Cinnamyl Alcohol Selectivity Research Articles

Co-Ti Bimetallic Complex-Induced Phase Modulation of Co@Black TiO2 for Catalytic Hydrogenation of Cinnamaldehyde.

Transition-metal-doped black titania, primarily in the anatase phase, shows promise for redox reactions, water splitting, hydrogen generation, and organic pollutant removal, but exploring other titania phases for broader catalytic applications is underexplored. This study introduces a synthetic approach using a Co-Ti bimetallic complex bridged by a 1,10-phenanthroline-5,6-dione ligand as a precursor for the synthesis of cobalt-doped black titania [Co@L2N@b-TiO2]. The synthesis involves precise control of pyrolysis conditions, yielding a distinct structure dominated by the rutile phase over anatase, with active cobalt encapsulated within a nitrogen-doped graphitic layer, primarily as Co0 rather than CoII and CoIII. The synthesized material is employed for the selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) under industrially viable conditions. The efficiency and selectivity of Co@L2N@b-TiO2 was compared with other catalysts, including cobalt-doped rutile TiO2 (Co@r-TiO2), anatase TiO2 (Co@a-TiO2), and black titania (Co@b-TiO2) as well as materials pyrolyzed under different atmospheres and temperatures, materials with phenanthroline ligands, and materials lacking any ligands. The superior performance of Co@L2N@b-TiO2 is attributed to its high surface area, stable Co0 within the nitrogen-doped graphitic layer, and composition of rutile and anatase phases of TiO2 and Ti2O3 (referred to as RAT), along with the synergistic interaction between RAT and Co0. These factors significantly influence the efficiency and selectivity of COL over hydrocinnamaldehyde (HCAL) and hydrocinnamyl alcohol (HCOL), indicating potential for broader applications beyond catalysis, particularly in designing of black titania-based materials.

Design of Pt@Sn core–shell nanocatalysts for highly selective hydrogenation of cinnamaldehyde to prepare cinnamyl alcohol

The selective hydrogenation of cinnamaldehyde (CAL) to prepare cinnamyl alcohol (COL) is challenging as the unwanted hydrogenation of CC bond in CAL is thermodynamically more favorable than the hydrogenation of CO bond. We herein designed core–shell structured nanoparticles (NPs) that consisted of Pt cores and Sn shells to catalyze the CAL to COL conversion. By simply changing the amount of Sn precursor, we generated Pt@Sn NPs with different Sn shell thickness and catalytic performance. Among the samples, Pt@Sn/SiO2 with Pt/Sn of 1/1 achieved the highest CAL conversion (87.2 %) as well as the COL selectivity (95.4 %), which were 5-fold and 6-fold, respectively, higher than those of Pt/SiO2. This catalyst was also applicable to the hydrogenation of other α, β-unsaturated aldehyde and unsaturated carbonyl compounds. Both experiments and theoretical calculations indicated that the strong Pt-Sn interaction and the partial coverage of Pt by Sn facilitated their adsorption of CO bonds, thus enhancing the conversion of CAL and the selectivity towards COL.

Enhanced Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol over Silica-Coated Pt-CoxOy Hybrid Nanoparticles.

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) is difficult due to the intrinsic difficulty with thermodynamically easier hydrogenation of C═C bonds. In this work, Pt-CoxOy hybrid nanoparticles encapsulated in mesoporous silica nanospheres (Pt-CoxOy@mSiO2) were synthesized by a sol-gel method, which showed greatly improved COL selectivity for hydrogenation of CAL. At 80 °C and 1.0 MPa of H2, Pt-CoxOy@mSiO2 achieved a CAL conversion of 98.7% with a COL selectivity of 93.5%. In contrast, Pt@mSiO2 yields 3-phenylpropanol (HCOL) as the major product with HCOL selectivity of 67.2%, while PtCo@mSiO2 yields 3-phenylpropionaldehyde with selectivity of 51.8% under the same conditions. The enhanced catalytic performance of Pt-CoxOy@mSiO2 for hydrogenation of CAL to COL is ascribed to the Pt surface electron deficiency induced by metal-oxide interaction, and the protection of active NPs by silica shells results in good catalytic stability.

