Bond In Cinnamaldehyde Research Articles

Immobilized PVA-stabilized gold nanoparticles on silica show an unusual selectivity in the hydrogenation of cinnamaldehyde

This work reports for the first time an “unusual” property of immobilized PVA-stabilized gold nanoparticles (AuNPs) on SiO2 for highly selective hydrogenation at the CC bond of cinnamaldehyde (CAL) at 150–180 °C, uncovering a catalytic route for selective hydrocinnamaldehyde (HCAL) production from CAL. When the same colloidal gold nanoparticles are immobilized on ZrO2, they effect competitive hydrogenations at both CC and CO bonds of the CAL molecules under identical reaction conditions.

Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with carbon nanotubes supported Pt-Co catalysts

The Pt-Co catalysts supported on carbon nanotubes (CNTs) have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding cinnamyl alcohol (CMO) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.17 wt%Co/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 60 °C under a pressure of around 2.5 MPa, and 92.4% for the conversion of CMA and 93.6% for the selectivity of CMA to CMO, respectively. The selective hydrogenation for the C O double bond in CMA would be improved as increasing the H 2 pressure, and the selective hydrogenation for the C C double bond in CMA is enhanced as increasing the reaction temperature. In addition, these catalysts have also been characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), H 2-temperature programmed reduction (H 2-TPR) and H 2-temperature programmed desorption (H 2-TPD) techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Co would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt 0 onto CNTs and increase the catalytic activity and selectivity of CMA to CMO.

Utilization of clay minerals for developing Pt nanoparticles and their catalytic activity in the selective hydrogenation of cinnamaldehyde

Abstract Platinum sub colloids (nm range) were synthesized in the presence of a surfactant (CTAB) by micellar technique in which the metal particles ensured long-term stability in the aqueous dispersion and were prevented from agglomeration. When this surfactant stabilized Pt hydrosol was allowed to react with aqueous suspension of Na + montmorillonite or Li + hectorite, the cationic exchange reaction between Na + /Li + and organic cation (CTA + ) took place with simultaneous incorporation of the reduced Pt particles into the organoclay host. Finely divided and well-dispersed Pt particles (nm range) were generated by this method in the interlamellar space of the montmorillonite and hectorite. The catalyst samples with different metal loadings were synthesized and characterized with UV–Vis spectroscopy, XRD, TEM and AAS techniques. From the TEM micrographs it was confirmed that the diameter of the Pt particles intercalated was in the nanometer range. The catalytic activity of the synthesized catalysts was studied towards the selective hydrogenation of C O bond in cinnamaldehyde using a batch type high pressure reactor at different temperatures and hydrogen pressures. The catalytic activity of the catalysts and their selectivity towards cinnamyl alcohol were discussed in detail. The activity and selectivity of 1 wt.% Pt loaded montmorillonite catalyst was found to be appreciable.

Carbon nanotubes supported Pt–Ni catalysts and their properties for the liquid phase hydrogenation of cinnamaldehyde to hydrocinnamaldehyde

The Pt–Ni catalysts supported on CNTs have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding hydrocinnamaldehyde (HCMA) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt–0.34 wt% Ni/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 70 °C under a pressure of around 2.0 MPa, and 98.6% for the conversion of CMA and 88.2% for the selectivity of CMA to HCMA, respectively. The selective hydrogenation for the C C bond in CMA would be improved as increasing the reaction temperature, and the hydrogenation for the C O bond in CMA is enhanced as increasing the H 2 pressure. In addition, these catalysts have also been characterized using TEM-EDS, XPS, H 2-TPR and H 2-TPD techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Ni would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt 0 onto CNTs and increase the catalytic activity and selectivity of CMA to HCMA.

