Cinnamyl Alcohol Selectivity Research Articles

Chemoselective reduction of α,β-unsaturated carbonyl compounds with UiO-66 materials

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 10wt% Ag/UiO-66 catalyst reached complete conversion after 6h and 50bar 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 24h 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 Nanoclusters Confined within Metal–Organic Framework Cavities for Chemoselective Cinnamaldehyde Hydrogenation

A highly selective and robust catalyst based on Pt nanoclusters (NCs) confined inside the cavities of an amino-functionalized Zr-terephthalate metal–organic framework (MOF), UiO-66-NH2 was developed. The Pt NCs are monodisperse and confined in the cavities of UiO-66-NH2 even at 10.7 wt % Pt loading. This confinement was further confirmed by comparing the catalytic performance of Pt NCs confined inside and supported on the external surface of the MOF in the hydrogenation of ethylene, 1-hexene, and 1,3-cyclooctadiene. The benefit of confining Pt NCs inside UiO-66-NH2 was also demonstrated by evaluating their performance in the chemoselective hydrogenation of cinnamaldehyde. We found that both high selectivity to cinnamyl alcohol and high conversion of cinnamaldehyde can be achieved using the MOF-confined Pt nanocluster catalyst, while we could not achieve high cinnamyl alcohol selectivity on Pt NCs supported on the external surface of the MOF. The catalyst can be recycled ten times without any loss in its a...

Selective Hydrogenation of Cinnamaldehyde over Pt and Pd Supported on Multiwalled Carbon Nanotubes in a CO2-Expanded Alcoholic Medium

Pt/MWCNT and Pd/MWCNT nanocatalysts were prepared via a liquid reduction method. The selective hydrogenation of cinnamaldehyde (CAL) was investigated over 5.0 wt.% Pt/MWCNT and 5.0 wt.% Pd/MWCNT catalysts in a CO2-expanded alcoholic medium at different reaction conditions. The hydrogenation selectivities over these two catalyst types were shown to be entirely different. It was found that the Pt/MWCNT catalysts are highly selective for C═O bonds, giving the unsaturated alcohol a selectivity for cinnamyl alcohol (COL) of 97.3% and a conversion rate for cinnamaldehyde of 99.3%. Conversely, the Pd/MWCNT catalyst is highly selective for C═C bonds, producing a saturated aldehyde with a selectivity for hydrocinnamaldehyde (HCAL) of 91.3% and a conversion rate for cinnamaldehyde of 98.6%. The small diameter of the Pt or Pd granules over the multiwalled carbon nanotubes (MWCNTs) leads to a high catalyst activity, and an increase of CO2 pressure results in a better hydrogenation performance for C═O bonds than that for C═C bonds.

Effects of Promoters on Properties of Cu-Zn-Al Catalyst for Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Cu-Zn-Al catalyst was modified by the additives such as Ni and Mn, and the prepared catalyst was employed in the selective catalytic hydrogenation of cinnamaldehyde. The results showed that the addition of Ni could improve catalytic activity significantly, moreover, the improving effect was highest when Zn was replaced by Ni, simultaneously leading to excessive hydrogenation. The Cu-(5%)Mn-Zn-Al catalyst exhibited a higher selectivity of 93.6% for C = O bond to cinnamyl alcohol and hydrogenation activity of 33.0% conversion at 130°C under 1.0 MPa of H2 pressure with the reaction time of 1 h. TPR and XRD characterization showed that Mn promoter was favorable for the growth of Cu0 fine grains on the surface of catalyst, which not only led to steric effect which improved the selectivity for cinnamyl alcohol, but also reduced the numbers of active centers, consequently decreased the reaction rate.

Intramolecular selective hydrogenation of cinnamaldehyde over CeO2–ZrO2-supported Pt catalysts

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.

Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol by Biocatalysis

A strain CG08 was isolated which could selectively hydrogenate cinnamaldehyde to cinnamyl alcohol. The strain was idetified asCitrobacter freundii. The yield of cinnamyl alcohol was determined by UV spectroscopy. The optimized degradation conditions were found as 30 g/L glucose,16 g/L peptone with the initial cinnamaldehyde addition amount of 2 mL/L at pH 6.0, 30 °C for 40 hours of reaction. The secondary addition amount was 1 mL/L for 32 hours. Under the optimized conditions, the conversion of cinnamaldehyde was 100 %, the selectivity for cinnamyl alcohol was 90.1 %. And the yield of cinnamyl alcohol was up to 2.88 g/L, which was 26.3 % higher than the previously reported one.

