CONICET | Buscador de Institutos y Recursos Humanos

The coal combustion fly ash (FA) contains carbon-rich solid residues (char) that can be promising materials for substituting the conventional carbon-based electrocatalysts in electrocatalytic oxygen reduction and evolution reactions (ORR and OER). After concentrating the char, there is still a remaining char-poor FA, which may be a promising material as a new solid acid catalyst for esterification reactions to produce biofuels.Fly ash samples from Portugal, Poland and South Africa from pulverized coal power plants burning local coals, and a Colombian coal in the case of the Portuguese sample, were collected and respective size-fractions (>150 µm, 75-150 µm, 45-75 µm) were obtained after dry sieving separation. FA bulk and respective sized-fractions were organosulfonic functionalized with sulfonic acid groups to study its activity as solid acid catalysts in the esterification of levulinic acid with n-butanol to allow the production of n-butyl levulinate. Comparing with data from literature, all the FA-based catalysts studied allowed an improvement of up to 100 % for n-butyl levulinate (a potential green fuel additive product) in a lower time reaction (2h) with 5 cycles of reusability.The performance of the Portuguese bulk FA sample and four >75 µm size-fractions samples (after dry sieving (1); followed by wet sieving (2); followed by impaction and water vortex and 5 min. ultrasonication (3), and more 10 min. ultrasonication (4)) as OER and ORR electrocatalysts was evaluated by cyclic voltammetry and linear sweep voltammetry in N2- or O2-saturated 0.1 mol dm-3 KOH electrolyte. All the samples showed ORR and OER electrocatalytic activities, with enhancing performances for treated samples. The FA sample obtained after dry and wet sieving, impaction, water vortex and 15 min. ultrasonication exhibited the highest carbon content and the best ORR performance.