Indones. J. Chem., 2021, 21 (5), 1111 - 1119 Renita Manurung et al. 1111 Synthesis and Characterization of Polystyrene Sulfonic Acid from Expanded Polystyrene Foam as a Catalyst in the Synthesis of Triacetin Renita Manurung, Rosdanelli Hasibuan, Fatimah Batubara, Handy Inarto * , Alwi Gery Agustan Siregar, and Auryn Saputra Department of Chemical Engineering, Faculty of Engineering, Universitas Sumatera Utara, Jl. Almamater, Padang Bulan, Medan 20155, Indonesia * Corresponding author: tel: +62-87887836636 email: inatohandy@gmail.com Received: October 13, 2020 Accepted: May 18, 2021 DOI: 10.22146/ijc.60559 Abstract: In Indonesia, the composition of waste has gradually changed over time. To reduce expanded polystyrene (EPS) foam waste, we converted it into a heterogeneous acid catalyst, namely Polystyrene Sulfonic Acid (PSSA). The catalyst was then used in an esterification reaction to generate triacetin. In this research, the synthesis of PSSA was performed using a sulfonation reaction with silver sulfate (Ag 2 SO 4 ) as the catalyst. Based on FTIR analysis, the sulfonation reaction was successful. The use of 0.5% and 1% catalysts led to a significant increase in the degree of sulfonation of PSSA, while there was a relatively constant increase when using 1.5–2.5% catalysts. The highest degree of sulfonation (78.63%) was achieved when the reaction was performed using 2% Ag 2 SO 4 catalyst for 25 min. The PSSA with the highest degree of sulfonation was characterized using X-Ray Diffraction (XRD), SEM-EDX, and BET-BJH. This PSSA had a semi- crystalline structure with a crystallinity of 73.83%, a particle size of 1.75 nm, mesoporous pores with a radius of 16.984 Å, and a sulfur content of 15% (% mass). Keywords: EPS foam; sulfonation; catalyst; silver sulfate; characterization ■ INTRODUCTION The composition of solid waste, notably the volume of expanded polystyrene (EPS) foam, has evolved and increased in line with industrial technology development and population growth. Cordova and Nurhati [1] reported that an approximate inflow of waste from nine river estuaries into the Indonesian Sea from June 2015 to July 2016 of approximately 23 ± 7.10 tons and 59% plastic waste, with EPS foam as the dominant type of waste. The disposal of EPS has therefore become an acute problem with an associated high environmental impact. As a result, there is increasing concern regarding the recycling of EPS waste, for which different options are developed. The tertiary recycling offers an alternative way of handling polymer waste, where waste is degraded/depolymerized into different materials such as styrene, toluene, and ethylbenzene to produce new polymers or other substances. In this context, the optimum catalyst and reactor design can enable catalytic degradation to occur at a lower temperature and increase the selectivity of products. The catalytic degradation of polystyrene has mainly been studied using solid catalysts such as zeolite, silica-alumina, fresh FCC catalyst, and MCM-41, which are expensive [2-3]. Another approach to reduce the waste involves the conversion of EPS foam waste into an acid catalyst namely Polystyrene Sulfonic Acid (PSSA). The PSSA has primarily been applied in industry in reversible osmosis membranes, ion exchangers, ultrafiltration, and plasticizers for conductive composites [4]. The PSSA is considered to have similar acidic properties to the SiO2 –H 3 PO 4 catalyst, which can be used to manufacture triacetin via the esterification process [5- 6]. There are various methods to prepare the PSSA catalyst. Martins et al. reacted polystyrene with acetyl sulfate as the sulfonating agent in CH 2 Cl 2 at 40 °C for 30 min to produce PSSA with a sulfonation degree (SD) of 18–22% [4]. Bozkurt conducted sulfonation of polystyrene using sulfuric acid as the sulfonating agent in cyclohexane in the presence of P 2 O 5 catalyst at 40 °C