Technology

Technology overview

• HEXSIB is SIBUR's proprietary ethylene trimerization technology for on-purpose production of 1-hexene, developed at NIOST (one of SIBUR's main R&D centers) and licensed globally by Technip Energies.​​
• The technology employs a chromium-based homogeneous catalyst system with innovative microwave activation to selectively trimerize ethylene to polymer-grade 1-hexene at exceptional selectivity (>99.7%) under mild operating conditions.

Catalyst System Description

Core Catalyst Composition (per US10508065B2 and US11291982B2)

The HEXSIB catalyst system comprises four essential components:​

1. 1. Chromium source compound
   • Trivalent chromium compounds are preferred
   • Common chromium sources include chromium(III) chloride, chromium(III) acetate, chromium carboxylates, and organochromium complexes
   • Molar ratios are optimized based on the specific chromium compound selected​
2. 2. Nitrogen-containing ligand (pyrrole compound)
   • Pyrrole or substituted pyrrole derivatives serve as the primary ligand
   • The pyrrole:Cr molar ratio ranges from 3:1 to 7:1, optimally around 4:1 to 6:1
   • The nitrogen-containing ligand coordinates with chromium to form the active catalytic species​
3. 3. Alkylaluminum compound (activator/cocatalyst)
   • Trialkylaluminum compounds such as triethylaluminum (TEA), triisobutylaluminum (TIBA), or tri-n-octylaluminum
   • Al:Cr molar ratio ranges from 5:1 to 200:1, typically 10:1 to 100:1
   • The alkylaluminum serves dual roles: activator and scavenger for trace impurities​
4. 4. Zinc compound (performance enhancer)
   • Zinc halides (ZnCl₂, ZnBr₂) or organozinc compounds
   • Zn:Cr molar ratio typically 1:1 to 10:1
   • Zinc incorporation significantly improves catalyst activity, selectivity, and stability​

Innovative Microwave Activation (SIBUR Patent Innovation)

A key differentiating feature of HEXSIB is microwave irradiation of catalyst components, particularly the alkylaluminum compound:​

• Microwave treatment parameters:
  • The alkylaluminum compound is irradiated with microwave (ultra-high frequency, UHF) radiation prior to mixing with other catalyst components
  • Microwave frequency: typically 2.45 GHz (standard industrial microwave frequency)
  • Irradiation duration: seconds to minutes, typically optimized for each specific formulation
  • Temperature control during irradiation prevents decomposition
  • Mixing with chromium compound occurs within 10 minutes of microwave treatment to preserve activated state​
• Benefits of microwave activation:
  • Significantly enhanced catalyst activity (2-5× improvement reported)
  • Improved selectivity to 1-hexene
  • Better catalyst stability and longer active lifetime
  • Enables operation at lower ethylene pressures (as low as 20-40 bar vs. 50+ bar for conventional systems)​

Catalyst Preparation Sequence

1. Microwave irradiate alkylaluminum compound under controlled conditions
2. Within 10 minutes, mix irradiated alkylaluminum with chromium source
3. Add pyrrole compound to form chromium-pyrrole complex
4. Introduce zinc compound to complete catalyst system
5. Dilute with reaction solvent if necessary
6. Feed continuously or batch-wise to reactor​

Reaction Chemistry and Mechanism

Trimerization Reaction

The selective ethylene trimerization follows a metallacycle mechanism characteristic of chromium-pyrrole catalyst systems:​

Overall reaction:

Reaction characteristics

• Highly selective for 1-hexene formation via chromacyclic intermediates
• Exothermic reaction: ΔH ≈ -180 to -200 kJ/mol
• Minimal formation of C₄ (1-butene) or C₈⁺ oligomers
• Polymer formation suppressed by optimized catalyst design and operating conditions​

Selectivity Performance

SIBUR patents claim exceptional selectivity:​

• 1-Hexene isomeric purity: ≥99.7% (ratio of 1-hexene to other hexene isomers ≥99.7:0.3)
• 1-Hexene selectivity in C₆ fraction: >99.9% achieved with optimized catalyst system​
• Overall selectivity to C₆ (hexenes): 85-95% based on ethylene converted
• C₄ (butenes) formation: <3%
• C₈+ (higher oligomers): <5%
• Polyethylene formation: Minimized through process control​

This exceptional selectivity is a key HEXSIB differentiator and simplifies downstream separation.

