Hydrogenation Of Phenylacetylene Research Articles

Rapidly solidified Al-Cu-Co quasicrystalline alloy: microstructure and catalytic properties

This study presents the characterisation and evaluation of the catalytic potential of an alloy with a composition referring to the quasicrystal from the Al-Cu-Co system. The material was synthesised through a melt-spinning process, providing rapid solidification conditions and a favourable material form of thin ribbons. Microstructural and chemical analyses were performed using scanning electron microscopy, X-ray diffraction and transmission electron microscopy methods. The obtained results confirmed the presence of a major phase which was a decagonal quasicrystal in the form of globular grains and additional crystalline phases occurring along the grain boundaries. The catalytic potential of the materials was explored using phenylacetylene hydrogenation. The catalyst, obtained by pulverising the ribbons, demonstrated catalytic activity with over 40% phenylacetylene conversion and selectivity exceeding 60% for styrene production under mild reaction conditions. The recovered catalyst displayed a stable phase composition, as confirmed by X-ray diffraction, and unchanged morphology, indicating the possibility of catalyst reuse for subsequent reaction cycles. The presented results provide insight into the experimental verification of the catalytic properties of the developed environmentally friendly catalysts.

Understanding selective hydrogenation of phenylacetylene on PdAg single atom alloy: DFT insights on molecule size and surface ensemble effects

Single atom alloys (SAAs) have proven to be effective catalysts, offering customizable properties for diverse chemical processes. Various metal combinations are used in SAAs and Pd dispersed materials are frequently employed in catalyzing hydrogenation reactions. Herein, we explore the hydrogenation of phenylacetylene to styrene and ethylbenzene on PdAg SAA using density functional theory calculations. Our results show that while PdAg SAA does improve the activity of the host Ag towards hydrogenation, a dilute PdAg SAA surface with isolated Pd-atoms is not selective towards partial hydrogenation of phenylacetylene. Additionally, we investigate how the size of the reactant molecule, the size of the metal alloy ensemble, and a ligand effect impact the hydrogenation process. The SAA enhances the binding strengths of various organic adsorbates, although this effect diminishes as the adsorbate size increases. Our findings indicate the dilute PdAg exhibits selectivity towards hydrogenation of smaller molecules such acetylene due to its distinct adsorption geometry. The selective hydrogenation of phenylacetylene necessitates a surface Pd dimer ensemble. Our research highlights the importance of both reactant molecule size and surface configurations in SAA catalysts. This is particularly crucial when dealing with the adsorption of sizable organic molecules where the functional group can adopt different adsorption modes.

Triple Play of Band Gap, Interband, and Plasmonic Excitations for Enhanced Catalytic Activity in Pd/HxMoO3 Nanoparticles in the Visible Region.

Plasmonic photocatalysis has been limited by the high cost and scalability of plasmonic materials, such as Ag and Au. By focusing on earth-abundant photocatalyst/plasmonic materials (HxMoO3) and Pd as a catalyst, we addressed these challenges by developing a solventless mechanochemical synthesis of Pd/HxMoO3 and optimizing photocatalytic activities in the visible range. We investigated the effect of HxMoO3 band gap excitation (at 427 nm), Pd interband transitions (at 427 nm), and HxMoO3 localized surface plasmon resonance (LSPR) excitation (at 640 nm) over photocatalytic activities toward the hydrogen evolution and phenylacetylene hydrogenation as model reactions. Although both excitation wavelengths led to comparable photoenhancements, a 110% increase was achieved under dual excitation conditions (427 + 640 nm). This was assigned to a synergistic effect of optical excitations that optimized the generation of energetic electrons at the catalytic sites. These results are important for the development of visible-light photocatalysts based on earth-abundant components.

Tuning the electronic structure of Pd by the surface configuration of Al2O3 for hydrogenation reactions.

The electronic interaction between a metal and a support modulates the electronic structures of supported metals and plays an important role in manipulating their catalytic performance. However, this interaction is mainly realized in heterogeneous catalysts composed of reducible oxides. Herein, we demonstrate the electronic interaction between γ-Al2O3 and η-Al2O3 with varying acid-base properties and supported Pd nanoparticles (NPs) of 2 nm in size. The strength and number of acid-base sites on the supports and catalysts were systemically characterized by FT-IR spectroscopy and TPD. The supported Pd NPs exhibit electron-rich surface properties by receiving electrons from the electron-donating basic sites on γ-Al2O3, which are beneficial for catalyzing the hydrogenation of nitrobenzene. In contrast, Pd NPs loaded on η-Al2O3 are electron-deficient because of the rich electron-withdrawing acid sites of η-Al2O3. As a result, Pd/η-Al2O3 exhibits higher catalytic activity in phenylacetylene hydrogenation than Pd/γ-Al2O3. Our results suggest a promising route for designing high-performance catalysts by adjusting the acid-base properties of Al2O3 supports to maneuver the electronic structures of metals.

