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result(s) for
"Palladium catalysts"
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Synthesis of 6- or 8-Carboxamido Derivatives of Imidazo1,2-apyridines via a Heterogeneous Catalytic Aminocarbonylation Reaction
Imidazo[1,2-a]pyridines and especially their amide derivatives exhibit a wide range of favourable pharmacological properties. In this work, Pd-catalysed carbonylation was used for the first time for the introduction of the carboxamide moiety into positions 6 or 8. A recyclable Pd catalyst, with palladium immobilised on a supported ionic liquid phase decorated with pyridinium ions, was used efficiently for the conversion of 6- or 8-iodo derivatives to the products. In the case of 6-iodo derivatives, a competing mono- and double carbonylation could be observed in the reactions of aliphatic amines as nucleophiles, but under the proper choice of reaction conditions, good-to-excellent selectivities could be achieved towards either the corresponding amides or α-ketomides. The heterogeneous catalyst showed excellent recyclability and low Pd-leaching.
Journal Article
Effect of Support and Polymer Modifier on the Catalytic Performance of Supported Palladium Catalysts in Hydrogenation
In this study, we investigated the influence of polymer nature and support characteristics on the performance of Pd-based heterogeneous catalysts. Catalysts were prepared via sequential adsorption of poly(4-vinylpyridine) (P4VP) or chitosan (CS) and palladium ions onto MgO and SBA-15 supports under ambient conditions. The resulting hybrid materials were characterized by IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). TEM analysis revealed that Pd nanoparticles with an average size of 2–3 nm were well-dispersed on P4VP/MgO, while larger and less uniformly distributed particles (8–10 nm) were observed on SBA-15-based systems. Catalytic tests in the hydrogenation of 2-propen-1-ol, phenylacetylene, and 2-hexyn-1-ol under mild conditions (40 °C, 1 atm H2, ethanol) demonstrated that both the support and polymer type significantly influence activity and selectivity. P4VP-modified catalysts outperformed CS-containing analogs in all reactions. MgO-based systems showed higher activity and selectivity in 2-propen-1-ol hydrogenation compared to SBA-15-based catalysts. The 1%Pd–P4VP/MgO catalyst exhibited the best performance, with a reaction rate of 5.2 × 10−6 mol/s, 83.4% selectivity to propanol, and stable activity over 30 consecutive runs. In phenylacetylene and 2-hexyn-1-ol hydrogenation, all catalysts showed high selectivity to styrene (93–95%) and cis-2-hexen-1-ol (96–97%), respectively. The incorporation of P4VP polymer into the Pd/MgO catalyst leads to smaller and better-distributed palladium particles, resulting in enhanced catalytic activity and stability during hydrogenation reactions. These results confirm that the choice of polymer modifier and inorganic support must be tailored to the specific reaction, enabling the design of highly active and selective polymer-modified Pd catalysts for selective hydrogenation processes under mild conditions.
Journal Article
Unsymmetrical Strategy on α-Diimine Nickel and Palladium Mediated Ethylene (Co)Polymerizations
Among various catalyst design strategies used in the α-diimine nickel(II) and palladium(II) catalyst systems, the unsymmetrical strategy is an effective and widely utilized method. In this contribution, unsymmetrical nickel and palladium α-diimine catalysts (Ipty/iPr-Ni and Ipty/iPr-Pd) derived from the dibenzobarrelene backbone were constructed via the combination of pentiptycenyl and diisopropylphenyl substituents, and investigated toward ethylene (co)polymerization. Both of these catalysts were capable of polymerizing ethylene in a broad temperature range of 0–120 °C, in which Ipty/iPr-Ni could maintain activity in the level of 106 g mol−1 h−1 even at 120 °C. The branching densities of polyethylenes generated by both nickel and palladium catalysts could be modulated by the reaction temperature. Compared with symmetrical Ipty-Ni and iPr-Ni, Ipty/iPr-Ni exhibited the highest activity, the highest polymer molecular weight, and the lowest branching density. In addition, Ipty/iPr-Pd could produce copolymers of ethylene and methyl acrylate, with the polar monomer incorporating both on the main chain and the terminal of branches. Remarkably, the ratio of the in-chain and end-chain polar monomer incorporations could be modulated by varying the temperature.
