A FEw of the many advantages in favour of the use of anhydrous phenol as a selection solvent refining agent for petroleum distillates may be summarised as follows (1) Phenol does not react with the oil or decompose under any condition encountered in the extraction process. (2) The miscibility temperature of phenol and lubricating distillates is relatively high. Phenol treating is carried out at temperatures (100-200 F.) which can be attained with the expenditure of comparatively little energy. Hence the phenol process is very flexible, and may be applied to a large variety of charge stocks. (3) Phenol has a sharply defined preferential solubility for the undesirable components of a distillate, as shown by its ability to bring about excellent improvements in viscosity index, carbon residue, Sligh oxidation and sulphur content. (4) The density and solubility of phenol at the treating temperatures are such that well-defined extract and raffinate layers quickly separate. (5) The separation of the phenol from the oil is accomplished very easily by distillation. (6) Phenol treatment reduces or eliminates acid finishing. (7) The treating plant does not require any unusual equipment, and it can be operated by three men. Consequently, labour and investment costs are small. (8) The most striking feature of selective solvent refining with anhydrous phenol is the unique ability of phenol to produce, economically, high-grade finished lubricating oils, capable of withstanding the most exacting laboratory and service requirements from comparatively low-grade flash coil distillates. For the past two and a half years the Imperial Oil Refineries at Sarma have been producing automobile, aeroplane, transformer and turbine oils of very high quality, as well as a number of specialty oils, and producing these oils from Colombian distillates. The cost of processing these oils is low because the phenol treating expenses are moderate, and definite savings have been made in the cost of finishing as compared to the regular method of acid and clay treating.
Modern practice in the refining of lubricating oils has, from necessity, been directed towards the utilisation of low-grade distillates for the production of high-grade finished oils. Until comparatively recent times such a practice has been impossible because of the limited methods of treating at the disposal of the refiner. The introduction of phenol as a selective solvent in the refining of such distillates has greatly increased the number of types of distillates which can be profitably used to produce high-quality lubricating oils. In addition, this method of treating is especially suitable for the production of oils which must possess unusual characteristics-for example, insulating oils, aeroplane oils, turbine oils, etc.