Utilizing Carbon Dioxide as a Reaction Medium to Mitigate Production of Polycyclic Aromatic Hydrocarbons from the Thermal Decomposition of Styrene Butadiene Rubber

• Published in: Environmental science & technology 2012-10, Vol.46 (19), p.10752-10757
• Main Authors: Kwon, Eilhann E, Yi, Haakrho, Castaldi, Marco J
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; Butadienes - chemistry; Carbon dioxide; Carbon Dioxide - chemistry; Chromatography; Combustion and energy production; Comparative analysis; Elastomers - chemistry; Exact sciences and technology; Gas Chromatography-Mass Spectrometry; Mass spectrometry; Other wastes and particular components of wastes; Pollution; Polycyclic aromatic hydrocarbons; Polycyclic Aromatic Hydrocarbons - chemistry; Prevention and purification methods; Refuse Disposal - methods; Styrenes - chemistry; Thermogravimetric analysis; Thermogravimetry; Wastes
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es301933p

The CO2 cofeed impact on the pyrolysis of styrene butadiene rubber (SBR) was investigated using thermogravimetric analysis (TGA) coupled to online gas chromatography/mass spectroscopy (GC/MS). The direct comparison of the chemical species evolved from the thermal degradation of SBR in N2 and CO2 led to a preliminary mechanistic understanding of the formation and relationship of light hydrocarbons (C1–4), aromatic derivatives, and polycyclic aromatic hydrocarbons (PAHs), clarifying the role of CO2 in the thermal degradation of SBR. The identification and quantification of over 50 major and minor chemical species from hydrogen and benzo[ghi]perylene were carried out experimentally in the temperature regime between 300 and 500 °C in N2 and CO2. The significant amounts of benzene derivatives from the direct bond dissociation of the backbone of SBR, induced by thermal degradation, provided favorable conditions for PAHs by the gas-phase addition reaction at a relatively low temperature compared to that with conventional fuels such as coal and petroleum-derived fuels. However, the formation of PAHs in a CO2 atmosphere was decreased considerably (i.e., ∼50%) by the enhanced thermal cracking behavior, and the ultimate fates of these species were determined by different pathways in CO2 and N2 atmospheres. Consequently, this work has provided a new approach to mitigate PAHs by utilizing CO2 as a reaction medium in thermochemical processes.