A Pd–Fe/α-Al2O3/cordierite monolithic catalyst for CO coupling to oxalate

A novel Pd–Fe/α-Al2O3/cordierite monolithic catalyst was prepared for the synthesis of diethyl oxalate from CO and ethyl nitrite. The palladium-based monolithic catalyst with an optimal thickness (15 μm) of Al2O3 washcoat showed excellent catalytic activity and selectivity in a continuous flow, fixed-bed microreactor. The physicochemical properties of catalyst were studied by a variety of characterization techniques. Catalytic performances of Pd–Fe/α-Al2O3/cordierite monolithic catalysts were dependent on particle size of alumina-sol, thickness of Al2O3 washcoat, pore structure, surface acidity of carrier, and distribution of active metal component on the Al2O3 washcoat. Under the mild reaction conditions, CO conversion was 32% and the space–time yield of diethyl oxalate was 429 g/(L h). Pd efficiency (DEO(g)/Pd(g)/h) of the monolithic catalyst (274 h−1) was much higher than that of a reference pellet catalyst (46 h−1), probably due to high dispersion of the Pd nanoparticles on the surface of the monolithic catalyst.