{"id":1311,"date":"2026-08-08T14:22:37","date_gmt":"2026-08-08T06:22:37","guid":{"rendered":"https:\/\/bastone-petrochem.com\/?p=1311"},"modified":"2026-08-08T14:22:37","modified_gmt":"2026-08-08T06:22:37","slug":"potassium-octoate-catalyst","status":"publish","type":"post","link":"https:\/\/bastone-petrochem.com\/es\/potassium-octoate-catalyst\/","title":{"rendered":"What Is Potassium Octoate? The PIR Catalyst Explained"},"content":{"rendered":"\n

Two numbers on a drum of potassium octoate are both correct and look like they contradict each other.<\/p>\n\n\n\n

The label reads 15% potassium. The drum holds roughly 70% catalyst.<\/p>\n\n\n\n

The 15% is potassium metal by weight. The 70% is how much potassium 2-ethylhexanoate salt is actually dissolved in the glycol carrier.<\/p>\n\n\n\n

For a rigid polyisocyanurate (PIR) foam formulator sizing a trimerization catalyst, knowing which of those two numbers the dosing math needs is the difference between hitting the isocyanurate target and missing it.<\/p>\n\n\n\n

Potassium octoate earns that place through one reaction. It cyclotrimerizes isocyanate groups into isocyanurate rings, and its production route, grade label, and side jobs all follow from that.<\/p>\n\n\n\n

What Potassium Octoate Is Chemically<\/h2>\n\n\n\n

Potassium octoate is potassium 2-ethylhexanoate, the potassium salt of 2-ethylhexanoic acid. Its formula is C8H15KO2, its molar mass 182.3 g\/mol, and its CAS number 3164-85-0. In pure form it is a white, colorless solid that dissolves readily in organic solvents and can form a monohydrate.<\/p>\n\n\n\n

Potassium octoate belongs to the metal-octoate salt family<\/a>, the 2-ethylhexanoate salts used across catalysis, drying, and coatings.<\/p>\n\n\n\n

The name carries a trap worth catching before you qualify a drum. Two different acids get sold as potassium octoate: the branched 2-ethylhexanoate (CAS 3164-85-0) and the straight-chain octanoate, also called caprylate (CAS 764-71-6).<\/p>\n\n\n\n

The PIR catalyst grade is specifically the branched 2-ethylhexanoate. Supplier catalogs blur the two, with one listing 764-71-6, another 3164-85-0, and some vendor sheets calling the product caprylate outright.<\/p>\n\n\n\n

Confirm the CAS number, not just the trade name. A grade label is a starting point for qualification, not a substitute for it.<\/p>\n\n\n\n

How Potassium Octoate Catalyzes PIR Trimerization<\/h2>\n\n\n\n

Potassium octoate catalyzes the cyclotrimerization of isocyanate groups. Three isocyanate (-NCO) groups combine into a single, thermally stable isocyanurate ring.<\/p>\n\n\n\n

\"Potassium<\/figure>\n\n\n\n

That ring is the structural difference between a polyisocyanurate foam and a straight polyurethane. The isocyanurate network chars instead of melting, which carries PIR’s thermal and fire performance.<\/p>\n\n\n\n

How the Trimerization Reaction Works<\/h3>\n\n\n\n

The potassium carboxylate does the work as a base. It activates an isocyanate group, an intermediate forms, cyclization closes the isocyanurate ring, and the catalyst regenerates for the next cycle.<\/p>\n\n\n\n

Reported laboratory loadings sit around 3.2 pphp at an isocyanate index near 500, within a studied range of roughly 0.5 to 6 pphp. Raising the trimerization catalyst is reported to shorten cream, gel, and tack-free times, lift isocyanurate content, and lower thermal conductivity.<\/p>\n\n\n\n

Against an amine-type trimerization catalyst, octoate is the slower, milder option. It runs longer cream and gel times and forms coarser cells, but handles more stably and shrugs off moisture better.<\/p>\n\n\n\n

How Octoate Compares With Amine and Acetate Catalysts<\/h3>\n\n\n\n

The amine catalysts in the same formulation do a different job. They drive the gel (urethane) and blow (water-CO2) reactions, while potassium octoate drives the trimerization that builds the isocyanurate ring. A PIR system runs both, at an isocyanate index well above 100.<\/p>\n\n\n\n

Where a tin catalyst like stannous octoate<\/a> pushes the urethane gel reaction, potassium octoate pushes ring formation.<\/p>\n\n\n\n

Potassium octoate also rarely works alone. Its usual partner, potassium acetate, is not a competitor but the other trimerization salt in the blend, ratio-tuned rather than swapped.<\/p>\n\n\n\n

Trait<\/th>Potassium octoate<\/th>Potassium acetate<\/th><\/tr><\/thead>
Carrier<\/td>Diethylene glycol<\/td>Water-miscible glycol or alcohol<\/td><\/tr>
Color added<\/td>Yellow-orange<\/td>Lower<\/td><\/tr>
Ring-forming onset<\/td>Milder, slower<\/td>Higher efficiency (reported)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Blending lets a formulator dial reactivity between octoate’s later onset and acetate’s faster ring formation without touching anything else in the system. Swapping one for the other in a running formulation changes carrier and color load at once, so re-check the cure profile before you do it.<\/p>\n\n\n\n

