Process Chemistry

• Process was an oxy-Claisen rearrangement of an orthoacetate derived from allyl alcohol.
• Desired product was the ethyl ester.
• The allyl ester was formed as an unwanted by-product
• Lab results gave both esters in equal proportions and at only 50% yield

Customer Requirements

• Economic, high conversion process with high selectivity towards the required ester
• Need to reduce the excess of the allyl alcohol

Approach

• Optimisation required an alternative to conventional approach (serious issues of reaction time and complexity)
• Ortho ester exchange kinetics and elimination / rearrangement kinetics were obtained using a combination of analytical and laboratory experiments
• Reaction rate constants at different temperatures were also calculated

Outputs

• Simulation predicted that semi-batch operation was needed with low allyl alcohol feed rates & low reflux ratios
• Simulation indicated that temperatures above 130°C were needed
• Simulations were validated by 20 experiments in 15 days
• Study yielded parameters that increased the overall yield from 50 to 95%
• Long term future of the process was therefore assured

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