Aqueous phase selective C[dbnd]O hydrogenation of cinnamaldehyde over bimetallic RuCo catalysts with electronic and geometric modification

Aqueous phase selective hydrogenation of cinnamaldehyde (CALD), as a representative α,β-unsaturated aldehyde, into cinnamyl alcohol (CALA) has been investigated over monometallic Ru and bimetallic RuCo catalysts on pristine h-BN support. Using water as the solvent, the optimal 0.5%Ru-1.1%Co/h-BN catalyst exhibits 510 h−1 specific reaction rate and 78.9 % CALA selectivity as well as good recycling stability at 100 °C. Based on the structure characterizations of catalysts, metal nanoparticles consisting of metallic Ru0 and partially oxidized Ruδ+ sites are uniformly dispersed on h-BN thin sheets. In comparison to monometallic catalysts, additive Co metals in bimetallic RuCo/h-BN catalysts play significant geometric and electronic modification roles on Ru active sites depending on the Ru/Co ratio, and therefore remarkably enhances the preferential activation of CALD CO bond and selectivity of CALA product as well as accelerates the catalytic reaction. Furthermore, the hydrogen dissociative activation ability of various Ru and RuCo catalysts was evaluated, while the superior catalytic performance in water than other commonly used solvents was also clarified and discussed.

ZIF-8 decorated Au/Al2O3 hybrid material for highly selective hydrogenation of cinnamaldehyde

Recycling of supported Au catalysts is challenging because of aggregation or loss of Au. Here, we report a strategy for introducing ZIF-8 into traditional Au/Al2O3 surface. The introduction of ZIF-8 can not only provide higher selectivity for the reaction products, but also prevent the loss or aggregation of the Au catalyst. From a series of characterizations, it can be seen that the ZIF-8 decorated Au/Al2O3 hybrid material Au@ZA (Z refers to ZIF-8, A refers to Al2O3) was successfully prepared. Au nanoparticles have better dispersion on the composite carrier, and the particle size is smaller. In the hydrogenation reaction of cinnamaldehyde (CAL), the Au@ZA composite catalyst has both the high chemical stability and the high selectivity of cinnamyl alcohol (COL) due to the micropore size effect of ZIF-8. The Au@ZA catalyst has ∼ 85 % COL selectivity when the CAL conversion is close to 100 %. And after 8 times of repeated use, the conversion of CAL and the selectivity of COL did not decrease significantly. It should be noted that just when a small amount of ZIF-8 is present, the synergistic catalytic effect mentioned above can be produced.

Reactant enrichment in hollow void of Pt NPs@MnOx nanoreactors for boosting hydrogenation performance.

In confined mesoscopic spaces, the unraveling of a catalytic mechanism with complex mass transfer and adsorption processes such as reactant enrichment is a great challenge. In this study, a hollow nanoarchitecture of MnOx-encapsulated Pt nanoparticles was designed as a nanoreactor to investigate the reactant enrichment in a mesoscopic hollow void. By employing advanced characterization techniques, we found that the reactant-enrichment behavior is derived from directional diffusion of the reactant driven through the local concentration gradient and this increased the amount of reactant. Combining experimental results with density functional theory calculations, the superior cinnamyl alcohol (COL) selectivity originates from the selective adsorption of cinnamaldehyde (CAL) and the rapid formation and desorption of COL in the MnOx shell. The superb performance of 95% CAL conversion and 95% COL selectivity is obtained at only 0.5MPa H2 and 40min. Our findings showcase that a rationally designed nanoreactor could boost catalytic performance in chemoselective hydrogenation, which can be of great aid and potential in various application scenarios.

