Removal of naphthenic acids from crude oil using amino acid ionic liquids

[Display omitted] ► Amino acid based ionic liquids can be used to remove naphthenic acids from crude oil. ► Both reactive and physical extraction reduces the total acid number. ► The reaction mechanism involves the formation of a zwitterionic species. ► The zwitterionic species can be reacted with carbonic acid to reform the ionic liquid. ► Successful multistage recycling of the ionic liquid has been demonstrated. A number of tetraalkylammonium and tetraalkylphosphonium amino acid based ionic liquids (AAILs) have been successfully used and recycled for the reactive extraction of naphthenic acids from crude oil and crude oil distillates. Spectral studies show that the mechanism by which this occurs is through the formation of a zwitterionic complex. Therein, the amino acid anion plays a key role in the formation of this complex.