Selective Hydrogenation Of Unsaturated Aldehydes Research Articles

Highly Selective Hydrogenation of Unsaturated Aldehydes in Aqueous Phase.

Chemoselective hydrogenation of carbonyl in unsaturated aldehydes is a significant process in the chemical industry, in which the development of aqueous-phase reaction systems as a substitution to organic ones is challenging. Herein, we report Ir atomic cluster catalysts anchored onto WO3-x nanorods via a reduction treatment at various temperatures (denoted as Ir/WOx-T, T = 200, 300, 400, and 500 °C), which accelerates the chemoselective hydrogenation of carbonyl groups in aqueous solutions. The optimal catalyst Ir/WOx-300 exhibits exceptional activity (TOF value: 1313.7 min-1) and chemoselectivity toward cinnamaldehyde (CAL) hydrogenation to cinnamyl alcohol (COL) (yield: ∼98.0%) in water medium, which is, to the best of our knowledge, the highest level compared with previously reported heterogeneous catalysts in liquid-phase reaction. Ac-HAADF-STEM, XAFS, and XPS verify the formation of interface structure (Irδ+-Ov-W5+ (0 ≤ δ ≤ 4); Ov denotes oxygen vacancy) induced by metal-support interaction and the largest concentration of interfacial Ir (Irδ+) in Ir/WOx-300. In situ studies (Raman, FT-IR), isotopic labeling measurements combined with DFT calculations substantiate that the hydrogenation of the C=O group consists of two pathways: water-mediated hydrogenation (predominant) and direct hydrogenation via H2 dissociation (secondary). In the former case, W5+-Ov site accelerates the activation adsorption of H2O, while Ir0 site facilitates the H-H bond cleavage of H2 and Irδ+ promotes the CAL adsorption. H2O molecule, as the source of hydrogen species, participates directly in the hydrogenation of the carbonyl group through a hydrogen-bonded network, with a largely reduced energy barrier relative to the H2 dissociation path. This work demonstrates a green catalytic route that breaks the activity-selectivity trade-off toward the selective hydrogenation of unsaturated aldehydes, which shows great potential in heterogeneous catalysis.

Sustainability in Biofuel Production Technology

It is highly desirable but quite challenging to replace precious metals with cheaper elements in the catalytic selective hydrogenation of unsaturated aldehydes. Herein, we report the preparation of a series of CuxNi3−xAlOy mixed-metal oxides (x = 0.5, 1, 2) derived from CuxNi3−xAl hydrotalcite to be used as catalysts for the promotion of the selective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL). It was found that the catalyst with the Cu2Ni1AlOy stoichiometry exhibited the best performance, with 98% FAL conversion and 99% selectivity toward FOL after 1.5 h at 120 °C and under a H2 pressure of 1.6 MPa, and also good reusability. On the basis of the combined results from catalyst characterization studies using XRD, H2-TPR, TEM, XPS, and in-situ FT-IR, it was concluded that the CuOx species on the surface of the CuxNi3−xAlOy catalysts can be reduced in situ to metallic copper during reaction, and that this Cu0 species is likely the responsible for the adsorption and conversion of FAL. The addition of Ni to these mixed-metal oxides helps disperse the Cu phase and hence make it easier to reduce and activate. It may also be that NiO can promote H2 dissociation to aid with the hydrogenation catalysis. Our work advances a new strategy for the design of simple, cheap, and efficient catalysts for the hydrogenation of FAL to FOL.

Synthesis of Dual-Active-Sites Ni-Ni2In catalysts for selective hydrogenation of furfural to furfuryl alcohol

The rational design of efficient heterogeneous catalysts for selective hydrogenation of unsaturated aldehyde to unsaturated alcohol is a long-term scientific challenge and pursuit. Herein, we prepared an effective NiIn0.2/MgO-Al2O3 catalyst with dual active sites for hydrogenation of furfural (FAL) to furfuryl alcohol (FOL), delivering a high activity and a maximum 98.9% FOL yield. Moreover, the NiIn0.2/MgO-Al2O3 exhibited excellent catalytic performances for the other unsaturated aldehydes and good durability in a 100 h stability test. Characterization and theoretical calculations reveal that H2 and FAL are adsorbed and activated on the active sites of metallic Ni and Ni2In intermetallic compound, respectively. Hydrogenation of FAL to FOL occurs on the surface of Ni2In via hydrogen spillover from metallic Ni. Sequentially, FOL easily desorbs from the surface of Ni2In owing to the active-site isolation and electron transfer effect in Ni2In. The metal-IMCs dual-active-sites mechanism provides a novel strategy for synthesizing efficient hydrogenation catalysts.

