Selective Hydrogenation Of Phenylacetylene Research Articles

Hierarchical N‐doped Carbon Nanosheets Anchored Bimetallic Oxides for Selective Hydrogenation of Phenylacetylene

Selective hydrogenation of alkynes to alkenes using a low‐cost non‐noble metal catalyst is urgently desirable but challenging because of their over‐hydrogenation to undesired alkanes. Herein, a series of hierarchical N‐doped carbon nanosheets anchored bimetallic oxides were successfully fabricated. The resultant composite catalysts had advantages associated with not only two‐dimensionality (2D) nanosheets with highly active sites and fast mass transfer, but also bimetallic oxides that dissociate and transfer hydrogen with the assistance of the oxygen vacancies. Furthermore, the bimetallic oxides combined with the advantages of high activity of Ni and the selectivity regulation of Co. Benefiting from these advantages, the catalytic performance of CoNiO2‐ZnCo2O4/NC NSs can reach nearly full conversion with 92 % selectivity at moderate reaction conditions and can keep excellent selectivity even prolonging the reaction time to 12 h, outperforming CoNiO2‐ZnCo2O4/NC NPs, CoO‐ZnCo2O4/NC NSs, and the commercial Lindlar catalysts, which demonstrate the huge potential for selective hydrogenation applications.

Gas–Liquid Mass Transfer Intensification for Selective Alkyne Semi-Hydrogenation with an Advanced Elastic Catalytic Foam-Bed Reactor

The Elastic Catalytic Foam-bed Reactor (EcFR) technology was used to enhance a model catalytic hydrogenation reaction by improving gas–liquid mass transfer. This advanced technology is based on a column packed with a commercial elastomeric polyurethane open-cell foam, which also acts as a catalyst support. A simple and efficient crankshaft-inspired system applied in situ compression/relaxation movements to the foam bed. For the first time, the catalytic support parameters (i.e., porosity, tortuosity, characteristic length, etc.) underwent cyclic and controlled changes over time. These dynamic cycles have made it possible to intensify the transfer of gas to liquid at a constant energy level. The application chosen was the selective hydrogenation of phenylacetylene to styrene in an alcoholic solution using a palladium-based catalyst under hydrogen bubble conditions. The conversion observed with this EcFR at 1 Hz as cycle frequency was compared with that observed with a conventional Fixed Catalytic Foam-bed Reactor (FcFR).

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 the 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.

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

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.

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.

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.

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.

Selective Hydrogenation of Phenylacetylene by Carbon Monoxide and Water

Selective Hydrogenation of Phenylacetylene by Carbon Monoxide and Water

Microstructure and catalytic properties of rapidly solidified Al-28.5 at% Fe and Al-28.5 at% Co alloys applied for selective hydrogenation of phenylacetylene

The Al 71.5 Fe 28.5 and Al 71.5 Co 28.5 (at.%) melt-spun alloys were examined in terms of microstructure evolution and catalytic response in the semihydrogenation reaction of phenylacetylene to styrene. In the as-spun state ribbons showed a single-phase composition. The Al 71.5 Co 28.5 alloy contained columnar grains of a metastable decagonal quasicrystal, which transformed into hexagonal Al 5 Co 2 and monoclinic Al 3 Co phases after heat treatment at 900 °C. The Al 71.5 Fe 28.5 ribbon had an ordered orthorhombic Al 5 Fe 2 phase structure in both the as-spun and annealed states. The pulverized ribbons revealed considerable catalytic activity for selective hydrogenation of phenylacetylene to styrene. The best results were achieved for the as-spun quasicrystalline Al 71.5 Co 28.5 alloy, showing a conversion rate of above 80% after 2 h reaction time. The selectivity to styrene was 60% for all catalysts. The tested powders retained their phase composition following liquid reaction therefore the proposed materials can be considered for catalytic use. • The Al5Co2 and Al5Fe2 ribbons were prepare by melt spinning methods • Decagonal quasicrystal in the Al5Co2 transforms into Al 5 Co 2 and Al 3 Co after annealing • Ordered orthorhombic Al 5 Fe 2 phase in both the as-spun and the annealed Al5Fe2 ribbons • Catalytic activity of the powdered ribbons in hydrogenation of phenylacetylene • The conversion rate exceeds 80% after 2 h reaction time for quasicrystalline Al5Co2

Synergistic trimetallic Ni–Cu–Sn catalysts for efficient selective hydrogenation of phenylacetylene

