Synthesis of Biodiesel from Second-Used Cooking Oil

These days, many used cooking oils from restaurants were re-used by street sellers to fry their food. Those waste oils commonly just throw away. Whereas waste oils which have not any treatment first, will pollute the environment. One of the ways to treat the waste oil is by converting to biodiesel. This research aimed to study the kinetic reaction of second-used cooking oil transesterification into biodiesel and find the optimum condition of its process. This research was done by transesterification reaction in batch reactor. The feedstock was collected from the street sellers in Yogyakarta. Methanol was used as a reactant and KOH was used as a base catalyst. The study parameters were temperature, alcohol to oil molar ratio, and catalyst concentration. Several types of analysis used were free glycerol analysis, total glycerol analysis, free fatty acid (FFA) analysis, and saponification analysis. These analyses were used to calculate the yield of conversion and ester content of biodiesel sample. From this research, it is found that the kinetic reaction of second-used cooking oil transesterification can be expressed by k = 0.0251exp (-15.29/RT) dm3/(mol.min). The optimum condition (the ester content 92.76%) of biodiesel production were obtained at temperature 66.5oC, molar ratio of methanol to oil 6.18:1, and 1 wt.% KOH.