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Au-Pd bimetallic nanoparticles (NPs) supported on SnNb2O6 ultrathin nanosheets (SN) were developed as multifunctional photocatalysts for the selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HCAL) under visible light irradiation. A representative catalyst (Au6-Pd1/SN) exhibits optimum performances with 99.8% conversion and 91.0% selectivity. The structure and surface properties of the prepared samples were revealed by SEM, TEM, BET, TPD, XPS, and EPR. The results of in situ FTIR spectra and NH3-TPD reveal that the rich surface Lewis acid sites on SN can chemisorb and activate CAL via the C = C…Nb coordination. EPR experiments indicate that H2 would dissociate to activated H atoms on Pd NPs following a photopromoted surface catalytic process. Experimental results suggest that Au NPs reduce the over hydrogenation of HCAL by inhibiting the formation of Pd-H species. The superior catalytic performance is attributed to a synergistic effect of Au, Pd NPs and SN. Finally, a possible synergetic mechanism for Au-Pd/SN is proposed to illustrate the photocatalytic process. This work offers a reference to guide a novel and more effective photocatalyst design for precise organic synthesis driven by sunlight.

Mesoporous TS-1 microspheres (MTS-1-MS) were applied to load Pt-Fe bimetallic components with different Fe/Pt molar ratios for the liquid-phase selective hydrogenation of cinnamaldehyde (CAL) to produce cinnamyl alcohol (COL). Combining the XRD and XPS characterization results, Fe dopant co-existed as PtFe fcc alloy or FeOx species, which modified the electronic properties of Pt active sites through the electron transfer from Fe to Pt, therefore, the catalytic performance was improved remarkably with the Fe-doped Pt/MTS-1-MS catalyst. As a result, the PtFe0.25/MTS-1-MS-350 catalyst, which contains Fe amount with a Fe/Pt molar ratio of 0.25 and was calcined at 350 °C before reduction in hydrogen at 400 °C, furnished 95.7% CAL conversion and 89.2% COL selectivity with an initial activity (in terms of TOF value) reaching 19440 h−1, much better than its analogue Pt/MTS-1-MS-350, which only showed 56.6% CAL conversion and 74.4% COL selectivity under the same conditions. To the best of our knowledge, it is one of the most active Pt-Fe bimetallic catalysts up to now. Moreover, the PtFe0.25/MTS-1-MS-350 catalyst can also be cycled for at least 9 times without obvious loss in activity or COL selectivity. Furthermore, theoretical calculations based on several simplified surface models were conducted using the density-functional theory (DFT) to reveal the differences in electronic structures and geometric properties caused by Fe dopant and to explain the reason why C O hydrogenation was preferential on the PtFe0.25/MTS-1-MS-350 catalyst from the perspective of CAL adsorption and COL desorption on/from Pt-Fe surface.

Due to coexistence of two conjugated unsaturated functional groups in cinnamaldehyde (CAL), exploring efficient catalysts with desirable selectivity to highly value-added products is still challengeable for the selective hydrogenation of CAL. Herein, NixFe1-xAl2O4+δ spinel composite metal oxides (SCMOs) supported Pt catalysts were developed and proved to be active and selective for the selective hydrogenation of CAL. Moreover, the selectivity switch can be realized just by changing the Ni/(Fe + Ni) molar ratios in NixFe1-xAl2O4+δ SCMOs. As a result, the excellent cinnamyl alcohol (COL) selectivity (~92.2%) and hydrocinnamaldehyde (HCAL) selectivity (~80.7%) were achieved on Pt/FeAl2O4+δ and Pt/NiAl2O4+δ, respectively. Based on the kinetic investigation of further hydrogenation of semi-hydrogenated product, the reason for the selectivity switch with Pt/NixFe1-xAl2O4+δ was revealed. In combination with detailed characterization, the excellent COL selectivity on Pt/FeAl2O4+δ can be attributed to more Pt(1 1 1) facets and FeOx species which can facilitate the preferential activation of C O bonds; while the high HCAL selectivity on Pt/NiAl2O4+δ is owing to the fact that there are more low coordinated active sites and two neighbouring Pt sites.

