Paraxylene: Production route
How plants split molecules that boil a degree apart
What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.PX is made in aromatics complexes that take reformate from refinery naphtha and maximise xylenes. The key steps are separation of PX from its isomers, which have nearly the same boiling point, and isomerisation of the leftover xylenes back into PX. Toluene and heavy aromatics are converted into more xylenes to raise yield. New Chinese complexes are 2-4 Mt/yr each, built in about 30 months at about 20% lower cost than elsewhere in Asia (Argus).
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| Adsorptive separation with isomerisation (Parex, Eluxyl) | about 85-90% of capacity (indicative) | about 2.5-3.5 t heavy naphtha per t PX depending on complex design, with benzene and hydrogen co-products (indicative) | 1-4.5 Mt/yr; Gulei 3.2 Mt/yr (Argus) | PX purity 99.7-99.9% | benzene, hydrogen, raffinate, fuel gas | naphtha plus about $100-150/t processing (indicative); margin is the PX-naphtha spread, $283/t in 2024 (Argus) |
| Crystallisation | about 10% (indicative) | refrigeration energy is the main extra cost (indicative) | 0.2-0.6 Mt/yr | lower recovery than adsorption from equilibrium xylenes | as above | higher than adsorption at scale (indicative) |
| Toluene conversion (selective disproportionation, transalkylation) | contributes to most capacity (indicative) | about 2-2.5 t toluene per t PX via selective disproportionation, with benzene co-product (indicative) | 0.5-2 Mt/yr | PX-rich xylenes | benzene | toluene price plus conversion |
| Toluene methylation and bio-PX | below 1% (indicative) | not published | pilot to 0.2 Mt/yr | not published | water | not published; well above fossil PX |
How each route works
Adsorptive separation with isomerisation (Parex, Eluxyl)Mixed xylenes pass through a simulated moving bed of zeolite adsorbent that selectively holds PX, recovering over 97% per pass. The PX-depleted stream is isomerised back to an equilibrium mix and recycled. This loop is the core of almost all modern complexes.
Highest yield and scale; capital-intensive and tied to refinery integration.
Argus, May 2025; indicative CrystallisationPX freezes at 13 C, well above other xylenes, so chilling mixed xylenes crystallises PX for separation. Used in older plants and for high-PX streams from selective toluene disproportionation.
Simple; efficient only on PX-rich feed.
indicative Toluene conversion (selective disproportionation, transalkylation)Not a separation route but a feed booster: toluene and C9 aromatics are converted over zeolites into benzene and xylenes, with selective processes giving a PX-rich xylene stream. Integrated in most complexes.
Raises PX yield per barrel; makes benzene as a co-product.
indicative Toluene methylation and bio-PXToluene reacted with methanol gives PX directly (some Chinese coal-to-chemicals plants). Bio-PX from sugars or biomass (Virent, Anellotech) has been demonstrated at small scale.
Methanol route links to coal; bio route is far from cost parity.
indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.