GB442061A - Process for the preparation of vanillin - Google Patents

Abstract

Vanillin is obtained from a eugenol-containing oil, e.g. clove oil or cinnamon oil, by heating the oil with caustic potash in less than 24 minutes to over 225 DEG C., preferably while stirring and with the addition of paraffin hydrocarbons. The potassium iso-eugenate is then dissolved in water, separated from the hydrocarbon, and subsequently oxidized with nitrobenzene at a temperature above 115 DEG but below 145 DEG C. The oxidation is carried out so that the concentration of the reaction mixture changes, i.e. volatile products are distilled off, and preferably the recovered oil from a previous oxidation is added to the reaction mixture. The reaction mixture (at approximately 120 DEG C.) is added to hot water, kept at 95 DEG C. for a short time, and quickly cooled to 18 DEG C. The solid vanillin is filtered off, washed with benzene, redissolved in hot water and filtered. The solution is then cooled to 18 DEG C. and acidified with acetic acid, and the crude vanillin recrystallized with the aid of active carbon. Further quantities of vanillin are recovered from the reaction solution. The water content of the mixture during the oxidation preferably varies from three times the eugenol-containing oil at the beginning to about one tenth of the oil at the end.