Characterization of Pd-CeO2/α-alumina catalyst for synthesis of dimethyl oxalate

Effect of adding CeO2 to Pd/α-Al2O3 as a catalyst promoter was investigated by X-ray diffraction, H2 chemisorption, and X-ray photoelectron spectroscopy methods. The addition of 0.8% CeO2 (wt%) greatly increased palladium dispersion on the α-Al2O3 support and decreased the particle size of palladium. Meanwhile, the addition of CeO2, increased the surface concentration of Pd. The in situ FTIR spectroscopy study indicated that CO was adsorbed on 1% Pd-0.8% CeO2/α-Al2O3 in the forms of linear species (band at 2089 cm−1) and bridged species (bands at 1967 and 1908 cm−1), and that the latter form was more stable. Methyl nitrite was very active and methoxylate could be observed from the IR spectra after methyl nitrite passed through the catalyst. Catalytic effects were evaluated in a micro-fixed-bed reactor at atmosphere pressure by using vapor-phase catalytic coupling reaction of carbon monoxide to (COOCH3)2 (dimethyl oxalate) as a model reaction.