Navigating through Complexity: Optimizing Cathodes for Organic Electrohydrogenation through Coherent Workflows

AbstractElectrochemical hydrogenation reactions offer a green and sustainable production pathway for both bulk and fine chemicals employed in the modern chemical industry. However, optimizing such systems can be tremendously challenging due to the number of variables that potentially influence the overall performance. The tailored and scalable electrode fabrication via catalytic inks can be especially difficult due to the complex interplay of material and process variables during the formulation of the inks and their deposition on suitable substrates. As a result, the significance of each variable must be systematically investigated to reveal the high‐impact and low‐impact variables, enabling rapid progression towards finding optimal conditions and parameters. In this work, we present an adaptable, coherent workflow to proficiently optimize electrode fabrication for electrochemical hydrogenation reactions with well‐adjustable experimental effort. Using the hydrogenation of phenylacetylene as a model reaction in a scalable zero‐gap reactor, we demonstrate the influence of deposition techniques, substrates, and catalyst loadings as well as the interactions of binders and additives on the electrochemical performance. Future works can greatly benefit from this coherent workflow as it enables direct comparability between datasets and functional, multidimensional optimization, hastening the rate at which new material systems are understood, reach maturity, and become industrially relevant.

Efficient selective hydrogenation of terminal alkynes over Pd–Ni nanoclusters encapsulated inside S-1 zeolite

Selective hydrogenation of alkynes is a challenging reaction that requires selective and efficient catalysts to achieve the desired alkenes. The development of general and robust catalysts that can operate under mild conditions and tolerate a wide range of functional groups is still an active area of research. Here, Pd-M bimetallic clusters (M = Ni, Cu, Mn, Fe) encapsulated inside S-1 zeolite were prepared and applied in the selective hydrogenation of substituted terminal alkynes. Among them, the Pd0.6Ni@S-1 catalyst displayed 91 % selectivity to styrene at the full conversion of phenylacetylene. Derivatives of phenylacetylene containing either electron withdrawing/donating or sensitive functional groups were effectively converted into the corresponding alkenes. The confinement effect of zeolite effectively inhibited the over-hydrogenation reaction and enhanced the stability of the catalysts. Furthermore, the product distribution was solvent-dependent by correlating the reaction selectivity with solvent properties. Apolar solvent showed the highest selectivity to styrene in the selective hydrogenation of phenylacetylene due to the competitive adsorption of apolar solvent and styrene on catalysts.

Microwave Synthesis of Nickel-Based Catalysts for Selective Hydrogenation of Phenylacetylene to Styrene

Microwave Synthesis of Nickel-Based Catalysts for Selective Hydrogenation of Phenylacetylene to Styrene

Microstructural characterization of rapidly solidified Al-13.5 at.% Cr and Al-13.5 at.% V alloys for catalytic applications

Intermetallic compounds, due to their well-defined stoichiometry, arrangement of atoms and controlled crystal structure, are a promising alternative to expensive noble metal catalysts. In this paper, the catalytic properties of Al-13.5 at.% Cr and Al-13.5 at.% V alloys, corresponding to the quasicrystalline approximants Al45Cr7 and Al45V7, were investigated for the first time.The alloys in the form of fragmented brittle ribbons were produced by the melt-spinning. The microstructure of the ribbons, both in the as-spun state and after heat treatment (100 h at 600 °C), was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. In the as-spun state, the ribbons showed a multiphase microstructure. In addition to the Al45Cr7 phase in the Al-Cr alloy and the Al3V phase in the Al-V alloy, they also contained α(Al) solid solution and icosahedral quasicrystalline phases. After heat treatment, the alloys became almost single phase, consisting mainly of stable monoclinic phases: Al45Cr7 or Al45V7. The catalytic performance of the phenylacetylene hydrogenation reaction was tested on as-spun and heat-treated alloys that had previously been pulverized and sieved to select a powder fraction of less than 32 µm. All the tested materials show high substrate conversion, above 80% after 1 h reaction, along with high activity rate. The homogenized powders demonstrated a slightly better properties in relation to as-spun materials. These results confirm the potential of intermetallic catalysts, including the tested alloys, in hydrogenation reactions and verify the possibility of using the metallurgical method to obtain catalytically active materials.Graphical abstract

Liquid-Phase Partial Hydrogenation of Phenylacetylene at Ambient Conditions Catalyzed by Pd-Fe-O Nanoparticles Supported on Silica.

