Naphtha
Two buyers want the opposite molecule.
Light, full-range and heavy naphtha into steam crackers and catalytic reformers — where the cracker pays for paraffins and the reformer pays for naphthenes and aromatics, so the same density can be the best cargo on the market or the wrong one entirely.
The desk
Naphtha is the one product where density tells you almost nothing.
Two naphtha cargoes can share a specific gravity, a boiling range and a sulphur content, and be worth materially different money — because what the buyer is really purchasing is the molecular composition underneath, and the two main buyers want opposite things from it.
A steam cracker wants paraffins. Straight-chain paraffins crack cleanly to ethylene and propylene; aromatics largely pass through, take up furnace capacity and end up in the pyrolysis gasoline. A catalytic reformer wants the opposite: naphthenes it can dehydrogenate into aromatics, and aromatics already there, because reformate value is aromatic value.
So the first question on a naphtha enquiry is not the density. It is which unit it feeds. From there the specification follows — paraffin content for one, naphthenes and aromatics for the other, and for both an entirely separate list of trace contaminants that decide whether the catalyst survives the cargo.
Composition
PNA, and the correlations built on it.
Naphtha composition is reported as paraffins, naphthenes and aromatics — and, where the buyer needs the detail, as full PIONA including iso-paraffins and olefins. It is the analysis that actually prices the cargo.
| Fraction | Cracker | Reformer |
|---|---|---|
| Normal paraffins | The prize. Highest ethylene yield per tonne of feed. | Low value — they must be isomerised or dehydrocyclised first, and some simply crack. |
| Iso-paraffins | Good, though a little less than normal paraffins for ethylene. | Modest. |
| Naphthenes | Moderate. | The prize. Dehydrogenate readily to aromatics, which is the reformer's whole purpose. |
| Aromatics | Largely inert through the furnace — they occupy capacity and report to pyrolysis gasoline rather than to ethylene. | Already the product. They arrive as value. |
| Olefins | Present in cracked naphthas; a stability and fouling concern rather than a benefit. | Undesirable — they consume hydrogen and promote coking. |
Steam cracker feed
Naphtha is the dominant liquid cracker feedstock outside the ethane-advantaged regions, and it is what makes a naphtha cracker's product slate broader than an ethane cracker's — propylene, butadiene and aromatics alongside ethylene, rather than ethylene almost alone.
Paraffinicity is the value driver. Beyond it, the boiling range has to suit the furnace: too light and the parcel is really an LPG-range material the furnace is not configured for; too heavy and the end point drives coking in the radiant coils and shortens the run between decokes. A cracker's tolerance on final boiling point is specific to its design, which is why a full distillation belongs on the offer.
- What a cracker specifies
- Total paraffins, and often the full PIONA; density; initial and final boiling point with the full curve; sulphur; and the contaminant set below.
- Cracked versus straight-run
- Straight-run naphtha is the reference feed. Cracked naphthas carry olefins and different contaminants and are not a drop-in substitute for a unit that was not designed for them — a distinction we state rather than leave to the density.
- Why sulphur is not simply a poison here
- Crackers often dose sulphur deliberately to passivate coil metallurgy against catalytic coking. Very low sulphur is therefore not automatically preferable — another product where the buyer works to a window rather than a minimum.
Catalytic reformer feed
Heavy naphtha, hydrotreated, into a reformer to make aromatics and high-octane reformate — and hydrogen, which for many refineries is the more important product of the two.
The cut matters in both directions. Light naphtha is deliberately excluded because at reforming conditions it cracks to lighter products instead of reforming; material that is too heavy is excluded because it accelerates catalyst deactivation through coking. The reformer feed cut is therefore narrower than a general "heavy naphtha" description implies, and a parcel that is nominally heavy naphtha can still be the wrong cut.
- What a reformer specifies
- N+2A or the full PNA; the distillation cut with both ends held; and the poison set below, at very low limits.
- Why the poison limits are so tight
- Reforming catalyst is platinum-based. It is expensive, it is poisoned irreversibly by certain metals, and a single contaminated cargo can shorten a cycle. That asymmetry — cheap test, expensive failure — is why this is the fussiest naphtha buyer in the market.
- Hydrotreated or not
- Stated explicitly. Whether the parcel has been through a naphtha hydrotreater changes both its sulphur and its metals position, and it is not something to infer.
Contaminants
The list that is not on a standard certificate.
Naphtha's routine specification is short and reassuring. The parameters that destroy value are trace metals and heteroatoms that a general assay does not report unless specifically requested — which is precisely why they cause the losses they do.
| Contaminant | What it does | Who cares most |
|---|---|---|
| Arsenic | An irreversible poison to reforming catalyst. Removed upstream in a hydrotreater; if it arrives in the cargo, it arrives in the catalyst. | Reformers, absolutely |
| Lead and copper | Catalyst poisons. Lead is also a marker of contamination from prior service or a blended-in stream of uncertain history. | Reformers |
| Mercury | Attacks aluminium in cryogenic service and poisons catalysts. The same mechanism described on our condensate page, and just as absent from a routine naphtha certificate. | Crackers, especially |
| Silicon | From antifoam carried over upstream. Poisons hydrotreating catalyst and is difficult to remove. A recurring problem with cracked and unconventional streams. | Both |
| Chlorides, organic and inorganic | Convert to hydrochloric acid downstream, corroding overheads and, in a reformer circuit, upsetting the chloride balance the catalyst depends on. | Both |
| Nitrogen | Neutralises acid function on reforming catalyst and consumes hydrotreating capacity. | Reformers |
| Oxygenates | MTBE or ethanol carried over from gasoline service in a shared tank or line. Damaging and entirely avoidable, which makes tank history a specification item. | Both |
Cuts
What we supply.