Selective hydrogenation of phenylacetylene is the most effective way to remove a small amount of phenylacetylene from styrene, but it is still a challenge to develop catalysts with high activity and selectivity. Herein, a series of non-precious bimetallic Ni3M/SiO2 (M = Zn, Sn, Cd, Fe, Co, Cu, or Mo) and trimetallic Ni3Cu–Sn/SiO2 catalysts were prepared and applied to selective hydrogenation of phenylacetylene. A trade-off between activity and selectivity was observed on Ni3M/SiO2, where Ni3Cu/SiO2 showed the best hydrogenation activity because of the hydrogen spillover effect of the Ni–Cu alloy, while Ni3Sn/SiO2 exhibited the highest selectivity to styrene due to the active-site isolation effect of the Ni–Sn alloy. Impressively, trimetallic Ni3Cu–Sn/SiO2 offered superior catalytic performance (94 % styrene selectivity at >99 % phenylacetylene conversion) as compared to bimetallic catalysts, owing to the synergistic effect among Ni, Cu, and Sn. In the case of Cu and Sn co-doping, the hydrogen spillover on the Ni–Cu alloy was deeply suppressed by Sn, which enabled an effective modification of the geometric and electronic structures of Ni to favor styrene desorption. The hydrogenation activity of Ni3CuSn0.3/SiO2 can be readily enhanced by increasing the metal loading and further improved by elevating the reaction temperature and pressure, but meanwhile the high selectivity is little affected. This work demonstrates a multi-metal synergistic strategy to break the activity–selectivity trade-off of Ni-based bimetallic catalysts in the selective hydrogenation of alkynes.

Selective hydrogenation of phenylacetylene over non-precious bimetallic Ni–Zn/SiO2 and Ni–Co/SiO2 catalysts prepared by glucose pyrolysis

Selective hydrogenation of phenylacetylene over non-precious bimetallic Ni–Zn/SiO2 and Ni–Co/SiO2 catalysts prepared by glucose pyrolysis

Highly Selective Semihydrogenation via a Wettability-Regulated Mass Transfer Process

Desired catalytic performance can be achieved by regulating the wettability of heterogeneous catalysts. Herein, by loading palladium nanoparticles within heterostructural gel supports, we achieved the wettability-controlled selective hydrogenation of phenylacetylene (PT) into styrene (ST) or ethylbenzene (ET) in aqueous media. During catalysis, the selectivity toward ST improved significantly as the catalyst hydrophilicity increased. Additionally, catalyst’s wettability had a negligible influence on its efficiency in the hydrogenation of PT. Mechanistic studies revealed that the catalyst’s wettability has less effect on its affinity for PT but markedly influences its affinity for ST. Hydrophobic catalysts favorably adsorbed semi-hydrogenated products (ST) and fully hydrogenated them to the corresponding ET. Contrastingly, hydrogenation of PT over hydrophilic catalysts remained in a semi-hydrogenated state owing to the quick desorption of ST from the catalyst surface, resulting from weak ST-catalyst interactions. We believe that the proposed strategy will be applicable in a wide range of heterogeneous catalysis reactions.

A Magnetically Separable Pd Single-Atom Catalyst for Efficient Selective Hydrogenation of Phenylacetylene.

Selective hydrogenation of alkynes to alkenes plays a crucial role in the synthesis of fine chemicals. However, how to achieve high selectivity and effective separation of the catalyst and substrate while obtaining high activity is the key for this reaction. In this work, a Pd single-atom catalyst is anchored to the shell of magnetic core-shell particles that consist of a Ni-nanoparticles core and a graphene sheets shell (Ni@G) for semi-hydrogenation of phenylacetylene, delivering 93% selectivity to styrene at full conversion with a robust turnover frequency of 7074 h-1 under mild reaction conditions (303 K, 2bar H2 ). Moreover, the catalyst can be recovered promptly from the liquid phase due to its magnetic separability, which makes it present good stability for enduring five cycles. Experimental and theoretical investigations reveal that H2 and substrates are activated by atomically dispersed Pd atoms and Ni@G hybrid support, respectively. The hydrogenation reaction occurs on the surface of Ni@G via hydrogen spillover from the metal to the support. Such a strategy opens an avenue for designing highly active, selective, and magnetically recyclable catalysts for selective hydrogenation in liquid reaction systems.

