Hydrogenation Of Phenylacetylene Research Articles

Tuning the Pt species on Nb2O5 by support-induced modification in the photocatalytic transfer hydrogenation of phenylacetylene

Herein, we reported the tuning of dominant products in the photocatalytic hydrogen transfer reaction over Pt/Nb2O5 photocatalysts, using a support-induced modification strategy. In the photocatalytic conversion of phenylacetylene with ethanol as a probe reaction, the dominant product was styrene over Pt/2D Nb2O5 nanoplates; in contrast, H2 was the main product over the Pt/bulk Nb2O5. Compared to the metallic Pt species over bulk Nb2O5, the positively charged Pt (Ptδ+) species over 2D Nb2O5 nanoplates contributed to the reduction of phenylacetylene, which was revealed by CO adsorbed Fourier transform infrared spectra. Furthermore, the present Ptδ+ species were due to the formation of Ptδ+–O–Nb structure via oxygen transfer of 2D Nb2O5 nanoplates, which was verified by the results of X-ray photoelectron spectra and H2 temperature-programmed reduction. This work sheds light on the design and application of Nb-based catalysts in the transfer hydrogenation of organics in photocatalysis.

Immobilization of an Iridium(I)-NHC-Phosphine Catalyst for Hydrogenation Reactions under Batch and Flow Conditions

Na2[Ir(cod)(emim)(mtppts)] (1) with high catalytic activity in various organic- and aqueous-phase hydrogenation reactions was immobilized on several types of commercially available ion-exchange supports. The resulting heterogeneous catalyst was investigated in batch reactions and in an H-Cube flow reactor in the hydrogenation of phenylacetylene, diphenylacetylene, 1-hexyne, and benzylideneacetone. Under proper conditions, the catalyst was highly selective in the hydrogenation of alkynes to alkenes, and demonstrated excellent selectivity in C=C over C=O hydrogenation; furthermore, it displayed remarkable stability. Activity of 1 in hydrogenation of levulinic acid to γ-valerolactone was also assessed.

Fabrication of Superamphiphilic Carbon Using Lignosulfonate for Enhancing Selective Hydrogenation Reactions in Pickering Emulsions.

Superamphiphilic materials have great potential to enhance the mass transfer between phases in liquid-liquid catalysis due to their special affinities. Constructing superamphiphilic surfaces that possess superhydrophilic and superhydrophobic properties simultaneously has been a tough assignment. So, exploration of simple methods to prepare such materials using renewable and abundant feedstocks is highly desired. Here, we reported an effective strategy to construct superamphiphilic carbon directly from sodium lignosulfonate, which is a renewable resource from paper industry wastes. From the characterization of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) for superamphiphilic carbon, we found that element C was responsible for the hydrophobic nature and the existence of O and S endowed the carbon with hydrophilic characteristics. Further, micro/nanohierarchical pores were found beneficial for the superamphiphilicity of carbon. Meantime, in the selective hydrogenation of styrene, phenylacetylene, and cis-stilbene in liquid-liquid systems, conversion became double using superamphiphilic carbon compared with blank results, and the yields were three times more than those in blank experiments. The reasons were that superamphiphilic carbon induced the formation of Pickering emulsions and enriched the reactants around catalysts, as concluded by the characterization of confocal laser scanning microscopy and relating contrastive experiments. This work revealed a different route to obtain superamphiphilic carbon and provided a diverse perspective to promote Pickering emulsion catalysis by the superamphiphilicity of carbon.

