Acid number in crude oil and mineral oil products

The acid number is an important parameter for the quality control and price determination of crude oils and mineral oil products. It permits important conclusions to be drawn about the quality of crude oil and refinement.

Products with only slightly higher acid numbers have greater corrosion potential and lead to higher costs during later processing, which is why they are also traded at lower prices.

Balancing risk with opportunity

Discounted opportunity crude oils have the potential to dramatically improve refinery operating margins and bring a significant increase in profitability to the refining industry overall. By mixing opportunity crude with well-defined samples, refineries can cut raw material costs and drive up margins on refined products. Despite their potential economic advantages, these opportunity crudes are discounted due to the risk associated with processing petroleum products that contain increased levels of naphthenic acid. More and more opportunity crudes are introduced to the market every year illustrating the need for a better method to reduce the transactional risk between buyers and sellers.
Even if a refinery is not interested in rolling the dice with opportunity crudes, their own operation is continuously at risk from damaging corrosion. A NACE-sponsored federal corrosion report remains the landmark study, estimating annual cost of corrosion in U.S. refineries at $3.7 billion. The report’s gap analysis estimates a direct profit loss ranging from $2 to $12 billion due to interruption in refinery operations caused by corrosion-related shutdowns.1 Refinery and terminal management is tasked with balancing potential revenue with the refinery infrastructure risk and cost of corrosion control when choosing to accept opportunity crudes or certain petroleum products.

The need for a better acid number test

Monitoring acid number (AN) in crude oil and petroleum products remains the benchmark for evaluating the risk of processing opportunity crude oils and for adjusting refinery protocol to accommodate corrosive petroleum products. Traditional potentiometric methods, written to address acidity in lubricant products, require large amounts (up to 120 mL) of solvent and extensive electrode care procedures. Poor solubility of crude products, especially asphaltic, paraffinic, and bitumen materials, causes electrode fouling and inaccurate acid number results via potentiometric techniques. In 2008, key petroleum industry leaders requested a new test method from ASTM. As a member of ASTM, Metrohm partnered with the industry to develop method D8045, a thermometric titration standard that addresses these challenges while improving analysis time and reagent expenditure.

White Paper WP-013EN

This White Paper describes a rapid and reliable method for acid number determination according to ASTM D8045.

Download link below

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