Thermal Cracking Characteristics and Kinetics of Oil Sand Bitumen and Its SARA Fractions by TG–FTIR

Abstract

The thermal cracking process of oil sand bitumen was investigated via studying the thermal cracking behaviors and online-gas-releasing characteristics of its SARA fractions (saturates, aromatics, resins, asphaltenes) by using TG−FTIR. The results showed that the asphaltenes contributed the most to coke formation of oil sad bitumen according to its largest weighted coke yield compared with that of others. The online FTIR analysis for the gases evolved from the thermal cracking process of oil sand bitumen and its SARA fractions indicated that the gaseous products in the main reaction stage showed more complex composition than those in the volatilization stage, and predominantly consisted of CO 2 , CO, methane, ethylene, other light alkanes and olefins, light aromatics, and hydrogen sulfide. Moreover, the release behaviors of typical gaseous products (CO 2 , CO, methane, ethylene, and light aromatics) for oil sand bitumen and its SARA fractions were different due to the different composition and structure. The thermal-cracking kinetic parameters of oil sand bitumen and its SARA fractions were determined using the iso-conversional Friedman procedure at heating rates of 10 to 800 K/min. The activation energy of oil sand bitumen ranging from 93.74 to 215.99 kJ/mol in the whole thermal cracking process fell in between that of aromatics and resins. The variation of activation energy with the conversion rate for oil sand bitumen during the thermal cracking process was influenced by the interaction between SARA fractions.

Structure of Wangqing oil shale and mechanism of carbon monoxide release during its pyrolysis

“…In this stage, the mass loss is mainly due to the evaporation of water, the release of a small amount of adsorbed gas, and the decomposition of some organic matter having low bond energy. The decomposition and rearrangement of pyrolytic bitumen molecules, associated with the release of volatile substances in oil shale, are also accompanied by the pyrolysis of certain minerals, which represents the transition stage of pyrolysis …”

“…This method can produce theoretical results without knowing the reaction mechanism, whereas the obtained data are more accurate . According to the weight loss of oil sands, Hao et al calculated the conversion‐related kinetic parameters at different heating rates and reported that the activation energy values lied within the range of 93.74‐215.99 kJ/mol. Scaccia et al studied the nonisothermal kinetics of coal using iso‐conversion method and found that the apparent activation energy remained almost constant when the conversion rate was within the range of 5%‐40%, indicating that the process consisted of an elementary reaction.…”

Quantification of low‐temperature oxidation of light oil and its SAR fractions with TG‐DSC and TG‐FTIR analysis

“…As for the heat flow (see Figure B), the cumulated values are close to the measured ones within the test temperature range except those at 130‐240°C (loss of light hydrocarbons) and 480‐560°C (excluding asphaltene). Asphaltene is the heaviest fraction in crude oil and important source of combustion fuel at the HTO phase . In addition, the interaction between SARA fractions during the reaction is also an important reason for the differences between the cumulated and measured values …”

“…However, both the main components involved in the LTO reaction and the differences associated with the oxidation characteristics among different components have not been well understood. To quantify the oxidation characteristics of crude oils, thermal analysis such as thermogravimetric analysis and differential scanning calorimetry (TG‐DSC), pressure differential scanning calorimetry (PDSC), and thermogravimetric analysis coupled with Fourier transform infrared spectrometer (TG‐FTIR) have been applied to investigate the oxidation properties of crude oil and its SARA fractions, as summarized in Table . Also, this table tabulates the reaction modes and characteristics during the combustion of light and heavy oils, the kinetics and thermochemical parameters of each reaction mode, the differences of oxidation characteristics between light, medium, and heavy oils, the oxidation relationship of crude oil and SARA fractions during the combustion process, and the combustion process of asphalt binder and its SARA fractions, respectively.…”

Characterization of bitumen and a novel multiple synergistic method for reducing bitumen viscosity with nanoparticles and surfactants

“…[5][6][7] Different subfractions have shown different density and viscoelasticity. 5,8,9 Early studies 10 have found that increasing the content of asphaltene can increase the viscosity of bitumen. Asphaltene has a high percentage of heteroatoms (N, O, S, and metals), and its self-aggregation effect will further increase the structural complexity of bitumen.…”