RECOVERY OF AROMATIC AND BICYCLIC AROMATIC COMPOUNDS

Abstract

Light cycle oil (LCO), which is a product of the catalytic cracking of the vacuum gas oil in the FCCU, contains a good percentage of aromatics, monocyclic and polycyclic. These compounds need to be separated from the streams, as these are not very suitable in the further conversion units or can add value to the specialized streams. In this study, liquid-liquid extraction has been used to recover the aromatics (p-xylene) and bicyclic aromatics (naphthalene) from model oil. The efficacies of various solvents have been tested for recovery of aromatics and bicyclic aromatics. Equilibrium data have been presented for compound p-xylene and naphthalene using the solvents: dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP) and dimethyl formamide (DMF). Phase diagrams have been plotted for all these systems at the normal temperature of industrial separation which are very much important in the industries. Regression of the experimental points is done by NRTL and UNIQUAC equations. Qualitative analysis is done on the basis of distribution coefficients and separation factors and graphs are produced for the same. DMF was found to be very good solvent for recovery of p-xylene and naphthalene. Various solvents are tested for their suitability for the recovery of aromatics. Quaternary systems are studied for NMP and DMF systems and their efficiency for the recovery of bicyclic aromatic compounds is studied. NMP was found to have a very good separation factor and distribution coefficient for naphthalene. LSER model has been used to correlate the various physiochemical properties of the solvents to the distribution coefficients and separation factors.