Catalytic Hydroconversion Of Two Xinjiang Middle-and Low-Rank Coals And Coal-Related Model Compounds

Xinjiang region is rich in middle-and low-rank coals.Understanding the characteristics of molecular compositions and structures of Xinjiang middle-and low-rank coals and their directional conversion mechanisms are of great importance for realizing value-added utilization of the coals and thereby converting the coal resource predomination to strong economic benefits.In this thesis,coal-related model compounds were used as probe molecules to evaluate the catalytic performance of catalysts,i.e.,TFMSA/MFA,Ni/MFA,and Ni/MFA@AIL,and to explore the formation and transfer mechanisms of active hydrogen species in their catalytic hydroconversions?CHCs?.In addition,extraction residues from Yiwuxian lignite(YL_ER)and Hefeng subbituminous coal(HSBC_ER)were subject to CHCs,reapectively,and 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 above CHCs.In this paper,three types of supported catalysts were facilely prepared by room-temperature impregnation method,in-situ decompostion method,and impregnation/in-situ decompostion method,repectively.The novel solid superacid catalyst TFMSA/MFA was prepared by impregnating trifluoromethanesulfonic acid?TFMSA?into microfiber attapulgite?MFA?at room temperature.The supported nickel-based catalyst Ni/MFA was facilely and effectively prepared by in-situ decomposing nickel tetracarbonyl?NTC?onto MFA at relative low temperature.The nickel-acid bifunctional catalyst Ni/MFA@AIL was facilely and effectively prepared by impregnating 1-sulfobutyl-3-methylimidazolium trifluoromethanesulfonate?AIL?into MFA,and then by in-situ decomposing NTC onto MFA@AIL.A series of advanced and modern technologies,including Transmission electron microscopy,Energy dispersive spectroscopy,H₂ temperature programmed reduction,X-ray diffraction,X-ray photoelectron spectroscopy,NH₃ temperature programmed desorption,Fourier transform infrared spectroscopy,N₂ adsorption/desorption,thermogravimetric analysis,and etc.,were used for the characterizations of catalysts,and the catalytic performances were associated with the relationship between catalyst structures and surface properties.TFMSA was successfully supported on the surface and pores of MFA,and strong interactions existed between the active components and support in TFMSA/MFA.In addition,the solid superacid catalyst possessed strong acidity.Nickel particles were uniformly distributed on the surface of MFA and strongly interacted with support in Ni/MFA.Both nickel particles and AIL were successfully loaded on MFA and their loadings were relatively low in Ni/MFA@AIL.Furthermore,strong interactions existed between the active components and support in Ni/MFA@AIL.The coal-related model compounds,such as di?1-naphthyl?methane,1-methylnaphthalene,oxydibenzene,benzyloxybenzene,2-ehoxynaphthalene,anthracene,diphenylmethane,bibenzyl,1,3-diphenylpropane,and dibenzyl ether,were used as probe molecules to investigate the catalytic performances of catalysts and the formation and transfer mechanisms of active hydrogen species in CHCs.TFMSA/MFA effectively catalyzed the cleavage of C_ar–C_alk and C_alk–O bridged bonds ranther than C_ar–O bridged bond in coal-related model compounds,which were attributed to its dual functions of releasing the mobile H⁺,and heterolytical splitting of H₂ to a mobile H⁺and an immobile H^–adhered the catalyst surface.Anthracene could be completely converted to perhydroanthracenes at 175°C and selectively converted to9,10-dihydroanthracene at 300°C by catalytic hydrogenation over Ni/MFA.The high activity of Ni/MFA for anthracene hydrogenation to perhydroanthracenes at lower temperatures was ascribed to its function of activating H₂ to H?H.At high temperatures,the resulting H?H tends to be thermally and homolytically split to H·.Quantum chemical calculations based on density functional theory further confirmed the temperature-controlled hydrogenation of anthracene over Ni/MFA.Ni/MFA@AIL effectively catalyzed the cleavage of C_ar–C_alk and C_alk–O bridged bonds in coal-related model compounds,and then catalytic hydrogenation of the resulting products to afford cyclanes,which was attributed 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.YL_ER and HSBC_ER were selected as coal samples in CHCs over Ni/MFA@AIL and their non-catalytic hydroconversions?NCHCs?were used as contrast experiments.The soluble portions from CHCs and NCHCs,respectively,were analyzed with a GC/MS qualitatively and quantitatively to investigate the catalysis of Ni/MFA@AIL on CHCs of coal samples.The yields of the soluble portions from CHCs of YL_ER and HSBC_ER over Ni/MFA@AIL were obviously higher than that of those from their NCHCs,indicating that Ni/MFA@AIL show excellent activity in above CHCs.The soluble portions from CHCs and NCHCs of YL_ER and HSBC_ER mainly consist of aliphatic hydrocarbons,alkenes,cyclanes,arenes,arenols,alcohols,esters,ethers,ketones,and other compounds.The realative contents of cyclanes in SPs from CHCs of YL_ER and HSBC_ER were higher than those from their NCHCs,however most of alkenes,arenes,parenols,alcohols,ethers,and ketones in soluble portions from CHCs were lower than those from NCHCs.The results suggest that Ni/MFA@AIL efficiently catalyzed the cleavage of C-C and C-O bridged bonds in YL_ER and HSBC_ER,and subsequently catalyzed hydrogenation and dehydroxylation.The above investigations will be good not only for understanding the characteristics of molecular compositions and structures of Xinjiang middle-and low-rank coals,but also for providing important scientific basis so as to establish an industrial chain of value-added utilization of middle-and low-rank coals in Xinjiang region.