What Is Maleic Anhydride?
Maleic anhydride is a white crystalline substance produced by air oxidation of benzene or n-butane. It serves as a raw material for fumaric acid, which is a food additive, and is also used in unsaturated polyester resins, paint resins, and as a resin modifier.
Maleic anhydride, an acid anhydride, hydrolyzes readily in water to form maleic acid. It and its isomer fumaric acid are precursors for organic acids like malic acid and succinic acid.
This chemical is considered hazardous according to the 2012 OSHA Hazard Communication Standard. It is a skin and respiratory irritant and sensitizer, requiring careful handling and appropriate protective equipment.
Maleic Anhydride Manufacturing Process and Uses
Maleic anhydride is produced via the air oxidation of benzene and n-butane, commonly using vanadium oxide as a catalyst. Its applications include raw material for fumaric acid and unsaturated polyester resins and as a modifier for resins, paints, inks, and glue for coating paper surfaces.
Additionally, it modifies resins like polypropylene, used in fiberglass-reinforced plastics for various applications including housing, automotive, marine, and chemical equipment.
Examples of Reactions Using Maleic Anhydride
Maleic anhydride, a dehydrated and condensed form of two carboxylic acids, reacts with water to form maleic acid, which can isomerize to fumaric acid. At 160°C, maleic acid dehydrates back to maleic anhydride. It’s also a raw material for synthesizing malic and succinic acids, with industrial production of malic acid typically involving the hydration of fumaric acid under pressure.
Safety of Maleic Anhydride and Regulations
As a white crystal that sublimates with a pungent odor, maleic anhydride is not classified as hazardous under fire regulations due to its solid state. However, it is flammable with a flash point of 102°C. Proper storage and handling are crucial due to its hazardous nature.