Feed Specifications

Ethylene purity requirements

• Polymer-grade ethylene (>99.9% purity)
• Oxygen content: <5 ppm (preferably <1 ppm)
• Water content: <5 ppm
• Sulfur compounds: <1 ppm
• Acetylene and other poisons: minimized through feed purification​​

Process Configuration and Operating Conditions

Reactor System

Reactor type:

• Liquid-phase stirred tank reactor (CSTR) or loop reactor configuration
• Continuous operation for commercial scale
• Temperature control via external cooling or internal heat exchange​

Solvent/diluent:

• Hydrocarbon solvents: toluene, xylenes, cyclohexane, or aliphatic hydrocarbons (C₆-C₁₂)
• 1-Hexene can serve as reaction medium (autogenous solvent)
• Solvent selection impacts selectivity and heat management​

Operating parameters

Operating conditions (per SIBUR patents):​

Parameter	Range	Typical/Optimal
Temperature	0-120°C	40-90°C
Pressure	20-150 bar	30-70 bar
Ethylene partial pressure	15-100 bar	25-50 bar
Residence time	10-120 minutes	30-60 minutes
Catalyst concentration	0.01-1.0 mmol Cr/L	0.05-0.5 mmol Cr/L

Key advantages of HEXSIB operating window:​​

• Lower temperature and pressure versus competing technologies
• Milder conditions reduce capital equipment requirements
• Lower energy consumption
• Improved safety profile

Reaction Performance Metrics

Catalyst productivity:

• 50,000-500,000 g 1-hexene per g Cr (highly dependent on conditions)
• Turnover frequency (TOF): 10,000-100,000 mol ethylene converted per mol Cr per hour
• Enhanced by microwave activation​

Ethylene conversion per pass:

• Single-pass conversion: 30-70%
• Unreacted ethylene recycled to reactor
• Overall ethylene utilization: >99%

Equipment List

A detailed equipment list is proposed in the Appendix. 

Separation and Product Work-Up (per US11912658B2)

SIBUR's separation patent (US11912658B2) describes an innovative split-flow separation scheme optimized for the HEXSIB process:​

1. Catalyst deactivation and quench
   • Reaction mass discharged from oligomerization reactor
   • Contacted with catalyst deactivating agent (alcohol, water, or alkaline solution)
   • Rapid quench stops reaction and stabilizes product slate​
2. Primary ethylene recovery
   • Flash separation or distillation removes unreacted ethylene
   • Ethylene recycle stream returned to reactor feed after compression/purification
   • Oligomerization product stream proceeds to further fractionation​
3. Split-flow separation (SIBUR innovation)
   The patent describes a key innovation: splitting the oligomerization product stream into two parallel processing paths:​
          → Path A: Part of product to distillation column for high-purity fractionation
          → Path B: Part of product to evaporator for bulk separation with lower fouling risk
   This split-flow design minimizes polymer contamination of equipment and extends run lengths between cleaning cycles.​
4. 1-Hexene product isolation
   • Distillation column(s) separate 1-hexene from:
     • Lighter components (C₄, C₅ if present)
     • Heavier components (C₈+, solvent)
   • Multiple distillation stages achieve polymer-grade 1-hexene specification
   • Evaporator handles streams with higher polymer/heavy oligomer content​
5. Heavy ends management
   • C₈+ oligomers and trace polymer removed as bottoms
   • Minimal heavy ends due to high front-end selectivity
   • Solvent recovery and recycle where applicable

Product Specifications

Polymer-grade 1-hexene (HEXSIB product):​​

Property	Specification
1-Hexene purity	>99.7% (>99.9% achievable)
Other C₆ isomers	<0.3%
C₄ and lighter	<100 ppm
C₈ and heavier	<500 ppm
Water	<50 ppm
Peroxides	<10 ppm
Color	Water-white

This product meets requirements for all commercial PE catalyst systems (Ziegler-Natta, metallocene, chromium, single-site).

