Pyrolytic kinetics, reaction mechanisms and products of waste tea via TG-FTIR and Py-GC/MS

Abstract

Abstract The present study experimentally quantified the pyrolysis behaviors of waste tea (WT) as a function of four heating rates using thermogravimetric-Fourier transform infrared spectrometry and pyrolysis-gas chromatography-mass spectrometry analyses. The maximum weight loss of WT (66.79%) occurred at the main stage of devolatilization between 187.0 and 536.5\u202f°C. The average activation energy estimates of three sub-stages of devolatilization were slightly higher (161.81, 193.19 and 224.99\u202fkJ/mol, respectively) by the Flynn-Wall-Ozawa than Kissinger-Akahira-Sunose method. Kinetic reaction mechanisms predicted using the master-plots were f (α)\u202f=\u202f(3/2)(1\u202f−\u202fα)2/3[1\u202f−\u202f(1\u202f−\u202fα)1/3]−1, f (α)\u202f=\u202f(1\u202f−\u202fα)2, and f (α)\u202f=\u202f(1\u202f−\u202fα)2.5 for the three sub-stages, respectively. The prominent volatiles of the WT pyrolysis were CO2\u202f>\u202fC O\u202f>\u202fphenol\u202f>\u202fCH4\u202f>\u202fC O\u202f>\u202fNH3\u202f>\u202fH2O\u202f>\u202fCO. A total of 33 organic compounds were identified including alkene, acid, benzene, furan, ketone, phenol, nitride, alcohol, aldehyde, alkyl, and ester. This study provides a theoretical and practical guideline to meeting the engineering challenges of introducing WT residues in the bioenergy sector.