Page 43 - חוברת תזות הנדסה ירוקה 2023

Study of micro-droplet effect on chemical reactions
Reut Amar1 npreut@walla.com
Prof. Dorith Tavor1, Dr. Izhak Ladizhensky1
1Sami Shamoon College of Engineering
Droplets and micro-droplets have recently become more common in various industries. The advantage of using drops rather than liquid in its liquid form is the increased surface area, giving a higher surface-to-volume ratio, which increases the efficiency of various processes. Turning liquid into droplets or small particles is called ‘atomization’ and is usually done with an atomizer. Theoretically, when chemical reactions occur in droplets, the surface areas of the droplets enable better interaction between the molecules of the reactants; therefore, droplet diameter may have a significant effect.
The purpose of the present study is to examine the use of the microdroplet method for increasing the efficiency of chemical reactions and for finding optimal conditions for performing various reactions.
The production of droplets is achieved by the creation of bubbling in pressurized air that is passed through a perforated tube into reactant solutions; this method creates fine droplets. Two model reactions were tested—hydrolysis of amyl acetate by potassium hydroxide to form amyl alcohol and a reaction between potassium hydroxide and benzyl chloride to form benzyl alcohol, which is slower.
Initially, the experiments were attempted on a system that was found to be unstable. In this first system, the hydrolysis reaction was tested under pressures of 2, 3, and 4 bar, as expected, as the pressure increased, the reaction conversion increased. The increase in pressure caused the kinetic energy of the liquid to increase, better overcoming surface tension. Thus, the liquid easily disbands into drops and there is better interaction between the reactants. Another parameter tested was the diameter of the tube nozzles from which the air exits into the solution. The tested diameters were: 0.5, 0.7, and 0.23 mm. With a tube nozzle diameter of 0.23 mm, the obtained results lacked good precise; probably, this diameter is too small. Here, the smaller the diameters of the drops, the higher the conversions. )For the smallest droplet diameter of 0.87μm, the highest conversion rate was obtained, 90% at the high pressure of 4 bar(. An attempt was made to perform a slow reaction in the initial system, but very few or no conversions were obtained.
Since the first system was somewhat unstable, it was decided to make changes, and a second system was built. In the second system, it was impossible to produce reactions at a pressure of 4 bar; therefore, the pressures tested were 2, 2.5, and 3 bar. Comparing the experimental results of the two systems, it was found that smaller droplet diameters were obtained in the improved second system, causing better interactions between the reactants,
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