Pd and PdZn supported on ZnO as catalysts for the hydrogenation of cinnamaldehyde to hydrocinnamyl alcohol

Abstract

Liquid phase selective hydrogenation of cinnamaldehyde (CAL) was investigated over ZnO-supported Pd and PdZn catalysts different in the Pd loading. The former monometallic catalyst was less selective to the formation of cinnamyl alcohol (COL) irrespective of the Pd loading (5 and 30 wt.-% Pd). When the Pd loading was small (5 wt.-%), PdZn catalyst (PdZn-5) indicated similar catalytic actions. However, PdZn catalyst containing Pd in a larger content of 30 wt.-% (PdZn-30) showed different results: the COL selectivity was about 20% at low conversion but it increased with CAL conversion, reaching to > 50% at a conversion of 60%. The COL selectivity was likely to change depending on the concentration of a product of hydrocinnamaldehyde (HCAL). The coadsorption of HCAL should control the orientation of CAL molecules adsorbed on the PdZn-30 catalyst. This may assist the adsorption of CAL via its aldehyde group on the surface of catalyst, resulting in an increase in the COL selectivity. Unique catalysis of PdZn-30 may result from structural features of the surface of its large PdZn particles, which are different from those of PdZn-5 having smaller PdZn particles.

Ambient aging effects on the effective energy gap of ZnO thin films

“…[1][2][3] In particular, its polar surfaces perpendicular to the c-axis [(000 1) O-polar and (0001) Zn-polar] try to reconstruct, dissociate water, and adsorb the resulting hydrogen or accumulate free carriers from the bulk in order to become stable, [4][5][6][7] which are very appealing properties for catalysis or gas sensing. [8][9][10] Since these effects influence the amount of accumulated charge on the surface, they can dramatically affect the band bending over a distance of tens of nanometers. 11,12 This has triggered intensive research during the last years with the aim of tuning the band bending properties of ZnO single crystals.…”

Review on heterogeneous catalysts for the synthesis of perfumery chemicals via isomerization, acetalization and hydrogenation

“…During hydrogenation reaction, cinnamaldehyde was adsorbed on the catalyst surface via C = C bond for hydrogenation to hydrocinnamaldehyde. The bimetallic PdZn alloy promoted the preferential hydrogenation of the aldehyde group, thus increasing the selectivity towards cinnamyl alcohol 165 . Pan, et al 166 also reported the synergistic effect between Pt and FeO x on Al 2 O 3 @SBA15 catalysts for the hydrogenation of cinnamaldehyde.…”

“…The activity of metal nanoparticles for chemoselective hydrogenation reaction was further improved via the formation of bimetallic nanoparticles. Fujita et al investigated the role of PdZn bimetallic nanoparticles in altering product selectivity from cinnamaldehyde hydrogenation 165 . Hydrogenation reaction was carried out using Pd/ZnO and PdZn/ZnO nanoparticles, with toluene as solvent at 80℃ under H 2 4.0 Mpa.…”

Tunable Selective Hydrogenation of Cinnamaldehyde by Capped Pt/Pd Nanoparticles Supported on Carbon Nanotubes

“…[7] For example, the exposure of metal crystal facets greatly affects the selectivity through the competitive adsorption of the C=C bonds and C=O bonds on the metal surface. Many previous works focused on the regulation of active metal, including the size, [8] the synergistic effect of polymetals [9] and the metal-support interaction. Many organic compounds can bind on the surface of noble-metal nanoparticles (NPs) to enhance stability, [10] change micro-structure, [11] control size distribution, [12] and increase activity.…”