Research progress and application prospects of the carbonization of biomass materials

Biomass is a renewable energy resource with rich content in China. The products of the carbonization of biomass materials have been widely used in energy storage, adsorption materials, and other fields. Studying the carbonization process of biomass materials is crucial for the efficient use of biochar. This article summarizes the effects of biomass types and carbonization conditions (such as carbonization temperature and pretreatment) on the structure, morphology, and properties of carbon in carbonization products. The aim is to provide a theoretical foundation for the effective use of biomass carbonization products. Various biomass materials and biochar can be prepared after treatment. The contents of cellulose, hemicellulose, lignin, and ash in different types of biomass materials vary greatly, and the carbon content, carbon structure, morphology, and properties of the products after carbonization differ. Therefore, selecting appropriate biomass materials based on usage requirements is essential. The carbonization temperature of biomass materials plays an important role in the pyrolysis of biomass. As the carbonization temperature increases, cellulose, hemicellulose, and lignin gradually decompose into gases with small molecules. Furthermore, as the carbonization temperature continues to increase, the internal structure of biomass carbon continues to rearrange, forming a dense aromatic carbon network plane of macromolecules, which increases the graphitization degree of biomass carbon. Additionally, the temperature greatly affects the structure and amount of the products of biomass carbonization. The activation of biomass materials further enhances the specific surface area and adjusts the pore structure of biomass carbon. Chemical activators such as acids, alkalis, and salts are commonly used and have their own advantages and disadvantages. Appropriate activators should be selected by a comprehensive consideration of usage requirements to activate the biomass. This article summarizes the preparation of carbon nanotubes by the carbonization of biomass materials through the template and chemical vapor deposition methods under the action of a catalyst. Further, the influence of components such as lignin and cellulose in biomass materials on the preparation of carbon nanotubes is analyzed. Cellulose in biomass materials has a small molecular weight and is easy to pyrolyze, resulting in gases with smaller molecules. However, lignin has a large molecular weight, is difficult to decompose, and produces less amount of small molecular gas. Therefore, biomass materials with high cellulose content are found to facilitate the preparation of carbon nanotubes. On this basis, the application prospects of biomass materials in carbon-containing refractories have been considered and examined to provide ideas for the preparation of new carbon-containing refractories with low cost and good properties.