In-situ XANES Studies of Ce0.9Zr0.1O2 Nanocatalysts for Total Oxidation of Methane

M.G. ZIMICZ; D.G. LAMAS; R.J. PRADO; LARRONDO S.A.

Campinas

Congreso; 21ª RAU (Reunión Anual de Usuarios del Laboratorio Nacional de Luz Sincrotón); 2011

The catalytic combustion of methane constitutes an alternative to conventional methane thermal combustion to produce energy. This method has the advantage to give the possibility of performing the oxidation reaction at lower temperatures, thus reducing the emissions of NOx. In recent years there has been growing global concern about the rapid increase in emissions of gaseous pollutants and greenhouse gases caused by the growth in energy demand. Under the Kyoto protocol, the reduction of hydrocarbons, CO2 and NOx emissions, and the increase of combustion efficiency, especially in the case of methane and natural gas, have become a central research topic. The aim of this work is to study the catalytic performance of Ce-Zr mixed oxides for the total oxidation of Methane with different techniques. All the solids of nominal composition Ce0.9Zr0.1O2, have nanometric particle sizes, and were synthesized via the nitrate- a-aminoacid combustion process using different a-aminoacids. Catalytic studies were performed in a  Laboratory fixed-bed reactor in the traditional way. Besides, in-situ XANES experiments near the Ce LIII edge were carried out heating the sample with a temperature ramp of 10°C/min and with a feed consisted of Methane(CH4) (2% mol.) and Oxygen (O2) (4% mol), in Helium (He). During these experiments, a mass spectrometer Quadrupole Mass Spectrometer QMS 422 Pfeiffer was connected to the exit in order to register the composition of exhaust gases. In-situ XANES experiments were carried out at the D06A-DXAS dispersive beamline of the Brazilian synchrotron Light Laboratory (LNLS), Campinas, Brazil. The D06A-DXAS dispersive beamline is equipped with a Si(111) monochromator and an image-plate detector to collect the absorption spectra. The comparison of traditional catalytic studies with in-situ XANES results allows following the evolution Ce0.9Zr0.1O2 ratio during the reaction rate at different temperatures and its importance in methane molecule activation.