A Robust n-C4 Isomerization Process
Isomalk-3 is a low-temperature isomerization technology for processing n-butane into isobutane (i-butane), its branched polymer. Isobutane is an important intermediate required for the production of isobutylene or alkylate. Isobutylene can be used to produce MTBE or other high-value petrochemicals such as isoprene through a synthetic on-purpose route.
The Isomalk-3 technology is based on the use of a mixed-metal oxide SI-3™ catalyst with high selectivity to i-butane. Operating at a temperature of 150-170°C (302-338°F), the yield and operating expenses are optimized. The expected lifetime of the SI-3 catalyst is over 10 years. The process eliminates the need for chlorine injection, off-gas caustic scrubbing and associated equipment expenses. Water, sulfur and nitrogen specs for the feed are significantly lowered. Breakthrough of these contaminants is permissible, and catalyst activity can be restored via “in-situ” catalyst regeneration. As with the other catalysts associated with the Isomalk family, operation is simple and reliable; startup, turnaround and shutdown times are minimal due to the high resistance to catalytic poisons and, most important, water.
Isomalk-3 can achieve high conversion to isobutane while significantly reducing equipment needs, and it is the only available nonchlorinated process based on n-C4 isomerization technology that has been commercially successful. The SI-3 catalyst provides a close approach to thermal equilibrium at low temperatures and exhibits outstanding stability, simplicity and safety in operation. Isomalk-3 can efficiently separate out C5+ from feeds in a dividing-wall-column deisobutanizer that allows for greater feedstock flexibility. The process can be adapted for reverse isomerization of i-butane to n-butane as well.
The process requires a one-reactor configuration and eliminates the chemical consumption of organochlorides and caustic for operation. Cooling water or refrigerant serves as a medium to recover i-C4 and n-C4 in the stabilizer overhead, depending on the available utilities on site. The subsequent integration of the i-butane with downstream dehydrogenation technology allows the optimal recovery of all products of the isomerization reaction, heat integration, minimized OSBL requirements and plot plan.
Isomalk-3 is the only available nonchlorinated process for n-C4 isomerization that is commercially successful. The SI-3 catalyst provides a close approach to thermal equilibrium at low temperatures and exhibits outstanding stability, simplicity and safety in operation. Features of Isomalk-3 include:
- Low operating and capital costs
- No chloride addition or caustic treatment needed; no wastes produced
- Regenerable catalyst (SI-3) – ease of operation and long service life of 10+ years
- Robust design – highly tolerant to process fluctuations resulting in 48 to 60 months between catalyst regeneration
- High conversion per pass – results in process configuration with only one reactor
- High selectivity – low hydrogen consumption
- Low-hydrogen partial-pressure requirement – no recycle gas compressor or separator
Isomalk-3 is licensed in partnership by Sulzer GTC and NPP Neftehim.