Crystal-Phase-Mediated Restructuring of Pt on TiO2 with Tunable Reactivity: Redispersion versus Reshaping

Restructuring of supported metal nanoparticles (NPs) (e.g., reshaping and redispersion) is of tremendous interest for the rational design of well-defined catalyst materials, but the underlying mechanism to tune their dynamic behaviors and thus reactivity is still unspecified. Here, we show a crystal-phase-mediated redispersion/reshaping of Pt NPs on TiO2, boosting opposite reactivities in hydrogenation/oxidation reactions. Utilizing a variety of state-of-the-art characterization methods, we unraveled that rutile TiO2 favors the reshaping of Pt NPs into two-dimensional planar geometry, whereas the anatase surface facilitates the redispersion of Pt NPs to single atoms (SAs) upon the same calcination procedure. Environmental transmission electron microscopy and density functional theory calculations were employed to directly visualize the dynamic transformation of Pt NPs and reveal the specific role of TiO2 supports in promoting the stability and diffusion of Pt SAs. As a result, the opposite reactivity was achieved by tuning their distinct restructuring behaviors. Thus, the redispersion of Pt on anatase TiO2 facilitates the selective hydrogenation of phenylacetylene with a high styrene yield of 21.22 × 10–2 s–1, whereas the reshaping on the rutile phase favors the combustion of methane with a turnover frequency as high as 3.11 × 10–2 s–1. Our results therefore open up an effective route for tuning the restructuring behavior of supported metal catalysts and designing catalysts with controlled catalytic structures and reactivities.

Synthesis of atomic platinum with high loading on metal-organic sulfide

Synthesis of ultrafine noble metal with sizes down to nanoscale and even atomic scale is of great significance for heterogeneous catalysis. However, the metal loading is usually kept below 2 wt% due to the aggregation tendency at higher metal contents. Herein, by mimicking the multicentered metal sulfur cluster of metalloenzyme, a bioinspired synthesis of isolated noble metal atoms on the metal-organic sulfide (MOS) framework was reported. The sulfur-rich framework featuring [Mo3S7Br6]2− cluster as the building block and dithiol as the linking node was constructed via chemical bonding and employed to support atomic metal species. Remarkably, highly dispersed platinum atoms with a loading amount as high as 18.5 wt% on the underlying sulfur-rich framework could be obtained after reduction. By increasing the number of benzene rings in the dithiol, the pore size and even the wettability of the MOS frameworks could be modulated. The general applicability of the synthesis could also be extended to the synthesis of atomic Pd. Furthermore, the Pt-loaded MOS could serve as the catalyst for selective hydrogenation of phenylacetylene to styrene in both organic solvent and pure water. Density function theory calculation demonstrated that the atomic Pt sites in the sulfur-rich coordination environment could activate H2 molecules and chemoselectively catalyze the semi-hydrogenation of phenylacetylene to styrene through moderately low energy barriers. The metalation of such a versatile MOS framework will shed light on the synthesis of bioinspired catalytic materials with well-defined structures for more diverse applications.

Promotion Effect of the X-Zeolite Host on Encapsulated Platinum Clusters for Selective Hydrogenation of Phenylacetylene to Styrene.

The microenvironment surrounding the metal clusters on a carrier produces a tremendous influence on its catalytic performance. In this work, the promotion effect of the zeolitic inner host on catalytic performance of encapsulated platinum nanoclusters is reported. In the reaction of phenylacetylene semihydrogenation to styrene, Pt@X-zeolite, where platinum nanoclusters are encapsulated into the inner microporosity of the X-zeolite, exhibits an ∼3.37 times increased turnover frequency and a much better selectivity of 87.6% in comparison to the referenced Pt/X-zeolite of 79.3% selectivity to styrene at the same reaction conditions, in which the platinum nanoclusters are located at the exterior of the zeolite. Meanwhile, the Pt@X-zeolite displays a higher stability after 10 cycles of the reaction. Through the detailed characteristics, the excellent performance of Pt@X-zeolite is mainly due to the promotion of the zeolitic framework on the encapsulated Pt clusters, resulting in "electron-deficient" Pt clusters, leading to a stronger interaction with the π* molecular orbitals of phenylacetylene and thus enhancing the activation and conversion of phenylacetylene. The zeolite cavity wrapped with encapsulated Pt clusters regulates the adsorption trend of phenylacetylene through the acetylene group on it, promotes the desorption of styrene, and strengthens its selectivity. Meanwhile, Pt@X-zeolite has an excellent stability through the zeolite framework, which protects the Pt species from being lost. This investigation reveals the importance of the zeolitic microenvironment on the catalytic performance of encapsulated metal species and deepens the cognition for this type of catalyst.