Issue 8, 2013

Remote detection NMR imaging of gas phase hydrogenation in microfluidic chips

Abstract

The heterogeneous hydrogenation reaction of propene into propane in microreactors is studied by remote detection (RD) nuclear magnetic resonance (NMR). The reactors consist of 36 parallel microchannels (50 × 50 μm2 cross sections) coated with a platinum catalyst. We show that RD NMR is capable of monitoring reactions with sub-millimeter spatial resolution over a field-of-view of 30 × 8 mm2 with a steady-state time-of-flight time resolution in the tens of milliseconds range. The method enables the visualization of active zones in the reactors, and time-of-flight is used to image the flow velocity variations inside the reactor. The overall reaction yields determined by NMR varied from 10% to 50%, depending on the flow rate, temperature and length of the reaction channels. The reaction yield was highest for the channels with the lowest flow velocity. Propane T1 relaxation time in the channels, estimated by means of RD NMR images, was 270 ± 18 ms. No parahydrogen-induced polarization (PHIP) was observed in experiments carried out using parahydrogen-enriched H2, indicating fast spreading of the hydrogen atoms on the sputtered Pt surface. In spite of the low concentration of gases, RD NMR made imaging of gas phase hydrogenation of propene in microreactors feasible, and it is a highly versatile method for characterizing on-chip chemical reactions.

Graphical abstract: Remote detection NMR imaging of gas phase hydrogenation in microfluidic chips

Supplementary files

Article information

Article type
Paper
Submitted
27 Nov 2012
Accepted
25 Jan 2013
First published
28 Jan 2013

Lab Chip, 2013,13, 1554-1561

Remote detection NMR imaging of gas phase hydrogenation in microfluidic chips

V. V. Zhivonitko, V. Telkki, J. Leppäniemi, G. Scotti, S. Franssila and I. V. Koptyug, Lab Chip, 2013, 13, 1554 DOI: 10.1039/C3LC41309H

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