Two-dimensional ruthenium nanoparticles between graphite layers: The effect of reduction temperature

A mixture of graphite powder and ruthenium chloride (III) anhydrous was treated at 723 K under 0.3 MPa chlorine for 3 days, followed by reduction under 40 kPa of hydrogen for 1 h to produce ruthenium metal particles intercalated between graphite layers (Ru-GIC). The structures of ruthenium particles depended on the reduction temperatures. Sheet-like ruthenium particles with 1–3 nm thickness and 10 to several hundred nm width containing numerous irregularly shaped holes with round edge, were formed by reduction at 573 K. A Ru-GIC sample treated at 653 K possessed two-dimensional ruthenium nanosheets with hexagonal holes (straight lines intersect at an angle of 120°) in a similar range of thickness and width. On the other hand, Ru-GIC samples reduced at 773 and 823 K showed two-dimensional plate morphology with a thickness of 1–4 nm. In addition, ruthenium nanoparticles supported on the graphite surface (Ru/Gmix) were also prepared from a slurry of ruthenium chloride (III) hydrate and graphite powder by impregnation and hydrogen reduction. The ruthenium particles in Ru/Gmix were spherical at about 3.6 nm, and the reduction temperature did not affect their particles size. Both Ru-GIC and Ru/Gmix samples were evaluated for cinnamaldehyde (CAL) hydrogenation in supercritical carbon dioxide solvent at 323 K, and they were active to produce cinnamyl alcohol (COL) and hydrocinnamaldehyde (HAL). However, Ru-GIC samples showed higher COL selectivity than Ru/Gmix prepared at the same reduction temperature, and COL selectivity over Ru-GIC increased with the reduction treatments at 773 and 823 K.

Highly Efficient Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol over CoRe/TiO2 Catalyst.

Allylic alcohols typically produced through selective hydrogenation of α,β-unsaturated aldehydes are important intermediates in fine chemical industry, but it is still a challenge to achieve its high selectivity transformation. Herein, we report a series of TiO2-supported CoRe bimetallic catalysts for the selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) using formic acid (FA) as a hydrogen donor. The resultant catalyst with the optimized Co/Re ratio of 1:1 can achieve an exceptional COL selectivity of 89% with a CAL conversion of 99% under mild conditions of 140 °C for 4 h, and the catalyst can be reused four times without loss of activity. Meanwhile, the Co1Re1/TiO2/FA system was efficient for the selective hydrogenation of various α,β-unsaturated aldehydes to the corresponding α,β-unsaturated alcohols. The presence of ReOx on the Co1Re1/TiO2 catalyst surface was advantageous to the adsorption of C=O, and the ultrafine Co nanoparticles provided abundant hydrogenation active sites for the selective hydrogenation. Moreover, FA as a hydrogen donor improved the selectivity to α,β-unsaturated alcohols.

Rigid confined space in frustrated Lewis pair/MOF catalyst: Highly regioselective reduction of α, β-unsaturated carbonyl compounds

The regioselective hydrogenation of α, β-unsaturated carbonyl compounds is an extremely important transformation. However, its development is hampered by a lack of precise and efficient catalysts. In this work, triggered by the steric hindrance and confinement capacity of the catalyst, we designed a novel catalyst FLP/MIL-101(Cr), with the bulky frustrated Lewis pair (FLP) of PPh3 and B(C6F5)3 immobilized in NH2-MIL-101(Cr). In the well-tailored FLP/MIL-101(Cr), the promoted selective reduction behaviors were realized, with cinnamyl alcohol selectivity up to 99 % and the complete substrate conversion in cinnamyl aldehyde reduction. Experimental characterizations and theoretical calculations indicated that the CN bond and π-π stacking interaction between FLP and the organic ligand of MIL-101(Cr) implemented and reinforced a rigid structure. Compared with homogeneous FLP, the special nano-space in FLP/MIL-101(Cr) catalyst benefits the selective reduction behavior towards the unsaturated bond with the smaller steric hindrance in α,β-unsaturated carbonyl compounds. As expected, FLP/MIL-101(Cr) showed good stabilities of skeleton structure and catalytic performance. This contribution provides an ingenious strategy to design FLP heterogeneous catalysts and represents its utilization possibility in selective reduction.

