Surface Spectroscopic Study of Renewable Ethylene Glycol Synthesis over Silicon Dioxide-Supported Metal Catalysts

Ethylene glycol (EG) is an extremely versatile chemical and, thus, is constantly in high demand. The current method of producing ethylene glycol involves oxidizing ethylene from natural gas into ethylene oxide over a silver (I) oxide catalyst, followed by hydration using acid. At nearly $37 per gram, however, silver (I) oxide is not very affordable. Recently, a new and economical synthetic method has been proposed using silicon dioxide-supported metal catalysts and syn gas (a mixture of carbon monoxide and hydrogen gas) .In a coupling reaction between carbon monoxide and methyl nitrite catalyzed by the supported metal, dimethyl oxalate (DMO) and nitric oxide are formed. The hydrogen in the syn gas can then be used to catalytically reduce DMO into ethylene glycol and methanol. Finally, the nitric oxide and methanol can be oxidized with atmospheric oxygen to regenerate methyl nitrite, which can then be recycled back into the reaction.

This experiment tested the selectivity and stability of SiO₂-supported copper during the reduction of DMO into ethylene glycol. Catalysts were prepared in 15-20 percent weight copper, using incipient wetness impregnation, as well as urea-assisted gelation. Fourier transform infrared spectroscopy was then performed as DMO dissolved in ethanol flowed over the catalyst. These spectra allowed some of the functional groups forming on the surface of the metal catalyst to be identified, based on shapes of peaks at certain wavenumbers. Determining the identities and concentrations of byproducts will give insight into the selectivity of the Cu/SiO₂ catalyst. Taking many spectra over extended periods of time will show how stable the catalyst is under reductive conditions.