Composition Analyses And Catalytic Hydroconversion Of Organic Matters In Ekuang Subbituminous Coal

Xinjiang region is rich in coal resources.Understanding the compositions and structure characteristics of organic macromolecules in Xinjiang coals and their directional conversion mechanisms is of great importance for realizing the value-added utilization of the coals.The development of catalysts with high activity and stability is the core issue for achieving the high value-added utilization of coals.In this thesis,Ekuang subbituminous coal(ESBC)was studied to understand the molecular structure of organic matter in the coal by using a variety of direct characterizations.Using coal-related model compounds(CRMCs)as probe molecules,the catalytic hydroconversion(CHC)performance of Ni₂P and Ni Co P and the formation and transfer mechanisms of active hydrogen species in the CHC process were systematically investigated.Moreover,the ESBC was subjected to CHC to afford soluble portions,which were analyzed to deduce the structure characteristics of the organic macromolecule skeleton in ESBC and CHC mechanisms,providing the theoretical support for the efficient and comprehensive utilization of coals in Xinjiang.Scanning electron microscope(SEM),solid-state ¹³C nuclear magnetic resonance,X-ray photoelectron spectrometer(XRPES),thermogravimetric analyzer(TGA),Fourier transform infrared spectrometer and Curie point pyrolysis-gas chromatography/mass spectrometer(CPP-GC/MS)were used to directly characterize the ESBC.The results show that aliphatic and aromatic carbon atoms are dominated in ESBC accounting for 44.5%and 52.5%,respectively.Aromatic carbon atoms mainly exist in non-substituted aromatic clusters and aromatic clusters with side chains containing oxygen-containing groups or alkyl substituents.Each aromatic cluster contains 2 rings on average with 3-4 substituent groups on each ring and each substituent group contains 1-2 methylene structures.-OH group is the mainly existing form of the oxygen element on the surface of ESBC,and a small amount of nitrogen and sulfur elements exist in the form of pyrrole nitrogen and sulfate,respectively.The total weight loss of ESBC is 35%,and the breaking of most covalent bonds such as C_alk-C,C_alk-H,C_alk-O,and C_ar-N occurs between 400-500 ^oC.10 volatile components were detected from ESBC with CPP-GC/MS at 3 different pyrolysis temparetures,including n-alkanes,branched alkanes,n-alk-1-enes,other alkenes,arenes,indanes,indenes,phenols,furans,and other oxygen-containing species,in which the relative content of n-alkanes,branched alkanes,arenes,and phenols are the most abundant.The n-alkanes and n-alk-1-enes with C₉–C₂₈ were detected as the straight-chain form in pairs.Phenolic compounds released from the breaking of C–O bridged bonds in aryl ethers are dominated by alkylphenols.All the non-supported and supported metal phosphate catalysts were prepared by hypophosphate pyrolysis and tested to select Ni₂P and Ni Co P catalysts with the best activities,which were characterized by SEM-EDS,Transmission electron microscopy,X-ray diffraction,XRPES,H₂ temperature programmed reduction and TGA.The results showed that the particles of Ni₂P and Ni Co P catalysts were nanoscale spherical particles with the particle size between30-70 nm.The 2 catalysts have no reducibility in H₂ blow 350 ^oC and great thermostability in N₂.According to the exploration of the catalytic reaction conditions and the catalytic product distribution of the 2 CRMCs,i.e.,(benzyloxy)benzene(BOB)and(oxybis(methylene))dibenzene(OBMDB),the Ni₂P catalyst has good catalytic activity and product selectivity for BOB and OBMDB.A higher temperature and pressure and a longer reaction time is conductive to the aromatic ring hydrogenation and dehydroxyl reaction.The Ni Co P catalyst can efficiently catalytically hydrocrack the C–O bridged bonds in BOB and OBMDB at low temperatures,and the products selectivity is well without aromatic ring hydrogenation.According to the noble metal-like properties of metal phosphates and the distribution of catalytic products,the Ni₂P and Ni Co P catalysts can activate H₂ to generate H·,which·attacks the carbon atom connected with oxygen atom to induce subsequent radical reactions,affording CHC products.Ni₂P and Ni Co P were selected as catalysts to perform CHC of ESBC,and their non-catalytic hydroconversions(NCHCs)were conducted as contrast experiments.The soluble portions(SPs)from CHCs and NCHCs were analyzed with a GC/MS and quadrupole exactive orbitrap mass spectrometer(QEOTMS)to investigate the catalysis of the 2 catalysts on CHCs of coal samples.The yields of SPs obtained by CHC on the 2 catalysts were higher than that of NCHC,indicating that both catalysts have good CHC effect on ESBC.The yields of arenes,hydroarenes,and phenolic compounds in SP₂ obtained by CHC reaction over Ni₂P catalyst were all higher than those in SP₁ obtained by NCHC reaction,indicating that Ni₂P can effectively promote the breaking of C–O bridged bonds in ESBC and partial hydrogenation of aromatic rings.The aromatic compounds in SP₁ and SP₂ are dominated by hydrocarbon(HC),N_xO_y,and O₁–O₃ class species,in which nitrogen atoms mainly exist in the form of pyridines,amino groups,and amides,while oxygen atoms exist in the form of hydroxyl groups,ether bonds,carbonyl groups,carboxyl groups,and furan rings.The yields of arenes and phenolic compounds in SP₄ obtained by CHC reaction over Ni Co P catalyst were higher than those in SP₃ obtained by NCHC reaction,and the aromatic compounds in SP₃ and SP₄ are dominated by HC,N₂O_y,and O₁ class species.QEOTMS analysis indicated that CHC of ESBC over both catalysts could obtain aromatic compounds with larger molecular weight,more heteroatoms,and higher condensation degree.Meanwhile,both catalysts have certain performance of hydrogenation to remove heteroatoms.This thesis contains 75 Figures,44 Tables,and 223 References.