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Carbon dots (CDs) with a size range of 0.2 to 2 nm were prepared using a hydrothermal treatment of sucrose and oleic acid. The as-synthesized CDs were used to reduce H2PdCl4 to metallic Pd nanoparticles with dPd = 9.3 ± 3.7 nm, as confirmed by PXRD and HRTEM data. Pd particles were made to be larger than the CDs, to observe any inverse support effects, however, TEM data revealed that the CDs were transformed to carbon sheets in the reduction reaction at 100 °C. The synthesized Pd-CDs catalysts (0.81 wt. % loading) and CDs were both tested for the liquid phase hydrogenation of cinnamaldehyde. The influence of mass, temperature, and hydrogen flow rate on the activity and selectivity of the CDs and Pd-CDs catalyst on the hydrogenation of cinnamaldehyde was investigated. The CDs gave a cinnamaldehyde conversion (40%, 4 h) with selectivity towards the reduction of the C = O bond (cinnamyl alcohol) while the Pd-carbon catalyst was only selective to the reduction of the C = C bond (conversion 78%) indicating the dominance of Pd in the reaction. Post analysis of the deactivated catalysts indicated formation of carbon sheets and sintering of the Pd nanoparticles. It is thus shown that the presence of Pd induces the CDs to carbon sheet formation and thus indicates the limited use of CDs as a support for the olefin hydrogenation reaction with the CDs produced carbon support. This finding has implications for other studies using CDs as supports. [ABSTRACT FROM AUTHOR]

Selective catalytic hydrogenation of cinnamaldehyde is an important chemical reaction process for the preparation of high-value chemical products. However, the hydrogenation of the C=O group in cinnamaldehyde is not affected by the thermodynamics, which causes the C=O double bond in its molecular structure difficult to be hydrogenated. In this work, Pt-Fe/Fe-NTA materials were prepared by a simple impregnation reduction method, and used as highly efficient catalysts for chemoselective hydrogenation of cinnamaldehyde. Built on a series of characterization technologies including XRD, FT-IR, XPS, SEM, and HRTEM the micro-structure and properties of Pt-Fe/Fe-NTA nanocatalysts were studied in detail. The experimental results suggest that the excellent catalytic performance of Pt-Fe/Fe-NTA catalysts mainly comes from the electron-rich property of the active center Pt and the existence of the surface Fe3+ species, which both contribute to enhance the chemisorption of the C=O double bond in cinnamaldehyde and to improve the selectivity of cinnamyl alcohol. Under optimal reaction conditions, a cinnamaldehyde conversion of 90.8% and a selectivity to cinnamyl alcohol of 90.9%, respectively were achieved, with the turnover frequency up to 1489 h−1. In addition, a possible catalytic reaction mechanism of hydrogenation of cinnamaldehyde on Pt-Fe/Fe-NTA catalysts was proposed. Pt nanocatalyst supported by Fe-NTA nanorods was synthesized. The obtained Pt-Fe/Fe-NTA catalyst exhibits excellent catalytic activity (TOF=1489 h-1) and superior catalytic selectivity to cinnamal alcohols (90.9%) at 40 °C for chemoselective hydrogenation of cinnamaldehyde [ABSTRACT FROM AUTHOR]

The selective hydrogenation of α,β-unsaturated aldehydes plays a crucial role in industrial production, and an efficient non-noble metal catalyst for it has been pursued to reduce the cost. Herein, we report an amorphous nickel phosphide for the selective hydrogenation of cinnamaldehyde. Compared to crystalline nickel phosphide, amorphous nickel phosphide showed both high activity and high selectivity to target products. Its catalytic performance was also better than that of commercial Pd/C catalyst. In addition, initial P/Ni ratio was found to be an important factor to affect the activity of amorphous nickel phosphide. High initial P/Ni ratio led to high activity owing to small particles, high surface area and strong metallicity of as-synthesized catalyst. Moreover, excellent catalytic performances of amorphous nickel phosphide were observed in the selective hydrogenation of different α,β-unsaturated aldehydes and ketones. [ABSTRACT FROM AUTHOR]

