Study on the mechanism of hydrogen production by catalytic pyrolysis of bagasse over CaO/Na 2 CO 3

Abstract

As a major type of agricultural waste, bagasse is rich in volatile matter and low in ash, making it an ideal raw material for thermochemical conversion to hydrogen-rich gas. In this study, an ex-situ microwave-assisted catalytic pyrolysis technique was used. CaO and Na 2 CO 3 and their mixed catalysts in different ratios were selected for the experiments at 550 °C. The aim is to optimize both the hydrogen yield and concentration of the components to produce high-quality fuel. Thermogravimetric analysis (TG/DTG) revealed the influence of the catalysts: Na 2 CO 3 significantly promotes low-temperature deoxygenation, and CaO can effectively adsorb CO 2. Molecular dynamics simulations showed that elevated temperatures promote carbon chain breakage, but too high a temperature (2,500 K) may lead to a carbonization cascade reaction, which inhibits bond breakage. The gas-phase products indicate that the mixed catalyst is most effective at a ratio of CaO : Na 2 CO 3 of 1:3, achieving the highest H 2 yield (maximum 17.26%) along with significant hydrocarbon generation inhibition (24.90%), and CO content reduction (23.45%). Catalyst characterization confirmed the presence of CaCO 3 in the mixed catalysts after pyrolysis. The CaO : Na 2 CO 3 = 1:3 catalyst was found to have a unique fibrous structure and a microporous network. Raman spectroscopy reveals the ordering of the carbon structure and differences in functional groups under the action of different catalysts. This study provides a theoretical basis for further optimizing the pyrolysis process of bagasse, and helps improve the conversion efficiency of biomass energy.