Pd Fe Catalysts Research Articles

PdFe Alloy-Fe5C2 interfaces for efficient CO2 hydrogenation to higher alcohols

Direct CO2 hydrogenation to higher alcohols (HA) is a promising route for high-value utilization of waste CO2, but developing active and stable catalysts remains a grand challenge. For this reaction, constructing multifunctional interfaces as active sites is required to fulfill controllable C-C coupling of alkyl and CO*/CHxO* species. Herein, we report a PdFe catalyst with abundant PdFe alloy-Fe5C2 interfaces via a PdFe alloy induced FeOx carbidization process, which can achieve HA yield of 86.5 mg gcat−1 h−1 with 26.5% selectivity at 300 ºC, 5 MPa, and 6000 mL gcat−1 h−1. The accelerated deactivation test unveils the PdFe catalyst exhibits better durability than the widely studied CuFe based catalysts against harsh conditions. Multiple in-situ characterization results unveil a synergetic mechanism for HA synthesis at the PdFe alloy-Fe5C2 interfaces, where PdFe alloy is responsible for CO formation and non-dissociative activation, while Fe5C2 phase promotes CO dissociation and chain propagation.

Liquid-Phase Partial Hydrogenation of Phenylacetylene at Ambient Conditions Catalyzed by Pd-Fe-O Nanoparticles Supported on Silica.

Catalysts with no hazardous or toxic components are required for the selective hydrogenation of acetylenic bonds in the synthesis of pharmaceuticals, vitamins, nutraceuticals, and fragrances. The present work demonstrates that a high selectivity to alkene can be reached over a Pd-Fe-O/SiO2 system prepared by the co-impregnation of a silica support with a solution of the metal precursors (NH4)3[Fe(C2O4)3] and [Pd(NH3)4]Cl2 followed by thermal treatment in hydrogen or in air at 400 °C. A DRIFT spectroscopic study of CO adsorption revealed large shifts in the position of the Pdn+-CO bands for this system, indicating the strong effect of Fen+ on the Pd electronic state, resulting in a decreased rate of double C=C bond hydrogenation and an increased selectivity of alkyne hydrogenation to alkene. The prepared catalysts consisted of mono- and bimetallic nanoparticles on an SiO2 carrier and exhibited a selectivity as high as that of the commonly used Lindlar catalyst (which contains such hazardous components as lead and barium), while the activity of the Fe-Pd-O/SiO2 catalyst was an order of magnitude higher. The hydrogenation of a triple bond over the proposed Pd-Fe catalyst opens the way to selective hydrogenation over nontoxic catalysts with a high yield and productivity. Taking into account a simple procedure of catalyst preparation, this direction provides a rationale for the large-scale implementation of these catalysts.

Tuning hydrogenation chemistry of Pd-based heterogeneous catalysts by introducing homogeneous-like ligands

Noble metals have been extensively employed in a variety of hydrotreating catalyst systems for their featured functionality of hydrogen activation but may also bring side reactions such as undesired deep hydrogenation. It is crucial to develop a viable approach to selectively inhibit side reactions while preserving beneficial functionalities. Herein, we present modifying Pd with alkenyl-type ligands that forms homogeneous-like Pd-alkene metallacycle structure on the heterogeneous Pd catalyst to achieve the selective hydrogenolysis and hydrogenation. Particularly, a doped alkenyl-type carbon ligand on Pd-Fe catalyst is demonstrated to donate electrons to Pd, creating an electron-rich environment that elongates the distance and weakens the electronic interaction between Pd and unsaturated C of the reactants/products to control the hydrogenation chemistry. Moreover, high H2 activation capability is maintained over Pd and the activated H is transferred to Fe to facilitate C-O bond cleavage or directly participate in the reaction on Pd. The modified Pd-Fe catalyst displays comparable C-O bond cleavage rate but much higher selectivity (>90%) than the bare Pd-Fe (<50%) in hydrotreating of diphenyl ether (DPE, modelling the strongest C-O linkage in lignin) and enhanced ethene selectivity (>90%) in acetylene hydrogenation. This work sheds light on the controlled synthesis of selective hydrotreating catalysts via mimicking homogeneous analogues.

