Catalytic hydroconversion of methanol-soluble portion from Xiaolongtan lignite over difunctional Ni/Z5A

A highly active difunctional supported nickel catalyst Ni/Z5A was prepared by thermally decomposing nickel carbonyl onto zeolite 5A (Z5A). The catalytic hydroconversion (CHC) of methanol-soluble portion (MSP) from the methanolysis of Xiaolongtan lignite was investigated over Ni/Z5A at 200 °C. Detailed molecular compositions of MSP and catalytically hydrogenated MSP (CHMSP) were characterized with a Fourier transform infrared spectrometer, gas chromatograph/mass spectrometer (GC/MS), and negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESIFTICRMS). According to analysis with GC/MS, MSP is rich in aromatic ring- and/or heteroatom-containing compounds, while most of the GC/MS-detectable compounds in CHMSP are chain alkanes and cyclanes. The analysis with ESIFTICRMS shows that both the number and yields of oxygen- and/or nitrogen-containing species in MSP were dramatically reduced after the CHC. These facts indicate that Ni/Z5A effectively catalyzed heteroatom (especially O atom) removal from MSP and hydrogenation of MSP. Naphth-1-ol and oxybis(methylene)dibenzene (OBMDB) were used as lignite-related model compounds and their CHCs were investigated to further understand the catalysis of Ni/Z5A in the CHC of MSP. As a result, Ni/Z5A proved to have 2 functions, i.e., activating H2 to biatomic active hydrogen (BAAH) and heterolytically splitting H2 to H+ relatively free from Ni/Z5A and H− adsorbed on Ni/Z5A. Over Ni/Z5A, the CHCs of naphth-1-ol and OBMDB proceeded via BAAH and H+ transfer to mainly produce tetralin and decalin from naphth-1-ol and methylcyclohexane and toluene from OBMDB.