Conceptual process design for aromatic/aliphatic separation with ionic liquids

Presently, there are no processes available to separate low concentration (<20%) aromatic hydrocarbons from mixed aromatic aliphatic hydrocarbon streams, such as a feed stream to naphtha crackers, which may contain 10–25% of aromatic components, depending on the source of the feed (naphtha or gas condensate). Present practice is removal of the aromatic hydrocarbons from the C5+-stream in the naphtha cracker by extractive or azeotropic distillation. If a major part of the aromatic compounds present in the feed to the crackers could be separated upstream of the furnaces, it would offer several advantages: higher capacity, higher thermal efficiency and less fouling. The improved margin will be around €20/t of feed or €48 million per year for a naphtha cracker with a feed capacity of 300 t/h, due to lower operational costs.Extraction with sulfolane will result in a negative margin of €10 million per year. Therefore, a conceptual process for the extraction of aromatic hydrocarbons with the ionic liquid 4-methyl-N-butylpyridinium tetrafluoroborate was developed using ASPEN. The investment costs are estimated to be €56 million and the annual costs about €28 million per year, resulting in a positive margin of about €20 million per year.