Eliminación de nitratos presentes en agua usando catalizadores de Pt-In/Al2O3

F. ALBANA MARCHESINI; CLAUDIA NEYERTZ; EDUARDO E. MIRÓ; CARLOS QUERINI

Gramado-Brasil

Simposio; XX SICAT – Simpósio Ibero-Americano de Catálise; 2006

FISOCAT

Bimetallic Pt, In catalysts supported on alumina or silica with 1 wt. % of Pt loading and from 1.20% to 0.25% of In were studied in order to test catalytic activity and selectivity of nitrate to N2 reduction in water, using H2 as reducing agent. Alumina supported catalysts displayed higher activity than those supported on silica. The results obtained in a batch reactor indicate that the catalysts with the highest nitrate conversion and the highest selectivity to N2 production are those with the highest Pt/In ratio, which suggests that a Pt-rich intermetallic compound could play a fundamental role in the catalytic reaction. Higher In loadings result in catalysts with lower activity, probably because Pt atoms are covered with In, thus avoiding the H2 dissociation.  However, for the catalyst with an In:Pt ratio of 1:0.25, the most active one, the nitrate conversion becomes almost constant after ca. 100 minutes of reaction reaching 67.7 %; this indicates that some degree of deactivation occurs. Both TPR and XRD characterizations suggest that the deactivation observed could be due to indium oxide segregation, which provokes a decrease in the Pt-In interaction. As for the reaction by-products, maximum concentrations of 2.5 and 23 ppm were obtained for nitrites and ammonia, respectively