Hydrodechlorination of chlorophenols with methanol as hydrogen donor over carbon nanotube supported Pd-catalysts

One of the effective methods of degradation and/or removal of chlorophenols, which are persistent environmental pollutants of toxic and resistant to biodegradation, is hydrodechlorination (HDC) via heterogeneous catalysis using liquid hydrogen donors. Here, Pd and Pd-M (M=Zn, Ni, Co) were supported on commercial multiwall carbon nanotubes (MWCNTs) and N-doped MWCNTs (N-MWCNTs), and their catalytic performances for the HDC of 2-chlorophenol (2-CP) using methanol as the hydrogen donor were investigated. The results showed that N-doping and/or the second metal addition to the N-MWCNTs supported Pd catalysts effectively increased their catalytic activity, which is attributed to the modulation of the Pd electronic structure and the improved active hydrogen supply from methanol by introducing the second metal. Particularly, nearly 100% conversion of 2-CP was achieved using Pd-Zn/N-MWCNTs. The catalysts were characterized using TEM, XPS, and XRD techniques to better understand the reaction mechanism, the promotional effects of N-doping in MWCNTs and the addition of second transition metal to the catalyst for the catalytic HDC of 2-CP.