Solvent demetallization of heavy petroleum feedstock using supercritical carbon dioxide with modifiers

Abstract Possibilities of demetallization of heavy petroleum feedstocks (HPF) using supercritical fluid extraction (SFE) have been studied. Experiments with various solvent mixtures were carried out in a semibatch extractor and in dynamic mode to assess the effect of modifier type and concentration as well as extraction time on the yield of extract and content of vanadium, nickel and iron in produced phases (extract and residual phase). Vacuum residue was used as the feedstock and supercritical carbon dioxide (scCO 2 ) was used as the primary solvent for extraction. Methanol, ethanol, acetonitrile, acetone, ethyl acetate, n -heptane, toluene and o-xylene were added to scCO 2 as modifiers to form the solvent mixtures. Extraction temperatures and pressures were maintained at 50 °C and 30 МPa to achieve a high density of scCO 2 . It has been found that methanol and o-xylene containing mixtures provide the highest metal content in the extract while ethyl acetate, n -heptane and toluene provide the lowest. Higher extract yield and the degree of metal concentration in residue were obtained with increasing both toluene concentration in scCO 2 and the time of dynamic extraction. The demetallization efficiency is estimated to be at a level above 95wt % at the yields of extract (demetallized oil) up to 60wt % using toluene as a modifier.