Catalytic Hydrogenation Of Cyclic Ester Into Ethylene Glycol Using Water As Hydrogen Source

The excessive consumption of fossil energy is threatening thedevelopment of human society, reduction our dependence onpetroleum oil and the development of renewable and green energysources are necessary. Nowadays, the development of renewableenergy to replace fossil fuels has become a hot research topic for manyresearchers. Biomass has attracted much attention to producechemicals due to its excellent properties: abundant, renewable, andproduces less pollution. Ethylene glycol is an important intermediatechemical and solvent that has been widely used in antifreeze, liquiddetergents, biodegradable polyester fibers, cosmetic products,pharmaceuticals, explosives, and plasticisers. The current conventionalprocess involves industrial production from petroleum-derivedethylene via hydration of the intermediate ethylene oxide. Recently,catalytic hydrogenation of biomass-derived glycolide for the synthesisof ethylene glycol was reported. However, these reactions still havesome limitations, such as the use of gaseous hydrogen, organicsolvents and expensive catalysts. Therefore, the development of asuitable reaction process for the production of ethylene glycol fromglycolide is highly desirable. In this study, the synthesis of ethylene glycol from biomass-derived cyclic esters using cheap and activemetals as reductants and water as hydrogen source under hydrothermalconditions is investigated. This research provides a useful process forthe synthesis of ethylene glycol with the advantages of simple, fast andenvironmental friendly and without the use of high-pressure gaseoushydrogen, expensive catalysts and organic solvent.This study focuses on the production of ethylene glycol fromglycolide under hydrothermal conditions. Results showed that thehighest yield of94%was obtained with25mmol Zn，6mmol CuO and25%water filling at250oC for150min. Moreover, propylene glycolwas also achieved via hydrogenation of DL-lactide under the sameconditions and gave84%yield.Furthermore, based on previous experimental results, reactionpathway for the formation of ethylene glycol from glycolide underhydrothermal conditions was proposed. Moreover, the reason for thereduction of catalyst CuO into Cu was also discussed, the resultsindicated that in-situ formed hydrogen reduced CuO into Cu.At last, the conversion of ethylene carbonate into ethylene glycolunder hydrothermal conditions was investigated. The reactionconditions such as the kinds of catalysts and reductants, reactiontemperature, water filling were optimized. The yield of58%ethyleneglycol was obtained with the addition of25mmol Zn,5mmol Fe,25%water filling at250oC for2h. This result provides a usefulmethod for the formation of ethylene glycol from ethylene carbonateunder hydrothermal conditions.