In this work, an alloy catalyst with C@PtGa interface structure was synthesized under H2/CO2 atmosphere by using PtCl62−/MgAlGa-LDHs as precursor. Cs-corrected STEM, EELS and CO chemisorption clearly confirmed the PtGa alloy particles were well covered by amorphous carbon thin layer with the characteristics of porous and permeable. In selective cinnamaldehyde hydrogenation, the C@PtGa catalyst showed a higher selectivity than both bare PtGa catalyst and Ga2O3@PtGa catalyst. The enhanced selectivity was attributed to the geometric decoration of carbon layer as well as the formation of electron-rich Pt sites at C@PtGa interface, which optimized the adsorption mode of cinnamaldehyde. More importantly, the permeable characteristic of carbon layer which maintained the accessibility of reactants to the Pt sites, contributed to the higher conversion compared to Ga2O3@PtGa catalysts with traditional oxide interface layer. Additionally, C@PtGa catalyst exhibited a good reusability with conversion of 88.3% and selectivity of 91.9% after 5 cycles. This work provides an alternative way to realize the boost of activity and selectivity in selective hydrogenation of C=O bonds by intelligently fabricating non-oxides@metal interface.

The selective hydrogenation of cinnamaldehyde (CAL) is an extremely important transformation. Herein, oxygen functionalized carbon nanotubes (oCNTs) supported a series of PtxCoy bimetallic nanoparticles (NPs) with varied Pt to Co ratios were synthesized. The introduction of Co significantly affects the electronic structure of Pt NPs, which clearly promotes the selectivity to cinnamyl alcohol (COL). Among all PtxCoy-oCNTs catalysts, PtCo3-oCNTs exhibited the best catalytic performance and a selectivity of over 76% towards COL at a CAL conversion of 99% was obtained. Further characterization of the fresh, used and cycled catalysts revealed that the NP structures were stable and did no change. The structural evolutions during the catalytic reaction were also investigated by identical location transmission electron microscopy (IL-TEM) method in detail, which found that the deactivation of PtCo3-oCNTs catalyst during the cycle experiment results from the agglomeration and detachment of PtCo3 NPs.

HPZSM-5 with hierarchical porous structure obtained via partial desilication of commercial ZSM-5 was proved to be a suitable support for Pt nanoparticles towards the liquid-phase selective hydrogenation of cinnamaldehyde (CAL) to yield cinnamyl alcohol (COL). Compared with Pt/ZSM-5, Pt/HPZSM-5 showed improved catalytic performance although the improvement seems to be very limited. After doping Fe to Pt/HPZSM-5 with a Fe/Pt molar ratio of 0.25, the PtFe/HPZSM-5 catalyst gave much further enhanced CAL conversion. Under the optimized conditions, a 97.9% CAL conversion with 87.6% selectivity to COL was achieved with the PtFe/HPZSM-5 catalyst. The initial activity (in terms of TOF value, defined as molecules of CAL converted per surface atom of Pt per second) reached about 3.41 s−1 with the PtFe/HPZSM-5 catalyst, one of the highest values up to now to our best knowledge. Moreover, the PtFe/HPZSM-5 catalyst can be recycled for at least 9 times without obvious loss in activity or selectivity to COL. The effect of partial desilication and Fe doping on the catalytic performance of PtFe/HPZSM-5 was discussed based on the characterization results using a series of techniques.

