Technology

Technology Heritage and Development

Axens butene-1 superfractionation technology for 1-butene extraction from raffinate streams traces its roots to the Institut Français du Pétrole (IFP) research and development programs of the 1970s-1980s. The foundational patents FR2474024A1 (1980) and GB2068408A (1981) represent the core intellectual property that evolved into Axens' current commercial offering.

Process Overview

The superfractionnation technology is designed to extract high-purity, polymer-grade 1-butene from C₄ raffinate streams, particularly raffinate-2 (RAF-2) after butadiene and isobutylene removal. It employs a two-column extractive distillation system featuring superfractionnation columns with a high theoretical plate count, enabling sharp separation of components with very close boiling points.

Technical Process Description

Feed Preparation and Upstream Integration

• Feedstock: Raffinate-2 containing typically 50-60% 2-butenes, 10-15% 1-butene, ~20% n-butane, and minor amounts of isobutane
• Feed Conditioning: The technology accommodates various C₄ olefinic cuts from steam crackers and FCC units

Stage 1: First Extractive Distillation

• Technology: Extractive distillation using polar solvent
• Solvent: Dimethylformamide (DMF) with additives (e.g., 0.1% nitrobenzene, 0.05% sodium nitrite)
• Separation: Removes saturated hydrocarbons (isobutane, n-butane) as overhead raffinate, while butenes and impurities go to bottoms with solvent
• Column Configuration: ~100 theoretical plates
• Includes: Solvent stripping column to recover and recycle DMF

Stage 2: Second Extractive Distillation

• Technology: Also extractive distillation using polar solvent
• Solvent: Same DMF-based solvent system
• Separation: Removes diolefinic and acetylenic impurities, producing high-purity butene-1 as raffinate
• Column Configuration: ~100 theoretical plates
• Includes: Second solvent stripping column for solvent recovery

Solvent Recovery and Recycling

• Regeneration Column: 40+ theoretical plates for solvent purification
• Heat Integration: Optimized thermal integration between extractive and regeneration columns
• Solvent Recycle Rate: >99% solvent recovery and reuse

Performance Specifications

Product Quality Achievements

• 1-Butene Purity: >99.5 wt% consistently achieved
• 1-Butene Recovery: ≥90% from the superfractionation section
• Impurity Levels:
  • Isobutane: <0.1 wt%
  • n-Butane: <0.3 wt%
  • 2-Butenes: <0.1 wt%
  • Residual aromatics and sulfur compounds: <10 ppm each

Process Efficiency Metrics

• Energy Integration: Heat pump integration opportunities for enhanced efficiency
• Utilities Consumption: Optimized steam and cooling water requirements
• Operating Flexibility: Handles feed composition variations of ±10% without performance degradation

Commercial Implementation

Reference Applications

• Global Licensing: Technology deployed across diverse geographic markets including Middle East, Asia, and Europe
• Scale Range: Commercial units from 50,000 to 200,000+ metric tons per annum

Technology Advantages

• Proven Reliability: Decades of commercial operation with >95% on-stream factor
• Feedstock Flexibility: Processes various C4 cuts from different cracking technologies
• Integration Benefits: Seamless integration with existing C4 processing complexes
• Economic Performance: Competitive production costs for polymer-grade 1-butene

Process Innovation Features

Advanced Process Control

• Composition Control: Real-time monitoring and adjustment of product specifications
• Energy Optimization: Dynamic optimization of reflux ratios and solvent flows
• Predictive Maintenance: Advanced monitoring of column performance parameters

Environmental Considerations

• Minimal Waste Generation: Closed-loop solvent system with negligible losses
• Energy Efficiency: Heat integration reduces overall energy consumption by 15-20%
• Emissions Control: Low volatile organic compound (VOC) emissions through optimized design

References

1. French Patent FR2474024A1, Process for obtaining high-purity 1-butene from C₄ hydrocarbon mixtures, Institut Français du Pétrole, 1980.
2. British Patent GB2068408A, Process for obtaining high-purity 1-butene from C₄ hydrocarbon mixtures, Institut Français du Pétrole, 1981.
3. Axens, C₄ Fractionation - Butene-1 Superfractionation.
4. Axens, Butene-1 recovery.
5. M. Naeem et al. (2014). Process simulation of 1-butene and n-butane separation by extractive distillation. IJERT. 3. 747-750.
6. R. Hirani et al. (2020). DWSIM Project, Separation of 1-Butene and N-butane by Extractive Distillation.