Probing the Carbonyl Functionality of a Petroleum Resin and Asphaltene through Oximation and Schiff Base Formation in Conjunction with N-15 NMR

Abstract

Despite recent advances in spectroscopic techniques, there is uncertainty regarding the nature of the carbonyl groups in the asphaltene and resin fractions of crude oil, information necessary for an understanding of the physical properties and environmental fate of these materials. Carbonyl and hydroxyl group functionalities are not observed in natural abundance 13C nuclear magnetic resonance (NMR) spectra of asphaltenes and resins and therefore require spin labeling techniques for detection. In this study, the carbonyl functionalities of the resin and asphaltene fractions from a light aliphatic crude oil that is the source of groundwater contamination at the long term USGS study site near Bemidji, Minnesota, have been examined through reaction with 15N-labeled hydroxylamine and aniline in conjunction with analysis by solid and liquid state 15N NMR. Ketone groups were revealed through 15N NMR detection of their oxime and Schiff base derivatives, and esters through their hydroxamic acid derivatives. Anilinohydroquinone adducts provided evidence for quinones. Some possible configurations of the ketone groups in the resin and asphaltene fractions can be inferred from a consideration of the likely reactions that lead to heterocyclic condensation products with aniline and to the Beckmann reaction products from the initially formed oximes. These include aromatic ketones and ketones adjacent to quaternary carbon centers, β-hydroxyketones, β-diketones, and β-ketoesters. In a solid state cross polarization/magic angle spinning (CP/MAS) 15N NMR spectrum recorded on the underivatized asphaltene as a control, carbazole and pyrrole-like nitrogens were the major naturally abundant nitrogens detected.

Distribution of Oxygen-Containing Compounds and Its Significance on Total Organic Acid Content in Crude Oils by ESI Negative Ion FT-ICR MS

“…For instance, CU showed a 12.8% for the O2 class in F1, even though there was no evidence of the presence of carboxylic acids in its nonacidic fraction according to its IR spectrum (Figure b). This opens the possibility of considering, for some crude oils, that an important percentage of compounds comprised in class O2 corresponds to other oxygen-containing compounds, such as phenolic hydroxyls, ketones, and esters, as well as cyclic and/or acyclic ethers. , By comparing the O2 classes for F1 and F2, significant molecular level differences were established in samples with low TAN (<0.5 mg KOH/g). DBE vs carbon number contour plots for the O2 class are shown in Figure .…”

Time-dependent multivariate and spectroscopic characterisation of oil residue in Niger Delta soil

“…[47][48][49][50] It is explicit in describing structural parameters of crude oil and its fractions. [51][52][53][54][55] Multidimensional NMR experiments such as correlation spectroscopy (COSY), heteronuclear correlation (HETCOR), and heteronuclear single quantum coherence (HSQC) spectroscopy have yielded important information about 1 H-1 H and 1 H- 13 C connectivity in petroleum molecules as well as the chemistry of crude oil with respect to functional groups present. 55,56 As a result of the variations in environmental conditions and time, true composition of oil residue varies as it ages in soil.…”

Characterization of the partial oxidation products of crude oil contaminating groundwater at the U.S. Geological Survey Bemidji research site in Minnesota by elemental analysis, radiocarbon dating, nuclear magnetic resonance spectroscopy, and Fourier transform ion cyclotron resonance mass spectrometry

“…The sp3 hybridized carbon calculation excludes anomeric carbons that can overlap with protonated aromatic carbons from 90-110 ppm. (Thorn and Cox, 2015). The major form of nitrogen in the asphaltene fraction appears to be carbazole (Thorn and Cox, 2015), evident from the peak at 113 ppm in the natural abundance CP/MAS 15 N NMR spectrum of figure 9.…”

“…(Thorn and Cox, 2015). The major form of nitrogen in the asphaltene fraction appears to be carbazole (Thorn and Cox, 2015), evident from the peak at 113 ppm in the natural abundance CP/MAS 15 N NMR spectrum of figure 9.…”

“…The two major peaks in the ACOUSTIC spectrum are the unreacted aniline at 57 ppm and the imines at 324 ppm, the latter resulting from 1,2-nucleophilic addition of aniline to quinone groups (Schiff base formation). Peaks at 79 and 95 ppm in the INEPT spectrum correspond to anilinohydroquinone and anilinoquinone adducts, respectively, from 1,4-nucleophilic addition of aniline to quinones (Thorn and Cox, 2015). The peak at 136 ppm corresponds to heterocyclic nitrogens (indole and quinolone, for example) resulting from intramolecular condensation reactions of aniline with carbonyl groups.…”