Semihydrogenation Of Phenylacetylene Research Articles

Interfacial Electronic Effects in Co@N-Doped Carbon Shells Heterojunction Catalyst for Semi-Hydrogenation of Phenylacetylene.

Metal-supported catalyst with high activity and relatively simple preparation method is given priority to industrial production. In this work, this study reported an easily accessible synthesis strategy to prepare Mott-Schottky-type N-doped carbon encapsulated metallic Co (Co@Np+gC) catalyst by high-temperature pyrolysis method in which carbon nitride (g-C3N4) and dopamine were used as support and nitrogen source. The prepared Co@Np+gC presented a Mott-Schottky effect; that is, a strong electronic interaction of metallic Co and N-doped carbon shell was constructed to lead to the generation of Mott-Schottky contact. The metallic Co, due to high work function as compared to that of N-doped carbon, transferred electrons to the N-doped outer shell, forming a new contact interface. In this interface area, the positive and negative charges were redistributed, and the catalytic hydrogenation mainly occurred in the area of active charges. The Co@Np+gC catalyst showed excellent catalytic activity in the hydrogenation of phenylacetylene to styrene, and the selectivity of styrene reached 82.4%, much higher than those of reference catalysts. The reason for the promoted semi-hydrogenation of phenylacetylene was attributed to the electron transfer of metallic Co, as it was caused by N doping on carbon.

Mesoporous silica stabilized MOF nanoreactor for highly selective semi-hydrogenation of phenylacetylene via synergistic effect of Pd and Ru single site

Mesoporous silica stabilized MOF nanoreactor for highly selective semi-hydrogenation of phenylacetylene via synergistic effect of Pd and Ru single site

Catalytically active nano-porous cobalt-palladium alloys

The potential advantages of nano-alloys and particularly, nano-porous alloys, place them at the "spotlight" of heterogeneous catalysis. Nevertheless, controlling the precise compositions of these materials is still a synthetic challenge. Previous research introduced the fabrication of metals and alloys with a high nano-scale porosity and controllable compositions, via a hydrogen-mediated chemical reduction process of metal complex salts. We have used this procedure to obtain two magnetic nano-porous Co-Pd alloys, pure porous palladium and pure porous cobalt. Single crystal X-ray diffraction studies enabled structural determination of the two Co-Pd bi-complex salts that were used as precursors for these alloys. Powder X-ray diffraction studies determined the crystalline phases of the alloys and indicated the nanometric size of their crystallites. High-resolution scanning electron microscopy indicated that these alloys assemble as highly porous clusters of interconnected nano-crystallites. It also indicated that each alloy cluster preserves the micrometric morphologies of its salt precursor. Energy dispersive X-ray spectroscopy showed that the alloys exhibit uniform composition down to the micro-level, which preserved the Co/Pd ratio within the salts. Focused ion beam tomography enabled 3D structural representation of the alloys and metals. Geometrical analysis of the 3D reconstructed data determined 90% porosity and a specific surface area of ~100 m2/g for the alloys. In addition, the alloys showed improved catalytic activity in the semi-hydrogenation of phenylacetylene, compared to the pure metals and commercial Pd/C. Moreover, their magnetic properties enabled facile recovery at the end of the reaction. The yield for styrene in this reaction was increased using "design of experiments" (DOE), a method for optimization of reaction conditions. Furthermore, our experiments implied that a highly porous structure significantly improves the selectivity of styrene in the reaction. These results demonstrated the advantage of fabricating nano-porous alloys with uniform compositions that may exhibit special properties and serve as new and efficient catalysts.

CuPd alloy decorated SnNb2O6 nanosheets as a multifunctional photocatalyst for semihydrogenation of phenylacetylene under visible light

Bimetallic alloy of CuPd nanoclusters decorated SnNb2O6 nanosheet (CuPd/SN) as a multifunctional photocatalyst has been constructed successfully. Compared with SN, CuPd/SN achieves an excellent performance for semihydrogenation of phenylacetylene under visible light irradiation. Especially, CuPd/SN with the Cu:Pd molar ratio of 3:1 exhibits the highest catalytic conversion efficiency for phenylacetylene (99.6%) with high selectivity of phenylethylene (99.4%). In situ FTIR result reveals that SN could activate phenylacetylene via a C≡C → Nb π-bonded coordination which improves the selectivity of phenylethylene. Experiment results indicate that atom Pd in alloy is responsible for dissociation H2, while Cu represses the overhydrogenation. Electrochemical measurements suggest that CuPd alloy on SN surface could greatly minimize the recombination of photogenerated electron − hole pairs. The separated electrons further facilitate the production of active H. Hydrogen spillover would transfer active H to Nb site for phenylacetylene semihydrogenation. Finally, a synergetic catalytic mechanism is deeply discussed at molecule scale. This work would provide a deep insight for designing a multifunctional photocatalyst.

Surface Defect-Induced Site-Specific Dispersion of Pd Nanoclusters on TiO2 Nanoparticles for Semihydrogenation of Phenyl Acetylene

Currently, the wide application of heterogeneous noble metal catalysts is greatly limited due to their high cost and scarcity in global reserves. Thus, an effective strategy is to design highly eff...

