Just Say No to Light, Sweet Crudes


LONDON – Crude price doesnt correlate to lubricant base oil yield or quality. Rather, paraffin content is key, and Asia is home to some of the worlds best lube crudes.

Crude is 85 to 90 percent of the cost of a barrel of base oil we make, said Amy Claxton, principal of consultancy My Energy. Light, sweet, expensive crude may or may not be good for base oil. The base oil refinery will prefer lower-priced Arab light or heavy.

Claxton, based in Hummelstown, Pa., described the impact of crude selection on base oil yield and quality at the ICIS World Base Oils & Lubricants Conference here last week.

Every crude is a unique mixture of molecules, said Claxton, mostly alkanes (or paraffins – a high concentration means paraffinic crude), cycloalkanes (or naphthenes – a high concentration means naphthenic crude), and aromatic hydrocarbons (a high concentration means fuels only).

Every molecule in the crude has a viscosity index, and crude is the starting point for VI, which is raised through the refining process. Crudes with higher paraffin and iso-paraffin content give higher yield and/or higher VI after processing as base oil.

Low paraffin crudes, like Alaska NS, Nigeria Light, Gullfaks from the North Sea, and Maya, give poor base oil yields, Claxton continued. These crudes are uneconomical for solvent processing or for API Group III base oils, although they can be useful if hydrotreated to reach Group II, but at a yield debit.

By comparison, mid-to-high paraffin crudes such as WTI, Brent, Arab Extra Light and Tapis, offer an economic advantage for solvent processing or hydrotreating. You get higher yield, higher VI, or both, Claxton noted. And the highest VI crudes provide economical Group III.

Crude pricing is related to two key properties: API gravity and sulfur content, said Claxton, and the reason is fuels refining economics. They are indicators of the difficulty to refine and the yield of fuel products. Crude pricing reflects refining intensity to make fuels, and is not necessarily a reliable indicator of base oil economics.

What the base oil refiner looks for, she said, is the paraffin content of the vacuum gas oil fraction. Molecular composition is the better indicator of crude value for lubricant economics.

The best crudes for lubricants are not evenly distributed around the world, Claxton said. Most Middle Eastern crudes are paraffinic, lube-friendly crudes, while most American and European crudes are suitable for fuels only. And, she continued, some paraffinic crudes are better than others.

Asia is cost-advantaged for high quality base oil production, Claxton said. For example, Indonesias Minas crude, Malaysias Tapis and Chinas Daqing are 70 to 75 percent paraffins. In the Middle East, Arab Light and Murban are 60 to 65 percent paraffins. This contrasts with some crudes from the Americas with paraffin composition as low as 25 percent.

The molecular fingerprints of crudes and their locations determine where the API Groups [of base stocks] are produced, Claxton concluded. Asian crudes facilitate production of extremely high quality Group III and III-plus. North America, with its hydrotreating technologies, is a major producer of Group II as well as a Group I producer. And the rest of the world primarily produces Group I.

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