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The Sigma-Aldrich Microreactor Explorer Kit — Made by Chemists for Chemists

By: Matthias Junkers, ChemFiles Volume 9 Article 4

All-in-One Solution

The Sigma-Aldrich Microreactor Explorer Kit was designed to give newcomers an opportunity to start discovering this innovative technology right away. Designed by chemists for chemists, it contains everything that is needed to perform flow chemistry experiments in a microstructured system right away: robust pumps for the transport of the reagent streams, a microreactor, an electronic monitoring unit including sensors for automated temperature and pressure supervision, sufficient tubing and fittings to connect all the different modules of the system, and last but not least spare replacements for consumptive parts. With its easy step-by-step manual, even non-experienced technicians or chemists will be able to set up and instantly use the system without effort. The Microreactor Explorer Kit 19979 gives chemists the opportunity to concentrate on what they can do best: chemistry!

In environments where microreactor and flow chemistry systems are already established, the Sigma-Aldrich Microreactor Explorer Kit can still be a valuable addition to the toolbox. With its highly attractive price, its portability and ease of use it can be applied to perform the initial process development for much more expensive and complicated systems. To this end it will help to employ all available flow chemistry tools as efficiently and cost-effectively as possible.

The Sigma-Aldrich Microreactor Explorer Kit 19979 is the most economical integrated solution for flow chemistry in microstructured reactors on the market. Why pay more?

Robust, Multipurpose Microreactor Chip

The borosilicate glass microreactor chip manufactured by Little Things Factory in Germany following Sigma-Aldrich’s design, offers the highest possible resistance to aggressive reagents (Figure 13). Even corrosive reactants like concentrated acids or acid halides can be used without harm. Glass offers the obvious advantage, where processes taking place in the microreactor are clearly visible. Blockages and impurities are easily detected and their removal can be followed visually. The Sigma-Aldrich glass microreactor with a total inner volume of 0.85 mL features two independent reagent stream inlets (indicated by the green and light yellow peek nuts on Figure 13, the red nut marks the output stream) with a small pre-heating unit of 0.08 mL each, a micromixer unit of 0.03 mL, and a fixed residence time unit (RTU) of 0.66 mL. Channel diameters are about 500 μm all through the reactor. This makes the reactor quite robust against blocking, because the channels will allow solid particles with diameters up to about 10% of the channel dimensions to flow freely through the system as long as the material does not accumulate at the channel walls. At the same time, channel dimensions are small enough to benefit from all advantages of microreactor technology (see previous chapter). A seperate channel allows insertion of the temperature sensor supplied with the kit directly into the glass chip. The temperature can be measured freely at any location between the beginning of the mixing zone to the end of the residence time unit.

Figure 13: Borosilicate glass microreactor from Kit 19979


Easy Heating or Cooling

Heating and cooling of the glass microreactor is very straightforward. A chemist will simply do what he is used to doing with any conventional glass flask: immerse it in a heated or cooled bath. This method is simple, but highly efficient; and all common heating or cooling media can be used. The microreactor is usually submerged just below the fittings. If more precise temperature control is required then the reactor can be completely sumberged in a temperature regulated system.. However after large temperature changes the fittings should be retightened.

Variable Residence Time Unit

The residence time unit (RTU) on the glass microreactor is fixed to 0.66 mL. Reactions requiring a longer residence time variable, extension is possible with 25 mL of extra PTFE tubing supplied with the kit. The residence time τ is the flow chemistry equivalent of the reaction time in classical batch chemistry. It is defined by the combined volume of the microreactor and the residence time unit and the flow rate. The PTFE tubing can be cut down exactly to the length needed for a specific reaction. Smaller pieces can be combined again into longer residence time units with connectors. To control the reaction temperature the tubing can be coiled and submerged in a heated or cooled bath.

Figure 14: Set-up example with heated bath (not included in kit)


Robust and Versatile Pumps

The Ismatec rotary piston pumps supplied with the Microreactor Explorer Kit 19979 are the best choice for continuous flow chemistry at an affordable price (Figure 15). They guarantee an undisturbed flow for hours, even at higher pressures. The ceramic pump heads align perfectly with the borosilicate glass reactor, which permits the prolonged use of aggressive and corrosive reagents. Flow rates can be chosen freely from 0.2 to 90 mL/min with adjustable stroke volumes. It should be noted though that backpressure in the system will limit the highest achievable flow rate depending on the viscosity of the solvent and the temperature. The system is specified to work up to 15 mL/ min at its full temperature range from -70 to 150 °C with all common solvents. The Microreactor Explorer Kit 19979 requires only minimum maintenance or replacement of wearing parts that can be performed by any chemist or lab worker.

