Pyrolysis of COVID-19 disposable masks and catalytic cracking of the volatiles.

ABSTRACT

The disposable masks generated in the battle against COVID-19 has attracted wide attention in the world. Pyrolysis can convert the masks into useful chemicals and fuels. In this work, the masks are pyrolyzed at temperatures of 400-580 °C and the volatiles generated are cracked without or with catalysts at 440-580 °C. The catalysts used include metal oxides (Al2O3, kaolin, Fe2O3, CeO2, TiO2) and molecular sieves (HZSM5, HY, ß(25H), ß(60H)). The yields and composition of gas and liquid products are studied in detail where the tetrahydrofuran (THF) soluble compounds are defined as the liquid product and the n-hexane soluble compounds are defined as the oil. The liquid product and the oil were identified by GC-MS and quantified by GC. Results indicate that 440 °C is sufficient for the masks' pyrolysis and the yields of gas, liquid product and oil are 23.4, 74.7 and 42.1 wt%, respectively. About 30% of the liquid product are C6-C35 hydrocarbons while about 70% are C36-C70 hydrocarbons trapped in the GC column (termed as column residue). The gas products are mainly C5, propylene and butene, accounting for 54.8%, 22.8% and 14.5% of the total gas product, respectively. Cracking of volatiles over various catalysts converts the liquid product mainly to propylene, butene and smaller organic gases. TiO2, HY and ß(60H) are good catalysts, especially ß(60H), which increases the yield of gas product to 86.5 wt% with 73.0% being ethylene, propylene and butene at 580 °C.