Pd-Cu/AC and Pt-Cu/AC catalysts for nitrate reduction with hydrogen: Influence of calcination and reduction temperatures

摘要

The influence of calcination and reduction temperatures on the catalytic properties of Pd-Cu and Pt-Cu bimetallic catalysts supported on activated carbon for the reduction of nitrates was studied. The catalysts were prepared using different calcination and reduction temperatures, and the respective activities and selectivities for the reduction of nitrates in water with hydrogen were assessed. It was found that the different preparation conditions lead to different catalytic performances. For both catalysts, the activity decreases by increasing calcination and reduction temperatures, whereas the effect on the selectivity is not uniform. For the l%Pd-0.3%Cu (wt.%) catalyst, the nitrate conversion after 5h of reaction varies from 93% (sample calcined at 200 °C and not reduced) to 25% (sample calcined and reduced at 400 °C). The formation of alloys during the preparation of the catalysts is prejudicial for nitrate reduction. In all the preparation conditions tested the Pd-Cu pair is more selective for the transformation of nitrate into nitrogen. All the samples have been characterized by nitrogen adsorption at -196°C, CO adsorption microcaiorimetry, TPR, XRD, XPS and TEM.