Effect of heteroatom substituted mesoporous support on the selective hydrogenation of cinnamaldehyde in supercritical carbon dioxide

Selective hydrogenation of cinnamaldehyde (CAL) is being carried out in supercritical carbon dioxide over Pt nanoparticle, supported on Al-MCM-48 and Ti-MCM-48. To evaluate the influence of the support, results are compared with Pt-MCM-48 (Si only). Pt-Al-MCM-48 and Pt-Ti-MCM-48, (containing metal particles of similar sizes) exhibits remarkable selectivity for cinnamyl alcohol (COL). A strong influence of heteroatom (Al and Ti) substitution is found in the activity and selectivity of the reaction. The rate of formation of COL follows the order of Pt-Ti-MCM-48 > Pt-Al-MCM-48 > Pt-MCM-48 under the same reaction conditions. We therefore propose that due to the interaction of Ti with CO 2, the support becomes activated, which increases the electron density of Pt and thereby interacts preferentially with the C O bond. Depending on the nature of the heteroatom, a significant change in the CO 2 pressure dependent activity and selectivity is observed. For Pt-Al-MCM-48, the maximum selectivity for COL is observed in the higher pressure (single phase) region. On the contrary, as the interaction of Ti and CO 2 is favorable in the lower pressure region, Pt-Ti-MCM-48 shows highest selectivity for COL at 7–8.5 MPa (biphasic region) and decreases in the single phase region. Conventional Arrhenius behavior is maintained for Pt-Al-MCM-48, whereas Pt-Ti-MCM-48 displays significant decrease in the reaction rate with increasing temperature.

Preparation and characterization of amorphous Co-B catalysts with mesoporous structure

Amorphous Co-B alloy catalyst with mesoporous structure was firstly prepared via reduction of cobalt acetate by potassium borohydride in the presence of an organic template hexadecyl–trimethyl–ammonium bromide. The as-prepared mesoporous Co-B was characterized by Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), scanning electron micrograph (SEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) measurement, N 2 adsorption–desorption, CO temperature-programmed desorption (TPD), and magnetic performance test. Investigations demonstrated that such mesoporous structure has a pronounced influence on the magnetic properties of Co-B alloy and the enhanced magnetic performance enables the as-prepared mesoporous Co-B to be recycled by magnetic method in the liquid-phase cinnamaldehyde (CMA) hydrogenation. During the hydrogenation, the as-prepared mesoporous Co-B exhibited higher cinnamaldehyde conversion and cinnamyl alcohol (CMO) selectivity than the regular Co-B obtained without using organic template, which is attributed to the larger specific surface area and the stronger affinity to C O. After 11 cycles, the conversion of cinnamaldehyde over the mesoporous Co-B was 85.2%, which is higher than that of the fresh regular Co-B. The good cycle performance is attributed to its preserved mesoporous structure in spite of the collapse of some mesopores during cycling. In addition, the increase of selectivity for cinnamyl alcohol after several cycles is attributed to the growth of particle size.

Effect of transition metals (Cr, Mn, Fe, Co, Ni and Cu) on selective hydrogenation of cinnamaldehyde over Pt/CNTs catalyst

The effect of transition metals (Cr, Mn, Fe, Co, Ni and Cu) on the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding semi-hydrogenated product over Pt/CNTs catalyst has been studied in ethanol at 343 K under 2.0 MPa H2 pressure. PtNi/CNTs catalyst shows good catalytic activity and selectivity of C=C bond hydrogenation, 68.4% for conversion of CMA and 97.0% for selectivity of hydrocinnamaldehyde (HCMA). PtCo/CNTs catalyst shows good catalytic activity and selectivity of C=O bond hydrogenation, 91.3% for conversion of CMA and 88.2% for selectivity of cinnamylalcohol (CMO).

