Enhanced catalytic reduction of N-nitrosodimethylamine over bimetallic Pd-Ni catalysts
Catalytic reduction of N -nitrosodimethylamine (NDMA) was investigated over γ-Al 2 O 3 supported bimetallic Pd-Ni catalysts (3%(Pd x Ni 1−x )). NDMA could be reduced to dimethylamine over 3%(Pd 0.8 Ni 0.2 ) with a metal-loading-normalized pseudo-first-order rate constant of 836 ± 21 L g me −1 h −1 . Characterization results showed that the reducibility of PdO (or NiO) was improved by addition of Ni (or Pd) in 3%(Pd x Ni 1−x ); Pd-Ni ensembles were formed in 3%(Pd x Ni 1−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%(Pd x Ni 1−x ), indicating high metal dispersion favor NDMA reduction. NDMA reduction over 3%(Pd 0.8 Ni 0.2 ) catalyst could be described by Langmuir-Hinshelwood model, reflecting an adsorption controlled reduction mechanism. The reduction mechanism of NDMA over 3%(Pd 0.8 Ni 0.2 ) catalyst was proposed to be that H 2 was activated by Pd, and H spillover from Pd to Ni/NiO reduced NDMA though N-N cleavage.
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