Heat Integrated Reactive and Extractive Distillation for the Synthesis of Carbonates In Emerging Markets

Carbonates are generally environmentally benign and biodegradable products. In particular, dimethyl carbonate (DMC) because of its high oxygen content, 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.  Carbonates are also extensively used as a methylating and carbonylating agent. Recently carbonates have become very important solvents in the emerging markets like lithium ion battery solutions and other electrochemical and coating sectors.

The emphasis of this paper is on production of DMC in which its early commercial production was via phosgenation of methanol. The phosgene route 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. The main objective of this project is energy savings which is being explored by using heat integrated reactive and extractive distillation techniques as will be presented.