Performance and mechanism of bamboo residues pyrolysis: Gas emissions, by-products, and reaction kinetics

The performances and reaction kinetics of the bamboo shoot leaves (BSL) pyrolysis were characterized integrating thermogravimetry, Fourier transform infrared spectroscopy, and pyrolysis-gas chromatography/mass spectrometry analyses. The high volatiles and low ash, N, and S contents of BSL rendered its pyrolysis suitable for bio-oil generation. The main mass loss of BSL pyrolysis occurred in the devolatilization stage between 200 and 550 °C. The peak temperatures of pseudo-hemicellulose, cellulose and lignin pyrolysis in BSL were 248.04, 322.65 and 383.51 °C, respectively, while their average activation energies estimated by Starink method were 144.29, 175.79 and 243.02 kJ/mol, respectively. The one-dimensional diffusion mechanism (f (α) = 1/(2α)) best elucidated the hemicellulose reaction. The cellulose (f (α) = 0.74 (1 - α)[-ln (1 - α)]^-13/37) and lignin (f (α) = 0.35 (1 - α)[-ln (1 - α)]^-13/7) reactions were best described by the nucleation mechanisms. The estimated kinetic triplets accurately predicted the pyrolysis process. 619.3 °C and 5 °C/min were determined as the optimal pyrolytic temperature and heating rate. The C-containing gases were dominant among the non-condensable gases evolved from the pyrolysis. The NO_x precursors (NH₃ and HCN) were found more important than NO emission in pollution control. 2,3-dihydrobenzofuran, (1-methylcyclopropyl) methanol, heptanal, acetic acid, and furfurals were the main pyrolytic by-products. BSL-derived biochar is a relatively pure carbon-rich material with extremely low N and S content. The BSL pyrolysis yielded a promising performance, as well as value-added by-products to be utilized in the fields of bioenergy, fragrance, and pharmaceuticals.