Green Chemistry for the Transformation of Chlorinated Wastes: Catalytic Hydrodechlorination on Pd-Ni and Pd-Fe Bimetallic Catalysts Supported on SiO2

Monometallic catalysts based on Fe, Ni and Pd, as well as bimetallic catalysts based on Fe-Pd and based on Ni-Pd supported on silica, were synthesized using a sol-gel cogelation process. These catalysts were tested in chlorobenzene hydrodechlorination at low conversion to consider a differential reactor. In all samples, the cogelation method allowed very small metallic nanoparticles of 2-3 nm to be dispersed inside the silica matrix. Nevertheless, the presence of some large particles of pure Pd was noted. The catalysts had specific surface areas between 100 and 400 m2/g. In view of the catalytic results obtained, the Pd-Ni catalysts are less active than the monometallic Pd catalyst (<6% of conversion) except for catalysts with a low proportion of Ni (9% of conversion) and for reaction temperatures above 240 °C. In this series of catalysts, increasing the Ni content increases the activity but leads to an amplification of the catalyst deactivation phenomenon compared to Pd alone. On the other hand, Pd-Fe catalysts are more active with a double conversion value compared to a Pd monometallic catalyst (13% vs. 6%). The difference in the results obtained for each of the catalysts in the Pd-Fe series could be explained by the greater presence of the Fe-Pd alloy in the catalyst. Fe would have a cooperative effect when associated with Pd. Although Fe is inactive alone for chlorobenzene hydrodechlorination, when Fe is coupled to another metal from the group VIIIb, such as Pd, it allows the phenomenon of Pd poisoning by HCl to be reduced.

Bimetallic PdFe catalysts in hydrodechlorination of diclofenac: Influence of support nature, metal deposition sequence and reduction condition

Monometallic palladium and bimetallic palladium-iron catalysts (1 wt% Pd, 10 wt% Fe) were prepared by sequential (denoted as “-s”) and co- (denoted as “-c“) impregnation of alumina and silica – zirconia (ZS) supports with metal nitrates. After reduction with H2 at 320 and 30 °C the catalysts were tested in hydrodechlorination of diclofenac in water at 30 °C in batch and flow-type reactors. The alumina-supported catalysts were more active than the ZS-supported ones, while the bimetallic catalysts were more efficient than the monometallic Pd ones. The co-impregnated bimetallic catalysts showed higher efficiencies than the catalysts prepared by the sequential deposition of metals. Pd/Al2O3 and PdFe/Al2O3-c provided the same rate of DCF conversion in the batch reactor after both types of preliminary reduction, opening the way for energy saving. The catalysts were studied by XRD, TEM, SEM-EDX, low-temperature N2 physisorption, Mössbauer spectroscopy, DRIFT-CO and by XPS after in situ reduction at 320 °C and ex-situ reduction at 30 °C. The improvements in catalyst efficiency resulted from wider pores, formation of PdFe alloys or Pd-Fe-Ox species on the surface, high Pd0/Pd2+ ratio, low extent of Pd encapsulation with the support and especially its coordinately unsaturated sites. The encapsulation degree was the lowest in the co-impregnated catalysts.

Green Synthesis of Pd–Fe Catalyst Supported on ɣ-Al2O3 Using Gobernadora Extract (Larrea tridentata) for the Hydrogenation of 2-Methylfuran to Biorefinery Products

Green Synthesis of Pd–Fe Catalyst Supported on ɣ-Al2O3 Using Gobernadora Extract (Larrea tridentata) for the Hydrogenation of 2-Methylfuran to Biorefinery Products

Hydrodehalogenation of 4-chlorophenol and 4-bromophenol over Pd–Fe/Al2O3: influence of catalyst reduction conditions

The reduction of monometallic Pd/Al2O3 and bimetallic PdFe/Al2O3 catalysts produced by co-impregnation or sequential impregnation of the support with metal salts was possible not only under high temperature hydrogen treatment but also at 30 °C under the action of aqueous phenol solution and hydrogen. According to the XPS data, both reduction routes provided sufficient degrees of Pd reduction required for fast hydrodehalogenation of 4-chlorophenol and 4-bromophenol to phenol in aqueous solutions. The degree of Pd reduction was higher in the co-impregnated bimetallic PdFe catalyst, which was more efficient in transformation of 4-bromophenol; the bimetallic catalysts were more stable than the monometallic Pd one in the conversion of 4-chlorophenol.

