Hydrogenation of cinnamaldehyde to cinnamyl alcohol with metal phosphides: Catalytic consequences of product and pyridine doping

• Published in: Applied catalysis. B, Environmental Vol. 277; no. C; p. 119272
• Main Authors: Bonita, Yolanda, Jain, Varsha, Geng, Feiyang, O’Connell, Timothy P., Ramos, Norbert X., Rai, Neeraj, Hicks, Jason C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.11.2020; Elsevier BV; Elsevier
• Subjects: Aldehydes; Bimetallic; Bimetals; Biomass conversion; Carbonyl compounds; Carbonyls; Catalysts; Charge transfer; Chemoselectivity; Cinnamaldehyde; Density functional theory; Doping; Fourier transforms; Functional groups; Hydrogenation; Infrared spectra; Metal phosphides; Phosphides; Pyridines; Reaction mechanisms; Reaction modulation; Selectivity; Metal phosphides; Reaction modulation; Biomass conversion; Chemoselectivity; Bimetallic
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2020.119272

Controlling the selectivity to CO hydrogenation in cinnamaldehyde over RuMoP through steric and electronic effects. [Display omitted] •99 % selectivity to CC bond reduction achieved with monometallic Ni2P and Co2P.•Selectivity to C = O reduction was 5% with NiMoP and 91 % with RuMoP.•Steric effects from adsorbed products improved the C = O hydrogenation selectivity.•DFT calculations predicted similar reduction products as observed in the experiments. Selective hydrogenation of α,β-unsaturated aldehydes is challenging due to the competition between unsaturated functional groups (CC and CO) with the catalyst. This study probes the use of metal phosphides as selective catalysts for cinnamaldehyde hydrogenation. Monometallic phosphides (MP; M = Ni, Co, Ru) showed high affinity to CC hydrogenation, with 98 % selectivity to hydrocinnamaldehyde with both Ni2P and Co2P. Bimetallic RuMoP improved the cinnamyl alcohol (COL) selectivity up to 91 %, while bimetallic NiMoP preferred CC hydrogenation to hydrocinnamaldehyde. Density functional theory (DFT) suggested greater charge transfer between the carbonyl oxygen and Mo sites on the surface leading to a lower activation energy barrier for cinnamaldehyde hydrogenation to COL. Product and pyridine doping studies resulted in an increased selectivity to COL possibly through surface coverage effects. Lastly, diffuse reflectance infrared Fourier transform spectra and DFT provided insights into the CAL adsorption mode and the reaction mechanism that supported the experimental observation.