Cover Feature: Pd‐Nanocomposites Formed by Calcination of [Pd(2‐pymo)2]n Framework as Catalysts of Phenylacetylene Semihydrogenation in Water (ChemCatChem 9/2021)

Cover Feature: Pd‐Nanocomposites Formed by Calcination of [Pd(2‐pymo)₂]_n Framework as Catalysts of Phenylacetylene Semihydrogenation in Water (ChemCatChem 9/2021)

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.

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.

Highly dispersed Ni2P clusters inlaid in micropore openings on mesoporous ZSM-5 zeolite and its catalytic performance in the phenylacetylene semi-hydrogenation

Preparation of Ni2P phase with cluster size and high stability is significant for enhancing its catalytic performance. Herein, Ni2P nanoclusters (<1nm) inlaid in micropore openings on mesoporous ZSM-5 zeolite (MZSM-5) was prepared through citric acid-assisted, two-step impregnation method under the reduction temperature of 400°C. The facilitation effect of the citric acid and support surface properties on the formation of Ni2P clusters was investigated. The formation of Ni(H2cit)+ complex promotes the dispersion of the Ni precursor on the zeolite surface. After calcination, the free Ni species interact stronger with the acidic hydroxyl groups on MZSM-5 than that with silanol on mesoporous TS-1(MTS-1), Silicalite-1 (MSilicalite-1) and SiO2, facilitating the formation of Ni2P nanoclusters on the MZSM-5 micropore openings after the calcined Ni catalyst was loaded with P species and followed by activation treatment. The obtained Ni2P clusters exhibit higher intrinsic activity (robs=1.50molkg−1s−1) than MTS-1, MSilicalite-1 and SiO2 supported Ni2P catalysts (0.80, 0.76, 0.40molkg−1s−1) in the semi-hydrogenation of phenylacetylene.

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.

Atomically dispersed Pd-Ru dual sites in an amorphous matrix towards efficient phenylacetylene semi-hydrogenation.

Optimizing the active sites to balance the conversion and selectivity of the target reaction has long been a challenging quest in developing noble metal-based catalysts. By dispersing Pd and Ru in an amorphous zirconium hydrogen phosphate matrix cross-linked by ionic inorganic oligomers, highly diluted noble metal (<0.2 mol%) can be utilized as dual single-atom sites in oxides for the semi-hydrogenation of phenylacetylene with optimized conversion and selectivity (both >90%) to styrene. In situ DRIFT-IR results suggested the fast generation of surface hydroxyl groups during the catalytic reaction, indicating the high efficiency of the single-atom sites to dissociate bound H2. This work provides an easily scaled-up method for the production of cost-effective single-atom catalysts extendable to various oxide matrices.

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.

Regulating Electronic Status of Platinum Nanoparticles by Metal–Organic Frameworks for Selective Catalysis

Selective hydrogenation of alkynes to alkenes remains challenging in the field of catalysis due to the ease of over-hydrogenated of alkynes to alkanes. Favorably, the incorporation of metal nanopar...

Nitrogen-fixing of ultrasmall Pd-based bimetallic nanoclusters on carbon supports

Synthesis of supported Pd-based bimetallic catalysts is of great importance in the heterogeneous catalysis field owing to their optimal geometric and electronic effects. Downsizing active metals to ultrasmall nanocluster (<2 nm), which is mandatory for maximizing the metal atom utilization, however remains as formidable synthesis challenges. Here, we present a general synthetic approach to sub-2 nm Pd-based bimetallic nanoclusters on porous nitrogen-doped carbon supports, in which the strong chemical interaction between metal and nitrogen largely suppresses the metal aggregation during the H2-reduction at 400–500 °C. Through the nitrogen-fixing strategy, we prepare 9 sub-2 nm Pd-based bimetallic nanocluster catalysts by conventional impregnation process. The prepared supported bimetallic Pd-Pb nanocluster catalyst exhibit a high turnover frequency of 1092 h−1 for the semihydrogenation of phenylacetylene under a mild condition (30 °C, 5 bar H2), along with a high selectivity of >93% to styrene, demonstrating the alloying and small-size effects in the bimetallic nanocluster catalysts.

Electronic Modulation of Pd-Based Bimetallic Catalysts with Sulfur-Doped Carbon Support for Phenylacetylene Semihydrogenation.

The semihydrogenation of phenylacetylene to styrene represents an important process for optimizing the polystyrene production and also a model reaction for the evaluation of selective hydrogenation catalysts. Although the alloying strategy and surface engineering for noble metal (particularly for Pd) catalysts can effectively inhibit the overhydrogenation of styrene, the selectivity of phenylacetylene semihydrogenation to styrene is generally below 95% near the full conversion. Here, we demonstrate the electronic modulation of Pd-based bimetallic nanocluster catalysts based on the strong metal-support interactions for improving the catalytic selectivity for phenylacetylene semihydrogenation. A series of Pd-M (M = Fe, Co, Ni, Cu, Ga) bimetallic nanoclusters of ∼2 nm are immobilized on mesoporous sulfur-doped carbon (meso_S-C) supports, which exhibit a high selectivity of >97% for the semihydrogenation of phenylacetylene to styrene. The strong interaction between metal and the meso_S-C supports enables the modulation of electronic structure of the bimetallic nanoparticles and thus leads to the selectivity enhancement for the phenylacetylene semihydrogenation.

