Maleic anhydride
- (Z)- Butendisäureanhydrid
- Cis- Butendisäureanhydrid
- 2.5 furandione
White orthorhombic needles or scales with sharp penetrating odor
Fixed
0.93 g · cm -3
53 ° C.
202 ° C
20 Pa ( 20 ° C)
- Hydrolysis with water to form maleic acid
- Soluble in many organic solvents
Risk
0.41 mg · m -3, 0.1 ml · m-3
400 mg · kg -1 ( LD50, rat, oral)
-469.8 KJ / mol
Template: Infobox chemical / molecular formula search available
Maleic anhydride is the anhydride of maleic acid, an unsaturated dicarboxylic acid. It is an intermediate in the chemical industry.
Extraction / representation
Maleic anhydride is produced by partial oxidation of n-butane or the so called " raffinate II " by means of a vanadium-phosphorus oxide ( VPO ) catalyst. The " raffinate II " is a part of the produced during steam cracking C4 fraction and mainly consists of isomers of n- butenes and n -butane.
Older methods go in place of n- butane from the benzene. However, such methods are uneconomical due to the high and still rising benzene prices and to the applicable emission limit values for benzene. In addition (4 carbon atoms) is in the production of maleic anhydride according to the old process based on a third of the original molecule benzene (6 carbon atoms) is lost as carbon dioxide. The modern catalytic processes start from a 4 carbon molecule, and it is only attached oxygen and split off water. The 4 C main body of the molecule is maintained. Overall, the newer methods are therefore efficient material.
There is an analogy for the production of phthalic anhydride: while older method of naphthalene go out, use modern methods o -xylene.
Chemical Properties
Maleic anhydride hydrolyzed in warm water to maleic acid. In Diels -Alder reactions occurs as a reactive dienophile in appearance. As is typical of the unsaturated compounds is maleic anhydride easily addition reactions at the double bond.
Use
Maleic anhydride is an industrial intermediate. It is mainly used for the production of unsaturated polyester and for the synthesis of surfactants, insecticides, herbicides, fungicides, growth regulators (eg, maleic hydrazide ) and other chemical compounds. One part is reduced to 1,4-butanediol and tetrahydrofuran. With α -olefins can be MSA transpose to strictly alternating copolymers, which are of great importance as a lubricant.