Influence of cellulose ultrastructure on the catalytic pyrolysis for selective production of levoglucosenone

This study was dedicated to enhancing the generation of levoglucosenone (LGO) from catalytic pyrolysis of cellulose by optimizing its ultrastructure. Cellulose was pretreated by Na2CO3 solutions with different concentrations and Amberlyst-15 (A-15) under different temperatures, respectively. The influences of pretreatment on the cellulose ultrastructure, especially its degree of polymerization (DP) and crystallinity index (CrI), were characterized. The catalytic pyrolysis experiments of pretreated cellulose were conducted with activated carbon as the catalyst to clarify the regulatory functions of ultrastructure on the LGO formation. Na2CO3 pretreatment could decrease CrI of cellulose remarkably and DP slightly. At the low Na2CO3 concentration, the decrease of CrI could promote the generation of LGO, but the high Na2CO3 concentration was detrimental to LGO formation because of the almost full transformation of cellulose Iβ to II. With the raising of temperature, A-15 pretreatment could increase the CrI and decrease the DP significantly, and the corresponding LGO yield showed a trend of gradual decrease. Moreover, the low CrI could lower the pyrolysis temperature, while the low DP could decrease the catalyst dosage for maximal LGO formation. The cellulose pretreated with 1 % Na2CO3 solution was most appropriate for producing LGO, and the maximum LGO yield was 19.76 wt. %, higher than that of 18.04 wt. % from raw cellulose, while the corresponding pyrolysis temperature of 285 °C and catalyst/sample of 1/5 were lower than those of 300 °C and 1/3 from raw cellulose.