Pt/Al2O3 coated with N-doped carbon as a highly selective and stable catalyst for catalytic hydrogenation of p-chloronitrobenzene to p-chloroaniline

摘要

Selective catalytic hydrogenation of p -chloronitrobenzene on Pt-based catalysts is a green and high-efficient way for p -chloroaniline production. However, supported monometallic Pt catalysts often exhibit undesirable p -chloroaniline selectivity. We herein reported supported Pt catalysts with N-doped carbon (NC) as an overcoating (Pt/Al _(2) O _(3) @NC) to overcome the disadvantage. Three Pt/Al _(2) O _(3) @NC catalysts with different NC coating amounts were prepared by in situ carbonization of an ionic liquid. For comparison, Al _(2) O _(3) coated by NC and Pt/Al _(2) O _(3) coated by SiO _(2) were also prepared. A combination characterization confirmed that the NC overcoating was successfully formed on Pt/Al _(2) O _(3) surface and Pt particles were completely coated by NC layers when ion liquid amount increased to 25 μl per g catalyst. Due to the intimate contact of NC layers and Pt particles Pt-NC heterojunctions were effectively formed on the catalyst surface. For the catalytic hydrogenation of p -chloronitrobenzene, Pt/Al _(2) O _(3) @NC with 25 μl ionic liquid as the NC precursor exhibited 100% selectivity to p -chloroaniline at 100% conversion of p -chloronitrobenzene. A lower ionic liquid amount led to decreased selectivity to p -chloroaniline. Furthermore, no deactivation was observed on Pt/Al _(2) O _(3) @NC during 5 catalytic cycles. The findings in the study demonstrate that coating noble metal catalysts by N-doped carbon is a promising method to enhance the selectivity and stability for catalytic hydrogenation of p -chloronitrobenzene.