Efficient Separation And Gentle Catalytic Hydrogenation Conversion Of Medium And Low Temperature Coal Tar In Northern Shaanxi

Medium and low temperature coal tar（MLTCT）is a highly aromatic hydrocarbon rich in various components,such as polycyclic aromatic hydrocarbons,alkanes and phenols.Among them,phenols and alkanes account for up to 30%and 20%of MLTCT.phenols and alkanes are widely used in fine and energy chemical industry,so efficient separation of coarse powder and alkanes is an important way for the high-value utilization of MLTCT.Based on this,this paper uses the method of two-solvent extraction to separate MLTCs to obtain petroleum ether extraction fraction(EP_PE),methanol extraction part（EP_M）and carbon disulfide extraction fraction(EP_CDS),and then realizes the high-value fine utilization of MLTCT by developing highly active catalysts,and selects a series of model compounds as probe molecules,and systematically investigates the hydrogenation isomerization,hydroconversion performance and reaction mechanism of highly active catalysts（Pd/Yβ,Ni/YBCZ）.The catalytic hydroconversion ability of EP_CDS under the action of Ni/YBCZ was further investigated,and the comparative analysis of organic components provided a high-value utilization pathway for EP_CDS in MLTGT.The details are as follows:（1）According to the component characteristics of MLTGT,the extraction solvent with large difference in boiling point and polarity was selected under ultrasonic radiation conditions to treat MLTCT,and the total yield of EP_PE was 54.7%,the total yield of EP_M was 25.2%,and the total yield of EP_CDS was 20.1%.GC/MS analysis of the corresponding organic components showed that the EP_PE component was composed of paraffins（49.0%）,aromatics（39.0%）and a small amount of heteroatoms;EP_M is composed of oxygenates（71.4%）,aromatics（26.7%）and a few heteroatoms;The main components of EP_CDS are aromatics and heteroatom compounds,and the content is up to 96.7%.（2）Based on rich chain alkane property of EP_PE components,the efficient isomerization of chain alkane was realized by preparing a multi-stage porous zeolite-supported palladium catalyst（Pd/Yβ）with high silicon shell,and its performance was evaluated.The catalyst has a stable skeleton structure,high specific surface area,good porosity and uniform distribution of approachable acidic sites,and the conversion rate of n-heptane（n-C₇）is as high as 86.1%at 280 ^oC and 1MPa hydrogen pressure,and the selectivity of isoalkanes（i-C₇）is 86.7%in the hydrogenation isomerization reaction of n-heptane（n-C₇）.（3）EP_CDS is rich in aromatic hydrocarbons and heteroatomic compounds,and in this study,bifunctional catalyst Ni_10%/YBCZ was prepared by preparing Y/beta composite zeolite（YBCZ）,loaded with Ni nanoparticles（loading 10%）,and reacted at 160 ^oC and 5MPa hydrogen pressure for 18 h,chain alkanes（CA,4.0%）,oxygenated organic compounds（OCOC,56.0%）,aromatics（arenes,35.3%）in the EP_CDS component,Nitrogenous organic compounds（NCOCs,3.3%）and sulfur-containing organic compounds（SCOCs,1.4%）were all converted to chain alkanes（CAs,9.0%）,cycloalkanes（70.8%）and hydroarenes（20.2%）.Oxydibenzene rich in>Car-O bridge bonds were used as modeled compounds to study the reaction mechanism of aromatic ring hydrogenation saturation and efficient removal of heteroatoms in the catalytic hydrogenation conversion of aromatic hydrocarbons and heteroatoms,which provided a theoretical basis for the efficient utilization of heavy aromatic hydrocarbons containing heteroatoms.