Enhanced hydrogenation of aromatic rings and hydrocracking of >Car[sbnd]O[sbnd] bridged bonds in the extraction residue from Piliqing subbituminous coal over a magnetic difunctional solid superbase

Abstract

Ni-Mg2Si/attapulgite powder (AP) was prepared by thermally decomposing nickel tetracarbonyl onto the as-synthesized Mg2Si/AP by impregnating Mg2Si onto AP in CCl4. Its catalytic performance was evaluated by the catalytic hydroconversion (CHC) of oxydibenzene (ODB) in n-hexane under different reaction conditions. Both ODB conversion and cyclohexane selectivity are 100 % by the CHC of ODB over Ni-Mg2Si/AP under 3 MPa of initial hydrogen pressure at 240 °C for 4 h. However, almost no ODB was converted without Ni-Mg2Si/AP under the same conditions. The results show that Ni-Mg2Si/AP could activate H2 to biatomic active hydrogen (H⋯H) and H−, resulting in the hydrogenation of aromatic rings (ARs) and the hydrocracking of >CarO bridged bonds (COBBs), respectively. Additionally, the catalyst was also successfully applied in the CHC of extraction residue (ER) from Piliqing subbituminous coal (PSBC) in n-hexane. The group components of the soluble portion (SP) from CHC and non-CHC (NCHC) (SPCHC and SPNCHC) of ER were analyzed with a gas chromatograph/mass spectrometer. The yield (36.4 %) of SPCHC is significantly higher than that (1.8 %) of SPNCHC. More alkyl-substituted arenols (ASAs), anisoles, and methoxy-substitued cresols exist in SPNCHC, while SPCHC contains more normal alkanes (NAs), non-substituted cycloalkanes, alkylcyclohexanes, tetralins, and octahydroanthracenes. NAs are predominant in SPCHC, while ASAs are the most abundant in SPNCHC, indicating that the CHC facilitates the hydrocracking COBBs and hydrogenating ARs. ODB conversion is as high as 91.2 % after recycling 4 times. Therefore, the catalyst might be potential to produce coal-derived chemicals and clean liquid fuels to facilitate coal efficient conversions owing to its high activity, difunctionality, stability, and good recyclability.