Selective production of levoglucosenone from catalytic pyrolysis of regenerated cellulose from a H3PO4-H2O system

A series of regenerated cellulose (RC) were prepared by a H3PO4-H2O system with different H3PO4 concentrations. The effects of H3PO4 concentrations on the physicochemical properties of RCs were studied, including crystallinity index (CrI), hydrogen bond energy (EH), accessibility, and degree of polymerization (DP). The catalytic pyrolysis experiments of RCs were executed with a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) instrument and a lab-scale device, to investigate the regulatory function of cellulose structure on the LGO formation. The results indicated that the H3PO4-H2O system could transform the cellulose crystal form from Ⅰ to amorphous form, reduce its CrI and EH significantly, improve its accessibility, while had slight effects on the DP. These changes made RC more appropriate for the selective preparation of LGO, and the corresponding optimal catalyst loading and pyrolytic temperature were also decreased significantly. With phosphoric acid activated carbon as the catalyst, the highest yield of LGO from RC in Py-GC/MS experiments reached 21.50 wt% at catalyst/cellulose (Cat/Cel) ratio of 1/5 and 270 °C, which was much higher than the 18.16 wt% of LGO gained from untreated cellulose at Cat/Cel ratio of 1/3 and 300 °C. In the lab-scale device, the maximum LGO yield from RC was 17.09 wt% at 270 °C and Cat/Cel ratio of 1/6.