Studies On Selective Hydrogenation Of Cinnamaldehyde Over Some Photocatalytic Systems

Transfer hydrogenation reaction was achieved by using inexpensive,clean,non-polluting organic molecules as hydrogen sources.It can avoid some of the hazards caused by the use of flammable and explosive hydrogen in the traditional hydrogenation reaction,and has the advantages of easy operation and high safety.In recent years,with the attention to "green catalysis" and the development of photocatalytic technology,the use of a mild photocatalytic system to achieve the transfer hydrogenation has been particularly concerned by researchers.This paper mainly carried out the following three aspects of work about hydrogenation of cinnamaldehyde:(1)we studied the photocatalytic system for selectivity transfer hydrogenation of cinnamaldehyde to form cinnamyl alcohol over Pt/TiO2 and Au/TiO2 under visible light and 365 nm UV light respectively.Plasma resonance noble metal nanoparticles(Au and Pt)were deposited on TiO2 by photo-reduction approach.XRD,XPS,TEM and DRS were used to characterize them in detail.And we investigated the selectivity hydrogenation performance of the photocatalysts under visible light and 365 nm UV light.The results show that Au/TiO2 and Pt/TiO2 showed different activity order under visible light and 365 nm UV light.The catalytic performance of Au/TiO2 in visible light is better than that of Pt/TiO2 due to the existence of surface plasmon resonance effect of Au nanoparticles in visible region,and its TOF value is 56 h-1.However,Pt/TiO2 showed excellent photocatalytic performance under 365 nm UV light because of the simultaneous existence of Pt nanoparticles plasma resonance catalysis and TiO2 photocatalysis,and the TOF value was as high as 197 h-1.The above results indicated that the coupling of plasma resonance noble metal nanoparticles and semiconductors is conducive to photocatalytic selective hydrogenation of cinnamaldehyde.(2)We use the visible light responsive MIL-100(Fe)instead of semiconductor TiO2.Au/MIL-100(Fe)obtained via photo-reduction approach.XRD and DRS were used to characterize it.The photocatalytic performance for transfer hydrogenation of cinnamaldehyde to form cinnamyl alcohol was investigated under visible light.The results show that under the same condition,the catalytic performance is not as good as that of the first system Au/TiO2.It's probably the ?-? accumulation effect between aromatic ligands and the aromatic ring of cinnamaldehyde due to the C=O of cinnamaldehyde is difficult to adsorb on the catalytic active sites and the reduction ability of MIL-100(Fe)is poor.(3)The third part of the work we considered to use of cheap non-noble metal Cu nanoparticles to replace noble metals,Cu/TiO2 and Cu/MIL-100(Fe)were prepared.And we investigated the photocatalytic performance of the photocatalysts for hydrogenation of cinnamaldehyde.We found that cinnamaldehyde was not hydrogenated over Cu/TiO2,but the reaction substrate had isomerized.The hydrogenation of cinnamaldehyde proceeded over Cu/MIL-100(Fe),but its activity is very low and the TOF value is only 1.17 h-1.In this thesis we proposed the coupling of semiconductor(TiO2)and resonance noble metal Pt nanoparticles showed superior photocatalytic performance for transfer hydrogenation of cinnamaldehyde to form cinnamyl alcohol under 365 nm UV light.It provides a new idea for the construction of highly efficient selective hydrogenation catalyst for unsaturated aldehydes.