Supported Palladium Nanoparticles Research Articles

Palladium Supported on Carbon Nanotubes Decorated Nickel Foam as the Catalytic Stirrer in Heterogeneous Hydrogenation of Polystyrene

Carbon nanotubes supported palladium (Pd/CNTs) catalyst displayed excellent activity toward hydrogenation of polystyrene (PS) to produce polycyclohexylethylene (PCHE) with added commercial values. However, its application is limited by the costly catalyst filtration process and energy-consuming elevated agitation speed. Herein, a dense, homogeneous and strongly attached layer of CNTs was decorated on nickel foams and employed as the catalyst support for palladium nanoparticles. Structured catalyst (Pd/CNTs@NF) was directly used as the catalyst stirrer in a rotating foam stirrer reactor (RFSR) for PS hydrogenation. Owing to the enhanced mass-transfer process, the hydrogenation degree reached 68.8%, which was 45.1% higher than that obtained in a slurry reactor using powdered Pd/CNTs catalyst under identical reaction conditions. Outstanding attachment strength of CNTs on the foam and catalytic stability in eight runs of recycling were also demonstrated. This work elucidates the promising feasibility of struc...

Novel palladium nanoparticles supported on β‐cyclodextrin@graphene oxide as magnetically recyclable catalyst for Suzuki–Miyaura cross‐coupling reaction with two different approaches in bio‐based solvents

A novel nanocatalyst was designed and prepared. Initially, the surface of magnetic graphene oxide (M‐GO) was modified using thionyl chloride, tris(hydroxymethyl)aminomethane and acryloyl chloride as linkers which provide reactive C═C bonds for the polymerization of vinylic monomers. Separately, β‐cyclodextrin (β‐CD) was treated with acryloyl chloride to provide a modified β‐CD. Then, in the presence methylenebisacrylamide as a cross‐linker, monomers of modified β‐CD and acrylamide were polymerized on the surface of the pre‐prepared M‐GO. Finally, palladium acetate and sodium borohydride were added to this composite to afford supported palladium nanoparticles. This fabricated nanocomposite was fully characterized using various techniques. The efficiency of this easily separable and reusable heterogeneous catalyst was successfully examined in Suzuki–Miyaura cross‐coupling reactions of aryl halides and boronic acid as well as in modified Suzuki–Miyaura cross‐coupling reactions of N‐acylsuccinimides and boronic acid in green media. The results showed that the nanocatalyst was efficient in coupling reactions for direct formation of the corresponding biphenyl as well as benzophenone derivatives in green media based on bio‐based solvents. In addition, the nanocatalyst was easily separable, using an external magnet, and could be reused several times without significant loss of activity under the optimum reaction conditions.

Cationic cellulose nanofibrils as a green support of palladium nanoparticles: catalyst evaluation in Suzuki reactions

Cationic cellulose nanofibrils (C-CNF) were used as a support for the growth and the immobilization of Pd NPs using PdCl2 as precursor. The ensuing Pd@C-CNF nanocomposite was tested as a catalyst for the Suzuki coupling reactions between aryl halides and arylboronic acid. Several characterization methods including TEM, HR-TEM, XRD, FT-IR, TGA and XPS were used to confirm the immobilization of Pd NPs onto the C-CNF surface and probe the surface composition after interaction with PdCl2. A quasi total coupling of phenyl boronic acid and 4-bromoacetophenone in DMF at 110 °C was found to occur after 4 h when only 0.02% of Pd@C-CNF of catalyst was used. Furthermore, the Pd@C-CNF could be easily recovered and reused for three consecutive Suzuki reaction cycles without significant loss of its catalytic activity and the loaded percent of palladium nanoparticles was maintained.

