Opportunity at National Institute of Standards and Technology (NIST)
Measurement of High-Accuracy Vapor-Liquid Equilibrium Data with NMR Spectroscopy
Material Measurement Laboratory, Applied Chemicals and Materials Division
Please note: This Agency only participates in the February and August reviews.
|Widegren, Jason A
Nuclear magnetic resonance (NMR) spectroscopy has many advantages for quantitative mixture analysis: mole ratios of mixture components can be obtained without calibration; spectral peaks are typically narrow and symmetric; flat baselines are readily obtained; signal averaging can be used to optimize signal-to-noise ratios; a wide range of molecular masses is accessible; and the sample can be gas, liquid, or solid. Despite these advantages, the use of NMR spectroscopy for mixture analysis has been mostly limited to 1H NMR spectroscopy on liquid-phase samples at ambient pressure and room temperature. Our goal is to broaden the use of quantitative NMR spectroscopy for the analysis of multiphasic mixtures over a wide range of temperatures and pressures.
We recently published a proof-of-concept for a complete vapor-liquid equilibrium (VLE) measurement inside an NMR sample tube [Suiter et al., 2020]. This type of novel NMR-based measurement has the potential to overcome the limitations of conventional VLE measurements, but multiple engineering problems stand in the way. For example, the sample cell is placed in a large magnetic field, which causes problems for many temperature and pressure sensors, and the magnetic field limits materials that can be used for the sample cell. Additionally, precise temperature control of the sample is hampered by limitations on the dimensions and placement of the sample cell in the spectrometer. We seek proposals related to any aspect of improved VLE measurements by NMR spectroscopy. We are also interested in the application of NMR spectroscopy to VLE measurements on important mixtures, such as commercially relevant refrigerant mixtures (e.g., replacements for R-410A). A 14 Tesla (600 MHz) NMR spectrometer and a 1.4 Tesla (60 MHz) NMR spectrometer will be available to the researcher.
Suiter, C. L.; Malavé, V.; Garboczi, E.; Widegren, J. A.; McLinden, M. O., Nuclear Magnetic Resonance (NMR) Spectroscopy for the in situ Measurement of Vapor-Liquid Equilibria. J. Chem. Engr. Data 2020, https://pubs.acs.org/doi/10.1021/acs.jced.0c00113.
Nuclear magnetic resonance spectroscopy; NMR; Quantitative NMR; Gas-phase mixtures; Vapor-liquid equilibria; VLE; Temperature measurements; Pressure measurements; Refrigerant mixtures; Mixture model development
Open to U.S. citizens
Open to Postdoctoral applicants