Palladium-based Catalysts Research Articles

Hydroconversion of paraffinic wax over platinum and palladium catalysts supported on silica–alumina

Two bifunctional catalysts consisting of platinum or palladium supported on amorphous silica–alumina were prepared and tested in hydrocracking/hydroisomerization of paraffinic wax. The performance of both noble metals was studied at the following reaction conditions: P=35bar; T=300–330°C; H2/wax=0.1wt/wt; WHSV=1–4h−1. The platinum sample was more active in hydrocracking of C22+ compounds and more selective to middle distillates. On the other hand, the palladium-based catalyst resulted in a higher isomerization degree of the products and lower amounts of methane and ethane. The higher production of light compounds over platinum is attributed to a monofunctional hydrogenolysis mechanism, in addition to the classical bifunctional route. Characterization studies showed that both catalysts had comparable metal and acid site distributions. These observations would indicate that the different catalyst performance is due to the different nature of platinum and palladium as hydrogenation/dehydrogenation function.

Selective hydrogenation of acetylene over TiO2-supported PdAg cluster: carbon species effect

The carbon species effects on the behavior of selective hydrogenation over the metal oxide supported palladium-based catalysts were Investigated.

Pd model catalysts: Effect of aging duration on lean redispersion

An automotive three-way catalyst (TWC) deteriorates as a function of temperature, time and aging environment. While much effort has gone into formulating durable exhaust catalysts, relatively little attention has been paid to controlling the aging environment on the vehicle with techniques currently in use to protect the catalyst and counteract the increasing demands for higher fuel economy (e.g., overfueling to reduce exhaust temperatures). New engine control methods that are designed to minimize aging may be possible that can reduce the extent of catalyst deactivation and provide a lean environment capable of redispersing many of the precious metal particles. To develop improved engine control methods, detailed experimental information is needed to map the response of the catalyst to different aging conditions. In this report, we examine palladium-based model powder catalysts on ceria–zirconia, which were exposed to three different exhaust compositions, lean-only, rich-only and redox, each at 700°C for three different durations, 20min, 2h and 16h. Residual catalyst activity and metal-support interaction were probed with Water Gas Shift (WGS) reaction and Oxygen Storage Capacity (OSC) measurements. The Pd metal particle size and dispersion were estimated by H2 chemisorption and XRD line broadening. Lean catalyst treatments at 550°C and 700°C were applied to determine the effect on Pd size and catalyst activity. An infrared study of CO adsorption onto the catalysts was used to identify whether Pd crystallite facets were covered by the support after exposure to the redox aging environment then again after the lean treatments were applied. The aging temperature and reducing gas environment significantly deteriorated catalytic activity through a combination of metal oxidation state effects and support interactions, while the aging duration was linked to the extent of Pd sintering reversibility through lean treatments. These insights provide a basis to develop engine control and aftertreatment design strategies to avoid severe aging modes and determine how often to actively intervene to regenerate the catalyst.

General Kinetic Modeling of the Selective Hydrogenation of 2-Methyl-3-butyn-2-ol over a Commercial Palladium-Based Catalyst

A general kinetic model has been developed to simulate the three-phase solvent-free hydrogenation of 2-methyl-3-butyn-2-ol (MBY) over a commercial palladium-based catalyst. A Langmuir–Hinshelwood mechanism with noncompetitive adsorption between hydrogen and the organic species is assumed. Gas–liquid mass-transfer resistance is included in the model. Experiments were carried out in a stirred slurry reactor to estimate the kinetic parameters. The proposed model is able to predict the concentration profiles of the species involved during MBY hydrogenation, at varying temperatures (313–353 K), pressures (3.0–10.0 bar), and catalyst loadings (0.075–0.175 wt %). The model predictions were successfully validated using additional experimental runs conducted under different operating conditions and at a lower initial concentration of MBY.

Pd model catalysts: Effect of aging environment and lean redispersion

The performance of automotive three-way catalysts (TWC) deteriorates with time, temperature and aging environment. Engine control methods are needed to minimize the extent of catalyst deactivation and provide an environment capable of partially redispersing noble metal catalyst particles. In this study, palladium-based model powder catalysts on ceria-zirconia or alumina supports were exposed to three different exhaust compositions, lean-only, rich-only and redox, each at 700°C for 16h. Catalyst activity was determined by CO oxidation with the water gas shift (WGS) reaction and oxygen storage capacity (OSC) measurements to probe the contact between the noble metal and support at a given state of catalyst deterioration. Lean catalyst treatments at 550°C and 700°C were applied to determine the effect on measured Pd size and catalyst activity. The lean-only gas environment was above the PdO decomposition condition, yet showed slightly deteriorated catalyst activity from the fresh state. The rich-only and redox gas environments significantly deteriorated catalytic activity through a combination of metal oxidation state effects and support/additive interactions, both with various degrees of reversibility depending on lean treatment time and temperature. The insight gained from this work could be used to develop engine control and after treatment design strategies to track (or infer) the aging process on the vehicle, avoid severe aging modes and actively intervene at various points to regenerate the catalyst.

