Synthesis, characterization and testing of catalysts for the methanation and steam reforming of methane reactions

This work of thesis is focused on the synthesis, characterization and testing of Ni-based catalysts supported on the ZrO2, Ce34Zr66O2, Ce33Zr63Pr4O2 mixed oxides to conduct the reactions of carbon dioxide methanation and steam reforming of methane at low temperature. The catalysts are prepared employing the water-in-oil synthetic technique through the incipient wetness impregnation and bulk methods to evaluate the differences resulting from their performance in a fixed-bed plant. The different supports are compared as well to investigate the effect of the Ce and Pr addition on the oxygen storage capacity of the catalysts and the consequent yields and conversions of methane. The testing of a Ni-impregnated catalyst synthetized at the ICPEES-CNRs of Strasbourg with similar conditions as the ones employed in the laboratory of Bologna constitutes a further comparison to analyze in this work. Several characterization techniques are employed to correlate the structural properties of the samples to their performance in the plant. The comparisons show the bulk-synthetized-samples to achieve higher methane yields with respect to the incipient wetness impregnated ones even though they are significantly subjected to the sintering phenomena that can cause a severe loss of activity. The methane conversion as well shows consistently higher values if the reaction is performed with the bulk-synthetized catalysts, in particular an increasing trend is individuated corresponding to a progressively enhanced oxygen storage capacity that permits to overcome the carbon formation on the catalytic sites. Eventually, the interaction between the support and the active phase is thought to represent the fundamental parameter to consider to achieve higher activities in both of the reactions together with the specific selectivity towards the products.