How Potassium Octoate Is Made and Why It Ships in DEG<\/h2>\n\n\n\n

Potassium octoate is made by neutralizing 2-ethylhexanoic acid with a potassium base, then diluting the salt in a diethylene glycol (DEG) carrier for catalyst use. The core reaction is a plain acid-base neutralization: 2-ethylhexanoic acid plus potassium hydroxide gives potassium 2-ethylhexanoate and water.<\/p>\n\n\n\n

\"Production<\/figure>\n\n\n\n

Reference procedures describe adding roughly 50% aqueous KOH to the acid over about two hours, letting the exotherm climb from ambient to near 45 C under cooling. The finished solution carries around 1% water.<\/p>\n\n\n\n

The feedstock is the anchor of the whole route. This can be sourced against 2-ethylhexanoic acid (CAS 149-57-5)<\/a>, the same branched C8 acid behind every metal octoate.<\/p>\n\n\n\n

Neat potassium octoate is a solid, and a solid is a poor way to meter a catalyst. Dissolving it to a concentrated solution in diethylene glycol gives a pumpable, dust-free liquid that disperses evenly into the polyol side and doses to spec.<\/p>\n\n\n\n

The carrier is not inert background in the dosing math. It is most of what sits in the drum.<\/p>\n\n\n\n

How to Read a Potassium Octoate Grade Label<\/h2>\n\n\n\n

The percentage on a potassium octoate grade label is potassium metal by weight, not the amount of catalyst salt in the drum. A grade sold as 15% K in DEG holds about 70% actual potassium 2-ethylhexanoate by weight; the 15% counts only the potassium atoms.<\/p>\n\n\n\n

\"How<\/figure>\n\n\n\n

The arithmetic behind that is fixed. Pure potassium 2-ethylhexanoate is only 21.4% potassium by weight, because the 39.1 mass of the potassium atom is a small share of the 182.3 molar mass. A solution assaying 15% potassium therefore carries about 70% salt, the balance being the DEG carrier.<\/p>\n\n\n\n

Umicore states its VALIREX K 15 DEG grade at 71 wt% concentration, and PIR literature describes commercial octoate as a roughly 70% solution in diethylene glycol. The computed figure and the datasheet agree.<\/p>\n\n\n\n

Grade<\/th>K metal<\/th>Carrier<\/th>Viscosity<\/th>Water<\/th><\/tr><\/thead>
VALIREX K 15 DEG (Umicore)<\/td>15%<\/td>DEG<\/td>~5000 mPa.s, RT<\/td>4%<\/td><\/tr>
15% Potassium Hex-Cem (Borchers)<\/td>14.9-15.2%<\/td>DEG<\/td>3000-6000 mPa.s, 20 C<\/td>3.0-4.5%<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

The two brands list the same 15% K in DEG grade through different test standards, which is why their viscosity windows do not line up.<\/p>\n\n\n\n

For dosing, the 70% salt figure is the number that governs the calculation. Size the catalyst on potassium 2-ethylhexanoate content, and a grade change that holds 15% K while shifting carrier or water spec will not surprise your cream time.<\/p>\n\n\n\n

Be wary of vendor tables quoting 18 to 22% active potassium. Those describe a salt-content grade, not the 15% metal-assay datasheet, and mixing the two conventions is exactly how a dosing number goes wrong. The COA number you dose against is the salt content, not the metal assay printed on the drum.<\/p>\n\n\n\n

Where Potassium Octoate Is Used Beyond PIR Foam<\/h2>\n\n\n\n

Potassium octoate has two roles outside PIR foam. It works as a co-accelerator in unsaturated polyester gelcoats and as a corrosion-inhibitor component in some coolant packages.<\/p>\n\n\n\n

Co-Accelerator in Polyester Gelcoats<\/h3>\n\n\n\n

In unsaturated polyester resins and gelcoats, potassium octoate works as a co-catalyst that boosts cobalt performance and cuts the color the cured composite picks up. It lets the cobalt octoate<\/a> drier reach the same cure at a lower cobalt level. Cobalt in these systems typically runs 0.005 to 0.020% as metal.<\/p>\n\n\n\n

A reformulation trend runs alongside this role. Umicore now offers 2-EHA-free potassium grades, its VALIKAT K line, introduced to address toxicity concerns around 2-ethylhexanoic acid and its metal salts while keeping the same cobalt-boost and color-reduction function.<\/p>\n\n\n\n

Corrosion Inhibitor in Coolants<\/h3>\n\n\n\n

Potassium 2-ethylhexanoate also appears in some antifreeze and coolant formulations as a corrosion inhibitor<\/a>, where the carboxylate protects metal surfaces rather than catalyzing a reaction. That role is chemically unrelated to trimerization, and it should not drive a grade choice made for PIR foam.<\/p>\n\n\n\n

What This Means for Your Formulation<\/h2>\n\n\n\n

Buy potassium octoate on two numbers, not one. The CAS 3164-85-0 confirms you have the branched 2-ethylhexanoate that actually catalyzes trimerization, and the salt content behind the metal assay is what your dosing keys on.<\/p>\n\n\n\n

The trimerization job is the whole reason the drum exists. The isocyanurate ring it builds is what earns PIR its char and fire performance, and the DEG carrier, the 15% label, and the gelcoat crossover all follow from that one reaction.<\/p>\n\n\n\n

Read the grade right and potassium octoate stops being a mystery liquid. It becomes a spec you can qualify, substitute, and defend.<\/p>\n\n\n\n