Methyl methacrylate methylacetylene

Direct esterification of methacrylic acid with alcohols using sulfuric acid or other catalysts can be used to prepare methyl methacrylate (MMA) and other esters. Commercial routes for the direct preparation of MMA and some lower alkyl esters also exist. In the 1990s, researchers at Shell developed a direct route to MMA from propyne (methylacetylene), carbon monoxide, and methanol using a Pd(II) catalyst. The limited availability of propyne may slow the expansion of this highly efficient route to high purity MMA. Transesterification of MMA is often the preferred route for the preparation of other esters. 

Methylacetylene and CO introduced continuously at 130°/13 atm. into a stirring autoclave containing Ni-carbonyl, methacrylic acid and a little water as catalysts, and hydroquinone methyl methacrylate. Y 80.5%. S. Kunichika, Y. Sakakibara, and T. Nakamura, Bull. Chem. Soc. Japan 41, 390 (1968). 

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. 

Synthesis of Methyl Methacrylate Via Catalytic Carbonylation of Methylacetylene ... 

Production of this monomer amounts to 20 miUion tons/year. Traditionally, production was based on cheap and toxic raw materials acetone, a side product of the production of phenol, and hydrogen cyanide, which is highly toxic, a side product of the production of acrylonitrile. The process has now been abandoned because it produces 2.5 kg of ammonium hydrogen sulfate/kg of methyl methacrylate and is characterized by -factor 2.5. The catalytic process, introduced by chemists of the Shell Co., is based on the methoxycarbonylation of methy-lacetylene (propyne). Besides 100 % atom utihzation. this process is characterized by high chemical yield and selectivity, both over 99 % [12]. For the economy of any industrial process, the turnover is a particularly important technological parameter. Approximately 100,000 mols (ca. 4000 kg) of methylacetylene is... 

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