Continuous extraction of naphthenic acid from low-grade oil using 1,6-hexanediol in an ammonia solution

•Searching for the best solvent for the acid removal from the High-Acid Crudes (HAC)•The previous computational solvent selection study was verified using an experimental study.•Solvents were tested using a batch-type and bench-scale continuous removal apparatus.•1,6-hexanediol with 3% ammonia solution was found to be the best solvent.•Regeneration scheme was suggested.