ESTUDO DE ÁCIDOS ORGÂNICOS DE ALTA MASSA MOLECULAR PRESENTES EM PETRÓLEO E DEPÓSITOS NAFTÊNICOS
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Data
2022-03-23
Autores
Barros, Eliane Valeria de
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Universidade Federal do Espírito Santo
Resumo
Among the controversies presented regarding the definition of naphthenic acids (NAs), we will focus on that NAs are carboxylic acids found naturally in crude oil, considering classic NAs (monoacids) and polyacids. Throughout Chapter 1, we will discuss a revision about NAs highlighting the challenges of the petroleum industry in the processing of acid petroleum, related phenomena to it. An exploratory bibliometric consultation highlights the expansion in the number of publications about NAs from the 2000s onwards. Advances in chemical characterization analyses contributed to discovering a specific group of high molecular weight tetrameric NAs, sometimes-called ARN, precursors of calcium naphthenate deposits, whose discussion will receive special attention. Here, we present the primary extraction and characterization techniques used in the elucidation of NAs, in which Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) stands out. In chapter 2 we propose a method for isolating ARN by solid phase extraction (SPE) from naphthenate deposits. The ESI(-)FT-ICR MS results showed that the strategy provided an optimal separation of acids with a distinct Mw range. The high resolution and mass accuracy indicated that one of the fractions concentrated only the ARN species, which were identified from their characteristic fragmentation patterns by ESI(-)MS/MS experiments. The integrations of the 1H and 13C nuclear magnetic resonance (NMR) spectra of the acidic fractions highlighted the expressive presence of alkyl compounds and the absence of aromatic hydrogens in the subfraction of interest. Orbitrap MS offered high-resolution power and mass accuracy like FT-ICR MS, proving to be convenient for elucidating complex mixtures of NAs with an important differential in the economic viability offered by the technique. The SPE extraction developed provided the isolation of ARN acids with a purity of the order of 95% (according to the 1H NMR results), compared to the 84% achieved without this step, substantially increasing the efficiency of the method for obtaining reference of precursor acids of calcium naphthenates deposits. In Chapter 3 we propose the use of a new analysis methodology for the identification of these species in oil samples and naphthenate deposits in situ. This methodology is based on an unconventional approach of using ESI(-)FT-ICR MS, doping the sample with formic acid to transform the ARN salts into their mono or unloaded form. This methodology proved to be promising and advantageous, as it requires simpler sample preparation, reduced consumption of reagents and analysis time. With good feasibility of application to identify the nature of the deposits and also to estimate in the initial phase the potential for incrustation and the need for oil treatment in the production units.
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Ácidos Naftênicos , ARN , Depósitos de Naftenato , Métodos de Extração , Preparo de Amostra , ESI(-)FT-ICR MS