Type of Document	Dissertation
Author	Stanford, Lateefah Ain
Author's Email Address	lateefahstanford@hotmail.com
URN	etd-06302006-140003
Title	Characterization of Naturally Occurring Surface- and Interface-Active Molecules in Petrochemicals by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
Degree	Doctor of Philosophy
Department	Chemistry and Biochemistry, Department of
Advisory Committee	Advisor Name Title Dr. Alan G. Marshall Committee Chair Dr. Albert E. Stiegman Committee Member Dr. Ryan P. Rodgers Committee Member Dr. William M. Landing Committee Member Dr. William T. Cooper Committee Member
Keywords	biodegradation emulsions water-solubles FT-ICR MS ion cyclotron resonance mass spectrometry petroleum asphaltenes
Date of Defense	2006-06-20
Availability	unrestricted
Abstract High-resolution electrospray ionization Fourier Transform Ion Cyclotron Mass Spectrometry (ESI FT-ICR MS) is a robust method for identifying polar nitrogen, sulfur, and oxygen (–NSO) containing compounds in naturally occurring complex mixtures (i.e. coal, humic acids, crude oil, etc…) as it affords an average mass resolution m/Δm50% ≥100, 000 and mass accuracy <0.3 ppm. In Chapter 3, we apply ESI FT-ICR MS to track compositional changes in crude oil –NSO compounds induced by in-reservoir microbial degradation. We observe a marked decrease in spectral complexity as microbial degradation of the selected oil increases. By negative-ion ESI FT-ICR MS, we reveal evidence of extensive degradation of –NSO species, previously regarded as resistant to degradation. Biodegradation alters the compound class distributions to different degrees. O, O3, O4, NO, N2O, SO2, SO3 and NS species decrease, whereas O2, SO, S2O heteroatomic class hydrocarbons increase in relative abundance with increased biodegradation. In conclusion, biodegradation may decrease the total petroleum hydrocarbons, however species undesirable to industrial processes and environmental ecology (i.e. Ox, and SOx compounds) appear to increase with degradation. For years, the petroleum industry has suffered financial losses because of polar organics that self-assemble as precipitates that plug transfer lines or corrode metal surfaces during vacuum gas oil distillation. Current research presumes that a select group of O2 class acids and sulfoxides are responsible for crude oil corrosivity during vacuum gas oil distillation. As demonstrated in Chapter 3, sulfoxides arise from the aerobic biodegradation of thiophenes whereas O2 class compounds arise from the degradation of pure hydrocarbons. The petroleum industry relies upon catalytic hydrotreatment to remove the above undesirable compounds. However, specific –NSO compounds poison catalysts and hydrotreatment removal of other undesirable –NSO compounds. In the quest to solve this issue, in Chapter 4 we characterize acidic and basic –NSO species in vacuum gas oil light, middle, and heavy distillates from an acidic vacuum gas oil. Each distillate was exhaustively characterized by mass, heteroatom class, type (rings plus double bonds), and carbon number distribution to mark compositional trends with increased distillation temperature. The light distillate fraction exhibits monoaromatic and low double bond equivalence (DBE) polycyclic species. Low molecular weight polycyclic, monoaromatic carboxylic acids, and oxygen-sulfur (SxOy) species solely populate the negative-ion mass spectrum of the light distillate. In contrast, the middle and heavy distillates are composed of high molecular weight and high DBE polyaromatic pyrrolic, phenolic, and carboxylic acids. The chemical properties and characteristics of polar species (represent <15% composition) in petroleum derived materials, threaten environmental wellness. In order for petroleum refineries to meet standards set by the Environmental Protection Agency (EPA) to decrease environmental risk, it is necessary to determine the chemical composition of potential environmentally hazardous compounds in petroleum. In Chapter 5, we explore the solubility limitations of crude oil organic acids in fresh and seawater, regarding heteroatomic class, aromaticity, and molecular weight through negative-ion