Material Insights · Understanding the Material World

Paraxylene and Toluene

Toluene is the main swing feed for extra paraxylene: transalkylation and disproportionation units turn toluene, often mixed with heavier aromatics, into xylenes and benzene, and can more than double the paraxylene an aromatics complex makes from the same naphtha. Whether toluene goes there or into petrol depends on the spread between them.

Paraxylene (chemical) and Toluene (chemical): 3 relationships.

How they are linked

1. Converted to xylenes

Physical flow · Strong · Toluene to xylenes and paraxylene

These units move methyl groups between aromatic rings: toluene alone gives benzene and xylenes, and adding C9 aromatics tilts output towards xylenes.

  • 31.5% and 22.0% benzene and xylene at equilibrium, pure toluene feed (mol)
  • 4.5% and 45.0% benzene and xylene, 50:50 toluene and C9 feed (mol)

Standard disproportionation gives roughly equal benzene and xylenes, while selective versions give a paraxylene-rich stream. Transalkylation with C9 feed sharply cuts benzene, which is why it has gained ground on plain disproportionation.

Sources: Portfolio Planning PLUS; ICIS

2. Lifts paraxylene yield

Physical flow · Strong · Toluene conversion feeds the PX loop

Inside an aromatics complex the xylenes made from toluene go to the paraxylene separation loop, adding to the xylenes that come straight from the reformer.

  • about 50% of xylene output from an integrated aromatics complex comes from transalkylation
  • 40% paraxylene increase from a toluene-only unit (200 to 280 kt/yr)
  • 110% increase with toluene plus C9 feed (to about 420 kt/yr)

For the same naphtha, a complex with a toluene and C9 unit makes about twice the paraxylene of one without. That makes toluene supply, and how much is kept for chemicals rather than petrol, a direct limit on paraxylene output.

Sources: IHS Markit (S&P Global); Portfolio Planning PLUS

3. Petrol or paraxylene

Substitution · Medium · Toluene's other use is petrol blending

Toluene is a high-octane petrol component, so it goes into conversion only when the spread to benzene and xylenes beats its value in petrol.

  • nearly half of toluene consumed went to benzene, mixed xylenes and PX, 2021
  • 20 cents/gal minimum premium US conversion operators looked for, 2016
  • 44% share of US chemical toluene use in disproportionation, 2016

Most toluene stays in refinery streams for petrol, and US traders watch toluene, benzene and xylene spreads to decide conversion runs. After new paraxylene capacity started in Northeast Asia, Southeast Asia and India, toluene use in disproportionation fell while use in transalkylation rose.

Sources: IHS Markit (S&P Global); ICIS

For investors

Key learnings

  1. Transalkylation supplies around half of a complex's xylenes, so toluene availability shapes how much paraxylene a refinery can make.
  2. Adding C9 aromatics to toluene cuts benzene and lifts xylenes, and the toluene, benzene and xylene spreads decide unit run rates.
  3. Toluene's floor is its petrol value; when petrol blending pays more, operators cut conversion, which can tighten paraxylene supply.

What to track

  • Paraxylene to toluene spread, Asia: Margin for conversion; narrowing cuts disproportionation runs (Weekly · Platts, ICIS)
  • Toluene against petrol blendstock spread: Opportunity cost of converting toluene (Weekly · Platts)
  • Benzene to toluene spread: Decides the benzene against xylene output mix (Weekly · Platts)

For policymakers

Key learnings

  1. A refinery aromatics complex with toluene and C9 conversion can more than double paraxylene from the same naphtha, which matters for polyester self-sufficiency plans.
  2. Because toluene is also a petrol octane booster, fuel demand and quality changes shift how much is free for chemicals.
  3. Toluene use in stand-alone disproportionation has fallen as new paraxylene complexes started in Asia and India, while transalkylation has grown.

What to track

  • India paraxylene capacity and imports: Self-sufficiency in the polyester chain (Annual · MoPNG, DGCI&S)
  • Petrol demand and octane specifications: Competing call on toluene (Annual · PPAC)

India

India is among the places where new paraxylene capacity started up, after which toluene use in disproportionation units declined and transalkylation grew.

Sources

  1. PEP Review 2018-07: UOP two-stage Tatoray process, IHS Markit (S&P Global) (2018)
  2. Tatoray process: toluene disproportionation and transalkylation, Portfolio Planning PLUS
  3. Toluene: Chemical Economics Handbook (abstract), IHS Markit (S&P Global) (2022)
  4. OUTLOOK '17: US toluene to track gasoline, aromatics, ICIS (2016)