
205Refining Processes for Used Oil Recycling to Base Oils or Fuels
patent document, compared with two virgin base stock oil results. Based on the
properties in the table, it was claimed that the re-rened oils were indistinguishable
from the virgin base stock oils. No information was provided on the sulfur content or
polynuclear aromatic hydrocarbon (PAN) levels in the product oils.
7.6.3 the snaMPrOgetti PrOcesses
The rst patent from 1979 (German patent DE 29 01 090 dated July 19, 1979; US Patent
4,406,778 dated September 27, 1983) was widely patented in Europe at a time when
the move away from acid and clay treatments for the re-rening proc ...