Enhanced catalytic reduction of N-nitrosodimethylamine over bimetallic Pd-Ni catalysts

Abstract

Catalytic reduction of N-nitrosodimethylamine (NDMA) was investigated over γ-Al2O3 supported bimetallic Pd-Ni catalysts (3%(PdxNi1−x)). NDMA could be reduced to dimethylamine over 3%(Pd0.8Ni0.2) with a metal-loading-normalized pseudo-first-order rate constant of 836±21Lgme−1h−1.Characterization results showed that the reducibility of PdO (or NiO) was improved by addition of Ni (or Pd) in 3%(PdxNi1−x); Pd-Ni ensembles were formed in 3%(PdxNi1−x) and there was an electronic transfer from Pd to Ni; metal dispersion was affected by the formation of Pd-Ni ensembles and a volcano curve of metal dispersion via Pd/Ni ratio was observed. The activity profiles demonstrated that TOF had a significant positive relationship with metal dispersion of 3%(PdxNi1−x), indicating high metal dispersion favor NDMA reduction.NDMA reduction over 3%(Pd0.8Ni0.2) catalyst could be described by Langmuir-Hinshelwood model, reflecting an adsorption controlled reduction mechanism. The reduction mechanism of NDMA over 3%(Pd0.8Ni0.2) catalyst was proposed to be that H2 was activated by Pd, and H spillover from Pd to Ni/NiO reduced NDMA though N-N cleavage.