The isobaric (vapour + liquid) equilibrium (VLE) of N-formylmorpholine with aromatics (ethylbenzene, n-butylbenzene, isopropylbenzene, 1,2,4-trimethylbenzene) at 101.33 kPa was investigated. The experimental VLE data for the four binary systems were tested and verified to be thermodynamically consistent by the Herington analysis method. At the same time, the non-random two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) activity coefficient models were used to correlate the experimental data with temperature-independent parameters. The average absolute deviations of the temperature correlated by NRTL model and UNIQUAC model for all the systems are below 0.62 K and the average absolute deviations for the vapour phase compositions are all below 0.083. In addition, the UNIFAC (Do) group contribution model was used to correlate and estimate the VLE data. The N-formylmorpholine was treated as a group (NFM). The group interaction parameters for CH2-NFM, ACH-NFM and ACCH(2)-NFM were regressed. The UNIFAC (Do) model can correlate the experimental data well. The group interaction parameters were used to estimate VLE data of the (o-xylene + N-formylmorpholine), (m-xylene + N-formylmorpholine) and (p-xylene + N-formylmorpholine) binary systems. The estimated data fit well with the literature data. The average absolute deviations of the temperature for N-formylmorpholine with (o-xylene, m-xylene, p-xylene) are 1.67 K, 1.77 K and 1.35 K, respectively, and the average absolute deviations for the vapour phase compositions of o-xylene, m-xylene and p-xylene are 0.0133, 0.0057 and 0.0059, respectively. (C) 2012 Elsevier Ltd. All rights reserved.