*3.2.4 Tubular reactor setup (type 3)*

The tubular reactor was fabricated using PFA tubes with a diameter 1.58 mm (supplied by Swagelok) coiled with the definite volume rolled into a disc form, connected with a T- joint and a static mixer (supplied by ColeParmer) and immersed into a temperature-controlled Sonicator bath. Two pumps A and B were used to pump the reaction mixture at a definite flow rate. The Sonicator bath (supplied by ComBiotech, Bengaluru) was used to control the temperature of the flow reactor with a fixed sonication frequency. The output of the reactor was connected to a collection vessel.

#### *3.2.5 RTD studies to characterize the reactor types*

The flow reactors were characterized through RTD studies using sodium hydroxide (NaOH) as tracer input to develop characteristic curves such as E, F, and C curves and other relevant parameters. For better visual detection and quantification of flow patterns of the tracer element, Rhodamine B (synthetic dye) was also used. The concentration of the tracer was around 0.1 N NaOH, prepared through dissolving 4 grams of NaOH in 1 liter of Milli-Q water.

**Figure 3.** *Schematic and actual image of the packed bed reactor.*

Two methods of injection were used, such as pulse and step inputs during the experiments. The pulse input injection was done by the construction of a T-joint and an injection port, where a 10 mL tracer was injected. For the step input, the inlet of the pump was swapped from inline water flow into the beaker containing the tracer solution at time t = 0.

A constant flow rate of 15.8 mL/min was maintained for all the trials performed. The tracer concentration at the exit was measured by a conductivity meter as a function of time and plotted all the characteristic curves. The concentration of tracer measured was in terms of milli siemens per centimeter.

#### **3.3 Estimation of reaction kinetics and relevant parameters**

#### **3.4 Reaction scheme**

The saponification reaction under basic condition is represented by the following reaction scheme. The rate equation for this reaction could be represented as (**Figure 4**) [28].

$$-\mathbf{r\_a} = -\mathbf{r\_{NaOH}} = \mathbf{k \, C\_{NaOH} \, C\_{Ethylacetate}}$$

The hydrolysis of ethyl acetate was essentially an irreversible second-order reaction, in which the sodium acetate and ethyl alcohol were formed as products. The reaction was represented as ethyl acetate proceeds with a direct attack of the nucleophile on the carbon atom of ethyl acetate [25]. In another study [16], found transition complex formation was a result of nucleophilic interaction of water molecule, where hydroxide ions generally assist the complex formation. The reaction investigation was conducted through a series of experiments in a tubular, packed, and batch reactor and analyzed. The experimental data were fitted with a second-order model at the end to compare the performance [17].
