Effect of Water Content in Waste Cooking Oil on Biodiesel Production via Ester-transesterification in a Single Reactive Distillation

Abstract

A single-column reactive distillation is employed to convert waste cooking oil to biodiesel via simultaneous esterification and transesterification reactions. The waste cooking oil contained 10 wt% of free fatty acid (FFA) and the contaminated water (2-8 wt%) was used as feedstocks for biodiesel production. Esterification was occurred in the upper of column to reduce FFA content to less than 1 wt% and to prevent the simultaneous saponification by base catalyst. Moreover, the contaminated water and by-product water (from esterification) together was removed in-situ as the distillate product. The reactive distillation has been optimally designed to have 16 stages consisting of 5 esterification, 9 transesterification stages and each stage for reboiler and condenser. The feed locations of oil and methanol were at the top of the column and at stage 6, respectively. The optimum methanol to oil ratio was 6:1 with reflux ratio 0.1 while the reboiler duty was in the range of 100-150 kW depended on the water content. This condition successfully converts 97 wt% of waste cooking oil to biodiesel with 96.5% purity.