Product

Cracked LPG is a liquefied petroleum gas stream consisting of C₃ and C₄ hydrocarbons recovered from secondary conversion (cracking) units in a refinery—such as the Fluid Catalytic Cracking Unit (FCCU), hydrocracker, delayed coker, visbreaker, or steam cracker—where it is produced as a byproduct of the thermal or catalytic breakdown of heavier hydrocarbon molecules (VGO, residue, or naphtha).

Key characteristics:

• Origin: Generated in conversion units as part of the cracked gas fraction, then recovered in the unit's gas concentration/gas plant section (absorber, stripper, debutanizer), in contrast to straight-run LPG, which comes directly from crude distillation.
• Composition: Unlike straight-run LPG, cracked LPG contains significant unsaturated (olefinic) hydrocarbons, because cracking reactions produce olefins alongside paraffins:
  • C₃ fraction: propane + propylene (often 30–70% propylene in FCC C₃s)
  • C₄ fraction: butanes + butenes/butylenes, and in some streams trace butadiene (notably in steam cracker C₄s)
• Contaminants: May contain H₂S, mercaptans, CO₂, nitrogen compounds, diolefins, and water—requiring amine treating, sweetening, and sometimes selective hydrogenation or extraction before use.
• Value and end uses: The olefin content makes cracked LPG considerably more valuable than straight-run LPG:
  • Propylene: recovered and upgraded to chemical/polymer grade for polypropylene, acrylates, acrylonitrile, cumene, etc.
  • Butylenes: feedstock for alkylation units (high-octane alkylate), MTBE/ETBE production, or oligomerization.
  • Saturated portion: after olefin recovery, residual C₃/C₄ paraffins can serve as steam cracker feed, alkylation feed, or be blended into commercial LPG.

Distinction from SR LPG: Cracked LPG is olefin-rich and chemically reactive, whereas SR LPG is essentially olefin-free and paraffinic. This is why cracked LPG is typically routed to petrochemical recovery or conversion rather than directly to the commercial LPG pool, and why untreated cracked LPG is generally unsuitable as direct cracker feed without prior processing.