Heterogeneous Fe3O4@chitosan-Schiff base Pd nanocatalyst: Fabrication, characterization and application as highly efficient and magnetically-recoverable catalyst for Suzuki–Miyaura and Heck–Mizoroki C–C coupling reactions

An environmentally friendly palladium-based catalyst supported on magnetite nanoparticles was successfully prepared. FT-IR, XRD, VSM, SEM, EDS and TGA studies have been used to characterize the nanocatalyst. The catalytic activity of the as-prepared catalyst was evaluated as a heterogeneous catalyst for the Suzuki–Miyaura carbon–carbon cross-coupling reaction of aryl halides and phenylboronic acid. Furthermore, it was found that the catalyst showed a high activity for the Mizoroki–Heck reaction of aryl halides and n-butyl acrylate. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture and recycled consecutive five runs without any significant loss in activity.

Multisource Synergistic Electrocatalytic Oxidation Effect of Strongly Coupled PdM (M = Sn, Pb)/N-doped Graphene Nanocomposite on Small Organic Molecules.

A series of palladium-based catalysts of metal alloying (Sn, Pb) and/or (N-doped) graphene support with regular enhanced electrocatalytic activity were investigated. The peak current density (118.05 mA cm−2) of PdSn/NG is higher than the sum current density (45.63 + 47.59 mA cm−2) of Pd/NG and PdSn/G. It reveals a synergistic electrocatalytic oxidation effect in PdSn/N-doped graphene Nanocomposite. Extend experiments show this multisource synergetic catalytic effect of metal alloying and N-doped graphene support in one catalyst on small organic molecule (methanol, ethanol and Ethylene glycol) oxidation is universal in PdM(M = Sn, Pb)/NG catalysts. Further, The high dispersion of small nanoparticles, the altered electron structure and Pd(0)/Pd(II) ratio of Pd in catalysts induced by strong coupled the metal alloying and N-doped graphene are responsible for the multisource synergistic catalytic effect in PdM(M = Sn, Pb) /NG catalysts. Finally, the catalytic durability and stability are also greatly improved.

Identification of by-products issued from the catalytic oxidation of toluene by chemical and biological methods

Benzene, toluene, ethylbenzene and xylenes (BTEX) are substances that are very commonly encountered in almost all sectors of the industry. Consequently, these molecules may be present in large amounts in industrial exhausts loaded with VOCs. An effective method for their elimination is catalytic oxidation, which is an economic and ecologic alternative to thermal oxidation. The aim of this work is to reveal the by-products issued from the total oxidation of toluene by palladium-based catalysts. The identification of these by-products was done using a chemical and toxicological approach. A toxicological validation of the developed catalysts was performed by coupling the catalytic system with an air–liquid interface (aLI) system, called Vitrocell®, to expose lung cells to catalytic exhausts.

ChemInform Abstract: Recent Developments in Palladium‐Based Bimetallic Catalysts

AbstractReview: recent developments in supported Pd bimetallic catalysts used for chemical synthesis, environmental protection, and renewable energy provision; 155 refs.

Enhanced CO2 Adsorption Affinity in a NbO-type MOF Constructed from a Low-Cost Diisophthalate Ligand with a Piperazine-Ring Bridge.

A metal-organic framework (NPC-6) with an NbO topology based on a piperazine ring-bridged diisophthalate ligand was synthesized and characterized. The incorporated piperazine group leads to an enhanced adsorption affinity for CO2 in NPC-6, in which the CO2 uptake is 4.83 mmol g(-1) at 293 K and 1 bar, ranking among the top values of CO2 uptake on MOF materials. At 0.15 bar and 293 K, the NPC-6 adsorbs 1.07 mmol g(-1) of CO2 , which is about 55.1 % higher than that of the analogue MOF NOTT-101 under the same conditions. The enhanced CO2 uptake combined with comparable uptakes for CH4 and N2 leads to much higher selectivities for CO2 /CH4 and CO2 /N2 gas mixtures on NPC-6 than on NOTT-101. Furthermore, an N-alkylation is used in the synthesis of the PDIA ligand, leading to a much lower cost compared with that in the synthesis of ligands in the NOTT series, as the former does not require a palladium-based catalyst and borate esters. Thus, we conclude that NPC-6 is a promising candidate for CO2 capture applications.

