农林业固废超临界水热化学制氢进展-反应机理

Thermochemical conversion technology for hydrogen production in supercritical water is a very promising technology for utilization of agriculture and forestry waste by taking supercritical water as the medium and converting the organic components of agriculture and forestry waste into hydrogen-rich gas through thermochemical means. In this paper, the reaction mechanism of the technology is systematically analyzed, the special physical and chemical properties of supercritical water are described, the reaction process of agriculture and forestry waste in supercritical water is studied, and the different degradation mechanisms and paths of main biomass components, such as cellulose, hemicellulose, lignin and amino acids, in supercritical water are discussed. For different reaction conditions, increasing the temperature, reducing the concentration and prolonging the residence time within a certain range all can significantly improve the hydrogen production performance, but the system operation cost will increase accordingly. Meanwhile, the change of pressure has little effect on the reaction result. In addition, although alkali metal homogeneous catalysts can play a significant catalytic role in biomass gasification, they will aggravate equipment corrosion and blockage problems at the same time. Therefore, heterogeneous catalysts are more suitable for industrial-scale supercritical water thermochemical hydrogen production system because of such advantages as high catalytic activity, high thermal stability, non-corrosiveness and recyclability. Future researches will focus on the quantitative description of organic components' reaction mechanism, mechanism investigation of the interaction between ash and the reaction between ash and catalyst, further investigation on the deactivation mechanism of catalysts and clarification of the added amount of catalyst.