Since hydrogenation of C=C bond in the cinnamaldehyde is thermodynamically favored, the selective hydrogenation of C=O group is challenging. Developing effective catalysts for this transformation has been hindered by the intrinsic disadvantages of traditional materials for decades. Hereby, we report the synthesis of the low dimensional Co based nanorods (NRs) as the effective platform for C=O groups hydrogenation in the conjugated compounds. The Pt/Co-NRs catalyst is simply fabricated by loading the Pt nano-particles (NPs) on the Co-NRs and the stability of the Co-NRs support is improved by coordination between the Pt NPs and the pyridinic N ring. Resorting to XRD, FT-IR, XPS, HRTEM, DTG-TG characterization methods, the catalytic mechanism for C=O bond hydrogenation has been proposed. The synergistic effects of K+ and OH− enhance the polarization of C=O group, leading to more adsorption of C=O groups on the Co-NRs so as to promote its hydrogenation performance. In the absence of spatial micropores in low dimensional Co based nanorods, the Pt/Co-NRs catalyst is more advantageous for mass transfer. Under optimal conditions, the conversion of cinnamaldehyde is 97.9% with 92.7% selectivity of cinnamyl alcohol within 3 h. In addition, the selectivity of cinnamyl alcohol changes slightly (only 2.4% fluctuations) after five recycle tests. [ABSTRACT FROM AUTHOR]

Uniform Au particles with a mean size of 1.9 nm were initially synthesized with polyvinyl alcohol (PVA) as protecting agent, and then deposited on MgO, AlO, TiO, FeO, CoO, ZnO and InO. After calcinations at 300 °C in air to remove PVA, Au particles were highly dispersed and immobilized on all the supports, displaying narrow diameter distributions and almost identical mean sizes of 2.5-3.2 nm. The Au-oxides catalysts were further used to catalyze selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL). It was found that the selectivity of COL was tightly related to the acidity/basicity of the Au/oxides catalysts. The catalyst with only acidic sites such as the Au/AlO catalyst gave very low selectivity of COL of 15%. The catalysts with only basic sites such as Au/MgO catalyst displayed medium selectivity of COL of 52%. Interesting, the Au catalysts with both acidic and basic sites such as the Au/InO and Au/ZnO catalyts exhibited the highest selectivity of COL of around 86%. The synergistic cooperation of acidic sites and basic sites should be responsible for preferential adsorption and activation of the C=O group than C=C group in CAL, and then preferential hydrogenation of C=O to COL. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Pt-Co alloy supported on SBA-15 catalysts (Pt-Co/SBA-15) were prepared by impregnation and NaBH reduction method. Their catalytic performances were investigated for selective hydrogenation of cinnamaldehyde. It was found that the formation of Pt-Co markedly enhanced the conversion to cinnamaldehyde and selectivity to cinnamyl alcohol compared with Pt/SBA-15. Meanwhile, the Pt-Co/SBA-15-0.6 catalyst performed the best catalytic activity that 71 % CAL conversion and 91 % selectivity to COL were attained. Moreover, no obvious deactivation was observed after using 4 times for Pt-Co/SBA-15-0.6. This improvement was contributed to the formation of Pt-Co alloy, which increased the amount of the Pt species on the catalysts. Graphical Abstract: Pt-Co alloy supported on SBA-15 catalyst shows excellent catalytic selective hydrogenation of cinnamaldehyde to cinnamyl alcohol [ABSTRACT FROM AUTHOR]

