Hydrogenation Of Diphenylacetylene Research Articles

Single-Atom Alloy Pd1Ag10/CeO2–ZrO2 as a Promising Catalyst for Selective Alkyne Hydrogenation

The effect of support on the performance of Pd1Ag10/Al2O3 and Pd1Ag10/CeO2–ZrO2 catalysts in the selective hydrogenation of diphenylacetylene (DPA) was studied. Characterization of the catalyst by DRIFTS-CO and HRTEM revealed the formation of a PdAg single-atom alloy (SAA) structure on the surface of PdAg nanoparticles, with Pd1 sites isolated by Ag atoms. It was found that the use of CeO2–ZrO2 as a carrier makes it possible to increase the activity of the Pd1Ag10 catalyst by a factor of three without loss of selectivity compared to the reference Pd1Ag10/Al2O3. According to the HRTEM data, this catalytic behavior can be explained by an increase in the dispersion of Pd1Ag10/CeO2–ZrO2 compared to its Pd1Ag10/Al2O3 counterpart. As evidenced by DRIFTS-CO data, the high selectivity of the Pd1Ag10/CeO2–ZrO2 sample presumably stems from the stability of the structure of isolated Pd1 sites on the surface of SAA Pd1Ag10/CeO2–ZrO2.

Formation of Metal–Hypercrosslinked Polystyrene Composites in a Supercritical Carbon Dioxide Medium and Their Catalytic Properties in the Hydrogenation of Diphenylacetylene

Formation of Metal–Hypercrosslinked Polystyrene Composites in a Supercritical Carbon Dioxide Medium and Their Catalytic Properties in the Hydrogenation of Diphenylacetylene

Highly Active Bimetallic Single-Atom Alloy PdAg Catalysts on Cerium-Containing Supports in the Hydrogenation of Alkynes to Alkenes

A study of a series of single-atom-alloy catalysts Pd1Ag3/Al2O3, Pd1Ag3/CeO2–Al2O3, and Pd1Ag3/CeO2–ZrO2 in the selective hydrogenation of diphenylacetylene (DPA) showed a significant (five-fold) increase in activity for the PdAg3/CeO2–ZrO2 sample in comparison with that of Pd1Ag3/Al2O3. It was especially noted that the increase in activity was not accompanied by a decrease in the selectivity for the target product. This catalytic behavior can be explained by two factors: (1) a more than twofold increase in the dispersity of the PdAg3/CeO2–ZrO2 catalyst and (2) a change in the electronic state of the nanoparticles, as determined from the results of an IR-spectroscopic study of adsorbed CO. The retention of the high selectivity of the synthesized catalysts indicated the stability of the structure of Pd1 monoatomic sites in the catalysts prepared by deposition on Ce-containing supports, which was also confirmed by the IR spectroscopy of adsorbed CO. The experimental results indicate that Ce-containing supports are promising for the synthesis of catalysts for the selective hydrogenation of substituted alkynes.

Deliberate control of the structure-specific active sites in PdIn bimetallic catalysts using adsorbate induced segregation effects

A bimetallic PdIn/Al2O3 catalyst has been prepared, characterized by diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO (DRIFTS CO), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and tested towards the liquid-phase diphenylacetylene hydrogenation at room temperature. It was shown that the freshly reduced catalyst contains PdIn intermetallic nanoparticles that demonstrate excellent selectivity in the diphenylacetylene selective hydrogenation to diphenylethylene ∼ 98 % at 90 % conversion. An oxidative treatment of the catalyst induces preferential oxidative leaching of the In component from the intermetallic compound, modifying the catalyst active sites structure to the state with a high hydrogenation activity but poor stilbene selectivity. The changes upon the redox treatments are essentially reversible and reproducible. This effect can be intentionally used to get an optimum balance between activity and selectivity of the catalyst.

