萃取精馏分离甲苯和甲基噻吩中萃取溶剂的选择

Selection of extraction solvents in extractive distillation of toluene and methyl thiophene

在一系列萃取溶剂存在下,通过测定常压气液平衡试验数据来计算甲苯与甲基噻吩的相对挥发度,并且以相对挥发度为评价指标,考察了单一萃取剂对甲苯与甲基噻吩分离过程的影响,从而研究分离纯化由焦化苯中得到的甲苯与甲基噻吩(2-甲基噻吩和3-甲基噻吩)时所需要的萃取溶剂。结果表明:以N-甲基吡咯烷酮为萃取剂且溶剂体积比为7时,甲苯与甲基噻吩的相对挥发度能够有很大的提高,在萃取精馏中能够使分离达到最好的效果。还对N-甲基吡咯烷酮的稳定性进行了检测,在常压下连续加热沸腾24 h后,纯度没有变化,即没有分解,稳定性好。在萃取精馏塔中全回流测定,N-甲基吡咯烷酮与甲苯不共沸。

The vapor-liquid equilibrium （VLE） data at atmospheric pressure were determined in the presence of several extraction solvents for calculating the relative volatility. The effect of single extraction solvent on the separation toluene and methylthiophene was assessed based on the relative volatility, thus the solvents available for separating toluene and methylthiophene （2-methyhhiophene and 3-methyhhiophene） were investigated. The results show that when using N-formylmorpholine as an extraction agent and the volume ratio of solvent to feed is 7, the relative volatility between toluene and mettwlthiophene can be greatly improved, and the optimal separation effect and economic benefit can be achieved. The stability of N-formylmorpholine was tested under continuous heating at atmospheric pressure for 24 h, and there was no change in purity, showing a good stability; there was no N-formylmorpholine in the top of the extractive distillation column with total reflux, so N-formylmorpholine and toluene are not azeotropic.