MODULAR ATR FT-IR MICROREACTOR CHIP FOR
OPTIMIZING REACTION CONDITIONS
Jasper J.A. Lozeman, Jeroen C. Vollenbroek, Johan G. Bomer, Hans L. de Boer, Albert van den Berg, Mathieu Odijk
BIOS Lab-on-a-Chip Group, MESA+ Institute for Nanotechnology, Technical Medical Centre, Max Planck Center for Complex Fluid Dynamics, University of Twente, Enschede, The Netherlands.
A silicon chip for attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy in combination with a modular herringbone
mixer
1and a microreactor has been successfully fabricated and tested. The modular design allows the chip to be used for a variety of reactions. A
model synthesis of 1-butyl-2,5-dimethyl-1H-pyrrole from hexane-2,5-dione with 1-butylamine has been performed on chip. When plotting the
natural logarithm of the peak area corresponding to the ketone stretch vibration at 1710cm
-1against the residence time, a linear curve can be
fitted, suggesting this step to be a first order reaction.
Chip Design
0.0 0.1 0.2 0.3 0.4 0.5 1000 1100 1200 1300 1400 1500 1600 1700 1800 Ab so rb an ce [a .u .] Wavenumber [cm-1] Fingerprint region 3.5min 10.5min 21.0min y = -0.2029x + 2.7719 R² = 0.995 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 0 5 10 15 20 25 ln (p eak ar ea [a .u .])Residence time [min]
Ketone peak area over time
Reaction Monitoring
Synthesis of 1-butyl-2,5-dimethyl-1H-pyrrole from hexane-2,5-dione and 1-butylamine. The reactants are mixed by the herringbone mixer, flow is stopped once the reaction chamber is filled. Next, every 3.5min a IR spectrum is generated.
FT-IR spectra over time. The broad peak at 3200cm-1,
corresponding to the formation of water, increases over time.
FT-IR spectra at 1800-1000cm-1. The ketone peak at
1710cm-1 decreases over time, while the peaks at
1525cm-1 (skeleton vibration) and 1300cm-1 (C-N
stretch) increase overtime5,6.
Reaction chamber Mixing channel 30mm
Top View
Bottom View The ATR crystal, an adaptation of
earlier designs3,4, is made of
silicon. This crystal, the bottom layer of the device, is used for IR-ATR sensing. To couple light into the silicon, facets are fabricated using KOH etching. The reaction chamber and mixing channel, fabricated from PDMS, PMMA, Teflon or COC, are modular in the sense that they can be stacked. The mixing channels mix by using herringbone mixers1. Channel
dimensions: H=100µm W=200µm.
References
[1] A.D. Stroock, et al. Science. 5555 (2002) 647–651. [2] K.F. Jensen, Chem. Eng. Sci. 2 (2001) 293–303.
[3] A. Susarrey-Arce, et al. Sensors Actuators B Chem. (2015) 13-21.
[4] E. Karabudak, et al. Anal. Chem. 7 (2012) 3132-3137. [5] E. Pretsch et al. Structure Determination of Organic Compound, 2009.
[6] D.L. Howard, et al. J. Phys. Chem. A. 29 (2015) 7980– 7990.
The current setup is lacking in analysis speed. Therefore a new IR spectrometer, using a tunable quantum cascade laser has been purchased from IRSweep. The laser, which not only has a time resolution in the microsecond range, also has an higher power output, increasing signal to noise.
Modular Design
A B C B C E D F A GModular design of the chip allows for a variety of reactions to be monitored. The simplest combination (left) has been used to obtain the results presented in this poster. A more complex design (right), can currently use up to 3 layers. Parallelization with multiple chips, could also increase the amount of reaction components.
Conventional
IR spectrometer Temperature Ratios of reactants Concentrations Mixing speed Measure products Change variablesA setup is proposed, using microfluidic flow chemistry (MFC), in which the reactions conditions can be changed in real-time, while measuring the formed products online. MFC allows for better control over temperature, concentrations and mass transport than conventional laboratory setups2.
Additional benefit of online analysis is further insight in reaction kinetics and intermediate products. 0.0 0.1 0.2 0.3 0.4 0.5 1000 1500 2000 2500 3000 3500 4000 Ab sor ba nc e [a .u .] Wavenumber [cm-1]
IR spectra over time
3.5min 10.5min 21.0min
The natural logarithm of the peak area at 1710cm-1, plotted
against the residence time. The linear fit suggests a first order reaction. Run reaction IR spectrometer Syringe pump Resistor (heating)
Acknowledgement
We would like to thank Max Krakers for the design of the herringbone mixer mask.
We would like to thank Tobias Elsbecker for fabricating the PMMA, Teflon and COC reaction chamber and mixer channels, and his to continuing contribution to the project.
Outlook
Proposed Concept
Facets
This work was supported by the Netherlands Center for Multiscale Catalytic Energy Conversion (MCEC), and NWO Gravitation programme funded by the Ministry of Education, Culture and Science of the government of the Netherlands.