A simple method for preparing highly active palladium catalysts loaded on various carbon supports for liquid-phase oxidation and hydrogenation reactions

Preparation of nanosized palladium (Pd) catalysts supported on various carbon supports using a simple liquid-phase reduction of aqueous Pd complexes with potassium borohydride (KBH 4) was investigated. We found that addition of appropriate amounts of sodium hydroxide (NaOH) into aqueous solutions of sodium tetrachloropalladate (Na 2PdCl 4) followed by reduction with KBH 4 produced highly dispersed Pd nanoparticles less than 5 nm in diameter on any carbon supports. Ultraviolet–visible light (UV–vis) absorption spectra of aqueous Na 2PdCl 4 solutions in the presence of various amounts of NaOH clarified the occurrence of partial or complete ligand exchange of the Pd complex from chloride ions (Cl −) to hydroxide ions (OH −). Hence, the production of small Pd nanoparticles on carbon supports is likely to be induced by structural change in the precursor complex prior to the reduction with KBH 4. Moreover, evaluation of catalytic activities for liquid-phase oxidation of benzyl alcohol into benzaldehyde using oxygen and hydrogenation of the C C bond in cinnamaldehyde with hydrogen revealed that catalytic functions were significantly dependent on the size and the dispersion of Pd particles; i.e., both reactions proceeded efficiently on small Pd catalysts highly dispersed on carbon supports but did not occur efficiently on Pd particles of relatively large sizes or with poor dispersion on those supports.

Effect of crystallinity on the catalytic performance of amorphous Co–B particles prepared from cobalt nitrate and potassium borohydride in the cinnamaldehyde hydrogenation

The amorphous Co–B particles were prepared from cobalt nitrate and potassium borohydride. Ethanol-thermal treatment has been used to promote the crystallinity of Co–B particles. Both the amorphous and crystallized Co–B particles were characterized by X-ray powder diffraction (XRD), scanning electron micrograph (SEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), specific surface area ( S BET), CO temperature-programmed desorption (TPD), and magnetic performance test. After crystallization, the synergistic effect between Co and B, the structure stability, and the magnetic property of Co–B enhanced while the activation energy in cinnamaldehyde (CMA) hydrogenation decreased. Furthermore, the conversion of cinnamaldehyde (CMA) increased from 5% to 57%. The hydrogenation of the C C bond in cinnamaldehyde (CMA) is favored for the amorphous Co–B particles while the hydrogenation of the C O bond is preferred for the crystallized Co–B particles. After 13 cycles, the crystallized Co–B particles remain higher cinnamaldehyde (CMA) conversion and cinnamyl alcohol (CMO) selectivity, which is attributed to their good structure stability and the novel magnetic method for recycle; while the cycle performance of amorphous Co–B particles is poor due to their instable structure.

Steric effects in the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol using an Ir/C catalyst

The liquid phase selective hydrogenation of cinnamaldehyde to cinnamyl alcohol has been carried out over a graphite-supported iridium catalyst. The effect of reaction parameters such as temperature, pressure, concentration of reactant, the effect of addition of product to the feed and pre-reduction of the catalyst were studied. In situ pre-reduction of the catalyst with hydrogen had a very significant enhancing effect on the conversion of cinnamaldehyde and selectivity of the catalyst to cinnamyl alcohol. Kinetic analysis of the pre-reduced catalyst showed that the reaction is zero order with respect to cinnamaldehyde and first order with respect to hydrogen. The reaction follows an Arrhenius behaviour with an activation energy of 37 kJ mol −1. Detailed analysis of the reaction showed that hydrogenation of the CC double bond to give hydrocinnamaldehyde predominantly occurred at low conversions of cinnamaldehyde (<5%). In addition, it was found that the CC double bond in cinnamyl alcohol could not be hydrogenated to give phenyl propanol, whereas the less thermodynamically favoured hydrogenation of the CO bond in hydrocinnamaldehyde could readily proceed. It was also found that the addition of cinnamyl alcohol to the feed greatly decreased the rate of hydrogenation of the CC bond in cinnamaldehyde. These results indicated that the cinnamyl alcohol adsorbs on the surface of the catalyst during the reaction and creates a steric effect that inhibits the hydrogenation of the CC bond of cinnamaldehyde.

