Sol-gel process for obtaining pure and mixed oxide zirconia spheres, microspheres and washcoats, useful as catalysts or catalyst support

摘要

Process for obtaining pure or mixed oxide zirconia spheres, microspheres or washcoats consisting of:preparing a zirconium solution in water at a concentration, formally expressed as ZrO₂, equal or lower than 400 g/l, starting from a basic zirconium carbonate additioned of conc. nitric acid up to a molar ratio [NO₃⁻]/[Zr⁴⁺] between 0.8 and 1.1, and eventually preparing one or more solutions of the other oxides when necessary;preparing a sol of zirconium, eventually mixed to other metals, by a thickening agent and, in the case of spheres and microspheres, of a surface active agent too;dripping the sol into an alkaline gelation bath for obtaining gel spheres or microspheres, or sucking the sol into the honeycomb channels in order to obtain the washcoats, with subsequent gelation with gaseous ammonia;ageing the so obtained gel;rinsing with water down to pH = 9-10, only in the case of gel spheres or microspheres;drying and calcining.