A method for preparing (a) at least one cetylated fatty acid or a mixture of cetylated fatty acids comprising the steps of: placing at contact at least one fatty acid, cetyl alcohol and a metal catalyst in a chamber of a reactor in absence of solvent, to obtain a reaction mixture; followed by saturating the container using an inert gas bringing the container to a pressure P1 of about 1 atmosphere, applying a flow of said inert gas through said chamber; followed by applying a first heating ramp to said reaction mixture up to reaching a temperature T1 comprised from 120°C to 200°C at a pressure P1 of about 1 atmosphere and in the presence of the inert gas flow to initiate an esterification reaction with initial formation of said cetylated fatty acid or mixture of cetylated fatty acids and esterification water; followed by keeping said reaction mixture under stirring at said temperature T1 and pressure P1 for a period of time comprised from 10 minutes to 2 hours; followed by applying a second heating ramp to said reaction mixture up to reaching a temperature T2 comprised from 201°C to 260°C at a pressure P1 of about 1 atmosphere and in the presence of the inert gas flow to continue the esterification reaction with further formation of said cetylated fatty acid or mixture of cetylated fatty acids and esterification water; followed by keeping said reaction mixture under stirring at said temperature T2 and pressure P1 and in the presence of the inert gas flow for a period of time comprised from 4 hours to 12 hours; applying a vacuum program in the chamber which reduces the reaction pressure up to reaching a reduced pressure P2 comprised from 100 mbar to 10 mbar; (VIII) keeping said reaction mixture under stirring at said reduced pressure P2 and in the presence of the inert gas flow for a period of time comprised from 30 minutes and 4 hours to obtain complete formation of said at least one unrefined cetylated fatty acid or mixture of unrefined cetylated fatty acids. placing at contact at least one fatty acid, cetyl alcohol and a metal catalyst in a chamber of a reactor in absence of solvent, to obtain a reaction mixture; followed by saturating the container using an inert gas bringing the container to a pressure P1 of about 1 atmosphere, applying a flow of said inert gas through said chamber; followed by applying a first heating ramp to said reaction mixture up to reaching a temperature T1 comprised from 120°C to 200°C at a pressure P1 of about 1 atmosphere and in the presence of the inert gas flow to initiate an esterification reaction with initial formation of said cetylated fatty acid or mixture of cetylated fatty acids and esterification water; followed by keeping said reaction mixture under stirring at said temperature T1 and pressure P1 for a period of time comprised from 10 minutes to 2 hours; followed by applying a second heating ramp to said reaction mixture up to reaching a temperature T2 comprised from 201°C to 260°C at a pressure P1 of about 1 atmosphere and in the presence of the inert gas flow to continue the esterification reaction with further formation of said cetylated fatty acid or mixture of cetylated fatty acids and esterification water; followed by keeping said reaction mixture under stirring at said temperature T2 and pressure P1 and in the presence of the inert gas flow for a period of time comprised from 4 hours to 12 hours; applying a vacuum program in the chamber which reduces the reaction pressure up to reaching a reduced pressure P2 comprised from 100 mbar to 10 mbar; (VIII) keeping said reaction mixture under stirring at said reduced pressure P2 and in the presence of the inert gas flow for a period of time comprised from 30 minutes and 4 hours to obtain complete formation of said at least one unrefined cetylated fatty acid or mixture of unrefined cetylated fatty acids.