Kinetics and Mechanisms of CO Oxidation on Nd_1-xSr_xCoO_3-y Catalysts with Static and Flow Methods

Abstract

Perovskite-type Nd 1-x Sr x CoO 3-y catalysts with various Sr mole fraction were prepared and investigated for the effect of Sr substitution on their catalytic activities in the oxidation of carbon monoxide. Utilizing the static and flow methods, kinetic studies have been carried out between 373 and 523 K. The initial reaction was investigated by the static reactor system using a differential photoacoustic cell, and for the study of reaction stage showing a constant catalytic activity after an initial stage characterized by high reaction rates, the flow reactor system using on-line gas chromatography was employed. The catalytic activity increased with increasing amounts of Sr substitution for Nd in NdCoO 3 compounds, and it also increased with higher reaction temperature within the range of 373-523 K. Kinetic data obtained in an initial reaction stage by CO 2 photoacoustic spectroscopy showed that the reaction partial orders to CO and O 2 were 0.8-0.9 and 0, respectively. In the reaction stage showing a constant catalytic activity after an initial stage, the oxidation was found to be first order with respect to CO and 0.5 order with respect to O 2 . The concentration of oxygen vacancy in the solid catalyst was shown to be the controlling factor for the oxidation of carbon monoxide. According to the experimental results, the mechanisms of the CO oxidation processes are discussed, and it is believed that O 2 adsorbs on the oxygen vacancies (V o x ) formed by Sr substitution while CO adsorbs on the lattice oxygens during the reaction process.

Facile Synthesis, Microstructure, and Gas Sensing Properties of NdCoO3 Nanoparticles

“…Among the mixed valence perovskites, NdCoO 3 stands out as a strong candidate for gas sensors because it has a high sensitivity to gases, mainly carbon monoxide (CO) [20,21]. One reason for the high response in gases is that the oxide crystallizes in a perovskite-type structure, where neodymium ions (Nd 3+ ) are dodecahedrally coordinated, while cobalt has an octahedral coordination but not an integer oxidation state [20].…”

Characteristics and Sensing Properties of the La1-xNdxCo0.3Fe0.7O3 System for CO Gas Sensors

“…exhibits good ability in CO sensing or CO catalytic oxidation. Among them, NdCoO 3 is an excellent sensing material with high sensitivity towards the CO [3][4]. It has been studied for CO sensing and exhibits excellent performances; for example, NdCoO 3 thin film showed a good response (about 15%) for CO concentration until 0.1% and the optimal working temperature was found to be around 300 ∘ C [5].…”

STRUCTURAL AND ELECTRICAL PROPERTIES OF LaCo1-xNixO3

“…Due to the possibility of inducing and controlling spin-state transition of Co ion through chemical substitution, temperature, or external pressure the study of doped cobaltites has become quite interesting. The effect of such doping in many such cobaltites has already been investigated and alkaline-earthdoped LaCoO 3 and NdCoO 3 are extensively used as catalysts, sensors and thermoelectric materials. 2,3 In the present study we have investigated the effect of Ni doping on the structural and electrical transport properties of LaCoO 3 .…”