Catalysts with no hazardous or toxic components are required for the selective hydrogenation of acetylenic bonds in the synthesis of pharmaceuticals, vitamins, nutraceuticals, and fragrances. The present work demonstrates that a high selectivity to alkene can be reached over a Pd-Fe-O/SiO2 system prepared by the co-impregnation of a silica support with a solution of the metal precursors (NH4)3[Fe(C2O4)3] and [Pd(NH3)4]Cl2 followed by thermal treatment in hydrogen or in air at 400 °C. A DRIFT spectroscopic study of CO adsorption revealed large shifts in the position of the Pdn+-CO bands for this system, indicating the strong effect of Fen+ on the Pd electronic state, resulting in a decreased rate of double C=C bond hydrogenation and an increased selectivity of alkyne hydrogenation to alkene. The prepared catalysts consisted of mono- and bimetallic nanoparticles on an SiO2 carrier and exhibited a selectivity as high as that of the commonly used Lindlar catalyst (which contains such hazardous components as lead and barium), while the activity of the Fe-Pd-O/SiO2 catalyst was an order of magnitude higher. The hydrogenation of a triple bond over the proposed Pd-Fe catalyst opens the way to selective hydrogenation over nontoxic catalysts with a high yield and productivity. Taking into account a simple procedure of catalyst preparation, this direction provides a rationale for the large-scale implementation of these catalysts.

Selective hydrogenation of phenylacetylene over high-energy facets exposed nanotubular alumina supported palladium catalysts

High-energy facets exposed nanotubular alumina as well as conventional alumina supported Pd catalysts were synthesized and applied to the selective hydrogenation of phenylacetylene. Novel alumina supported catalyst presented higher selectivity at complete conversion of phenylacetylene. This could be related to the well dispersion of Pd and strong metal-support interaction, which are the consequences of the unique structural properties of the crystal plane regulated alumina. It helps create more active sites for hydrogenation meanwhile facilitates the desorption of alkene and thus suppresses the excess hydrogenation towards ethylbenzene.

Adjustment of the Single Atom/Nanoparticle Ratio in Pd/CNT Catalysts for Phenylacetylene Selective Hydrogenation

AbstractPd/C catalysts are widely used for hydrogenation reactions in the chemical industry. One of the reasons for their high activity is the ability of Pd nanoparticles (PdNP) to dissociate H2 and promote H‐spillover. Nevertheless, for selective hydrogenation unpromoted Pd/C catalysts show disappointing results. The use of supported Pd single atom (PdSA) catalysts permits to achieve high selectivity. However, PdSA show low activity because they have difficulty in activating H2. A cooperative catalysis between PdNP and PdSA operates for the hydrogenation of alkenes thanks to the H‐spillover, which makes it possible to obtain active isolated PdSA−H species. Here, we present experimental and computational results obtained for phenylacetylene hydrogenation on Pd/CNT catalysts showing different PdSA/PdNP ratios. Tuning this ratio allows doubling the activity while reaching high selectivity to styrene at high conversion. DFT calculations suggest that the first coordination sphere of PdSA has a pronounced effect on their reactivity.

PLATINUM – MESOPOROUS CARBON NITRIDE NANOCOMPOSITES: SYNTHESIS, CHARACTERIZATION AND CATALYTIC PERFORMANCE IN PHENYLACETYLENE HYDROGENATION

The platinum nanocomposites were synthesized by chemical reduction of H2PtCl6·6H2O in situ with a methanol—water mixture using mesoporous graphitic carbon nitride as a stabilizing matrix and a catalyst support. The textural, morphological, and optical properties of the obtained platinum – mesoporous carbon nitride composites (Pt/mpg-C3N4) were studied. Pt/mpg-C3N4 has been developed as an effective heterogeneous catalyst for the gas and liquid phase hydrogenation of phenylacetylene. An efficient and versatile approach to the modification of platinum with various organic solvents and ligands for the selective hydrogenation of phenylacetylene to styrene in a flow gas-phase process is pre-sented. The addition of pyridine, piperidine, or morpholine to the starting solution of phenylacetylene in hexane provides 95–100% conversion and 90–92% selectivity to styrene. A sharp increase in the selectivity to styrene without substantial changes in conversion is also observed when THF, ethanol, triethylamine, dioxane, or chloroform are used as diluents. The obtained Pt/mpg-C3N4 composites also demonstrated considerable catalytic activity in the selective hydrogenation of phenylacetylene to styrene at low temperatures in the liquid phase

