Long‐chain phenols. Part 231 practical separations of the component phenols in technical cashew nut‐shell liquid (Anacardium occidentale): Distillation procedures for obtaining cardanol

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Abstract
The separation of cardanol from cardol and coloured impurities in technical cashew nut‐shell liquid (CNSL) has been examined by molecular and vacuum distillation and the purity of fractions carefully assessed by thin‐layer, gas‐liquid and high‐performance liquid chromatographic analysis. A small 10‐stage rotary still (Vitamins‐Watt type) produced cardanol (99%) in approx. 58% yield with a total phenolic recovery between 80 and 90%. A falling film single‐stage still (Edwards type) gave less pure cardanol and a good total phenolic recovery. Prerequisites to avoid polymerisation in conventional vacuum distillation were wide‐bore vacuum equipment and a nitrogen leak. Excessive flask and surface temperatures resulted in only a 70% total phenolic recovery, the cardanol fractions being approx. 90% pure. With a lower flask and surface temperature, by the use of a liquid‐heating bath, the total phenolic recoveries were better than those in molecular distillation and the cardanol fractions (60 %) were 90–95 % pure. The procedure of slow addition enabled the scale of apparatus to be reduced. The distillation of hydrogenated technical CNSL appeared less satisfactory than that of the unsaturated material.

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