ESI FT-ICR MS. We identify water-soluble (23 ºC) crude oil NSO non-volatile acidic crude oil hydrocarbons by negative-ion ESI FT-ICR MS at an average mass resolving power, m/Δm50% = 550,000. Of the 7,000+ singly-charged acidic species identified in South American crude oil, surprisingly many are water-soluble, and much more so in pure water (1,441) than in seawater (768). Water-soluble heteroatomic classes detected at >1% relative abundance include O, O2, O3, O4, OS, O2S, O3S, O4S, NO2, NO3, and NO4. The abundance of parent oil classes do not directly relate to abundance in the water-soluble fraction. Classes containing one oxygen (presumably phenolics) and (especially) two oxygens (presumably carboxylic acids) exhibit the highest solubility. Highly alkylated O2 species soluble in pure water preferentially "salt out" in seawater. O3S is the most abundant OxS class in each sample. OS, O2S and O4S compounds are present in the crude oil but do not dissolve significantly in fresh or salt water. Polyaromatic pure hydrocarbons and non-acidic nitrogen containing hydrocarbons are highly toxic to aquatic organisms. For this cause in Chapter 6, we utilize positive-ion ESI FT-ICR MS to analyze South American and North American crude oils and their polar -NSO containing distilled water-soluble basic species and FD FT-ICR MS to analyze their basic and neutral species. We identify water-soluble (23 ºC) crude oil NSO non-volatile basic and neutral hydrocarbons by positive-ion ESI and continuous flow FD FT-ICR MS at an average mass resolving power, m/Δm50% = 550,000. In contrast to acidic nitrogen-containing heteroatomic classes, basic nitrogen classes are water-soluble. Water-soluble heteroatomic basic classes detected at >1% relative abundance include N, NO, NO2, NS, NS2, NOS, NO2S, N2, N2O, N2O2, OS, O2S, and O2S2. Of the 8,000+ singly-charged basic species identified in South American crude oil, ~1,800 are water-soluble. At nominal mass, we resolve up to 14 peaks above a threshold of 3σ of baseline noise in the positive-ion electrospray water-soluble base mass spectrum. The data clearly confirm reduced solubility with increasing degree of alkylation for a given aromatic core. Among the Nx classes, N1 species are more prevalent in the parent crude oil, whereas N2 species are most prevalent for the water solubles. DBE and carbon number strongly limit solubility for both neutral classes and bases. Many of the water-soluble crude oil species identified in Chapters 5 and 6 are surface active and stabilize water-in-oil emulsions. In Chapter 7, by complimentary use of negative- and positive-ion ESI, and FD FT-ICR MS, we investigate the changes in non-volatile acidic, basic, and neutral hydrocarbon water-in-bitumen emulsion stabilizers, with respect to bitumen concentration in heptol diluent. Singly charged heteroatomic bitumen emulsion stabilizers, populate the positive- and negative-ion ESI FT-ICR mass spectra over an impressive mass range from 300 < m/z < 900. Highly condensed aromatic basic, nonpolar, and acidic species stabilize emulsions at high bitumen concentrations. Emulsion stabilizers are less aromatic at low bitumen concentrations. Furthermore, all basic and most nonpolar emulsion stabilizers are below detected limits in low bitumen concentration emulsion films. In Chapter 8, by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) we identify non-volatile polar acidic and basic emulsion stabilizers in nine geographically distinct light, medium, and heavy oils. Oil class compositions are unique, however oils of similar API gravity follow similar percent relative abundances for the O2 and O4S classes. Heavy oils are high in O2 and low in low O4S. The light oils follow the opposite trend. However, independent of parent oil O2 and O4S class abundances, O2 and O4S species preferentially adsorb and are the two most abundant classes in the emulsion interfacial material. Negative-ion nitrogen containing classes do not have a high affinity for emulsion interface adsorption. However all positive-ion nitrogen containing species indiscriminately adsorb to the oil/water interface.
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