Non-catalytic production of biodiesel using supercritical methanol: a brief review

This paper aims to review the potential and challenges of non-catalytic transesterification as a sustainable route for biodiesel synthesis. Recently, biodiesel production using supercritical technology has undergone rapid developments as it provides numerous advantages over conventional catalytic technologies, including elimination of catalyst preparation and product separation and purification processes, higher biodiesel yield, shorter reaction time, applicability to a wide variety of feedstocks without any pre-treatment requirements. Nevertheless, there are many concerns regarding the massive energy obligation to conduct the reaction at the supercritical conditions of methanol, which requires high temperature and pressure. Accordingly, the challenges facing the supercritical technology to be considered as a sustainable process have been elaborated through this review. Different production techniques using supercritical technology have been addressed. Several reaction variables affecting the supercritical reaction and their optimisation methodologies have been discussed in this review. Moreover, some constructive recommendations have been proposed thoroughly to overcome the limitations of this technology. Biodiesel production using supercritical technology could be considered as a sustainable route in the near future.