Heterogeneous Approach to the Catalytic Cracking of Vacuum Gas Oil
Bibliographic record
Abstract
This study examines the roles of intracrystallite diffusion and reaction phenomena during the catalytic cracking of vacuum gas oil. Catalytic cracking experiments on FCC-type catalysts were performed in a fluidized bench-scale CREC riser simulator. This reactor was operated under close-to-industrial FCC conditions in terms of temperature, reaction time, partial pressures of reactant and products, and catalyst-to-oil ratio. The activity and selectivity of two USY zeolite catalysts, with very similar properties but varying zeolite crystallite sizes, were determined. A five-lump kinetic model describing the catalytic cracking of gas oil to light cycle oil, gasoline, light gases, and coke and accounting for diffusional constraints experienced by hydrocarbons while evolving in the zeolite pore network was considered. The results show that the catalyst with the smaller crystallites provided higher activity and selectivity toward desirable intermediate products (gasoline with low aromatics) and lower selectivity for terminal products (coke), indicating that diffusion plays a significant role in catalytic cracking. Diffusivity and kinetic parameters, including modified Thiele modulus and effectiveness factor, were established to determine the effects of crystallite size and temperature on the operating regime of the catalyst. It was found that, in the 510−530 °C range, the overall cracking rate is controlled by the highly temperature-sensitive intracrystalline gas oil transport, whereas in the 550−570 °C range, the overall cracking rate is dominated by a mildly temperature-sensitive intrinsic cracking rate.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".