How is Methyl Methacrylate synthesized industrially?

Methyl methacrylate (MMA) is a key compound in the production of polymethyl methacrylate (PMMA), which is widely used in various industries, including automotive, construction, and electronics. The industrial synthesis of MMA involves several steps and chemical reactions, utilizing different raw materials and catalysts.

Raw Materials

The primary raw materials for the industrial synthesis of MMA are acetone, methanol, and hydrocyanic acid (HCN). These materials serve as the building blocks for the synthesis process. Acetone is derived from isopropyl alcohol, while methanol is typically obtained from natural gas or biomass sources. Hydrocyanic acid is produced via the Andrussow process, which involves the reaction of methane, ammonia, and oxygen at high temperatures.

Esterification

The first step in the synthesis of MMA is the esterification of methacrylic acid. Methacrylic acid is obtained by the catalytic oxidation of isobutylene, a process commonly known as the acetone cyanohydrin route. In the esterification reaction, methacrylic acid reacts with methanol in the presence of an acid catalyst, such as sulfuric acid or p-toluenesulfonic acid, to form methyl methacrylate and water.

Hydrocyanation

The next crucial step is the hydrocyanation of acetone to produce acetone cyanohydrin. This reaction involves the addition of hydrogen cyanide (HCN) across the double bond of acetone, yielding a cyanohydrin intermediate. This process is typically catalyzed by a base, such as sodium cyanide or a cyanide salt, under controlled conditions of temperature and pressure.

Cyanohydrin Deprotonation

After the formation of acetone cyanohydrin, the next step involves the deprotonation of the cyanohydrin group to generate a cyanide ion. This step is essential for the subsequent cyanide addition reaction. Deprotonation is usually achieved by treating the acetone cyanohydrin with a strong base, such as sodium hydroxide or potassium hydroxide, leading to the formation of the cyanide ion and the corresponding acetone anion.

Cyanide Addition

In the final step, the cyanide ion adds to the acetone anion, resulting in the formation of a β-keto nitrile intermediate. This reaction, known as the cyanide addition or cyanation reaction, is facilitated by the presence of a suitable catalyst, such as cuprous cyanide or a cyanide complex of a transition metal. The β-keto nitrile intermediate undergoes further chemical transformations to yield methyl methacrylate as the final product.

Conclusion

In conclusion, the industrial synthesis of methyl methacrylate involves a series of chemical reactions starting from readily available raw materials such as acetone, methanol, and hydrocyanic acid. These reactions are catalyzed by various acids, bases, and transition metal complexes to produce methyl methacrylate, a vital compound used in the manufacture of polymethyl methacrylate and other important industrial products. The optimization of reaction conditions and catalyst selection are crucial factors in ensuring high yields and efficient production of MMA Plant on an industrial scale.