Utilization of bio-oil from corncob pyrolysis for aromatic extraction in raw lubricant oil

Corncob is one of the biomass wastes which has abundant amount in Indonesia. Through pyrolysis, corncobs can be converted into bio-oil containing compounds such as furans and phenolics, which can be utilized as extractants of aromatics in raw lubricant oil. In high temperature, the aromatic content in engine lubricants can affect physical properties of the lubricants causing wearing on engine parts. The objective of the present research is to investigate effect of the weight ratio of extractant (solvent) to raw lubricant oil and the composition of aromatic in raw lubricant oil on the extent of aromatic extraction. The former work used extractants of bio-oil containing furans and phenolics, furfural and phenol for comparison, while the latter used extractant of bio-oil containing furans and phenolics. Pyrolysis has been done in a stirred tank reactor with a heating rate of 5°C/min and a maximum temperature of 500°C. Bio-oil from the pyrolysis contained many low molecular weight oxygenates dominated by carboxylic acids, which comprise 37% volume of bio-oil. Combined fractions of furans and phenolics have been isolated from bio-oil as bottom product from centrifuge and it comprises 5% weight of the original bio-oil obtained from pyrolysis of biomass. The bottom product to be used as aromatic extractant contained guaiacol (41.69%), phenol (27.29%), and furans (12.77%), with no carboxylic acid detected. The weight ratio of extractant to raw lubricant oil was varied 1:1, 2:1 and 3:1 with a constant initial weight composition of aromatics of 60%, and the initial weight composition of aromatics in raw lubricant oil was varied 30%, 45% and 60% with constant weight ratio of extractant to raw lubricant oil of 1:1. As the raw lubricant oil was a commercial lubricant and as an aromatic compound model was p-xylene. The aromatic extraction was performed at constant temperature of 40°C for 60 minutes. Aromatic extraction by furfural and bio-oil solvent shows that the greater solvent to lubricant ratio resulted in less raffinate yield, but more extraction intensity. Aromatic extraction by phenol shows that the greater solvent to lubricant ratio resulted in more raffinate yield and the extraction intensity reached minimum value as this ratio was 2:1. Aromatic extraction by bio-oil solvent shows that the more initial amount of aromatics in lubricant resulted in more raffinate yield, but less extraction intensity.