Hydrogen production from glucose by partial oxidation in high temperature high pressure water - 2: Reaction mechanism and rate of HCOOH decomposition

By partial oxidation of glucose with ZnO in high pressure high temperature water at 300°C, glucose was converted into H₂ with relatively high yield and without CH₄ formation. In order to understand the reaction mechanism and the optimum condition of the process, we performed glucose partial oxidation at 200-300°t to analyse an intermediate of H ₂, without ZnO, which probably promotes the intermediate into H ₂. As a result, we detected a high yield of HCOOH. The formation of HCOOH was sensitive to reaction temperature and the yield was the highest at 200°C among the experimental conditions. It was confirmed that the role of ZnO was a promoter of HCOOH decomposition into H₂ and CO₂ through HCOOH conversion experiments with and without ZnO at 200-300°. The conversion of HCOOH with ZnO was within a few minutes at 300°C. Through the study, we suggested that two-stage reaction is effective for H₂ formation from glucose partial oxidation: the partial oxidation of glucose is conducted at 200°C and the conversion of HCOOH is achieved over 300°C. To confirm the idea, the two-stage reaction was performed: the partial oxidation of glucose was conducted at 200°C with ZnO followed to increase temperature up to 300°C for promotion of H₂ formation. The H₂ yield was less amount than expected. This was probably due that ZnO prohibited the formation of HCOOH on glucose partial oxidation at 200°C.