Reducing priority polycyclic aromatic hydrocarbons in coal tar pitch through alkylation: Mechanism and potential toxicity evaluation

Coal tar pitch (CTP) is a carbon material with abundant yield in China, but the toxic polycyclic aromatic hydrocarbons (PAHs) contained in it have restricted its broader applications. In order to reduce the PAHs content, an alkylation method was developed in this study to modify CTP (MCTP) by using 1-dodecene as the alkylating reagent, and the optimal reaction conditions (temperature 170 °C, time 4 h, solvent dosage 60 times that of CTP, and alkylating reagent dosage 4 times that of CTP) for synthesizing the MCTP were determined by alkylation modification with model compounds. Compared with CTP, the content of PAHs in MCTP was reduced by 97.35 %. The mechanism of the reaction was explained by analyzing the types of alkylation products and combining structural analyses of CTP and MCTP. PAHs emissions from fumes and the toxic equivalent quantity (TEQ) among different environmental standards were greatly reduced, while MCTP demonstrated low cytotoxicity and ecotoxicity. The method can also be applied to the toxicity assessment of road materials such as alkylation by-products.