Salting-Out Induced Aggregation for Selective Separation of Vanadyl-oxide Tetraphenyl-porphyrin from Heavy Oil

Abstract

This work presents a technique for separating vanadyl-oxide tetraphenyl-porphyrin, VOTPP, from heavy oil. This technique involves sequential separation of heavy oil and VOTPP from a solvent mixture of (4:1) volume ratio tetrahydrofuran, THF, and methanol upon stepwise addition of 1.0 M aqueous NaCl solution. Nevertheless, the salting-out of VOTPP from the solvent mixture was not NaCl specific, and many electrolytic solutions produced the same effect. The leftover concentration of heavy oil and VOTPP was determined using UV–vis spectroscopy following the Beer–Lambert law. Two bands were targeted, one at 549 nm and another at 700 nm. Both bands were assigned for heavy oil, and one, α band, at 549 nm was assigned for VOTPP. Accordingly, the leftover concentration of VOTPP was back calculated once the concentration of heavy oil was obtained from the absorbance measurement at 700 nm. Optimum separation required lower volume percent of NaCl at lower heavy oil concentration, and 10 vol % NaCl provided the best window for separation at 100 ppm heavy oil, while 20 vol % was needed for 1000 and 2000 ppm heavy oil.