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

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-methylthiophene and 3-methylthiophene) 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 methylthiophene 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.