In Situ Encapsulation of Pt Nanoparticles within Pure Silica TON Zeolites for Space-Confined Selective Hydrogenation.

Straightforward encapsulation of Pt clusters (∼2 nm) into the pure silica TON-type zeolite (ZSM-22) was reached in a dry gel conversion route, where the ionic liquid template was removed via the hydrocracking-calcination-reduction approach. The obtained Pt@ZSM-22 series possessed high crystallinity, large surface area, and ultrafine Pt clusters inside the zeolite crystals. They exhibited remarkable activity in the semi-hydrogenation of phenylacetylene into styrene; the lead sample with 0.2 wt % Pt loading afforded a large turnover number up to 117,787. The preferential high affinity of the pure silica ZSM-22-encapsulated Pt clusters toward the substrate phenylacetylene rather than the hydrogenated product was derived from the unique space-confinement effect of zeolite microchannels, which is responsible for such excellent performance.

Modification of Ni/Al2O3 catalyst with Pd nanoparticles for selective phenylacetylene semihydrodenation

NiPd/Al2O3 (4.9 wt% of Ni–0.1 wt% of Pd), Ni/Al2O3 (5 wt% of Ni) and Pd/Al2O3 (0.1 wt% of Pd) catalysts were tested in the liquid-phase semihydrogenation of phenylacetylene in batch- and flow-type reactors. Catalysts were characterized by temperature-programmed reduction, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Differences in the formation of palladium particles during deposition of metals on the surface of the alumina were revealed. Relatively large Pd particles observed in Pd/Al2O3 transformed to β-PdHx phase in a hydrogen atmosphere. When Pd and Ni are co-supported, no monometallic palladium particles were detected. Pd was apparently atomically distributed in the close vicinity of some NiO particles. As a result, there were two types of NiO particles in NiPd/Al2O3: NiO particles isolated from Pd species and those in close contact with atomically dispersed palladium. This distribution of metals provided the formation of activated hydrogen, which, in turn, led to an increase in the phenylacetylene conversion compared to monometallic Ni/Al2O3, while maintaining high selectivity of styrene formation. The close interaction of metals and their co-action in the hydrogenation of phenylacetylene was confirmed by the kinetic data obtained in a batch-type reactor. These data showed the difference in the reaction mechanisms on Ni/Al2O3 and NiPd/Al2O3.

Constructing PtI@COF for semi-hydrogenation reactions of phenylacetylene

The great efforts have been devoted to fabricate excellent hydrogenation catalysts owing to the broad applications in industrial fields. However, the preparation processes of traditional hydrogenation catalysts are often complicated. Herein, mono-valence PtI@COF was synthesized as a catalyst for semi-hydrogenation of phenylacetylene for the first time. The easily prepared SO3H-linked COF possesses a two-dimensional eclipsed layered-sheet structure, making its incorporation with metal ions feasible. The as-prepared PtI@COF composite exhibits excellent performance for semi-hydrogenation phenylacetylene with 93.5% conversion and 90.2% selectivity to styrene under mild reaction conditions (1 ​bar H2, 25 ​°C) within 20 ​min. It’s worth noting that the turnover frequency (TOF) value reaches at 3965 h-1, which outperforms most of recently reported excellent Pt-based catalysts for this reaction.

Graphdiyne-based Pd single-atom catalyst for semihydrogenation of alkynes to alkenes with high selectivity and conversion under mild conditions

Pd–GDY catalysts show an evident dependence on Pd species size in hydrogenation reaction. Specifically, Pds–GDY shows superior performance in semihydrogenation of phenylacetylene with much higher TOF of 6290 h−1 and selectivity of 99.3% at 100% conversion.

Unraveling the Role of Site Isolation and Support for Semihydrogenation of Phenylacetylene.

Intermetallic compounds (IMCs) composed of transition metals and post-transition metals function as superior heterogeneous catalysts in comparison to their monometallic and bimetallic alloy counterparts. Rendering IMCs in their nanomaterial iterations further enhances their efficiency. Herein, we demonstrate the role of PdIn as well-dispersed intermetallic nanoparticles (IMNPs) for the semihydrogenation of phenylacetylene selectively to styrene at ambient conditions. Higher selectivity of PdIn was explained with the help DOS calculations. We have explored the role of a few well-known silica-based supports such as SBA-15 and MCM-41, providing insight into how they affect catalysis. As an additional support we have explored previously reported JNC-1, a mesoporous carbon material obtained via a templated strategy using SBA-15. PdIn supported on SBA-15 and JNC-1 displayed the best dispersion, while also exhibiting the most catalytic activity due to the unique nature of the porous structure.