Pd-C Catalyst Research Articles

Improving Pd-C catalysts via heteroatom doping for the dehydrogenation of formic acid: a non-noble-metal modulation strategy

A non-noble-metal modulation strategy has been developed to adjust the electronic structure of Pd, resulting in enhancement of the catalytic performance for the dehydrogenation of formic acid.

Electrocatalytic activity enhancement of palladium-manganese nanosheet assembled nanobuds by tuning electronic structure

Adding another transition metals into Pd lattice is demonstrated as an effective strategy to improve Pd utilization while enhancing its catalytic activity toward formic acid electrooxidation through the generated ligand and strain effects. However, it is still very challenging to identify the contributions from the two effects on activity enhancement, which restrains the rational design of Pd-based alloy electrocatalysts. Herein, we reported the synthesis of PdMn nanosheet assembled nanobuds using a facile polymeric surfactant-free method with eliminated strain effect essentially, which were demonstrated as advanced catalysts in the aspect of much better catalytic activity and stability compared with the-state-of-the-art Pd-C catalyst. The catalytic enhancement mechanism should be attributed to the generated ligand effect which originates from the modulated electronic structure and consequent charge redistribution.

Efficient synthesis and antibacterial activity of N-(o-benzyloxy/hydroxyphenyl) benzohydroxamic acids

A modified one-pot two-step method has been developed to synthesize N-(o-benzyloxyphenyl) benzohydroxamic acids from o-benzyloxy nitrobenzene in good to excellent yields. The synthesized N-(o-benzyloxyphenyl) benzohydroxamic acids were subjected to benzyl deprotection using Pd-C catalyst under H2 gas atmosphere to afford corresponding N-(o-hydroxyphenyl) benzohydroxamic acids. All the synthesized N-(o-benzyloxy/ hydroxyphenyl) benzohydroxamic acids were characterized by 1H-, 13C NMR, FT-IR, UV-Vis., HRMS (ESI) and the structure of the compound 5d was further confirmed by analyzing its X-ray data. The synthesized novel N-(o-benzyloxy/ hydroxyphenyl) benzohydroxamic acids were screened for antibacterial activity against the bacterium Escherichia coli by the serial broth microdilution method using microplate alamar blue assay (MABA). The synthesized derivatives showed significant activity against E. coli.

Promotional effect of nickel addition on soot oxidation activity of Ce0.9Pr0.1O2 oxide catalysts

The present study investigates the promotional effect of Ni addition on soot oxidation activity of Ce0.9Pr0.1O2 oxide catalysts. A series of xNi-PDC (x= 0, 3, 5, 7, 10, 15, and 20 mol%) catalysts were synthesized by solution combustion synthesis method and characterized by XRD, Raman spectroscopy and TEM analysis. XRD and SAED patterns of the catalysts show cubic fluorite structure of ceria with an average crystallite size of 6–8 nm, and only 20Ni-PDC display NiO as a secondary phase. Raman spectra of xNi-PDC catalysts display an increase in oxygen vacancies. With a minimum addition of 10 mol% Ni to PDC, i.e., the 10Ni-PDC catalyst showed optimum soot oxidation activity (T50 = 360 °C) than compared to PDC and other Ni-PDC catalysts. Lattice strain and oxygen vacancies played a key descriptor role in showing better soot oxidation activity of the 10Ni-PDC catalyst. From the soot oxidation kinetic studies, the activation energy obtained by Ozawa plots for the 10Ni-PDC catalyst is 137 kJ/mol.

Antibacterial activity of curcuminoid derivatives resulted from hydrogenation reaction with Pd-C catalyst from turmeric (Curcuma longa) rhizomes extract

Turmeric (Curcuma longa) is one of the most commonly used plants for traditional medicine especially for antibacterial activity. However, because of its color, it is necessary to conduct a transformation reaction that can change the color of curcuminoid into colorless but still have antibacterial activity. The aim of this research was to analyze the antibacterial activity of tetrahydrocurcuminoid, derived from hydrogenation of curcuminoid isolated from turmeric extract towards Staphylococcus aureus and Fusobacterium nucleatum. Hydrogenation reaction was carried out using H2 gas with Pd-C catalyst to remove the conjugated double bond in curcuminoid to form tetrahydrocurcuminoid. Tetrahydrocurcuminoid then was purified by using silica gel column chromatography and characterized using UV-Vis and FTIR spectral data. Antibacterial activity of curcuminoid and tetrahydrocurcuminoid were tested against S. aureus and F. nucleatum using disc diffusion method. The antibacterial activity showed that tetrahydrocurcuminoid had a better antibacterial activity against S. aureus and F. nucleatum with average diameter of clear zone were 5.5 and 2.75 mm, respectively, than curcuminoid with 2 and 2.5 mm, respectively.

