(77a) Production of Dimethyl Carbonate Via Reactive Distillation Process

Dimethyl
Carbonate (DMC) is an environmentally benign and biodegradable product. Because
of its high oxygen content, DMC is an idea additive for gasoline to replace methyl
tert-butyl ether (MTBE). DMC has many applications in the synthesis of
polycarbonates, production of methyl isocyanate and as a replacement of halogenated
solvents.  It is extensively used as a methylating and carbonylating agent. Dimethyl
Carbonate has recently becomes an important solvent in the lithium ion battery
solutions and other electrochemical and coating sectors.

The
early commercial production of DMC via phosgenation of methanol has many draw
backs especially the toxicity of phosgene and is being phased out and replaced by
other methods. Among these new routes of producing DMC are the oxidative carbonylation
of methanol involving CO, transesterification using propylene carbonate or
ethylene carbonate to co-produce DMC and propylene glycol or ethylene glycol,
and methanolysis of urea.  The merits of each of the new routes of producing
DMC will be presented especially the systematic choice of entrainers in the extractive
distillation step to separate the DMC-Methanol azeotrope common to all the
three routes.