Effect of Iodide on the pH-Controlled Hydrogenations of Diphenylacetylene and Cinnamaldehyde Catalyzed by Ru(II)-Sulfonated Triphenylphosphine Complexes in Aqueous–Organic Biphasic Systems

The effect of NaI on hydrogenation of diphenylacetylene catalyzed by the water-soluble [{RuCl(mtppms-Na)2}2(µ-Cl)2] (1) (mtppms-Na = meta-monosulfonated triphenylphosphine sodium salt) is reported. Hydrogenations were performed under mild conditions (P(H2) = 1 bar, T = 50–80 ℃) in aqueous–organic biphasic reaction mixtures wherein the catalyst was dissolved in aqueous phase of various pHs. In acidic solutions, addition of NaI to 1 + mtppms-Na increased the selective conversion of diphenylacetylene to stilbenes from 10% to 90% but did not effect the high Z-selectivity (up to 98%). In contrast, in basic solutions the major product was diphenylethane (up to 70%), and the yield of E-stilbene exceeded that of the Z-isomer. 1H and 31P NMR measurements revealed that depending on the absence or presence of NaI, the catalytically active Ru(II)-hydride species in acidic solutions was [RuHCl(mtppms-Na)3], 2, or [RuHI(mtppms-Na)3], 5, respectively, while in basic solutions, both 2 and 5 were hydrogenated further to yield the same hydride species, cis,fac-[RuH2(H2O)(mtppms-Na)3]. [RuHI(mtppms-Na)3] proved superior to [RuHCl(mtppms-Na)3] as a catalyst for the selective hydrogenation of cinnamaldehyde to dihydrocinamaldehyde. This finding was explained by a facile formation of a (putative) dihydrogen complex [Ru(H2)I2(H2O)(mtppms-Na)2] intermediate, resulting in fast heterolytic activation of H2.

Pd/Ag Nanoparticles Prepared in Ionic Liquids as Model Catalysts for the Hydrogenation of Diphenylacetylene

AbstractThe preparation of bimetallic Pd/Ag‐based model catalysts is addressed to study the promotional effects of Ag doping in the liquid‐phase semi‐hydrogenation of diphenylacetylene. The precursor concept is employed where colloidal bimetallic Pd/Ag nanoparticles are initially synthesized and then used as well‐defined building units for catalyst preparation. This approach allows for tuning the composition of the nanoparticles independently with the two metals co‐localized to a fine extent. Size and composition of the nanoparticles are preserved after immobilizing them on a carbon support.

Selective hydrogenation of diphenylacetylene using NiCo nanoparticles supported on mesoporous carbon as catalyst.

Hydrogenation of alkynes to alkenes is an important procedure in the synthesis of organic compounds. In this study, selective hydrogenation was carried out on diphenylacetylene as a model of alkyne compounds using NaBH4 as a hydrogen source and NiCo bimetallic nanoparticles supported on mesoporous carbon (NiCo/MC) as a catalyst. The mesoporous carbon was prepared using the soft-templated method from phloroglucinol and formaldehyde as precursors while the NiCo/MC catalyst was synthesized using a wet impregnation method. Based on surface area analysis, it was found that the pore diameters of MC, Ni/MC, and NiCo/MC were 12.8 nm, 13.4 nm, and 12.7 nm respectively, which indicated the mesoporous size of the materials. TEM analysis also confirmed the formation of nanoparticles on mesoporous carbon with the average size similar to the pore structure of the support, thus indicating the incorporation of the metals on the support. The hydrogenation reaction of diphenylacetylene was carried out with variations in reaction time and temperature. GCMS analysis of the products showed that the optimum conditions were obtained over NiCo/MC catalyst at 50 °C for 4 h with a diphenylacetylene conversion of 71.5% and a selectivity of 87.1% for the formation of cis-stilbene.

Kinetics of liquid-phase diphenylacetylene hydrogenation on “single-atom alloy” Pd-Ag catalyst: Experimental study and kinetic analysis