Remarkable effect of BaO on photocatalytic H2 evolution from water splitting via TiO2 (P25) supported palladium nanoparticles

Here we report a versatile strategy based on the use of BaO as an electron promoter to boost the photocatalytic activity of TiO2 based, Pd supported photocatalysts for hydrogen production from water splitting. Pd-BaO nanoparticles were deposited on the TiO2 surface by simple chemical reduction method using NaBH4 as reductant. The as-synthesized Pd-BaO/TiO2 photocatalysts showed a remarkably high performance in hydrogen production, approximately 29.6 mmol g−1h−1 using an ethanol-water mixture (5% ethanol and 95% water), which is two times higher than Pd/TiO2 photocatalyst, where the latter is already regarded as the most active metal based TiO2 photocatalysts for H2 production. This high hydrogen production efficiency was attributed to the inherent high catalytic activity of palladium nanoparticles and electronic promotional effect of BaO. The Ba (in the form of BaO) greatly enhanced the electron transfer from the semiconductor conduction band to Pd centers by raising the Fermi level of TiO2 during photo-irradiation. Most importantly, Pd is present exclusively in zero oxidation state, which is ideal for proton reduction in the as-prepared photocatalysts due to close proximity of highly electropositive BaO. The structural morphologies and mechanistic aspects of the Pd-BaO/TiO2 photocatalysts are addressed by using UV–Vis/DRS, XRD, TEM, and XPS characterization techniques.

Walnut Shell-Templated Ceria Nanoparticles: Green Synthesis, Characterization and Catalytic Application

Ceria (CeO2) nanoparticles (NPs) have been produced from cerium nitrate and walnut shell as a worthless agricultural waste by a thermal decomposition method followed by open air calcination. These NPs further were characterized using powder X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy, energy dispersive X-ray spectroscope and Fourier transform infrared spectroscopy. Moreover, particle sizes can be tuned by changing cerium source/biomass ratio. To test the catalytic activity of cerium NPs as a heterogeneous catalyst, we selected three-component synthesis of 3,4-dihydroquinoxalin-2-amine. Also, the efficiency of CeO2 NPs as a support for palladium NPs and subsequent use in aerobic oxidation of alcohols has been investigated. TEM image of a recovered catalyst indicates the formation of 12 nm sized palladium NPs within the cerium oxide NPs. The catalyst is quite effective for the oxidation of primary and secondary benzylic alcohols into their corresponding aldehydes and ketones under atmospheric pressure of air. Oxidation of secondary aliphatic alcohols is performed in oxygen atmosphere.

Recyclable cellulose nanocrystal supported Palladium nanoparticles as an efficient heterogeneous catalyst for the solvent‐free synthesis of coumarin derivatives via von Pechmann condensation

2‐Amino pyrimidine nanocellulose‐supported Palladium nanoparticles (CNC‐AMPD‐Pd) as a novel bio supported nanocatalyst was prepared and characterized by ICP‐AES, FT‐IR, XRD, SEM, TEM, TGA and EDX techniques. The nanocatalyst demonstrated outstanding performance in Pechmann condensation between different substituted phenols and ethyl acetoacetate to obtain coumarin derivatives in good to excellent yields. The catalyst is easily recycled and reused without loss of the catalytic activity. The combined merits of reusable catalyst and solvent‐free reaction conditions make the condensation with safe operation, no leaching of pd into environment, low pollution, rapid access to products and simple workup.

Facile synthesis of monodispersed Pd nanocatalysts decorated on graphene oxide for reduction of nitroaromatics in aqueous solution

We synthesized the reproducible heterogeneous catalyst of graphene oxide (GO)-supported palladium nanoparticles (NPs) via a simple and green process. The structure, morphology and physicochemical properties of the synthesized heterogeneous catalyst were characterized by the latest techniques such as high-resolution transmission electron microscopy (TEM), scanning TEM, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. The GO-supported Pd NPs (Pd/GO nanocatalyst) exhibited excellent catalytic activity for the reduction of nitroaromatics to aminoaromatics in aqueous sodium borohydride. The nitroaromatics were converted to corresponding aminoaromatics with high yields (up to 99%) using Pd/GO nanocatalyst in aqueous solution. The hybrid heterogeneous catalyst showed 83% of conversion after six cycles in the reduction of nitrobenzene to aminobenzene. These features ensured the high catalytic activity of the introduced graphene oxide supported Pd nanocatalysts.