Copper Single-Atom-Covered Pt Nanoparticles for Selective Hydrogenation of Phenylacetylene

The selective hydrogenation of alkynes to alkenes is very important for both industry and scientific investigation, and overhydrogenation of alkynes to alkanes is the biggest problem to be solved. Suppressing the catalytic hydrogenation of alkenes to alkanes and keeping the efficient conversion from alkynes to alkenes at the same time is a viable solution, but the slight difference in structure between alkynes and the corresponding alkenes causes great difficulty in realizing such a target. The Pt/C–Cu bimetallic catalysts are used to catalyze the selective hydrogenation of phenylacetylene (PA) to styrene (ST). High-resolution STEM and EXAFS results show that the prepared Pt/C–Cu catalysts are composed of copper single atoms and Pt nanoparticles. In particular, Pt/C–Cu is a catalyst in which copper single atoms cover the surface of Pt nanoparticles. The experimental results reveal that the selectivity of ST strongly depends on the coverage of Cu single atoms over Pt nanoparticles in Pt/C–Cu, so selective hydrogenation of PA is a structure-sensitive reaction. The selectivity of ST can reach 94.4% at a PA conversion of 100% in the selective hydrogenation of PA over Pt/C–0.5Cu, an optimized Pt–Cu bimetallic catalyst; after selective removal of PA in ST from 100 to 30 ppm over the same catalyst, the yield of ST reaches 99.97%. The chemisorption results of H2 and probe molecule ethene (C2H4) over the Pt–Cu/C catalysts reveal that Cu single atoms covering on the surface of Pt nanoparticles weaken the Pt–H and Pt–C2H4 interactions, so the catalytic hydrogenation of the carbon–carbon double bond over Pt/C–0.5Cu can be tremendously suppressed. The added Cu single atoms over Pt nanoparticles are not poisonous sites because they can also act as the active centers to activate hydrogen and the carbon–carbon double bond.

Homogeneous-like Alkyne Selective Hydrogenation Catalyzed by Cationic Nickel Confined in Zeolite

The selective hydrogenation of alkynes to their corresponding alkenes is an important type of organic transformation, which is currently accomplished by modified palladium catalysts. Herein, we rep...

Facile Redox Synthesis of Novel Bimetallic Crn+/Pd0 Nanoparticles Supported on SiO2 and TiO2 for Catalytic Selective Hydrogenation with Molecular Hydrogen

The bimetallic Crn+/Pd0 nanoparticles have been synthesized for the first time by a two-step redox method. The method includes the deposition of Pd0 nanoparticles on the surface of SiO2 and TiO2 carriers followed by the deposition of Crn+ on the surface of Pd0 nanoparticles using the redox procedures, which are based on the catalytic reduction of Crn+ with H2 in aqueous suspensions at ambient conditions. Transmission (TEM) and scanning (SEM) electron microscopy, X-ray photoelectron spectroscopy (XPS), Fourie-transformed infrared spectroscopy of adsorbed CO (FTIR-CO), and CO chemisorption studies were performed to characterize the morphology, nanoparticle size, element, and particle distribution, as well as the electronic state of deposited metals in the obtained catalysts. A decrease in nanoparticle size from 22 nm (Pd/SiO2) to 2–6 nm (Pd/TiO2) makes possible deposition of up to 1.1 wt.% Cr most likely as Cr3+. The deposition of CrOx species on the surface of Pd nanoparticles was confirmed using FTIR of adsorbed CO and the method of temperature-programmed reduction with hydrogen (TPR-H2). The intensive hydrogen consumption in the temperature ranges from −50 °C to 40 °C (Cr/Pd/SiO2) and from −90 °C to −40 °C (Cr/Pd/TiO2) was first observed for the supported Pd catalysts. The decrease in the temperature of β-PdHx decomposition indicates the strong interaction between the deposited Crn+ species and Pd0 nanoparticle after reduction with H2 at 500 °C. The novel Crn+/Pd/TiO2 catalysts demonstrated a considerably higher activity in selective hydrogenation of phenylacetylene than the Pd/TiO2 catalyst at ambient conditions.