• Pd 1 Ag 3 SAA catalyst demonstrates extremely high selectivity in diphenylethene (ca. 98 %). • Selectivity of Pd 1 Ag 3 does not depend on P(H 2 ) and DPA concentration. • Proposed kinetic model is capable to describe the experimental dependencies. Catalytic performance of Pd 1 Ag 3 /Al 2 O 3 single-atom alloy (SAA) catalyst was studied in liquid-phase hydrogenation of diphenylacetylene (DPA) and compared with the performance of the reference monometallic Pd/Al 2 O 3 . Formation of SAA structure in Pd 1 Ag 3 /Al 2 O 3 was confirmed by FTIR CO technique. It was found that Pd 1 Ag 3 /Al 2 O 3 single-atom alloy catalyst exhibits excellent selectivity in diphenylethene (stilbene) (ca. 98 %), which remains constant over a wide range of DPA conversions (0–95%), while over Pd/Al 2 O 3 selectivity decreases steadily with the increase in DPA conversion. It is remarkable that the selectivity of Pd 1 Ag 3 /Al 2 O 3 depends neither on hydrogen pressure (5–15 bar), nor on DPA concentration (0.0262 – 0.159 mol/l). In contrast, over the reference Pd/Al 2 O 3 selectivity tends to decrease with increasing P(H 2 ) and decreasing DPA concentration. The proposed reaction network comprises hydrogenation of DPA in a parallel formation of cis and trans -stilbene with following hydrogenation to bibenzyl and direct formation of the latter from the initial DPA. The calculations clearly shows the capability of the kinetic model to describe the experimental dependencies for Pd 1 Ag 3 single-atom catalyst in an excellent way with the degree of explanation equal to ca. 99 %.

Synthesis of Supported Heterogeneous Catalysts by Laser Ablation of Metallic Palladium in Supercritical Carbon Dioxide Medium.

To obtain a supported heterogeneous catalyst, laser ablation of metallic palladium in supercritical carbon dioxide was performed in the presence of a carrier, microparticles of γ-alumina. The influence of the ablation process conditions—including supercritical fluid density, ablation, mixing time of the mixture, and laser wavelength—on the completeness and efficiency of the deposition of palladium particles on the surface of the carrier was studied. The obtained composites were investigated by scanning and transmission electron microscopy using energy dispersive spectroscopy. We found that palladium particles were nanosized and had a narrow size distribution (2–8 nm). The synthesized composites revealed high activity as catalysts in the liquid-phase hydrogenation of diphenylacetylene.

Synthesis of Heterogeneous Catalysts by Laser Ablation of Metallic Palladium with Deposition on Alumina in Supercritical Carbon Dioxide

An experimental setup is designed and assembled to produce deposited heterogeneous catalysts by laser ablation of a metal target in the presence of various carriers in supercritical carbon dioxide (SC-CO2). The conditions of pulsed laser exposure (wavelength, frequency, and time), parameters of an SC-CO2 medium (pressure and temperature), and configuration of the experimental setup (laser, target, carrier, and visual and optical control components) are determined. A composite comprised of Al2O3 with Pd particles is prepared in this setup by the laser ablation of metal palladium with deposition onto γ-alumina in an SC-CO2 medium. Studying the synthesized composite as a catalyst in the liquid-phase hydrogenation of diphenylacetylene shows its high level of activity (TOF = 1.45 s–1) and high selectivity in the hydrogenation of one bond of the triple bond.

Synthesis of Polymer–Metal Composites by the Impregnation of Hypercrosslinked Polystyrene with Palladium Compounds in Supercritical Carbon Dioxide and Their Catalytic Activity in the Liquid-Phase Hydrogenation of Diphenylacetylene

Composites—palladium metal particles in a polymer matrix—are obtained by impregnation of hypercrosslinked polystyrene with palladium compounds in supercritical carbon dioxide (SC-CO2) followed by molecular hydrogen reduction. The synthesized composites exhibit a high level of catalytic activity in the liquid-phase hydrogenation of diphenylacetylene (DPA). The turnover frequency (TOF) is 15–50 min–1 and the selectivity in the formation of diphenylethylene is 60–80% at ~90% conversion of the substrate.

