Technology

Technology Summary

Axens' n-butane isomerization technology is designed to restore the thermodynamic equilibrium (isobutane to n-butane ratio) in C₄ paraffinic cuts, converting low-value normal butane into high-value isobutane, relying on the current commercial offering featuring the proprietary ATIS-1L catalyst. The technology serves multiple strategic applications, primarily to provide provide high-purity isobutane for alkylation units enabling production of high-octane alkylate gasoline components, but also to supply isobutane for dehydrogenation to isobutylene, subsequently used in the production of ethers (MTBE/ETBE).

Detailed Process Description

Axens' n-butane isomerization follows the following sequential steps:

• Reactants preparation:
  • Feed drying: n-butane-rich cut is processed through molecular sieve dryers to remove moisture and contaminants that could poison the chlorinated alumina catalyst.
  • Hydrogen treatment: Make-up hydrogen is similarly dried using molecular sieve adsorbents to ensure long catalyst lifetimes.
  • H2/HC molar ratio: Hydrogen and hydrocarbon feed are typically fed to the reactor at a 0.07-0.15 ratio for optimal catalyst performance.
• Reaction Section:
  • Dual reactor configuration: Features permutable reactors R-1 and R-2 operating in series, providing operational flexibility and ultra-high on-stream service factor.
  • Temperature control: Medium pressure (MP) steam heating maintains optimal reaction temperatures for thermodynamic equilibrium.
  • Chloriding agent injection: Continuous supply of chlorinating agent (typically perchloroethylene) maintains catalyst activity.
• Product Recovery Section:
  • Stabilizer column (STAB): Separates light gases and dissolved hydrogen from the isomerate product.
  • Cooling water (CW) system: Provides process cooling and temperature regulation.
  • Chiller package: Manages product cooling and separation efficiency.
• Environmental Controls: 
  • Caustic scrubbing: Off-gas treatment removes hydrogen chloride before release, requiring continuous caustic supply and generating alkaline waste streams.

ATIS-1L Catalyst System

The ATIS-1L catalyst represents Axens' state-of-the-art solution for C₄ paraffin isomerization, claimed to provide unsurpassed combination of high activity, low cost, and low platinum content:

• Technical specifications:
  • Composition: Platinum on chlorinated alumina support.​​​​​​​
  • Activity: Enables effective operation at low temperatures with very high equilibrium conversion rates.
  • Platinum content: Features reduced platinum content compared to competing formulations while maintaining superior performance.
• Operational Characteristics:
  • High activity: Allows operation at lower reactor temperatures that enable higher iC4/nC4 equilibrium and favor superior yields.
  • Selectivity: Achieves minimum 98% selectivity to isobutane at typical operating conditions.
  • Stability: Requires continuous chloriding agent supply to maintain active acidic sites.

Performance and Efficiency

• Single-Pass Conversion: Achieves equilibrium-limited conversion rates
• Selectivity: Minimum 98% selectivity to desired isobutane product
• Catalyst Life: Typical service life of 3-5 years with proper operation and feed quality control
• Yield: High liquid product yields with minimal light gas formation

Commercial Experience

Reference Installations

Axens has deployed more than 120 commercial references since the 1990s in C₄ and C₅/C₆ applications with ATIS series catalysts.

References

1. Axens. Upgrading C4 Paraffinic Cuts using Isomerization Processes. Technical Brochure. Axens Group.
2. Axens. C₄ Isomerization, Alkylation & Olefins Hydrogenation. Retrieved from https://www.axens.net/expertise/oil-refining/c4-isomerization-alkylation-olefins-hydrogenation
3. Axens. Isomerization Catalysts. Retrieved from https://www.axens.net/solutions/catalysts-adsorbents-grading-supply/isomerization-catalysts?language=en
4. Axens. C₄ Isomerization. Retrieved from https://www.axens.net/taxonomy/term/420
5. Axens. Process Technologies. Retrieved from https://www.axens.net/taxonomy/term/11?page=50
6. Axens. Isomerization Catalysts. Retrieved from https://www.axens.net/solutions/catalysts-adsorbents-grading-supply/isomerization-catalysts
7. Axens. Catalysts & Adsorbents Catalogue - English. Product Catalogue. Axens Group.
8. ExxonMobil Chemical. ALKEMAX™ Sulfuric Acid Alkylation Technology. Technical Factsheet. Retrieved from https://www.exxonmobilchemical.com/-/media/media-assets/media-library-assets/3/catalysts_licensing_factsheet_alkemax_saa_en.pdf
9. Europétrole. Axens and ExxonMobil Catalysts and Licensing LLC sign alliance agreement to provide technologies for high-octane alkylate production. Euro Petrole News. Retrieved from https://www.euro-petrole.com/axens-and-exxonmobil-catalysts-and-licensing-llc-sign-alliance-agreement-to-provide-technologies-for-high-octane-alkylate-production-n-i-18396
10. Europétrole. Axens to supply technologies for S-Oil's residue upgrading capacity expansion project. Euro Petrole News. Retrieved from https://www.euro-petrole.com/axens-to-supply-technologies-for-s-oil-s-residue-upgrading-capacity-expansion-project-n-i-11682
11. Jechura, J. (2019). Gasoline Upgrading: Reforming, Isomerization, & Alkylation. CBEN409 Course Materials. Colorado School of Mines. Retrieved from https://people.mines.edu/jjechura/wp-content/uploads/sites/120/2019/02/CBEN409_09_Gasoline_Upgrading.pdf
12. Oil & Gas Journal. (2015, July 16). S-Oil lets contracts for Onsan refinery, olefins projects. Retrieved from https://www.ogj.com/refining-processing/refining/operations/article/17246338/s-oil-lets-contracts-for-onsan-refinery-olefins-projects
13. Semantic Scholar. (n.d.). Catalysts [PDF document]. Retrieved from https://pdfs.semanticscholar.org/6c64/904ba72acb7fcf2000cf0128abe1ee25278c.pdf