Typical FCC reactor conditions: Industrial catalytic cracking (e.g., FCC) commonly operates near which pressure–temperature combination?
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A2 atm & 500°C
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B10 atm & 500°C
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C30 atm & 200°C
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D50 atm & 750°C
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E1 atm & 350°C
Answer
Correct Answer: 2 atm & 500°C
Explanation
Introduction:Catalytic cracking (especially FCC) converts heavy gas oils to gasoline and lighter products using a solid acid catalyst at elevated temperature and modest pressure. Choosing realistic operating ranges helps distinguish FCC from hydrocracking and thermal processes.
Given Data / Assumptions:
- Atmospheric to a few atmospheres pressure in FCC riser/regen loop.
- Reaction temperatures roughly around 480–540°C in the riser.
Concept / Approach:FCC employs short contact times at high temperature and low–moderate pressure to favour gasoline-range products while minimising overcracking and coking. Pressures above ~3–4 atm are unusual in classic FCC risers, and temperatures near 200°C or 750°C are out of range for the cracking step.
Step-by-Step Solution:
Eliminate unrealistic pairs (too high P, too low/high T).Recognise typical FCC regime ~2 atm and ~500°C.Select “2 atm & 500°C.”Verification / Alternative check:Process descriptions consistently cite ~1–3 atm riser pressure and ~500°C reactor outlet temperatures.
Why Other Options Are Wrong:
- 10 atm at 500°C: More characteristic of hydroprocessing with hydrogen, not FCC.
- 30 atm & 200°C / 50 atm & 750°C: Out of FCC envelope.
- 1 atm & 350°C: Temperature too low for effective catalytic cracking.
Common Pitfalls:Mixing FCC with hydrocracking conditions where high H2 pressure is used.
Final Answer:2 atm & 500°C