Pt, Pd, Au Binary and Ternary Catalysts for the Oxygen Reduction Reaction

The activation of oxygen in fuel cells and generally in electrocatalytic processes is of paramount importance to make such technologies marketable. For this reason it has been extensively studied for the last fifty years [1]. It is known that platinum-based binary alloys are excellent catalysts for the ORR (oxygen reduction reaction), which occurs at the cathode of PEMFCs (proton exchange membrane fuel cells). Beyond the lowering of the platinum loading in the electrode catalytic layers, alloyed Pt-based materials lead to the improvement of the catalytic activity [2], to the increase of the tolerance towards poisoning species and, for some authors, to durability enhancement of the catalysts under fuel cell working conditions [3]. PtxM1-x bimetallic materials (M = Co, Fe, Ni and Cr) have been extensively studied in order to correlate their catalytic activity and their electrochemical stability towards the ORR to their composition, crystallographic and electronic structures. Recent works have clearly shown that commercial Pt3Co/C nanoparticles were not totally stable during PEMFC operation even if they were more stable than monometallic Pt/C catalysts, they suffered compositional changes at the nanoscale. Other noble metals were also considered for the activation of the ORR in acidic medium, such as palladium and gold. Amongst pure metals, palladium leads to the highest activity towards the ORR, just after platinum. A review paper of Antolini [4] cited numerous publications explaining that palladium-based alloys or core-shell structures could lead to activities towards the ORR higher than those observed on pure palladium, and almost comparable to those recorded on pure platinum. Pd-Co and Pd-Fe are the most cited metallic alloys because they are the most active, in agreement with DFT (Density Functional Theory) calculations. Recently, PtPd alloys with very low Pt atomic ratio led to remarkable fuel cell electric performances [5]. Bimetallic PtxAu1-x catalysts have also led to excellent stability and activity under PEMFC working conditions, making this kind of materials a serious alternative candidate to platinum as cathode electrocatalysts in a PEMFC. In comparison, few studies have been carried out on the behavior of trimetallic catalysts towards the ORR. PtFeNi nanoparticles showed excellent electrocatalytic performances under PEMFC working conditions [6]. The research group of Manthiram studied Palladium-based trimetallic catalysts. They obtained activities towards the ORR comparable or even slightly higher to that of a Pt/C catalyst using Pd–Co–Mo/C and Pd–Co–Au/C materials. Although a few studies on trimetallic catalyst activity and stability is available in the literature, several trends could be drawn : (i) alloying platinum with a less noble metal seems to be beneficial for the ORR in terms of activity and tolerance, (ii) the interactions between two different noble metals such as Pt-Pd, Pt-Au and Au-Pd seems to enhance the durability and the catalytic activity towards the ORR with respect to pure metals and (iii) platinum seems unavoidable in order to achieve the best possible activity from the catalyst in an acidic environment. So in the present work, the synthesis and characterization of carbon supported Pt, Pd and Au based binary and ternary catalysts (PtxPdyAuz/C) are described as well as their systematic study (activity and selectivity) towards the ORR. The aim of this work is to allow defining a relevant catalyst formulation (composition and atomic ratio) for enhanced ORR performance. [1] C. Coutanceau, S. Baranton, “Advanced Processes in Catalytic Oxidation - Oxygen Activation in Fuel Cells and Electrocatalytic Processes”, in “From Laboratory Studies to Industrial Applications", D. Duprez and F. Cavani (Eds.), Imperial College Press, London, 2014. [2] M. T. Paffet, J. G. Beery, S. Gottesfeld, Oxygen reduction at Pt0.65Cr0.35, Pt0.2Cr0.8 and roughened platinum J. Electrochem. Soc. 135 (1988) 1431-1436. [3] X.Yu, S.Ye. Recent advances in activity and durability enhancement of Pt/C catalytic cathode in PEMFC: Part II: Degradation mechanism and durability enhancement of carbon supported platinum catalyst, J. Power Sources 172 (2007) 145-154. [4] E. Antolini, Palladium in fuel cell catalysis, Energy Environ. Sci. 2 (2009) 915-931. [5] M. Mougenot, A. Caillard, P. Brault, S. Baranton, C. Coutanceau, High Performance Plasma Sputtered PdPt Fuel Cell Electrodes with Ultra Low Loading, Int. J. hydrogen Energy 36 (2011) 5429-8434. [6] B. Fang, B. N. Wanjala, J. Yin, R. Loukrakpam, J. Luo, X. Hu, Jo. Last, C.-J. Zhong, Electrocatalytic performance of Pt-based trimetallic alloy nanoparticle catalysts in proton exchange membrane fuel cells, Int. J. Hydrogen Energy 37 (2011) 4627–4632 Acknowledgement: This work was made under the framework of the SMARTCat project funded by the European Commission under the FP7 Fuel Cells and Hydrogen Joint Technology Initiative grant agreement FP7-2012-JTI-FCH-325327.

