Catalytic hydroconversion of Yiwu lignite over solid superacid and solid superbase

Abstract

Trifluoromethanesulfonic acid supported on attapulgite powder (TFMSA/AP) and Mg2Si/γ-Al2O3 were facilely prepared by impregnating TFMSA onto AP and Mg2Si onto γ-Al2O3. The extraction residue from Yiwu lignite (YLER) was subjected to non-catalytic hydroconversion (NCHC) and catalytic hydroconversion (CHC) over TFMSA/AP and Mg2Si/γ-Al2O3, respectively. Detailed molecular compositions of the soluble portions from the NCHC (SPNCHC) and CHC over TFMSA/AP (SPCHC-A) and Mg2Si/γ-Al2O3 (SPCHC-B) were characterized with a gas chromatograph/mass spectrometer. As a result, the yields of SPCHC-A and SPCHC-B are 19.6% and 17.5%, respectively, which are much higher than that of SPNCHC (1.04%), suggesting that both TFMSA/AP and Mg2Si/γ-Al2O3 show excellent activity for the CHC of YLER. Arenes and arenols are predominant in SPCHC-A and SPCHC-B, respectively, while large amounts of alkanoates were detected in SPNCHC. The results indicate that TFMSA/AP effectively catalyzes the cleavage of Car–Calk and Calk–O bridged bonds (BBs) in YLER, while Mg2Si/γ-Al2O3 significantly promotes the cleavage of C–O BBs in YLER. Di(1-naphthyl)methane, 1-methylnaphthalene, oxydibenzene, and benzyloxybenzene were used as coal-related model compounds (CRMCs) for the CHC to further explore the catalysis of TFMSA/AP and Mg2Si/γ-Al2O3. The results show that TFMSA/AP not only releases mobile H+ but also heterolytically splits H2 to form an immobile H− and a mobile H+, leading to the cleavage of Calk–Car and Calk–O BBs in the CRMCs. In contrast, Mg2Si/γ-Al2O3 facilitates heterolytically splitting H2 to an immobile H+ and a mobile H−, resulting in the cleavage of C–O BBs in the CRMCs.