Promotional roles of ZrO2 and WO3 in V2O5-WO3/TiO2-ZrO2 catalysts for NOx reduction by NH3: Catalytic performance, morphology, and reaction mechanism

Abstract Recently, because of the increasing demand for natural gas and the reduction of greenhouse gases, interests have focused on producing synthetic natural gas (SNG), which is suggested as an important future energy carrier. Hydrogenation of CO2, the so-called methanation reaction, is a suitable technique for the fixation of CO2. Nickel supported on yttrium oxide and promoted with cobalt were prepared by the wet-impregnation method respectively and characterized using SBET, XRD, FTIR, XPS, TPR, and HRTEM/EDX. CO2 hydrogenation over the Ni/Y2O3 catalyst was examined and compared with Co–Ni/Y2O3 catalysts, Co% = 10 and 15 wt/wt. The catalytic test was conducted with the use of a fixed-bed reactor under atmospheric pressure. The catalytic performance temperature was 350 °C with a supply of H2:CO2 molar ratio of 4 and a total flow rate of 200 mL/min. The CH4 yield was reached 67%, and CO2 conversion extended 48.5% with CO traces over 10Co–Ni/Y2O3 catalyst. This encourages the direct methanation reaction mechanism. However, the reaction mechanism over Ni/Y2O3 catalyst shows different behaviors rather than that over bi-metal catalysts, whereas the steam reforming of methane reaction was arisen associated with methane consumption besides increase in H2 and CO formation; at the same temperature reaction.

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Oxidative decomposition of dichloromethane over sulfated iron titanate catalysts: Catalytic performance and reaction mechanism

Applied Catalysis A General ◽

10.1016/j.apcata.2021.118094 ◽

2021 ◽

Vol 616 ◽

pp. 118094

Author(s):

Hangqi Xia ◽

Hao Zhang ◽

Jinyan Wu ◽

Gong Chen ◽

Wei Sun ◽

...

Keyword(s):

Reaction Mechanism ◽

Catalytic Performance ◽

Oxidative Decomposition ◽

Iron Titanate

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Catalytic performance and reaction mechanism of an iron-loaded catalyst derived from blast furnace slag for the CO-SO2 reaction to produce sulfur

Applied Catalysis A General ◽

10.1016/j.apcata.2020.117810 ◽

2020 ◽

Vol 606 ◽

pp. 117810

Author(s):

Wen Ren ◽

Ping Zhou ◽

Yeshun Tian ◽

Wenlong Wang ◽

Yong Dong ◽

...

Keyword(s):

Blast Furnace ◽

Reaction Mechanism ◽

Blast Furnace Slag ◽

Catalytic Performance ◽

Furnace Slag

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Numerical Investigation on the Intraphase and Interphase Mass Transfer Limitations for NH3-SCR over Cu-ZSM-5

Processes ◽

10.3390/pr9111966 ◽

2021 ◽

Vol 9 (11) ◽

pp. 1966

Author(s):

Shiyong Yu ◽

Jichao Zhang

Keyword(s):

Pressure Drop ◽

Catalytic Reduction ◽

Nox Reduction ◽

Catalytic Performance ◽

No Oxidation ◽

Relative Pressure ◽

Nh3 Scr ◽

Nox Conversion ◽

Nh3 Adsorption ◽

Media Channels

A systematic modeling approach was scrutinized to develop a kinetic model and a novel monolith channel geometry was designed for NH3 selective catalytic reduction (NH3-SCR) over Cu-ZSM-5. The redox characteristic of Cu-based catalysts and the variations of NH3, NOx concentration, and NOx conversion along the axis in porous media channels were studied. The relative pressure drop in different channels, the variations of NH3 and NOx conversion efficiency were analyzed. The model mainly considers NH3 adsorption and desorption, NH3 oxidation, NO oxidation, and NOx reduction. The results showed that the model could accurately predict the NH3-SCR reaction. In addition, it was found that the Cu-based zeolite catalyst had poor low-temperature catalytic performance and good high-temperature activity. Moreover, the catalytic reaction of NH3-SCR was mainly concentrated in the upper part of the reactor. In addition, the hexagonal channel could effectively improve the diffusion rate of gas reactants to the catalyst wall, reduce the pressure drop and improve the catalytic conversion efficiencies of NH3 and NOx.

