Hydrodechlorination activity of catalysts based on nitrogen-doped carbons from low-density polyethylene

Nitrogen-doped carbons (NDCs) were prepared by co-pyrolysis of low density polyethylene (LDPE) and tested in the aqueous phase catalytic hydrodechlorination (HDC) of 4-chlorophenol (4-CP). The NDCs were obtained as clusters of non-porous spherical particles with carbon black-like structure. Pyridine and 1,10-phenanthroline were used as nitrogen precursors. Both precursors allowed incorporating a significant content of nitrogen into the carbon matrix (0.1–1.7%, w), with a preferential allocation at the outer regions in the case of pyridine. Different pyrolysis conditions were tested to address their effect on the amount of nitrogen incorporated to the carbon structure. Nitrogen showed different bonding configurations: pyridine-like, pyrrole-like and quaternary. Those NDCs prepared with phenanthroline showed higher content of quaternary and lower of pyrrolic nitrogen in their structure. The NDCs exhibited some activity in HDC, showing their potential as metal-free catalysts. Pd/NDCs catalysts were also prepared and tested. They yielded a much higher activity than Pd supported on non-doped carbons used as blanks, thus suggesting a synergistic between the NDCs and Pd. The NDCs-supported Pd catalysts prepared from 1,10-phenanthroline exhibited a remarkable activity of 55.6 mmol gPd−1 min−1, which may be related to the higher amount of nitrogen of the support with a higher contribution of quaternary nitrogen species.