Enhanced Activity of Alkali-Treated ZSM-5 Zeolite-Supported Pt-Co Catalyst for Selective Hydrogenation of Cinnamaldehyde

A bimetallic Pt8Co1 supported on alkali-treated ZSM-5 zeolite (ZSM-5-AT) was prepared through the impregnation method. The structure and surface properties of the catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2-sorption and X-ray photoelectron spectroscopy (XPS) as well as temperature-programmed desorption of NH3 (NH3-TPD) and temperature-programmed reduction of H2 (H2-TPR). The TEM images present that the bimetallic Pt8Co1 nanoparticles with a mean particle size of 4-6 nm were uniformly dispersed on the alkali-treated ZSM-5 zeolite. The bimetallic Pt8Co1/ZSM-5-AT catalyst exhibited an extraordinary COL selectivity of 65% at a >99% CAL conversion efficiency, which showed a much higher catalytic performance (including the activity and selectivity) than the monometallic Pt/ZSM-5-AT and Co/ZSM-5-AT catalysts in the selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) using hydrogen as reducing agent. The high catalytic activity of the bimetallic catalyst was attributed to the higher electron density of Pt species and more acidic sites of the alkali-treated ZSM-5 zeolite support. The recovery test showed no obvious loss of its initial activity of the Pt8Co1/ZSM-5-AT catalyst for five times.

Highly selective electrocatalytic hydrogenation of cinnamaldehyde over tin dioxide-supported palladium nanocatalysts

Selective hydrogenation of α, β-unsaturated aldehydes has always been a hot research topic owing to favorable thermodynamics in CC hydrogenation. In this work, a series of Pd/SnO2 nanocatalysts were facilely synthesized under mild conditions, via the reduction of Na2PdCl4 by dimethylaminoborane. Under galvanostatic electrolysis at 3.33 mA cm−2 for 8 h, the selective conversion of cinnamaldehyde (CAL) was achieved over Pd/SnO2-coated carbon fiber in neutral phosphate buffer, giving the cinnamyl alcohol (COL) selectivity of 78.85% at the conversion of 84.88%. The Pd/SnO2 nanocatalysts outperform commercial Pd/C catalysts, showing high COL selectivity and faradaic efficiency. The cathodic reduction potential of CAL over Pd4·3/SnO2 occurs at −0.92 V. The SnO2 support is beneficial to promote the CO adsorption of CAL and lower the HER activity of Pd nanocatalysts, thereby contributing to superior activity of Pd4·3/SnO2 for selective hydrogenation of CAL.

Photocatalytic selective hydrogenation of α,β-unsaturated aldehydes over oxygen vacancies enriched layered double hydroxide supported Co3O4 nanoparticles photocatalyst

The design of efficient photocatalyst for selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols is changeling. In this study, oxygen vacancy enriched MgAl-layered double hydroxide (MgAl-LDH) supported Co3O4 nanoparticle photocatalysts are developed taking the advantage of the semi-memory effect of CoMgAl-LDH. Excellent photocatalytic performance was achieved with a 99 % cinnamaldehyde conversion and 98 % cinnamyl alcohol selectivity at 100 °C under visible light irradiation. The electron enriched Co3O4 nanoparticles facilitated the activation of isopropanol to provide active H species under light irradiation. In situ DRIFTS and DFT calculation results suggest the oxygen vacancies of MgAl-LDH were beneficial to the terminal O adsorption of –CO group in cinnamaldehyde and ensure the high selectivity of cinnamyl alcohol. This study demonstrated a novel synthesis strategy of Co3O4 nano-photocatalyst for the efficient selective hydrogenation under visible light irradiation.

