PBTC (Phosphonobutane Tricarboxylic Acid)
CAS 37971-36-1 C7H11O9P
- CAS number
- 37971-36-1
- EC number
- 253-733-5
- Formula
- C7H11O9P
- Molar mass
- 270.13 g/mol
- HS code
- 2931.49
Supply of PBTC
- Grades
- Supplied mainly as 50% aqueous acid and as sodium-salt solutions. Specified by active content, with limits on phosphorous acid, phosphoric acid, chloride and iron; standard grades are low in chloride, typically 10 ppm or less.
- Packaging
- Plastic drums (about 250 kg) · 1,000 L IBC
- Documents
- CoA, SDS and TDS on request; certificate of origin where the destination requires it.
- Delivery
- Worldwide, including the United States, Canada, the United Kingdom, Germany and the rest of the EU, the United Arab Emirates, India, Singapore, Malaysia and Australia. Quoted EXW, FOB, CIF or DAP.
PBTC is a water-treatment chemical that stops limescale from forming in cooling towers, boilers and pipes. It is used where the water is very hard or alkaline, or treated with chlorine, conditions in which similar chemicals break down or stop working. It contains less phosphorus than most similar products, which matters where phosphorus in wastewater is limited. It is also used in industrial detergents, including those for washing bottles.
Technical details
PBTC is a phosphonocarboxylic acid: one phosphonic acid group and three carboxylic acid groups on a butane chain. That combination sets it apart from HEDP and ATMP. The carboxyl groups keep PBTC and its calcium salts in solution, so it keeps working at calcium levels, pH and temperatures at which the other two precipitate, and it is the most resistant of the three to chlorine and bromine. With a single phosphorus atom it is about 11.5% phosphorus by weight, against roughly 30% for HEDP and ATMP, so the same dose adds a little over a third as much phosphorus to the discharge. It is made by adding a dialkyl phosphite to maleate and acrylate esters and hydrolysing the product, not from phosphorous acid directly, and it costs more per kilogram than HEDP or ATMP. Ehlinar supplies acid and sodium-salt grades.
Appearance: The 50% acid grade is a clear, colourless to pale-yellow liquid with a density of about 1.27–1.30 g/cm³. Sodium-salt grades are supplied as solutions.
Applications
How we supply
- Certificate of Analysis (CoA), lot-specific where available
- Safety Data Sheet (SDS / MSDS)
- Technical Data Sheet (TDS)
- Certificate of Origin / Certificate of Conformity
Independent third-party inspection can be arranged on request, with the agency and scope agreed per trade. Representative samples can be requested for qualification, subject to supplier availability. We recommend incoming quality control against the agreed CoA.
Quoted on standard Incoterms (e.g. EXW, FOB, CIF, DAP) as agreed per trade. Delivery region, packaging and grade are confirmed per quote.
Documents and services above are subject to supplier availability and confirmed per quote; nothing here is an offer.
Typical / indicative values — not a binding specification
| Property | Typical |
|---|---|
| Active content (liquid grade) | 49–51% |
| Density at 20 °C | ≥1.27 g/cm³ |
| Chloride | ≤10 ppm |
| pH (1% solution) | 1.5–2.0 |
Also known as
2-Phosphonobutane-1,2,4-tricarboxylic acid · 2-Phosphono-1,2,4-butanetricarboxylic acid · PBTCA · Phosphonobutanetricarboxylic acid
Frequently asked questions
- When is PBTC worth its higher price over HEDP or ATMP?
- When the water defeats the cheaper phosphonates: high calcium, high pH, high cycles of concentration, high temperature, or a continuous chlorine or bromine residual. It is also chosen where phosphorus discharge is limited, since it carries a little over a third as much phosphorus per kilogram. In softer, unchlorinated water HEDP or ATMP usually does the job at lower cost.
- Is PBTC used on its own?
- Often not. A common cooling-water combination is PBTC against calcium carbonate scale plus a dispersant copolymer such as AA/AMPS, which holds calcium phosphate, iron oxide and silt in suspension.
- How is the active content stated?
- As PBTC acid by weight; the standard liquid is 49–51%. Sodium-salt grades may be quoted as salt or as acid equivalent, so confirm the basis on the quote.
Enquire about PBTC
Related products
Figures and identifiers here are compiled from public references and provided for general information; they are indicative, not a specification. See all products.