As might be expected, the main determinant of the cost is the price of ethylene. On a molar basis, purified EO and fiber-grade MEG sell for about the same price, but the price of a pound of EO is higher because of its lower molecular weight. We also evaluate variants in which all of the EO is converted to EG, with none of the EO purified for sales. Costs for making EG are higher in this case. In addition, we examine a variant in which all of the EO is purified for sales.
Modern plants use oxygen to oxidize ethylene.
Some older plants use air as the oxidant, but doing so is less efficient and costs are higher as a result. The report evaluates several variants of air processes. Other routes to EG have been proposed, but none is commercial. We evaluate routes from EO via ethylene carbonate, and from ethylene by direct hydroxylation with water and oxygen. Proposed routes from ethylene that we describe, but do not evaluate, include those via glycol esters and via 1,2-dichloroethane.