Purification and total acid number reduction of raw diesel via column chromatography

Abstract

Crude petroleum products have impurities that are harmful to industrial equipment, vehicles, and the environment. The American Society of Testing and Materials (ASTM) is a regulatory body that controls the standards for different classes of fuel. These regulations can include acidity, sulfur content, flash point, and many more parameters. ASTM has different standards depending on the type of fuel. For example, diesel that is used in vehicles that are driven on streets is known as road going diesel and has the designated class of ASTM D975. In this research, the standards for ASTM D975 will be used. An unrefined diesel product provided by an industrial collaborator will be upgraded to reach the ASTM standards for acidity and sulfur content. Also, the industrial collaborator asked us to improve the colour and smell of the diesel. Acidity is measured by the total acid number (TAN) with the units of mg of KOH per g of diesel. The TAN value was lowered through acid-base neutralization using different conditions. These conditions include various temperatures, solid KOH, and different concentrations of aqueous KOH solutions with or without a phase transfer catalyst (PTC). A novel technique of using column chromatography was developed to purify the diesel. This technique greatly improved the colour and smell, with colour ranging from an initial brown colour to green or colourless. The odour could be converted to a petroleum like odour from a strong initial camp fire burning aroma. The column was optimized to be run without solvent and the stationary phase recycled. The column can purify up to 800 mL of diesel per 100 g of silica gel and has a recovery of 70%. The TAN value was also reduced to less than 0.03 mg of KOH per gram of diesel using this method of purification.