engleski

Integrated microsystem for biodiesel production

Biodiesel has been identified as one of the most prominent options for partially reducing the use of conventional fossil fuels, one of the most significant causes of climate change. Biodiesel, a mixture of monoalkyl esters of long-chain fatty acids, provides valuable improvement in comparison with petroleum diesel in terms of biodegradability and renewability, better quality of exhaust gas emission and lower environment harmful effect [1]. Conventional biodiesel production processes cannot fulfil the supply for biodiesel, so new intensified processes are rapidly developing. Application of microreactors is a way to intensify conventional processes in terms of mixing, mass transfer and reducing the reaction time. Microreactors have been thoroughly explored in recent decades [2]. However, enzyme-catalysed process continues to represent area which need to be additionally investigated. Production of biodiesel is only a first step towards gaining a product which meets the quality standards according to EN 14214 [3]. After the transesterification, the separation of biodiesel and by-products, primarily glycerol, is usually carried out by a phase separation process based on the difference in density. Common purification methods include biodiesel washing by water (also known as wet washing). However, rinsing with water generates large quantities of wastewater that must be properly disposed, posing a great economic and environmental problem. Therefore, alternative solutions for the purification of biodiesel have been developed, of which the use of deep eutectic solvents (DESs) is of particular interest. It has been shown that DESs prepared from choline chloride and ethylene glycol or glycerol as hydrogen bond donor can efficiently and completely remove free glycerol from biodiesel [4, 5]. In the previously conducted experiment, integrated system was developed for the production of biodiesel and its purification (Figure 1). The experiment was carried out in a polytetrafluoroethylene (PTFE, teflon) tubular capillary microreactor (length: width = 500 mm:1 mm, internal volume 392.5 μl). The first microchip (microreactor) was used for biodiesel production while the second one (microextractor) was used for simultaneous glycerol separation, i.e. biodiesel purification. The maximum FAME yield (94.52% ± 3.38) was obtained for the residence time of less than 1 h [6]. As a next intensification step, two new integrated systems were proposed on a smaller channel size (length: width: depth = 330 mm: 500 μm: 50 μm with internal volume of 8, 3 μL). First, an integrated system on two microchips connected in series (Y-shape inlets, with DESs recirculation in the system) and second, an integrated system on a single chip. In a system with two integrated chips (Figure 2), continuous synthesis of biodiesel from sunflower oil and methanol with the lipase from Thermomyces lanuginosus as catalyst will take place on the first chip. The crude biodiesel thus obtained will be routed to another chip, where continuous extraction of all impurities will be carried out using deep eutectic solvents (DESs). At the exit of the second chip, the solvent and pure biodiesel phase will be separated and the solvent will be returned to the process by a recirculation pump. When developing a single chip integrated system, the synthesis and purification of biodiesel will take place on a single chip without solvent recirculation.

microreactors, biodiesel synthesis, biodiesel purification, integrated system

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