Application: The Snamprogetti Cracking Technology allows producing high-purity isobutylene, which can be used as monomer for elasto-mers (polyisobutylene, butyl rubber) and/or as an intermediate for the production of chemicals—MMA, tertiary-butyl phenols, tertiary-butyl amines, etc.
Feed: Methyl tertiary butyl ether (MTBE) can be used as feedstock in the plant. In the case of high level of impurities, a purification section can be added before the reactor.
Description: The MTBE cracking technology is based on proprietary cat-alyst and reactor that carry out the reaction with excellent flexibility and mild conditions as well as without corrosion and environmental prob-lems. With Snamprogetti consolidated technology, it is possible to reach the desired isobutylene purity and production with only one tubular reactor (1) filled with a proprietary catalyst characterized for the right balance between acidity and activity.
The reaction effluent, mainly consisting of isobutylene, methanol and unconverted MTBE, is sent to a counter-current washing tower (2) to separate out methanol, and then to two fractionation towers to separate isobutylene from unconverted MTBE, which is recycled to the reactor (3) and from light compounds (4). The produced isobutylene has a product purity of 99.9+ wt%.
The methanol/water solution leaving the washing tower is fed to the alcohol recovery section (5), where high-quality methanol is recov-ered.
Utilities:
Steam, ton/ton isobutylene 5
Water, cooling, m³/ton isobutylene 186
Power, kWh/ton isobutylene 17.4
Commercial plants: Six units have been licensed by Saipem.
Licensor: Saipem - CONTACT
2
Ether
High-purity isobutene MTBE feed
MeOH 1
3
5
4 Light ends
Petrochemical Processes 2010 2010
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Isomerization
Application: Convert iso-olefins to normal olefins.
Description:
C4 olefin skeletal isomerization (CDIsis)
A zeolite-based catalyst especially developed for this process pro-vides near equilibrium conversion of isobutylene to normal butenes at high selectivity and long process cycle times. A simple process scheme and moderate process conditions result in low capital and operating costs. Hydrocarbon feed containing isobutylene, such as C4 raffinate or FCC C4s, can be processed without steam or other diluents, nor the addition of catalyst activation agents to promote the reaction. Near-equilibrium conversion of the contained isobutylene per pass is achieved at greater than 85% selectivity to isobutylene. At the end of the process cycle, the catalyst bed is regenerated by oxidizing the coke with an air/
nitrogen mixture. The butene isomerate is suitable for making various petrochemical such as propylene via Olefin Conversion Technology.
Economics: The CDIsis isomerization process offers the advantages of low capital investment and operating costs coupled with a high yield of isobutylene. Also, the small quantity of heavy byproducts formed can easily be blended into the gasoline pool. Capital costs (equipment, labor and detailed engineering) for three different plant sizes are:
Total installed cost: Feedrate, Mbpd ISBL cost, $MM
10 8
15 11
30 30
Utility costs: per barrel of feed (assuming an electric-motor-driven com-pressor) are:
Power, kWh 3.2
Fuel gas, MMBtu 0.44
Steam, MP, MMBtu 0.002
Water, cooling, MMBtu 0.051
Nitrogen, scf 57–250
Commercial plants: Three plants are in operation. Three licensed units are in various stages of design.
Licensor: CDTECH - CONTACT
3
4 2
5
Isobutylene
Isomerized C4 olefins
C5+
Petrochemical Processes 2010 2010
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Isomerization
Application: Isomalk-2 is a broad-range isomerization technology devel-oped by NPP Neftehim, which has been commercially proven in various regions of the world. Isomalk-2 is a competitive alternative to the three most commonly used light gasoline isomerization processes: zeolite, chlorinated alumina and sulfated oxide catalysts.
Description: Isomalk-2 offers refiners cost-effective isomerization op-tions that have consistently demonstrated reliable performance with all standard process configurations, including once-through isomerization, once-through with pre-fractionation, recycle of low-octane pentanes and hexanes, and benzene reduction
Each scheme generates different yield and octane results. The ex-amples given below are for a light straight-run (LSR) process stream, but could also be applied to a reformate stream or some LSR/reformate combinations. In a once-through isomerization process scheme, the LSR is mixed with the hydrogen makeup gas; the mixture is then heated and enters a first reactor where benzene saturation and partial isomerization take place.
The gas-product mixture exits the first reactor, is cooled and fed to a second reactor to complete the isomerization reaction at chemical equilibrium. The product mixture from the second reactor is cooled and fed to a gas separator, where the mixture is separated from the excess hydrogen gas. Excess hydrogen is combined with makeup hydrogen and fed through the recycle dryers for blending with feed. There is no hydrocarbon feed drying step required.
Saturated isomerate from the separator is heated and fed to the stabilizer. The stabilizer’s overhead vapors are cooled and fed to a reflux drum. Liquid hydrocarbons from the reflux drum are returned to the stabilizer as reflux; while uncondensed light hydrocarbons are separat-ed and sent to the offgas system. The bottom product or isomerate is cooled and sent to gasoline blending.
In an isomerization process scheme with recycle of low-octane hexanes, the isomerate is produced and then fed to a fractionation column(s). Overhead and bottoms isomerate streams are cooled and sent to gasoline blending. A low-octane C6 isomerate stream is recycled back to the isomerization unit.
Prefractionation with low-octane recycle can utilize all of the above methods: prefractionation, isomerization and postfractionation. The prefractionation step consists of de-isopentanization of the feed and/
or C7+ separation. The post fractionation step consists of separating the high octane portion of the C5–C6 isomerate and recycling the low-oc-tane C5 and C6 isomerate stream.
Isopentane fraction Product RON 91-92
Continued
Copyright © 2010 Gulf Publishing Company. All rights reserved.
Copyright © 2010 Gulf Publishing Company. All rights reserved.