PEP Review 91-1-2
DIMETHYL CARBONATE BY VAPOR-PHASE OXIDATIVE CARBONYLATION
Published: June 1992
Ube Industries has announced a 3,000 t/yr (6.6 million lb/yr) dimethyl carbonate (DMC) plant scheduled to start up in 1992. This plant will employ a new low-pressure vapor-phase process based on carbon monoxide. Conventionally, DMC is produced by a two-phase phosgenation process or a relatively new liquid-phase oxidative carbonylation process. Ube has developed a vapor-phase oxidative carbonylation process to produce dimethyl oxalate (DMO) with DMC as the by-product using a Pd catalyst. Using a similar process configuration, DMC becomes the major product in the presence of a catalyst of PdCl2/CuCl2 on activated carbon.
In Ube's new process, carbon monoxide and methyl nitrite react to form DMC and nitric oxide, which together with methanol are then oxidized back to methyl nitrite and water in a separate nitrite regenerator. The total reaction is the oxidation of carbon monoxide and methanol to DMC and water with DMO being the major by-product. The reactor effluent is partially condensed to separate excess gaseous feedstocks from the liquid product, which is distilled to recover DMC.
In this review, we evaluate the vapor-phase oxidative carbonylation process for DMC production and compare its economics to those of the liquid-phase process. The capital investment of the vapor-phase process is estimated to be about 5% higher, mainly because of the costs of the refrigeration system, which is not required in the liquid-phase process. The consumptions of methanol, electricity, and refrigeration are also higher. However, the vapor-phase process could be economically competitive, depending on the amount and credit of DMO by-product.