Application: New processes, RHT-isooctene and RHT-isooctane, can be used to revamp existing MTBE units to isooctene/isooctane production. Feeds include C4 iso-olefin feed from FCC, steam crackers, thermal crackers or on-purpose iso-butylene from dehydrogenation units. The processes uses a unique configuration for dimerization. A new selectivator is used, together with a dual-bed catalyst.
The configuration is capable of revamping conventional or reactive distillation MTBE units. The process provides higher conversion, better selectivity, conventional catalyst, and a new selectivator supports with longer catalyst life with a dual catalyst application.
The process is designed to apply a hydrogenation unit to convert isooctene into isooctane, if desired, by utilizing a dual-catalyst system, in the first and finishing reactors. The process operates at lower pressure and provides lower costs for the hydrogenation unit.
Description: The feed is water washed to remove any basic compounds that can poison the catalyst system. Most applications will be directed toward isooctene production. However as olefin specifications are required, the isooctene can be hydrogenated to isooctane, which is an excellent gasoline blending stock.
The RHT isooctene process has a unique configuration; it is flexible and can provide low per pass conversion through dilution, using a new selectivator. The dual catalyst system also provides multiple advantages. The isobutylene conversion is 97–99 %, with better selectivity and yield together with enhanced catalyst life. The product is over 91% C8 olefins, and 5 – 9% C12 olefins, with very small amount of C16 olefins.
The feed after water wash, is mixed with recycle stream, which provides the dilution (also some unreacted isobutylene) and is mixed with a small amount of hydrogen. The feed is sent to the dual-bed reactor for isooctene reaction in which most of isobutylene is converted to isooctene and codimer. The residual conversion is done with singleresin catalyst via a side reactor. The feed to the side reactor is taken as a side draw from the column and does contain unreacted isobutylene, selectivator, normal olefins and non-reactive C4s. The recycle stream provides the dilution, and reactor effluent is fed to the column at multiple locations. Recycling does not increase column size due to the unique configuration of the process. The isooctene is taken from the debutanizer column bottom and is sent to OSBL after cooling or as is sent to hydrogenation unit. The C4s are taken as overhead stream and sent to OSBL or alkylation unit. Isooctene/product, octane (R+M)/2 is expected to be about 105.
If isooctane is to be produced the debutanizer bottom, isooctene product is sent to hydrogenation unit. The isooctene is pumped to the required pressure (which is much lower than conventional processes), mixed with recycle stream and hydrogen and is heated to the reaction temperature before sending it the first hydrogenation reactor. This reactor uses a nickel (Ni) or palladium (Pd) catalyst.
If feed is coming directly from the isooctene unit, only a start-up heater is required. The reactor effluent is flashed, and the vent is sent to OSBL. The liquid stream is recycled to the reactor after cooling (to remove heat of reaction) and a portion is forwarded to the finishing reactor—which also applies a Ni or Pd catalyst (preferably Pd catalyst) — and residual hydrogenation to isooctane reaction occurs. The isooctane product, octane (R+M)/2 is >98.
The reaction occurs in liquid phase or two phase (preferably two phases), which results in lower pressure option. The olefins in isooctene product are hydrogenated to over 99%. The finishing reactor effluent is sent to isooctane stripper, which removes all light ends, and the product is stabilized and can be stored easily.
Licensor: Refining Hydrocarbon Technologies LLC.