Recyclability of water-soluble ruthenium–phosphine complex catalysts in multiphase selective hydrogenation of cinnamaldehyde using toluene and pressurized carbon dioxide

The recyclability of water-soluble ruthenium–phosphine complex catalysts was investigated in water–toluene and in water–pressurized carbon dioxide systems for selective hydrogenation of trans-cinnamaldehyde (CAL). For the first hydrogenation run, the selectivity for cinnamyl alcohol (COL) is high for both toluene and dense CO 2, because of interfacial catalysis in which the reaction mainly occurs at the interface between the aqueous phase and the other toluene or dense CO 2 phase. The total CAL conversion and the COL selectivity decrease on the second run, more significantly with dense CO 2 than toluene. On the subsequent runs, however, less significant changes were observed. During the first run, the active metal complexes should change to much less active ones such as Ru(H) 2L n (TPPTS) m (L = COL) by accumulation of the main product of COL. This structural change may occur more easily in multiphase hydrogenation with dense CO 2 than that with toluene, probably because the solubility in the dense CO 2 gas phase is even smaller than that in toluene. For homogeneous reaction of COL in aqueous phase, Ru(H) 2L n (TPPTS) m catalyzes the isomerization to HCAL compared with the hydrogenation to hydrocinnamyl alcohol. With those complexes, however, the selectivity for COL is still comparable to that for HCAL for multiphase hydrogenation reactions because the hydrogenation of an ampholytic substrate of CAL occurs mainly at interface between water and toluene or dense CO 2 gas phase. Interactions of CO 2 molecules with CAL would also increase the reactivity of carbonyl group of the substrate.

Selective hydrogenation of cinnamaldehyde using ruthenium–phosphine complex catalysts with multiphase reaction systems in and under pressurized carbon dioxide: Significance of pressurization and interfaces for the control of selectivity

The selective hydrogenation of trans-cinnamaldehyde (CAL) has been investigated with several types of multiphase reaction systems using Ru–phosphine complex catalysts in the presence of high-pressure CO 2. The selective formation of an unsaturated alcohol, cinnamyl alcohol (COL), can be achieved in an organic solvent free two-phase system, which includes the liquid (CAL, Ru complex) and gas (H 2, CO 2) phases. Both total conversion and COL selectivity are enhanced with increasing CO 2 pressure. This enhancement is due to the dissolution of CO 2 molecules into the CAL phase, which promotes the dissolution of H 2 and activates the reactivity of the carbonyl group of CAL molecules, and a high concentration of CAL in the reaction medium. The high COL selectivity can also be obtained in three- and two-phase reaction systems, which include a gas (H 2, CO 2) phase, a liquid (water-dissolving Ru complex) phase, and/or another liquid phase (CAL). The COL selectivity is high irrespective of CO 2 pressure because of a water–CAL interface or a water–CO 2 interface as a main reaction locus, but the total conversion is not enhanced by pressurization with CO 2, and it decreases at elevated CO 2 pressure under the two-phase conditions because of a simple dilution effect. In contrast, the highly selective formation of COL is not possible in a homogeneous dense CO 2 gas phase or in a two-phase system that includes a gas (H 2) phase and a liquid (DMF, CAL, Ru complex) phase. Pressurization with CO 2 is not effective in improving the conversion and COL selectivity for these systems.

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.

Influence of oxygen-containing surface groups on the activity and selectivity of carbon nanofiber-supported ruthenium catalysts in the hydrogenation of cinnamaldehyde

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.

Completely selective hydrogenation of trans-cinnamaldehyde to cinnamyl alcohol promoted by a Ru–Pt bimetallic catalyst supported on MCM-48 in supercritical carbon dioxide

Supercritical carbon dioxide (scCO2) is a unique reaction medium for the selective hydrogenation of cinnamaldehyde using a well-defined Ru–Pt bimetallic catalyst supported on MCM-48. The reaction is completely selective to the unsaturated alcohol in supercritical carbon dioxide. The selectivity to the desired unsaturated alcohol shows a significant pressure dependence. By varying the pressure at the constant reaction temperature of 323 K, we are able to optimize the selectivity of cinnamyl alcohol to 100%. This is a particularly dramatic enhancement compared to that in organic solvents and under solventless conditions, where Ru–Pt bimetallic catalyst produces cinnamyl alcohol along with hydrocinnamaldehyde and 3-phenylpropanol. More importantly, the excellent physicochemical properties of the scCO2 medium provide a significant influence on the selectivity, which goes beyond that of simple solvent replacement only.

