Selective catalytic hydroconversion of a low-temperature coal tar-derived crude phenols to cyclohexanol over a nitrogen-doped Co-based catalyst

An extraction-catalytic hydroconversion (CHC)-column chromatography strategy was designed for the CHC of crude phenols to obtain cyclohexanol (CH) and enrich non-substituted condensed arenes (NSCAs) from a low-temperature coal tar (LTCT). Phenanthrene, fluoranthene, and pyrene were enriched with purities of 94.3%, 90.1%, and 96.1%, respectively, by extraction with petroleum ether and methanol and subsequent gradient elution using a medium pressure preparative liquid chromatograph (MPPLC) and high pressure preparative liquid chromatograph. Co supported on a nitrogen-doped carbon material (NDCM) was prepared by one-step pyrolysis of a cobalt-organic framework under N2 atmosphere and crude phenols (CPs) were extracted from the LTCT. CH with a purity of 98.7% was obtained by catalytically hydroconverting CPs over Co/NDCM and subsequent elution using the MPPLC. The mechanism for the CHC of CPs over Co/NDCM was examined using phenol as the LTCT-related model compound. As a result, phenol was completely converted and the CH selectivity reached 97.7% in n-hexane under initial hydrogen pressure of 3 MPa at 140 °C for 3 h. The characterization of Co/NDCM and the distribution of products from the CHC of phenol indicate that Co/NDCM can activate H2 to H···H and the H···H transfer plays a crucial role in hydrogenating aromatic rings.