A novel process is described for producing esters of linear monocarboxylic acids containing 6 to 26 carbon atoms, by reacting vegetable or animal oils, neutral or otherwise, with monoalcohols containing 1 to 18 carbon atoms in the presence of a catalyst selected from: mixtures of titanium oxide and alumina having formula: (TiO.sub.x).sub.y(Al.sub.2O.sub.3).sub.1-y where x has the value 1.5 to 2.2 and y, representing the weight ratio of the two oxides, has a value of 0.005 to 0.995; mixtures of zirconium oxide and alumina having formula: (ZrO.sub.x).sub.y(Al.sub.2O.sub.3).sub.1-y where x has the value 1.5 to 2.2 and y has a value of 0.005 to 0.995; and mixtures of antimony oxide and alumina having formula: (SbO.sub.x).sub.y(Al.sub.2O.sub.3).sub.1-y where x has the value 1.2 to 2.6 and y has a value of 0.005 to 0.995, in order to directly produce, in one or more steps, an ester for use as a fuel and a pure glycerin.