Phosphosilicate nanosheets for supported palladium nanoparticles as a novel nanocatalyst

Abstract Inspired by the high accessibility and low diffusion limitations of fibrous silica nanoparticles (KCC‐1), fibrous phosphosilicate (FPS) was engineered using a microemulsion system. In this work, we report design and synthesis of high-surface-area FPS using tripolyphosphate (TPP) and tetraethyl orthosilicate (TEOS). The FPS nanocatalyst was thoroughly characterized by Fourier transform infrared spectra (FTIR), Powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDX), and N2 adsorption/desorption study. Considering the large ionic internal character, high mechanical and thermal stability as well as long-term colloidal stability, this system could be considered as perfect nanocatalyst by using the host–guest approach. Then palladium nanoparticles (Pd NPs) supported on fibrous phosphosilicat to the cycloaddition of CO2 to epoxides.

Design of Shape‐Palladium Nanoparticles Anchored on Titanium(IV) Metal‐Organic Framework: Highly Active Catalysts for Reduction of p‐Nitrophenol in Water

AbstractThe three‐dimensional microporous Ti‐based MOF material MIL‐125‐NH2 (MIL: Material of Institut Lavoisier) was successfully used as a support for palladium nanoparticles designed as catalysts for p‐nitrophenol hydrogenation. According to the mild and green synthetic approach, two catalysts of different nanoparticle morphology and different catalytic activity were obtained. Enhanced catalytic activity was found for a catalyst prepared using KBr as a capping agent, while Pd NPs of undefined shape synthesized without KBr were less active.

Synthesis of high surface area magnesia by using walnut shell as a template

Abstract In the present study, high surface area amorphous magnesia was synthesized using walnut shell as a template. This green, simple and useful synthetic protocol was based on the precipitation of magnesium nitrate on biomass in an aqueous phase, followed by calcination. Materials were characterized using X-ray diffraction, scanning electron microscopy (SEM) and N2 adsorption/desorption porosimetry, and the results exhibited high surface area for magnesium oxide. Furthermore, the pore size and surface area of these mesoporous materials can be adjusted by varying the biomass/magnesium nitrate ratio. In addition, magnesium oxide was studied as the support of palladium nanoparticles for the aerobic oxidation of alcohols. We have found out that the resulting Pd-loaded material acts as an effective catalytic system for the aerobic oxidation of benzylic and aliphatic alcohols. The catalyst can be recovered and reused three times without loss of activity. Also, to test the catalytic activity of magnesium oxides as a solid catalyst, we selected Meerwein-Ponndorf-Verley reduction of cyclohexanone with 2-propanol over different magnesium oxides.

Monodisperse palladium nanocatalysts for dehydrocoupling of dimethylamineborane

Over the last several decades, dimethylamine borane, which is one of the ammonia borane derivatives, has been attracting attention as one of the most effective solid hydrogen storage materials. Herein, the preparation and characterization of activated carbon supported palladium nanoparticles was reported as a highly efficient catalyst for dehydrogenation of dimethylamine borane under ambient conditions. The characterization of prepared nanomaterials was made by using some analytical methods such as XRD, XPS, TEM, HR-TEM. The prepared nanomaterials were observed in the range of 3.46–4.36 nm with an approximate mean diameter of 4 nm. The results of these analyses showed that the new palladium nanoparticles were colloidally stable and crystalline. The catalytic activity and durability of prepared nanomaterials were investigated for the dehydrogenation of dimethylamine borane. The one of the best TOF (100.3 h−1) value was obtained for the dehydrogenation of dimethylamine borane. The investigations showed that the palladium nanoparticles have very high catalytic activity and stability at room conditions.

Magnetic crosslinked copoly(ionic liquid) nanohydrogel supported palladium nanoparticles as efficient catalysts for the selective aerobic oxidation of alcohols

Nowadays it is still a great sustainable processes challenge to produce efficient, selective and easy magnetic recovery and recycling catalysts for oxidation of alcohols using air as the oxidant. In this work, a new magnetic nanohydrogel comprising [DABCO-allyl][Br] ionic liquid, allyl alcohol and N,N'-methylenebis(acrylamide) is used for stabilization of small and highly uniform palladium nanoparticles of 3–4 nm size MXCPILNHG@Pd. This material has been characterized by Fourier-transform infrared spectroscopy (FTIR), atomic adsorption spectroscopy (AAS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), SEM-Map, energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectra (XPS), vibrating-sample magnetometer (VSM) and dynamic light scattering (DLS). According to optimization of cross-linking degree and ratio of DABCO-IL, MXCPILNHG-2@Pd is found as a highly selective catalyst in oxidations of primary alcohols to the corresponding aldehydes in toluene and to acids in water. Furthermore, secondary alcohols were reacted efficiently to the corresponding ketones in both toluene and water. Catalyst is magnetically recovered and recycled for several times in both toluene and water and the reused catalysts are characterized by TEM and XPS.

