MOFs-derived N-doped carbon matrix superacid-catalyzed hydrocracking of a residue from thermal dissolution of Hefeng subbituminous coal

Abstract An active, low-cost, and recyclable catalyst was prepared by impregnating trifluoromethanesulfonic acid (TFMSA) onto metal-organic frameworks (MOFs)-derived N-doped carbon matrix nanoparticles. The residue (R TD ) from thermal dissolution (TD) of Hefeng subbituminous coal in methanol was subjected to further TD and catalytic hydrocracking (CHC) over the catalyst, i.e. , TFMSA/MOFs at 300 °C in cyclohexane. Detailed molecular compositions of the soluble portions from TD (SP TD ) and CHC (SP CHC ) were characterized with a Fourier transform infrared spectrometer, gas chromatograph/mass spectrometer (GC/MS), and positive-ion atmospheric pressure chemical ionization orbitrap mass spectrometer (PIAPCIORMS). The results show that 15.60% of organic matter in R TD was converted to a soluble portion by the CHC, whereas the yield of SP TD is only 1.04%. According to the analysis with GC/MS, SP CHC is rich in alkyl-substituted benzenes, while most of the GC/MS-detectable compounds in SP TD are alkyl-substituted arenols, alkyl-substituted cyclenones, and phenylalkanones in addition to alkyl-substituted benzenes. The analysis with PIAPCIORMS shows that both the number and yields of basic nitrogen-containing species were dramatically reduced after the CHC. These facts indicate that TFMSA/MOFs effectively catalyzed the cleavage of C ar –C alk bridged bonds connecting some aromatic rings (ARs) and side chains on some ARs in R TD to obtain soluble compounds. Di(1-naphthyl)methane and 2-(benzyloxy)naphthalene were used as coal-related model compounds (CRMCs) and their CHCs were investigated to further explore the catalysis of TFMSA/MOFs in the CHC of R TD . As a result, TFMSA/MOFs effectively catalyzed the cleavage of C ar -C alk and C-O bonds in the CRMCs under moderate conditions. TFMSA/MOFs can be easily separated by using an external magnetic field and the recovered TFMSA/MOFs is still highly active for the CHC of DNM.