Fractionation and Characterization of Mexican Crude Oils

Abstract

Crude oils are intricate mixtures of hydrocarbon compounds; different physicochemical characterizations must be performed to get to know their complexity. A series of four typical Mexican Crude Oils (MCOs) with densities ranging from 30 to 9 °API was characterized through different physical, spectroscopic, and thermal methods. The four types of MCOs were also fractionated into saturates, aromatics, resins, and asphaltenes (SARA) through high-performance liquid chromatography (HPLC). The fractions obtained were subsequently characterized through different physicochemical techniques such as Fourier transform infrared (FTIR) spectroscopy, vapor pressure osmometry (VPO), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). VPO led to determining the average molar mass of each MCO fraction to be compared to those of the different Mexican petroleums. It was clearly observed that the molar mass of the resin and asphaltene fractions increases when crude oil gets heavier than saturate and aromatic components. The thermal stability of the series of MCOs was evaluated by TGA observing that the decomposition temperature increases with the average molecular mass of the crude oil. The original heavy crude oil and its fractions were studied through differential scanning calorimetry (DSC); the study of heat effects associated to phase transitions was monitored for each fraction, resulting into the Wax dissolution temperature (WDT) and the Wax precipitation temperature (WPT) of the four MCOs investigated. It was established that the different molecular features of crude oils may be clearly correlated to their average molar mass.

Asphaltene fractionation based on adsorption onto calcium carbonate: Part 1. Characterization of sub-fractions and QCM-D measurements

“…Absorption bands observed between 900 cm -1 and 700 cm -1 are due to different aromatic C-H bending deformations. [58] The band around 880 cm -1 indicates the presence of highly substituted aromatic structure [59] and this was found to be highest for bulk fraction and lowest for fraction irreversibly-adsorbed HCl . Again, the higher absorbance intensity for bulk fraction at this wavenumber could be due to the CaCO3 contamination.…”

In situ catalytic upgrading of heavy crude oil through low-temperature oxidation

“…4a, absorption peaks in Fig. 4c at 1023 and 1162 cm -1 were weakened, and the absorption peak at 1267 cm -1 has nearly disappeared, indicating the breakage of C-N, C-O, and C-S bonds; the absorption peak at 796 cm -1 was also weakened, showing the removal of the existing alkyl side chain; the absorption peak at 868 cm -1 became weaker, implying the occurrence of ring-opening reactions (Castro and Vazquez 2009). As well, the absorption peak at 1374 cm -1 was enhanced in Fig.…”

“…It is acknowledged that condensed aromatic rings form the main structure of resin and asphaltene. Rich fatty structural units connected to the aromatic rings, complex branched structures, and a high degree of aromatization make the molecular structure exhibit strong polarity and make it easy to be attacked by oxygen atoms, which contribute to a fast oxidation reaction rate and large reactivity for resin and asphaltene at low temperatures (Castro and Vazquez 2009;Chen et al 2013b). In general, there will be a series of reactions between crude oil and oxygen once they are in contact.…”

Avaliação De Asfaltenos Precipitados Em Diferentes Condições De Composição, Temperatura E Pressão

“…41,46 As amostras de asfaltenos apresentaram bandas relativas aos grupos aromáticos (CH) na região de 1620 -1590 cm -1 e aos grupos metil e metileno (CH) na faixa de 1500 -1350 cm -1 ; uma banda em 1462 cm -1 está provavelmente relacionada à deformação angular simétrica do grupo metileno (CH 2 ) em hidrocarbonetos; uma banda em 1456 cm -1 está próxima à banda de deformação angular assimétrica do grupo metila (CH 3 ); bandas em 1376 cm -1 sugerem vibração de deformação angular simétrica do grupo metila. 41,47 Em torno de 1000 cm -1 são encontradas bandas relacionadas a funções oxigenadas, 42,47 sendo que na faixa de 1030-1040 cm -1 estão bandas específicas de grupos sulfóxidos (S=O). 36,46,48 Bandas em torno de 720 cm -1 , mais intensas nas amostras do P01, correspondem, à presença do grupo metileno em cadeias alifáticas longas; já a banda em 694 cm -1 , presente nos asfaltenos obtidos pela norma IP143, pode estar relacionada a um anel aromático monossubstituído, como o fenol.…”