Wang ◽  
...  
Keyword(s):  
Comparative Study ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
N2o Formation ◽  
Cu Catalysts ◽  
Reduction Of Nox
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