Methane catalytic combustion over La-Ce-Mn-O- perovskite prepared using dielectric heating

摘要

In the present work we report on the influence of the preparation method on the physicochemical and catalytic properties of La-Ce-Mn-O- catalysts used for methane combustion. Samples were prepared hydro-thermally using both conventional (CH) and dielectric heating (MH). Catalysts were characterized by N2 adsorption-desorption, X-ray powder diffraction (XRD), temperature-programmed reduction by H2 (H2-TPR) and temperature-programmed desorption-mass spectrometry (TPD-MS). An analysis of XRD and TPR data leads us to conclude that microwave irradiation leads to formation of La_(1-x)Ce_xMnO3 + εCeO2 (x + ε = 0.2), whereas conventional heating leads to CH-LaMnO3 + CeO2 systems. Catalytic combustion of methane without and with 100 ppmv H2S was carried out using a GHSV of 8000 h~(-1) and oxygen-to-methane ratio of 4. Microwave prepared sample was found to be the best both in terms of sulphur tolerance and percent CH4 conversion. The superior catalytic performance of the catalyst prepared using dielectric heating was attributed to a well dispersed cerium oxide species strongly interacting with the LaMnO3 host structure.