Abstract
Contamination of waste water and drinking water by nitrate ion is a critical issue in the world. Among various methods used (ex. biological denitration, ion exchange), catalytic reduction of nitrate has one of the highest potential. Although this method has many advantages such as simplicity of management and high rate of reduction, the selectivity to harmless product, N2, is not high enough. Recently, we succeeded to synthesize morphologically controlled cubic Pt nanoparticles (maximum fraction of cubic particles was 70%) by reducing solution under the existence of a structure directing polymer (poly-N-isopropylacrylamide). By using this Pt nanoparticles as catalyst for NO reduction with CH4, we found out that the reaction is structure sensitive and the morphology of Pt nanoparticles has effects on the selectivity of products. Because the mechanism of nitrite reduction may resemble to that of NO reduction by CH4, it is highly possible that the morphology of the Pt nanoparticles can significantly affect the selectivity to reaction products. In this paper, we supported the morphologically controlled Pt nanoparticles on an alumina membrane tube having the average pore diameter of 100 nm and performed nitrite reduction by H2 gas in a counter flow type reactor. The effect of the Pt morphology on the catalytic behavior for NO2-/H2 reaction in aqueous phase will be discussed in the light of experimental results.
