Published September 1998
Eastman Chemical Company, in collaboration with Research Triangle Institute and Bechtel Engineering, is developing a syngas-based route for the production of methyl methacrylate (MMA). The new route is claimed by Eastman to be environmentally more benign than the currently dominant acetone-cyanohydrin route, which involves handling highly toxic materials such as hydrogen cyanide and dealing with large amounts of acidic liquors containing ammonium bisulfate and sulfuric acid. Another noteworthy feature of the new process is that it is primarily syngas-based, as all the intermediate chemicals used in the process, such as propionic acid (PA), formaldehyde (FA), and methanol, are derivatives of syngas. Thus the process can be integrated with a syngas plant producing methanol, and all the intermediate chemicals required in MMA production can be indigenously produced and captively used. In-house production of the necessary intermediates offers economic benefits too. Natural gas (for syngas) and ethylene (C2H4) are the only materials that need to be imported across the fence.
Eastman's route to MMA consists of three basic stages. In the first stage, C2H4 is carbonylated with CO in the presence of water to form PA. The reaction takes place at 170-200�C (338-392�F) and 50-55 atm in a dilute aqueous PA solution in the presence of a halide-promoted molybdenum catalyst. In the second stage, PA reacts with FA at 300�C (572�F) and 2 atm in the gaseous phase to produce methacrylic acid (MAA); a silica-supported, niobium-based catalyst is used. In the third and final stage, MAA is esterified with methanol to give MMA.
In this review, we present an evaluation of the Eastman syngas-based process for MMA, based on producing 250 million lb/yr (113,400 t/yr) at a 0.9 stream factor at a U.S. Gulf Coast location. Our evaluation includes a detailed presentation of the process economics.