Gas storage spheres tank in petrochemical plant at night

C4 and aromatics value chain

Linde collaborates with its partners to deliver C4 and aromatics production facilities and seamlessly integrate them into cracker facilities for increased overall yield and cost effectiveness

C4 Processing

Liquid steam crackers produce significant quantities of valuable unsaturated C4 hydrocarbons like butadiene, butene-1 and isobutylene. Depending on regional or global market demand, these valuable products can often be recovered economically.

Options for processing C4 cuts in downstream crackers include:

  • Butadiene extraction
  • Removal of ethyl and vinyl acetylene to facilitate butadiene extraction processing
  • Conversion of 1,3-butadiene to maximize 1-butene or 2-butene yield
  • Production of high-purity isobutylene
  • Hydrogenation of total C4 cut for recycling to cracking furnace or export
  • Total hydrogenation of combined C3/C4 and/or C4/C5 cuts for recycling to cracking furnace to boost olefin yield and reduce feedstock consumption
Linde collaborates with world-class C4 processing licensors and catalyst vendors to develop best-cost value chains for C4 processing and recovery. Close cooperation ensures flawless project execution and a one-stop service for customers.

Diagram of C4 processing
Diagram of C4 processing

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C4 Processing – Hydrogenation

Depending on the target product slate, Linde delivers selective and full hydrogenation units as part of its complete steam cracker complex offering. Through close and long-standing collaboration with third-party hydrogenation licensors, we also offer a single point of accountability for an entire licensing package.

Ethylene plant in Tasnee

C4 selective hydrogenation

C4 selective hydrogenation is used to convert butadiene to 1-butene via MTBE. The value chain could be adapted to provide commercial-grade MTBE.

Highlights of Linde’s C4 selective hydrogenation offering include:

  • Butadiene conversion down to 10 – 5000 ppm-wt
  • Product to HPIB plants
  • Recovery of 1-butene product purity ~99.5 wt %, by distillation 
  • Flexibility with regard to 1-butene/2-butene ratio
  • C4 product as feedstock for ETBE (MTBE) plants or for full hydrogenation 
  • Close alignment with downstream processing
  • Hydro-isomerization to 2-butene

C4 full hydrogenation

A C4 full hydrogenation unit is used to improve the ethylene yield. It converts all unsaturated C4 hydrocarbons and saturated C4 streams, and recycles these back to the cracking furnace.

Highlight of Linde’s C4 full hydrogenation offering include:

  • 1-stage process with trickle phase reactor, olefin conversion > 98%
  • Acetylene, butadiene and butene conversion down to – 5 ppm-wt
  • Product fed to cracking furnace (C4 recycling)
  • Converts all unsaturated C4 hydrocarbons, thus avoiding the risk of severe coke formations especially if butadiene content is high

Linde offers C4 full hydrogenation process designs in collaboration with licensors and catalyst vendors.

PE plant in Al-Jubail
Petrochemical plant in Baytown

C4/C5 full hydrogenation

The C4/C5 full hydrogenation unit is a licensed process used to improve the ethylene yield. It converts all unsaturated C4/C5 hydrocarbons to avoid coke formation. Saturated streams are recycled back to the cracking furnace. The process scheme and layout are identical to the C4 full hydrogenation configuration.

High-purity isobutylene (HPIB)

Strong demand growth makes high-purity isobutylene one of the fastest growing chemical intermediates worldwide. It is used in a wide variety of high-value applications such as butyl rubber, polyisobutylene (PIB) and (poly) methyl methacrylate (PMMA). 

Based on a comprehensive cooperation agreement between BASF and Linde, Linde is in a unique and exclusive position to offer licensing and the full range of engineering, procurement and construction (EPC) services for BASF’s superior technology enabling the production of HPIB from refinery and steam cracker C4 streams. 

Not only does this technology represent a step change in process economics compared with other HPIB production routes, it also offers the following technical benefits:  

  • High selectivity and product quality
  • No formation of azeotrope, vastly simplifying the separation process and reducing the energy demand
  • Wide range of capacities (from 25 kt/a to more than 150 kt/a) proven commercially
  • No specialized equipment required  

High-purity isobutylene (HPIB)

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