Reduction of curcuminoid extract from turmeric (Curcuma longa) rhizomes and its antibacterial activities

Curcuminoid is an active compound of turmeric rhizomes commonly used as yellow pigment. In some cases, the presence of pigment in beauty product is not desirable due to its aesthetics effect. In this study, yellow color removal of curcuminoid was carried out by two steps hydrogenation, i.e. using LiAlH4 followed by Pd-C catalyst to form dihydrocurcuminol and hexahydrocurcuminol derivatives, respectively. Dihydrocurcuminol derivatives had successfully synthesized by observing a wavelength shift from 419 to 428 nm in UV-Vis spectra and FTIR spectra also showed a reduction intensity of the carbonyl groups at 1600 cm−1. Moreover, hexahydrocurcuminol derivatives were identified at 283 nm in UV-Vis spectra while in FTIR spectra showed an absorption band of C-H sp3 at 2942 cm−1. Curcuminoid and hexahydrocurcuminol derivatives were evaluated for their antibacterial activities against Staphyloccocus aureus with 2 and 2.5 mm and Fusobacterium nucleatum with 4 and 2.75 mm inhibitory zone diameter, respectively. It can be concluded that curcuminoid and hexahydrocurcuminol derivatives had a weak antibacterial activity against both bacteria tests.

Pd/C catalyzed room-temperature, atmospheric pressure hydrogenation of furanic bio-oils from acidic ionic liquid catalyzed liquefaction of biomass in acetone

Furanic bio-oils were produced from liquefaction of corn cobs and switchgrass using 1-(3-propylsulfonic)-3-methylimidazolium chloride catalyst in acetone at 120 °C, 5 h. The biomass conversions to bio-oils for corn cobs and switchgrass were 43.8 ± 1.9 and 40.2 ± 1.4% (w/w) respectively. The bio-oils were then catalytically hydrogenated in water: methanol 3:1 (v/v) at room-temperature and atmospheric pressure using 5% Pd-C catalyst to give hydrogenated bio-oils and analyzed using GC–MS to identify the products. GC–MS analysis revealed that majority of the products in hydrogenated bio-oils is C4-C17 alcohols, ethers and furans. A total of 64 products were observed in GC–MS and 61 were identified with the use of mass spectroscopy. These products are arising from the partial reduction as well as deoxygenation of biomass derived furan aldehyde - acetone cross aldol products and acetone self condensation products. In addition, NMR analysis was used to quantify the effect of catalytic hydrogenation. 1H NMR spectra peak integration for the alkene-furan region (6.0–8.0 ppm) showed reductions of 19.0 to 1.8% and 19.1 to 2.6% due to the catalytic hydrogenation of bio-oils from corn cobs and switchgrass, confirming the effect of Pd-C catalyzed, 1 Atm., room temperature hydrogenation.

Pd-TiO2 Schottky heterojunction catalyst boost the electrocatalytic hydrodechlorination reaction

Electrocatalytic hydrodechlorination (EHDC) provides one promising solution to mitigate challenges from the water pollutions by persistent chlorinated organics. Palladium (Pd) has shown appealing properties as EHDC catalysts, while the low earth abundance has urged us to raise its activity and minimize usage. Herein, one novel semiconductor-metal Pd-TiO2 Schottky heterojunction catalyst was developed, which notably outperformed the conventional Pd-C catalyst in mass activity, dechlorination degree and energy selectivity towards EHDC of 2,4-dichlorophenol (2,4-DCP) in water. A combined experimental and DFT calculation study on mechanism revealed that the primary product phenol had a considerable negative effect on EHDC by competing the active sites with 2,4-DCP. The enhanced performance of Pd-TiO2 originated from the Schottky heterojunction-induced metal-support interactions, which optimized the Pd electronic structure and balanced the 2,4-DCP adsorption and phenol desorption on Pd. This study highlights one novel strategy to boost the metal performance in electrocatalytic hydrogenation reactions.

Gold-based carbon-supported bimetallic catalysts for energy storage and biomedical applications

In this study, the controlled synthesis of highly reactive gold palladium bimetallic nanostructured catalyst, using polyvinyl pyrrolidone stabiliser, has been proposed. In order to determine the morphology, biocompatibility and to explore the chemistry of the produced Au0.8Pd0.2-C samples, microscopic examinations, cell viability and Raman spectroscopy technique were performed. The XRD pattern displayed a well-defined fcc crystalline structure for the Au0.8Pd0.2-C and PdC catalysts. The presence of Au in Au0.8Pd0.2-C electrodes promotes a positive effect, which was confirmed by the appearance of a broad peak in the region of H2 adsorption/desorption, suggesting that the H2 adsorption/desorption processes on the surface of catalyst were favored. Standard MTT assay performed on the Au0.8Pd0.2-C samples displayed a decreased cellular response with respect to the control group; however, cell confluency throughout the tissue culture plate suggested biocompatibility of the given sample. Moreover, when the Au0.8Pd0.2-C catalyst was chemically tested by Raman spectroscopy, the presence of Au and Pd ions was confirmed.