Pd‐Nanocomposites Formed by Calcination of [Pd(2‐pymo)2]n Framework as Catalysts of Phenylacetylene Semihydrogenation in Water

AbstractThe novel Pd‐nanocomposites, fabricated via calcination of the MOF [Pd(2‐pymo)2]n (2‐pymo=2‐pyrimidinolate), were used for the first time in the transfer hydrogenation of phenylacetylene with NaBH4. The presence of Pd NPs or PdO in the studied materials was evidenced by XPRD, Raman spectroscopy, XPS and HR‐TEM. Under mild reaction conditions, in water as a solvent, Pd‐nanocomposites, Pd/CPYMO and PdO/Pd/CPYMO, provided better catalytic results than the pristine [Pd(2‐pymo)2]n, producing styrene with good selectivity. These two catalysts showed also good durability in subsequent reuses, while the productivity of PdO/CPYMO decreased after the second run.

Selective reduction of alkynes to alkenes with hydrogen or formic acid catalyzed by cis,mer-[IrH2Cl(mtppms)3

In this work we have found, that the water-soluble cis,mer-[IrH2Cl(mtppms)3] (mtppms = monosulfonated triphenylphosphine Na-salt) was an excellent catalyst for reduction of terminal alkynes by hydrogen transfer from aqueous HCOOH/HCOONa mixtures. The conversions strongly depended on the pH of the reaction mixtures, and the highest rate of phenylacetylene transfer hydrogenation was observed at pH 3. The same dihydrido-Ir(III) complex actively catalyzed also the hydrogenation of terminal alkynes under mild conditions (T = 50 °C; P(H2) = 2–10 bar). Importantly, both the hydrogenation and hydrogen transfer reductions afforded exclusively the corresponding alkenes as products. Phenylacetylene and its substituted derivatives reacted smoothly, while benzylic and aliphatic alkynes were less reactive or did not react at all. It was also found, that an excess of the mtppms ligand inhibited the reaction. This was rationalized by formation of cisz-[IrH2(mtppms)4]+ which was also confirmed with multinuclear NMR spectroscopy. On the basis of the experimental results, a joint mechanism was suggested for both the hydrogenation and transfer hydrogenation pathways. The mechanism of hydrogenation and transfer hydrogenation of phenylacetylene was also studied by DFT calculations, which revealed several possibilities for protonation of a vinyl intermediate as the crucial step in formation of the styrene product.

The effect of treatment with sodium carbonate and hydrogen on the activity and selectivity of polymeric Pd-containing catalysts for hydrogenation of acetylene compounds

Catalytic hydrogenation of the triple carbon-carbon bond of acetylene compounds is an important industrial process. High selectivity to the olefin compound should be provided in the process. This study considers the effect exerted by sodium carbonate treatment of the palladium catalysts containing super-cross-linked polystyrene (SPS) on their activity and selectivity in the hydrogenation of 2-methyl- 3-butin-2-ol and phenylacetylene. The effect of such treatment was shown to depend on the chosen palladium precursor and the type of polymeric support (non-functionalized SPS or that containing ternary amino groups). At atmospheric pressure of hydrogen and a temperature of 90 °C in a toluene medium, the 1%-Pd/SPS catalysts treated with Na2CO3 provided a 98 % selectivity in the hydrogenation of 2-methyl-3-butin-2-ol (at a 95 % conversion of the substrate), while selectivity in the hydrogenation of phenylacetylene reached 99.5 %.

Enhanced Catalytic Activity of PdNi Dilute Nanoalloy for Selective Phenylacetylene Hydrogenation

Coordination of identical metals has significant impact on catalytic activity and selectivity of heterogeneous catalyst. Here, we show that the selectivity for hydrogenation of Pd can be manipulated by altering the coordinate environment. PdNi/SiO2 dilute alloy nanocatalysts have been synthesized at room temperature, which show effectively the unparalleled catalytic performance (about 100% selectivity to styrene) for phenylacetylene hydrogenation at 30 °C with full conversion. Structural and surface analyses show that the improvement in dispersion of the Pd active sites and the changed electronic structure of Pd contribute the catalytic performance significantly. This work is an important step towards developing highly active hydrogenation catalysts by forming dilute alloys.