CoxFe1-xAl2O4+δ composite oxides were prepared using a sol-gel method with glucose as hard template. Pt nanoparticles supported on CoxFe1-xAl2O4+δ were employed for the liquid-phase selective hydrogenation of cinnamaldehyde (CAL) to yield the desired cinnamyl alcohol (COL). The activity increased with the x value; while the selectivity to COL almost kept above 90% despite of different x values. Upon investigation of kinetic behaviour with Pt/Co0.5Fe0.5Al2O4+δ as a model catalyst, the initial activity (in terms of TOF, defined as the converted CAL molecules per surface Pt atoms per second) of 4.1 s−1 was furnished. As for the selectivity to COL, it almost kept around 95% at whatever CAL conversions despite of the reaction temperatures. Pt/Co0.5Fe0.5Al2O4+δ catalyst can also be recycled for at least 10 times without obvious loss in activity or selectivity toward COL. This suggests that the active sites on the Pt/Co0.5Fe0.5Al2O4+δ catalyst preferentially adsorb and activate CAL via the terminal carbonyl groups. XPS analyses, H2-TPR, and CO-IR studies reveal that the intimate contact of Pt nanoparticles with FeOx or CoOx plays an important role in determining the catalytic performance of the Pt/CoxFe1-xAl2O4+δ catalysts. The Pt δ+/Pt0 ratio increased with the x value so that the Pt/CoAl2O4 was the most active among the Pt/CoxFe1-xAl2O4+δ catalysts.

Graphene is an ideal model support to investigate the influence of carbon surface chemistry on catalytic reactions. Here a mild hydrothermal method was developed to synthesize graphene-supported iridium nanocatalysts from graphene oxide. By simply varying the hydrothermal conditions, the physicochemical properties of catalysts can be tuned, which can further affect their catalytic performances. Catalysts obtained at higher H2 pressure during hydrothermal process performed higher catalytic activities for hydrogenation of both p-chloronitrobenzene and cinnamaldehyde, benefiting from their higher reduction degrees of iridium nanoparticles. Interestingly, catalysts obtained at lower hydrothermal temperature performed higher activities for p-chloronitrobenzene hydrogenation but lower activities for cinnamaldehyde hydrogenation, due to their distinct surface chemistry of graphene. Through systematic characterizations on 11 catalysts prepared under various conditions, we found that lower hydrothermal temperature endows graphene with larger lateral dimension and more in-plane oxygenated surface groups, which facilitates the accessibility of nitro groups to catalyst surface via H-bond interaction as confirmed by density functional theory calculations. This is not true for cinnamaldehyde, of which adsorption on graphene via π-π stacking interaction is favorable for its hydrogenation.

A multifunctional photocatalyst is constructed based on Cu-Cu2O hybrid and monolayer H1.4Ti1.65O4·H2O nanosheets via an in situ photo-deposition process (Cu-Cu2O/TNS). The prepared sample enables the oxidation of cinnamyl alcohol to cinnamaldehyde with over 95% of selectivity under visible light irradiation using molecule O2 as the oxidant. In situ FTIR spectra suggest that the Lewis acid sites in TNS would selectively adsorbed the hydroxyl of cinnamyl alcohol forming surface C O∙∙∙Ti O coordination species. UV-DRS spectra reveal that light adsorption of TNS can be extended to visible light region due to the interface charges transfer from C OH to Ti O via the surface coordination, resulting in the activation of OH in alcohol. In situ ESR further indicates that directional interface charge transfer induces the charge enrichment in Ti atoms of TiO6, facilitating O2 adsorption. XAFS results reveal that the hybrid electronic states of Cu-Cu2O efficiently improve the interface electronic transfer kinetics to inhibit the intramolecular hydrogen transfer for dominating the selectivity towards cinnamaldehyde. This work highlights the synergistic effect of surface coordination-activation-photocatalysis for selective photosynthesis of fine chemicals.

A series of carbon nanotube (CNT)-supported bimetallic PtFe nanoparticles were synthesized and employed as catalysts for hydrogenation of cinnamaldehyde in pure water. A synergy between water and bimetallic PtFe catalysts has allowed the efficiently selective production of cinnamyl alcohol. With the aid of water, an initial reaction rate of >1200 h−1 and a high selectivity of >97%, as well as a good cycling stability, were achieved with a Pt3Fe/CNT catalyst under mild reaction conditions. Isotopic labeling studies and theoretic calculation results demonstrated that the water-involved hydrogen-exchange pathway occurred with a lower energy barrier, which coexisted with the pathway of direct H2 dissociation–hydrogenation. This work also suggested that water participated in the catalytic hydrogenation reaction by serving as a hydrogen-exchange bridge.