Highly Efficient Hydrogenation of Cinnamaldehyde Catalyzed by Pt-MCM-48 in Supercritical Carbon Dioxide

In supercritical carbon dioxide medium, a platinum-containing cubic mesoporous molecular sieve was shown to promote markedly the selective hydrogenation of trans-cinnamaldehyde, giving an excellent selectivity for cinnamyl alcohol. In contrast to the other platinum-containing conventional catalysts, Pt-MCM-48 can be recycled a number of times without showing any deactivation in the studied reaction condition. The selectivity mainly depends on the pressure of carbon dioxide, while the conversion depends on the pressure of carbon dioxide as well as hydrogen pressure.

Selective hydrogenation of α-, β-unsaturated aldehyde to unsaturated alcohol with supported platinum catalysts at high pressures of hydrogen

Hydrogenation of an α, β-unsaturated aldehyde, cinnamaldehyde (CAL), was carried out with silica-supported platinum catalysts in ethanol under pressurized hydrogen atmosphere up to 12 MPa at 50°C. The initial rate of reaction (CAL consumption) was proportional to hydrogen pressure and independent of CAL concentration. Increasing hydrogen pressure decreased the selectivity of cinnamyl alcohol (COL) but increased that of hydrocinnamaldehyde (HCAL). The COL selectivity increased with CAL concentration. The effect of hydrogen pressure on the selectivity in ethanol is different from that observed previously in a solvent of supercritical carbon dioxide.

Ultrasonics in chemoselective heterogeneous metal catalysis. Sonochemical hydrogenation of unsaturated carbonyl compounds over platinum catalysts

The hydrogenation of unsaturated aldehydes was studied over ultrasonically pretreated silica supported platinum catalyst. In the hydrogenation of cinnamaldehyde a remarkable reaction rate and cinnamyl alcohol selectivity increase was observed. Using other unsaturated aldehydes the reaction rate and unsaturated alcohol selectivity increased moderately.

Selective hydrogenation of cinnamaldehyde over Raney cobalt catalysts modified with salts of heteropolyacids

The hydrogenation of cinnamaldehyde to cinnamyl alcohol was carried out over Raney cobalt catalysts modified by Cu 3/2PMo 12O 40. It was found that the conversion of cinnamaldehyde decreases substantially with increases in the amount of Cu 3/2PMo 12O 40 deposited on Raney cobalt catalysts. The maximum yield of cinnamyl alcohol varies with the amount of deposited Cu 3/2PMo 12O 40. The more the deposited modifier, the higher the attainable maximum yield of cinnamyl alcohol. With 2.8% Cu 3/2PMo 12O 40 modified Raney cobalt, the selectivity for cinnamyl alcohol does not change with reaction temperature and reaction time. Thus, it is likely that the selectivity of ca. 80% for cinnamyl alcohol represents a specific value which is related to the nature of the surface modifier, Cu 3/2PMo 12O 40. The influences of the heteropolyanions and the competitive cations on the conversion and the selectivity were also investigated. It was found that copper salts of different heteropolyacids acting as the modifier of the catalyst bring about different enhancements in the selectivity for cinnamyl alcohol. The order of enhancement of selectivity in terms of heteropolyacid anion is PMo 12O 3− 40>SiMo 12O 4− 40>PW 12O 3− 40. There is little difference in selectivity by modification with (NH 4) 6Mo 7O 24 and Cu 2SiMo 12O 40. Raney cobalt catalyst modified by different 12-molybdophosphate containing cations of alkali, alkaline earth and transition metals gives a similar selectivity of about 75%. Among all of the 12-molybdophosphates, that containing the cation Cu 2+ is the best in improving the selectivity of the catalysts. A selectivity as high as 83% was attained when an amount of 2.8% Cu 3/2PMo 12O 40 was deposited on the catalyst.