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The contents of saturates, aromatics, and polars in crude oil were determined using carbon-13 nuclear magnetic resonance spectroscopy ( 13 C NMR) associated with support vector regression (SVR) and a genetic algorithm (GA) for the simultaneous selection of spectral variables and SVR model parameters. The developed models presented prediction sample errors of 4.4% (w/w) for saturates, 4.3% (w/w) for aromatics (w/w), and 3.7% (w/w) for polars. These results are acceptable for the petroleum industry, considering that the error obtained by the standard methodology is 5% (w/w), which is the maximum value of variation allowed in SARA analysis. The proposed methodology made these determinations using small amounts of samples (approximately 2 mL) in a relatively short time (approximately 2 h).

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http://rvq.sbq.org.br Melhoria no Ponto de Fluidez de Óleos Pesados pela Adição de Solventes OrgânicosResumo: Este artigo descreve o comportamento do ponto de fluidez de três óleos pesados com adição de querosene, aguarrás, tolueno e condensado de gás. O estudo mostrou um decaimento no ponto de fluidez de todos os óleos que se relaciona com a composição química dos óleos. O óleo com menor grau API (maior quantidade de asfaltenos e resinas) apresentou maior decaimento do ponto de fluidez para todos os solventes, destacando o condensado de gás e a aguarrás. O uso de condensado de gás para reduzir o ponto de fluidez de óleos pesados é particularmente vantajoso, quando disponível no campo petrolífero. Previne a paralisação na produção de óleo, devido a obstrução e problemas de fluxo nos dutos, e facilita a logística, reduzindo os custos operacionais do processo.Palavras-chave: Óleos pesados; ponto de fluidez; solventes orgânicos. AbstractThis paper describes the pour point behavior of three heavy oils with the addition of kerosene, turpentine, toluene and gas condensate. The study showed a decrease in the pour point of all oils related to their chemical composition. The oil with the lowest API gravity (high amount of asphaltenes and resins) showed the highest pour point decay for all solvents, highlighting gas condensate and turpentine. The use of gas condensate to reduce the pour point of heavy oils is particularly advantageous, when it is available in the oilfield. It also prevent halt in oil production, due to pipeline clogging and flow problems, and facilitate the logistics, reducing operational costs in the process.

Hydrocarbons present in saturated fractions of crude oils can be assessed by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as ionizing reagents in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). In this work, five paraffin standards of different average molar mass distributions (M w) were easily ionized by APCI(+)FT-ICR MS using isooctane as the reagent gas. Data of M w , carbon number and double bond equivalent (DBE) distributions corresponding to linear and cyclic hydrocarbons (HCs) were compared to results obtained from analysis of high temperature gas chromatography with a flame ionization detector (HTGC-FID), comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) and 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. APCI(+)FT-ICR MS data showed good agreement with those of analytical techniques. Furthermore, the ability of APCI(+) to assess n-paraffin, even in blends with polyaromatic hydrocarbon molecules such as coronene (M w = 301 Da) at concentrations from 2.5 to 25 µg mL-1 , was demonstrated. The typical MS paraffin profile (containing repeating mass units of 14 Da) was clearly confirmed, being totally suppressed when a concentration of 25 µg mL-1 of coronene was used. This phenomenon was also evidenced in one of two saturated fractions produced using saturates, aromatics and polar (SAP) compound fractionation methodology.

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Document examination to determine document authenticity is an important field in forensic science.