Highly Selective and Efficient Electrocatalytic Semihydrogenation of Diphenylacetylene to Z-Stilbene Using Pt-Pd Alloy Cathode Catalyst

The electrical energy can be provided from renewable energy source such as solar and wind, thus making the electrocatalytic hydrogenation process is expected one of important technology to reduce carbon dioxide emission in organic synthesis industry. The selective hydrogenation of alkynes to Z-alkenes is highly important for the construction of numerous valuable compounds, such as bioactive molecules, natural products, flavors, and industrial materials. Although a number of methods for the stereoselective synthesis of Z-alkenes have been developed so far, the Lindlar catalytic semihydrogeneation of alkynes is a long-standing synthetic transformation and still remains the favored system. HoweveTo develop more environmentally benign and efficient semihydrogenation systems, we have demonstrated electrocatalytic hydrogenation of diphenylacetylene (DPA) in a proton exchange membrane (PEM) reactor. 1 In our system, the oxidation of water was employed as an anodic process (Figure 1 (a)).Especially, in this work, we have investigated systematically influences of catalyst materials such as Pt, Pd, and PtPd alloy for a PEM reactor on the product selectivity for Z-stilbene and partial current density for Z-stilbene formation in the hydrogenation of diphenylacetylene. As a result, PtPd alloy with a composition of Pt1Pd99 was found to be a most suitable catalyst material in order to achieve both high partial current density for Z-stilbene formation and high Z-stilbene selectivity (Figures 1 (b) and (c)). As shown in Figure 1 (b), it was also found that the partial current density for Z-stilbene is much improved by the addition of a small amount of Pt which has the high hydrogenation activity. Moreover, the synergy of Pt electrocatalysis for the formation of adsorbed hydrogen species (Had) (H+ + e− → Had) and Pd catalysis for hydrogenation of DPA (2Had + DPA → Z-stilbene) might be required in order to achieve the high stereoselective formation of Z-stilbene. Acknowledgement This work was support by JST CREST Grant No. JPMJCR18R1, Japan. The authors gratefully acknowledge for ISHIFUKU Metal Industry corporation the generous gift for cathode catalysts. References 1) A. Fukazawa, J. Minoshima, K. Tanaka, Y. Hashimoto, Y. Kobori, Y. Sato, M. Atobe, ACS Sustain. Chem. Eng. 2019, 7, 11050–11055. Figure 1

Alumina-Supported Palladium–Silver Bimetallic Catalysts with Single-Atom Pd1 Sites in the Liquid-Phase Hydrogenation of Substituted Alkynes

The catalytic characteristics of Pd–Ag/Al2O3 bimetallic catalysts with an Ag/Pd atomic ratio of 0.03–3.0 have been studied in the selective liquid-phase hydrogenation of diphenylacetylene and 1-phenyl-1-propyne. It has been found that an increase in the Ag/Pd ratio leads to a significant increase in selectivity, which, however, is accompanied by a decrease in the catalyst activity. Comparison with data of an earlier structural study suggests that an increase in selectivity observed with an increase in the Ag/Pd ratio to 0.5–1.0 is attributed to the following two factors: (1) the suppression of the formation of palladium hydride and (2) an increase in the fraction of “single-atom” Pd1 sites isolated from each other by Ag atoms on the surface of the Pd–Ag nanoparticles. An increase in the Ag/Pd value to 2.0–3.0 leads to a further increase in the selectivity, which exceeds the selectivity of a commercial Lindlar catalyst (Pd–Pb/CaCO3). In this case, the most probable cause of the high selectivity is the formation of the single-atom Pd1 sites on the surface of the Pd–Ag alloy and an increase in the stability of the structure.

Experimental and theoretical analysis of particle size effect in liquid-phase hydrogenation of diphenylacetylene

The liquid-phase hydrogenation of diphenylacetylene (DPA) over 1 wt% Pd/Al2O3 catalysts with the mean palladium cluster size varying from 1.9 to 20 nm was studied at 5 bar H2 pressure and 25 °C. Hydrogenation of the triple bond was found to be structure sensitive and turnover frequency increased as Pd cluster size increased, while TOF in hydrogenation of the intermediate stilbene was essentially independent on the cluster size. Selectivity to stilbene was rather high (90–94%) and tends to increase with an increasing of Pd particle size.A reaction network was proposed for diphenylacetylene hydrogenation involving formation of cis- and trans- stilbene and their subsequent hydrogenation. The effect of Pd nanoparticle size on the hydrogenation kinetics was analyzed and discussed using a geometric approach based on the respective contribution of low (edges, corners) and highly coordinated sites (terraces) for a cubooctahedral shape of metal clusters. A quantitative description of the concentration dependences was performed incorporating the Pd particle size in the rate equations through changes in dispersion and the ratio of sites of different coordination. An excellent correspondence between theory and experiments was demonstrated.