Formation of Active Centers of Nickel–Zinc Catalysts Deposited on the Nanodiamond for the Selective Hydrogenation of Phenylacetylene

A study is performed of bimetallic catalysts NiZn/ND with ratios Ni : Zn = 1 : 1 and 1 : 3 prepared by impregnation using detonation nanodiamond (ND) as a support. They were compared with monometallic Ni/ND and Zn/ND. It is shown by nitrogen adsorption/desorption, scanning and transmission electron microscopy that metal deposition does not affect the porous structure or morphology of a support. Coordination of metal precursors on a nanodiamond surface proceeds with the participation of functional groups, as is confirmed by a change in the electrokinetic charge of the surface. The reduction of metal precursors is studied by temperature-programmed reduction and in situ XAFS spectroscopy. In Ni-containing samples, two forms of Ni2+ are found that are bonded differently with the support. ZnO is not reduced in the samples upon treatment with hydrogen at temperatures up to 400°C. The fraction of reduced nickel is determined by analyzing XANES spectra. Virtually full reduction of nickel is observed in a catalyst with a Ni : Zn ratio of 1 : 1 after 4 h of in situ treatment with hydrogen inside a spectrometer cell at 400°C, but not at a Ni : Zn ratio of 1 : 3 under the same conditions. The highest selectivity of styrene formation in the reaction of phenylacetylene hydrogenation throughout the investigated range of temperatures (100–350°С) is ensured by NiZn/ND; NiZn3/ND is less active and selective, since ZnO closes the active nickel centers and prevents the adsorption of phenylacetylene.

Phosphorus and nitrogen-doped palladium nanomaterials support on coral-like carbon materials as the catalyst for semi-hydrogenation of phenylacetylene and mechanism study

In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by selective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nanoparticles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The results of N2 adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is 1307 m2g−1. In addition, the experimental exploration shows the intervention of P in carbon-nitrogen materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst can be reused several times without significant reduction in reaction activity.

Behavior of Pd‐supported catalysts in phenylacetylene hydrogenation: Effect of combined use of polyvinylpyrrolidone and NaOH for magnetic support modification

Recently, magnetic nanoparticles have attracted the attention as catalyst supports due to the possibility of magnetic separation, allowing for easy, fast, and clean recovery of the catalysts. A synthesis strategy of such supports plays an important role in improving the properties of the magnetic catalysts. Here, we proposed a simple and effective method to increase the activity and lifetime of the Pd magnetic catalyst. Polyvinylpyrrolidone‐maghemite nanoparticles were synthesized via one‐pot coprecipitation method using an excess of the NaOH. This was followed by adsorption of Pd2+ on the magnetic nanoparticles. The resulting catalyst showed activity (WCC = 4.0 × 10−6 mol s−1, WCC = 12.7 × 10−6 mol s−1) and selectivity (94%) in phenylacetylene hydrogenation. The catalyst was then magnetically recovered and reused 58 times. The activity of the catalyst increased significantly during the first three runs, changing the rate ratio of WCC to WCC from 1:3.2 to 1:1.6, and then decreased in the following runs. To understand the reason for this behavior, the catalyst was characterized, as well as catalytic studies were performed using similar catalysts for comparison. The results show that the NaOH adsorbed on magnetic support affects the size, stability, and catalytic properties of the Pd particles, and the effect of alkali is enhanced in the presence of the polymer.

Phenylacetylene semihydrogenation over a palladium pyrazolate hydrogen-bonded network

The palladium azolate/carboxylate network (Pd-dmpzc) catalyses the selective hydrogenation of phenylacetylene to styrene in water. Under optimised conditions, at a Pd:NaBH4 ratio of 1:100 at 40 °C, Pd-dmpzc provided much better results than Pd(OAc)2 or PdCl2(CH3CN)2. Analysis of the recovered catalyst revealed the presence of different Pd2+ species and Pd0 NPs which contributed in the catalytic reaction.