Study on electrochemical properties of Pd-C and Pd-CNT catalysts

ABSTRACTThe catalytic and electrochemical properties of carbon-supported Pd catalysts (Pd-C, Pd-CNT), prepared by the technique of deposition reduction, are presented in this paper. Single-walled and multiwalled (nitrogen doped, carboxylated, noncarboxylated) carbon nanotubes with different specific surface areas as well as activated carbon (NORIT®) were used. Prepared catalysts were evaluated using cyclic voltammetry. Voltammetric characterization of the catalysts evaluated on the basis of nitrobenzene reduction reaction reveals increasing reactivity of catalysts with increasing Pd concentration from 1 up to 5% Pd and decreasing reactivity from 5 to 10% Pd. Influence of support properties on the reactivity of catalyst was also observed. Prepared catalysts were compared with four commercially produced catalysts.

Facile synthesis of uniform AuPd@Pd nanocrystals supported on three-dimensional porous N-doped reduced graphene oxide hydrogels as highly active catalyst for methanol oxidation reaction

Porous reduced graphene oxide hydrogels (RGOH), especially as supports for immobilizing metallic nanocrystals have attracted great attention in advanced nanomaterials, which have broad applications in catalysis, sensing and electric/optical devices. Herein, uniform core-shell AuPd@Pd nanocrystals supported on three-dimensional (3D) porous N-doped RGOH (AuPd@Pd NCs/N-RGOH) are facilely prepared by combining hydrothermal treatment with wet-chemical co-reduction. Ethylenediamine (EDA) is used as the nitrogen source and assembly agent for N-RGOH under hydrothermal conditions, and also as the structure-director for AuPd@Pd NCs during the wet-chemical co-reduction process. The nanocomposites display enhanced catalytic activity and stability for methanol oxidation reaction (MOR) in comparison with Pd NPs/N-RGOH and commercial Pd-C catalysts, owing to the unique structure and abundant nitrogen of N-RGOH, along with the synergistic effects between N-RGOH and AuPd@Pd NCs.

Multicomponent platinum-free nanoporous Pd-based alloy as an active and methanol-tolerant electrocatalyst for the oxygen reduction reaction

Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiAl (np-PdCuTiAl) electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiAl catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of ~3.7 nm. The half-wave potential of np PdCuTiAl is 0.873 V vs. RHE, more positive than those of PdC (0.756 V vs. RHE) and PtC (0.864 V vs. RHE) catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiAl in the presence of methanol, and this negative shift is much lower than those of the PdC (50 mV) and PtC (165 mV) catalysts. The enhanced ORR activity of np-PdCuTiAl has been further rationalized through density functional theory calculations.

Design and synthesis of palladium/graphitic carbon nitride/carbon black hybrids as high-performance catalysts for formic acid and methanol electrooxidation

Here we report a facile two-step method to synthesize high-performance palladium/graphitic carbon nitride/carbon black (Pd/g-C3N4/carbon black) hybrids for electrooxidizing formic acid and methanol. The coating of g-C3N4 on carbon black surface is realized by a low-temperature heating treatment, followed by the uniform deposition of palladium nanoparticles (Pd NPs) via a wet chemistry route. Owning to the significant synergistic effects of the individual components, the preferred Pd/g-C3N4/carbon black electrocatalyst exhibits exceptional forward peak current densities as high as 2155 and 1720 mA mg−1Pd for formic acid oxidation in acid media and methanol oxidation in alkaline media, respectively, far outperforming the commercial Pd-C catalyst. The catalyst also shows reliable stability, demonstrating that the newly-designed hybrids have great promise in constructing high-performance portable fuel cell systems.

Catalytic Oxidation and Reduction of Polycyclic Aromatic Hydrocarbons (PAHs) Present as Mixtures in Hydrothermal Media

The reactivity of fluorene, anthracene, and fluoranthene under oxidation and reduction conditions were investigated in this study. This project looks at catalytic and green approaches of converting PAHs to less toxic and/or less stable derivatives that are amenable to further degradation. Hydrothermal reactions have been performed at 300°C with pure H2O and Nafion-SiO2 catalyst for oxidation, and pure H2O, HCOOH, Pd-C, and Nafion-SiO2 catalysts for reductive hydrogenation. Time series has been performed for both the oxidation and hydrogenation systems. The products of the reaction were identified and quantified by the use of Gas Chromatography-Mass Spectrometry and the NIST Library. The reaction products include oxidized products of anthracene and fluorene; and hydrogenated derivatives of anthracene and fluoranthene. Fluoranthene did not undergo oxidation, and fluorene did not undergo hydrogenation under the conditions of this research.

