Catalytic Hydrogenation Performance Of Co-Mo/?-Al₂O₃ And Application In Heteroatoms Removal For Dongming Lignite Upgrading

As a fossil fuel,coal has a large amount of reserve and a wide distribution.Lignite,a low rank coal,contains a large number of hetero atoms?O,N,S?in various forms,which reduce the utilization efficiency as a fuel.Therefore,the preparation of efficient and inexpensive catalysts is beneficial to the removal of heteroatoms in lignite,and understand the molecular composition and characteristics of lignite at the mean time.In this paper,a Co-Mo/?-Al₂O₃ bimetallic catalyst was prepared via an equal volume impregnation method.?NH₄?₆Mo₇O₂₄·4H₂O and Co?NO₃?₂·6H₂O were used as active components and commercial?-Al₂O₃ was used as a carrier.The catalyst was vulcanized before to use.The prepared catalyst was characterized by Brunner-Emmet-Teller?BET?,NH₃ temperature programmed desorption?NH₃-TPD?,scanning electron microscope?SEM?,field emission transmission electron microscopy-energy dispersive chromatography?TEM-EDS?,X-ray photoelectron spectroscopy?XPS?,and X-ray diffraction?XRD?.The results show that the active components,Co and Mo,are successfully supported on the carrier?-Al₂O₃ to obtain Co-Mo/?-Al₂O₃ bimetallic catalyst.Mo is the main active component and the valence state is Mo⁴⁺.Layered stacking crystal is the dominate structure in MoS₂ catalyst.Coal-related model compounds?CRMCs?,including oxybis?methylene?dibenzene?OBMDB?,furan?FR?,thiophene?TP?and quinoline?QL?,were used as the probe molecule to evaluate the catalytic performance of catalysts and study the catalytic hydroconversion pathway for each CRMCs.Meanwhile,the effects of reaction temperature,reaction time and initial hydrogen pressure on the conversion of each CRMCs were studied.Refer to optimum reaction conditions for each CRMCs were selected to study the catalytic hydrogenation conversion of souble organic matter in Dongming lignite?DL?.A thermal dissolution experiment was carried out at 300?with sopropanol?IPA?solvent to obtain soluble organic matter named DL_IPA.DL_IPA was subjected to catalytic hydrotreation conversion to obtain DLIPA260,DLIPA280,DLIPA300,DLIPA320 and DLIPA340under different conditions.DL_IPA and the catalytic products were analyzed by elemental analyzer,Fourier transform infrared spectroscopy?FT-IR?,gas chromatography/mass spectrometer?GC/MS?,and quadrupole Orbitrap mass spectrometer?Orbitrap MS?.Results of the ultimate analyses show that the content of O,N and S is decreased in DL_IPA after via the catalytic process.Results of the FT-IR results indicate that the catalyst can break the C-O bonds to produce more hydrocarbon compounds in the macromolecule.According to the GC/MS data,indicate that the relative content of alkane compounds for DL_IPA organic matter is increasesd significantly after via the catalytic process.At the same time,the relative contents of aromatics,phenols,esters,alcohols and other species?some oxygen-containing,sulfur-containing and nitrogenr-containing compounds,etc.?is decreased,while the relative contents of olefins and ketones first increased first and then decreased.Another,the relative contents of ethers and aldehydes is increased slightly.In addition,results of Oribtrap MS results suggest that the weighted average double bond equivalents?DBE?and carbon number?CN?values for DL_IPA decreases after catalytic hydrogenation under different conditions.Among them,the relative contents of O₂-O₆ group compounds for DL_IPA decreases after the catalytic hydrogenation under different conditions,while the relative content of O₁compounds increases.It may be the possible reason is that the new O₁ group compounds are generated from O₂-O₆ group compounds via partial deoxygenation.After the catalytic hydrogenation,compared with the relative content of the N₁-N₄ group compounds in DL_IPA,the relative contents of the N₁-N₄ group compounds is increased.At the same time,the relative content of the S group compounds in DL_IPA is 1.38%,while no S group compound is detected in the catalytic products.The above results indicate that the Co-Mo/?-Al₂O₃ bimetallic catalyst has obvious catalytic effects on catalytic deoxidation,catalytic desulfurization,catalytic denitrification and promotion of hydrogenation fracture of aromatics ring compounds.The paper has 36 figures,18 tables and 130 references.