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Maleic anhydride

Maleic anhydride
Maleic anhydride
Maleic anhydride-3d.png
Sample of Maleic anhydride.jpg
Names
Preferred IUPAC name
Furan-2,5-dione
Other names
Maleic anhydride
cis-Butenedioic anhydride
2,5-Furanedione
Maleic acid anhydride
Toxilic anhydride
Identifiers
108-31-6 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:474859 N
ChEMBL ChEMBL374159 YesY
ChemSpider 7635 YesY
ECHA InfoCard 100.003.247
EC Number 203-571-6
PubChem 7923
RTECS number UE5950000
UNII V5877ZJZ25 YesY
Properties
C4H2O3
Molar mass 98.06 g·mol−1
Appearance White crystals or needles
Odor irritating, choking
Density 1.48 g/cm3
Melting point 52.8 °C (127.0 °F; 325.9 K)
Boiling point 202 °C (396 °F; 475 K)
Reacts
Vapor pressure 0.2 mmHg (20°C)
-35.8·10−6 cm3/mol
Hazards
Safety data sheet MSDS at J. T. Baker
Corrosive (C)
R-phrases R22, R34, R42/43
S-phrases (S2), S22, S26,
S36/37/39, S45
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 102 °C (216 °F; 375 K)
Explosive limits 1.4%-7.1%
Lethal dose or concentration (LD, LC):
LD50 (median dose)
465 mg/kg (oral, mouse)
850 mg/kg (oral, rat)
875 mg/kg (oral, rabbit)
390 mg/kg (oral, guinea pig)
400 mg/kg (oral, rat)
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 1 mg/m3 (0.25 ppm)
REL (Recommended)
TWA 1 mg/m3 (0.25 ppm)
IDLH (Immediate danger)
10 mg/m3
Related compounds
Succinic anhydride
Related compounds
Maleic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Maleic anhydride is an organic compound with the formula C2H2(CO)2O. It is the acid anhydride of maleic acid. It is a colorless or white solid with an acrid odor. It is produced industrially on a large scale for applications in coatings and polymers.

Maleic anhydride is produced by vapor-phase oxidation of n-butane. The overall process converts the methyl groups to carboxylate and dehydrogenates the backbone. The selectivity of the process reflects the robustness of maleic anhydride, with its conjugated double-bond system. Traditionally maleic anhydride was produced by the oxidation of benzene or other aromatic compounds. As of 2006, only a few smaller plants continue to use benzene.

In both cases, benzene and butane are fed into a stream of hot air, and the mixture is passed through a catalyst bed at high temperature. The ratio of air to hydrocarbon is controlled to prevent the mixture from igniting. Vanadium pentoxide and molybdenum trioxide are the catalysts used for the benzene route, whereas vanadium phosphate is used for the butane route:

The main competing process entails full combustion of the butane, a conversion that is twice as exothermic as the partial oxidation.

The traditional method using benzene became uneconomical due to the high and still rising benzene prices and by complying the regulations of benzene emissions. In addition, in the production of maleic anhydride (4 C-atoms) a third of the original carbon atoms is lost as carbon dioxide when using benzene (6 carbon atoms). The modern catalytic processes start from a 4-carbon molecule and only attaches oxygen and removes water; the 4-C-base body of the molecule remains intact. Overall, the newer method is therefore more material efficient.


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