Recyclable and effective Pd/poly(N-isopropylacrylamide) catalyst for hydrodechlorination of 4-chlorophenol in aqueous solution

A thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM) stabilized palladium nanoparticle catalyst was prepared for the hydrodechlorination (HDC) of 4-chlorophenol (4-CP) and the reduction of 4-nitrophenol (4-NP) at mild conditions in aqueous solution. The catalyst was synthesized by NaBH4 reduction method and characterized by transmission electron microscopy (TEM), UV-Visible spectroscopy and gel permeation chromatography (GPC). TEM characterization indicates the highly dispersed Pd nanoparticles (similar to 3 nm) on the surface of PNIPAM. UV-Visible spectroscopy exhibits a low critical solution temperature (LCST) of 34 degrees C for PNIPAM and the cloud-point temperature of 34.5 degrees C for PNIPAM-Pd catalyst in aqueous solution. The catalytic HDC of 4-CP and reduction of 4-NP followed the pseudo-first-order kinetics and the dynamic data were measured. High conversion (>95%) of 4-CP (4-NP) was obtained at the substrate/Pd molar ratio of 100:1 in the homogeneous catalytic system. After reaction, the catalyst could be precipitated and separated from reaction system by slightly increasing the temperature of aqueous solution. The PNIPAM-Pd catalyst can be reused three times with little reduction of HDC activity. (C) 2015 Elsevier B.V. All rights reserved.