Abstract

Methacrylic acid (MAA) and its derivatives exhibit a rich array of chemistries and have found wide use in commercial applications, especially as monomers for making various types of polymer products. The predominant manufacturing route to the two simplest methacrylates continues to be via the conversion of acetonecyanohydrin (ACH) in sulfuric acid to methacrylamide followed by either hydrolysis to MAA or esterification with methanol to give methyl methacrylate (MMA). Alternative routes have reached or are now approaching commercialization. These include processes based on either ethylene (C-2), propylene (C-3), methylacetylene (C-3), or isobutylene (C-4) feedstocks, as well as a separate ACH process which does not involve sulfuric acid. The later route, which starts with catalyzed hydration of ACH to hydroxyisobutyramide followed by esterification and dehydration steps to MMA, has an added benefit of recycling HCN as a raw material. The ethylene-based routes typically involve formaldehyde condensation on either a propionaldehyde or propionic acid intermediate. The isobutylene-based routes involve oxidation processes to reach the methacrylate backbone, often passing through methacrolein as an intermediate. The propylene-based routes typically involve isobutyric acid or isobutyraldehyde intermediates. The methylacetylene-based process appears to be the most selective overall, where a single reaction with carbon monoxide and methanol leads directly to MMA. All of the synthetic routes require various types of catalysts to promote the separate steps involved. In addition to providing more details on each of these processes, the following article also provides information on volumes, costs, health and safety for methacrylic acid and its derivatives.