Assessment of noncatalytic biodiesel synthesis using supercritical reaction conditions

This article reviews the relatively new field of supercritical fluid phase synthesis of biodiesel fuel. We assess the current state of the art and then suggest several directions for new or additional research that would lead to important advances in this field. Biodiesel synthesis at supercritical conditions is technologically feasible and perhaps economically competitive with conventional synthesis routes for low-cost feedstocks such as waste cooking oil. A better understanding of the reaction kinetics (both metal-catalyzed and uncatalyzed) and phase behavior (e.g., location of liquid-liquid-vapor and liquid-vapor regions and critical temperature and pressure as they change during the course of the reaction) is needed. Additionally, there is a need for more detailed analysis of the economics, energy requirements, and environmental impacts of the supercritical process relative to conventional technology.