Automation System - Automation in Microreactor Systems - Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)

Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)

4. Automation in Microreactor Systems

4.2. Automation System

For the past several years, our lab has explored automated reactions with the general microfluidic system and silicon microreactor shown schematically in Figure 4.1 [33, 34]. The reactor itself is mounted on a two-zone temperature control block. The left zone is controlled at an elevated temperature, while the right zone is cooled. The oval section between the two zones allows for insulation between the two temperature areas. The cooled mounting block is designed with threaded channels to allow for fluidic connections between the reactor and external pumps and analytical equipment. In addition, this block has separate channels for cooling fluid from an attached chiller to maintain temperature. Similarly, the heated mounting block contains a resistive heating element to control the temperature of the reaction zone. Owing to the high thermal conductivity of silicon, fluid rapidly reaches thermal equilibrium when moving between temperature zones, enabling the reactant streams to mix fully before entering the heated zone and tight control on time spent in this reaction zone. Additionally, the low thermal mass of the reactor and temperature-control blocks allows for rapid changes between temperature set points.

Figure 4.1 Automation system schematic. Solid lines represent fluid flow, and dashed lines represent data flow.


The temperatures of these zones are measured by integrated thermocouples and maintained by PID controllers. The residence time is controlled by one or more syringe pumps. Concentration may also be controlled by adjusting the flow rate of reactants and solvent on separate pumps. These controllers and pumps are connected via RS-232 to a computer running Labview to control their set points. This computer is also connected to the in-line analytical equipment, to allow for reaction feedback. A Matlab script within Labview monitors the reaction condition and determines how and when set points should be changed. By varying the analysis and structure of the script used, a number of experiments can be run with differing control schemes and goals.