Study On Catalyst Of CO Coupling Reaction To Diethyl Oxalate

Synthesis of diethyl oxalate (DEO) via catalytic coupling reaction of CO and ethyl nitrite (EN) is an environment benign and atomic economic process. The effecting factors of catalytic activities, such as Pd loading amount, promoters and the plasma treatment on the catalysts, were investigated in this paper based on former achievements on this subject. The catalysts were evaluated in the fixed bed reactor with 5mL catalyst. The experiments were carried out on catalyst in the same reaction condition of CO 25%, ethyl nitrite 15%, nitrogen 60%, the residence time 1.8s and temperature of 373K~ 393K. A series catalyst was prepared by impregnation method with Pd loadings in the range 0.4-2.0wt%. The results indicated that the catalytic activity of 0.8% Pd/-Al2O3 was the highest among all the catalysts.The influence of promoter was also studied. La, Ce, Ti, Cu, Fe, Co and Li promoters were added in the new catalysts, respectively. The catalysts were prepared by the impregnation method. The results showed that the catalysts doped La or Ce can obviously improve catalytic performance. The molar ratio of La/Pd and Ce/Pd were further investigated in the later experiments. The results indicated that the catalysts reached the best catalytic capability when La/Pd (mol ratio) is 0.5 and Ce/Pd (mol ratio) is 1.0. Meanwhile, the catalysts were characterized by BET, TEM, XPS and ICP, respectively, which can provide the useful information of the catalysts.The catalysts including La, Ce, Ti, and Fe promoters were investigated after they were treated with plasma method under the nitrogen or hydrogen environment. The performance of catalysts treated under the hydrogen environment is better than that under nitrogen environment. Comparing the plasma treated catalyst with untreated, the STY of DEO and the conversion of CO on La-Pd/α-Al2O3 catalyst increased 7.8% and 8.3%; and the STY of DEO and the conversion of CO on Ce-Pd/α-Al2O3 (20-40 mesh) catalyst increased 23.8% and 25.1%. Combining with the catalysts characterization results, the influence of these effecting factors was discussed.