Effect of Organic Additives on the Performance of Nano-sized Ru-Zn Catalyst

A novel Ru-Zn catalyst was prepared by coprecipitation. The catalyst was characterized by XRF, XRD and TEM. The effects of organic additives on the performance of the Ru-Zn catalyst for benzene selective hydrogenation to cyclohexene were investigated. The results showed that the catalyst was composed of Ru and Zn in molar ratio of 33.8 : 1, and the most probable value of the Ru crystallite size in the catalyst was 5.1 nm. The modification of Ru with Zn and the small size effect were the main cause why the catalyst exhibited the high activity and the excellent cyclohexene selectivity. When PEG (polyethylene glycol) was used as an additive, the activity of the catalyst decreased, and the cyclohexene selectivity increased with the increase of the PEG molecular weight. With the addition of PEG-20000, a cyclohexene selectivity of 78.9% at a benzene conversion of 68.7% and a maximum cyclohexene yield of 61.4% were obtained. With diethanolamine and triethanolamine as additives, cyclohexene yields were as high as 58.9% and 58.2%, respectively.