Introduction Of The Group Contribution Concept Into The Nrtl Model

摘要

Generally the NRTL activity coefficient model has shown great capabilities inrnpredicting liquid-liquid or liquid-vapour phase equilibria. However its major drawbackrnis the non availability of the required molecular interaction parameters for a hugernnumber of chemical systems. Therefore in the present work, a group contributionrnapproach is introduced into the initial NRTL to give the GC-NRTL (Group ContributionrnNRTL) model. It is simply based on calculating group interaction parameters accordingrnto the NRTL equation, by minimizing an objective function made of the sum of thernsquared differences between the calculated values and the experimental ones reported inrnthe literature. The minimization method is based on the Genetic algorithm which hasrnproven to be very performing in reaching the optimum. As an illustration, the GCNRTLrnmodel was tested for 8 binary liquid- liquid systems mainly involving currentrnfunctional groups like CH, CH2, CH3, OH, COOH, ACH, ACOH, ACCH3, NO, etc. Thernagreement between the predicted results by means of the GC-NRTL and thernexperimental phase equilibrium data is encouraging and the interaction parameters tablernshould be completed to include a greater number of functional groups.