TY - JOUR
T1 - 1H low field nuclear magnetic resonance relaxometry for probing biodiesel autoxidation
AU - Berman, Paula
AU - Meiri, Nitzan
AU - Linder, Charles
AU - Wiesman, Zeev
N1 - Funding Information:
PB acknowledges support from the Kreitman School of Advanced Studies at Ben-Gurion University of the Negev of the Negev for a short-term post-doctorate fellowship. NM acknowledges support from the Substitutes for Oil Transportation fellowship of the Israel Ministry of Science, Technology and Space . The authors would like to thank Dr. Sofiya Kolusheva and Dr. Anna Milionshchik from the Ilse Katz Institute for Nanoscale Science and Technology at Ben Gurion University, for performing the FTIR and TGA–FTIR measurements; Dr. Keren Adamsky head of the solid state NMR unit at Bar Ilan University for performing the 1 H HF-NMR measurements; Dr. Mark Karpasas and Dr. Raisa Banshatz for performing the dynamic viscosity measurements and other members of the Phyto-Lipid Biotechnology Lab at Ben Gurion University of the Negev, for their contribution to this work.
Publisher Copyright:
© 2016 Elsevier Ltd. All rights reserved.
PY - 2016/8/1
Y1 - 2016/8/1
N2 - The oxidation stability of biodiesel composed of fatty acid esters derived from vegetable oils, is one of the major issues challenging its wide-spread use as an alternative fuel. The poor oxidative stability of biodiesel compared to petrodiesel, is due to its high content of unsaturated fatty acid methyl esters that negatively affects fuel properties such as storage lifetime. Moreover, the relationship between new molecules formed by oxidation and their new solution morphologies is a complex subject that affects physico-chemical properties of the fuel. The goal of this work was to understand how the oxidized unsaturated fatty acid methyl esters and the non-oxidized components of the biodiesel interact and affect the final properties of multi component biodiesel mixtures. Towards this objective standard pure fatty acid methyl esters and biodiesel mixtures were heated for different time periods with constant stirring to induce autoxidation, and then analyzed by 1H low field nuclear magnetic resonance (LF-NMR) relaxometry. To further define the molecular consequence of autoxidation and appearance of autoxidation products, a combination of supporting methods, including, gas chromatography, Fourier transform infrared, 1H high field NMR, and thermogravimetric analysis were used. 1H LF-NMR relaxometry was proven to be an advantageous tool to study autoxidation of biodiesel. It is a direct, rapid, non-destructive method that can be used to study the underlying structural and compositional mechanisms that contribute to changes in the fuel's physico-chemical properties. For example we describe in this paper the interactive effect of new oxidative products and stable non-oxidized components upon each other's molecular movement and morphology during the process of oxidation. One major result was to show that the oxidized products of fatty acid methyl esters have different secondary interactions between themselves and the biodiesel components which were not oxidized but are mutually affected by each other. Characterizing these changes in molecular interactions and how they affect biodiesel properties is one of the major contributions of 1H LF-NMR relaxometry. Also, the possibility of 1H LF-NMR to analyze heterogeneous and at times heterophasic whole samples directly, including their physicochemical state, is of great value when studying the effect of different antioxidants on the oxidation stability of fuels and other food and biological systems.
AB - The oxidation stability of biodiesel composed of fatty acid esters derived from vegetable oils, is one of the major issues challenging its wide-spread use as an alternative fuel. The poor oxidative stability of biodiesel compared to petrodiesel, is due to its high content of unsaturated fatty acid methyl esters that negatively affects fuel properties such as storage lifetime. Moreover, the relationship between new molecules formed by oxidation and their new solution morphologies is a complex subject that affects physico-chemical properties of the fuel. The goal of this work was to understand how the oxidized unsaturated fatty acid methyl esters and the non-oxidized components of the biodiesel interact and affect the final properties of multi component biodiesel mixtures. Towards this objective standard pure fatty acid methyl esters and biodiesel mixtures were heated for different time periods with constant stirring to induce autoxidation, and then analyzed by 1H low field nuclear magnetic resonance (LF-NMR) relaxometry. To further define the molecular consequence of autoxidation and appearance of autoxidation products, a combination of supporting methods, including, gas chromatography, Fourier transform infrared, 1H high field NMR, and thermogravimetric analysis were used. 1H LF-NMR relaxometry was proven to be an advantageous tool to study autoxidation of biodiesel. It is a direct, rapid, non-destructive method that can be used to study the underlying structural and compositional mechanisms that contribute to changes in the fuel's physico-chemical properties. For example we describe in this paper the interactive effect of new oxidative products and stable non-oxidized components upon each other's molecular movement and morphology during the process of oxidation. One major result was to show that the oxidized products of fatty acid methyl esters have different secondary interactions between themselves and the biodiesel components which were not oxidized but are mutually affected by each other. Characterizing these changes in molecular interactions and how they affect biodiesel properties is one of the major contributions of 1H LF-NMR relaxometry. Also, the possibility of 1H LF-NMR to analyze heterogeneous and at times heterophasic whole samples directly, including their physicochemical state, is of great value when studying the effect of different antioxidants on the oxidation stability of fuels and other food and biological systems.
KW - Autoxidation products
KW - Biodiesel autoxidation
KW - H low field nuclear magnetic resonance relaxomtery
KW - Molecular packing
UR - http://www.scopus.com/inward/record.url?scp=84961677935&partnerID=8YFLogxK
U2 - 10.1016/j.fuel.2016.03.002
DO - 10.1016/j.fuel.2016.03.002
M3 - Article
AN - SCOPUS:84961677935
SN - 0016-2361
VL - 177
SP - 315
EP - 325
JO - Fuel
JF - Fuel
ER -