Plant Configuration: Nizhnekamskneftekhim (NKNH) Implementation

Project Overview

SIBUR's first commercial HEXSIB unit is at Nizhnekamskneftekhim (NKNH) in Tatarstan, Russia:​

• Capacity: 50,000 tonnes/year 1-hexene
• Feed integration: Ethylene from EP-600 olefins complex (1,500 kt/y ethylene cracker)
• Timeline: Construction completed end-2024, commissioning 2024-2025, commercial operation 2025
• Strategic purpose: Replace imported 1-hexene (previously sourced from UK and Germany); supply 125-130% of SIBUR's internal demand​

Process Integration

• Direct ethylene pipeline from EP-600 to HEXSIB unit
• Closed-loop water circulation system for cooling
• Closed flare system for emissions control (low-carbon design)
• 1-Hexene product storage and distribution to SIBUR PE plant

Technology Performance Summary

Key Performance Indicators

Metric	HEXSIB Performance	Industry Benchmark
1-Hexene selectivity	>99.7% isomeric purity	95-99%
C₆ selectivity (on ethylene)	85-95%	80-90%
Operating pressure	30-70 bar	50-100+ bar
Operating temperature	40-90°C	80-120°C
Catalyst productivity	50,000-500,000 g/g Cr	Variable
Energy efficiency	High (mild conditions)	Moderate to high
Capital intensity	Lower (simpler equipment)	Higher

Technology Advantages (per SIBUR/Technip statements)

1. Milder operating conditions: Lower T/P reduce equipment cost and energy use​
2. Exceptional selectivity: >99.7% 1-hexene purity simplifies separation​​
3. High catalyst performance: Microwave activation enhances activity and stability​
4. Simplified separation: High selectivity reduces fractionation complexity​​
5. Lower carbon footprint: Energy efficiency and potential for bio-based ethylene feedstock​
6. Drop-in compatibility: Product meets all PE catalyst system requirements​
7. Proven scale-up: Commercial unit operating at NKNH

Techno-Economic Positioning

Competitive Advantages

• vs. Full-range α-olefin processes: HEXSIB is dedicated to 1-hexene, avoiding co-product balance issues
• vs. Other trimerization routes: Microwave activation and zinc enhancement improve economics
• vs. Imported 1-hexene: Integrated production reduces logistics costs and supply risk

Market and Licensing Strategy

• Internal use: SIBUR PE plants (LLDPE/HDPE specialty grades)
• External licensing: Technip Energies offers HEXSIB to global polyolefin producers
• Integration opportunities: Can be incorporated into greenfield PE complexes or retrofitted to existing sites​

References

SIBUR Patents (Ethylene Trimerization to 1-Hexene)

1. US10508065B2 (granted Dec 17, 2019): Methods of preparing oligomers of an olefin. Inventors: Zilbershtein TM, Lenev DA, Lipskikh MV. Assignee: SIBUR Holding PJSC.​
2. US11291982B2 (granted Apr 5, 2022): Catalyst system used in olefin oligomerization and method for olefin oligomerization. Inventors: Lenev DA, ACEVEDO FORERO R. Assignee: SIBUR Holding PJSC.​
3. US11912658B2 (granted Feb 27, 2024): Method for separating olefin oligomerization products (variants). Inventors: Arkatov OL, Lipskikh MV, Popov EA, Khusainov AF. Assignee: SIBUR Holding PJSC.​
4. US8921251B2 (granted Dec 30, 2014): Catalyst system and processes for the (co-)trimerization of olefins and the (co-)polymerization of olefin oligomers. Inventors: Zilbershtein TM, Lipskikh MV, Nosikov AA, Nesyn GV. Assignee: SIBUR Holding PJSC.​

SIBUR and Technip Energies Communications

1. SIBUR. SIBUR's speciality chemical tech used in premium basic polymer production goes international. Press release | Jan 12, 2022​
2. Technip Energies and SIBUR. Technip Energies and SIBUR announce agreement to license lower-carbon HEXSIB technology. Joint press release | Jan 11, 2022​
3. Interfax. SIBUR to produce up to 50,000 tpy of hexene at Nizhnemkamskneftekhim. Aug 31, 2022.​
4. PGCA/NANGS. Sibur will start switching to its own hexene in 2025 from the installation at NKNH. Apr 22, 2024.​
5. Interfax. SIBUR receives first hexene product from NKNK facility. Aug 25, 2025.