Separation Rule Of Aromatics/Cyclichydrocarbon In Coal Liquefaction And Its Mechanism In Separation

Producing liquid fuel from raw coal is analternative method to alleviate shortage of liquid fuel. The main composition of coal liquefied oil are aromatic hydrocarbon and its derivatives(60-70%), saturated hydrocarbon(25%), olefin and heteroatomic compound(<10%). For the higher density and lower reactivity, aromatic hydrocarbon and its derivatives largely existing in coal liquefied oil are easily to be cracked and coke under high temperature if the coal liquefied oil used as liquefied fuel directly. As a result, various countries set the value of 18% as maximum content of aromatic hydrocarbon in fuel. Thus, separating or enriching aromatic hydrocarbonof coal liquid effectively is critical work of coal liquefied oil purification, which can improve conversion rates of aromatic hydrocarbon, control content of aromatic hydrocarbon, optimize properties of fuel and decrease hydrogen consumption.In order to study approach of separation process, methylbenzene and methylcyclohexane, which riched in the 200～220℃fractions of Shenhua coal liquefied oil, was selected as model compounds to study the phase equilibrium rules of the extracting agent.Usingγ-butyrolactone as an extraction agent, the ternary equilibrium phase of methylenenzene and mehtylcyclohexane was diagramed. Furthermore, the amount ofγ-butyrolactone used in extraction was calculated based on the ternary diagram. The equilibrium parameters were measured by D-B apparatus in the different experiment condition. The results showed the best separation was at the solvent ratio of 0.5:1 and toluene less than 60%. According to the caculation of Aspen, the coefficient of these three mixture phase was the most existed between toluene andγ-butyrolactone. It is proved by the quantum chemistry calculation that the separation mechanism was from the inter-molecular force. Different steric hindrance of methylcyclohexane and toluene leads to different inter-molecular force withγ-butyrolactone and the changes of relative volatility. These results in the separation of toluene and methylcyclohexane easily.