Issue 79, 2016, Issue in Progress

Particle size effects in the selective hydrogenation of cinnamaldehyde over supported palladium catalysts

Abstract

This work investigated the catalytic performance of palladium catalysts in the selective hydrogenation of α,β-unsaturated aldehydes, and especially the effect of Pd particle size on the hydrogenation of cinnamaldehyde (CAL). An unsupported nanosized Pd catalyst and a series of supported Pd catalysts using supports of activated carbon, SiO2, TiO2, γ-Al2O3, SiC, and graphene oxide were prepared and evaluated in the selective hydrogenation of CAL. Varied sizes of Pd particles could be obtained directly by using different Pd precursors and indirectly by introducing an inactive Ag metal over a γ-Al2O3 supported palladium catalyst. Over a reducible TiO2 support, the Pd particle size can also be controlled indirectly by the effect of strong metal-support interaction (SMSI). Combined with their TEM observations and catalytic tests, density functional theory (DFT) calculations have confirmed that smaller Pd particles favored C[double bond, length as m-dash]C-centered adsorption of CAL leading to a higher selectivity to hydrogenation of the C[double bond, length as m-dash]C bond, forming hydrocinnamaldehyde (HCAL), while on larger ones, the C[double bond, length as m-dash]C-centered adsorption would be partly substituted by C[double bond, length as m-dash]O-centered adsorption resulting in a lowered selectivity to HCAL but an increased selectivity to C[double bond, length as m-dash]O bond hydrogenation, forming hydrocinnamyl alcohol (HCOL). It is clarified that the size dependence of the catalytic selectivity originates from the strong dependence of C[double bond, length as m-dash]C/C[double bond, length as m-dash]O-centered adsorption on Pd particle size. Finally, tests using solvents with different Pd–solvent interactions and α,β-unsaturated aldehydes with remarkable steric effect variations were applied to further regulate the adsorption between palladium and substrate to alter the catalytic activity and selectivity.

Graphical abstract: Particle size effects in the selective hydrogenation of cinnamaldehyde over supported palladium catalysts

Supplementary files

Article information

Article type
Paper
Submitted
02 Jul 2016
Accepted
01 Aug 2016
First published
02 Aug 2016

RSC Adv., 2016,6, 75541-75551

Particle size effects in the selective hydrogenation of cinnamaldehyde over supported palladium catalysts

F. Jiang, J. Cai, B. Liu, Y. Xu and X. Liu, RSC Adv., 2016, 6, 75541 DOI: 10.1039/C6RA17000E

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