Comparison of Acids and Sulfates for Producing Levoglucosan and Levoglucosenone by Selective Catalytic Fast Pyrolysis of Cellulose Using Py-GC/MS

Levoglucosan (LG) and levoglucosenone (LGO) are two high-valued chemicals, which can be produced by catalytic fast pyrolysis of cellulose with proper catalysts. This work investigated the catalytic characteristics of different acids and metal salt catalysts to produce LG and LGO using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analysis (TGA). The results showed that weak acids (such as formic acid and acetic acid) enhanced LG yield, whereas sulfuric acid and phosphoric acid promoted the yield and selectivity of LGO with inhibitory effects on LG production. The maximum LGO selectivity of 61.8% was obtained with 10% phosphoric acid, while the maximum LG selectivity of 87.6% was obtained with 10% acetic acid. In comparison with two impregnation methods, the filtration method can increase LGO yield, while the evaporation method enhanced the selectivity of LGO (up to 82.6%) with lower concentration of phosphoric acid. The effects of metal salts on pyrolysis of cellulose were investigated by impregnating with different sulfates and chlorates. The results indicated that sulfates can increase the LGO yield significantly, which can be attributed to the effect of sulfate anions.