engleski

Microsystem for biocatalytic production of biodiesel

Renewable fuels are recognized as an important energy source in today’s energy market. Biodiesel, which is considered more environmentally friendly than fossil fuels, has attracted a lot of attention. Nowadays, biodiesel is produced industrially by transesterification of oils and fats of different origins. Transesterification, a reaction in which fatty acid esters are produced from oils or fats and alcohols in the presence of a catalyst, is the most widely used process for producing biodiesel. However, the downstream processes used in industrial biodiesel production present a critical challenge and determine the final price of biodiesel. One of the biggest issues in biodiesel purification is the removal of glycerol, the by- product of a transesterification process. To overcome the challenges of biodiesel production and purification, microsystems have been introduced as process intensification tools. Microsystems offer numerous applications, from microreactors to microextractors. The application of microsystems results in improved mass and heat transfer, higher reaction and extraction rates, lower costs and energy consumption, while producing much less waste. All these advantages can be used extensively in biodiesel production and purification. The research conducted in this study was divided into several steps. Firstly, reaction conditions for the lipase-catalysed biodiesel synthesis were optimized. Edible and waste sunflower oil (acquired from deep frying of potatoes) were used as a substrate while methanol was used as the source of alcohol. Different microreactor configurations were analysed (different inlet strategy, different oil to methanol molar ratio, different residence times) in terms of getting FAME yield to meet the quality standard. The highest yield of 96.5 % at a residence time of τ = 20 min was obtained in the microreactor experiment using an emulsion of waste oil and commercial enzyme suspended in a water buffer as one inlet stream for a 2-stream inlet configuration. After biodiesel was produced, purification was performed using two different technologies, extraction, and membrane filtration. Extraction was performed in microsystems using water or deep eutectic solvents (DESs). By using a ChCl:Gly1:2.5 DES, free glycerol content in extract was less than 0.01 % (w/w) for the residence time of only 13.61 s. When biodiesel was purified by membrane filtration different membranes were used. Process was performed in an ultrafiltration module, where different membranes were tested for biodiesel purification, mainly glycerol removal. Polyacrilonitrile membrane showed average ultrafiltration efficiency (during 6 cycles) of 91.48 % with average free glycerol content in permeate of 0.006 % (w/w). Process models for biodiesel production and biodiesel purification were developed. Different kinetic models were selected, based on which process models were developed. All process models were validated using independent experimental results. Finally, integrated microsystems were developed, combining biodiesel production catalysed by lipase in a microreactor with biodiesel purification by either microextraction or ultrafiltration, connected in series. The best integrated microsystem was the set-up where 2-inlet feeding strategy for biodiesel production was combined with DES based microextraction. In this integrated system, for the residence time of 20 min, a FAME yield of 94 ± 3.1 % was achieved. Since the glycerol content in the purified biodiesel was lower than 0.02 % (w/w), biodiesel meets quality standards according to the standard EN 14214:2012+A2:2019.

microsystems ; biodiesel production by lipase catalysed transesterification ; biodiesel purification by microextraction and membrane filtration ; kinetics ; mathematical modelling ; integrated microsystem for the production and purification of biodiesel

Skandinavski model