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Home Vinyl Acetate Monomer (VAM)

Vinyl acetate

Vinyl acetate is an organic compound with the formula CH3COOCH=CH2. A colorless liquid with a pungent odor, it is the precursor to polyvinyl acetate, an important polymer in industry.

Production

The worldwide production capacity was estimated at 6,154,000 tonnes/annum in 2007, with most capacity concentrated in the United States (1,585,000 all in Texas), China (1,261,000), Japan (725,000) and Taiwan (650,000). The average list price for 2008 was $1600/tonne. Celanese is the largest producer (ca 25% of the worldwide capacity), while other significant producers include China Petrochemical Corporation (7%), Chang Chun Group (6%) and LyondellBasell (5%).

Preparation

The major industrial route involves the reaction of ethylene and acetic acid with oxygen in the presence of a palladium catalyst.

Ethylene + acetic acid + 1/2 O2 → Vinyl acetate + H2O

But byproducts are also generated:

Ethylene + 3 O2 → 2 CO2 + 2 H2O

Vinyl acetate is also prepared by the gas-phase addition of acetic acid to acetylene.

Polymerization

It can be polymerized, either by itself to make polyvinyl acetate or with other monomers to prepare copolymers such as ethylene-vinyl acetate (EVA), vinyl acetate-acrylic acid (VA/AA) and polyvinyl chloride acetate (PVCA). Due to the instability of the radical, attempts to control the polymerization via most 'living/controlled' radical processes have proved problematic. However, RAFT (or more specifically MADIX) polymerization offers a convenient method of controlling the synthesis of PVA by the addition of a xanthate chain transfer agent.

Other reactions

Vinyl acetate undergoes many of the reactions anticipated for an alkene and an ester. Bromine adds to give the dibromide. Hydrogen halides add to give 1-haloethyl acetates, which cannot be generate by other methods because of the non-availability of the corresponding halo-alcohols. Acetic acid adds in the presence of palladium catalysts to give ethylidene diacetate, CH3CH(OAc)2. It undergoes transesterification with a variety of carboxylic acids. The alkene also undergoes Diels-Alder and 2+2 cycloadditions.