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) was conducted over a series of FeO x -doped Pt catalysts supported on a 15 wt% Al 2 O 3 @SBA-15 composite (15AS). It was found that the addition of FeO x to the catalyst greatly improved its performance. With an optimal Fe/Pt molar ratio of 0.25, the PtFe 0.25 /15AS catalyst reached a maximum reaction rate (defined as moles of converted CAL per gram of Pt per hour) of 13.93 mol g Pt −1 h −1 with 76.9% selectivity to COL. Additionally, the PtFe 0.25 /15AS catalyst afforded the highest TOF value (defined as moles of converted CAL per mole of Pt active sites per second) of 1.54 s −1 . X-ray photoelectron spectroscopy analyses and H 2 temperature-programmed reduction and CO diffuse-reflectance infrared Fourier-transformation spectroscopy studies reveal that there is strong interaction between Pt nanoparticles and Al 2 O 3 @SBA-15 composites and also between Pt and FeO x , resulting in Pt species with a positive charge being dominant in PtFe 0.25 /15AS catalysts. Therefore, Pt species with positive charges, together with FeO x species, are beneficial for preferential adsorption and activation of carbonyl bonds of CAL, so that the activity and selectivity to COL were improved by PtFe x /15AS catalysts ( x represents the Fe/Pt molar ratio).

Allylic alcohols, important intermediates in fine chemical industry, are typically obtained through chemoselective hydrogenation of α,β-unsaturated aldehydes. Here we show that UiO-66, a zirconium-based metal–organic framework can be used in the chemoselective hydrogenation of cinnamaldehyde, both under high hydrogen pressure as silver nanoparticle support, and as transfer hydrogenation catalyst in the Meerwein–Ponndorf–Verley (MPV) reduction. A recyclable 10 wt% Ag/UiO-66 catalyst reached complete conversion after 6 h and 50 bar of H2 with 66% selectivity for cinnamyl alcohol in the inert solvent N,N-dimethylacetamide (DMA). Pure UiO-66 as MPV catalyst with isopropanol reached complete conversion with >90% selectivity after 24 h at 120 °C. The substrate scope was extended to citral and carvone, two α,β-unsaturated carbonyl compounds that are harder to reduce selectively. Introduction of a NO2-functional group into the UiO-66 linker to increase the Lewis acidity was clearly beneficial for the conversion of carvone.

Pt nanoparticles supported on sheetlike mixed metal oxides (MMO) derived from layered double hydroxides are found to be highly efficient catalysts for the selective hydrogenation of cinnamaldehyde. A series of characterizations are employed to investigate the structure and composition of the support and catalyst. Divalent species have a significant influence on the activity and selectivity. CoAl MMO-supported catalysts achieve an increase in both conversion and selectivity to cinnamyl alcohol through the formation of PtCo alloy on the surfaces of catalysts during preparation. A possible reaction path is proposed. The effects of Co/Al ratio and calcination temperature on catalytic performance are researched in this work.

Ru-based nanoparticles were deposited on carbon nanotubes and graphene via an organometallic approach involving mixed-metal clusters modified with appropriate ligands. These ligands allowed either covalent or non-covalent π–π interactions with the carbonaceous surfaces. The immobilized clusters were then coalesced at different temperatures to give carbon-supported nanoparticles of different sizes. The obtained catalysts were tested in the selective hydrogenation of cinnamaldehyde. It was found that the nature of the metal(s), support nature, incorporation method and activation temperature all had a profound influence on activity and selectivity. Interestingly, the selectivity could be shifted from cinnamyl alcohol (COL) to hydrocinnamaldehyde (HCAL) by changing the reaction solvent. The best catalysts gave a very high selectivity in cinnamyl alcohol, which is not the more thermodynamically favored product, and could be reused several times without loss of activity or selectivity.