Structure–Activity Relationship of Continuous Transformed Palladium Nanoclusters and Single Atoms for Selective Phenylacetylene Hydrogenation

Heterogeneous solid catalysts based on atomically dispersed Pd species are the most applicable catalysts in selective alkyne hydrogenation. However, the understanding of their structure–activity relationship remains ambiguous due to lack of structural analysis tools available and a unified synthetic system to obtain comparable Pd-based catalysts. Herein, we reported a convenient method to obtain Pd nanoclusters and Pd single atoms loaded on a nitrogen-doped carbon support (marked as Pd-NC@NC and Pd-SA@NC, respectively) in a uniform procedure and explored their structure–activity relationship in phenylacetylene hydrogenation. By the application of various kinds of characterization methods, we legibly illustrated the structures of Pd-NC@NC and Pd-SA@NC and found that Pd-NC@NC exhibited much higher mass activity than Pd-SA@NC (6.70 vs 0.33 mmol g–1 h–1) in phenylacetylene semi-hydrogenation. Theoretical calculations revealed that the different abilities of Pd nanoclusters and Pd1-N4 sites to adsorb reactants caused by steric hindrance were most likely to contribute to their different catalytic performances. This established structure–activity relationship provides guidelines for rationally designing metal catalysts for selective alkyne hydrogenation.

Enhanced Alkene Selectivity for Transfer Semihydrogenation of Alkynes over Electron-Deficient Pt Nanoparticles Encapsulated in Hollow Silica Nanospheres.

In this work, we report that Pt nanoparticles confined in hollow porous silica nanospheres (Pt@HPSNs) function as highly selective catalysts for the transfer hydrogenation of phenylacetylene to styrene with ammonia borane. Relative to the deep hydrogenation of phenylacetylene to ethylbenzene over the supported Pt/SiO2, Pt@HPSNs exhibit above 88% of styrene selectivity at nearly 100% of phenylacetylene conversions, and the high selectivity of Pt@HPSNs can be maintained even at high ammonia borane/phenylacetylene ratios and longer reaction time. The Pt 4f X-ray photoelectron spectrum of Pt@HPSNs shows a remarkable ∼1.5 eV shift to high binding energy, proving the nature of electron deficiency of such encapsulated Pt nanoparticles. Combined with extremely minor transfer hydrogenation of styrene to ethylbenzene when styrene as substrates, the enhanced styrene selectivity of Pt@HPSNs is ascribed to the electron deficiency of encapsulated Pt nanoparticles, which leads to the fast desorption of styrene and thus avoids deep hydrogenation.

Poly(ethylene imine) stabilized metal hydroxide nanoaggregates in reverse microemulsion system enabling synthesis of hollow silica catalytic nanoreactors as highly efficient semihydrogenation catalysts

In this work, we report a generic method of reverse microemulsion for syntheses of uniform and well-dispersed hollow porous silica nanospheres with metal (oxide) nanoparticles inside their cavities (MxOy@HPSNs or M@HPSNs), where the water phase consists of poly(ethylene imine) stabilized metal hydroxide nanoaggregates. During silica deposition, the mentioned nanoaggregates function as void templates as well as a platform to deliver catalytic functionality into voids. The subsequent calcination simultaneously gives hollow nanostructures and metal (oxide) nanoparticles inside central voids. The method applies to the metals that have hydroxide precipitates at basic conditions, and is suitable for most of catalytically active metals. As a demonstration, Pd@HPSNs illustrate high catalytic efficiency for selective hydrogenation of phenylacetylene at ambient H2 pressure, and the enhancement could be assigned to the effect of void confinement.

Continuous Flow Liquid‐Phase Semihydrogenation of Phenylacetylene over Pd Nanoparticles Supported on UiO‐66(Hf) Metal‐Organic Framework

AbstractCatalysis under continuous flow operation is industrially more relevant compared to reactions carried out in batch reactors. But catalysis with metal‐organic frameworks (MOFs) is largely restricted to batch reactions, especially in case of semi hydrogenation reactions. We anchored Pd nanoparticles (NPs) on robust UiO‐66(Hf) MOF to develop effective catalyst for semi hydrogenation of phenylacetylene into styrene. We investigated catalytic performance of Pd/UiO‐66(Hf) in a continuous‐flow liquid‐phase semi‐hydrogenation of phenylacetylene (PA). In this study, Pd/UiO‐66(Hf) catalyst exhibited good catalytic performance with a rare combination of high PA conversion (99.0 %) and high styrene selectivity (90.0 %). Additionally, Pd/UiO‐66(Hf) demonstrated lower deactivation rate in contrast to many reported materials to date. The higher stability of metal NPs over UiO‐66(Hf) aroused from the strong metal‐support interaction (between Brønsted acidic μ3‐OH of MOF and Pd). The Pd/UiO‐66(Hf) retained its catalytic activity even after four recycles.

