1-Hexene Production from Ethylene

The process under analysis comprises three major sections: (1) Reaction; (2) Chemicals Separation; and (3) Purification.

Reaction. A recycle cyclohexane stream from the Solvent Recovery Column is mixed with the catalyst system solution and then fed a trimerization reactor. An ethylene recycle stream is mixed with the ethylene feed and they are simultaneously fed to the reactor, but in a counter-current fashion. In order to remove the reaction heat from the medium, it is maintained an external circulation loop passing through heat exchangers against boiler feed water, generating low pressure steam. The process achieves an ethylene conversion of about 70 wt%.

Chemicals Separation. The reactor output stream is mixed, in a static mixer, with 2-ethyl-1-hexanol, which deactivates the catalyst in the reaction medium, to prevent the production of by-products during the purification section. Then the deactivated process stream is flashed in three stages, at decreasing pressures and increasing temperatures. The recovered vapor phases from each stage are mixed and directed to the Ethylene Recovery Column. As a result, a relatively pure ethylene stream is recovered as the top product and most of it is recycled to reaction. The smaller part is purged from the process to avoid the buildup of light contaminants in the process.

Purification. The product rich stream is fed to another three distillation columns in order to separate heavy olefins by-products produced via undesirable side reactions and lighter contaminants, which are exported to the nearby petrochemical complex to be used as fuel. A cyclohexane rich stream is also recovered and split into two fractions, one fraction is directed to the reaction area and the second fraction is sent to the Ethylene Recovery Column. The final product stream, with a purity greater than 99 wt%, is produced.