engleski

Optimization of heterogeneously catalyzed methanolysis in microreactor using a green eggshell catalyst

Calcium oxide was derived from chicken eggshell (ES) by calcination at 900 °C. To improve catalyst performance, the catalyst was treated by the hydration-dehydration method. The new catalyst, with improved structural and morphological properties, denoted as ESHC-600, was obtained and used in methanolysis reaction. Methanolysis reaction was carried out in a microreactor system equipped with two microfluidic syringe pumps. ESHC-600 catalyst was suspended in sunflower oil and added in the first syringe, whereas methanol was placed in the second one. Microchannel with an internal diameter of 0.6 mm was connected with syringes by a T-shaped three-way junction and immersed in the thermostated water bath (60 °C). The reaction parameters are optimized in the following range: catalyst concentration (0.05, 0.075, and 0.1 g/g), methanol to oil volume ratio (1:2, 2:1, and 3:1) and residence time (4, 7, and 10 min). Design of the experiment was created according to three-level full functional design. The response variable was FAME content, which was determined by the HPLC method. It can be noted, that the catalyst exhibits satisfactory catalytic activity in such specific reactor systems in which two immiscible liquids and a solid catalyst interact at a micro-level. Namely, each segment represents one microreactor, thus achieving enhanced miscibility with suppressing external diffusion limitations. Determined optimal reaction conditions were: catalyst concentration of 10 wt%, methanol to oil volume ratio of 3:1, and residence time of 10 min. FAME content in microreactor (54.8 % FAME) was 5 times higher compared with the reaction in a batch reactor (10.3 % FAME) under optimal conditions. Also, it is important to note that potential problem in such microreactor systems represents catalyst precipitation in the syringe, which is particularly pronounced at longer residence time. Such behavior of the catalyst leads to a decline of catalytic activity due to non-uniformly catalyst concentration during the reaction, which can be overcome by pre- treatment of the catalyst-oil suspension under ultrasonic conditions. According to obtained results, such designed reaction systems can be used in biodiesel production in a large scale using sustainable, green, and energy-efficient processes, whereby productivity would be increased by connecting more of these reactors in series.

biodiesel ; eggshell ; microreactors ; heterogenous catalysis

nije evidentirano