Sequential Thermal Dissolution And Catalytic Hydroconversion Of Xingjiang Piliqing Subbituminous Coal Over Solid Superbase

Xinjiang region is rich in subbituminous coals.In spite of their large-scale exploitation and low transportation costs,subbituminous coals have not been used as widely as bituminous coals and anthracites owing to their high water and ash contents.Therefore,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 Xinjiang subbituminous coals.They are also rich in arenes and oxygen-containing bridged bonds,such as the>C-O-bridged bonds?COBBs?.Besides,sulfur-containing and oxygen-containing species exist in subbituminous coals.Therefore,cleavage of COBBs,hydrogenation of arenes,and removal of heteroatoms under mild conditions are crucial to efficient,clean,and value-added utilization for subbituminous coals.In this thesis,composition characterization of organic matters in subbituminous coal was performed using two methods for degradation,including sequential thermal dissolution?STD?and catalytic hydroconversion?CHC?,combined with various advanced analytical techniques.In addition,STD and CHC of extraction residue?ER?from PSBC were studied in order to obtain soluble portions?SPs?and examine STD and CHC effect on organic structures in PSBC.Meanwhile,the characteristics of molecular compositions and structures of organic macromolecules in PSBC and their directional conversion mechanisms were inverted at the molecular level for providing an important scientific basis and information support for the efficient utilization of subbituminous coals and obtaining high value-added chemicals from subbituminous coals in Xinjiang region.Proximate and ultimate analysis,scanning electron microscope,solid-state ¹³C nuclear magnetic resonance,X-ray photoelectron spectrometer?XRPES?,Fourier transform infrared?FTIR?spectrometer?FTIRS?and thermal gravimetric analyzer were used to directly characterize PSBC for obtaining comprehensive information on organic structures in PSBC,including micromorphology,carbon skeleton structures,element forms on the surface,functional groups,and covalent bond types in PSBC.ER was thermally dissolved sequentially in n-hexane,toluene,methanl,and ethanol to obtain soluble portions?SPs?1–4(SP_1-4)from the thermal dissolution?TD?with the total yield of 40.1%.According to the analysis with gas chromatograph/mass spectrometer?GC/MS?,SP_1-4 all contain abundant arenols,while arenes mainly exsist in SP_1-3,and the arenes contains 1-3 aromatic rings?ARs?.The main ethers in SP₃are methoxy substituted ethers,and esters are predominant in SP₄.Arenols could be generated from the breakage of>C-O-in PSBC during TD or ethanolysis.The esters could be ascribed to transesterification and the breakage of>C-O-bridged bonds during methanolysis and ethanolysis.These are the main reasons for the high yield of SP₃ and SP₄.In addition,according to the analysis with quadrupole exactive-orbitrap mass spectrometer,the main oxygen-containing organic compounds in SP₄ are ethyl benzoates,arenols,and alkoxy-containing compounds.The main nitrogen-containing organic compounds?NCOCs?in SP₄ are nitrogen-containing ethyl benzoates,quinoline arenols,alkoxyquinolines,and benzoylpyrazoles?or benzoylimidazoles?.Beside,sulfur-containing organic compounds?SCOCs?are main sulfoxides and thiophenes,providing important information on S and N forms occurring in subbituminous.Magnetic supported nickel supersbase Ni-Mg₂Si/attapulgite powder?AP?was prepared by thermally decomposing nickel tetracarbonyl onto the as-synthesized Mg₂Si/AP by impregnating Mg₂Si onto AP in CCl₄.A series of advanced and modern technologies,including N₂adsorption/desorption,transmission electron microscopy,energy dispersive spectroscopy,FTIRS,H₂ temperature programmed reduction,XRPES,X-ray diffraction,superconducting quantum interference device magnetometer,and etc.were used for the characterizations of Ni-Mg₂Si/AP.Ni and Mg₂Si are successfully loaded on the surface and pores of the support,and Ni-Mg₂Si/AP exhibits strong paramagnetismt.Besides,it possesses strong base properties.Its catalytic performance was evaluated by the catalytic hydroconversion?CHC?of?oxybis?methylene??dibenzene?OBMDB?and oxydibenzene?ODB?in n-hexane under different reaction conditions.Both OBMDB and ODB were completely converted at low temperature?150??.OBMDB was completely converted to methylcyclohexane by the CHC over Ni-Mg₂Si/AP under 3 MPa of initial hydrogen pressure?IHP?at 240 ? for 2 h.ODB was completely converted to cyclohexane by the CHC over Ni-Mg₂Si/AP under 3 MPa of IHP at 240 ? for 4 h.Therefore,Ni-Mg₂Si/AP is a highly active difunctional solid superbase.It could activate H₂ to biatomic active hydrogen?H…H?and H^-,resulting in the hydrogenation of ARs,the hydrocracking of>C-O-bridged bonds?COBBs?,and removal of–OH,respectively.The enthalpy change of reaction were calculated by density functional theory,it assists the mechanisms for directional CHC of OBMDB and ODB.Recycling experiments was used to evaluate the stability of Ni-Mg₂Si/AP under the same conditions.The Ni-Mg₂Si/AP after recycling 4 times possesses strong base properties.Additionally,the catalyst was also successfully applied in the CHC of extract soluble portion?ESP?and ER from PSBC in n-hexane.The group components and functional group of the SPs from CHC and non-CHC?NCHC?of ESP and ER(SP_E-NCHC-NCHC and SP_E-CHC,SP_ER-NCHC and SP_ER-CHC)were analyzed with a GC/MS and FTIRS,respectively.The relative content?RC?of non-substituted arenes?NSAs?is predominantly high in the SP_E-NCHC,which is 28.0%,followed by alkyl-substituted phenanthrenes,and considerable ethers and NCOCs.However,non-substituted cyclanes?NSCAs?are predominant in the SP_E-CHC,accounting for 66.8%of the total group components,and interestingly 65.3%of NSCAs is cyclohexane,followed by alkanes,and considerable alkyl-substituted cyclohexanes and tetralins exsit in SP_E-CHC.It is interesting that no benzofurans and NCOCs in SP _E-CHC and no NSCAs in the SP_E-NCHC have been detected.The yield?36.4%?of SP_ER-CHC is significantly higher than that?1.8%?of SP _ER-NCHC.The RC of arenols is predominantly high in SP_ER-NCHC,accounting for 45.5%,followed by arenes,while arenes is the highest in SP_ER-CHC,accounting for 68.2%,followed by alkanes.The arenes in SP_ER-CHC are main hydroarenes.Besides,SP_ER-CHC also contains considerable cyclanes and non-substituted arenes.However,anisoles,NCOCs,and SCOCs in SP_ER-NCHC are much more abundant than those in SP_ER-CHC.It is interesting that cyclanes and hydroarenes only exist in SP_ER-CHC,while anisoles,methoxy-substitued methylphenols,and SCOCs only appear in SP_ER-NCHC.These results indicate that Ni-Mg₂Si/AP is highly active for catalyzing the cleavage of COCBBs,the hydrogenation of ARs and the removal of O,N,and S heteroatoms in ER.Based on the above analysis,the possible parthways for the formation of some compounds producted by the CHC of ESP and ER are proposed,and the synergism of H^-and H…H transfer is also clarified on a molecular level.This thesis contains 73 Figures,54 Tables,and 198 references.