Structural Features And Pyrolytic Products Distribution Of Organic Matter From Coal Liquefaction Residue

The coal liquefaction residue(CLR)accounts for about 30 wt.% of the raw coal.The composition and structure are complex.CLR has the characteristics of high carbon,high sulfur and high ash.CLR is rich in high value-added polycyclic aromatic structures,which is difficult to achieve efficient use and severely restricts direct coal liquefaction.In order to explore the clean conversion and efficient utilization of coal liquefaction residue,it is of great significance to understand the composition and structure of organic matter in coal liquefaction residue.In this paper,the solvent extraction technology combined with Ultrasonic-Soxhlet Extraction was used to extract coal liquefaction residue with a mixture of methanol and toluene in equal volume,coal liquefaction residue extract(CLRE)was obtained..The chemical composition and structural characteristics of CLRE were studied by analyzing CLRE by Pyrolysis-gas chromatography mass spectrometer(Py-GC/MS)at different temperatures.The molecular in CLRE were studied by stepwise ruthenium ion catalytic oxidation(RICO)method,combined with gas chromatography mass spectrometry(GC/MS)and Fourier transform infrared spectroscopy(FTIR)analysis.The esterification products of organic phase were detected and analyzed by GC/MS on CLRE RICO step by step,and the organic composition and molecular structure information of CLRE were inferred by observing the composition structure of products.After methylation of the oxidation products obtained by RICO,the acids and compounds corresponding to the GC/MS detectable components can be divided into five categories: including alkanes acid compounds(AAs),benzene acid compounds(BCAs),other acid compounds,ester compounds and other compounds.Other compounds mainly include long-chain alkanes,aromatic hydrocarbons,alkenes / alkynes,acid anhydrides,amides,halides,and aromatic ring-containing compounds.The yield of benzene polyacids has an absolute advantage in the oxidation products.Based on the change of benzene polyacids,it was speculated that there were more methyl substituents connected to the peripheral structure of CLRE,and the degree of condensation of the condensed aromatic ring structure was lower.With the progress of oxidation,the methyl substituents in the internal structure of the CLRE gradually decrease and the degree of condensation of the condensed aromatic ring becomes higher.The oxygen and nitrogen in the CLRE were present in the condensed aromatic ring.Heteroatoms such as sulfur and halogen were mainly present in aromatic hydrocarbon side chains or as bridges connecting macromolecular aromatic hydrocarbon structures.Rapid pyrolysis experiments were carried out on CLRE at different temperatures(300-700 °C).The results show that: at 600 °C,the product types were the most.The relative contents of alkanes,arenes,alkynes,phenolketones,aldehydes,carboxylic acids and their derivatives containing oxygen,nitrogen/sulfur compounds and halogens reached the highest.