Journal Article
Reusable and Self-Assembly Supramolecular Palladium Catalyst for C–C Coupling Reactions in Aqueous
A novel fluorescent supramolecular polymer (named N
3
T) has been synthesized resoundingly, which can effectively identify trace amounts of Pd
2+
in solution, and then a self-assembled supramolecular catalyst catalyst N
3
T-Pd was obtained. The N
3
T-Pd with spherical structure could be used for C–C coupling reactions in an eco-friendly aqueous medium. The catalyst was characterized by NMR, FT-IR, XPS, SEM and fluorescence spectra. The N
3
T-Pd has prominent stability and recyclability without any decrease of catalytic activity after least five cycles. Notably, the reaction degree of Pd
2+
with the supramolecular polymer can be conformed by the fluorescence intensity of the supramolecular polymer. With that, the N
3
T detection limit (LOD) of Pd
2+
was measured by fluorescent titration. Surprisingly, N
3
T can ultrasensitive detection of Pd
2+
, the limit of detection was 1.9 × 10
−7
M.
Graphical Abstract
The self-assembly supramolecular palladium catalyst N
3
T-Pd has been developed as a novel and efficient catalyst for ligand-free C–C cross-coupling reactions in aqueous at room temperature.
Journal Article
A Comprehensive Review on Barrelene-Derived α-Diimine Nickel and Palladium Olefin Polymerization Catalysts
Late transition metal olefin polymerization catalysts have received more attention in the field of catalytic olefin polymerization. Barrelene-based α-diimine nickel and palladium olefin polymerization catalysts are rising stars because of their backbone structure and catalytic properties. In this review, we present a comprehensive review of barrelene-derived α-diimine nickel and palladium olefin polymerization catalysts. α-Diimine nickel and palladium catalysts are introduced from two aspects: barrelene-derived backbone and aniline derivatives with different substituents. The relationship between catalyst structure and catalytic properties is also emphasized. This review attempts to provide an inspiration for the design of high-performance barrelene-based catalysts.
Journal Article
Polar-Functionalized Polyethylenes Enabled by Palladium-Catalyzed Copolymerization of Ethylene and Butadiene/Bio-Based Alcohol-Derived Monomers
Polar-functionalized polyolefins are high-value materials with improved properties. However, their feedstocks generally come from non-renewable fossil products; thus, it requires the development of renewable bio-based monomers to produce functionalized polyolefins. In this contribution, via the Pd-catalyzed telomerization of 1,3-butadiene and three types of bio-based alcohols (furfuryl alcohol, tetrahydrofurfuryl alcohol, and solketal), 2,7-octadienyl ether monomers including OC8-FUR, OC8-THF, and OC8-SOL were synthesized and characterized, respectively. The copolymerization of these monomers with ethylene catalyzed by phosphine–sulfonate palladium catalysts was further investigated. Microstructures of the resultant copolymers were analyzed by NMR and ATR-IR spectroscopy, revealing linear structures with incorporations of difunctionalized side chains bearing both allyl ether units and polar cyclic groups. Mechanical property studies exhibited better strain-at-break of these copolymers compared to the non-polar polyethylene, among which the copolymer E-FUR with the incorporation of 0.3 mol% displayed the highest strain-at-break and stress-at-break values of 940% and 35.9 MPa, respectively.
Journal Article
Partially Oxidized Pd/PdO/CC Catalyst for Hydrogen Production at Anodic and Cathodic in a Formaldehyde & Water Coelectrolysis System
Partial oxidation is a strategic method to optimize catalytic materials, particularly for multifunctional systems. Palladium (Pd), renowned for its dual activity in formaldehyde oxidation (FOR) and hydrogen evolution reactions (HER), is engineered here into a partially oxidized Pd/PdO catalyst. This design integrates metallic Pd's conductivity with PdO's oxidative properties, overcoming PdO's inherent limitations in adsorption and electron transfer. The Pd/PdO catalyst achieves a current density of 50 mA cm−2 at a low FOR potential of 0.63 V versus reversible hydrogen electrode, while HER performance remains robust even in formaldehyde‐containing electrolytes, maintaining unaltered onset potentials and kinetics. Hydrogen sources and mapped FOR‐driven hydrogen generation pathways through in situ differential electrochemical mass spectrometry and product analysis are conclusively identified. Density functional theory calculations demonstrate that Pd0–Pd2+ interfacial synergy enhances formaldehyde adsorption, while partial density of states (PDOS) analyzes reveal electronic modulation induced by partial oxidation, rationalizing the improved activity. This work not only elucidates the bifunctional mechanism of Pd/PdO but also highlights its potential in formaldehyde–water coelectrolysis systems. By bridging material design with atomic‐level mechanistic insights, the study establishes a universal framework for developing efficient, oxidation‐engineered catalysts for sustainable hydrogen production. This work presents a novel partially oxygen‐doped Pd/PdO/CC catalyst, enabling a dual‐hydrogen generation process at both the cathode and anode through formaldehyde–water coelectrolysis, significantly enhancing energy efficiency and sustainability.
