Unlocking the Power of Flow Chemistry

During flow chemistry processes, material continuously enters and leaves the 'flow reactor'. Conditions, such as reactant concentrations, pH, pressure, temperature, and mass transfer between different phases, allow a chemical reaction to develop.

In batch chemistry, the reactor conditions change over time (the concentrations at the start of the reaction will show variability compared to those at the end). Conversely, in the flow chemistry process, the reactor conditions remain constant once the steady state has been realized. A simple description of a flow reactor would be a round-bottomed flask with a constant supply and flow of reactants inwards while a product constantly flows outwards.

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The design of the flow reactor can have a major impact on the reaction; the most basic flow reactor is a simple tube into which reactants flow. Here, mixing material will, by and large, be slow diffusion. By introducing internal structures within the tube (static mixers), improvements in the mixing can be observed, but it can cause pressure drops. Tubular reactors are sometimes referred to as plug flow reactors (PFRs) which can confuse as the flow is not considered plug flow.

A good substitute for a tubular reactor would be a continuous stirred tank reactor (CSTR). This vessel is fitted with an agitator into which fluid enters and leaves. CSTRs are a cornerstone of chemical product batch manufacturing due to their versatility in handling a diverse range of materials—they span single—and multi-phase chemistry, crystallizations, viscous materials, fermentation requiring gas sparging, and more.

CSTRs are available in many different sizes, and process engineers are granted access to considerable amounts of data and a broad spectrum of correlations with which to specify equipment (e.g., mixer type) and operating parameters for distinct functions (e.g., suspension of particles, mixing of phases). CTSRs also help support and develop knowledge regarding the scaling of the process (e.g., from small development scale to manufacture scale).

The fReactor-Classic has been developed by leveraging many of the key principles of CSTRs. Each distinct module is a single CSTR. There are valid reasons for using more than one CSTR together—each additional module helps make the processing conditions across various fluid 'elements' more uniform.

Other reactor designs can facilitate distinct needs, such as exothermic reactions, specific multiphasic reactions, fast reactions, or the use of catalyst beds. Some of these can be found on Asynt’s pages covering multiphasic flows, but these pages largely focus on PFRs and CSTRs to support a better understanding of flow reactors and introduce researchers in various application contexts to the wider world of flow reactors.

This information has been sourced, reviewed and adapted from materials provided by Asynt.

For more information on this source, please visit Asynt.