Lucite process

Palladium catalysts with simple monodentate phosphine ligands (e.g. PPh3) can catalyze the methoxycarbonylation of ethylene. However, the Lucite process employs a bulky diphosphine, 1,2-( Bu2PCH2)2CgH4, and is highly active and selective under quite mild conditions (10 bar/80°C). Two alternative catalytic cycles are possible, based either upon a palladium hydride or a palladium methoxide complex (Figure 9), and mechanistic and spectroscopic studies indicate that the hydride cycle is dominant. The alkene and CO insertion steps are the same as those in the Pd-catalyzed co-polymerisation of CO and alkenes to polyketones (Section 4.4). 

Alpha process C2H4, CO, CH3OH, H2CO Catalytic carbonylation of ethylene to Lucite (to become... 

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). 

Polymers are divided into two classes natural and synthetic. Important biological molecules such as proteins, nucleic acids, and polysaccharides (starches and the cellulose in wood and cotton) are natural polymers. Natural rubber and natural fibers such as silk and wool are also natural polymers. Familiar examples of synthetic polymers include plastics such as polyethylene. Teflon, and Lucite (Plexiglas) and synthetic fibers such as nylon, Orion, and Dacron. In this section we will describe some processes by which polymers are formed from organic compounds. 

Two examples are highlighted below where precious metal catalysts are used to produce fine chemicals on an industrial scale via carbon-carbon bond forming reactions. The first (a) is rhodium-catalysed hydroformylation in the oxo-process , which is a well established industrial process. The second (b) highlights a new process developed by Lucite involving a palladium-catalysed methoxy-carbonyla-tion. Many of the points mentioned above in this article are illustrated in the examples, with efficient recycle of catalyst (precious metal) and the extra cost of ligands being justified by the costs savings of the novel chemistry. 

This is a new technology developed by Lucite (formerly Ineous, formerly ICI).[8] It involves a two-step process a liquid phase methoxy-carbonylation followed by a gas phase condensation. 

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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