4.7 Article

Geometrically embedding dispersive Pt nanoparticles within silicalite-1 framework for highly selective α, β-unsaturated aldehydes hydrogenation via oriented C = O adsorption configuration

期刊

CHEMICAL ENGINEERING JOURNAL
卷 446, 期 -, 页码 -

出版社

ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2022.137064

关键词

Zeolitic microchannel; Confinement effect; Selective hydrogenation; alpha, beta-unsaturated aldehydes; Fine chemistry; Core-shell catalyst

资金

  1. National Natural Science and China National Petroleum Corporation (CNPC) Joint Foundation [U1662101, 21173030]

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The authors designed a catalyst with Pt nanoparticles embedded in a zeolitic microchannel to achieve selective hydrogenation of α,β-unsaturated aldehydes. The confinement effect in the microchannel enhances the adsorption and hydrogenation of the C=O group, leading to high yields and selectivities of unsaturated alcohols. The study also demonstrated the importance of molecular size and electronic effects in controlling the selectivity of the hydrogenation reaction.
The issue for thermodynamically favored C = C hydrogenation needs to be overcome in the hydrogenation of alpha, beta-unsaturated aldehydes to unsaturated alcohols. Herein, we employ confinement effect in the catalyst-designing engineering to orient the C = O adsorption by the zeolitic microchannel, where highly dispersed Pt nanoparticles are homogeneously well-embedded within the silicalite-1 framework (Pt@S-1). Comprehensive characterizations, such as HAADF-STEM, H-2-TPR, FT-IR of CO adsorption and XPS are carried out to demonstrate the geometric, confinement and electronic properties of metal species. In the hydrogenation of alpha, beta-unsaturated aldehydes with suitable molecular size, Pt@S-1 displays preferential C = O hydrogenation. For example, Pt@S-1 gives conversion of 99.8% and meanwhile the aiming cinnamal alcohol selectivity of 98.7% in the hydrogenation of cinnamaldehyde, outperforming larger Pt nanoparticles ill-suitedly embedded within silicalite-1 (Pt@S-1-is) and highly dispersed Pt nanoparticles supported on the silicalite-1 surface (Pt/S-1). For the hydrogenation of smaller 3-methyl-2-butenal, though the confinement effect boosts the C = O hydrogenation to some extent, the synergetic electronic effect via introducing Fe species effectively increases the unsaturated alcohol selectivity. Investigations on the adsorption configuration by in-situ FT-IR spectroscopy clearly indicate that the unsaturated aldehyde with suitable molecular size is preferentially adsorbed on Pt sites of Pt@S-1 via the oxygen atom of C = O with on-top eta(1) mode, thus favoring high unsaturated alcohol selectivities, while the d(i)-sigma(CO)eta(2) and eta(4) adsorption modes on Pt@S-1-is and Pt/S-1 are relatively adverse for prioritized C = O hydrogenation.

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