Integrative Investigation of Low-Temperature Oxidation Characteristics and Mechanisms of Heavy Crude Oil

Zhao, Shuai; Pu, Wanfen; Varfolomeev, Mikhail A.; Yuan, Chengdong; Родионов, А. А.

doi:10.1021/acs.iecr.9b03346

Cited by 28 publications

(10 citation statements)

References 44 publications

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“…This should not be construed as absence of conversion at ambient temperature or indefinite stability of the asphaltenes in solution. There is ample evidence to indicate that oxidation of heavy oil and asphaltenes will proceed at ambient temperature over time (oxidative weathering), and this process can be accelerated by increasing the partial pressure without resorting to an increase in temperature …”

Section: Resultsmentioning

confidence: 99%

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Origin of Free Radical Persistence in Asphaltenes: Cage Effect and Steric Protection

2020

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Heavier petroleum fractions contain persistent free radicals, and the highest concentration of persistent free radicals is usually found in asphaltenes. The origin of free radical persistence was studied. The potential influence of exposure to air, free radical caging, and steric protection was evaluated. The free radical content of asphaltenes diluted in toluene remained constant to within 5% over a period of 465 h under both nitrogen and air atmospheres. The persistent free radicals were accessible for reaction in dilute solution. Caging of free radicals due to high viscosity could not explain the observations. Caging of free radicals due to molecular-level aggregation was possible, but explaining all of the observations in terms of the cage effect became tenuous. The asphaltenes appeared unencumbered by steric constraints compared to 9,10-dihydroanthracene during hydrogen transfer reactions, which made it unlikely that steric protection was a major contributor to the persistence of free radicals. The asphaltenes were reactive at 250 °C, both for self-reaction and for conversion of various model molecules (1,2-dihydronaphthalene, α-methylstyrene, 2,4,6-trimethylstyrene, 1,1-diphenylethylene, trans-1,2-diphenylethylene, triphenylethylene, tetraphenylethylene, and 9,10-dihydroanthracene). An alternative explanation for the origin of free radical persistence was forwarded. It was considered unlikely that individual free radical species could remain as persistent free radicals over geologic time but also be reactive. The observed persistence of free radicals could be explained in terms of a dynamic “equilibrium” of free radical pairs, which is a self-stabilizing process that gives the impression of free radical persistence. Dynamic formation and destruction of free radicals through addition and decomposition reactions of radical pairs average out on the macroscopic scale to create the impression of persistent free radicals. Any individual species does not remain persistent beyond what one would expect from a reactive persistent free radical.

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Section: Resultsmentioning

confidence: 99%

“…There is ample evidence to indicate that oxidation of heavy oil and asphaltenes will proceed at ambient temperature over time (oxidative weathering), and this process can be accelerated by increasing the partial pressure without resorting to an increase in temperature. 22 3.2. Reaction of Asphaltenes and 1,2-Dihydronaphthalene.…”

Section: Energy and Fuelsmentioning

confidence: 99%

Origin of Free Radical Persistence in Asphaltenes: Cage Effect and Steric Protection

2020

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“…To further understand the LTO reaction pathways of heavy oil, Zhao et al investigated alterations of gaseous product compositions and oxidized oil properties caused by LTO. The results indicate that LTO reactions were carried out at lower levels as the oxidation temperatures lowered, which was demonstrated by a lower H/C and higher content of high molecules with polycyclic aromatic hydrocarbons [25]. Zhao et al characterized the compositional changes of the heavy oil due to LTO through gas chromatograph-mass spectroscopy and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry; the results showed that the condensation of aromatics, as well as aromatization and condensation of other compounds, were intensified below 200 • C, and that chain saturated aliphatic, monocyclic, bicyclic, and tricyclic naphthenic acids were the main acidic components in the oxidized oils [26].…”

Section: Introductionmentioning

confidence: 91%

“…; then, static isothermal oxidation experiments were carried out for 3 days in a muffle furnace at specific temperatures (50, 100, 150, 200, 250, 300, and 350 • C) and a constant pressure of 2.98 MPa (the original pressure of the FC oilfields). After isothermal oxidation reactions of FC extra-heavy oil at various experiment temperatures, oxidized oils and gaseous products were collected [25,27].…”

Section: Static Isothermal Oxidation Experiments and Physical Propert...mentioning

confidence: 99%

Combustion Behavior and Kinetics Analysis of Isothermal Oxidized Oils from Fengcheng Extra-Heavy Oil

