Acetic anhydride by thermal deshydration of acetic acid

Chemical reactions

Ketene formation
CH3CO2H  =====> CH2=CO  + H2O  ( endo 32 kcl) catalyst : triethyl phosphate (1% /AcOH) , reaction temp 450 to 700°c

Ketene produced react on acetic acid
CH2=CO + CH3CO2H =====> Ac2O  (exo  25 kcal)  reac temperature 20/40°C

N.B. catalyst killed after Ketene formation  by adding ammonia to destroy catalyst


Example of a unit producing 1000 kg/h of acetic anhydride

Chemical yield based on acetic acid consumed : 92%
Mains by products :mixture of CO2/CO/C2H4/CH4  % ratio 14/46/23/17  , total which accouts for 3 to 5% of AcOH cracked


REACTION SECTION

reaction

DISTILLATION SECTION (main equipment )

this assumed usage of  crude acetic acid ,

distillation




Catalyst preparation (triethyl phosphate)

 REACTION :sodium ethoxyde on POCl3

catalyst prep.