For the purpose as stated in title, three Ru catalysts were prepared with the same treated carbon nanotubes. One has most of Ru nanoparticles confined inside the channels, and the other two have most of Ru nanoparticles outside through different preparation methods. Heat treating was performed to obtain another three catalysts. Characterization by X-ray photoelectron spectroscopy indicated that heat treating made Ru nanoparticles electron rich. Hydrogenation of benzene, p-chloronitrobenzene, and cinnamaldehyde was chosen as model reactions to evaluate all these catalysts. Electronic effect plays an important role in catalytic performance. The electron-rich Ru would be favorable for p-chloronitrobenzene hydrogenation, but unfavorable for benzene hydrogenation. For cinnamaldehyde hydrogenation, the electron-rich Ru would be favorable for adsorption of CO bond rather than CC bond and thus promoted the selectivity to cinnamyl alcohol. A confinement effect induced by the electronic effect has different influences on these substrates, and it can be enhanced by heat treating for all the reactions. Finally, we drew a correlation of electronic structures between catalysts and substrates accounting for these phenomena.

The catalytic performance of Ni/TiO2 and Ni-Ir/TiO2 catalysts in the selective hydrogenation of cinnamaldehyde (CAL) has been investigated. The Ni-Ir/TiO2 presented higher activity than the Ni/TiO2. Here, we studied and gave some insights into the interaction between Ni and Ir species and the role of Ir using X-ray diffraction (XRD), transmission electron microscope (TEM), hydrogen temperature-programmed reduction (H-2 TPR), hydrogen temperature-programmed desorption (H-2 TPD), and X-ray photoelectron spectroscopy (XPS). The size of Ni particles on the Ni-Ir/TiO2 was 10.1 nm, smaller than that (12.7 nm) on the Ni/TiO2. The reducibility of Ni was improved by addition of a small amount of Ir, as confirmed with the H-2 TPR analysis. The Ni-Ir/TiO2 could be reduced at a temperature of 352 degrees C, which is lower than the temperature for Ni/TiO2 (385 degrees C); moreover, a new reduction peak appeared at 240 degrees C due to the stronger interaction of Ni-Ir species, which was certified by XPS analysis. The H-2 TPD results indicate that the hydrogen spillover effect may occur in Ni-Ir/TiO2. The electronic structure of the surface Ni atoms was modified upon addition of Ir, resulting in an enhanced activity of the Ni-Ir/TiO2 catalyst, about four times as high as that of the Ni/TiO2 catalyst. (c) 2013 Elsevier Inc. All rights reserved.

This work reports a striking enhancement of catalytic performance of gold nanoparticles (NPs) with average diameter of 3.2 nm partially (ca. 32–40%) confined in the cavity of carbon nanotubes (CNTs) for the gas-phase hydrogenation of 1,3-butadiene (BD), as well as liquid-phase hydrogenation of cinnamaldehyde (CAL). The reaction rates and turnover frequencies of the CNTs confining gold NPs exceed those with a similar size deposited on the outer surface of CNTs and activated carbon by more than one to two orders of magnitude in both two reactions. The selectivity to monobutenes and hydrocinnamaldehyde is up to 100% and 91% at 100% and 95% conversions of BD and CAL, respectively. Au/CNTs catalysts were characterized in depth to establish their structure–property relationship. The peculiar interaction of confined gold NPs with the surface of CNTs facilitates the dissociation/activation of H2, which is the rate-determining step for hydrogenation reactions demonstrated by kinetic studies.

Selective liquid phase hydrogenation of cinnamaldehyde is reported, for the first time, over CeO2, ZrO2, and CeO2–ZrO2-supported Pt catalysts. Cinnamyl alcohol is the selective product. These catalysts are highly active and selective even at 25 °C and found to be superior to most of the hitherto known supported Pt catalysts. Alkali addition (NaOH) has enhanced the performance of these catalysts. At an optimized reaction condition, 95.8% conversion of cinnamaldehyde and 93.4% selectivity of cinnamyl alcohol have been obtained. Acidity of the support (due to the presence of ZrO2 component) and higher electron density at Pt (due to CeO2 component) are attributed to be responsible for the superior catalytic activity of Pt supported on CeO2–ZrO2 composite material.