Selective hydrogenation of α,β-unsaturated aldehydes over Pt supported on cerium–zirconium mixed oxide of different composition

Cerium–zirconium mixed oxides with different Ce/Zr ratio were prepared and used as supports for Pt-containing catalysts. The study of the catalysts in the cinnamaldehyde hydrogenation reaction has shown that cinnamaldehyde conversion and cinnamyl alcohol selectivity strongly depend on the CeO2 content in the support. The highest cinnamyl alcohol yield of 81% was obtained in 105 min at room temperature and atmospheric pressure over the 1%Pt/CeO2–ZrO2 catalyst with Ce : Zr atomic ratio equal to 4 : 1.

Breaking the Activity-Selectivity Trade-Off of Pt Nanoparticles Encapsulated in UiO-66 for Hydrogenation by Constructing Suitable Hierarchical Structure

The simultaneous enhancement of activity and selectivity during hydrogenation is a great challenge. Herein, by encapsulating Pt nanoparticles (NPs) into the hierarchical defective metal–organic framework (MOF) of UiO-66, the steric screening effect of the pores, Lewis acid sites of the nodes, and metal-MOF synergy have been finely tuned and effectively utilized for selective hydrogenation. Benefiting from optimal meso/micropores, favorable Lewis acid sites and strengthened metal–support interaction, Pt NPs encapsulated in hierarchical UiO-66 exhibited superior performance in selective hydrogenation. With the proper loading of Pt NPs into suitable meso/microporous UiO-66, the conversion of cinnamaldehyde is increased from 18.2% to 85% along with the selectivity for cinnamyl alcohol being improved from 15.8% to 76% under 70 °C and 2 MPa. The conventional trade-off relationship between increasing selectivity and promoting activity for encapsulated metal catalysts has been broken with the as-developed catalyst. This study provides a promising strategy to optimize transformation efficiency by the design of a tailored MOF-based framework for encapsulating metal NPs with the needed steric effect and synergistic effect.

Self-Assembly Ultrathin Fe-Terephthalic Acid as Synergistic Catalytic Platforms for Selective Hydrogenation

Self-Assembly Ultrathin Fe-Terephthalic Acid as Synergistic Catalytic Platforms for Selective Hydrogenation

Highly stable Pt–Co bimetallic catalysts prepared by atomic layer deposition for selective hydrogenation of cinnamaldehyde

Pt–Co bimetallic catalysts were deposited on γ-Al2O3 nanoparticles by atomic layer deposition (ALD) and were used for selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL). High resolution transmission electron microscopy, hydrogen temperature‐programmed reduction, x-ray diffraction, and x-ray photoelectron spectroscopy were used to identify the strong interaction between Pt and Co. The obtained catalysts with an optimal Pt/Co ratio achieved a COL selectivity of 81.2% with a CAL conversion of 95.2% under mild conditions (i.e., 10 bar H2 and 80 °C). During the CAL hydrogenation, the addition of Co on Pt significantly improved the activity and selectivity due to the synergetic effects of Pt–Co bimetallic catalysts, resulted from the transfer of electrons from Co to Pt, which can stabilize the carbonyl groups. The obtained Pt–Co bimetallic catalysts also showed excellent stability due to the strong interaction between the metal nanoparticles and the alumina support. Negligible losses in the activity and selectivity were observed during the recycling experiments, showing the potential for practical applications.

Synergistic effects of PtFe/CeO2 catalysts afford high catalytic performance in selective hydrogenation of cinnamaldehyde

Selective hydrogenation of unsaturated aldehydes remains a grand challenge in controlling chemoselectivity up to now. We synthesized a series of PtFex/CeO2 catalysts, which were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) as well as temperature-programmed-reduction by hydrogen (H2-TPR). The catalytic performance of PtFex/CeO2, including cinnamaldehyde (CAL) conversion and selectivity toward cinnamyl alcohol (COL), is improved remarkably by introduction of Fe species in the Pt particles in the selective CAL hydrogenation under mild conditions. XPS results indicate that the electron transfer from Fe to Pt promotes CAL adsorption, resulting in the enhanced CAL conversion. And the COL selectivity is improved by CAL adsorption via an interaction of CO group with surface oxygen defect sites because of interaction between PtFe and CeO2 support. In all, this study may provide some hints to design efficient nano Pt particles for the selective hydrogenation.

