High efficiency separation of olefin from FCC naphtha: Influence of combined solvents and related extraction conditions

Separation of olefin from fluid catalytic cracking (FCC) naphtha is a high way to protect the research octane number (RON) from a loss during hydrodesulfurization. Solvent extraction is a promising way to separate olefin and extract sulfides simultaneously. In order to realize effective separation of olefin from FCC naphtha, this paper focused on the development of a kind of high efficient solvent and optimization of corresponding operation conditions for olefin separation. The results showed the combined solvents consisted of sulfolane (95 v%) and N-methyl-2-pyrrolidone (5 v%) exhibited high separation capability for olefin, and the best solvent to oil ratio was 3:1. Based on the combined solvent and optimal solvent to oil ratio, the best olefin enrichment coefficient could be up to 97.63 indicating lots of olefin enriched in raffinate. The desulfurization efficiency exceeded 90% after 3-stage extraction by the combined solvents, which was close to and even prior to some kinds of ionic liquids. Moreover, the combined solvents exhibited remarkable stability, and variation of desulfurization efficiency of the combined solvents was only around 1% after recycled 8 times. These studies gave a high efficient way to upgrade clean gasoline by separating olefin and enriching sulfides from FCC naphtha.