PEP Review 2010-12
Ethylene Oxide Production by Nippon Shokubai Process
Published: March 2010
This Review presents a techno-economic representation of an ethylene oxide (EO) production process based on technical data extracted from the patents of Nippon Shokubai ( Japan). For that reason we have titled the Review as “Ethylene Oxide Production by Nippon Shokubai Process.” It may be advised, however, that despite the best possible engineering judgment used in the conceptualization and designing of the process, a commercial Nippon EO plant may not (or may) have an exact construct as presented in the Review. We, nevertheless, strongly believe that the presented process design and economic evaluation thereof is a reasonably good picture of the actual process, and the two should be well within the marginal boundary of errors.
The process essentially consists of oxidizing high-purity ethylene gas with oxygen in the presence of an inert gas (methane); other gases like nitrogen, argon, carbon dioxide and ethane are generally also present in the process system. Oxidation conditions are: 446–518°F (230–270°C) at 15–25 atm. The alpha-alumina supported silver-cesium catalyst is of a proprietary design. Ethylene per-pass conversion is kept in the range 6–12%. Maximum selectivity to EO is about 83%. EO separation from the reactor effluent gases is executed by absorbing it in water, followed by stripping from the aqueous solution. Final purification is done in a battery of distillation columns. Carbon dioxide is the major byproduct which is eliminated from the process system via a Benfield® or CATACARB® unit. Overall EO yield is around 80% (per our designed process).
Our cost analysis is based upon a 320 thousand metric t/yr plant. We estimate that a plant of that capacity will require a capital investment of about $326.2 million at a U.S. Gulf Coast location. Product value (as defined in the text) is about $0.57/lb and the production cost is $0.45/lb. Cost details and relevant assumptions are given in the description part of the Review.