Highly Active and Stable Palladium Single-Atom Catalyst Achieved by a Thermal Atomization Strategy on an SBA-15 Molecular Sieve for Semi-Hydrogenation Reactions.

Single-atom catalysts (SACs) have great potential to revolutionize heterogeneous catalysis, enabling fast and direct construction of desired products. Given their notable promise, a general and scalable strategy to access these catalyst systems is highly desirable. Herein, we describe a straightforward and efficient thermal atomization strategy to create atomically dispersed palladium atoms anchored on a nitrogen-doped carbon shell over an SBA-15 support. Their presence was confirmed by spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurement. The nitrogen-containing carbon shells provide atomic diffusion sites for anchoring palladium atoms emitted from palladium nanoparticles. This catalyst showed exceptional efficiency in selective hydrogenation of phenylacetylene and other types of alkynes. Importantly, it showed excellent stability, recyclability, and sintering-resistant ability. This approach can be scaled up with comparable catalytic activity. We anticipate that this work may lay the foundation for rapid access to high-quality SACs that are amenable to large-scale production for industrial applications.

Liquid-phase hydrogenation of 1-hexene and phenylacetylene over multicomponent nickel skeleton catalysts

This paper presents the results of a study of the process of hydrogenation of 1-hexene in ethanol and phenylacetylene in a hexanewater suspension over multicomponent nickel skeleton catalysts It was demonstrated that the activity of multicomponent skeleton nickel catalysts is substantially dependent on the nature of the additives introduced into the bearing alloy. Introduction of Cu, Pb and Ta leads to an increase in activity (W=196-295cm3/min-gNi). The major mechanism of the effect of emulsion composition on the rate and selectivity of hydrogenation of phenylacetylene involves a change in the coefficient of distribution of substances between the solution and the surface of the skeleton nickel catalyst. It was also shown that the presence of water, which competes with unsaturated hydrocarbons during adsorption, adversely affects the process of purification from acetylenic hydrocarbons, as well as the stereo-regular polymerization of monomer. The research results of the kinetics and direction of the processes of hydrogenation of phenylacetylene suggest significant effect of the adsorption factor, including the ratio of free energies, concentrations and spatial orientation of the molecules of the mixture components, as well as the interaction of reacting substances and hydrogen with thecatalyst surface.

Supported Pt Nanoparticles on Mesoporous Titania for Selective Hydrogenation of Phenylacetylene.

Semi-hydrogenation of alkynes to alkenes is one of the most important industrial reactions. However, it remains technically challenging to obtain high alkene selectivity especially at a high alkyne conversion because of kinetically favorable over hydrogenation. In this contribution, we show that supported ultrasmall Pt nanoparticles (2.5 nm) on mesoporous TiO2 (Pt@mTiO2) remarkably improve catalytic performance toward semi-hydrogenation of phenylacetylene. Pt@mTiO2 is prepared by co-assembly of Pt and Ti precursors with silica colloidal templates via an evaporation-induced self-assembly process, followed by further calcination for thermal decomposition of Pt precursors and crystallization of mTiO2 simultaneously. As-resultant Pt@mTiO2 discloses a high hydrogenation activity of phenylacetylene, which is 2.5 times higher than that of commercial Pt/C. More interestingly, styrene selectivity over Pt@mTiO2 remains 100% in a wide phenylacetylene conversion window (20–75%). The styrene selectivity is >80% even at 100% phenylacetylene conversion while that of the commercial Pt/C is 0%. The remarkable styrene selectivity of the Pt@mTiO2 is derived from the weakened styrene adsorption strength on the atop Pt sites as observed by diffuse reflectance infrared Fourier transform spectroscopy with CO as a probe molecule (CO-DRIFTS). Our strategy provides a new avenue for promoting alkyne to alkene transformation in the kinetically unfavorable region through novel catalyst preparation.

