Poly(amic acid) salt-mediated palladium and platinum nanoparticles as highly active and recyclable catalysts for hydrogenation of nitroarenes in water under ambient conditions

摘要

Development of highly active and recyclable catalysts for selective hydrogenation of nitroarenes to amines in water at room temperature is always a challenge in chemical industry. This study reports a facile in situ method for synthesis of ultrafine palladium and platinum nanoparticles (NPs) stabilized by poly (amic acid) salt (PAAS) and their potential as catalysts for hydrogenation of nitroarenes with sodium borohydride or molecular hydrogen as reductant in water at room temperature. In the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride, the activity parameters of PdNPs-PAAS and PtNPs-PAAS catalyst is 6.66 x 10(3) and 5.58 x 10(3) s(-1) M-1 respectively. In the hydrogenation of diverse nitroarenes under atmospheric hydrogen pressure, PdNPs-PAAS shows high activity but poor selectivity toward desired amines in some cases, while PtNPs-PAAS shows both high activity and high selectivity for selective hydrogenation of nitroarenes to corresponding anilines. The high efficiency of nanocatalyst is due to the quasi-homogeneous dispersion of metal NPs and synergistic effects between metal NPs and PAAS. In addition, nanocatalyst can be easily recovered with pH-sensibility of PAAS and reused at least six times without significant loss of catalytic activities.