US Patent 7186876 Process to prepare a process oil

A process to prepare a process oil with an aromatic content of more than 50 wt % (according to ASTM D 2007) and a polycyclic aromatics (PCA) less than 3 wt % (according to IP 346) by (a) contacting a feed mixture of a petroleum fraction boiling in the lubricating oil range and an aromatic rich hydrocarbon fraction with a polar solvent in a counter-current liquid-liquid extraction column, wherein the process oil is obtained by removing the polar solvent from the top product and an extract is obtained by removing the polar solvent from the top product and an extract is obtained by removing the polar solvent from the bottom product.