High-throughput continuous-flow system for SABRE hyperpolarization

Signal Amplification By Reversible Exchange (SABRE) is a versatile method for hyperpolarizing small organic molecules that helps to overcome the inherent low signal-to-noise ratio of nuclear magnetic resonance (NMR) measurements. It offers orders of magnitude enhanced signal strength, but the obtained nuclear polarization usually rapidly relaxes, requiring a quick transport of the sample to the spectrometer. Here we report a new design of a polarizing system, which can be used to prepare a continuous flow of SABRE-hyperpolarized sample with a considerable throughput of several millilitres per second and a rapid delivery into an NMR instrument. The polarizer performance under different conditions such as flow rate of the hydrogen or liquid sample is tested by measuring a series of NMR spectra and magnetic resonance images (MRI) of hyperpolarized pyridine in methanol. Results show a capability to continuously produce sample with dramatically enhanced signal over two orders of magnitude. The constant supply of hyperpolarized sample can be exploited, e.g., in experiments requiring multiple repetitions, such as 2D- and 3D-NMR or MRI measurements, and also naturally allows measurements of flow maps, including systems with high flow rates, for which the level of achievable thermal polarization might not be usable any more. In addition, the experiments can be viably carried out in a non-deuterated solvent, due to the effective suppression of the thermal polarization by the fast sample flow. The presented system opens the possibilities for SABRE experiments requiring a long-term, stable and high level of nuclear polarization

Diffusion Measurements of Hydrocarbons in Zeolites with Pulse-Field Gradient Nuclear Magnetic Resonance Spectroscopy

Pulse field gradient NMR technique was used to determine self-diffusivity of heptane and pentadecane at room temperature for microporous catalysts, used both as powders and shaped with a binder extrudates. The results showed that diffusivities increased with increasing specific surface area, micro- and mesopore volume of the studied catalysts. The presence of Bindzil binder together with H-Beta-25 decreased hydrocarbon diffusivities. Self-diffusivities of heptane and pentadecane were smaller for extrudates than for the powder catalysts. The detailed information about mass transfer limitations is needed to further process optimization since effective diffusivity is directly correlated with self-diffusion coefficients. The estimates of the ratio of porosity and tortuosity were also determined. The diffusion measurements with relatively long observation times Delta (20 up to 1000 ms) and catalysts fully immersed in pentadecane revealed that a small portion of sites exhibits very small diffusivities in H-Beta-25-Bindzil extrudates, which is correlated with a low ratio of mesopore to micropore volumes of this material