(143e) Sustainable Biodiesel Production From Waste Cooking Oil and Animal Fats Under Supercritical Methanol

Chee Kai Tan¹, Maoqi Feng¹, Laura Harris², and Cary Wang¹

1)      Chemical Engineering Department, Chemistry and Chemical Engineering Division, Southwest Research Institute, San Antonio, Texas

2)      Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia

Abstract

In conventional process for transesterification of animal fats and vegetable oils to biodiesel, free fatty acids and water always present a problem and result in a low conversion.  These problems can be easily overcome in supercritical methanol (SCM) process.  In our study, both glyceride tributyrate, animal fats, and waste cooking oil were used as feedstock for transesterification under supercritical methanol condition.  The process flow diagram is shown in Figure 1. The reactor was constructed from a 3/8” OD x 4’ long stainless tube with wall thickness of 0.049” (reactor volume = 47.4 mL). For glyceride tributyrate, the conversion was 100% under SCM condition. For waste cooking oil, the fatty acid methyl ester (FAME) yield was  >90% at the following reaction conditions: reaction temperature = 300^oC and 250°C, reaction pressures = 2000 psi, 2500 psi, and 3000 psi, residence time = 18 minutes, and molar ratio of methanol to oil = 40:1, flow rate = 2.5 mL/min.  Heterogeneous catalyst, ZSM-5, has lowered the transestrification reaction to sub-supercritical conditions, thus the process is more cost attractive for biodiesel manufacturing. Both temperature effect and pressure effect will be presented.  

Figure 1.  Continuous Process Flow Diagram for biodiesel production with supercritical methanol.