A highly active difunctional Ni-Mg 2 Si/γ-Al 2 O 3 was prepared by thermally decomposing nickel tetracarbonyl onto γ-Al 2 O 3 impregnated with Mg 2 Si. The non-catalytic hydroconversion (NCHC) and catalytic hydroconversion (CHC) of the extract ( E ) and extraction residue (ER) from Yinggemajianfeng lignite were investigated over Ni-Mg 2 Si/γ-Al 2 O 3 at 240 °C in n -hexane. Benzyloxybenzene and oxybis(methylene)dibenzene were used as lignite-related model compounds to speculate the possible mechanisms for the catalytic hydrocracking and hydrogenation over Ni-Mg 2 Si/γ-Al 2 O 3 . As a result, more organic matter in ER was converted to soluble portion (SP) by the CHC than by the NCHC. The main SP from the CHC are chain alkanes and cyclanes, while that from the NCHC is rich in arenes and oxygen-containing organic compounds. The results indicate that Ni-Mg 2 Si/γ-Al 2 O 3 effectively catalyze the hydrocracking of >C alk –O– linkages and the hydrogenation of aromatic rings in E and ER.
Catalysts Ni/γ-Al 2 O 3 , Mg 2 Si/γ-Al 2 O 3 , and Ni-Mg 2 Si/γ-Al 2 O 3 were prepared. Their activities for catalytic hydroconversions (CHCs) of some lignite-related model compounds were examined. For the CHCs of oxydibenzene (ODB), benzyloxybenzene, and oxybis(methylene)dibenzene, the suitable loadings of Ni and Mg 2 Si are 33 and 20% in Ni-Mg 2 Si/γ-Al 2 O 3 , respectively, and the optimal reaction conditions are 4 MPa of initial hydrogen pressure, 240 °C, and 2 h, under which ODB was almost completely converted to cyclohexane. The formation of possible intermediates during the CHC of ODB was discussed. Ni-Mg 2 Si/γ-Al 2 O 3 was proposed to have 3 functions, i.e., activating H 2 to biatomic active hydrogen (H⋯H), releasing H − , and heterolytically splitting H⋯H to release H − as well, resulting in the hydrogenation of aromatic rings and the hydrocracking of C O bonds, respectively.
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