Washcoating was the selected method

Washcoating was the selected method for the catalysts deposition on the micromonoliths. The pretreated micromonolithic structures were immersed in a slurry of RuO2/Al2O3 catalyst with the adequate composition and rheological properties. The rheological properties of the slurry were properly adjusted in order to ensure a layered homogeneous deposition and to avoid cracking effects of the layer. First, the RuO2/Al2O3 catalyst was milled in a zirconia jar on a Retsch® PM100 equipment until obtaining a 5m < ø < 10 m particle size. Then, the adequate amount of solid was dispersed in deionised water and the mixture was sonicated using an ultrasonic disperser (Sonicator Misonix) working at 50 W. After that PVA (polyvinyl alcohol),previously dissolved in hot water, was added as tensioactive and colloidal alumina (Nyacol Al20) was also added to improve the stability. The mixture was kept under vigorous stirring for 24 h. The optimized composition of the suspension was 18.2 wt. % catalyst, 11 wt. % PVA, 6.28 wt. % colloidal alumina and distilled water as balance. The viscosity of the final slurry was 7.5 cps and the pH was 6.18. This pH value assures the stability of the slurry, avoiding catalyst particle agglomeration since the measured isoelectric point of the RuO2/Al2O3 solid was 9.5.