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The Role of Nitrate on the Sol-Gel Spread Self-Combustion Process and Its Effect on the NH3-SCR Activity of Magnetic Iron-Based Catalyst

Catalysts ◽

10.3390/catal10030314 ◽

2020 ◽

Vol 10 (3) ◽

pp. 314

Author(s):

Xing Ning ◽

Zhi-bo Xiong ◽

Bin Yang ◽

Wei Lu ◽

Shui-mu Wu

Keyword(s):

Nitric Acid ◽

Citric Acid ◽

Sol Gel ◽

Nox Reduction ◽

Combustion Process ◽

Catalytic Performance ◽

Metal Nitrate ◽

Acid Sites ◽

Complexing Agent ◽

Nh3 Scr

Sol-gel spread self-combustion is the burning of the complexing agent in dried gel and the oxidant. Meanwhile, high temperature takes place during the combustion process, which is harmful to the pore structure of the catalyst. The nitrate from metal nitrate precursors as an oxidant could participate in the spread of the self-combustion process. Therefore, the influence of nitrate from metal nitrate on the spread self-combustion of an iron–cerium–tungsten citric acid gel and its catalytic performance of NOx reduction were investigated by removing nitrate via the dissolution of washing co-precipitation with citric acid and re-introducing nitric acid into the former solution. It was found that the removal of nitrate contributes to enhancing the NH3–SCR activity of the magnetic mixed oxide catalyst. The NOx reduction efficiency was close to 100% for Fe85Ce10W5–CP–CA at 250 °C while the highest was only 80% for the others. The results of thermal analysis demonstrate that the spread self-combustion process of citric acid dried gel is enhanced by re-introducing nitric acid into the citric acid dissolved solution when compared with the removal of nitrate. In addition, the removal of nitrate helps in the formation of γ-Fe2O3 crystallite in the catalyst, refining the particle size of the catalyst and increasing its pore volume. The removal of nitrate also contributes to the formation of Lewis acid sites and Brønsted acid sites on the surface of the catalyst compared with the re-introduction of nitric acid. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrates that both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms exist over Fe85Ce10W5–CP–CA at 250 °C with E–R as its main mechanism.

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Metal-organic framework MIL-53(Al): synthesis, catalytic performance for the Friedel-Crafts acylation, and reaction mechanism

Science China Chemistry ◽

10.1007/s11426-015-5359-0 ◽

2015 ◽

Vol 58 (10) ◽

pp. 1544-1552 ◽

Cited By ~ 14

Author(s):

Junlei Yan ◽

Sai Jiang ◽

Shengfu Ji ◽

Da Shi ◽

Hefei Cheng

Keyword(s):

Reaction Mechanism ◽

Metal Organic Framework ◽

Catalytic Performance ◽

Metal Organic ◽

Organic Framework

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Research on Methane Decomposition during Gas Reburning for NOx Reduction

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.356-360.1801 ◽

2011 ◽

Vol 356-360 ◽

pp. 1801-1806

Author(s):

Hai Ping Xiao ◽

Qin Jian Yu ◽

Lei Huang

Keyword(s):

Free Radicals ◽

Reaction Mechanism ◽

Reaction Kinetics ◽

Nox Reduction ◽

Main Reaction ◽

Nox Removal ◽

Factors Influencing ◽

Main Factors ◽

Hydrocarbon Radicals ◽

Reaction Processes

In order to discover main reaction mechanism of CH4 in NOx removal by methane reburning, reactions between CH4 and NOx were simulated from the point of reaction kinetics. Simulating result demonstrated that reaction temperature and excessive air coefficient were main factors influencing DeNOx efficiency. NO could be directly reduced by free radicals including H, HO2, HCCO and O. Firstly, NO was mainly reduced by HO2.Secondly,NO was mainly reduced by H. Hydrocarbon radicals such as CH3, CH2, C2H4, CH2O, C2H6, CH2CO, HCN, HCNO, HNCO were produced in reaction processes as intermediate products. Lots of free radicals were consumed or produced in reaction and led to concentration variation of NO. At the same time, NO could be directly reduced by hydrocarbon radicals such as CH3, CH2.Therefore, hydrocarbon radicals have important influence on removal efficiency of NOx during methane reburning.

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