Separation and Purification of Biodiesel by a Millifluidic System

In this research, we applied the characteristic of high surface area to volume ratio in microfluidics, conducting separation and purification procedures in biodiesel production, and attempt to integrate transesterification onto one chip to realize a high-throughput completed biodiesel production chip. Fatty acid methyl ester (FAME) is not available immediately after transesterification as a result of containing excessive methanol. Methanol can be washed out from FAME by water-washing process, which is needed to be carried out to reduce the methanol content. In this research, we designed washing chip to decrease methanol content in biodiesel and separation chip to collect high purity biodiesel from upper outlet by gravity settling. Methanol content was reduced from 6% before washing to less than 0.2% after washing by injecting biodiesel and water into 500 mm washing chip at 0.6 ml/min water flow rate, meeting FAME standard. Washing chips with staggered-herringbone structure can obtain even better results. We use passive structure of flow channels to separate the biodiesel and its by-product. Due to the effect of gravity, flow pattern in the channel changed from slug flow to somewhat like laminar flow gradually. Therefore, fluids from upper outlet of the chip are pure FAME, confirmed by no glycerol peaks in the NMR chart of upper-outlet fluids. Hydrolysis of intermediates in transesterification caused reverse reaction during washing procedures, decaying conversion largely. In this research, we tried two different methods to reduce intermediates: longer residence time and higher environment temperature. Decent conversion of 93 % can be attainable at 55 ℃ and 1 h residence time. We proved heating and settlements are essential factor to connect transesterification with separation and purification in continuous biodiesel production.