Figure 15: Rotary piston pump head


Automated Pressure and Temperature Supervision

The Sigma-Aldrich Microreactor Explorer Kit 19979 is supplied with an easy to use monitoring unit based on a Siemens SPS element that is able to supervise two temperature and two pressure channels (Figure 16). Here the user can define upper and lower limits for each channel. If one of the sensor channels reports a violation of the threshold values the control unit will shut down the whole system. This allows unsupervised operation of the microreactor system. If for example a blockage of the microreactor occurs, then the pressure in the system will rise and the system is halted automatically in a safe state. This means that expensive parts like the pumps or the microreactor are protected from any serious damage and the risk of leakages of potentially harmful chemicals is also minimized. The user can remove the cause of possible problems upon return and restart the system. The electronic control unit is small (shoebox size) and robust and can be put into the fume hood together with the whole kit.

Figure 16: Pressure sensors


Convenient Case

The transportation case allows convenient movement of the Microreactor Explorer Kit 19979 (15 kg) between laboratories and facilities. The whole system can be set up in less than an hour and if space is required in the laboratory for other tasks, the whole system can be stored away in its case.

Included Accessories

The kit includes many useful accessories that will accelerate an instant start: a metal rod and holder help to lock the microreactor chip in the desired position; additional fittings and connectors; a tube cutter to facilitate working with the PTFE tubing, and three bottle caps to keep the reagent inlets and the product stream in place.

Open Construction

All parts of kit 19979 are connected with standard fittings that are also used in chromatography equipment. This enables the easy incorporation of additional modules into the microreactor system. For example, a pressure valve can be attached to the output stream of the reactor in order to increase the boiling point of the solvent or to avoid phase separations in reactions with gas formation. The open construction of MRE Kit 19979 also makes it ideal for use in teaching. The function of all individual parts can be observed as opposed to the mystery of a black box.

Requirements

The Microreactor Explorer Kit 19979 was developed as a highly versatile tool for chemical synthesis and all kinds of chemical transformations can be performed in this system with only a few requirements needing to be met. All starting materials and products have to be in solution or liquid form to avoid blocking the microreactor. Still, blockages do not need to be feared as the reactor can usually be liberated easily.

The formation of gases and volatile vapors during the reaction may diminish residence times unpredictably and should also be avoided. Flow pressure within the system via a pressure valve can help to suppress the formation of gas bubbles.

Finally, it should be noted that the faster a reaction runs the greater it benefits from microstructured reactors (preferrably less than 30 minutes). Slow reactions that take several hours or days to complete are not enhanced significantly by the special features of a microreactor.

Comprehensive Manual

The Microreactor Explorer Kit 19979 is supplied with a comprehensive manual that will guide users easily through the system set-up. Many tips for the design of experiments are given (including e.g. an Excel® sheet on CD for the planning of a microreaction and the calculation of output, concentrations, etc.). The Microreactor Explorer Kit 19979 is so easy to set up and use that special, time-consuming training is not required to work with the kit.

Optional Accessories

Some recommendations for optional accessories are given with the manual, e.g. valves required to perform reactions at elevated pressure in order to raise the boiling point of solvents.

Optional Accessories

Some recommendations for optional accessories are given with the manual, e.g. valves required to perform reactions at elevated pressure in order to raise the boiling point of solvents.

Multistep Synthesis

The Microreactor Explorer Kit 19979 can be used to perform continuous flow multistep reactions. Two kits with an additional 3rd glass microreactor contain all parts needed for a 3-stage assembly with full temperature and pressure supervision. Examples of multistep microreactions are presented in detail in the following chapter.

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MRE Kit 19979 at a Glance


MRE Kit 19979 Components
  • 0.85 mL borosilicate glass microreactor type S02 with clamp
  • Two rotary piston pumps with adjustable ceramic pump heads
  • Two thermo & two pressure sensors
  • Electronic control unit
  • 25 mL variable Residence Time Unit (PTFE tube, inner diameter 1/8 in.)
  • Sufficient additional tubing, fittings and helpful tools
  • Comprehensive manuals
  • Convenient transportation case

Figure 12: Microreactor Explorer Kit 19979 Set-Up Example

Figure 17: Transportation case

Figure 18: Microreactor clamp and support rod


MRE Kit 19979 Features
  • All reagent-touching materials metal-free
  • Automated pressure & temperature supervision
  • Temperature range: -70 to 150 °C
  • Flow rates: 0.2 to 15 mL/min/pump at full temperature range (up to 90 mL depending on solvent viscosity and temperature)
  • Max. inner pressure: 6.5 bar
  • Suitable for production scales from g to kg amounts per day proven in industrial environment
  • Compact system fitting into a single fume hood (space saving)
  • The whole system weighs less than 15 kg and can be moved easily between different facilities in its convenient transportation case
  • Easy handling, no special training required
  • Open construction allowing easy system adaptions
  • 120/240 Volt AC input
  • CE compliant

MRE Kit 19979 Benefits
  • Reliable & secure scale-independent chemical synthesis (from R&D to kilo-lab)
  • Accelerated process development (cost savings)
  • Safe handling of highly exothermic reactions or hazardous materials
  • Product profile improvement
  • Side product suppression
  • Protection of unstable products or intermediates
  • Higher product yields with constant & better quality

Microreactor Explorer Kit

19979-1KT

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