Wang

et al. 2021

Energies

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The low-temperature oxidation (LTO) of heavy oil is of great significance for the combustion front stability, which directly influences the efficiency and safety of in-situ combustion (ISC). To provide feasible heating by artificial ignition before the implementation of ISC in the Xinjiang Fengcheng (FC) oilfields, this paper investigates the oxidation behavior of FC extra-heavy oil and its isothermal oxidized oils. Firstly, FC extra-heavy oil was subjected to isothermal oxidation experiments conducted utilizing an oxidation reactor, and the physical properties of the gaseous products and oxidized oils were analyzed. The combustion behavior of the FC extra-heavy oil and oxidized oils was then studied by non-isothermal thermogravimetry and differential scanning calorimetry. Subsequently, the Friedman and Ozawa–Flynn–Wall methods were adopted to perform kinetic analysis. Oxygen consumption was always greater than the production of CO and CO2, so oxygen addition reactions were the main pathway in heavy oil LTO. H/C decreased to 8.31% from 20.94% when the oxidation temperature rose from 50 °C to 150 °C, which deepened the oxidation degree. The density and viscosity of 200 °C to 350 °C oxidized oils increased at a slower rate, which may be related to the LTO heat effect. The change law of temperature interval, peak temperature, and mass loss of the oxidized oils had a good correlation with the static oxidation temperature. Compared with other oxidized oils, the peak heat flow and enthalpy of 350 °C oxidized oil increased significantly with high-temperature combustion, and were 42.4 mW/mg and 17.77 kJ/mol, respectively. The activation energy of 350 °C oxidized oil began to decrease obviously around a conversion rate of 0.4, which indicates that it was beneficial to coke deposition with stronger activity. Finally, we came up with LTO reaction mechanisms and put forward a reasonable preheating temperature for the application of ISC in FC oilfields.

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“…With the decrease of the crude oil temperature during pipelining, the wax becomes less soluble and crystallizes out of the crude oil. The precipitated wax crystals accompanying the aggregated asphaltene particles change the crude oils from simple Newtonian fluids to complex non-Newtonian fluids, and even induce gelation [2]. Therefore, crude oils containing high asphaltene and wax contents often have a high pour point and high viscosity, which is adverse for the safety and economic operation of crude oil transportation [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Asphaltene Inhibition and Flow Improvement of Crude Oil with a High Content of Asphaltene and Wax by Polymers Bearing Ultra-Long Side Chain

Lu²,

Niu³

et al. 2021

Energies

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A high content of asphaltene and wax in crude oil leads to difficulties in the recovery and transportation of crude oil due to the precipitation of asphaltenes and the deposition of waxes. Comb-like polymers were found to be capable of inhibiting the aggregation of asphaltenes and crystallization of waxes. In this work, comb-like bipolymers of α-olefins/ultra-long chain (C18, C22 and C28) alkyl acrylate were synthesized and characterized by FT-IR and 1H NMR spectra. The results show that, for a model oil containing asphaltene, the initial precipitation point (IPP) of asphaltene was prolonged by UV, and the asphaltene particle size was reduced after adding the biopolymers, as revealed by dynamitic light scattering (DLS). The bipolymer containing the longer alkyl chain had a better asphaltene inhibition effect. However, DSC and rheological results show that the wax appearance temperature (WAT) of the typical high asphaltene and high wax content of crude oil was obviously reduced by adding bipolymers with shorter alkyl chains. The bipolymer (TDA2024-22) with a mediate alkyl chain (C22) reduced the viscosity and thixotropy of the crude oil by a much larger margin than others. Compared with the previously synthesized bipolymer with phenyl pendant (PDV-A-18), TDA2024-22 exhibited a better performance. Therefore, bipolymers with appropriate alkyl side chains can act as not only the asphaltene inhibitors but also wax inhibitors for high asphaltene and wax content of crude oil, which has great potential applications in the oil fields.

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Integrative Investigation of Low-Temperature Oxidation Characteristics and Mechanisms of Heavy Crude Oil

Cited by 28 publications

References 44 publications

Origin of Free Radical Persistence in Asphaltenes: Cage Effect and Steric Protection

Origin of Free Radical Persistence in Asphaltenes: Cage Effect and Steric Protection

Combustion Behavior and Kinetics Analysis of Isothermal Oxidized Oils from Fengcheng Extra-Heavy Oil

Asphaltene Inhibition and Flow Improvement of Crude Oil with a High Content of Asphaltene and Wax by Polymers Bearing Ultra-Long Side Chain

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