Light naphtha
The light end, broadly C5–C6. Isomerisation feed, gasoline blending volume, and petrochemical service. Volatile — vapour pressure is a real handling parameter, not a formality.
Full-range naphtha
The standard traded cut and the usual cracker feed. Sold on paraffinicity and the full distillation curve.
Heavy naphtha
Reformer feed. Sold on N+2A and the cut, with the poison set at low limits and the hydrotreated status stated.
Open-spec naphtha
Traded against a market-standard description rather than a buyer's table. We will tell you plainly what an open-spec parcel is and is not: it is a commercial convention, and it does not carry the PNA or trace analysis a plant needs. If your unit has real constraints, buy to your own specification instead.
Parcels and basis
Clean-product tankers, FOB, CFR, CIF or delivered to a nominated terminal. Term programmes where a cracker wants a consistent feed rather than a series of unrelated cargoes.
Pricing
Against the relevant regional naphtha assessment, with the quotation period and the publication named in the contract rather than assumed.
Carriage
Clean cargo, and the tank history is part of the specification.
Naphtha is light, low-viscosity and colourless, and it picks up whatever a tank or line last held far more readily than a heavier product would. On a cargo whose value sits in trace analysis, that is a quality issue rather than a housekeeping one.
| Item | Position |
|---|---|
| Tank history | Three-cargo history requested as standard, and refused where the previous service was leaded, oxygenated or metal-bearing. This is the single most effective contamination control available and it costs nothing. |
| Vapour pressure and loading temperature | Recorded. Light naphtha in particular loses light ends and gains vapour pressure problems if loaded warm. |
| Vessels | Clean-product and parcel tankers with coated or stainless tanks according to the grade and the buyer's requirement. |
| Inspection | Independent at load and discharge, sampling under supervision, sealed retains at both ends. |
| Quantity | Ship's figures, shore figures and vessel experience factor, with the governing figure named in the contract. |
Scope
Where our obligation ends.
- What we supply
- Naphtha as seaborne cargo parcels with the composition and trace analysis the destination unit needs.
- We do not hydrotreat, isomerise or reform
- We operate no units. Where a parcel needs treatment to meet your poison limits, that is a plant matter and we will say so rather than implying we can adjust the cargo.
- We do not warrant your yields
- We give you the PNA, the distillation and the trace set. What your furnace or your reformer makes of it is yours to model, and an offer that promises an ethylene yield is promising something the seller does not control.
- Origin
- Screened per consignment. Declined where it cannot be documented — see Compliance.
How to specify
Six lines and we can price it.
Naphtha enquiries arrive as a gravity and a tonnage, which is the least informative pair of numbers in this product.
Which unit it feeds
Steam cracker, reformer, isomerisation unit or gasoline blending. This decides everything else.
Composition target
Minimum total paraffins for a cracker, or minimum N+2A for a reformer. A range rather than a point.
The cut
Initial and final boiling point, and whether your unit is constrained at the heavy end. Full curve preferred.
Trace ceilings
Arsenic, lead, copper, mercury, silicon, chlorides, nitrogen — whichever your unit holds. Say if you want them reported even without a limit.
Sulphur, as a window
Maximum, and a minimum if your furnace uses sulphur for coil passivation.
Quantity, basis and terminal
Tonnes, FOB / CFR / CIF / delivered, tank coating and any previous-cargo restriction you impose.
Quality
The analysis that prices the cargo.
Independent inspection by an agency appointed for the cargo — SGS, Bureau Veritas or Intertek — instructed jointly, with sampling under supervision and sealed retains at both ends.
On naphtha the certificate has to go beyond the routine set, because the routine set does not describe what the buyer is buying. A density, a distillation and a sulphur figure describe a fluid. A PNA analysis and a trace-metals scan describe a feedstock.
- Core test set
- Density at 15 °C; full distillation; vapour pressure where the grade warrants it; total sulphur; mercaptan sulphur; doctor test; colour; copper corrosion; water content.
- Composition
- PNA as standard, full PIONA where the buyer works from it.
- Trace analysis
- Arsenic, lead, copper, mercury, silicon, total and organic chloride, and total nitrogen — each by its dedicated method rather than inferred from a general scan.
- Missing determinations
- Chased or independently run before offer. On this product a blank in the trace set is the blank that matters.
- Documentation per parcel
- Certificate of Quality, Certificate of Quantity, Certificate of Origin, safety data sheet in the destination language, bill of lading, three-cargo tank history and the independent inspection report.
Straight answer
What we will tell you before you ask.
- That gravity is not a specification here
- Two parcels at the same density can differ in paraffin content enough to change your yields materially. We quote the composition, and we treat a naphtha offer without one as incomplete.
- That open-spec is a commercial term, not a technical one
- It is a legitimate way to trade and a poor way to feed a plant with real constraints. We will tell you which you are doing.
- That the trace metals are the expensive parameters
- Arsenic in a reformer and mercury in a cracker cost far more than the cargo. They are cheap to test and absent from most certificates, so we put them on ours.
- That tank history is a quality control
- Leaded, oxygenated or metal-bearing previous service on a naphtha parcel is a reason to decline the tank, not a detail to note. We ask for three cargoes back.
- Where an origin cannot be cleared
- Screened per consignment; declined where it cannot be documented, and not referred onward — see Compliance.
Enquiries
Every enquiry is answered by the desk that handles it.
Send the product, quantity, delivery basis, destination and timing. We revert with availability, an indication and the documentation that accompanies it. Specifications are released once we know who we are speaking with.