Retardation of asphaltene precipitation by addition of toluene, resins, deasphalted oil and surfactants

The aim of this work is to test the possibility of using deasphalted oil (DO) or resin (R) obtained from Kuwaiti crude to inhibit the asphaltene precipitation from such crude when n-heptane is added. The inhibition effect of toluene (T) and selected surfactants is also tested. Surfactants used are nonyl phenol (NP), dodecyl benzene sulfonic acid (DBSA). and dodecyl resorcinol (DR). The retardation of asphaltene precipitation with addition of inhibitor is found to be in the order: DR > DBSA > NP > R > T > DO. These results show that toluene and DO are not effective inhibitors. Their effect on the onset point becomes appreciable only when their mass fraction in the oil exceeds 60%. The resins have modest inhibition effect. The strong inhibition effect of the surfactants is due to the interaction between the acidic head of these molecules and the asphaltene. The mechanism of inhibition is explained in terms of the micellization model of Victorov and Firoozabadi. Onset point for asphaltene precipitation with n-heptane addition is calculated in the presence of different amounts of inhibitor. Calculated results agree well with experiment. It is possible by using the micellization model to predict the amount of inhibitor required for reaching a certain onset point. (C) 2002 Elsevier Science B.V. All rights reserved.