Multi-Wall Carbon Nanotubes As Cathodes for Lithium-Air Batteries: Effect of Catalysts and Additives

Batteries with high specific energy densities have attracted a lot of attention due to their demand in electric vehicles (EVs). Due to the increase in demand for energy storage devices for applications such as load-levelling of electrical energy supply and demand [1], propulsion for electric vehicles, and microelectro-mechanical devices, the research for new classes of electrode materials that provide high energy, high power and cycle life longer than lithium-ion batteries is being motivated [2,3]. Lithium air batteries have high specific energy density and they can achieve four times higher energy density than the current lithium ion batteries [2, 3]. Lithium air batteries also have higher theoretical energy density than lithium ion batteries [4]. Catalysts have been shown to improve both the battery capacity and the recyclability of these batteries when used in cathodes. Several catalysts have been discovered for lithium air batteries. Debart et al. used several catalysts for lithium oxygen batteries with non-aqueous electrolyte. The electro-catalysts used by them included Pt, La0.8Sr0.2MnO3, Fe2O3, NiO, CuO, CoFe2O4. Co3O4 exhibited highest discharge capacity and best cycling performance. Later Debart et al. examined manganese oxides as catalysts for lithium oxygen batteries. Mn3O4, bulk Mn2O3, bulk α, β, λ, γ-MnO2, α-MnO2 nanowires and β-MnO2 nanowires were used as catalysts [6]. The air cathode with α-MnO2 as the catalyst showed the highest capacity of about 3000 mAh/g (carbon) Lu et al. reported ORR studies on polycrystalline metal catalysts of palladium, platinum, ruthenium, gold and glassy carbon surfaces in non-aqueous electrolyte [5]. In this study, we investigate various modes of loading palladium-based catalysts and their effect on the capacity and round-trip efficiency of lithium-air batteries. The aim of our study is to increase the first discharge capacity, improve the recyclability, increase capacity retention and improve the recyclability of the battery. The loading and morphology the catalyst-CNT cathodes were studied using transmission electron microscopy. Electrochemical testing using electrochemical impedance spectroscopy and charge-discharge cycling were also investigated. The cathode consisted of conductive carbon cloth coated with MWCNT or palladium inside MWCNT. Celgard 2040 was used as a separator. LiTFSi (Bis Trifluoromethane sulfonamide Lithium salt) in TEGDME (Tetraethyl glycol di-methyl ether) was used as electrolyte. The battery was assembled in the Swagelok cell. Figure 1 shows the assembly of the battery. Figure 2 shows the TEM images of palladium nanoparticles inside MWCNT. Figure 3 shows Pristine CNT with first cycle at a current rate of 200 mA/g showing a discharge capacity of 9300 mAh/g and a charge capacity of 8250 mAh/g. Figure 4 shows catalyst-loaded CNT with first cycle at a current rate of 200 mA/g showing a discharge capacity of 13800 mAh/g and a charge capacity of 3000 mAh/g.

ChemInform Abstract: How Low Does Iron Go? Chasing the Active Species in Fe‐Catalyzed Cross‐Coupling Reactions

AbstractReview: 51 refs.

Nitrous Oxide-dependent Iron-catalyzed Coupling Reactions of Grignard Reagents.

