Mechanistic Study On Catalytic Conversion Of Glucose Into Low Carbon Glycols Over Nickel Promoted Tungsten Carbide Catalyst

Hydrogenolysis of biomass-derived sugar into valuable chemicals such as ethylene and propylene glycols (Eg, Pg), an alternative technology from renewable resource instead of fossil, is a promising green process. Most previous research on glucose hydrogenolysis, focusing on catalyst development, has been conducted with dilute glucose aqueous solution, which hinders industrial application of this process.A deep understanding of the mechanism of glucose hydrogenolysis would be of great significance for catalyst design and process application. We have developed a highly efficient nickel promoted tungsten carbide catalyst for glucose hydrogenolysis with selectivity of ethylene glycol as38%. Therefore, in this thesis catalytic conversion of glucose into glycols over2%Ni-30%W2C/AC Catalyst was investigated to elucidate its reaction mechanism.The dependence of main product distribution on the reaction parameters including temperature, initial glucose concentration, catalyst amount and H2pressure has been investigated. The results, in combination with the intermediate analysis by LCMS and GCMS revealed the reaction pathways for glycol formation from glucose over nickel promoted tungsten carbide. The main results and conclusions are as follows:(1) Glucose undergoes hydrogenolysis (retro-aldol reaction), hydrogenation, isomerization and dehydration in parallel under the reaction condition.(2) Retro-aldol reaction favors for glucose of low concentration, resulting in better glycol yields, while dehydration and hydrogenation favor the glucose of high concentration, leading to coking and hexyl alcohol.(3) Addition of NaOH into the reaction could significantly increases the C3product yields by enhancing the isomerization of glucose into fructose.