Abstract
During the catalytic combustion reaction of methane, the migration of the active species on surface facilitates the catalytic reaction, and the element doping can improve the redox performance of the catalyst. Nitrogen-modified perovskite type composite catalysts were prepared by hydrothermal method and then characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), temperature-programmed reductions (TPR), and X-ray photoelectron spectra (XPS). The results revealed that nitrogen sources (urea, biuret, melamine, carbohydrazide, and semicarbazide hydrochloride) and nitrogen source addition changed the catalytic performance in physical and chemical properties, the migration of reactive species and the catalytic performance. When the addition amount of semicarbazide hydrochloride was three times that of LaCoO3, the composite catalysts had high Co3+/Co2+ (1.39) and Oads/Olat (15.18) and showed the best catalytic performance: the temperatures that are required for achieving methane conversion of 50% and 90% were 277 and 360 °C, which are more effective than noble metal oxides. Moreover, the in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) were applied to elucidate the efficient for CH4 removal and also can further explain the surface reaction mechanism of the composite catalyst during the methane catalytic combustion.
Highlights
Catalytic methane (CH4 ) oxidation is an attractive reaction from both scientific research and practical application as it is a model reaction for evaluating catalytic performance, and an effective technology for removing CH4 from devices
We evaluated the effects of nitrogen sources and nitrogen source addition perovskite type composite catalysts in physical and chemical properties, the migration of reactive species, and the catalytic performance
X-ray diffractometer (XRD) patterns in Figure 5 indicate that the orthorhombic phase LaCO3 OH gradually appeared that the catalytic activity of LC-SH5 is lowest of the five samples, scanning electron microscopy (SEM), temperature-programmed reductions (TPR), and X-ray photoelectron spectra (XPS) of LC-SH5 are and the hexagonal crystal system LaCO3 OH weakened with more addition of the nitrogen source
Summary
Catalytic methane (CH4 ) oxidation is an attractive reaction from both scientific research and practical application as it is a model reaction for evaluating catalytic performance, and an effective technology for removing CH4 from devices. La0.7 Ce0.3 CoO3 , and concluded that 3DOM-m La0.7 Ce0.3 CoO3 catalyst exhibited high catalytic activity for methane combustion due to its larger surface area, better low-temperature reducibility, higher oxygen adsorption species concentration, higher surface-to-volume ratio, and unique nanovoid. Ritzmann et al uncover the fundamental details that govern oxygen diffusivity in LaCoO3 , confirming that the spin state of the Co3+ ions critically influences oxygen transport in LaCoO3 [14] It can increase the surface oxygen content of perovskite type catalysts obtaining a high specific surface area to enhanced catalytic activity [15]. The nitrogen addition of perovskite type oxides can make the N3+ into the crystal structure, which caused the formation of oxygen defects (oxygen vacancies) for the loss of O2− , or promoting the increased of catalyst surface high valence metal ion content. The stable activity of composite catalysts for CH4 oxidation suggests that nitrogen modified composite catalysts materials is a feasible strategy to design industrial catalyst for low-temperature CH4 oxidation, avoiding the use of noble metals
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