Titanate Nanotube-Supported Au-Rh Bimetallic Catalysts: Characterization and Their Catalytic Performances in Hydroformylation of Vinyl Acetate

A series of titanate nanotube-supported metal catalysts (M/TNTs, M = Rh, Au orAu-Rh) were facilely synthesized. The effects of different Au contents, reduction processes and sequence of loading metals on their catalytic performances in the hydroformylation of vinyl acetate were comparatively investigated. The results showed that some Au and Rh formed bimetallic particles. Furthermore, the presence of Au in catalysts could significantly improve the selectivity of reaction for aldehydes. Compared with the monometallic catalysts (Rh-0.33/TNTs-1 and Au-0.49 /TNTs-2), the resultant bimetallic catalysts exhibited significantly higher selectivity for aldehydes as well as higher TOF values in the hydroformylation of vinyl acetate. Among them, Au-0.52/Rh-0.32/TNTs-12 displayed the best catalytic performance. The corresponding selectivity for aldehydes was as high as 88.67% and the turnover frequency (TOF) reached up to 3500 h(-1). In addition, for the reduction of Rh3+ and Au3+ ions, the photo-reduction and ethanol-reduction were the optimal techniques under the present conditions, respectively.