Methyl methacrylate, Lucite process

Alpha (2) A process for making methyl methacrylate, developed by Ineos Acrylics (now Lucite International) since 1990. Ethylene is carbonylated and methylated to produce methyl propionate, which is reacted with formaldehyde to produce methyl methacrylate. The first stage is homogeneously catalyzed by a palladium phosphine complex. The second stage is operated in the gas phase over a proprietary basic heterogeneous catalyst. Piloted by Davy Process Technology in 2002. The first commercial plant is to be built in Singapore, completion expected in early 2008. The second will be built in Texas by Mitsubishi Rayon, for completion in late 2009. 

Methyl methacrylate (MMA) is an important commodity since it is polymerized to give poly methylmethacrylate (PMMA), a strong, durable and transparent polymer sold under the trade-names Perspex and Plexiglas. Since the conventional routes to MMA involve either the reaction of acetone with HCN to give the cyanohydrin (which has environmental problems), or the oxidation of isobutene, alternative carbonylation routes to MMA are being developed. One of these is the Lucite Alpha process which is claimed to decrease production costs by ca. 40%. This first synthesizes methyl propionate by a methoxycarbonylation of ethylene (Equation 23), using a palladium catalyst with very high (99.8%) selectivity. In the second step, MMA is formed in 95% selectivity by the reaction of methyl propionate with formaldehyde (Equation 24). 

Methyl methacrylate monomer, which is polymerized in large quantities in commercial practice to give the clear resinous compositions sold as Lucite and Plexiglas, is prepared from acetone cyanohydrin by a process involving dehydration and hydrolysis of the nitrile to methacrylamide, followed by aicoholysis of the amide. 

Several other types of hydrocarboxylations and hydroesterifications have been conducted with rates and selectivity that are appropriate for the synthesis of fine chemicals and commodity chemicals. One target for hydroesterification has been methyl methacrylate, the monomer of polyfmethyl methacrylate), which is the polymer often called "acrylic". It is estimated that 2.1 million metric tons of methyl methacrylate was produced in 2005. Much of this material is produced from acetone cyanohydrin, but two alternative routes could involve catalytic carbonylation. The first route would involve the hydroesterification of methylacetylene, and this chemistry relates to the original route to methyl methacrylate by carbonylation of methylacetylene using nickel carbonyl as catalyst. The second route involves the sequence of ethylene hydoesterification, aldol addition of the resulting ester to formaldehyde, and dehydration. This sequence comprises Lucite s new "Alpha" process and is shown in Equation 17.33. The route to methyl methacrylate by hydrocarboxylation of ethylene produces water as the only byproduct. 

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