Selective hydrogenation of unsaturated aldehydes over Pd catalyst supported on N-doped porous carbon

Selective hydrogenation of unsaturated aldehydes over Pd catalyst supported on N-doped porous carbon

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.

Catalytic hydrogenation of furfural to furfuryl alcohol on hydrotalcite-derived CuxNi3−xAlOy mixed-metal oxides

It is highly desirable but quite challenging to replace precious metals with cheaper elements in the catalytic selective hydrogenation of unsaturated aldehydes. Herein, we report the preparation of a series of CuxNi3−xAlOy mixed-metal oxides (x = 0.5, 1, 2) derived from CuxNi3−xAl hydrotalcite to be used as catalysts for the promotion of the selective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL). It was found that the catalyst with the Cu2Ni1AlOy stoichiometry exhibited the best performance, with 98% FAL conversion and 99% selectivity toward FOL after 1.5 h at 120 °C and under a H2 pressure of 1.6 MPa, and also good reusability. On the basis of the combined results from catalyst characterization studies using XRD, H2-TPR, TEM, XPS, and in-situ FT-IR, it was concluded that the CuOx species on the surface of the CuxNi3−xAlOy catalysts can be reduced in situ to metallic copper during reaction, and that this Cu0 species is likely the responsible for the adsorption and conversion of FAL. The addition of Ni to these mixed-metal oxides helps disperse the Cu phase and hence make it easier to reduce and activate. It may also be that NiO can promote H2 dissociation to aid with the hydrogenation catalysis. Our work advances a new strategy for the design of simple, cheap, and efficient catalysts for the hydrogenation of FAL to FOL.

Spatial Location and Microenvironment Engineering of Pt-CeO2 Nanoreactors for Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

More than 25% of chemical transformations involve at least one hydrogenation step. Selective hydrogenation of unsaturated aldehydes is an essential process in the industrial production of pesticide...

NiBi intermetallic compounds catalyst toward selective hydrogenation of unsaturated aldehydes

Intermetallic compounds (IMCs) have evoked considerable attention as high-selectivity catalysts in chemical processes by virtue of their exceptional structural properties. Here we report a general method to obtain Ni-based IMCs via structural transformation from layered double hydroxides (LDHs) precursor, which exhibit excellent selectivity toward CO hydrogenation in various unsaturated aldehydes (crotonaldehyde, 3-methyl-2-butenal, 2-pentenal, furfural, 5-hydroxymethylfurfural and cinnamaldehyde). The optimal catalyst (NiBi IMCs) displays surprisingly high selectivity toward unsaturated alcohols (97.2%, 93.2%, 94.5%, 97.7%, 97.9% and 98.9%, respectively). A combination investigation based on STEM, XANES, and in situ COIR verifies a rugged and ordered surface atomic structure, due to the huge difference in atomic radius between Ni and Bi. Both experiment characterization (in situ FT-IR) and theory calculation (DFT) reveal that the well-organized surface atomic arrangement with a steric hindering effect gives rise to the vertical adsorption configuration of unsaturated aldehydes, resulting in selective hydrogenation of CO instead of CC group. This work shows a significant paradigm for investigation of LDHs-based IMCs catalyst via a deep viewpoint on structure-selectivity relationship, which is potentially applied as a hopeful candidate in heterogeneous hydrogenation catalysis.

Microenvironment of MOF Channel Coordination with Pt NPs for Selective Hydrogenation of Unsaturated Aldehydes

Surface and interface states of noble metal nanoparticles (MNPs), closely related to the catalytic performance, have been of great concern to academics in the field of catalysis. The catalytic prop...

