Characterization of Precipitated Asphaltenes and Deasphalted Oils of the Medium Crude Oil–CO<sub>2</sub> and Medium Crude Oil–<i>n</i>-Pentane Systems
Bibliographic record
Abstract
In this paper, asphaltenes are precipitated from a medium crude oil using a non-hydrocarbon precipitant (CO 2 ) or a hydrocarbon precipitant ( n -pentane). First, the onset pressure of asphaltene precipitation from the medium crude oil–CO 2 system is determined using a visual high-pressure saturation cell. Second, the morphology of CO 2 -precipitated asphaltenes (CO 2 –asphaltenes) is examined and compared to that of n -pentane-precipitated asphaltenes (C 5 –asphaltenes). Third, the precipitated asphaltenes and deasphalted oils (i.e., maltenes) of the medium crude oil–CO 2 and medium crude oil– n -pentane systems are characterized by applying a variety of analytical techniques, such as the density and molecular-weight measurements, nuclear magnetic resonance (NMR) spectrometry, Fourier transform infrared (FTIR) spectrometry, and simulated distillation. It is found that the onset pressure of asphaltene precipitation from the medium crude oil–CO 2 system is equal to 3.8 MPa. The yields and physicochemical properties of the precipitated asphaltenes and deasphalted oils strongly depend upon the specific precipitant used. CO 2 –asphaltenes are small particles dispersed in the co-precipitated resins, whereas C 5 –asphaltenes are solid-like dark brown and brittle powders. In addition, CO 2 –asphaltenes have a lower molecular weight, low aromaticity, and shorter aliphatic side chains than C 5 –asphaltenes. On the other hand, CO 2 -deasphalted oil (CO 2 –maltenes) has a higher molecular weight, high aromaticity, and longer aliphatic side chains than n -pentane-deasphalted oil (C 5 –maltenes). The compositional analysis results of CO 2 –maltenes and C 5 –maltenes indicate that the carbon numbers of most precipitated asphaltenes are larger than C 50 and that CO 2 –maltenes are heavier than C 5 –maltenes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".