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

Abstract

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 (H 2, m/z = 2 a.m.u.), methane (CH 4, m/z = 16 a.m.u.), water (H 2O, m/z = 18 a.m.u.), carbon monoxide (CO, m/z = 28 a.m.u.), methanol (CH 3OH, m/z = 32 a.m.u.), carbon dioxide (CO 2, m/z = 44 a.m.u.), and ethanol (C 2H 5OH, m/z = 46 a.m.u), and found three of them – H 2O, C 2H 5OH and CO 2 – depended strongly on temperature during the pyrolysis. In addition, we concluded that weight loss was attributed to the evaporation and/or volatilization of H 2O, C 2H 5OH and CO 2, 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, C 2H 5OH and CO 2 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.