Catalytic dry reforming of natural gas for the production of chemicals and hydrogen

Carbon dioxide reforming of methane to synthesis gas was studied over Nibased catalysts. It is shown that, in contrast to other Nibased catalysts which exhibit continuous deactivation with timeonstream, the rate over the Ni=La2O3 catalyst increases during the initial 2–3 h of reaction and then tends to be essentially invariable, displaying very good stability. Xray di5raction, hydrogen and CO uptake studies, as well as highresolution TEM indicate that, under reaction conditions, the Ni particles are partially covered by La2O2CO3 species which are formed by interaction of La2O3 with CO2. Catalytic activity occurs at the Ni–La2O2CO3 interface, while the oxycarbonate species participate directly by reacting with deposited carbon, thus restoring the activity of the Ni sites at the interface. XPS and FTIR studies provide evidence in support of this mechanistic scheme. It was also found that methane cracking on Ni sites and surface reaction between deposited carbon and oxycarbonate species are the rate determining steps in the reaction sequence. A kinetic model is developed based on this mechanistic scheme, which is found to predict satisfactorily the kinetic measurements. ? 2003 International Association for Hydrogen Energy. Published by Elsevier Scie