Preparation of anhydrate sugars from biomass via pyrolysis

Levoglucosan (LG) and levoglucosenone (LGO) are platform molecules derived from biomass, which have versatile applications in varied chemical industries. Selective production of LG and LGO from biomass remains a challenging process and much research effort is devoted to this research topic. For examples, pretreatment of biomass to remove inorganics with various acids is conducted for suppressing cracking of cellulose and for enhancing selectivity of LG and LGO. A number of mineral acids, salts, solid acids and carbon-based catalysts are also tried for guiding the conversion of cellulose to the direction of LG and LGO. Some process development such as microwave assisted pyrolysis and hydrothermal treatment is also proposed to further enhance production of LG and LGO. Nevertheless, production of LG and LGO from biomass has yet not reach the stage of commercialization as there are some remaining issues to be addressed, i.e. the selectivity to LG and LGO, their separation from bio-oil, the cost and environmental impact, etc. This review mainly revisits the progress in pretreatment of biomass for removing inorganics, varied catalysts and process developments for conversion of biomass to LG and LGO. The major challenges in production of LG and LGO from biomass and the potential solutions are discussed or proposed as well.