Catalytic Hydrogenation of Aqueous Nitrate over Pd−Cu/ZrO2 Catalysts

ZrO 2 supports with different properties were prepared, and the hydrogenation of aqueous nitrate catalyzed by ZrO 2 supported Pd−Cu bimetallic catalysts was investigated. The results showed that ZrO 2 support calcined at 573 K was unstable during the preparation of the bimetallic catalyst. Increasing calcination temperature led to the increase of particle size of ZrO 2 support. In addition, using ZrO 2 calcined at 973 K as the support resulted in the increase of metal particle sizes and the increased content of bimetallic ensembles at the expense of monometallic Pd. The bimetallic catalyst with ZrO 2 calcined at 773 K as the support exhibited higher catalytic activity and N 2 selectivity for the reduction of aqueous nitrate as compared to the bimetallic catalyst with ZrO 2 calcined at 573 or 973 K as the support. The activity and selectivity of ZrO 2 supported bimetallic catalysts for nitrate reduction also depended on the Pd/Cu ratio. Decreasing Pd/Cu ratio led to the decrease of the amount of monometallic Pd sites and to the increase of the content of Pd−Cu ensembles. The bimetallic catalyst with Pd/Cu ratio of 4/1 showed the optimum activity and N 2 selectivity for the reduction of aqueous nitrate.