Catalytic co-pyrolysis of cellulose over alkali and alkaline earth metal salts for levoglucosan production

A comprehensive study of alkali and alkaline earth metal (AAEM) salts including two different anions (Cl- and CH3COO-) in the catalytic pyrolysis of cellulose to produce levoglucosan (LG), bio-oil, and biochar were investigated. At the same time, the catalytic pyrolysis mechanism was also speculated. The thermogravimetric analyzer (TGA) and lab-scale fixed-bed reactor system were used to determine the thermal degradation process and the pyrolysis products of LG, bio-oil, and biochar. The optimized pyrolysis parameters were obtained by using Box-Behnken design-response surface method. According to the results, AAEM salts significantly boosted the yield of biochar, as well as greatly cut down the output of LG and bio-oil. The rank of effect on LG yield was as follows: CaCl2, MgCl2 > CH3COOK, CH3COONa > (CH3COO)2Mg, (CH3COO)2Ca > KCl, NaCl. Moreover, the addition of AAEM salts considerably dropped the activation energy E of cellulose pyrolysis as well as prompted microcrystalline cellulose pyrolysis under lower temperatures. This study was pivotal in deducing the pathway of cellulose pyrolysis, thereby offering critical insights to hasten the progress of biomass utilization.