(773f) Hydrogenation of Dimethyl Oxalate to Ethylene Glycol On a Cu/SiO2/Cordierite Monolithic Catalyst: Enhanced Internal Mass Transfer and Stability

Ethylene glycol (EG) is an important chemical used in a variety of consumer and industrial applications. At present, ethylene oxidation is a universal industrial approach to produce EG. However, as crude oil resource shrinks, synthesis of EG from syngas attracts increased interest. This indirect synthesis process includes two steps: the coupling of CO with nitrite esters to dimethyl oxalate (DMO), and the hydrogenation of DMO to EG. Copper-based catalysts have been widely used for the hydrogenation of DMO. Notably, internal diffusion has been considered as the rate-limiting step. In order to eliminate the internal diffusion limit and radically solve the contradiction between the grain size and bed resistance, A catalytic structured reactor for hydrogenation of DMO has been introduced in this work.

The structured reactor consisting of a cordierite monolith is based on a non-precious metal, thus cost-effective for a widespread application in industry. The washcoat of the monolithic catalyst was dip-coated with highly dispersed Cu/SiO₂ slurry prepared by ammonia evaporation method. This structure could guarantee high copper species diffusion within the mesopores of silica matrix in the form of copper phyllosilicate. These features render a catalyst with high activity in the reaction of hydrogenation of DMO, achieving a 100% conversion of DMO and more than 95% selectivity of EG. Notably, the conversion of DMO over monolith is significantly higher than compared to a packed bed Cu/SiO₂  catalyst in the form of pellet and extruded granular grains. It is primarily due to the short diffusion course of the thin wash-coat layer and regular channel structure of the monolithic catalyst. Calculations indicated that the internal mass transfer is dominated on the extruded granular catalyst. Moreover, the monolithic catalyst possessed excellent stability compared to packed bed catalysts upon heat treatment, which is attributed to the decreased probability of formation of hotter spots and less dead zones.