Carbonylative Suzuki‐Miyaura Cross‐Coupling Over Pd NPs/Rice‐Husk Carbon‐Silica Solid Catalyst: Effect Of 1,4‐Dioxane Solvent

AbstractWith the aim of investigating the role of solvent in directing the product selectivity in carbonylative Suzuki‐Miyaura cross‐coupling (CSMC), Rice‐Husk (RH) derived carbon‐silica supported palladium nanoparticle (PdNPs/C‐SiO2) catalysts were prepared and characterized by various techniques. The structural and textural properties of these catalysts have been determined by XRD, BET, SEM, TEM, FT‐IR and XPS. In CSMC over Pd NPs/C‐SiO2catalysts solvents are playing a critical role in directing the product selectivity particularly with 1, 4‐dioxane solvent biaryl ketone alone formed from iodobenzene, carbon monoxide and phenylboronic acid, addressing the in‐situ formation of phenylboronate ester from 1, 4‐dioxane solvent and phenyl boronic acid and subsequent biaryl ketone formation with 100% selectivity and appealing catalytic activity ( Extreamly high TON= 3,61,650).

Facile Fabrication of Highly Active Magnetic Aminoclay Supported Palladium Nanoparticles for the Room Temperature Catalytic Reduction of Nitrophenol and Nitroanilines

Magnetically recyclable nanocatalysts with excellent performance are urgent need in heterogeneous catalysis, due to their magnetic nature, which allows for convenient and efficient separation with the help of an external magnetic field. In this research, we developed a simple and rapid method to fabricate a magnetic aminoclay (AC) based an AC@Fe3O4@Pd nanocatalyst by depositing palladium nanoparticles (Pd NPs) on the surface of the magnetic aminoclay nanocomposite. The microstructure and the magnetic properties of as-prepared AC@Fe3O4@Pd were tested using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM) analyses. The resultant AC@Fe3O4@Pd nanocatalyst with the magnetic Fe-based inner shell, catalytically activate the outer noble metal shell, which when combined with ultrafine Pd NPs, synergistically enhanced the catalytic activity and recyclability in organocatalysis. As the aminoclay displayed good water dispersibility, the nanocatalyst indicated satisfactory catalytic performance in the reaction of reducing nitrophenol and nitroanilines to the corresponding aminobenzene derivatives. Meanwhile, the AC@Fe3O4@Pd nanocatalyst exhibited excellent reusability, while still maintaining good activity after several catalytic cycles.

Pd/UiO-66(Hf): A highly efficient heterogeneous catalyst for the hydrogenation of 2,3,5-trimethylbenzoquinone

The conversion of 2,3,5-trimethylbenzoquinone (TMBQ) to 2,3,5-trimethylhydroquinone is regarded as one of the most important reactions for the production of vitamin E. Here, we report on a Hf-based metal–organic framework (MOF), UiO-66(Hf), with supported palladium nanoparticles as a highly active, selective, and recyclable catalyst for the direct hydrogenation of TMBQ with H2 under mild reaction conditions. The developed Pd/UiO-66(Hf) catalyst exhibited a marked increase in activity compared with its Pd/UiO-66(Zr) counterpart and conventional Pd/C catalysts. Its excellent catalytic performance is ascribed to the large number of acid sites in the UiO-66(Hf) framework, which promote hydrogenation.

