Influence of Biodiesel on Base Oil Oxidation as Measured by FTICR Mass Spectrometry

Abstract

Internal combustion engine lubricants are subject to thermo-oxidative degradation during use and must be designed to withstand oxidation in order to extend their useful life. Understanding the complex chemical process of thermo-oxidative degradation is essential to designing higher performing engine lubricants. In this study base oil samples composed of a Group II base oil, doped with three different levels of biodiesel (B0, B15, and B100), were subjected to benchtop oxidation testing of up to 168 h, which mimics the conditions experienced in an internal combustion engine. The resulting samples were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for ultrahigh-resolution characterization to monitor oxidation as a function of time and biofuel content. Both negative-ion nanoelectrospray ionization and positive-ion atmospheric pressure photoionization were utilized. Most of the oxidation products were found to be polyoxygenated species containing 1–8 oxygen atoms, with the number of detected species increasing with oxidation time. Assessment of the maximum carbon number of protonated classes indicated the involvement of oligomerization reactions; additionally, modeling of mean double bond equivalents (DBE) for each protonated class suggests increasing carbonyl content for each particular class with increasing oxidation time. The oxidations of B15 and B100 doped samples were compared to that of B0. B15 samples were found to correspond closely to B0 samples, with a similar number of species detected. B100 samples showed a significant increase in number of species generated at 24–72 h relative to B0 and B15; however, a similar number of species were observed at 168 h for all samples, indicating a similar level of base oil oxidation at the final oxidation point. FTICR MS is shown to afford new insights into base oil oxidation as a function of time and biofuel content.

Virtual Special Issue of Recent Advances in Analysis of Fuels and Products by Advanced Mass Spectrometry

“…Jones et al study the thermo-oxidative degradation process by investigating oxidation of base oil doped with three different levels of biodiesel. The oxidation products are monitored with FT-ICR MS, and increased oxygenated compounds are observed with increased oxidation time and biodiesel content.…”

“…List of Papers Published in This Virtual Special Issue are effectively identified on the basis of the retention time, collisional cross section, m/z value, and chemical formula.Jones et al9 study the thermo-oxidative degradation process by investigating oxidation of base oil doped with three different levels of biodiesel. The oxidation products are monitored with FT-ICR MS, and increased oxygenated compounds are observed with increased oxidation time and biodiesel content.…”

Correlation between the Molecular Structure and Viscosity Index of CTL Base Oils Based on Ridge Regression

“…Currently, the main approaches for molecular characterization of base oils are mass spectrometry (MS) and nuclear magnetic resonance (NMR). , MS provides information on the content of different types of compounds and the carbon number of each compound, which allows us to evaluate the changes in hydrocarbon structure types during the hydrogenation process. Nuclear magnetic resonance (NMR), on the other hand, is mainly used to make a certain degree of speculation on the structure of base oils by measuring the content of different types of carbon atoms and calculating some ASPs. − Compared to 1 H NMR, the chemical shifts of 13 C NMR are more sensitive to the molecular structure and can provide more valid information, so the carbon-type distributions it provided are often used as input variables in models for VI calculations.…”

Revealing the Reactivity of Individual Chemical Entities in Complex Mixtures: the Chemistry Behind Bio-Oil Upgrading

“…Complex mixtures such as petroleum-related compounds and bio-oils can also be analyzed by ultrahigh-resolution MS. − The high mass accuracy and high resolving power achieved by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) allows a unique molecular formula to be assigned to each detected composition of a complex sample without any prior fractionation . The sample will comprise thousands of elemental compositions (molecular formulae), which can be assigned as C c H h N n O o S s where c, h, n, o, and s represent the number of carbon, hydrogen, nitrogen, oxygen, and sulfur atoms, respectively .…”