The couple of Ru/C and ammonium metatungstate hydrate (AMT) has been discovered to give the highest yield of ethylene glycol (EG) and propylene glycol (PG) from glucose under atmosphere of hydrogen. Herein, disclosing the kinetics of this catalytic process and understanding the functionality of catalyst have great significance for better utilization of biomass-based precursor in renewable ways. The kinetics study of this three-phase reaction disclosed the dependence of EG formation affected by both catalysts while PG formation depended on Ru/C only but inhibited by AMT. Hydrogenation reaction occurred at low temperature range (120 - 180) and glucose followed first order kinetics to sorbitol by Ru/C. This hydrogenation process had no mass transfer effect by hydrogen while the initial loading pressure was above 450psi. 10wt% of Ru/C showed the best catalyst efficiency due to the effect of the activated carbon support. AMT was activated at high temperature (above 185) and observed having no activity in C-C cleavage on saturated polyols (sorbitol, erythritol). Instead, sorbitol was determined to have first order C3-C3 and C2-C4 hydrogenolysis by Ru/C above 190 with significant hydrogen dependence. PG was produced in the route of C3-C3 cleavage, while C2-C4 route resulted in EG formation and erythrose as intermediate. The role of AMT was determined to catalyze aldose (glucose and erythrose) through retro-aldol condensation to glycolaldehyde which was further reduced by Ru/C to EG. Moreover, the deposition of soluble AMT on carbon support modified Ru/C which resulted in a lower order kinetics and equilibrium shift to EG formation. The ratio of EG and PG formation can be adjusted between 7:1 to 1.5:1 by modifying the AMT loading and hydrogen pressure. A kinetic model was also studied. The experimental rate constants were well fitted and predicted.

Stepwise kinetic study of glucose conversion to ethylene glycol and propylene glycol over Ru/C and AMT catalysts

2019 Fall National Meeting

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