The Comonomer Production Technology (CPT) can be utilized to produce two valuable comonomers: butene-1 and hexene-1. These comonomers are commonly used in polyethylene and polypropylene production. Unlike other routes to butene-1 and hexene-1, which dimerize or trimerize polymer grade ethylene to produce the comonomer, CPT uses a much lower cost steam cracker or refinery based C4 raffinate as the feed. The C4 raffinate is converted to butene-1 by isomerization and fractionation. Hexene-1 is produced by metathesis of the C4 raffinate followed by isomerization of the hexene-3 produced by the metathesis reactions. Ethylene and propylene are co-produced in the metathesis reactions and recovered as valuable by-products. The CPT unit can be configured to produce only butene-1, only hexene-1 or a combination of both products. When both comonomers are produced and the capacity is below 20 kta, the unit can also be configured in a campaign mode where the isomerization and fractionation equipment is common for both comonomers. The campaign mode permits the cost effective production of smaller quantities of these comonomers which the dimerization or trimerization routes cannot achieve.
The Comonomer Production Technology (CPT) offers the most cost effective route for the production of butene-1 and hexene-1. This is the result of using a significantly lower cost feed, lower overall energy costs and lower investment. Specifically, the feed to CPT is C4 raffinate, which has a much lower value than polymer grade ethylene. In addition, while CPT consumes more energy than either dimerization or trimerization, when the energy costs of producing the polymer grade ethylene feed is considered, the overall energy consumption of CPT is lower. In addition, since CPT does not utilize polymer grade ethylene as a feed, the size of the associated steam cracker can be reduced, saving capital investment as well as operating costs. The investment of the CPT unit is also lower when butene-1 and hexene-1 are co-produced. CPT further produces ethylene and propylene as valuable co-products to the comonomers, further improving the relative operating margins.
CPT offers high reliability and lower maintenance costs, since both the dimerization and trimerization routes have fouling reactor loop reactor systems which must be shut down and cleaned, whereas CPT uses simple fixed bed reactor systems which produce no fouling components. The catalyst is simply regenerated from time to time.