Selective pyrolysis of Organosolv lignin over zeolites with product analysis by TG-FTIR

Organosolv lignin has been selected to investigate the thermal behavior of lignin over zeolites by using a thermogravimetric analyzer coupled with a Fourier-transform infrared spectrometer (TG-FTIR). The chemical structure of this lignin has been determined by 1H NMR to obtain the distribution of main functional groups such as methoxyl groups and free aliphatic and phenolic hydroxyl groups. All three zeolite catalysts tested, HZSM-5, H-β, and USY, exerted significant influences on the dehydration reaction in the initial stage, the deoxygenation reaction of oxygenated compounds such as methanol and phenols, and the char-forming process during lignin pyrolysis in the range 30–800 °C. The dehydration reaction was enhanced in the order USY > HZSM-5 > H-β, while char formation was suppressed in the reverse order. The presence of HZSM-5 and H-β catalyzed the conversion of both oxygenated compounds and chars into the low-molecular-weight gases CO, CO2, and methane. The addition of USY clearly aided decomposition of the oxygenated compounds, but had little effect on the char degradation.

► The distribution of main functional groups in Organosolv lignin is determined.
► All three zeolite catalysts, HZSM-5, H-β, and USY, have significant influences on the pyrolysis of this lignin.
► The dehydration reaction was enhanced in the order USY > HZSM-5 > H-β.
► The char formation was suppressed in the reverse order H-β > HZSM-5 > USY.