Styrene (Vinyl Benzene)

Production Method

Styrene comprises approximately 70-80% benzene and 20-30% ethylene. Today, styrene production is commonly carried out via ethylbenzene dehydrogenation. Benzene and toluene are obtained as by-products. In this method, iron (III) oxide, potassium oxide and potassium carbonate are used as catalysts. During production, distillation occurs at high temperature. This increases styrene's tendency towards polymerization. To prevent this problem, elemental sulfur was previously used; nowadays, additives and inhibitors (small amounts of NaOH) are added instead. Another method is the propylene oxide method. In this method, ethylbenzene is reacted with oxygen. The resulting peroxide reacts with propylene. Hydrogen is then removed to obtain styrene. 15-20% of total styrene is produced via this method. An example of alternative styrene production is the obtainment of stilbene through toluene oxidation and styrene obtainment through the reaction of stilbene with ethylene. The advantage of this process is that it uses half the ethylene compared to the ethylbenzene dehydrogenation method.

Polymerization Problem in Styrene Production

Styrene is a monomer and has a tendency towards polymerization.

Causes of Polymerization:

• Temperature (65°C and above). • Dissolved oxygen. • Inhibitor deficiency.

To Stop Polymerization:

• Add TBC (4-tert-butylcatechol) at 0.5% ratio and aerate. (10-15 ppm) • Reduce tank temperature by applying water in spray form. • Can be diluted with ethylbenzene. As the product polymerizes, viscosity increases, the product temperature exceeds the boiling point, and the tank may rupture under pressure.

Applications

Styrene is most commonly used in GPPS (General Purpose Polystyrene) and HIPS (High Impact Polystyrene) production. GPPS, also known as crystal polystyrene, is preferred in single-use plastic cups and some food packaging due to its crystal clarity. HIPS, also known as impact-resistant polystyrene, is a type of grafted copolymer to which butadiene rubber has been added to increase impact resistance. Due to its ease of processing and high stability, it has a quite broad range of applications. It is used in the production of yogurt containers, toys, white goods and automotive parts. Secondly, it is used in EPS (Expanded Polystyrene) production. It is a lightweight polymer. It is added as a foaming agent to soften the resin. Due to its low water absorption, good insulation and high mechanical strength properties, it is an excellent material for the construction sector. Its consumption is expected to increase in the coming years. The third application is ABS (Acrylonitrile Butadiene Styrene) production. It is also used in resin production. Many resins contain 15-30% styrene. It reduces viscosity, thins the resin and increases its fluidity. At the same time, it provides hardening.

Styrene Situation in Turkey

Since styrene production is not carried out in Turkey, domestic styrene demand is met through imports. Styrene is used in Turkey in sectors such as PS, SBR and other areas (unsaturated polyester resins, protective coatings, etc.). The GTİP (Customs Tariff Statistics Position) number is defined as 2902.50.00.00.00. *According to Turkish Statistical Institute data, total styrene imports in 2018 were approximately 266,000 tonnes. The countries from which most imports are made are Spain, Saudi Arabia and the Netherlands, in that order. Öznur Kurt - Product and Service Development / Assistant Specialist - Aleph Petrol ve Kimya / Ürünleri San. Tic. A.Ş. Sources: 1. "Styrene" en.wikipedia.org ty. Web. 04.11.2019. 2. T.C. Milli Eğitim Bakanlığı. (2012). Benzen Türevleri ve Prosesleri. Ankara, TR. 3. T.C. Devlet Planlama Teşkilatı. (2008). Kimya Sanayii Özel İhtisas Komisyonu (Petrokimya Sanayii-Klor Alkali- Sentetik Elyaf ve İplik Çalışma Grubu Raporu). Ankara, TR. 4. "Polyester Nedir?" www.baranboya.com ty. Web. 05.11.2019. 5."Sıvı (Likit) Ürünler ve Ambalajları" www.ambalaj. org.tr July-August 2006. Web. 21.11.2019 6."Hips Antişok" www.polinyapi.com.tr ty. Web. 21.11.2019 7. Styrolution. (2013). Global Styrene Market-Key Factors Influencing the Future Landscape, Platts Global Aromatics Conference. Seoul. 8. "Dış Ticaret İstatistikleri" biruni.tuik.gov.tr ty. Web. 05.11.2019.