To produce high-purity hexene-1 from a mixed C4 stream using Lummus’ comonomer production technology (CPT). The feedstock can contain any amount of butene-1, butene-2 and butane.
While the following description uses raffinate-2 feed, steam-cracker raw C4s or raffinate-1 can be used with additional steps for butadiene hydrogenation or isobutene removal before the CPT unit.
In the butene isomerization section (1), raffinate-2 feed from OSBL, mixed with butene recycle from the butene distillation section, is vaporized, preheated and fed to the butene isomerization reactor where butene-2 is isomerized to butene-1 over a fixed bed of proprietary isomerization catalyst. Reactor effluent is cooled and flows to the butene distillation section (2) where it is separated in a butene fractionator into butene-1 for feed to metathesis and recycle butene-2.
The butene-1 is mixed with butene recycle from the autometathesis recovery section and is vaporized, preheated and fed to the autometathesis reactor (3) where butene-1 reacts with itself to form hexene-3 and ethylene over a fixed bed of proprietary metathesis catalyst. Some propylene and pentene are also formed from the reaction of butene-2 in the butene-1 feed. Reactor effluent is cooled and flows to the autometathesis recovery section (4), where two fractionation columns separate it into a hexene-3 product that flows to the hexene isomerization unit (5), an ethylene/propylene mix, and butene-1 that is recycled to the butene autometathesis section. A purge of butenes/C5s is sent to battery limits.
Hexene-3 from the autometathesis unit is mixed with hexene recycle from the hexene distillation section and is vaporized, preheated and fed to the hexene isomerization reactor where hexene-3 is isomerized to hexene-1 and hexene-2 over a fixed bed of proprietary isomerization catalyst. Reactor effluent is cooled and flows to the hexene distillation section (6) where fractionators separate it into hexene-1 product, recycle hexene-2/hexene-3, and a purge to remove any heavies present in the hexene-3 feed.
Licensor: Lummus Technology