Insight into the role of iron in platinum-based bimetallic catalysts for selective hydrogenation of cinnamaldehyde

Selective hydrogenation of cinnamaldehyde (CAL) toward cinnamyl alcohol (COL) is an extremely important and challenging reaction. Herein, a series of PtxFey-Al2O3 bimetallic catalysts with varied Pt to Fe ratios were prepared by incipient wetness impregnation method. The introduction of Fe significantly modifies the electronic and surface properties of Pt, which clearly enhances the C=O hydrogenation selectivity. Among all the catalysts, Pt3Fe-Al2O3 displays the best catalytic performance and the conversion of CAL is 96.6% with 77.2% selectivity of COL within 1 h. In addition, Pt3Fe-Al2O3 had excellent reusability with 76% COL selectivity after five runs of the recycle process. Further characterization of the fresh, used and cycled catalysts revealed that the structure and electronic state of the synthesized PtxFey-Al2O3 are unchanged after hydrogenation reaction. The identical-location transmission electron microscopy (IL-TEM) results revealed that the interaction between the nanoparticles and the supports was strong and the catalyst was relatively stable.

Identification and Insight into the Role of Ultrathin LDH‐Induced Dual‐Interface Sites for Selective Cinnamaldehyde Hydrogenation

AbstractFocusing on the simultaneous enhancement of activity and selectivity in α, β‐unsaturated aldehyde hydrogenation, we designed and prepared an ultrathin CoAl‐LDH supported Pt catalyst. A series of technologies revealed the ultrathin CoAl‐LDH support possesses the characteristic of dual defects, oxygen vacancy (VO) and cobalt vacancy (VCo). Then, two kinds of vacancy related interface sites were identified, namely Pt−VO−Coδ+ and Pt−VCo−OHδ−. Compared with the bulk catalyst, the ultrathin catalyst exhibits both enhanced intrinsic activity and C=O bond selectivity under the synergistic effect of the dual interface sites. Specifically, the Pt−VO−Coδ+ interface site changes the adsorption mode of cinnamaldehyde and promotes the activation of C=O bonds, thus leading to the improved cinnamyl alcohol selectivity. The H atoms of the Pt−VCo−OHδ− interface site participate in the hydrogenation process, which facilitates the mobility of active hydrogen and therefore promotes the intrinsic activity. More importantly, the ultrathin catalyst shows good reusability.

Boosting selective hydrogenation through hydrogen spillover on supported-metal catalysts at room temperature

Highly efficient hydrogenation of substrates with strong absorption on metals at low temperatures is a long-term pursuit. However, due to the scaling relationship of high binding energies on metals, the poor activity and/or selectivity are frequently observed. Herein, we described a strategy of hydrogen spillover to enable highly selective hydrogenation at low temperatures by constructing the dual-active site in PtCo alloys supported on hydroxyl-abundant cobalt borate (CoBOx), delivering a high TOF of 2479 h−1 (two orders of magnitude over PtCo/C) and 94.5 % selectivity of cinnamyl alcohol at room temperature. Experimental and theoretical investigations suggest that hydrogen and reactants are activated on PtCo alloys and second active sites on CoBOx support, respectively. Hydrogenation sequentially occurs on CoBOxvia hydrogen spillover from metal to support. Easy desorption of surface-bounded products substantially re-generates the active sites. Spillover hydrogenation on dual-active site provides a novel strategy for energy-efficiently selective hydrogenation.