Platinum-antimony and platinum-bismuth deposited on activated carbon were prepared by various methods. The materials were characterized by nitrogen physisorption, X-ray diffraction and high-resolution transmission electron microscopy. The samples were tested as catalysts for the selective oxidation of cinnamyl alcohol to cinnamaldehyde, using HO as the oxidant. 5%Pt-5%Sb/C shows selectivities in excess of 98 % in both water and toluene as the reaction medium. In comparison, state-of-the art bismuth catalysts give selectivities of 73-95 % (in water) and 84 % (in toluene). Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Magnetically responsive Pd/FeO@C catalysts have been successfully prepared by depositing Pd nanoparticles onto the surface of FeO@C composites. Various techniques such as XRD, SEM, TEM, SQUID etc. have been used to characterize the composite catalysts. The obtained catalysts, consisting of core-shell structured microspheres with high uniformity, show a good superparamagnetic property. The selective hydrogenation of cinnamaldehyde on the magnetic catalysts has been investigated, achieving about 70 % selectivity to hydrocinnamaldehyde at 100 % conversion. Moreover, the magnetic catalyst can be easily recovered under an external magnetic field and reused for seven cycles without any degradation in activity. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Pt-based bimetallic nanoparticles supported on reduced graphene oxide were prepared by a facile NaBH reduction and chemically probed in the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol (CAO). Compared with other metals (Fe, Ni, Cu, Zn), Co effectively promoted the catalytic performance. When the mass ratio of Pt:Co was 5:1, the selectivity to CAO was 89.5 % with 94.6 % conversion, which were higher than exclusively using Pt catalyst. The enhanced selectivity and activity might be attributed to the change of the electronic environment on Pt metal surface through metal-metal interaction. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Pd or Pt promoted CeO 2–ZrO 2-supported Ni catalysts exhibited superior catalytic activity to the hitherto known Ni catalysts for liquid-phase hydrogenation of cinnamaldehyde at moderate conditions. Under similar experimental conditions, the unpromoted catalyst was selective for hydrocinnamaldehyde product (C=C hydrogenation) whereas the promoted catalyst yielded 3-phenyl propanol (C=C and C=O hydrogenation product). Enhanced dispersion of Ni was the cause for higher activity of the promoted Ni catalysts. Graphical Abstract: Ni/CeO 2–ZrO 2 promoted with Pd/Pt showed high catalytic activity for liquid phase hydrogenation of cinnamaldehyde. The activity of these catalysts is superior to the hitherto known Ni catalysts.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The liquid phase selective hydrogenation of cinnamaldehyde has been investigated on cobalt (15 wt%) impregnated on alumina, silica and various phases of titania supports. The multiple reduction stages observed in the TPR studies suggest the presence of cobalt aluminate/silicate/titanate species, and DRIFT spectra results seem to corroborate this observation. An optimum level of conversion and selectivity to cinnamyl alcohol was observed at 120 °C and 10 kg/cm hydrogen pressure. Co/TiO exhibited a greater conversion (47.4%) and selectivity to cinnamyl alcohol (58%) than Co/AlO and Co/SiO which may be attributed to the presence of TiO ( x < 2) species on the catalyst surface and to the preferential adsorption of C=O on the catalyst surface. The stability of Co/TiO was found to be better than Co/AlO and Co/SiO. Between the various phases of titania (high surface area, anatase and rutile), the crystalline phases exhibited a better conversion and selectivity to cinnamyl alcohol, while the stability was found to be better for high surface area titania. Graphical Abstract: The liquid phase selective hydrogenation of cinnamaldehyde has been investigated on cobalt impregnated on AlO, SiO and TiO supports. The observed trend for conversion and selectivity to cinnamyl alcohol was Co/TiO > Co/SiO > Co/AlO. The hydrogenation of CMA is believed to preferentially proceed via adsorption of C=O on the surface of Co/TiO.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Pt- and Pt-Fe based catalysts on zeolite P (ZP) support have been prepared and widely characterized by surface area and porosity, XRD, SEM, TEM, TPR, in order to investigate their morphological and microstructural properties. The catalysts have been tested in the selective liquid-phase hydrogenation of cinnamaldehyde. Kinetic tests have shown the beneficial effect of Fe promoter on the catalysts behaviour towards the selective formation of cinnamyl alcohol (85% selectivity to 90% conversion). The ZP supported catalysts have been compared with a catalyst supported on P-zeolitized Fe containing pumice (Z-PM), confirming the role of Fe Lewis acid site in promoting the reactivity of zeolite P-based materials. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Selective hydrogenation of cinnamaldehyde over Pd (2 wt%) supported on CeO ZrO and CeO-ZrO catalysts is reported for the first time. In general, the olefinic (C=C) group of cinnamaldehyde is preferentially hydrogenated compared to the carbonyl (C=O) group. This selectivity preference could, however, be altered or reversed by adding alkali additives to the catalyst. The influence of additive on the structure and redox properties of the active sites and correlation of that with selective hydrogenation activity is investigated. Graphical Abstract: Selective hydrogenation of cinnamaldehyde over Pd (2 wt%) supported on CeO ZrO and CeO-ZrO catalysts is reported for the first time. Alkali additives influence the selectivity for hydrogenation of olefinic (C=C) and carbonyl (C=O) groups of cinnamaldehyde. The influences of additive on the structure and redox properties of the active sites and correlation with selective hydrogenation activity are reported.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The vapour phase hydrogenation of cinnamaldehyde over Ni loading γ-Al2O3 catalysts was performed at 1 atm and 300 °C in a fixed-bed reactor. The major product was hydrocinnamaldehyde. Unexpected products of styrene and ethylbenzene due to new reaction pathway of hydrodeformylation were observed. The results indicated that Ni metal was the active centers and the catalytic activity was parallel to the Ni surface area. The stability of TOF values implied that the cinnamaldehyde hydrogenation over Ni/γ-Al2O3 catalysts was a structure insensitive reaction. [ABSTRACT FROM AUTHOR]

