SELECTIVE DIMERIZATION OF BENZOTHIOPHENE USING SUPPORTED ALUMINUM SULFATE UNDER SUPERCRITICAL CO2 CONDITIONS

Dimerization reactions of benzothiophene were performed using 10 wt% A l-2(SO4)(3) supported on porous silica gel as a solid acid catalyst un der atmospheric or supercritical CO2 conditions, in order to purify na phthalene as well as to separate and recover benzothiophene(BT). BT wa s more selectively dimerized under supercritical CO2 conditions (100 d egrees C, 100 atm) than in atmospheric octane solution at the same rea ction temperature, allowing its selective dimerization even when mixed with naphthalene. Effects of reaction pressure, solvent, and reaction time on the dimerization selectivity were examined based on the analy ses of recovered fractions and products. Five types of benzothiophene dimers were identified, being produced more selectively under the supe rcritical CO2 conditions. The dimers were easily converted to BT monom er by heating to around 250 degrees C, suggesting the possibility of r ecovery of BT from crude naphthalene. (C) 1998 Elsevier Science B.V.