Abstract

Mono- and bimetallic catalysts have been evaluated in the catalytic reduction of NO2 and NO3. The activity and selectivity of the catalysts based on Pd, Pd-In and Pd-Sn supported on different materials such as basic Al2O3, SiO2 and SnO2 have been evaluated under mild operation conditions (25 °C, 1 atm). NO2 hydrogenation was efficiently achieved with monometallic Pd catalyst supported on SnO2 and the bimetallic Pd-In catalysts supported on Al2O3 and SiO2 which led to the highest NO2 conversion (80%). Pd/SnO2 and bimetallic Pd-In supported catalysts completely transformed NO3 while Pd-Sn catalyst showed a lower activity. Initial rates between 0.5 and 2.6 mmol·min−1·gPd−1 were obtained for NO3 reduction. The lowest selectivity to NH4+ was observed with the Pd-In/Al2O3 catalyst, which also showed a high stability in long-term experiments. The operation at low relative H2 fractions in the gas feed greatly diminishes the selectivity to NH4+, reaching concentrations below the maximum concentration allowed in drinking water (0.5 mg/L).

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