Improving the Analysis of Phase-Separated Bio-Fuel Samples with Slice-Selective Total Correlation NMR Spectroscopy
Description
NMR data supporting "Improving the Analysis of Phase-Separated Bio-Fuel Samples with Slice-Selective Total Correlation NMR Spectroscopy". ABSTRACT: Pyrolysis oil has been identified as a possible alternative fuel source, however widespread use is hindered by high acidity and water content. These negative characteristics can be mitigated by blending with, for example, mixtures of biodiesel, marine gas oil and butanol. These blended biofuel samples can be unstable and often separate into two distinct phases. Analysis of how the components of any blended biofuel samples partition between the two layers is an important step towards understanding the separation process and may provide insight into mitigating the problem. Slice-selective NMR, where the NMR spectrum of only a thin slice of the total sample is acquired, has been previously used to study, non-invasively, bio-oil samples. Here, the technique is extended and improved, with slice-selective two-dimensional correlation experiments used to resolve the distinct chemical spectra of the various components of the phase-separated blended fuel mixtures. EXPERIMENTAL DETAILS: All ¹H NMR measurements were performed on a 300 MHz Bruker Avance spectrometer at 298 K, using a 5 mm BBO probe equipped with a z gradient coil producing a maximum gradient strength of 0.55 T m⁻¹. For the slice-selective NMR experiments, a G4 cascade was used for the selective pulse, with a 5000 Hz bandwidth and applied at offsets of + and − 5000 Hz, corresponding to the upper and lower layers respectively. A gradient of 5 % of the maximum gradient strength was applied concurrently with the selective pulse. This corresponds to a slice 4.3 mm in width, exciting a slice centred 4.3 mm from the centre of the Gz coils. No deuterated solvents were added to the samples. All NMR experiments were acquired without the use of the lock and shimming was achieved using the area of the acquired FID. The data presented here were all acquired with a slice-selective 2D TOCSY experiment with 256 increments, 8 scans and 16 dummy scans, for an experimental duration of 2 hours and 30 minutes. 1D ¹H experiments of all blended samples were also acquired, using 64 scans, for a duration of 16 seconds. All data were processed using TopSpin 2.1. CONTENTS Data organised by samples. Sample A - zg, two slice-selective 1D, 2D TOCSY Sample B - zg, two slice-selective 1D, two slice-selective 2D TOCSY Sample C - zg, two slice-selective 1D, two slice-selective 2D TOCSY Sample D - zg, two (near-identical) slice-selective 1D, 2D TOCSY Sample E - zg, 2D TOCSY Sample F - zg, 2D TOCSY Pulse sequences - 1D data acquired with Bruker_slice_select, 2D TOCSY data acquired with Bruker_slice_select_TOCSY
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