The formation of carbon-carbon bonds is one of the fundamental transformations in chemistry. In this regard the application of palladium-based catalysts has been extensively investigated during recent years, but nowadays research focuses on iron catalysis, due to sustainability, costs and toxicity issues; hence numerous examples for iron-catalyzed cross-coupling reactions have been established, based on the coupling of electrophiles (R(1)-X, X = halide) with nucleophiles (R(2)-MgX). Only a small number of protocols deals with the iron-catalyzed oxidative coupling of nucleophiles (R(1)-MgX + R(2)-MgX) with the aid of oxidants (1,2-dihaloethanes). However, some issues arise with these oxidants; hence more recently the potential of the industrial waste product nitrous oxide (N(2)O) was investigated, because the unproblematic side product N(2) is formed. Based on that, we demonstrate the catalytic potential of easily accessible iron complexes in the oxidative coupling of Grignard reagents. Importantly, nitrous oxide was essential to obtain yields up to >99% at mild conditions (e.g. 1 atm, ambient temperature) and low catalyst loadings (0.1 mol%) Excellent catalyst performance is realized with turnover numbers of up to 1000 and turnover frequencies of up to 12000 h(-1). Moreover, a good functional group tolerance is observed (e.g. amide, ester, nitrile, alkene, alkyne). Afterwards the reaction of different Grignard reagents revealed interesting results with respect to the selectivity of cross-coupling product formation.

Biphasic Palladium-Catalyzed Hydroesterification in a Polyol Phase: Selective Synthesis of Derived Monoesters.

The palladium-catalyzed hydroesterification reaction was performed with polyols and olefins in a liquid/liquid biphasic system composed of unreacted polyol on the one hand and apolar reaction products/organic solvents on the other hand. The palladium-based catalyst was immobilized in the polyol phase thanks to the use of cationic triarylphosphines possessing pendent protonated amino groups in the acidic reaction medium or to the sulfonated phosphine TPPTS (trisodium triphenylphosphine-3,3',3''-trisulfonate). Owing to the insolubility of the products in the catalytic phase, this approach allowed the synthesis of monoesters of polyols with high selectivities as well as the easy separation of the catalyst through simple decantation.

Pd Nanoparticles Immobilized on Fe3O4 @ Poly(ethylene glycol) Bridged Amine Functionalized Imidazolium Ionic Liquid: A Magnetically Separable Catalyst for Heck in Water

A palladium-based catalyst supported on novel Fe3O4 @ Poly(ethylene glycol) bridged amine functionalized imidazolium ionic liquid (Fe3O4@PEG–AIm–NH2–IL) was successfully prepared by a facile method. The catalyst was characterized by FT-IR, TEM, VSM, XRD, XPS and TGA-DSC, which showed high activity and stability for the Heck reaction in pure water. Furthermore, the catalyst could be recovered in a facile manner from the reaction mixture and recycled five times without any loss in activity. A novel magnetically separable Fe3O4@PEG–AIm–NH2–IL–Pd was designed and synthesized, which was used as outstanding palladium catalyst for the Heck reaction in pure water. The supported catalyst could be recycled and reused with the simple application of an external magnetic field, while keeping similar catalytic activity for five successive reactions.

Microwave-Assisted Solvothermal Synthesis of Pd-MnO2 Hybrid at Onion-like Carbons: Electrocatalytic Oxidation of Alcohols in Alkaline Media

The use of less toxic glycerol, (a non-flammable, volatile, and little-valued residue of biodiesel production), ethanol as well as ethylene glycol (EG) as fuel may be an interesting alternatives to methanol for Direct Alcohol Fuel Cell (DAFC) technology. The volumetric energy densities of glycerol, ethanol and EG are 5.80, 6.31 and 5.97 kW h L-1 compared to 5.81 kW h L-1for methanol makes them good fuel cell candidates [1-2]. The secret to the efficient electrocatalysis of alcohols is the use of efficient nanocatalyst. Palladium-based catalysts have emerged as the most viable electrocatalysts for alcohol in alkaline electrolytes. To harness the great catalytic potential offered by Pd, and to reduce cost, Pd-based alloys supported on different carbon supports are constantly used in direct alcohol fuel cells (DAFCs). In this work, palladium-manganese oxide nanoparticles supported on carbon nano onions (Pd-MnO2/OLC) were synthesized using the microwave-assisted solvothermal technique. Palladium-manganese oxide nanoparticles supported on Vulcan carbon (Pd@MnO2/XC–72) were also synthesized using the same technique for comparison. The catalysts were characterized using XRD, XPS, FESEM and HRTEM techniques. Electroxidation of the alcohols was performed in 0.5 M alcohol / 0.5 M KOH via cyclic and linear sweep voltammetry, chronoamperometric and elelctrochemical impedance spectroscopy. Results obtained show that the catalyst supported on OLC exhibited the highest current density and least charge transfer resistance relative to the catalyst supported on XC–72. Pd-MnO2/OLC gave the best result amongst the catalyst synthesized with respect to the current density, and electrochemical stability as well as exhibited the least charge transfer resistance in all the alcohols studied. For instance, the onset oxidation potential and current density of the glycerol oxidation process were -0.5386 V and 5.58mAcm-2, respectively. The implications of these results relative to methanol oxidation using the best catalyst system synthesized are discussed.

