Xinbin Yu

Date of Award

Fall 2020

Document Type

Open Access Dissertation

Department

Chemical Engineering

First Advisor

Christopher T. Williams

Abstract

Ethylene glycol is a bulk chemical and hydrogenation of dimethyl oxalate (DMO) on Cu/SiO2 catalysts is the final reaction step in a growing industrial syngas to ethylene glycol (StEG) process. Efforts to improve the performance of the catalysts are still ongoing and the detailed catalytic mechanism remains controversial.

In the present work, a series of 10 wt% Cu/SiO2 is prepared.by urea hydrolysis method and indium species is introduced by incipient wetness impregnation. Reaction studies show that 0.25 wt%-0.5 wt% of indium species can dramatically enhance the performance of 10 wt% Cu/SiO2 catalyst. Various characterizations reveal that indium species are partially reduced and have negligible effect on the content of Cu+ species on the surface. Rather, the promotional effect likely originates from interactions between reduced indium species and Cu0 species though enhanced ability of the latter to activate H2.

Support materials and the synthesis parameters (AE temperature and copper loading) are also optimized to prepare Cu/SiO2 catalysts as Cu+ species for the activation of C=O group in the reaction comes from Cu species strongly interacted with SiO2 during catalyst synthesis. KIT-6 supported copper catalysts are prepared via ammonia evaporation (AE) method. The mesoporous, interconnected channels of KIT-6 facilitate the dispersion of copper species. Reaction studies indicate that loading amount of copper species significantly influence the hydrogenation performance. Both AE temperature and loading amount of copper species influence the intrinsic activity. The hydrogenation of DMO to EG is proposed to proceed via the synergy between Cu0 and Cu+ sites and catalysts with the highest surface Cu0 content exhibit the highest intrinsic activity in the investigated range.

The adsorption DMO over Cu2+/SiO2 prepared by urea hydrolysis is studied via ATR-FTIR to know how C-O and/or C=O bond adsorb on the surface at room temperature. The results show that silica does not adsorb dimethyl oxalate and the primary intermediates over the surface of Cu2+-containing sample are identified as adsorption of two C=O groups via bidentate mode (1606 cm-1), acyl species (1357 cm-1, 1315 cm-1) and alkoxy C-O species (1045 cm-1).

Rights

© 2020, Xinbin Yu

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