The Ethylene Dimerization process dimerizes ethylene to produce butene-2 and butene-1. The catalyst is formulated to offer a high selectivity to butene-2. The butene-2 to butene-1 product ratio is about nine to one. As such, it is ideally suited to applications where ethylene is dimerized as feed to an Olefins Conversion Unit, thereby permitting the conversion of ethylene to propylene. The Ethylene Dimerization process, when combined with Olefins Conversion Technology (OCT), provides the only commercial route to convert ethylene to propylene. When combined with ethane cracking technology, it is the only commercial route to produce commercially viable quantities of PG propylene from ethane feed. Since a portion of the ethylene dimerizes to butene-1, it may be recovered and used as a comonomer in a polypropylene or polyethylene facility, thus potentially eliminating the need for a separate ethylene dimerization unit to produce the comonomer. Ethylene dimerization and OCT can also be combined with a liquid feed steam cracker or an MTO unit to produce any desired propylene to ethylene product ratio up to 100% propylene. The Ethylene Dimerization process can also be used to convert ethylene into alkylate using ethylene recovered from refinery off-gas streams.
The Ethylene Dimerization process is the only commercially demonstrated dimerization technology to produce butene-2 and butene-1 allowing the process integrations with ethylene plants and MTO units outlined above. It is a simple, low investment cost process consisting of only a loop reactor and catalyst quench section. When butene-1 is recovered, a simple fractionation sequence is also provided. It offers a high selectivity to butene, thereby making conversion of ethylene to propylene economically viable and attractive whenever the propylene to ethylene price ratio is above 1.08. The low investment cost permits the best flexibility for the operation of the unit when the propylene to ethylene price ratio is above 1.08 and suspension of operation when it drops below that value—resulting in the best operating margin from the adjoining ethylene plant. Capacity can range from 40 kta to 600 kta or above. The catalyst is designed to minimize oligomerization which means long cycle times for the loop reactors and minimum maintenance costs. When used in conjunction with ethylene recovered from refinery off-gas streams, it permits upgrading the ethylene from fuel gas value to alkylate value.