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Ru Nanospheres in Water Drops for Enhanced Catalytic Performances in Selective Hydrogenation

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journal contribution
posted on 31.07.2018, 00:00 by Zhikun Peng, Weidong Li, Yalei Miao, Sheng Chen, Guoji Liu, Shouchang Liu, Jie Gao, Baojun Li, Zhongyi Liu
In heterogeneous catalysis, especially in the presence of a hydrophilic and hydrophobic mixed solution, the relationship between a nano-/microscale dynamic system and catalytic performance is an unknown but very significant issue. Here, from the result of a coupling liquid–liquid–solid CFD-EDEM (CFD, computational fluid dynamics) simulation as well as a high-speed recording system, we found that it is favorable for the solid catalyst granules to stay in electrolyte water drops to construct instant soft core–shell (SCS) structures in an agitating condition. Different morphologies of Ru catalysts resulting in different water shells are responsible for the different hydrogenation performances. Ru nanosphere (NS) catalysts exhibit higher cyclohexene selectivity (S40 = 66.6%) than other morphologies in benzene-selective hydrogenation. Because the water shells formed around Ru NSs are uniform and in appropriate depth, this benefits the diffusion of cyclohexene and the inhibition of cyclohexane. On the basis of the promotion effect of the electrolyte shell around the catalyst in an agitated reaction, a “teardrop catalysis” model process is proposed for an agitated oil–water phase in a heterogeneous reaction. This model is also verified in CAL-selective (cinnamaldehyde-selective) hydrogenation and employed to improve cinnamyl alcohol (COL) selectivity. This work provides a new way of exploring physical effects for selective heterogeneous catalytic reactions.