Highly ordered Ru-containing mesoporous carbons (Ru-OMC) were for the first time synthesized by a one-pot method. Comparing with our previously reported Ir-OMC, the Ru precursor must be added after the formaldehyde was consumed by polycondensation with resorcinol to obtain a small particle size. The resultant Ru-OMC samples with different Ru contents were characterized with X-ray diffraction (XRD), N2 adsorption-desorption, and Transmission electron microscopy (TEM). The results evidenced the formation of highly ordered mesostructure, in which Ru particles were imbedded. The new carbon materials were further evaluated in the selective hydrogenation of cinnamaldehyde (CMA). By comparison with the traditional Ru/AC catalyst, our Ru-OMC samples exhibited much higher activity (2–14-fold) and up to 60% of selectivity to cinnamyl alcohol (CMO). [ABSTRACT FROM AUTHOR]

A series of SiO2 supported transition metal (Fe, Co, Ni, Mo and W) phosphide catalysts were synthesized and tested for the selective hydrogenation of cinnamaldehyde (CMA). Among these tested catalysts, Ni12P5/SiO2 and Ni2P/SiO2 prepared with initial Ni/P ratios of 2/1.3 and 1/1 exhibited high activity and selectivity for the conversion of CMA to hydrocinnamaldehyde (HCMA). The two nickel phosphide catalysts showed selectivity to HCMA up to 90% at a conversion of 90%. The properties of the nickel phosphide catalysts were characterized by BET surface area determinations, X-ray powder diffraction (XRD) analysis, and transmission electron microscopy (TEM). The influences of reaction temperature, hydrogen pressure, Ni/P ratio, and reduction temperature were studied in detail. For comparison, Pd/SiO2 catalyst was also used in this reaction, and the possible reasons for the different catalytic performances of the two kinds of catalysts are presented. [ABSTRACT FROM AUTHOR]

Hydrogenation of unsaturated carbonyl compounds like cinnamaldehyde and citral was studied in a biphasic media using water-soluble FeII/EDTA as a catalyst. It was observed that olefinic bond was selectively hydrogenated over the carbonyl group. Different reaction parameters like temperature, pressure, catalyst concentration were optimized for better selectivity of hydrocinnamaldehyde/dihydrocitronellal. The catalyst was further extended to hydrogenation of several other α,β-unsaturated carbonyl compounds. [ABSTRACT FROM AUTHOR]

Hydrogenation properties of cinnamaldehyde (CMA) have been studied over Pt/ZrO2 and PtM/ZrO2 catalysts (M = Cr, Mn, Fe, Co and Ni) in ethanol at 343 K and 2.0 MPa. The effect of different content of Ni and base has also been investigated over PtNi/ZrO2 catalyst. With introduction of transition metals to Pt/ZrO2 catalyst shows a significant influence on the catalytic properties. PtCo/ZrO2 catalysts show the best yield of cinnamyl alcohol (CMO), and PtNi/ZrO2 catalyst shows good yield of hydrocinnamaldehyde (HCMA). In the presence of base solution, rate of the hydrogenation of CMA over PtNi/ZrO2(0.4 wt%) catalyst increases significantly and side reaction is remarkably inhibited. More bare metal atoms situated remote from the interface region on PtNi/ZrO2 catalyst surface are the reason of good selectivity of HCMA for PtNi/ZrO2 catalyst. [ABSTRACT FROM AUTHOR]

The behaviour of ruthenium was studied in relation to the acidity of beta zeolite. The impregnation of beta zeolite with ruthenium chloride decreased the crystallite size of beta zeolite. The acidity of the beta zeolite influenced the particle size of ruthenium. The particle size of ruthenium increased with decreasing acidity. Even catalysts with large particle size of ruthenium were selective to hydrogenation of the C=C bond in cinnamaldehyde hydrogenation. The ruthenium catalyst with highest Brönsted acidity gave the highest conversion. The products formed were hydrocinnamaldehyde, cinnamaldehyde acetal and hydrocinnamaldehyde acetal; no cinnamyl alcohol was observed, which indicates protection of the C=O group during the hydrogenation via acetal formation. [ABSTRACT FROM AUTHOR]