Highly active and selective catalytic hydrogenation of p-chloronitrobenzene to p-chloroaniline on Pt@Cu/TiO_2

摘要

It is still a great challenge to achieve trade-off between catalytic activity and selectivity on supported N catalysts for the catalytic hydrogenation of p-chloronitrobenzene. Here through a two-step photodeposition method, bimetallic Pt@Cu/TiO2 catalysts with different Cu contents were synthesized to deal with this problem. For comparison, Pt/TiO2 and Cu/TiO2 were also synthesized using the photodeposition method. Characterization results suggested that Cu was site-specifically deposited on N particle surface and core-shell nanocomposites with N as core and Cu as shell were formed on TiO2. Additionally, electron transfer between N and Cu occurred in bimetallic nanoparticles, resulting in negatively charged N and positively charged Cu. For the catalytic hydrogenation of p-chloronitrobenzene, Pt/TiO2 exhibited the highest catalytic activity but lowest selectivity among the tested catalysts. Bimetallic catalysts with Cu content equal to the monolayer dispersion capacity displayed a slightly lower activity than that of Pt/TiO2 and 100% selectivity to p-chloroaniline. A lower Cu content led to decreased p-chloroaniline selectivity, while a higher Cu content resulted in markedly inhibited catalytic activity despite of 100% p-chloroaniline selectivity. The findings in the present study indicate that Pt@Cu/TiO2 with a monolayer Cu content is a prominent catalyst with high activity and selectivity.