Hydroconversion Of East Mongolia Lignite Catalyzed By Supported Solid Superacid

Hydrocracking is one of the most important reactions for direct coal liquefaction. The preparation of catalysts with high activity is the key technology in coal liquefaction. In this study, a supported solid acid catalysts(TFMSA/AP) was prepared by impregnating trifluoromethanesulfonic acid(TFMSA) into purified attapulgite powder(AP). A variety of means to characterize and analyse the above catalyst, i.e., Fourier transform infrared spectroscopy(FTIR), Scanning electron microscopy with Energy dispersive X–ray spectroscopy(SEM-EDS), X–ray photoelectron spectroscopy(XPS), X–ray diffraction(XRD), Brunauer-Emmett-Teller method(BET) and NH3 temperature programmed desorption(NH3-TPD). The characterization results showed that TFMSA was effectively loaded on the surface and pore of AP, and there exists interaction between the carrier and the active component. TFMSA/AP has superacidity and the total number of acid sites is 1.02 mmol/g. Hydrocracking of di(1-naphthyl)methane(DNM) and benzyloxybenzene(BOB) were used as probe reactions to investigate the activities of the catalyst and optimize their reaction conditions. The results showed that TFMSA/AP was high active for hydrocracking of DNM and BOB, the conversions of them are 87% and 98%, respectively.The extraction and thermol dissolution residues(MLER, MLTDR) of East Mongolia Lignite(ML) were selected as the coal samples in the catalytic hydrocracking(CHC) over TFMSA/AP. The non-catalytic hydrocracking(NCHC) were used as contrast experiments. The soluble portions(SPs) from CHC and NCHC were analyzed with a gas chromatograph/mass spectrometer(GC/MS) qualitatively and quantitatively to investigate the catalysis of TFMSA/AP on the hydrocracking of coal residue. The yields of products from CHC were significant higher than that from NCHC, and the yields of arenes, phenols, sulfur-containing organic compounds(SCOCs) and nitrogen-cintaining organic compounds(NCOCs) of SPs from CHC were also significant higher than that from NCHC, suggesting that TFMSA/AP can highly promote the arenes and phenols to release and N and S elements to remove from coal residues. The content of phenols is the highest among the SPs from CHC of MLER and MLTDR, and the homologs of phenol accounted for the largest proportion in phenols, the content of arenes takes second place, and the homologs of benzene accounted for the largest proportion in arenes.While the content of esters is the highest among the SPs from NCHC of MLER and MLTDR, and the homologs of ethyl esters accounted for the largest proportion in esters.Alkyl aromatics containing Car–Calk bond and alkly aryl ethers containing C–O bond were selected as coal-related model compounds to investigate the CHC mechanism of TFMSA/AP. The results showed that the protons released from TFMSA/AP attack selectively on the ipso-position of aromatic ring or transfer to the oxygen atom of the ether bridge bond, leading to the cleavage of Car–Calk and C–O bond, which could be the crucial step for alkyl aromatic and alkly aryl ether hydrocracking, respectively. Based on the hydrocracking mechanism of the two kinds of model compounds containing Car–Calk and C–O bonds and the group distributions of SPs from CHC and NCHC of coal samples, the formation mechanisms of arenes and phenols from CHC were revealed.