Effects of Sn<i><sub>x</sub></i>Pt<i><sub>y</sub></i> Alloy Structures on the Performance of SnPt Catalysts for the Selective Hydrogenation of Unsaturated Aldehydes to Unsaturated Alcohols

Effects of Sn<i><sub>x</sub></i>Pt<i><sub>y</sub></i> Alloy Structures on the Performance of SnPt Catalysts for the Selective Hydrogenation of Unsaturated Aldehydes to Unsaturated Alcohols

Highly Selective Catalysts for the Hydrogenation of Unsaturated Aldehydes: A Review

The selective hydrogenation of unsaturated aldehydes (UAL) to saturated aldehydes (SAL) and unsaturated alcohols (UOL) is an important industrial process for producing fine chemicals. More efforts ...

CoOx@Co Nanoparticle‐based Catalyst for Efficient Selective Transfer Hydrogenation of α,β‐Unsaturated Aldehydes

AbstractCurrently, developing simple and effective catalysts for selective hydrogenation of α,β‐unsaturated aldehydes to unsaturated alcohols is challenging. Herein, an efficient CoOx‐shell/Co‐core structured nanoparticle catalyst is synthesized by a facile ultrasonic‐assisted carbothermal reduction method. The resultant catalyst exhibits outstanding catalytic performance toward the selective transfer hydrogenation of a wide spectrum of α,β‐unsaturated aldehydes into corresponding unsaturated alcohols with over 90 % selectivity. This is the simplest nonprecious metal catalyst to be reported for the selective hydrogenation of unsaturated aldehydes.

Pocketlike Active Site of Rh1/MoS2 Single-Atom Catalyst for Selective Crotonaldehyde Hydrogenation.

Selective hydrogenation of unsaturated aldehydes to unsaturated alcohols is a valuable but challenging task for synthesizing fine chemicals. We report that single Rh atoms anchored to the edges of 2D MoS2 sheets can efficiently convert crotonaldehyde to crotyl alcohol with 100% selectivity via a steric confinement effect of pocketlike active sites. Characterization results suggest that the synthesized Rh1/MoS2 single-atom catalysts (SACs) possess a unique geometric and electronic configuration, which confines the adsorption mode of the reactant molecule by a steric effect. The DFT calculations suggest that the MoS2 sheets terminate with oxidized Mo edges and the Rh1 stably anchors at the Mo cation vacancy site, which can facilely dissociate H2 to H atoms. The dissociated H atoms spill over to react with the edge O atoms to form OH species and create an HO-Mo-Rh1-Mo-OH configuration, resembling a pocketlike active site, which confines the adsorption mode of the crotonaldehyde due to steric effects. Such specific adsorption configuration yields 100% selectivity. The strategy of constructing pocketlike active centers with single metal atoms and 2D nanosheets opens new approaches to designing highly selective SACs for specific classes of catalytic transformations.

Combined synergetic and steric effects for highly selective hydrogenation of unsaturated aldehyde

Enhancing the selectivity to unsaturated alcohols for the hydrogenation of unsaturated aldehydes is of great importance and challenge. Herein, Pt-SnOx@ZIF-8 catalysts with combined synergetic and steric effects were designed for the hydrogenation of 2-pentenal. The selectivity to unsaturated alcohol was enhanced from 4.3% to 61.5% by the synergetic effect between SnOx and Pt active sites and was further enhanced to 80.9% by the steric effect of ZIF-8. In situ FTIR was used to investigate the surface reaction mode over the present catalysts. The results showed that SnOx acted as electrophilic sites for the adsorption and activation of the CO bond and the apertures of ZIF-8 oriented the CO adsorption on the active sites.

Highly Networked Platinum–Tin Nanowires as Highly Active and Selective Catalysts towards the Semihydrogenation of Unsaturated Aldehydes

AbstractThe selective hydrogenation of α,β‐unsaturated aldehydes to unsaturated alcohols is an important process for many industrial applications, whereas the realization of excellent conversion efficiency and selectivity remains a significant challenge. Herein, we report the preparation of a class of networked Pt–Sn nanowires (Pt–Sn NWs) for the selective hydrogenation of unsaturated aldehydes to the desired unsaturated alcohols. The optimized Pt1.5Sn NWs delivered a high conversion efficiency (98.1 %) for the hydrogenation of cinnamaldehyde (CAL) and excellent selectivity to cinnamyl alcohol (COL) (90.6 %); thus, they outperformed Pt1.5Sn nanoparticles (NPs) as well as Pt NPs. The high performance of the Pt1.5Sn NWs was expanded to the hydrogenation of other α,β‐unsaturated aldehydes. X‐ray photoelectron spectroscopy revealed that a high ratio of metallic Pt in the Pt1.5Sn NWs boosted the conversion of CAL and that a high Sn content favored the hydrogenation of the C=O bond, both of which lead to excellent activity and selectivity.

