Petroleum and Petrochemical Engineering
Core concepts
This domain covers crude oil characterisation and refining. Know crude assays, TBP and ASTM distillation curves, characterisation factors, API gravity, sulphur and metals content, and how these drive product slate. Master refinery units: atmospheric and vacuum distillation, catalytic cracking (FCC), hydrocracking, reforming, alkylation, isomerisation, hydrotreating, coking and visbreaking. Understand octane and cetane numbers, Reid vapour pressure, and product specifications (LPG, gasoline, kerosene, diesel, fuel oil). Petrochemical routes: steam cracking of naphtha to ethylene and propylene, aromatics (BTX) from reforming, and downstream polymers. Also cover natural gas processing (sweetening, dehydration, NGL recovery) and the role of hydrogen.
Traps
Do not confuse TBP with ASTM distillation - TBP is a true boiling-point curve at high reflux. Octane number relates to gasoline knock resistance; cetane to diesel ignition quality - higher is better in each, but they are different scales. FCC produces olefins and high-octane gasoline; reforming raises octane via aromatics and is hydrogen-producing. Hydrotreating removes sulphur and nitrogen, not carbon.
Worked rule of thumb
Characterisation factor (Watson) K = (T_B)^(1/3)/SG, where T_B is mean average boiling point in °R. Paraffinic crudes have K ≈ 12.5–13.0, naphthenic ≈ 11.0–12.0, aromatic < 11.5. This single number helps predict crude quality and processing behaviour.
Exam strategy
Link each unit operation to its feedstock, products and key specification; state the chemistry (cracking, reforming, alkylation) explicitly.