Vacuum distillation – crude oil refining under reduced pressure
Vacuum distillation is a key step in the refinery in which the residue from the atmospheric distillation of crude oil is further processed at lower pressure (vacuum). The aim is to use the vacuum to lower the boiling temperatures in order to gently separate heavier fractions such as lubricating oil base stocks, bitumen or fuel oil components – without thermally decomposing them.
Why is vacuum distillation so important for base oils?
While atmospheric distillation produces lighter fractions such as petrol or diesel, the heavy components are left behind. These are treated in vacuum distillation at low pressure so that they can be broken down at moderate temperatures.
This prevents thermal damage and provides the raw materials for high-quality lubricating oil products, such as those used in BASINOL engine oils, gear oils and industrial lubricants.
How does vacuum distillation work technically?
The principle is based on the physical law that liquids boil at lower pressure and lower temperature. In practice, the oil is fed into a vacuum distillation tower in which various heavy oil fractions are specifically vaporized and separated under controlled negative pressure – e.g. base oil fractions, wax bases or residues.
What are the advantages of vacuum distillation compared to atmospheric distillation?
Vacuum distillation is particularly gentle and prevents heavier components from coking, oxidizing or decomposing. This makes it indispensable for the production of high-quality lubricant base oils with defined viscosity, color brightness and oxidation stability. It is also an important preliminary process for downstream steps such as hydrocracking or hydrofinishing.
Is vacuum distillation only used for lubricants?
No. It is also relevant in the production of bitumen, kerosene waxes, vacuum gas oil and even as a raw material supplier for petrochemical plants. In the lubricant world, however, it plays a key role as a supplier of base oil fractions that are processed into API Group I, II or III oils in subsequent steps.
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