The homogeneous complex Ru(PPh3)3Cl2 has been immobilized onto three different carbon materials: graphite, carbon nanofibers, and graphite oxide (GO). All the supports were previously functionalized with (bis(2-aminoethyl)amine). For graphite oxide, a second functionalization strategy using N-[3-(trimethoxysilyl)propyl]-etylenediamine (TPEN) was also followed. XRD, NMR, TG, TPD, DRIFTS, and XPS techniques were applied for the characterization of the functionalized supports and the hybrid catalysts. The hybrid catalysts have been tested in the hydrogenation of cinnamaldehyde and, although less active, they showed selectivities comparables to that for the homogeneous complex. The different behavior observed for the samples after recycling and reusing can be related to the ligand-support interaction type. While activity and selectivity are preserved for the Ru grafted on the covalent-functionalized GO–TPEN, variations in activity and selectivity are observed for the amine-functionalized samples.

A series of catalysts consisting of ZrO2 in pure form or modified by doping with boron or an alkaline-earth metal to enhance their acid and basic properties, respectively, were prepared and used in the Meerwein–Ponndorf–Verley reduction of cinnamaldehyde with 2-propanol, where they exhibited moderate activity and a high selectivity (up to 98%) towards cinnamyl alcohol. The catalyst preparation procedure and its modification (viz. doping with boron or an alkaline-earth metal) were found to delay crystallization and increase the number of hydroxyl groups present on the catalyst surface, and hence its catalytic activity. The surface acid and basic properties of the catalysts were determined by pyridine and carbon dioxide chemisorption, respectively. The most active sites in the studied reaction are seemingly proton (Bronsted) acid sites of medium–high strength formed by modification of the ZrO2 with boron; however, the increased activity thus obtained is accompanied by a loss of selectivity towards cinnamyl alcohol. Modifying ZrO2 with an alkaline-earth metal enhances its basicity, thereby reducing its catalytic activity and increasing its selectivity for the unsaturated alcohol.

Bimetallic platinum–tin and platinum–gallium catalysts supported on carbon nanofibers (CNF) were prepared via reductive deposition precipitation and impregnation. Detailed EXAFS, TEM-EDX and XPS studies showed that reductive deposition precipitation resulted in a close contact of tin with platinum. These bimetallic catalysts displayed an improved selectivity for cinnamaldehyde hydrogenation towards the desired cinnamyl alcohol as compared to the monometallic platinum catalyst and a bimetallic catalyst prepared by impregnation in which such a close interaction was absent. The general applicability of reductive deposition precipitation as synthesis technique was demonstrated using tin and gallium as promoters.

An enhancement of the catalytic performance of platinum in the liquid phase hydrogenation of cinnamaldehyde has been achieved by modifying a ZnO support by addition of Cr(III) cations. The addition of chromium improves the structural properties of the support (larger surface area) and increases its reducibility, and resulted in a better Pt dispersion. The presence of chromium in the support enhanced the overall catalytic activity, and improved the high selectivity towards the unsaturated alcohol. The increase of the reduction temperature from 473 K to 623 K produces an impressive decrease in the turnover frequency for Pt/ZnO, whereas this value remains practically unmodified for Pt/Cr–Zn. The higher reduction temperature reduces the overall activity in both catalysts, but improves selectivity towards the unsaturated alcohol. The present 5 wt% Pt/Cr–ZnO catalyst showed the best results (in terms of selectivity) published until now without use of reaction promoters. The improved performance of this catalyst is ascribed to an adequate metal–support interaction and to the higher reducibility of the support that opens the possibility of alloy formation.

A novel mesoporous Co–B amorphous alloy was synthesized by controlling the chemical reduction of Co2+ with BH−4 in the presence of surfactant. During liquid-phase cinnamaldehyde hydrogenation, mesoporous Co–B exhibited higher activity and selectivity to cinnamyl alcohol compared with nonporous Co–B. This higher activity was attributed to its high surface area and mesopores, which facilitated diffusion and adsorption of reactants, whereas its better selectivity was ascribed to the uniform distribution of Co active sites and their connection via a porous network, which facilitated the competitive hydrogenation of CO against CC coexisting in the cinnamaldehyde molecule, because CC adsorption was inhibited due to steric hindrance.