Fe-ZSM-5 supported palladium nanoparticles as an efficient catalyst for toluene abatement

Catalytic combustion is considered as an efficient and economic technology to remove VOCs, and Al-ZSM-5 zeolite supported palladium catalysts (Pd/Al-ZSM-5) with good performances in this kind of reactions have been reported. In this work, it is found that Fe-ZSM-5 supported palladium catalyst (Pd/Fe-ZSM-5) exhibit higher catalytic activity in toluene combustion than the Pd/Al-ZSM-5, which is strongly related to more Pd0 active species and higher concentration of absorbed oxygen species of Pd/Fe-ZSM-5 than those of Pd/Al-ZSM-5. More importantly, Pd/Fe-ZSM-5 has a good catalyst life and water-resistant ability, which should be potentially significant for practical applications in environment protection.

Supported palladium nanoparticles as highly efficient catalysts for radical production: Support-dependent synergistic effects

Supported metallic palladium (Pd) acts as a real catalyst for peroxymonosulfate (PMS) activation to produce highly oxidizing species. However, the species produced are surface-bound in nature, and their use for pollutant degradation requires an inert supporting material to minimize the surface scavenging effect. In this study, we synthesized Pd nanoparticles (NPs) on different supporting materials (Al2O3, TiO2, SiO2, g-C3N4, C, and TiC), and compared their reactivity toward PMS activation for the first time. Experiments with 1,4-dioxane as a target pollutant showed that Pd/SiO2 had the highest reactivity of degrading 1,4-dioxane under acidic and neutral conditions, potentially due to the active interaction between SiO2 and PMS. However, Pd/Al2O3 had the greatest value of around 107% in the conversion of PMS to radicals. The ready oxidation of methanol to formaldehyde and degradation of 1,4-dioxane suggest that the activation of PMS by all the supported Pd NPs proceeded via a radical mechanism. These findings are critical to the development of efficient composite catalysts and the scientific understanding of observing different active species produced by Pd-catalyzed PMS.

Silica nanosphere supported palladium nanoparticles encapsulated with graphene: High-performance electrocatalysts for methanol oxidation reaction

A new type of silica nanosphere supported palladium nanoparticles encapsulated with graphene (denoted as Pd/SiO2@RGO) sandwich nanostructure electrocatalyst is prepared via a two-step reduction method for the first time. The characterization of electrocatalyst morphology and composition is discussed by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The TEM and XRD results show that palladium nanoparticles (Pd NPs) with a narrow size distribution are uniformly dispersed between silica sphere and the graphene layer. The ternary hybrid electrocatalyst exhibits high activity (1533 mA mg−1pd), superior operational durability and anti-poisoning ability (If/Ib = 3.9) compared with other controlled Pd catalysts. Moreover, it significantly reduces the peak potential (ca. 40 mv) and onset potential (ca. 80 mv) than commercial Pd/C, accounting for combination of the merits of SiO2 nanosphere support and the excellent electronic conductivity of RGO while overcoming their shortcomings. We provide an efficient way to fabricate a promising non-platinum anode catalyst for alkaline fuel cells.

Cover Feature: Nitrogen‐Doped Carbon Xerogels Supporting Palladium Nanoparticles for Selective Hydrogenation Reactions: The Role of Pyridine Nitrogen Species (ChemCatChem 6/2018)

Cover Feature: Nitrogen‐Doped Carbon Xerogels Supporting Palladium Nanoparticles for Selective Hydrogenation Reactions: The Role of Pyridine Nitrogen Species (ChemCatChem 6/2018)

Polydopamine supported palladium nanoparticles: Highly efficient catalysts in Suzuki cross-coupling and tandem Suzuki cross-coupling/nitroarene reductions under green reaction conditions

The application of an easily prepared and highly active polydopamine-supported Pd nanoparticles catalyst in Suzuki cross-couplings and tandem Suzuki cross-coupling/catalytic transfer hydrogenation sequences under green reaction conditions is described. In Suzuki cross-couplings between aryl bromides and arylboronic acids Pd concentrations down to ppm levels could be used, while reactions were completed within minutes. Heteroaryl bromides needed somewhat longer reaction times but could be transformed under otherwise identical conditions. The efficiency of the Suzuki cross-couplings made them compatible with the mechanistically different catalytic nitroarene transfer hydrogenations, yielding valuable biphenyl aniline products in a mild, one-pot tandem fashion. The influence of reaction time, temperature and Pd particle size on the catalyst efficiency and recyclability is also examined.