Project ForgeLiquid-phase isomerization of o-xylene to p-xylene over a zeolite catalyst in a CSTR was studied at 3 temperatures × 3 stirring speeds (1000/2000/3000 rpm). Rates (mol/L·s): 500K: 0.020,0.025,0.025; 600K: 0.037,0.047,0.047; 700K: 0.069,0.078,0.086. The operating condition where the rate is NOT controlled by external mass transfer resistance is
- T=500K; rpm=3000
- BT=600K; rpm=1000
- CT=700K; rpm=1000
- DT=700K; rpm=2000
Explanation
External mass transfer resistance is absent once the rate plateaus (becomes insensitive to further increases in stirring speed). At 500K, rate is unchanged between 2000 and 3000 rpm (0.025 both) — plateaued. At 700K, the rate is still rising even at 3000 rpm — still mass-transfer limited at every tested speed.
Source: GATE CH 2018 (2018)
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