A flow chemistry route to 2-phenyl-3-(1H-pyrrol-2-yl)propan-1-amines

The Knoevenagel condensation of pyrrole-2-carboxaldehyde (1) with a range of substituted benzyl nitriles (2a–e) afforded rapid access to a family of α,β-unsaturated nitriles (3a–e) in good yields (67–78%). Flow hydrogenation (ThalesNano H-cube™) at 60°C, 50bar H2 pressure, 1.0mL/min through a 10% Pd-C catalyst selectively, and quantitatively, hydrogenated the olefin double bond (4a–e). Use of a Raney Nickel catalyst at 70°C, 70bar H2 pressure and flow rates of 0.5–1.0mL/min afforded quantitative conversion into the corresponding saturated amines with the reduction of both the olefin and nitrile bonds (5a–e). The versatility of this approach was further exemplified by reaction of 5a and 5c with norcantharidin to afford acid amide norcantharidin analogues 7 and 8 as novel protein phosphatase 1 and 2A inhibitors.

Dehydroabietic acid

The title compound [systematic name: (1R,4aS,10aR)-7-iso­prop­yl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octa­hydro­phen­anthrene-1-carboxylic acid], C20H28O2, has been isolated from disproportionated rosin which is obtained by isomerizing gum rosin with a Pd-C catalyst.. Two crystallographically independent mol­ecules exist in the asymmetric unit. In each mol­ecule, there are three six-membered rings, which adopt planar, half-chair and chair conformations. The two cyclo­hexane rings form a trans ring junction with the two methyl groups in axial positions. The crystal structure is stabilized by inter­molecular O—H⋯O hydrogen bonds.

Pd-C/ammonium Formate: A Selective Catalyst for the Hydrogenation of Chalcones to Dihydrochalcones

Pd-C/ammonium formate is a highly efficient catalyst for the selective hydrogenation of chalcones to dihydrochalcones (DHCs). The reaction proceeds under mild conditions and the Pd-C catalyst is recovered without loss of activity.

Potential bile acid metabolites. 24. An efficient synthesis of carboxyl-linked glucosides and their chemical properties.

A facile and efficient synthesis of the carboxyl-linked glucosides of bile acids is described. Direct esterification of unprotected bile acids with 2,3,4,6-tetra-O-benzyl-D-glucopyranose in pyridine in the presence of 2-chloro-1,3,5-trinitrobenzene as a coupling agent afforded a mixture of the alpha- and beta-anomers (ca. 1:3) of the 1-O-acyl-D-glucoside benzyl ethers of bile acids, which was separated effectively on a C18 reversed-phase chromatography column (isolated yields of alpha- and beta-anomers are 4-9% and 12-19%, respectively). Subsequent hydrogenolysis of the alpha- and beta-acyl glucoside benzyl ethers on a 10% Pd-C catalyst in acetic acid/methanol/EtOAc (1:2:2, by vol) at 35 degrees C under atmospheric pressure gave the corresponding free esters in good yields (79-89%). Chemical specificities such as facile hydrolysis and transesterification of the acyl glucosides in various solvents were also discussed.

Catalytic Transfer Hydrogenation of Unsaturated Ketones and Imides via Ammonium Formate

Ammonium formate in acetic acid in presence of Pd-C catalyst efficiently converts open chain α,β-unsaturated ketones and cyclic enones to their saturated ketone analogues. The system converts enimides to saturated imides. An unsaturated non-conjugated cyclic dienone was also reduced by this system.

Synthesis of Poly[(1→6)-2,5-Anhydro-D-Glucitol] by Cationic Cyclopolymerization of 3,4-Di-O-Allyl-1,2:5,6-Dianhydro-D-Mannitol

Abstract The cyclopolymerization of 3,4-di-O-allyl-1,2:5,6-dianhydro-D-mannitol (1d) using BF3·OEt2 produced poly[(1→6)-3,4-di-O-allyl-2,5-anhydro-D-glucitol] (2d). For the polymerization in CH2Cl2 at -10°C, the maximum yield and Mn were obtained as 58.9% and 4890, respectively. The specific rotations ([α]22546) of the obtained polymers were +34.0° ∼ +38.8° (c=1.0 in CHCl3). The deallylation of polymer 2d in acetic acid/ethanol/water using the Pd-C catalyst perfectly proceeded to form poly[(1→6)-2,5-anhydro-D-glucitol] (3). The specific rotations ([α]22546) of the resulting polymers were +17.1° ∼ +18.9° (c=1.0 in H2O). Polymer 2d was soluble in chloroform and tetrahydrofuran, but insoluble in water, whereas polymer 3 was soluble in water but insoluble in chloroform and tetrahydrofuran.