Corrosion Analysis on Acidic Crude Oils using FT-ICR

Published February 25, 2020

A new method to characterize crude oil corrosion shows that corrosion in acidic crude oils depends on the specific structures of the acid molecules, information that can help improve oil valuation and refining.

What did scientists discover?

Organic acids in petroleum are known to corrode iron pipes in oil refineries. However, the corrosion rate does not correlate well with the acid content of the oil, which suggests that only a fraction of the acids contribute to steel corrosion. This new method to characterize the initial acids and the subsequent products formed from acid corrosion can reveal the reactive acid species. This information can be used to better improve oil valuation and refining.

We show that corrosion in acidic crude oils depends on the specific structures of the acid molecules. Acids with fewer rings and double bonds in their structure are more corrosive.

Why is this important?

"Opportunity crudes" are those crude oils available at discounted price due to higher concentration of organic acids (naphthenic acids). Naphthenic acids cause corrosion in the steel pipes of oil refineries at a cost of ~ $1 billion annually. The acids react with iron in the steel to form oil-soluble iron naphthenates, which decompose at refinery temperature to yield oil-soluble ketones and oil-insoluble iron and magnetite (Fe₃O₄). Each ketone is composed of the two acids that initially reacted with iron to form the iron naphthenate, so analysis of the ketones formed reveals which specific naphthenic acids reacted with iron. Not all acids are equally corrosive, so this knowledge can be used to provide more accurate oil pricing and better refinery strategy.

Who did the research?

Krajewski, L.C.^1,2, Robbins, W.K.², Corilo, Y.E.¹, Bota. G.⁴, Marshall, A.G.^1,3, and Rodgers, R.P.^1,2,3

¹ICR User Facility, National High Magnetic Field Laboratory ²Future Fuels Institute (FFI) ³Department of Chemistry and Biochemistry, Florida State University ⁴Inst. for Corrosion and Multiphase Tech, Ohio University

Why did they need the MagLab?

There are tens of thousands of different naphthenic acids, so the ultrahigh resolution mass spectrometers at the Maglab are required to resolve and identify the original unreacted naphthenic acids and the ketone products.