351.     ------.  [BRIDGEWATER, R. M.]  British Research on Petroleum Substitutes.  VII.  Synthetic Lubricating Oils.  Petroleum (London), vol. 8, 1945, pp. 136, 152-153.

    First gives some consideration to the existing knowledge concerning the composition and the chemical and physical properties of lubricating oils derived from petroleum.  The absence of real knowledge as to the physical and chemical properties required in a lubricating oil has been a major difficulty in researches on synthetic lubricating oils.  The various raw materials available for the manufacture of synthetic lubricating oils are:  Coal-carbonization products, including tar fractions and C₂H₄; products of the pressure hydrogenation of coal or tar; and the primary products of the Fischer-Tropsch process.  The principal methods for producing lubricating oils from these products are:  Isolation of suitable fractions by distillation or solvent extraction; stabilization of such fractions by hydrogenation; polymerization of hydrocarbons, especially olefins, with or without catalysts; chlorination of hydrocarbons, especially high-boiling paraffins, followed by dechlorination; condensation of chlorinated hydrocarbons or olefins with aromatic hydrocarbons.  Lubricating oils from the neutral-oil fractions of low-temperature tar were unsatisfactory, even after hydrogenation over a Mo catalyst.  The viscosity was too low at the higher temperatures, and there was too great a tendency toward oxidation and carbonization.  Better results might be attained by using the superior hydrogenation catalysts subsequently discovered.