Selective catalytic hydroconversion of crude phenols to cyclohexanols over a carbon-based nickel catalyst and separation of condensed arenes from a low-temperature coal tar

Abstract

The dynamic combined strategy consisting of extraction, column chromatography, and catalytic hydroconversion (CHC) was used to prepare cyclohexanol (CH) from crude phenols (CPs) derived from a low temperature coal tar (LTCT) and enrich condensed arenes from the dephenolized fraction. Fluoranthene, anthracene, and pyrene with purities of 92.2, 91.7, and 95.5 %, respectively, were enriched by a combination of extraction and gradient elution in medium pressure preparative liquid chromatograph (MPPLCI) and high pressure preparative liquid chromatograph. CPs obtained by extracting LTCT were catalytically hydroconverted over a nickel supported on a nitrogen-doped carbon material (NDCM) prepared with a nickel-organic framework as the precursor. The mechanism for the CHC of CPs was explored using phenol as the model compound. The results show that phenol was completely converted and the selectivity of CH is up to 99.9 % in n-hexane under initial hydrogen pressure of 3 MPa at 160 °C for 1 h. The characterization of Ni/NDCM and the distribution of the products from the CHC of phenol indicate that Ni/NDCM can strongly adsorb phenol and effectively activate H2 to H···H, which transfer plays a crucial role in hydrogenating the aromatic rings.