Intermetallic PdxIny/Al2O3 catalysts with isolated single-atom Pd sites for one-pot hydrogenation of diphenylacetylene into trans-stilbene

Novel one-pot synthesis of trans-stilbene comprises hydrogenation of diphenylacetylene into cis-stilbene followed by its hydroisomerization, over the catalyst being intermetallic PdxIny/Al2O3 system with isolated single-atom Pd1 sites. The hydroisomerization rate in the process is comparable or exceeds the over-hydrogenation into 1,2-diphenylethane thus providing 76% yield of trans-stilbene in the case of Pd2In3/Al2O3 catalyst. This result presumably stems from the formation of ordered single-atom Pd1 sites with favorable hydroisomerization ability on the surface of PdxIny catalysts.

Electrocatalytic Semihydrogenation of Alkynes to Z-Alkenes Using a Proton Exchange Membrane Reactor: Influence of Catalyst Materials on Product Selectivity and Reaction Rate

Z-alkenes are versatile building blocks in organic synthesis and often found in pharmaceuticals, perfumes, and natural products. Although a number of methods for stereoselective synthesis of Z-alkene have been developed so far, the Lindlar semihydrogeneation of alkynes is a long-standing synthetic transformation and still remains a privileged system. However, it used toxic Pb additive and a large amount of quinolone, and has other limitations such as narrow substrate scope. Therefore, development of a powerful and reliable system for stereoselective semihydrogenation of alkyne to Z-alkene as alternative to the Lindlar catalytic system is still challenging target.Under these backgrounds, we have demonstrated electrocatalytic hydrogenation in a proton exchange membrane reactor so called PEM reactor to develop a powerful and reliable stereoselective semihydrogenation system. Especially, in this work, we have investigated systematically influences of catalyst materials such as Pt, Pd, and PtPd alloy for a PEM reactor on the product selectivity for Z-stilbene and partial current density for Z-stilbene formation in the hydrogenation of diphenylacetylene. As a result, PtPd alloy with a composition of 1(Pt):99(Pd) was found to be a most suitable catalyst material in order to achieve both high Z-stilbene selectivity and high partial current density for Z-stilbene formation (Figure 1).The authors gratefully acknowledge support by JST CREST Grant No. JPMJCR18R1, Japan.Ref. A. Fukazawa, J. Minoshima, K. Tanaka, Y. Hashimoto, Y. Kobori, Y. Sato, M. Atobe, ACS Sustain. Chem. Eng. 2019, 7, 11050-11055. Figure 1

Rare-Earth Supported Nickel Catalysts for Alkyne Semihydrogenation: Chemo- and Regioselectivity Impacted by the Lewis Acidity and Size of the Support.

Bimetallic catalysts of nickel(0) with a trivalent rare-earth ion or Ga(III), NiML3 (where L is [iPr2PCH2NPh]-, and M is Sc, Y, La, Lu, or Ga), were investigated for the selective hydrogenation of diphenylacetylene (DPA) to (E)-stilbene. Each bimetallic complex features a relatively short Ni-M bond length, ranging from 2.3395(8) Å (Ni-Ga) to 2.5732(4) Å (Ni-La). The anodic peak potentials of the NiML3 complexes vary from -0.48 V to -1.23 V, where the potentials are negatively correlated with the Lewis acidity of the M(III) ion. Three catalysts, Ni-Y, Ni-Lu, and Ni-Ga, showed nearly quantitative conversions in the semihydrogenation of DPA, with NiYL3 giving the highest selectivity for (E)-stilbene. Initial rate studies were performed on the two tandem catalytic reactions: DPA hydrogenation and (Z)-stilbene isomerization. The catalytic activity in DPA hydrogenation follows the order Ni-Ga > Ni-La > Ni-Y > Ni-Lu > Ni-Sc. The ranking of catalysts by (Z)-stilbene isomerization initial rates is Ni-Ga ≫ Ni-Sc > Ni-Lu > Ni-Y > Ni-La. In operando 31P and 1H NMR studies revealed that in the presence of DPA, the Ni bimetallic complexes supported by Y, Lu, and La form the Ni(η2-alkyne) intermediate, (η2-PhC≡CPh)Ni(iPr2PCH2NPh)2M(κ2-iPr2PCH2NPh). In contrast, the Ni-Ga resting state is the Ni(η2-H2) species, and Ni-Sc showed no detectable binding of either substrate. Hence, the mechanism of Ni-catalyzed diphenylacetylene semihydrogenation adheres to two different kinetics: an autotandem pathway (Ni-Ga, Ni-Sc) versus temporally separated tandem reactions (Ni-Y, Ni-Lu, Ni-La). Collectively, the experimental results demonstrate that modulating a base-metal center via a covalently appended Lewis acidic support is viable for promoting selective alkyne semihydrogenation.

