Naphthenic acid removal from crude oil by liquid-liquid extraction using ionic liquids.

The global low acidic crude oil is gradually depleting as it is one of the main sources
in fulfilling global energy demand. High acidic crude oil is still in abundance which
allows it to have a significant potential to replace low acidic crude oil. However, high
acidic crude oil poses significant problems whereby it causes complications in oil
refineries such as corrosion problems which will lead to various equipment failure. This
is due to the high amount of naphthenic acid present in the crude oil. In order to use the
crude oil safely, naphthenic acid removal is necessary. However, the current available
techniques pose serious problems such as the conventional method producing a large
amount of waste and the treated crude oil still contains high acid content. Ionic liquids
as designer solvents act as a positive prospect in naphthenic acid extraction. In this
study, eight (8) ionic liquids have been successfully synthesized namely piperidinium
and pyrrolidinium based ionic liquids with different anions which are
trifluoromethanesulfonate, phenolate and dicyanamide. Naphthenic acid extraction
from model oil using the synthesized ionic liquids were studied by using two different
techniques which are the mechanical stirring and ultrasonic assistance. Extraction study
at various ionic liquid/model oil ratio was performed where the initial and final amount
of naphthenic acid in model oil were determined. The piperidinium based ionic liquid
with phenolate anion showed the best potential to extract the naphthenic acid from
model oil. It is able to completely remove all the acid at a small amount of ionic
liquid/model oil ratio of 0.010 and 0.0025 for the mechanical stirring method and
ultrasonic assistance method, respectively. Ultrasonic assistance shows a remarkable
potential in enhancing the extraction efficiency of naphthenic acid. Study on effect of
ultrasonic parameters namely ionic liquid/oil ratio, amplitude and time were also
conducted using response surface methodology (RSM).