High efficiency pyrolysis of used cigarette filters for ester-rich bio-oil through microwave-assisted heating

As a type of solid waste, the used cigarette filters (UCF) were utilized to produce ester-rich bio-oil via a cleaner production process, namely, microwave-assisted pyrolysis (MAP). The pyrolysis efficiency was significantly enhanced owing to the high heating rate under MAP conditions with assistance of microwave absorber silicon carbide (SiC) in reactor and adding methanol into N2 carrier gas. Compared with the traditional tubular muffle furnace heating method yielding 0% of bio-oil, the MAP heating method obtained 29.17% of bio-oil from UCF. The bio-oil yield from UCF increased from 29.17% to 46.71% due to the introduction of methanol. Results of the gas chromatography/mass spectrometry showed that esters were the main components in the bio-oils (over 40%), especially of methyl acetate (over 12%). The aromatic compounds of phenols and polycyclic aromatic hydrocarbons (PAHs) were also produced from the MAP of UCF. The bio-char from MAP of UCF exhibited the mesoporous property (e.g., over 500 m2/g of specific surface area). It is expected to produce over 350000 metric tons ester-rich bio-oil if the proposed technology can be scaled up globally. It will be a preeminent contribution for the conversion of UCF to the cleaner production and our environments. [Display omitted] •Used cigarette filters were converted into bio-oil through microwave heating.•High heating rate assisted microwave absorber and enhanced pyrolysis efficiency.•Adding methanol to carrier gas promoted the yield of 46.71 wt% bio-oil.•Smoking influence was clarified by comparison of unused cigarette filters.•358065-ton bio-oil can be produced from all used cigarette filters globally.