Fine Separation Of Zaozhuang High Temperature Coal Tar And Molecular Simulation

High temperature coal tar（HTCT）is a by-product of coal pyrolysis with extremely complex chemical composition.In addition,due to the"three highs"problem of traditional HTCT processing technology,HTCT has been labeled as"contaminated"and has increased the difficulty of its refined utilization.However,the condensed arenes,nitrogen-,oxygen-,and sulfur-containing aromatic compounds enriching in HTCT are one of the irreplaceable sources of numerous value-added chemicals,such as naphthalene,phenol and quinoline.In this paper,conventional volatile organic solvents and eco-friendly deep eutectic solvents（DESs）are combined with kilogram-level HTCT high-efficiency separation experimental plant,modified high-pressure preparative chromatograph（MHPPC）plant and flash preparative chromatograph（FPC）plant to achieve the refined,efficient and clean HTCT in-depth processing technology.The kilogram-level HTCT high-efficiency separation plant is designed,processed and operated according to the requirements of experimental and technological parameters.The plant mainly includes extraction separation,solvent distillation,crystallization/column chromatography,solvent circulation,cooling,exhaust gas treatment and power control unit.It has the advantages of large processing capacity,good extraction effect,simple process,strong controllability,mild operating conditions,high safety factor,low energy consumption and environmental friendliness.According to the results of small-scale experiments,HTCT was extracted with petrolumn ether（PE）:HTCT=4:1 to obtain light portions（LP）and analyzed by gas chromatograph/mass spectrometer（GC/MS）,which further elucidated that the extraction by the kilogram-level HTCT high-efficiency separation plant can effectively remove the heavy components（e.g.colloids and asphaltenes）in HTCT.The yield of LP is 32.6 wt%,and the relative content of condensed arenes decreased slightly from 90.3%to 86.6%,while the relative content of nitrogen-containing aromatics（NCAs）remained unchanged.Therefore,LP,which removes the heavy components of macromolecules such as colloids and asphaltenes,can be used as the raw material for the continuous separation and purification of various fractions,especially in the preparation column chromatography process,in order to obtain a series of value-added aromatic compounds.The separation of LP by multi-stage column chromatography plants shows that the self-MHPPC uses silica gel as a stationary phase to enrich condensed arenes into EP₁-EP₅ according to molecular weight（or number of aromatic rings）and enrich heteroatom-containing aromatics into EP₆-EP₉.The FPC further separates the enriched EP_n,and obtains phenanthrene（94.5%）,fluoranthene（86.5%）,pyrene（76.6%）,benzo[k]fluoranthene（94.4%）,benzo[a]pyrene（96.3%）and other condensed arenes with relative content exceeding 75%.However,limited by the ability of silica gel to selectively adsorb/desorb the homologues/isomers of heteroatom-containing aromatics,it can not to obtain heteroatom-containing aromatics with a relative content surpassing 75%.Crystalline white naphthalene（99.9%）was obtained from EP₁ by recrystallization process.LP was separated and purified by DES extraction and FPC stepwise gradient elution.The fractions were characterized and analyzed by GC/MS,fourier transform infrared（FTIR）and nuclear magnetic resonance（NMR）.The experiments and molecular dynamics simulations verify that the noncovalent bond interaction between DES₄（equimolar mixed choline chloride/malonic acid was denoted as DES₄）and NCAs is stronger than that of condensed arenes.Under the optimal conditions of 35 ^oC and a mass ratio of DES₄/LP of 1:2,NCAs can be separated from LP.The yield is 35.3%and the selectivity to basic NCAs is 90.9%.In addition,DES₄ can be recycled 3 times and its extraction capacity slightly decreases.FPC equipped with silica gel as the stationary phase and different solvents as the mobile phase performs gradient elution of EP₂ enriched by DES₄ exteaction,and further obtains quinoline（90.4%）,carbazole（93.3%）and benzo[h]quinoline（92.0%）.Molecular dynamics simulations demonstrate that the noncovalent bond interaction types between condensed arenes and PE,ethyl acetate or methanol are similar,but the solvation free energy（SFE）calculated by Gaussian illustrates that PE with low cost and low polarity has suitable solubility for condensed arenes.However,due to the-C=O of ethyl acetate,the solubility of condensed aromatics in ethyl acetate is the best.Compared with condensed arenes,due to the presence of heteroatoms（N,O and S）,heteroatom-containing aromatics and solvent molecules（PE,ethyl acetate,methanol and their mixed solvents）have the binding sites with strong attraction.This can produce a strong noncovalent bond interaction at the binding site,especially the noncovalent bond interaction of phenol-type oxygen-containing and carbazole-type NCAs is stronger than that of pyridine-type NCAs.SFE also displays that 70%ethyl acetate/30%methanol and 100%methanol have the best solubility for nitrogen-containing and oxygen-containing aromatic compounds,respectively.Equimolar mixed choline chloride/malonic acid as a DES₄,that is a uniform and flowing transparent liquid and is dominated by the electrostatic interaction of anions and cations,has a strong noncovalent bond interaction between malonic acid molecule and Cl^-by noncovalent interaction energy and radial distribution function analysis,which greatly reduces the respective melting points.Furthermore,the noncovalent bond interaction type between equimolar mixed choline chloride/malonic acid and NCAs was analyzed by reduced density gradient function,which describes that equimolar mixed choline chloride/malonic acid and the nitrogen atom of NCAs can generate the binding site,such as hydrogen bond,X-H··πbond and van der Waals interaction,which promotes the selective extraction of NCAcs from HTCT,especially basic NCAs.In addition,thermal fluctuation index analysis also proved that the noncovalent bond interaction between DES₄ and aromatic compounds is stable near room temperature.There are 45 figures,16 tables and 104 references in this thesis.