Online monitoring of TBC in styrene storage tanks according to ASTM D4590
AN-PAN-1027
2026-02
it
Reliable monitoring of TBC in styrene according to ASTM D4590 requires an explosion-proof solution like the 2060 TI Ex Proof Analyzer.
Nella produzione di stirene, butadiene e acetato di vinile, lo stabilizzante 4-terz-butilcatecolo (TBC) svolge un ruolo cruciale nel prevenire la polimerizzazione prematura durante lo stoccaggio e il trasporto.
Per garantire la qualità del prodotto, la concentrazione di TBC nello stirene deve essere mantenuta al di sopra di 10-15 mg/L. È necessario un attento monitoraggio della concentrazione per controllare i livelli di TBC.
Questa nota applicativa di processo presenta una soluzione per la determinazione colorimetrica online di TBC nello stirene (secondo ASTM D4590) con 2060 TI Ex Proof Process Analyzer di Metrohm Process Analytics.
Ogni anno nel mondo vengono prodotte più di 27 milioni di tonnellate di monomero di stirene (C6H5CH=CH2) [1]. Lo stirene e altri monomeri reattivi, come il butadiene e l'acetato di vinile, sono intrinsecamente instabili durante lo stoccaggio e il trasporto a causa della loro tendenza a subire una polimerizzazione spontanea quando esposti a fattori ambientali come calore, luce o ossigeno.
Per mitigare questo rischio vengono aggiunti stabilizzanti chimici come il 4-tert-butylcatechol Il TBC agisce come inibitore dei radicali liberi, prevenendo la formazione di lunghe catene polimeriche che possono causare variazioni di viscosità, ostruzioni o persino reazioni incontrollabili nei serbatoi di stoccaggio.
Styrene monomers (M) form radicals (R*) when they are exposed to either light or heat (Reaction 1). These radicals can react with either oxygen (causing peroxide radicals) or other monomers to create polymer chains. This polymerization is exothermic. If left uncontained, it can lead to runaway polymerization in the styrene storage tank, resulting in serious consequences.
TBC is a free radical inhibitor that requires oxygen to prevent the monomers from polymerizing. Because monomers are present in the solution and in the tank headspace, a minimum concentration (10–15 mg/L) of oxygen (O2) is required in both.
The O2 addition is necessary to take advantage of different reaction kinetics (Reaction 1) – peroxide radical formation (r1) occurs much faster than styrene polymer formation (r2). In the presence of the correct amount of TBC, these peroxide radicals are scavenged (r3). Otherwise, the peroxide radicals react with styrene monomers to form peroxide chains (polyperoxides, r4) until the oxygen is completely depleted.
These contaminations can be hazardous during the purification processes (distillation) due to the instability of peroxides at increased temperatures. Therefore, the TBC concentration in styrene must be maintained above 10–15 mg/L. Close monitoring of the TBC concentration is required to control its depletion.
While TBC is essential for preventing styrene and other reactive monomers from polymerizing prematurely, solely relying on laboratory analyses might be inadequate to guarantee consistent TBC levels within the required range.
Furthermore, the delay between sample collection, analysis, and results further magnifies the challenge of promptly addressing any deviations from optimal TBC concentrations. For operators tasked with maintaining TBC levels above the critical threshold of 10–15 mg/L, a more responsive and continuous monitoring approach is important to mitigate the risk of polymerization incidents and maintain product quality throughout the entire storage and transportation process.
A photometric process analyzer accurately tracks TBC reduction at the styrene storage tank inlet to maintain optimal conditions around the clock. Metrohm Process Analytics offers the 2060 TI Ex Proof Process Analyzer for monitoring TBC concentration in styrene (Figure 2).
Il metodo utilizzato si basa sulla norma ASTM D4590 per l'analisi colorimetrica del 4-tert-butylcatechol (TBC) nello stirene. I risultati sono calcolati sulla base di una determinazione fotometrica a 490 nm.
| Parametro | Concentrazione [mg/L] |
|---|---|
| 4-tert-butylcatechol (TBC) | 0–50 |
Due to styrene’s sensitivity to light and heat, storage conditions can quickly become hazardous. Continuous monitoring is essential. In hazardous environments, only explosion-proof analyzers like the 2060 TI Ex Proof Process Analyzer (Figure 2) ensure safe, real-time TBC control.
Online monitoring of TBC, as defined in accordance with ASTM D4590, is essential for maintaining product quality and safety during the production and storage of styrene, butadiene, and vinyl acetate. The presence of TBC prevents early polymerization, thereby avoiding potential hazards associated with unwanted polymerization reactions.
Maintaining TBC concentrations above the critical threshold of 10–15 mg/L is crucial. This requires close and continuous monitoring. Online process analyzers, such as the 2060 TI Ex Proof Process Analyzer from Metrohm Process Analytics (configured for photometric analysis), offer a reliable solution for real-time TBC concentration monitoring. This ensures optimal storage conditions and product quality.
- Optimize product quality and increase profit with fast response times to variation in process conditions.
- Fully automated diagnostics—automatic alarms for when TBC concentrations are outside of the specified parameters.
- Safe working environment and automated sampling.
- Falcke, H.; Holbrook, S.; Clenahan, I.; et al. Best Available Techniques (BAT) Reference Document for the Production of Large Volume Organic Chemicals. Industrial Emissions Directive 2010/75/EU (Integrated Pollution Prevention and Control). JRC Publications Repository. https://publications.jrc.ec.europa.eu/repository/handle/JRC109279 (accessed 2024-03-06). https://doi.org/10.2760/77304
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