Short answer: if your process has a catalyst or a colour specification, buy refined. If naphthalene is a feedstock you will purify or sulphonate yourself, crude is almost always the better commercial decision.
Crude and refined naphthalene are the same compound — C₁₀H₈, CAS 91-20-3. Neither is a different chemical, and a specification sheet showing the same CAS number for both is not an error. What separates them is how far the material has been taken past the coal tar still, and that processing difference shows up in three numbers that matter commercially: sulphur content, crystallisation point, and price per tonne.
Where each grade comes from
Crude naphthalene is recovered directly from the fractional distillation of coal tar. At that point it still carries sulphur compounds — thionaphthene chiefly — along with other aromatic impurities that came through with it. Typical purity sits above 95%, with sulphur up to 1.5%, and it is supplied as flakes or solid blocks.
Refined naphthalene takes that same crude material through additional purification: acid washing, alkali treatment, and re-crystallisation. Those steps strip the sulphur down to 0.1% or lower and lift purity to between 99% and 99.9%. The result is a white crystalline flake or powder with a materially higher crystallisation point.
The specification difference
| Property | Crude Naphthalene | Refined Naphthalene |
|---|---|---|
| CAS Number | 91-20-3 | 91-20-3 |
| Purity | > 95% | 99% – 99.9% |
| Sulphur Content | ≤ 1.5% | ≤ 0.1% |
| Moisture Content | ≤ 0.3% | ≤ 0.05% |
| Melting Point | ≥ 77 °C | ≥ 79.5 °C |
| Crystallisation Point | — | ≥ 79.4 °C |
| Form | Flakes / Blocks | White crystalline flakes / powder |
| Typical Packaging | 25 kg & 40 kg bags | 25 kg bags |
Typical values. Actual figures are confirmed on the Certificate of Analysis for each lot.
Crystallisation point is the number experienced buyers check first, because it is the most honest single indicator of purity. Pure naphthalene crystallises at about 80 °C; every impurity depresses that figure. A refined lot quoted at ≥79.4 °C is telling you something specific about how little else is in the drum. A crude lot has no meaningful crystallisation specification at all, which is exactly what you would expect.
Where crude naphthalene is the right buy
Crude is the correct choice wherever the naphthalene is going to be chemically transformed anyway, and where residual sulphur either does not interfere or is removed downstream:
- As feedstock for refined naphthalene production — refiners buy crude by definition
- Naphthalene sulfonate manufacture, including sulphonated naphthalene formaldehyde (SNF) concrete superplasticizers
- Moth repellent and naphthalene ball production, where reagent-grade purity is irrelevant
- Tanning and leather processing auxiliaries
- General chemical synthesis where the sulphur level is tolerable or handled in a later step
Buying refined for any of these is paying a purification premium for a property the process does not use. On a full container load, that difference is not trivial.
Where refined naphthalene is worth the premium
Refined becomes necessary once sulphur or colour carries a real cost:
- Phthalic anhydride (PA) production — the vanadium catalyst is sulphur-sensitive, and crude will shorten its life
- Dyes and pigments, where any colour body carried through the impurities shows up in the finished shade
- Beta-naphthol synthesis and downstream fine chemicals
- Agrochemical and specialty chemical intermediates working to tight assay specifications
- Any process where the customer specification names a crystallisation point
The phthalic anhydride case is the clearest. PA plants run fixed-bed vanadium pentoxide catalyst, and sulphur is a known poison. The cost of replacing a catalyst bed early dwarfs whatever was saved on the naphthalene, which is why PA producers specify refined grade almost without exception.
A note on sourcing origin
The two grades do not come from the same places, because the processing economics differ. Crude naphthalene is recovered wherever coal tar is distilled at scale — Russia, Indonesia, India and Europe are the practical origins. Refined capacity is concentrated more narrowly; China and Indonesia supply the bulk of internationally traded refined naphthalene. That matters for lead time and freight planning more than most buyers expect: the two grades of what looks like one product can sit on entirely different shipping routes.
How to decide
Work backwards from your process rather than from the price list. Ask three questions in order. Does anything in the process involve a catalyst? If yes, refined. Does the finished product have a colour or assay specification a customer will test against? If yes, refined. If neither — and the naphthalene is being sulphonated, transformed, or sold into an application with no purity-driven failure mode — crude will do the same job for less.
If you are genuinely unsure, the practical step is to send the specification you have been given, rather than the grade name. Grade names travel badly between markets; a specification sheet does not. First Chemicals supplies both grades and can confirm which one a given specification actually calls for, with the Certificate of Analysis and MSDS for the matching lot.