What is Continuous Flow Chemistry?


Continuous flow chemistry is widely used in the chemical and petrochemical markets, and has been for decades.  The continuous flow chemistry production methodology has been gaining interest in pharmaceutical R&D due to:

  • Improved Process Safety
  • Improved Quality
  • Space Savings
  • Increased Product Capacity

In its simplest form, continuous flow chemistry begins with two or more streams of different materials – for example starting material and reactants.  The streams of materials are pumped at pre-determined flow rates into a single chamber, tube, and in some cases a micro reactor which contains small channels where the flowing material mixes and reacts with one another.  At this point, the materials mix together and react as they flow through the reaction chamber.  Due to the very small size of the reaction tube or channels of the micro reactor, only small amounts of materials are needed for the reaction which:

  • Reduces use of expensive reagents/compounds
  • Lowers solvent use
  • Improves temperature control
  • Improves workplace safety because of the lower amount of material for potential exposure

Based on the reaction kinetics and flow rates of the material, a specific residence time within the micro reactor  is needed to ensure that all starting material is converted to the desired product.  In turn, the material is then collected at the outlet of the micro reactor in a flask or other suitable container.

Since the reaction is in a continuous flowing stream, it is desirable to monitor the state of the reaction to know conditions including:

  • Steady state
  • Dispersion characteristics
  • Presence of reactive intermediates

Monitoring the reaction requires technology that lends itself to identification of each reaction component all while in a flowing stream.  ReactIR fitted with a micro flow cell is an appropriate technology.  ReactIR is based on FTIR spectroscopy and when coupled with Attenuated Total Reflectance (ATR), is ideal for in situ measurement and trending of reaction components.

FTIR (fourier transform infrared) spectroscopy is specific in that each functional group of a given material has a unique fingerprint spectrum.  This allows easy differentiation and determination of reaction components.  When measuring the intensity of the respective IR signal over time, you are able to trend the relative or absolute concentrations over the course of the reaction.  In other words, you can watch the trends changing and when a plateau is reached, you can ensure the reaction is at steady state.

If you are interested in learning more about the benefits of flow chemistry, I invite you to view the online presentation given by Professor Steven Ley of the University of Cambridge, UK: The Application of the ReactIR Flow Cell to Continuous Processing Technology or read an earlier post regarding the specific benefits of continuous flow chemistry.

Author’s note: Continuous flow chemistry has also been called flow based chemistry, microflow chemistry and plug flow chemistry.