Thermogravimetry–mass spectrometry on the pyrolysis process of Lyocell fibers with and without catalyst

We analyzed the pyrolysis behaviors of Lyocell fiber, a novel man-made cellulosic fiber, with and without catalyst, using thermogravimetry–mass spectrometry (TG–MS) coupling technology. The temperature for maximum weight loss in the control Lyocell fibers was between 260 and 340 °C, and the fibers were completely decomposed at 460 °C. The temperature for maximum weight loss in the catalyzed fibers shifted to 130–300 °C, and 11% of the weight still remained at 460 °C. With TG–MS, we monitored the evolution profiles of several volatile compounds: hydrogen (H2, m/z = 2 a.m.u.), methane (CH4, m/z = 16 a.m.u.), water (H2O, m/z = 18 a.m.u.), carbon monoxide (CO, m/z = 28 a.m.u.), methanol (CH3OH, m/z = 32 a.m.u.), carbon dioxide (CO2, m/z = 44 a.m.u.), and ethanol (C2H5OH, m/z = 46 a.m.u), and found three of them – H2O, C2H5OH and CO2 – depended strongly on temperature during the pyrolysis. In addition, we concluded that weight loss was attributed to the evaporation and/or volatilization of H2O, C2H5OH and CO2, which benefits the removal of hetero-atoms, such as hydroxyl groups from the cellulosic rings during the carbon formation. We also proposed possible reaction mechanisms for the removal of water. Interestingly, C2H5OH and CO2 presented similar MS signal changes, implying that they were synchronously generated during pyrolysis. All results indicated that the catalyst positively altered and accelerated the pyrolysis and increased the carbon yield.