Process for the decarboxylative ketonization of fatty acids or fatty acid derivatives

A process P for the decarboxylative ketonization of fatty acids, fatty acid derivatives or mixtures thereof in liquid phase with metal compounds as catalysts, the process comprising:

• a) in a first step, elementary metal or a metal compound, said elementary metal or metal compound being selected from the group consisting of iron, iron (II) oxide, a mixed oxide of iron (II) and iron (III), magnesium and magnesium oxide, and at least one fatty acid, at least one fatty acid derivative or a mixture thereof comprising at least 10 mol %, based on the entire amount of fatty acid or fatty acid derivative, of fatty acid having 12 carbon atoms or less or derivative of fatty acid having 12 carbon atoms or less, are mixed in a molar ratio of from 1:0.8 to 1:3.5, wherein the molar ratio is of the elementary metal or metal compound to the total amount of carboxylic groups in the at least one fatty acid, at least one fatty acid derivative or a mixture thereof, and reacted for a period P1 of from 5 min to 24 h at a temperature T1 which is above 270° C. and below 300° C. in the absence of added solvent, and
• b) thereafter the temperature is raised to a temperature T2 which ranges from 300° C. to 400° C., and additional fatty acid, fatty acid derivative or a mixture thereof comprising at least 10 mol %, based on the entire amount of fatty acid or fatty acid derivative, of fatty acid having 12 carbon atoms or less or derivative of such fatty acid, is added over a period of time P2 of from 5 min to 24 h in the absence of added solvent until the molar ratio of the elementary metal or metal compound to the total amount of carboxylic groups in the at least one fatty acid, at least one fatty acid derivative or a mixture thereof is in the range of from 1:6 to 1:99.