Supported liquid-phase catalysts containing ruthenium complexes for selective hydrogenation of α, β-unsaturated aldehyde: importance of interfaces between liquid film, solvent, and support for the control of product selectivity

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) has been investigated with supported liquid-phase catalysts (SLPC), which contain Ru–TPPTS complexes in water film supported on a porous silica gel, in organic solvent (toluene). It was shown that COL can be mainly produced with small quantities of hydrocinnamaldehyde (HCAL) and hydrocinnamyl alcohol (HCOL). The influence of various reaction and catalyst preparation parameters on the overall rate of reaction and the product selectivity have been examined. In addition, liquid-phase adsorption of CAL on water-loaded silica samples has also been measured. It is believed that the hydrogenation of CAL to COL occurs at the interface between the water film and the organic solvent while that to HCAL at the interface between silica, water, and toluene. The hydrophilic nature of the CO bond of CAL is significant for the selective formation of COL at the water/toluene interface, to which polar CO bonds of CAL molecules are pointing. The product, COL, also has a polar OH group, and so it is difficult for COL to be hydrogenated to HCOL at this interface. At the other silica/water/toluene interface, CAL molecules may be adsorbed with their CC bonds as well, which enables the hydrogenation to HCAL. On recycling of SLPC, its activity and COL selectivity decrease. Both oxygen dissolved in toluene and change of active Ru complexes in the water film are responsible for the decrease of catalytic activity, and the change of the state of dispersion of the water film is significant for the decrease of COL selectivity.

Carbon nanofiber supported palladium catalyst for liquid-phase reactions: An active and selective catalyst for hydrogenation of cinnamaldehyde into hydrocinnamaldehyde

Carbon nanofibers (CNFs) prepared by decomposition of ethane over a Ni/alumina catalyst, are used as support for palladium clusters. The carbon support displays a mean diameter of 40–50nm, lengths up to several tens of micrometers, as highlighted by transmission electron microscopy (TEM) observations and a specific surface area of about 50m2/g. The spheroidal palladium particles have a relatively homogeneous and sharp size distribution, centered at around 4nm. This novel Pd/carbon nanofiber catalyst displays unusual catalytic properties and is successfully used in the selective hydrogenation of the CC bond in cinnamaldehyde at a reaction temperature of around 80°C, under continuous hydrogen flowing at atmospheric pressure. The high performances of this novel catalyst in terms of efficiency and selectivity are, respectively, related to the inhibition of the mass-transfer processes over this non-porous material and to peculiar palladium–carbon interactions. It is concluded that the absence of microporosity in the carbon nanofibers favours both the high activity and selectivity which is confirmed by comparison with the commercially available high surface area charcoal supported palladium catalyst.

Water-soluble iridium and rhodium complexes with tris(hydroxymethyl)phosphine and their catalysis in biphasic hydrogenation and hydroformylation

Novel water-soluble Ir and Rh complexes with tris(hydroxymethyl)phosphine catalyse the selective hydrogenation of the CO bond of cinnamaldehyde and the hydroformylation of pent-1-ene both under biphasic conditions.

Hydrogenation of crotonaldehyde and cinnamaldehyde catalyzed by water-soluble palladium complex

The selective hydrogenations of crotonaldehyde and cinnamaldehyde in the aqueous-benzene biphasic system were investigated using water-soluble palladium complex PdCl 2(TPPTS) 2 as catalyst. The hydrogenation rate of crotonaldehyde was higher than that of cinnamaldehyde under similar reaction conditions. The palladium complex selectively catalyzed the hydrogenation of CC bond in crotonaldehyde to form butanal (100%). On the contrary, hydrogenation of both CC and CO bonds in cinnamaldehyde occurred simultaneously, with the amount of phenylpropanal only slightly higher than that of phenylpropanol. However, the reduction of CO bond of cinnamaldehyde could be inhibited by the addition of Na 2CO 3 solution. Therefore, high selectivity to form phenylpropanal (91%) could be obtained by using Na 2CO 3 solution at pH 12.2. Other factors affecting the hydrogenation conversion and selectivity of crotonaldehyde and cinnamaldehyde were also discussed.