Critical Review on the Preparation of Platform Compounds from Biomass or Saccharides via Hydrothermal Conversion over Carbon-Based Solid Acid Catalysts

The use of carbon-based catalysts to catalyze the hydrothermal conversion of biomass and its derived carbohydrates to produce platform compounds such as 5-(hydroxymethyl)furfural (HMF), levulinic acid (LA), and furfural (FF) has a long history. The excellent thermal stability and chemical activity and low preparation cost of carbon-based catalysts make them develop rapidly in catalytic hydrothermal conversion, which is the core attention in the review. Carbon catalysts are divided into sulfuric acid-based carbon catalysts, phosphoric acid-based carbon catalysts, metal-supported carbon catalysts and other types of carbon catalysts, to study their application to hydrothermal decomposition of monosaccharides, disaccharides, polysaccharides, and biomass. The characteristics of different types of carbon catalysts were introduced. The diversified development of carbon-based catalysts and the upgrading of feedstocks have promoted the improvement of product selectivity, cost, and energy optimization, realizing the transformation of hydrothermal decomposition of biomass into a greener process. However, the development of efficient catalytic systems for hydrothermal conversion of abundant, cheap, and readily available biomass sources is still an ideal choice to expand the process strategy.