Petrochemical refiners often utilize discounted opportunity crudes as a way to improve their margin spread. The varieties of these cheap crude oils on the market continue to grow in number, but they have hidden risks for the refining industry caused by factors such as high naphthenic acid and sulfur content. Sulfur compounds and naphthenic acids are among the substances that contribute to the corrosive nature of crude oils and petroleum products. This is why processing crude oils with high naphthenic acid and sulfur content increases the risk of corrosion. The refiner must balance the cost benefit versus the risk and the cost of corrosion control when processing high TAN crudes.

A reliable total acid number (TAN) determination is a crucial part of crude oil corrosion control. Guest authors Bert Thakkar, Bryce McGarvey, and Colette McGarvey of Imperial Oil, and Larry Tucker and Lori Carey of Metrohm USA were involved in the development of the ASTM Method D8045 for acid number determination. Here, they explain the method.

The White Paper discusses the following points:

• Issues of sulfur and naphthenic acid corrosion (NAC)
• Corrosion control by monitoring the acid content of the crude oil
• ASTM D8045 as a precise and rapid analysis method of total acid number in crude oils, overcoming the limitations of traditional potentiometric titration according to ASTM D664
• Detailed description of the thermometric titration according to ASTM D8045
• Data showing how potentiometric and thermometric titration according to ASTM D664 and D8045, respectively, correlate

For further insights into this method, watch the video below explaining the principle of thermometric titration and how the analysis of the acid number according to ASTM D8045 can be performed.