Uniform spherical Co-B amorphous alloy nanoparticles were prepared by ultrasound-assisted reduction of Co(NH3)2+6 with BH−4 in aqueous solution, and the particle size was adjusted by changing either the ultrasound power or the ultrasonication time. During liquid-phase cinnamaldehyde (CMA) hydrogenation, the as-prepared Co-B catalyst exhibited much higher activity and better selectivity to cinnamyl alcohol (CMO) than the regular Co-B obtained by direct reduction of Co2+ with BH−4. The higher activity can be attributed to both the higher dispersion of Co active sites ( S Co ) and the higher intrinsic activity ( R S ). The higher selectivity can be attributed to both the uniform Co-B amorphous alloy particles and the strong electronic interaction between Co and B, which enhances the competitive adsorption of C O group against C C group in the CMA molecule. Meanwhile, the stronger adsorption for hydrogen on Co active sites was more favorable for C O hydrogenation in comparison with the C C hydrogenation.

Zr-zeolite beta with Si/Zr ratio of 75–200, as well as zeolite beta with both Zr (Si/Zr ratio of 100) and Al (Si/Al ratios of 100 and 25), were synthesized in a seeded synthesis using HF as the mineralizer. The Al-free Zr-zeolite beta was found to catalyse the MPV reduction of α , β -unsaturated aldehydes to the corresponding alcohols with high selectivity. In the reduction of cinnamaldehyde to cinnamyl alcohol, TONs of 55–77 mol mol−1Zr h−1 were obtained with selectivity > 98 % . Zr-zeolite beta maintained good activity and selectivity in the presence of water and benzoic acid. Reuse of the catalyst by washing with 2-propanol or recalcination led to recovery of activity. For the Al-containing Zr-zeolite beta, 27Al NMR spectra showed that Al was incorporated into the zeolitic framework. This is in agreement with pyridine adsorption studies in which Bronsted acidity was detected. However, the increased acidity decreased the selectivity in the MPV reduction of cinnamaldehyde as a significant amount of 1-cinnamyl 2-propyl ether was formed as a byproduct. Hence, Al-free Zr-zeolite beta is a useful chemoselective catalyst for the MPV reduction of α , β -unsaturated aldehydes.

Carbon nanofiber-supported platinum catalysts were studied to establish the influence of the support surface composition on their performance in the liquid-phase hydrogenation of cinnamaldehyde. By acid–base titration, XPS, and TGA-MS, the number of oxygen-containing surface groups was determined in oxidized carbon nanofiber samples and in platinum catalysts pretreated at 473–973 K. TEM, EXAFS, and H2-chemisorption studies showed the presence of a narrow and stable platinum particle-size distribution (1–2 nm). The overall catalytic activity increased by a factor of 25 after treatment at 973 K, which is tentatively related to the decreasing amount of oxygen of the carbon fibers. With XPS and H 2-chemisorption experiments carried out at 308 K no clear evidence was found for a change in the electronic structure of the platinum particles induced by the oxygen-containing groups present on/in the surface of the carbon nanofibers. A linear decrease of the hydrogenation activity with an increase of the number of acidic groups on the carbon nanofiber support was found. Therefore, it is suggested that hydrogenation is assisted by adsorption of cinnamaldehyde on the carbon support after removal of the oxygen-containing surface groups.

Carbon-nanofiber-supported ruthenium catalysts were employed to study the influence of oxygen-containing surface groups on catalytic performance in the liquid-phase hydrogenation of cinnamaldehyde. The carbon nanofibers were oxidized to introduce oxygen-containing groups and the metal precursor was applied using homogeneous deposition precipitation. After reduction the catalysts were heat-treated in nitrogen at different temperatures to tune the number of surface oxygen functional groups. TEM and chemisorption studies showed the presence of a narrow and stable particle-size distribution (1–2 nm) even after heat treatment at 973 K. The overall specific activity increased by a factor of 22 after treatment at 973 K, which is related to the decreasing number of oxygen-containing groups. The cinnamyl alcohol selectivity decreases from 48 to 8% due to enhanced rate of hydrocinnamaldehyde production with increasing heat treatment. This unambiguously demonstrates the metal–support interaction, which involves support surface-oxygen functionalities that affect the metal activity and selectivity. The precise nature of this interaction has yet to be elucidated.