Microreactor systems: Using Teledyne Isco Syringe Pumps

Teledyne Isco pumps have a range of uses in different industries.  One use was by the Environmental Protection Agency’s National Risk Management Research laboratory in Cinncinnati, Ohio who focuses on development of process intensified and green reaction strategies for pharmaceutical relevant reactions.  These high precision syringe pumps have been invaluable to this work in demonstrating organic chemistries in the Spinning Tube-In-Tube (STT®) reactor.  The reactions used with this type of system include the high-conversion synthesis of esters from acid anhydrides and alcohols, of imidazole-based ionic liquids and of dipyrromethanes.

The reaction system is comprised of two Teledyne Isco Model 100DX syringe pumps with the STT®Magellan™microreactor (see Fig 1).  The key feature of this microchemical reactor system is the high ratio of surface area to volume.  As a result, mass transfer, heat transfer, and mixing are vastly more efficient.  Other benefits of this type of system include:

• Increased throughput
• Minimized unwanted by-product formation
• Safer chemicals
• Solventless or decreased solvent usage
• Minimal environmental footprint
• Smaller physical footprint

As shown in figure 1 each pump is connected separately to the reactor with a manual valave on each inlet and outlet.  Based upon the chemistries employed, the required residence times in the reactor vary from 10 seconds to 5 minutes.  This requires the syringe pumps to operate at flow rates from 0.100ml/minute.  In order for the reactions to yield the desired conversion and selectivities while minimizing unwanted reaction by-products, the concentrations of the reactants must be precise and kept constant.

Why Teledyne Isco Pumps?

Teledyne Isco pumps have a flow rate accuracy of ± 0.5% or better, and flows are pulse-less.  Pulse-less flow means fluid pressure and density are constant, without fluctuation in solvating properties or chemical potential.  The pumps can be operated in either constant flow or constant pressure mode, as a stand-alone unit, or via external control.  Teledyne Isco syringe pumps also have a flow rate and pressure limits alarm to alert the user to any change in conditions.

In addition Teledyne Isco Syringe pumps have much larger cylinder volumes (up to 1 L), eliminating the need for refills with most batch runs.  For continuous operation, however, dual pump systems deliver pulse-less flow with the same accuracy and precision of single pumps, and can operate unattended.

STT Reactor Setup with two Isco pumps operating independently and simultaneously from one controller, in constant flow mode

Other pump types, such reciprocating pumps, produce flow or pressure pulse that affects the quality of the product produced.  For reciprocating pumps, the piston sweep volumes are typically small, and thereby require frequent refills, creating periodic pressure drops.  Although dual piston reciprocating pumps produce smoother flows than single piston pumps, they cannot produce the pulse-less, accurate flows required for many high performance applications.

Typically, chemical engineers choose to work with Model 100DM for low flow applications, 500D for most common applications, or the 500HL pump for Hazardous Location environments.  Single pumps are most often used in batch applications, while dual pumps are used in continuous flow.

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