Stoessel criticality diagram — cooling-failure assessment of a semi-batch acylation
Thermal process-safety criticality diagram placing process temperature, MTSR, MTT and T_D24 on one temperature scale to classify a semi-batch reaction as Stoessel class 4, the assessment a reaction-hazard or process-safety chemist files from calorimetry data before scaling a batch reaction up.
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"text": "Stoessel criticality diagram — semi-batch acylation in toluene, 6.3 m³ reactor",
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"Criticality class 4: T_p < MTT < T_D24 < MTSR — on loss of cooling the batch reaches boiling before decomposition,",
"so evaporative cooling is a barrier ONLY if the condenser and vent are sized for the full boil-off rate."
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"T": 60,
"val": "60 °C",
"note": "process set point\njacket cooled",
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{
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"T": 111,
"val": "111 °C",
"note": "reaction mass b.p.\nat 1.013 bar",
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"code": "T_D24",
"T": 125,
"val": "125 °C",
"note": "TMR_ad = 24 h\nadiabatic calorimetry",
"order": 3,
"role": "Decomposition"
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{
"code": "MTSR",
"T": 139,
"val": "139 °C",
"note": "T_p + 0.45 × ΔT_ad\nΔT_ad,rx = 175 K",
"order": 4,
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"t": "Dashed lines: MTT (boiling, 111 °C) and T_D24 (125 °C).\nMTSR = 139 °C sits above both, so the cooling-failure\npath is boil-off first, then decomposition — class 4."
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