Using back pressure valve in flow chemistry

Continuous flow chemistry or flow chemistry is compared to batch chemistry. The advantages include more consistent quality, higher efficiency, and easy scale-up from R&D to production. In flow chemistry, two or more reagents are mixed through the reactor in a continuous manner, and the flow, temperature, and pressure are controlled to perform the required chemical reaction most efficiently.

Controlling pressure in flow chemistry is important for phase control, residence time, reaction rate, and equilibrium management. For example, the reaction temperature is a key component of the reaction efficiency, but at a sufficiently high temperature, the reagent will reach the boiling point, which will have a negative effect on the reaction. By adding a back pressure regulator at the reactor outlet to control the reaction pressure, the reagents can be prevented from boiling.

Sometimes one of the reagents is a gas or sometimes an inert gas is introduced. By increasing the reactor pressure, the actual volume that the gas will occupy is reduced. This will leave more space for the liquid portion of the reaction, thereby increasing the productivity of the reactor.

In addition, in a gas-liquid reaction, pressure has an effect on the reaction speed. Generally, the gas must first be dissolved in the liquid before it can react. By increasing the pressure, the solubility of the gas increases, thereby increasing the reaction rate.

When the chemical reaction is reversible, there will be an equilibrium between the reagent and the product, and when the equilibrium is reached, the reaction speed will be slowed down. When the gas participates in this reaction, the balance will depend on the pressure. At higher pressures, the equilibrium will shift to the side of the reaction equation with the fewest gas molecules.

The back pressure valve is used to provide back pressure to the outlet of the microreactor, and is suitable for reactions that require pressurization, especially gas-liquid reactions. For gas-liquid reactions, normally, the gas will quickly occupy most of the space inside the reactor after entering the reactor. In addition to the large flow rate of the gas, the phenomenon of rapid outflow of the gas or the expulsion of the liquid will often cause the liquid to be segmented. Greatly affect the response effect. The back pressure valve installed at the outlet of the reactor can ensure that the reaction system is carried out under a certain pressure. After the gas is compressed, the volume becomes smaller, the flow rate slows down, and it can be fully contacted and mixed with the liquid, which improves the reaction efficiency.

Continuous flow chemistry is used in a variety of industries, including petrochemicals, specialty chemicals, active pharmaceutical ingredients (API), and polymer chemistry.