Selective hydrogenation of unsaturated aldehydes over Pt nanoparticles promoted by the cooperation of steric and electronic effects.

The selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols can reach high selectivity and activity at room temperature using Pt nanoparticles immobilized on a non-porous Al2O3 support stabilized by aspartic acid. Aspartic acid molecules had a significant steric effect on C[double bond, length as m-dash]C hydrogenation and could modify the electronic state of metal particles.

Synthesis of bimetallic SnPt-nanoparticle catalysts for chemoselective hydrogenation of crotonaldehyde: Relationship between SnxPty alloy phase and catalytic performance

Bimetallic SnPt-nanoparticle (SnPt-NP) catalysts with several types of SnxPty alloy structures were prepared using a polyalcohol reduction process; the catalytic behavior of each SnxPty alloy phase toward the selective hydrogenation of unsaturated aldehydes to the corresponding unsaturated alcohols was elucidated. Atomic absorption spectroscopy (AAS) and transmission electron microscopy (TEM) indicate that SnPt-NP catalysts with various Sn/Pt atomic ratios can be successfully prepared by a polyalcohol reduction process using Pt(acac)2 and Sn(AcO)2 as the metal precursors. X-ray diffraction (XRD) results reveal that the Sn1Pt3, Sn1Pt1, and Sn2Pt1 alloy phases are formed through control of the Sn/Pt atomic ratio of the starting mixture during preparation. The Sn1Pt3 alloy phase enhanced the hydrogenation of both the CC and CO bonds during the selective hydrogenation of crotonaldehyde. When only Sn1Pt1 alloy phases (Sn/Pt = 1.40), accompanying with separated Sn phase, were formed in the SnPt-NP catalysts, the highest unsaturated alcohol (UOL) selectivity (71.5% at 37.6% conversion) was observed. The formation of the Sn2Pt1 alloy phase led to decreased UOL selectivity. We suggest that the Sn1Pt1 alloy phase is an effective bimetallic SnPt hydrogenation catalyst for the selective formation of unsaturated alcohols.

Heterogeneous catalysis for green chemistry based on nanocrystals

Abstract Modern society has an ever-increasing demand for environmentally friendly catalytic processes. Catalysis research is working towards a solution through the development of effective heterogeneous catalysts for environment-related applications. Nanotechnologies have provided effective strategies for the preparation of nanocrystals (NCs) with well-defined sizes, shapes and compositions. Precise control of these NCs provides an important foundation for the studies of structure-performance relationships in catalysis, which is critical to the design of NCs with optimized catalytic performances for practical applications. We focus on recent advances in the development of bottom-up strategies to control NCs structures for some key catalytic applications, including CO oxidation, selective oxidation of alcohols, semihydrogenation of alkynes, and selective hydrogenation of unsaturated aldehydes and nitrobenzene. These key applications have been a popular research focus because of their significance in green chemistry. Herein we also discuss the scientific understandings of the active species and active structures of these systems to gain an insight for rational design of efficient catalytic systems for these catalytic reactions.

Selective Hydrogenation of Unsaturated Aldehyde in a Gas–Liquid–Liquid–Solid Batch Reactor

Selective Hydrogenation of Unsaturated Aldehyde in a Gas–Liquid–Liquid–Solid Batch Reactor

Theoretical Studies of Species Related to Acrolein Hydrogenation

Unsaturated alcohols, usually produced from selective hydrogenation of unsaturated aldehydes, are important fine chemical intermediates used to synthesize pharmaceuticals and flavoring materials. Acrolein, the smallest member in α, β-unsaturated aldehydes, is the model system for studying selective hydrogenation of α, β-unsaturated aldehydes. So far most theoretical work is about adsorption and reactions of acrolein and its related species on surfaces. In the present paper we systematically studied the geometries, electronic structures, stability and transformation of various species derived from stepwise hydrogenation of acrolein in the gas phases. We identified the most stable intermediates for each system and determined the energy barrier for intermolecular conversion between isomers for various species with different content of hydrogen. All these results are valuable and informative for understanding the surface chemistry of hydrogenation of α, β-unsaturated aldehydes.