NOVELTY - Preparing acid esters through reactive distillation, comprises submitting a carboxylic acid to esterification in reaction section of a reactive distillation column with an alcohol in the presence of a solid acid catalyst to form an acid ester.    USE - The process is useful for preparing acid esters (claimed). The process is useful for the manufacture of biodiesel from waste lipid materials, various oils, fats and free fatty acids.    ADVANTAGE - The process: provides high conversion of fatty acids (at least 99%); minimizes the catalyst deactivation, hence provides more stable operating process; reduces the excess of light alcohol as compared to conventional processes; and provides acid esters with better properties as compared to the prior reactive distillation processes.    DETAILED DESCRIPTION - Preparing acid esters through reactive distillation, comprises submitting a carboxylic acid to esterification in reaction section (A) of a reactive distillation column with an alcohol in the presence of a solid acid catalyst to form an acid ester, where a first supply stream comprises the carboxylic acid, a second supply stream comprises a first alcohol and a third supply stream comprises a second alcohol, the second alcohol having a higher molecular weight than the first alcohol, are supplied to the reactive distillation column, the first supply stream is supplied to the column at a first entry level located just above or at the top of the reaction section, the second supply stream is supplied to the column at a second entry level located in or just below the reaction section and below the first entry level, and the third supply stream is supplied to the column at a third entry level located above the first entry level, and a bottom stream comprising the ester formed is obtained and a top stream comprising unreacted first alcohol, water and unreacted second alcohol is obtained.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a reactive distillation column.    Reaction section (A)    Separation section (B)    Bottom separation section (C)    Heat exchanger (H-1)    Decanting vessel. (D-1)