Preparation Of Magnetic Supported Superacid Catalyst And Application For Hydroconversion Of Hefeng Subbituminous Coal

Xinjiang region is rich in subbituminous coals.Understanding the characteristics of organic molecular compositions and structures of subbituminous coals and their directional conversion mechanisms are of great importance for realizing value-added utilization of the coals.With this in mind,developing highly active and easily separated catalysts under mild conditions is highly desirable for achieving coals directional conversion.In this thesis,coal-related model compounds were used as probe molecules to evaluate the catalytic performance of catalysts,i.e.,MSSA,TFMSA/MOFs,and Ni_13%-TFMSA/TZ5A,and to explore the formation and transfer mechanisms of active hydrogen species in their catalytic hydroconversions?CHCs?.In addition,residues from extraction(HSBC_ER)and thermal dissolution(HSBC_TDR)of Hefeng subbituminous coal?HSBC?and the resulting methanol-soluble portions(HSBC_MSP)were subjected to CHCs,reapectively.Then the characteristics of molecular compositions and structures of organic macromolecules in the residues and their directional conversion mechanisms were inverted by analyzing soluble species resulting from the CHCs,which provides the key information for the subsequent hydroconversion of coal derivatives and finally realizes the comprehensive utilization of subbituminous coals.In this paper,three magnetic supported superacid catalysts were facilely prepared by impregnation without solvent at room-temperature and impregnation/in-situ decompostion method,repectively.Specifically:?1?A novel and highly active magnetic solid superacid?MSSA?with extraordinary separable and recyclable properties was facilely developed by impregnating trifluoromethanesulfonic acid?TFMSA?onto mesoporous zirconia coated ferroferric oxide nanoparticles?MPMC?;?2?An active,low-cost,and recyclable catalyst?TFMSA/MOFs?was prepared by impregnating TFMSA onto ZIF-67 metal-organic frameworks?MOFs?-derived N-doped carbon matrix nanoparticles?Co/NC?;?3?An active and recyclable supported Ni catalyst(Ni_13%-TFMSA/TZ5A)was developed by thermally decomposing nickel tetracarbonyl?NTC?to highly dispersive nickel nanoparticles onto treated zeolite 5A?TZ5A?impregnated with TFMSA.A series of advanced and modern technologies,including Transmission electron microscopy,Energy dispersive spectroscopy,Pyridine in situ infrared spectroscopy,Fourier transform infrared spectroscopy,H₂ temperature programmed reduction,X-ray photoelectron spectroscopy,X–ray diffraction,NH₃ temperature programmed desorption,N₂adsorption/desorption,superconducting quantum interference device magnetometer,and etc.,were used for the characterizations of catalysts,and then probe the relationships between the structures and surface properties with the catalytic properties.TFMSA was successfully loaded on the surface and pores of the supports,and strong interactions existed between the active components and supports both in MSSA and TFMSA/MOFs.In addition,the solid superacid catalysts possessed strong acidity.Both nickel particles and TFMSA were successfully loaded on TZ5A and the TFMSA loading was relatively higher in Ni_13%-TFMSA/TZ5A.Furthermore,strong interactions existed between the active components and support in Ni_13%-TFMSA/TZ5A.Furthermore,the catalyst Ni_13%-TFMSA/TZ5A possessed acid properties and lower nickel loading.The coal-related model compounds?CRMCs?,such as di?1-naphthyl?methane,9-benzylphenanthrene,1-methylnaphthalene,toluene,benzyloxybenzene,bibenzyl,dibenzyl ether,and 2-?benzyloxy?naphthalene,were used as probe molecules to investigate the catalytic performances of catalysts and the formation and transfer mechanisms of active hydrogen species in CHCs.MSSA effectively catalyzed the cleavage of C_ar–C_alk bridged bonds in CRMCs,which was attributed to the carbon atom in the iso-posotion of naphthalene tends to be attacked by the mobile H⁺transferred from cyclohexane.TFMSA/MOFs effectively catalyzed the cleavage of C_ar–C_alk and C–O bridged bonds.H⁺released from TFMSA in TFMSA/MOFs not only tends to attack the iso-posotion of aromatic rings but also transfer to the oxygen atom with more negatively charged to cleave the strong C–O bridged bonds.Ni_13%-TFMSA/TZ5A effectively catalyzed the cleavage of C–O bridged bonds in CRMCs,and then catalytic hydrogenation of the resulting products to afford cyclanes,which was ascribed to its functions of releasing the mobile H⁺,activating H₂ to H?H,and heterolytical splitting of H?H to a mobile H⁺and an immobile H^–adhered the catalyst surface.For the above CRMCs hydroconversion reactions:?1?HSBC_ER and HSBC_TDR were selected as coal samples in CHCs over TFMSA/MOFs and their non-catalytic hydroconversions?NCHCs?were used as contrast experiments.The soluble portions?SPs?from CHCs and NCHCs,respectively,were analyzed with a GC/MS qualitatively and quantitatively to investigate the catalysis of TFMSA/MOFs on CHCs of coal samples.As a result,the yields of the SPs from HSBC_ER-CHC and HSBC_TDR-CHC over TFMSA/MOFs were obviously higher than those of their NCHCs,and the yields of the SPs from both HSBC_ER-NCHC and HSBC_ER-CHC were higher than those of the HSBC_TDR-NCHCDR-NCHC and HSBC_TDR-CHC,indicating that TFMSA/MOFs showed outstanding activity in CHC of ER than TDR.In addition,thermal dissolution of HSBC in methanol could separate more organic small molecule compounds than those from the extraction with acetone/CS₂.The resulting arenes and arenols yields of the SPs from both HSBC_ER-CHC and HSBC_TDR-CHCDR-CHC are prominently higher than those of the their NCHCs.The SPs from both HSBC_ER-CHC and HSBC_TDR-CHC are rich in alkyl-substituted benzenes and phenols,and the relative content of arenes are predominant.These facts indicate that TFMSA/MOFs effectively catalyzed the cleavage of C_ar–C_alk and C–O bridged bonds connecting some aromatic rings?CARs?and side chains on some ARs in coals to obtain soluble compounds,i.e.,arenes and arenols;?2?HSBC_MSP was used to CHC over Ni_13%-TFMSA/TZ5A.The GC/MS result showed that HSBC_MSP contains a large number of alkanes,arenes,and oxygen-containing compounds,while most of the GC/MS-detectable compounds in HSBC_CHMSP are alkanes and arenes,and only small number of arenes and oxygen-containing compounds.The results indicate that Ni_13%-TFMSA/TZ5A efficiently catalyzed the hydrogenation of ARs and removal of heteroatoms,which prodives a protocol for achieving the conversion of coal derivatives to clean liquid fuel oil.The above investigations will be good not only for understanding the characteristics of organic molecular compositions and structures of coals,but also for providing the coals directional conversion under mild conditions.The present work might open a new avenue for acquiring the value-added chemicals and liquid fuel.