Roughly 95% of the feedstock costs of Ethylene Oxide (EO) are Ethylene costs. For every ton of EO, between 700 and 800 kg of Ethylene are required in modern plants. In older plants more Ethylene is required. The other important feedstock is oxygen.

About 60 years ago more than one ton of Ethylene was required to produce one ton of EO in the direct oxidation process. In the recent 60 years, the reduction of Ethylene consumption has mainly been caused by improvement of catalysts. About 20 years ago, the invention of Rhenium doped catalyst caused a reduction in Ethylene use of roughly 5%. Improvement in the EO manufacturing process resulted in another reduction of about 3%. During the recent years there are no important improvements in EO catalyst and process that give significant (>1%) reductions in Ethylene use.Theoretically there is still room for improvement. The theoretical minimum use of Ethylene is 637 kg for 1 ton of EO when 100% of the Ethylene is turned into EO and nothing is burned.

For a modern world scale EO plant producing 700 kton MEG or 500 kton EO per year (kton is 1000 ton), the Ethylene feedstock costs are between 350 and 400 mln $/a at an Ethylene price of $1000/ton. The difference between high and low feedstock costs is about 50 mln $/a and the low feedstock costs are, of course, targeted. The monetary numbers can be scaled with plant capacity and Ethylene price. For a 200 kton EO per year plant the difference between high and low feedstock costs is about 25 mln $/a at an Ethylene price of $1000/ton. At an Ethylene price of $1200/ton this difference is $30 mln/year between high and low cost of Ethylene.

These lowest costs can be achieved by:

1. The best catalyst at the economical optimal life of the catalyst,
2. Improved process conditions,
3. Improved operation.

Presently the best catalyst is often called High Selectivity (HS) catalyst. Using HS catalyst will reduce the feedstock costs by about 5% when compared to older types of catalysts that don’t use Rhenium doping. As long there is no strong competition in the market of HS catalysts, the costs of this HS catalyst will take away about 25 to 50% of the reduced costs of Ethylene, because it is sold at higher prices. HS catalyst has, additionally, a significantly shorter life in plants without improved process conditions.

Using the improved process conditions significantly reduces the costs of catalyst because it allows an increase of catalyst life of more than 100% and reduction of Ethylene consumption. For improved process conditions, investments of about $5-10 mln in the production plant are required. Normally these investments are recovered in 1 or 2 years.

Nearly all plants built after 2000 use HS catalyst with improved process conditions. Many older plants have started to use HS catalyst in the past 20 years. Most plants have improved the process conditions.