Syntheses And Studies Of Magnetic Ionic Liquids Extracting Asphaltenes From Coal Direct Liquefaction Residues

Coal direct liquefaction residues （CDLR） as by-products of the directliquefaction process of coal hydropyrolysis usually account for about30wt%of coal, containing about30wt%heavy oils,25wt%asphaltenes and45wt%other substances. Among them, CDLR contains polycyclic aromatichydrocarbons components （asphaltenes）, which is an important feedstock toprepare high-added value carbon materials. But due to the problems fromseparation Techniques, the nowadays main measures to utilize the residues aregasification for hydrogen production, combustion providing heat andcarbonization and so on, which have low-added value and also causeenvironmental problems. Thus, it is terribly essential to look for an effectiveseparation method to extract asphaltene fractions from CDLR.Compared with traditional solvents （benzene, toluene， pyridine，tetrahydrofuran and benzopyridine）, ionic liquids （ILs） are used as greensolvents or excellent media due to their unique physicochemical properties,such as wide liquid range, non-volatility, thermal stability, synergistic effect,designability and so on. Iron-containing magnetic ILs not only have aboveexcellent properties but also exhibit an unexpectedly strong response to anadditional magnetic field, which make them have more advantages to extractasphaltenes from CDLR.Based on the asphaltenes separation recycling for purpose, and theasphaltenes of polycyclic aromatic hydrocarbons structure and solvent similarcompatible principle, three kinds of iron-containing magnetic ILs withdifferent cationic rings were synthesized in experiments, including1-butyl-3-methylimidazolium tetrachloroferrate （[bmim]FeCl₄）,N-butylpyridium tetrachloroferrate （[bPy]FeCl₄） and1-butyl-1-methylpyrrolidium tetrachloroferrate （[bmP]FeCl₄）. By the temperature control of the stirrer tanks device and the vacuum filter toseparate, the effects of the three synthesized magnetic ionic liquids （MILs）extracting the asphaltenes are investigated on trials to observe the differentmaterial ratios, different dissolving temperatures and different dissolvingtimes of CDLR to MILs systematically. Through the extraction process andthe analysis of the three extracts, the results show that under the sameconditions of the material ratio （1:5）, dissolved time （30min） and the solubilitytemperature （50℃）, the extraction yield of [bPy]FeCl₄is highest among threeMILs; In the three extracts, the extract of [bPy]FeCl₄has the highest carboncontent （88.71%）, the largest average molecular weight Mw （11397） and thesmallest polydispersity （1.290）; In the three extracts, the extract of [bPy]FeCl₄has the largest ratio of C/H （1.43） and the highest aromaticity fa（0.75）.Therefore, pyridine-based iron-containing magnetic IL is more feasible andpreponderant to extract asphaltene fractions from CDLR.