Reactive Monomer Applications

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Prism® Styrene Polymerization Inhibitors

To control unwanted polymerization in styrene purification train, the stream sent to purification requires a chemical treatment, but even with this, the styrene losses due to polymerization may be relevant.

In liquid phase, styrene polymerizes without any initiating agent. In order to control the unwanted styrene polymerization and degradation, the common industrial practice is to treat the stream sent to the purification section with a polymerization retarder. Typical commodity products are different kinds of dinitrophenols (DNOC, DNBP, DNOP, DNP); in the past, sulpher was used.

The key objective of every chemical treatment in this area of the plant is to contain polymer growth, reducing styrene monomer losses, maintaining system control in emergency conditions where runaway styrene polymerization could occur.

Companies initially targeted the use of effective chemistry kinetics to minimize unwanted polymerization. These chemistries were defined as “true inhibitors” to differentiate them from the “old inhibitors,” or retarders used previously. True inhibitors were of interest because they could be added to the traditional chemistries used, without interfering with the long term effectiveness of the latter.

A true inhibitor reacts irreversibly and very quickly with the radicals in the system. It can totally inhibit polymerization while it’s present, however, it will be totally consumed in a static test with additive replenishment. As per the graph below, once the inhibitor is consumed, the polymerization resumes at the untreated rate.

The old retarder undergoes a slow, reversible reaction that moves to equilibrium in the static test. The retarder slows down the polymerization rate, but does not eliminate polymer formation. Because of typical high dosage levels and slow reaction kinetic, it lasts longer than inhibitors in the system.

Di-nitro-phenols commonly used in the industry are a classic example of retarders.

Nalco’s true inhibitors are unique and all are part of the Prism® program.

Contact us for more details about the successes achieved by this technology and how we can put it to work for your plant.