Electronic Metal‐Support Interaction Strengthened Pt/CoAl‐LDHs Catalyst for Selective Cinnamaldehyde Hydrogenation

• Published in: ChemCatChem 2022-09, Vol.14 (18), p.n/a
• Main Authors: Gao, Zhexi, Cai, Luoyu, Miao, Chenglin, Hui, Tianli, Wang, Qian, Li, Dianqing, Feng, Junting
• Format: Article
• Language: English
• Subjects: Aldehydes; Aluminum; Catalysts; Cinnamaldehyde; Cobalt; EMSI effect; Fine chemicals; Hydrogenation; interfacial structure; layered double hydroxides; metal-support interaction; Platinum; selective hydrogenation of cinnamaldehyde; Selectivity; X ray photoelectron spectroscopy
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202200634

Cinnamaldehyde (CAL) is a typical sustainable biomass molecule which is classified as α, β‐unsaturated aldehydes. Selective hydrogenation of CAL to produce high‐value and fine chemical cinnamylalcohol (COL) is an attractive catalytic transformation process. However, the hydrogenation of C=O bond in CAL is more unfavorable than C=C bond in thermodynamics and kinetics, leading to great challenge on achieving high yield of unsaturated alcohol. In this work, a Pt/CoAl‐LDHs catalyst was prepared for hydrogenation of CAL to COL, showing outstanding intrinsic activity (TOF as high as 4.93 s−1) and finally achieving 93.6 % selectivity at 95.4 % conversion. In contrast, the yields of COL over Pt/Co(OH)2 and Pt/Al(OH)3 were only 73 % and 34 % respectively. Characterizations including Raman, O‐XAFS, XPS revealed that the Co2+−O2−−Al3+ structure in CoAl‐LDHs contributed to strengthened metal‐support interactions, and resulted in electron‐rich and geometric decoration Ptδ− sites. The electron‐rich Ptδ− provided preferable H2 activation capability, and also exposed abundant unsaturated sites which optimized the adsorption mode of cinnamaldehyde favorable for C=O hydrogenation. However, in Pt/Co(OH)2 and Pt/Al(OH)3 catalysts, the Pt0 without electron‐rich and unsaturated property cannot improve the H2 activation capability as well as electronic repellency to C=C bond. In addition, a possible catalytic mechanism was proposed to illustrate the role of Ptδ−−Co2+−O2−−Al3+ interfacial structure on enhancing activity and selectivity. Selective hydrogenation: A highly active Pt/CoAl‐LDHs catalyst was prepared for hydrogenation of cinnamaldehyde (CAL) to cinnamylalcohol (COL), achieving 93.6 % selectivity at 95.4 % conversion. A possible catalytic mechanism was proposed to illustrate the role of the Ptδ−−Co2+−O2−−Al3+ interfacial structure for enhancing activity and selectivity.