Mobile Low-Field 1H NMR Spectroscopy Desktop Analysis of Biodiesel Production
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Biodiesel produced mainly by the base-catalyzed transesterification of vegetable oils or animal fats with a short chain alcohol, has become an attractive alternative to petroleum-based diesel fuel. Even though high-field 1H nuclear magnetic resonance (NMR) is a reliable method for biodiesel quality control, it is restricted by its poor mobility and expensive superconducting coils. As an alternative, this study presents a mobile low-field 1H NMR spectrometer for the analysis of biodiesel samples derived from different feedstock oils. The low-field 1H NMR spectra of all the compounds coexisting in a typical transesterification reaction such as rapeseed oil, rapeseed biodiesel, methanol, and glycerol, could be clearly differentiated. Field-dependent characteristic parameters such as relaxation times are provided. The degree of saturation of the different biofuels samples could be reliably estimated via integration of the resolved signals of the spectra. The obtained results agreed well with those measured at high-field 1H NMR. Since this compositional information is directly related to the biodiesel properties, the presented mobile low-field 1H NMR device built from permanent magnets arrayed in a Halbach geometry, constitutes an excellent alternative tool for biodiesel quality control.
KeywordsNuclear Magnetic Resonance Transesterification Reaction Linolenic Acid Methyl Ester Fame Profile Oleic Acid Methyl Ester
We thank the Deutsche Forschungsgemeinschaft (DFG), Deutscher Akademischer Austausch Dienst (DAAD) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for their financial support of this project.
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