(532cs) Novel Kinetic Model for the Ethyl Acetate Synthesis By Direct Addition on a Silicotungstic Acid Catalyst.

Ethyl acetate is an important organic chemical used in glues, surface coatings, thinners, paints, inks, nail polisher removal products and as solvent in physical and chemical processes. Among other processes, the gas phase direct addition of ethylene and acetic acid, catalyzed by a solid acid such as silicotungstic acid, is the ethyl acetate synthesis route that was commercialized by BP Chemicals and Showa Denko in the ‘90s. Due to the acidic nature of the catalyst and presence of water in the acetic acid feedstock, a variety of by-products, mainly ethanol and diethyl ether, other esters, alcohols, ethers, aldehydes, ketones and hydrocarbons are formed as well.

A kinetic model for the direct addition reaction focusing on the main products was developed based on a simple mechanism in which six reacting components, i.e. ethylene, acetic acid, water, ethyl acetate, ethanol and diethyl ether, are converted into each other via five reactions (See figure). The non-idealities of the gas phase, due to presence of acetic acid, were captured by the Hayden and O’Connell equation of state. Reactions are described according to Langmuir-Hinshelwood and Eley-Rideal type mechanisms, where adjustable parameters were determined by regression to experimental data. The model was improved by accounting for the dehydration of silicotungstic acid by water and clustering of protons with ethanol.

The kinetic model can simulate the effects of operating conditions, i.e. space time, temperature, pressure and feed composition, on conversions and selectivities to the main products (ethyl acetate, ethanol and diethyl ether) well, which is essential to consider predictions trustworthy. The model can be implemented in state-of-the-art process modeling software packages to simulate the performance and identify better operating points for ethyl acetate production plants that apply the direct addition technology. Hence, the kinetic model is a viable tool to optimize the performance of the production plants.