Due to insufficient capabilities for the solvent extraction in the Czech Republic, a technology for lube base oil production, comprising HP hydrocracking on existing equipment (originally designed for brown coal tar processing) and solvent dewaxing has been developed since the late fifties, resulting in the manufacture of high quality products. High flexibility in the lube oil components viscosity has been achieved by the development of a special catalyst and by using five types of vacuum gas oils of different viscosities as feedstocks. In order to maximise the utilization of the liquid products from a Hydrocracking unit for lube oil production and, furthermore, to widen the viscosity range, a unique vacuum distillation of the products has been developed, which makes it possible to withdraw five side cuts with viscosities in the range from 2 to 20 mm~2/s at 40 °C. The cuts with viscosities up to 15 mm~2/s at 40 °C have good low temperature properties without dewaxing. The cuts and residues with higher viscosities have to be dewaxed by a MEK-toluene mixture, yielding different grades of refined paraffin waxes as by-products.The stability of hydrocracked oils are considerably influenced by the remaining polyaromatics content, which depends on the feed quality and hydrocracking unit operating parameters. Desired properties of the resulting base lube oil components, including their oxidation stability, are achieved both by their manufacturing on three levels of viscosity index (95, 105, 130) and by mixing them with components manufactured by the selective extraction.
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