Journal Article
Palladium Catalysts Supported in Microporous Phosphine Polymer Networks
A new set of microporous organic polymers (POPs) containing diphosphine derivatives synthesized by knitting via Friedel–Crafts has been attained. These amorphous three-dimensional materials have been prepared by utilizing diphosphines, 1,3,5-triphenylbenzene, and biphenyl as nucleophile aromatic groups, dimethoxymethane as the electrophilic linker, and FeCl3 as a promoting catalyst. These polymer networks display moderate thermal stability and high microporosity, boasting BET surface areas above 760 m2/g. They are capable of coordinating with palladium acetate, using the phosphine derivative as an anchoring center, and have proven to be highly efficient catalysts in Suzuki–Miyaura coupling reactions involving bromo- and chloroarenes under environmentally friendly (using water and ethanol as solvents) and aerobic conditions. These supported catalysts have achieved excellent turnover numbers (TON) and turnover frequencies (TOF), while maintaining good recyclability without significant loss of activity or Pd leaching after five consecutive reaction cycles.
Journal Article
Optimizing Pt/Pd Ratios for Enhanced Low-Temperature Catalytic Oxidation of CO and C.sub.3H.sub.6 on Al.sub.2O.sub.3 Support
This study investigated the impact of diverse Pt-Pd ratios on the activity and performance of DOC. A range of Pt-Pd catalysts with different Pt-Pd ratios and monometallic Pd and Pt catalysts on Al.sub.2O.sub.3 support were evaluated systematically. 0.5%wt PGM was used to avoid the high catalyst costs. The light-off temperatures and conversion efficiencies of CO, NO, and C.sub.3H.sub.6 were investigated under simulated diesel exhaust conditions. Several scientific techniques were used to characterize the catalysts, such as XRD, XPS, H.sub.2-TPR, and CO.sub.2 TPD. The results demonstrated that using bimetallic Pt-Pd catalysts on Al.sub.2O.sub.3 support significantly improved light-off temperatures and conversion efficiency than monometallic Pt and Pd catalysts. The order of light-off temperatures and CO and C.sub.3H.sub.6 conversions was: 0.4Pt0.1Pd < 0.3Pt0.2Pd < 0.2Pt0.3Pd < 0.1Pt0.4Pd < 0.5Pd < 0.5Pt. The synergistic enhancement of catalytic activity can be ascribed to the coexistence of active sites for Pt and Pd. 0.4Pt0.1Pd bimetallic catalyst showed best activity and stability in conversion of CO and C.sub.3H.sub.6 among all catalysts. As a result of the competitive adsorption of C.sub.3H.sub.6 and CO on Pt surface, which restricts the availability of adsorbed oxygen, the monometallic Pt/Al.sub.2O.sub.3 catalyst demonstrated high light-off temperatures and slow CO and C.sub.3H.sub.6 conversion rates. However, the Pd/Al.sub.2O.sub.3 catalyst showed very stable conversion efficiency, demonstrating metallic Pd's higher stability than Pt/Al.sub.2O.sub.3. Results demonstrated that Pt can be prudently incorporated into Pd-catalysts to improve their catalytic activity. It is noteworthy that the optimal Pt to Pd ratio plays a vital role in balancing activity and stability. The careful use of Pt-modified Pt-Pd bimetallic catalysts holds promise for achieving desired emissions conversion conditions. For instance, the 0.4Pt0.1Pd bimetallic catalysts exhibited superior activity and stability in the conversion of CO and C.sub.3H.sub.6 compared to other bimetallic catalysts. Pt loading above a specific amount may reduce activity due to Pt and Pd active site overlap and saturation.
Journal Article