Phenylacetylene hydrogenation coupled with benzyl alcohol dehydrogenation over Cu/CeO2: A consideration of Cu oxidation state

We have examined the effect of copper oxidation state in the continuous gas phase coupled phenylacetylene hydrogenation (to styrene) with benzyl alcohol dehydrogenation (to benzaldehyde) over Cu/CeO2. Analysis by H2-TPR, XPS, XRD and STEM-EDX analyses demonstrates the generation of a range of Cu oxidation states (Cu0 (13–77%), Cu+ (13–74%), Cu2+ (0–55%)). The stepwise formation of styrene and ethylbenzene was promoted in the stand-alone phenylacetylene hydrogenation. An increase in Cu0/Cu+ (from H2-TPR and XPS) enhanced H2 chemisorption and styrene TOF, but with low hydrogen utilisation efficiency. The formation of benzaldehyde and toluene was promoted in the stand-alone dehydrogenation of benzyl alcohol, where benzaldehyde selectivity and TOF correlate with the concentration of Cu0. Full hydrogen utilisation, exclusive benzaldehyde/styrene formation and a (3-fold) greater styrene TOF (to attain 100% yield) was achieved in the coupled process, where hydrogenation/dehydrogenation activity correlates with Cu+/Cu0. This opens new directions for sustainable “hydrogen free” hydrogenations over non-noble Cu catalysts.

2D and 3D Ruthenium Nanoparticle Covalent Assemblies for Phenyl Acetylene Hydrogenation

The bottom‐up covalent assembly of metallic nanoparticles (NP) represents one of the innovative tools in nanotechnology to build functional heterostructures, with the resulting assemblies showing superior collective properties over the individual NP for a broad range of applications. The ability to control the dimensionality of the assembly is one of the major challenges in designing and understanding these advanced materials. Here, two new organic linkers were used as building blocks in order to guide the organization of Ru NP into two‐ or three‐dimensional covalent assemblies. The use of a hexa‐adduct functionalized C60 leads to the formation of 3D networks of 2.2 nm Ru NP presenting an interparticle distance of 3.0 nm, and the use of a planar carboxylic acid triphenylene derivative allows the synthesis of 2D networks of 1.9 nm Ru NP with an interparticle distance of 3.1 nm. The Ru NP networks were found to be active catalysts for the selective hydrogenation of phenylacetylene, reaching good selectivity toward styrene. Overall, we demonstrated that catalyst performances are significantly affected by the dimensionality (2D vs. 3D) of the heterostructures, which can be rationalize based on confinement effects.

Pd−Zn Alloy Nanoparticles Encapsulated into Mesoporous Silica with Confinement Effect for Highly Selective Semi‐Hydrogenation of Phenylacetylene

AbstractIn the process of hydrogenation of phenylacetylene to styrene, it is a crucial step to improve the reaction selectivity of the target product styrene. Herein, we have designed the Pd−Zn alloy nanoparticles encapsulated into mesoporous silica with confinement effect (Pd−Zn@MS) for highly selective semi‐hydrogenation of phenylacetylene via annealing the Pd NPs@ZIF‐8 in reducing atmosphere. The as‐obtained Pd−Zn@MS achieved up to the 95 % of conversion rate and 92 % of selectivity, because the mesoporous silica exhibits a steric hindrance effect for the reactant molecular size, and the Pd−Zn alloy nanoparticles shows the high selectivity for the target product styrene. DFT calculations demonstrates that the PdZn alloy nanoparticles can reduce significantly the desorption energy barrier of styrene from 1.72 eV to 0.95 eV, compared with the Pd nanoparticles. Meanwhile the mesoporous silica in the outer layer greatly guarantees the stability of the catalytic performance of the catalyst, and the catalytic performance did not drop after the five‐cycle test. This work provides a new idea for the selective hydrogenation of phenylacetylene and the process of limited‐area catalysis.