Process P1 for the manufacture of a secondary fatty alcohol, said process P1 comprising synthesizing an internal ketone K1 by a process P0 comprising the decarboxylative ketonization reaction of a fatty acid or the like in a liquid phase with a metal compound as catalyst in a reaction medium, wherein a ketone K2 at liquid state, which is identical or similar to the internal ketone K1, is introduced into the reaction medium, and subjecting the internal ketone K1 to a hydrogenation reaction with hydrogen gas as hydrogenating agent to form the secondary fatty alcohol. Use of the secondary fatty alcohol manufactured by the process P1 for the manufacture of an internal olefin or of an internal olefin sulfonate.