Real-time monitoring the carbonization and activation process of activated carbon prepared from Chinese parasol via zinc chloride activation

Abstract

The study of carbonization and activation mechanism is essential for the preparation of high-performance biomass-based activated carbon (AC), which has been widely used in many fields. In this work, an online volatile analysis and real-time sampling was carried out to study the carbonization and activation mechanism of AC prepared by pyrolysis of Chinese parasol sawdust and ZnCl2 mixture. Combining a series of analysis results, it was found that the effect of ZnCl2 could be divided into three stages: (1) At low temperature (<300 °C), it promoted the depolymerization and dehydration of hemicellulose to release furfural, but inhibited the release of other small molecules produced from hemicellulose, cellulose and lignin; (2) It catalyzed the dehydration of alcoholic hydroxyl groups and the cleavage of phenol/ether CO bonds in solid residues at 300−400 °C; (3) It catalyzed the aromatization reaction at temperatures ≥ 400 °C, and formed a large number of pore structures through the swelling effect of ZnCl2 and the release of small molecular gases. 2308 m2/g of micropore AC with micropore ratio of 71.9 % and 2057 m2/g mesoporous AC with mesoporous ratio of 58.6 % were obtained when the temperature just rose to 500 °C and 550 °C, respectively. No additional activation time was required, which helped to save time and energy consumption in AC production.