Comparison of Catalytic Properties of the Easily Interconvertible, Water-Soluble [RuHCl(CO)(mtppms-Na)3] and [RuH(H2O)(CO)(mtppms-Na)3][BF4

The effect of the mobile interconversion of [RuHCl(CO)(mtppms-Na)3] 1, and [RuH(H2O)(CO)(mtppms-Na)3]+ 2, was studied in hydrogenation of phenylacetylene and cinnamaldehyde in aqueous–organic biphasic systems, as a function of the chloride concentration and the pH of the aqueous phase. Catalytic activity of the two complexes was also determined in homogeneous organic solvents without any additives. In the biphasic system, the rate of selective hydrogenation of phenylacetylene to styrene was strongly increased upon addition of NaCl, while the reaction of cinnamaldehyde slowed, with no change in product distribution. Both reactions responded with a rate decrease upon increasing the pH of the aqueous phase. It was concluded that hydrogenation of phenylacetylene was catalyzed by 1 with no chloride dissociation, while in the reduction of cinnamaldehyde, the aquo-complex 2 was the active catalytic species. Catalytic cycles were suggested to rationalize these findings.

Selective hydrogenation of phenylacetylene over TiO2 supported Ni2P nanoparticles under visible light irradiation

The introduction of P weakened the adsorption of styrene and enhanced the light absorption ability of Ni2P/TiO2, which improved photocatalytic activity and selectivity in the selective hydrogenation of phenylacetylene.

Pt nanoparticles confined in hollow silica nanoreactors as highly efficient catalysts for semihydrogenations of alkynes at atmospheric H2 pressure.

In this work, Pt nanoparticles encapsulated hollow porous silica nanoreactors (Pt@HPSNs) was synthesized in one-pot by a reverse microemulsion system, and they exhibit good catalytic efficiency and stability for semihydrogenations of alkynes. The key design concept is to form Pt hydroxide nanoparticles mixed poly(ethyleneimine) nano-aggregates in water droplets, which further functions as seeds for silica deposition and the void templates to form the central voids. The Pt@HPSNs illustrate a wide adaptability for semihydrogenations of a series of terminal alkynes to the corresponding alkenes at mild reaction conditions, and demonstrate high yields of styrene for semihydrogenation of phenylacetylene, showing good catalytic efficiency for hydrogenation of phenylacetylene to styrene at atmospheric H2 pressure. The enhanced catalytic performance of Pt@HPSNs are ascribed to their hollow porous nanostructures, where the confinement of Pt nanoparticles in voids increase the structural stability and the confinement effect may increase the collision of reactants and Pt, resulting in improved catalytic efficiency.

Etching suppression as a means to Pt dendritic ultrathin nanosheets by seeded growth.

2D ultrathin metal nanostructures are emerging materials displaying distinct physical and chemical properties compared to their analogues of different dimensionalities. Nanosheets of fcc metals are intriguing, as their crystal structure does not favour a 2D configuration. Thanks to their increased surface-to-volume ratios and the optimal exposure of low-coordinated sites, 2D metal nanostructures can be advantageously exploited in catalysis. Synthesis approaches to ultrathin nanosheets of pure platinum are scarce compared to other noble metals and to Pt-based alloys. Here, we present the selective synthesis of Pt ultrathin nansosheets by a simple seeded-growth method. The most crucial point in our approach is the selective synthesis of Pt seeds comprising planar defects, a main driving force for the 2D growth of metals with fcc structure. Defect engineering is employed here, not in order to disintegrate, but for conserving the defect comprising seeds. This is achieved by in situ elimination of the principal etching agent, chloride, which is present in the PtCl2 precursor. As a result of etching suppression, twinned nuclei, that are selectively formed during the early stage of nucleation, survive and grow to multipods comprising planar defects. Using the twinned multipods as seeds for the subsequent 2D overgrowth of Pt from Pt(acac)2 yields ultrathin dendritic nanosheets, in which the planar defects are conserved. Using phenylacetylene hydrogenation as a model reaction of selective hydrogenation, we compared the performance of Pt nanosheets to that of a commercial Pt/C catalyst. The Pt nanosheets show better stability and much higher selectivity to styrene than the commercial Pt/C catalyst for comparable activity.