Composition analysis of natural gas by combined benchtop NMR spectroscopy and mechanistical multivariate regression

Refined high-pressure tube design for improved resolution in high-pressure NMR spectroscopy

“…These paramagnetic particles penetrated the sapphire material, leading to broader and unsymmetric peaks in the NMR spectrum. 19,33 Hence, 5 mm o.d. tubes without a flange, 3.2 mm i.d., and a length of 178 mm were purchased from Rototec-Spintec GmbH (Bad Wildbad, Germany).…”

“…The immense improvement in spectral resolution, as demonstrated by various comparisons, allows the utilization of HP benchtop NMR spectroscopy for an analysis of even more complex spectra than those presented in ref. 19 and 33. Within the frame of the current work, the pressure-dependent H 2 solubility in 2-methylfuran and 2-methyltetrahydrofuran (2-MTHF) is reported.…”

“…19 Despite the spectral distortions induced by the used HP sapphire NMR tube, this HP benchtop NMR setup combined with chemometrics could successfully quantify the composition of complex hydrocarbon gas mixtures with less than 0.5% disparities from dedicated gas chromatography (GC) analysis. 33 To push HP NMR's capabilities even further and allow the scientific community to have easier access to HP equipment, we present a refined low-cost sapphire tube design. Although the original sapphire tube construction 17 had continuously been revised, 28–30 multiple improvements are introduced with this model: (a) better sapphire quality to improve sensitivity and SNR, (b) a PEEK attachment to abolish the bulky metal body affecting the magnetic field homogeneity and the instrument's temperature stability, 19,22,28 and (c) no punctual stress on the sapphire tube, which can lead to cracks.…”

“…To demonstrate the capabilities of this HP NMR tube, it was used in conjunction with the same compact NMR spectrometer by replacing the previous tube used in ref. 19 and 33. The immense improvement in spectral resolution, as demonstrated by various comparisons, allows the utilization of HP benchtop NMR spectroscopy for an analysis of even more complex spectra than those presented in ref.…”

“…For instance, ref. 33 demonstrated that a linewidth decrease of only 13.3% at half height approximately halved the quantification error of component quantification of complex hydrocarbon gas mixtures when employing indirect hard modeling, a mechanistical multivariate regression technique. Moreover, the improved resolution and SNR is particularly advantageous for specimen with more complex NMR spectral patterns, like in HP reaction monitoring, foodstuffs, fuels, and many more.…”