| The synthesis conditions of coconut oil fatty acid ester, such as water-entrainer type and dosage, molar ratio of acid to alcohol, catalyst dosage and reaction time, were optimized by the esterification of coconut oil fatty acid with 1, 6-hexanediol as a probe reaction catalyzed by novel supported solid acid Zr(SO4)2-Ti(SO4)2/SiO2. Another five alcohols with different molecular structures were used as the reactants to synthesize five coconut oil fatty acid esters, respectively. The six synthesized esters were characterized by FTIR. The optimal synthesis conditions were obtained as follows: water-entrainer (toluene) dosage 8 mL (in respect to 0.02 mol 1, 6-hexanediol), molar ratio of coconut oil fatty acid to 1,6-hexanediol 2.5∶?1, dosage of catalyst 6% (in respect to the total mass of the reactants) and reaction time 4.5 h. Under the optimal conditions, the esterification rate could reach 98.6%. The catalytic activity of the above solid acid for the synthesis of coconut oil fatty acid ester of monohydroxy alcohol was higher (esterification rate 99.1%), while it was relatively lower (esterification rate 80.3%) for tetrahydroxy alcohol. The catalytic activity decreased with the increase of hydroxyl group in the alcohol molecule. In the case of the same number of hydroxyl group, both the decreases in the branched alkyl chain of alcohol molecule and in the carbon atom of the branched alkyl chain were beneficial to improve the catalytic activity of solid acid. |
