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Monsanto process

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Title: Monsanto process  
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Subject: Rhodium, Monsanto, Silicotungstic acid, Grignard reaction, Sandwich compound
Collection: Catalysis, Chemical Processes, Monsanto, Organometallic Chemistry, Rhodium
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Monsanto process

The Monsanto process is an industrial method for the manufacture of acetic acid by catalytic carbonylation of methanol.[1] The Monsanto process has largely been supplanted by the Cativa process, a similar iridium-based process developed by BP Chemicals Ltd which is more economical and environmentally friendly.

This process operates at a pressure of 30–60 atm and a temperature of 150–200 °C and gives a selectivity greater than 99%. It was developed in 1960 by the German chemical company, BASF, and improved by the Monsanto Company in 1966, which introduced a new catalyst system.[2]


  • Catalytic cycle 1
  • Tennessee Eastman acetic anhydride process 2
  • References 3
  • External Links 4

Catalytic cycle

The catalytic cycle of the Monsanto process

The methanol to methyl iodide and the hydrolysis of the acetyl iodide to acetic acid and hydrogen iodide.[4]

The reaction has been shown to be first-order with respect to methyl iodide and [Rh(CO)2I2]. Hence the oxidative addition of methyl iodide is proposed as rate-determining step.

Tennessee Eastman acetic anhydride process

Acetic anhydride is produced by carbonylation of methyl acetate in a process that is related to the Monsanto acetic acid synthesis.[5]

CH3CO2CH3 + CO → (CH3CO)2O

In this process lithium iodide converts methyl acetate to lithium acetate and methyl iodide, which in turn affords, through carbonylation, acetyl iodide. Acetyl iodide reacts with acetate salts or acetic acid to give the anhydride. Rhodium iodides and lithium salts are employed as catalysts. Because acetic anhydride is not stable in water, the conversion is conducted under anhydrous conditions in contrast to the Monsanto acetic acid synthesis.


  1. ^ Hosea Cheung, Robin S. Tanke, G. Paul Torrence "Acetic Acid" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a01_045
  2. ^
  3. ^ Hartwig, J. F. Organotransition Metal Chemistry, from Bonding to Catalysis; University Science Books: New York, 2010. ISBN 189138953X
  4. ^ Jones, J. H. (2000). Process for the Manufacture of Acetic Acid"TM"The Cativa (PDF).  
  5. ^ Zoeller, J. R.; Agreda, V. H.; Cook, S. L.; Lafferty, N. L.; Polichnowski, S. W.; Pond, D. M. (1992). "Eastman Chemical Company Acetic Anhydride Process".  

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