How Low Does Iron Go? Chasing the Active Species in Fe-Catalyzed Cross-Coupling Reactions

The catalytic cross-coupling reactions of organic halides or related substrates with organometallic nucleophiles form the cornerstone of many carbon-carbon bond-forming processes. While palladium-based catalysts typically mediate such reactions, there are increasing concerns about the long-term sustainability of palladium in synthesis. This is due to the high cost of palladium, coupled with its low natural abundance, environmentally deleterious extraction (∼6 g of metal are produced per ton of ore), toxicity, and competition for its use from the automotive and consumer electronics sectors. Therefore, there is a growing interest in replacing palladium-based catalysts with those incorporating more earth-abundant elements. With its low cost, high natural abundance, and low toxicity, iron makes a particularly appealing alternative, and accordingly, the development of iron-catalyzed cross-coupling is undergoing explosive growth. However, our understanding of the mechanisms that underpin the iron-based catalytic cycles is still very much in its infancy. Mechanistic insight into catalytic reactions is not only academically important but also allows us to maximize the efficiency of processes or even to develop entirely new transformations. Key to the development of robust mechanistic models for cross-coupling is knowing the lowest oxidation state in the cycle. Once this is established, we can explore subsequent redox processes and build the catalytic manifold. Until we know with confidence what the lowest oxidation state is, any cycles proposed are largely just guesswork. To date, Fe(-II), Fe(-I), Fe(0), Fe(I), and Fe(II) have been proposed as contenders for the lowest-oxidation-state species in the cycle in iron-catalyzed cross-coupling; the aim of this Account is to pull together the various pieces of evidence in support, or otherwise, of each of these suggestions in turn. There currently exists no direct evidence that oxidation states below Fe(0) are active in the catalytic cycle. Meanwhile, the reactivity required of the lowest-oxidation-state species has been observed with model compounds in higher oxidation states, implying that there is no need to invoke such low oxidation states. While subzero-valent complexes do indeed act as effective precatalysts, it is important to recognize that this tells us that they are efficiently converted to an active catalyst but says nothing about the oxidation states of the species in the catalytic cycle. Zero-valent heterogeneous iron nanoparticles can be formed under typical catalytic conditions, but there is no evidence to suggest that homogeneous Fe(0) complexes can be produced under comparable conditions. It seems likely that the zero-valent nanoparticles act as a reservoir for soluble higher-oxidation-state species. Fe(II) complexes can certainly be formed under catalytically relevant conditions, and when bulky nucleophilic coupling partners are exploited, potential intermediates can be isolated. However, the bulky reagents act as poor proxies for most nucleophiles used in cross-coupling, as they give Fe(II) organometallic intermediates that are kinetically stabilized with respect to reductive elimination. When more realistic substrates are exploited, reduction or disproportionation to Fe(I) is widely observed, and while it still has not been conclusively proved, this oxidation state currently represents a likely candidate for the lowest one active in many iron-catalyzed cross-coupling processes.

Electrooxidation of Phenol at Palladium-Based Catalyst Materials in Alkaline Solution

Electrooxidation of Phenol at Palladium-Based Catalyst Materials in Alkaline Solution

Magnetically recoverable nano Pd/Fe3O4/ZnO catalyst: preparation, characterization, and application for the synthesis of 2-oxazolines and benzoxazoles

A novel palladium-based catalysts supported on Fe3O4/ZnO nanoparticles have been prepared by a simple method. The catalyst was characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, atomic absorption spectrophotometry, FT-IR, and BET analysis. The catalyst afforded efficient synthesis of 2-oxazolines and benzoxazoles from aromatic nitriles under solvent-free conditions. The significant features of this method are short reaction times, good to high yields of the products, simple operation, solvent-free condition, non-toxicity, reusability of the catalyst without significant loss of catalytic activity, and using ultra small amount of Pd (0.004 g of catalyst contains 9.16 × 10−3 mmol Pd which was determined by ICP).