The esterification of kemiri sunan (Aleurites trisperma sp.) oil with TiO
photocatalyst was studied. Kemiri sunan oil is non-edible oil with high content of free fatty acid (FFA), which needs esterification and followed by transesterification process to improve methyl ester yield. Esterification was conducted to reduce FFA content in the oil by reacting them with methanol to produce methyl ester. In this study, esterification is conducted in photocatalytic reactor using TiO
photocatalyst in the presence of UV light. Many parameters effected to the conversion of FFA, but in this study it was limited in reaction time, ratio methanol and ratio TiO
. The aim of this study was to obtain the optimum condition of those parameters. Experimental result showed that the optimum condition of esterification achieved at ratio of catalyst to oil 0.4% (w/w), ratio between oil and methanol 1:36, and reaction time 60 minutes. the conversion of FFA into methyl ester was 83.45% (FFA decrease from 29.79% to 4.93%). Photocatalytic esterification is prospective because it needs shorter time, do not require neutralization, also in the end the catalyst and methanol could be recycled. Esterification product was characterized with FTIR.