NO Oxidation (no + oxidation)

Distribution by Scientific Domains

Selected Abstracts

Effects of NO2, CO, O2, and SO2 on oxidation kinetics of NO over Pt-WO3/TiO2 catalyst for fast selective catalytic reduction process

Muhammad Faisal Irfan
The selective catalytic reduction rate of NO with N-containing reducing agents can be enhanced considerably by converting a part of NO into NO2. The enhanced reaction rate is more pronounced at lower temperatures by using an equimolar mixture of NO and NO2. The kinetics of NO oxidation over Pt-WO3/TiO2 catalyst has been determined in a fixed-bed reactor with different concentrations of oxygen, nitric oxide, and nitrogen dioxide in the presence of 8% water. It has been found that the reaction is second order with respect to nitric oxide, first order for oxygen with a third-order rate constant. Also, it is found that there is no effect on the reaction order with an addition of NO2, CO, or SO2. It follows the same second order but the reaction rate is found to be changed. It is observed that in the case of NO2 and SO2, the reaction rate tends to decrease, but it increases with the addition of CO into the feed. 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 613,620, 2006 [source]

The Role of Surface Oxides in NOx Storage Reduction Catalysts

CHEMCATCHEM, Issue 6 2010
Jelena Jelic Dr.
Monte Carlo or bust: First-principles kinetic Monte Carlo simulations are used to examine NO oxidation over Pd(101)/Pd(100). Under typical conditions for NO oxidation in a NOx storage reduction system (600,K, 105,Pa,O2, 100,Pa,NO), turnover frequencies are comparable to those of Pt(111) surfaces, implying that the surface oxide is similar in reactivity to an oxygen-covered metal surface. [source]

Kinetic Reaction Models for the Selective Reduction of NO by Methane over Multifunctional Zeolite-based Redox Catalysts

T. Sowade
Abstract Kinetic measurements of the selective catalytic reduction (SCR) of NO by methane were performed over CeO2/H-ZSM-5, In-ZSM-5, and CeO2/In-ZSM-5 catalysts. The parameter space covered NO, CH4, and O2 concentrations varying from 250 to 1000 ppm, from 500 to 2000 ppm, and from 0.5 to 10,vol.-%, respectively, space velocities between 5000 and 90000 h,1 and temperatures between 573 and 873 K depending on the catalyst activities. With CeO2/In-ZSM-5 an additional series of measurements was performed with moistened feed gas (0.5,10,vol.-% H2O). On the basis of a pseudo-homogeneous, one-dimensional fixed-bed reactor model, the data were fitted to a kinetic model that includes power rate laws for the reduction of NO and for the unselective total oxidation of methane. From analyses of isothermal data sets, almost all reaction orders were found to vary significantly with changing temperature, which indicates that the simple kinetic model cannot reflect the complex reaction mechanism correctly. Nevertheless, the data measured with In-ZSM-5 could be modeled with good accuracy over a wide range of reaction temperatures (150 K) while the accuracy was less satisfactory with the remaining data sets, in particular for data with the moist feed over CeO2/In-ZSM-5. With the latter catalyst it was not possible to represent the data measured in dry and in moist feed in a single model even upon confinement to fixed reaction temperatures. A comparison of the separate models established showed strong changes in the reaction orders in the presence of water, which occur apparently already at a very low water content (,,0.5,vol.-%). The kinetic parameters found are in agreement with earlier conclusions about the reaction mechanisms. With In-ZSM-5, both reaction orders and the activation energy show a rate-limiting influence of NO oxidation on the NO reduction path which is removed by the presence of the CeO2 promoter. A difference in the reaction mechanism over CeO2/In-ZSM-5 and CeO2/H-ZSM-5 is reflected in different kinetic parameters. The differences of the kinetic parameters between dry-feed and moist-feed models for CeO2/In-ZSM-5 reflect adsorption competition between the reactants and water. [source]

Using Acetylene for Selective Catalytic Reduction of NO in Excess Oxygen

Shan-Shan Yu
Abstract Acetylene as a reducing agent for selective catalytic reduction of NO (C2H2 -SCR) was investigated over a series of metal exchanged HY catalysts, in the reaction system of 0.16% NO, 0.08% C2H2, and 9.95% O2 (volume percent) in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 C. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6 reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2 -SCR of NO. The protons in zeolite were crucial to the C2H2 -SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2 -SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO. [source]