Catalyst development on nanoparticle oxide supports for the water splitting and oxidative coupling of 4-methylpyridine reactions

Catalyst development is a formulation balance for high activity, selectivity, and stability. The three essential components that comprise heterogeneous catalyst are (1) the active component, (2) the support, and (3) additives or promoters. The two reactions, thermochemical water splitting and oxidative coupling of 4-methylpyridine, were studied using nanoparticle oxide supports.;The water splitting reaction requires a temperature of at least 1,500 °C to thermally activate an iron oxide catalyst. The extremely high temperature sinters the catalyst significantly decreasing the surface area. Zirconia and yttria stabilized zirconia are considered high temperature stable materials. In order to improve the stability of iron oxide, it was deposited on zirconia and yttria stabilized zirconia. These iron oxide catalysts were subjected to cyclic reaction experiments which consisted of a thermal heating step to create an oxygen deficient iron oxide followed by feeding water vapor to generate hydrogen. The n-ZrO2 and YSZ supports stabilize the iron oxide on the catalyst's surface by limiting the sintering and in turn providing a consistent hydrogen yield over multiple cycles.;Palladium oxide deposited on nanoparticle alumina (n-Al2O 3 (+)) and titania supports for the oxidative coupling of 4-methylpyridine has yielded highly active catalysts. A series of calcination temperatures were investigated for the nanoparticle titania (n-TiO2) demonstrating the titania phase is important with the the anatase phase having the best yield. The optimum yield of 5wt% Pd/n-TiO2 with a support pretreatment at 450 °C was 2.2 g/g catalyst. A series of additives ceria, zinc oxide, and zirconia were investigated in an attempt to improve the yield. The product yields were dependent on the additive, support, and preparation method showing the delicate balance with the synthesis process and in the formulation. A 5wt% Pd, 5wt% Zr, 90wt% n-Al2O3 (+) catalyst consistently produced a yield of 3.4 g/g catalyst which is the best catalysts reported to date.;Regeneration studies were performed to increase the catalyst life time and increase the yield per catalyst. These catalysts were subjected to a series of temperature treatments under air, helium, and oxygen gas. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) showed a reduction from PdO to palladium metal while diffuse reflectance infrared spectroscopy (DRIFTS) showed carbon deposits on the catalyst's surface. Static air and oxygen with heat restored most of the catalyst activity but the heat treatments caused sintering preventing complete regeneration.