Lipase-catalyzed transesterification (also esterification) from oils or fats for biodiesel production has some advantages over chemical-catalyzed transesterification, such as environmental friendship, lower energy consumption，being widely suitable to low quality oils or fats. However, the low stability of the lipase due to alcohol (methanol) has been being regarded as the main hurdle to the industrialization of lipase-catalyzed biodiesel production. Tsinghua University has developed a novel process to eliminate the inhibition of methanol on lipase, thus the operational life of the lipase could be improved into more than 300 cycles from several (1-5) cycles while traditional process applied. The patented novel process was successfully demonstrated in a pilot plant (200kg/day) and commercial plant (50,000ton/year) in China. It has also been being demonstrated in a pilot-plan in Brazil.
During the past 20 years, it has been being an attractive project to research and improve the enzymatic process for biodiesel production. Of course, the enzyme (lipase) itself is one of the core factors. A lot of research focused on how to improve the specific activity or stability of lipase. Its stability depends upon not only enzyme itself but also how to use it. Some researchers use the free lipase (which is cheaper) as catalyst, but do not recycle lipase, other researcheres use and recycle immobilized lipase which is much expensive. This work presents a novel process in which both free and immobilized lipase are applied and successfully recycled. The free lipase will first catalyze more than 90% of the conversion of oils and the obtained products contain still free fatty acid (FFA) which is not accepted by the standard specification of biodiesel. Then the immobilized lipase will further catalyze the conversion of the unconverted feedstock form the first step.
Compared to the process using only free lipase (normally a neutralization with alkaline needed to remove FFA), the novel process can directly get the qualified products and higher yield because of the conversion of FFA. Compared to the process using only immobilized lipase, the dosage of immobilized lipase can be significantly reduced with the novel process because that less than 10% of the conversion is left for the immobilized enzyme after the first conversion with free lipase.
See more of this Group/Topical: Transport and Energy Processes