Status and prospects of supercritical alcohol transesterification for biodiesel production

摘要

The growth in the global fuel consumption is expected to continue unabated. At the same time, nationsrnaround the globe are trying to reduce greenhouse gas emissions resulting from the transportation sector.rnThese factors have led researchers to look for alternative sources of fuels. Biodiesel is one suchrnalternative fuel that can complement or displace petroleum diesel with a potentially lower carbon footprintrnfuel, depending upon the feedstock and the production process. Biodiesel refers to the monoalkyl estersrnderived from a wide range of raw materials, like vegetable oils, animal fats, and algae lipids.rnConventionally, biodiesel is produced by transesterification with the help of an acid, base or enzymerncatalyst. Certain drawbacks, like slow reaction times, soap formation and intense pre- and post-processing,rnare associated with conventional transesterification, ultimately leading to increased capital and productionrncosts. Supercritical transesterification is a relatively new technique promising to provide advantages, suchrnas faster reaction times, catalyst-free operation, and higher purity of final product, over the conventional transesterification method. The most common feedstocks are virgin and used edible oils from crops likernsoybean, rapeseed, and African palm. There is an increasing interest in algae to avoid the utilization ofrnfood resources for energy production. Using algae as a lipid source, a more sustainable biodieselrnproduction process could be developed to achieve large-scale production capabilities on a long-term basisrnwithout adverse effects on the food chain. This paper presents a critical review of supercriticalrntransesterification and its prospects for biodiesel production.