Theoretical Calculations on the Mechanism of Hydrogenation of Diphenylacetylene over Pdn (n = 1-4) Clusters

Diphenylacetylene (DPA) is a precursor of stilbene and benzil, and reduction of DPA or its derivatives with metallic reagents is both an old and contemporary topic of research. By means of density function theory (DFT) calculations, a detailed investigation of the mechanism of the hydrogenation of DPA over Pd clusters was carried out at the molecular level. The various species structures in the hydrogenation of DPA over Pd clusters were optimized and analyzed. The calculations indicate that the reactions over different Pd clusters share similar reaction mechanisms, and the entire reaction path could be divided into approximately two stages: stage 1: the hydrogenation of DPA to stilbene by the addition of one hydrogen molecule; and stage 2: the hydrogenation of stilbene to the final product diphenylethane (DPE) with the recovery of the catalyst. The Pd2- and Pd3-catalyzed systems exhibit the smallest rate-determining step (RDS) energy barrier, and these systems might be the most active and effective catalytic species among the Pd clusters. Although the Pd clusters used in the current work are simple systems, these clusters could eventually provide insights into the specific structure of the Pd catalyst, since Pd and/or clusters and/or nanoparticles could be envisioned as active catalysts in experiments.

Liquid-Phase Hydrogenation of Internal and Terminal Alkynes on Pd–Ag/Al2O3 Catalyst

The structure and catalytic properties of a bimetallic Pd–Ag/α-Al2O3 catalyst are studied in the liquid-phase hydrogenation of substituted internal and terminal alkynes using diphenylacetylene, phenylacetylene, 1-phenyl-1-propyne, and 1-phenyl-1-butyne as sample alkynes. IR spectroscopy of adsorbed CO, X‑ray diffraction (XRD), and electron microscopy were used to show that the active sites on the Pd–Ag nanoparticle surface are Pd1 sites. The synthesized Pd–Ag/α-Al2O3 catalyst shows a much higher selectivity in the hydrogenation of internal symmetric and asymmetric alkynes compared to the monometallic Pd/α‑Al2O3 sample. Also, it was found in the hydrogenation of diphenylacetylene and 1-phenyl-1-propyne on Pd–Ag/α-Al2O3 that the rate of the stage of desired olefin hydrogenation substantially decreases, which favors the kinetic control of the process.

Effects of pyrolysis temperatures on the textural, magnetic, morphology, and catalytic properties of supported nickel nanoparticles

The development of base metal catalysts for industrially important reactions continues to be an important goal of catalysis research. Herein, the effects of pyrolysis temperature on the textural, structural, surface, magnetics properties and catalytic properties of silica-supported nickel nanoparticles (NiNPs) were thoroughly investigated. Mono-dispersed NiNPs encapsulated in graphitic shells were first successfully obtained and were characterized using a variety of methods such as BET surface area measurement, CO-pulse chemisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HR-TEM), and superconducting quantum interference device (SQUID) measurement. The findings showed that all catalysts’ properties were considerably altered with change in pyrolysis temperature. Hydrogenation of diphenylacetylene was then selected as the model reaction for the evaluation of the catalytic performance of the graphitic-shelled NiNPs. After testing, pyrolysis of a nickel at 800 °C (catalyst A) displayed tremendous activity and selectivity to produce >94% of stilbene with selectivities of 99% for the Z-isomer.