Chemical Reaction Monitoring using Zero‐Field Nuclear Magnetic Resonance Enables Study of Heterogeneous Samples in Metal Containers

Abstract

We demonstrate that heterogeneous/biphasic chemical reactions can be monitored with high spectroscopic resolution using zero‐field nuclear magnetic resonance spectroscopy. This is possible because magnetic susceptibility broadening is negligible at ultralow magnetic fields. We show the two‐step hydrogenation of dimethyl acetylenedicarboxylate with para‐enriched hydrogen gas in conventional glass NMR tubes, as well as in a titanium tube. The low frequency zero‐field NMR signals ensure that there is no significant signal attenuation arising from shielding by the electrically conductive sample container. This method paves the way for in situ monitoring of reactions in complex heterogeneous multiphase systems and in reactors made of conductive materials while maintaining resolution and chemical specificity.

Towards large‐scale steady‐state enhanced nuclear magnetization with in situ detection

“…In principle, signal acquisition can be performed directly during the bubbling. 39 In order to study the magnetic-field dependence of the polarization transfer during in situ ZULF-SABRE experiments, a variable magnetic field in the range of -3 µT to 3 µT was applied during the bubbling. A plot of the maximum signal amplitude over the applied magnetic field strength is shown in Fig.…”