In a base oil production plant the operating conditions needed to produce products at a desired specification are very sensitive to feed quality.
Base oils are produced from Vacuum Gas Oils (HVGOs) and Deasphalted Oils (DAOs) which having different viscosity by aromatic solvent and solvent dewaxing. Feedstock having the same viscosity may have a very different composition depending on the crude origin and therefore these have to be refined by using different operating conditions in order to produce base oils at desired specification.
A way of defining the feed composition is to determine its hydrocarbon distribution (i.e. aromatic, naphthenic and paraffinic carbon content); this can be obtained off-line (ASTM D2140), or by laboratory high resolution 13C NMR.
Unfortunately the feedstock characterization can be only available one or two times a day and it is not actually possible to follow any fluctuation in quality.
Moreover, any change needed to correct an out of spec product required almost five hours.