Pyrolysis technology transforms difficult-to-recycle solid wastes — such as waste plastics and waste tyres — into liquid oil products. As a result, the global waste recycling industry is paying increasing attention to this approach. However, raw pyrolysis oil is not a uniform product. Instead, it is a mixed hydrocarbon liquid with a wide boiling range and complex composition. Through distillation, operators can separate it into two distinct fractions: naphtha and non-standard diesel. Understanding the differences between these two products is therefore fundamental for pyrolysis companies developing product strategies and expanding into downstream markets.
During pyrolysis, long-chain organic molecules break down and recombine, producing a three-phase output of gas, liquid, and solid. The liquid phase — pyrolysis oil — contains hydrocarbons ranging from C4 to above C30. Because of this broad carbon number distribution, pyrolysis oil naturally lends itself to fractional distillation by boiling point.
Industrial distillation works on a simple principle: hydrocarbon molecules of different carbon chain lengths boil at different temperatures. By controlling the distillation temperature, operators can therefore separate fractions by boiling range. In pyrolysis oil processing, producers typically set the cut point at 180°C–220°C, though this varies by equipment and target specification:
The output ratio between the two fractions is not fixed. Instead, several key variables influence it:
Separated from the same batch of pyrolysis oil, naphtha and non-standard diesel differ significantly in physical properties, chemical composition, end uses, and pricing logic. The table below summarises the key differences.
| Parameter | Naphtha (Light Fraction) | Non-Standard Diesel (Heavy Fraction) |
|---|---|---|
| Appearance | Light yellow to near-colourless, clear and transparent | Dark yellow to brownish, slightly turbid |
| Boiling Range | Approx. 30–200°C | Approx. 200–360°C |
| Primary Carbon Numbers | C5–C10 | C10–C22 |
| Density (20°C) | 0.65–0.75 g/cm³ | 0.82–0.87 g/cm³ |
| Flash Point | Below 28°C (Class A flammable liquid) | 55°C–80°C |
| Kinematic Viscosity (40°C) | Very low, excellent flowability | 2–8 mm²/s, close to standard diesel |
| Primary Hydrocarbon Composition | Alkanes, olefins, aromatics (high BTX content) | Primarily alkanes and cycloalkanes, lower aromatics |
| Main Uses | Petrochemical feedstock, solvent oil raw material, gasoline blending component | Industrial boiler/kiln fuel, power generation fuel, heavy machinery fuel |
| Downstream Buyers | Chemical companies, solvent oil producers, blending traders | Industrial fuel consumers, fuel distributors |
| Transport Compliance | Class A flammable liquid; strict hazardous goods transport requirements | Class C fuel; relatively lower transport compliance threshold |
| Upgrading Pathway | Hydrodesulphurisation + diolefin removal → chemical-grade naphtha | Hydrotreating + desulphurisation → on-spec diesel |
Pyrolysis naphtha is rich in aromatics and light hydrocarbons, giving it several potential industrial applications. However, its high olefin content and complex impurity profile mean that buyers typically need either in-house refining capability or a defined tolerance for feedstock variability.
This accessible market tolerates non-conventional feedstocks well. Rich in benzene, toluene, and xylene, this naphtha provides excellent solvency for degreasers, coatings, and ink thinners. Processors buy it directly for blending or simple distillation, grading and selling it as solvent oil.
For aromatic-rich streams like waste tyre naphtha (20–40% BTX), isolation via extraction or distillation yields the highest value. These aromatics serve as precursors for styrene, resins, and dyes. However, strict quality needs and specialized equipment limit its current commercial scale.
High aromatic content offers strong octane potential, making this naphtha theoretically viable for specialized fuel blending. However, strict automotive standards limit benzene, olefins, and vapour pressure. Without prior hydrotreatment, it cannot directly enter commercial road-use gasoline streams.
Long-term, hydrotreating to remove olefins, sulphur, and nitrogen upgrades the product into chemical-grade naphtha. This premium feedstock supplies ethylene and propylene crackers, accessing high supply-chain value. However, massive capital requirements restrict this route to large-scale operations.
Compared to naphtha, non-standard diesel has a narrower but more predictable range of applications, concentrated in industrial fuel markets. Its higher boiling range and relatively stable chemistry make it a workable fuel. However, elevated sulphur content shuts it out of road transport and other regulated fuel markets, confining it to industrial settings where sulphur emission requirements are less stringent.
This massive, stable outlet serves heavy industries like steel and paper. These sectors prioritize calorific value over strict sulphur limits, especially with desulphurisation systems. Offering comparable heat output at a discount, this diesel is highly attractive to high-volume industrial consumers.
Diesel generator sets in mining, ports, and remote areas provide another major application. These settings feature flexible fuel specifications and on-site storage. Facilities with captive power stations offer stable, long-term procurement, making them excellent direct-supply channels for pyrolysis producers.
Inland waterway vessels historically utilized this fuel under less stringent emission limits. However, as international and regional maritime regulations tighten globally, the compliant market window for unrefined diesel is narrowing. Producers targeting marine channels must closely monitor local port authority requirements.
Off-road machinery, including excavators and agricultural tractors, faces less rigorous fuel enforcement than on-road vehicles. Cost-conscious contractors frequently purchase this diesel to lower operating expenses. Though fragmented, this segment aggregates substantial volume, typically flowing through local intermediary traders.
When pyrolysis oil enters industrial markets, buyer trust—not price—is the primary barrier. Scepticism surrounding waste origins, batch consistency, and long-term reliability creates a distinct trust gap that varies across different oil fractions.
Pyrolysis oil products face compliance challenges across all major markets. Regulatory frameworks vary widely in maturity, creating significant uncertainty for both cross-border sales and local operations.
Pyrolysis oil fits neither conventional fossil fuel nor renewable energy definitions. This ambiguity complicates customs classification, taxation, sales licensing, and environmental assessments. Companies must negotiate with regulators case-by-case across jurisdictions, which heavily increases compliance costs and operational lead times.
Major global economies continue tightening sulphur limits for transportation and industrial fuels. Pyrolysis diesel typically exceeds these ultra-low thresholds by multiple orders of magnitude. Without specialized hydrodesulphurisation treatment, this product lacks any viable, legally compliant sales channels within these premium markets.
Naphtha’s low flash point classifies it globally as a dangerous good under UN packaging, labelling, and transport regulations. Cross-border shipments add complex compliance layers. Meanwhile, non-standard diesel faces lower transport hurdles, though bulk storage facilities must satisfy strict fire prevention rules.
Frameworks like Europe’s RED III qualify waste-derived oil for lucrative advanced biofuel incentives. However, unlocking these policy premiums demands rigorous feedstock traceability and full lifecycle carbon accounting. Most pyrolysis producers currently lack the comprehensive documentation required to pass these near-term audits.
Pyrolysis diesel and naphtha reflect divergent pathways, but share one core logic: closer alignment with standard specifications unlocks stronger pricing power. Long-term competitiveness depends on refining depth rather than volume. As global circular economies advance, rising compliance thresholds are squeezing low-end markets. Producers integrating hydrotreating and quality certification will successfully transition from simple waste processors into highly valued, legally recognized recycled oil suppliers.