Hydrodeoxygenation of Guaiacol over Pd–Co and Pd–Fe Catalysts: Deactivation and Regeneration

In bio-oil upgrading, the activity and stability of the catalyst are of great importance for the catalytic hydrodeoxygenation (HDO) process. The vapor-phase HDO of guaiacol was investigated to clarify the activity, stability, and regeneration ability of Al-MCM-41 supported Pd, Co, and Fe catalysts in a fixed-bed reactor. The HDO experiment was conducted at 400 °C and 1 atm, while the regeneration of the catalyst was performed with an air flow at 500 °C for 240 min. TGA and XPS techniques were applied to study the coke deposit and metal oxide bond energy of the catalysts before and after HDO reaction. The Co and Pd–Co simultaneously catalyzed the CArO–CH3, CAr–OH, and multiple C–C hydrogenolyses, while the Fe and Pd–Fe principally catalyzed the CAr–OCH3 hydrogenolysis. The bimetallic Pd–Co and Pd–Fe showed a higher HDO yield and stability than monometallic Co and Fe, since the coke formation was reduced. The Pd–Fe catalyst presented a higher stability and regeneration ability than the Pd–Co catalyst, with consistent activity during three HDO cycles.

Vapor-phase hydrodeoxygenation of lignin-derived bio-oil over Al-MCM-41 supported Pd-Co and Pd-Fe catalysts

Fast pyrolysis of lignocellulosic biomass is an attractive process to produce bio-oil as an alternative liquid fuel source. Upgrading of bio-oil via hydrodeoxygenation (HDO) is an important route to accomplish this renewable energy production process. Al-MCM-41 supported Pd, Co and Fe catalysts were evaluated for HDO of guaiacol and lignin-derived bio-oil at atmospheric pressure in a fixed-bed reactor. Bimetallic Pd-Co and Pd-Fe catalysts showed higher HDO yield and stability than the monometallic Co and Fe catalysts. The addition of Pd significantly enhanced the stability of Co and Fe catalysts since it helped reduce the coke formation. The lignin-derived bio-oil mainly contained phenolic compounds which had one to three oxygen atoms. The catalytic upgrading could not only eliminate significantly the oxygen of these phenolic compounds but also reduce the amount of tar and heavy components. Pd-Fe catalyst was recognized as a suitable catalyst for upgrading of lignin-derived bio-oil since it produced more deoxygenated products and less gas-phase yield than Pd-Co catalyst.

Enhanced Selective Oxidation of Benzyl Alcohol via In Situ H2O2 Production over Supported Pd-Based Catalysts

Bimetallic Pd-Fe catalysts supported on TiO2 are shown to be highly effective toward the selective oxidation of benzyl alcohol to benzaldehyde via the in situ production of H2O2 from molecular H2 and O2, under conditions where no reaction is observed with molecular O2 alone. The rate of benzyl alcohol oxidation observed over supported Pd-Fe nanoparticles is significantly higher than those of either Pd-Au or Pd-only analogues. This enhanced activity can be attributed to the bifunctionality of the Pd-Fe catalyst to both synthesize H2O2 and catalyze the production of oxygen-based radical specie,s as indicated by an electron paramagnetic resonance analysis. Further studies also reveal the noninnocent nature of the solvent, resulting in the propagation of radical generation pathways.

Selective hydrogenation of levulinic acid to γ-valerolactone using bimetallic Pd-Fe catalyst supported on titanium oxide

The synthesis of γ-valerolactone (GVL), a versatile precursor in the manufacture of high-value chemicals such as polymer plasticizer, solvent, jet fuel, and, agrochemicals, has been targeted by many research groups. In this study, we report the catalytic performance of iron-modified palladium supported on titanium oxide (denoted as Pd(5.0)-Fe(5.0)/TiO2; 5.0 was the loading amount of Pd and Fe, respectively) in the selective hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in stainless-steel batch reactor system. Pd(5.0)-Fe(5.0)/TiO2 catalyst was synthesized by a simple hydrothermal method at 150°C for 24 h, then followed by reduction with H2 at 500°C for 3 h. The X-ray diffraction (XRD) patterns of Pd(5.0)-Fe(5.0)/TiO2 before and after reduction showed the formation of metallic Pd at 2θ = 40.34° and 47.2° corresponding to Pd(111) and Pd(200), respectively. The hydrogenation of LA to GVL effectively occurred in the H2O solvent, whereas in 2-propanol the formation of ester was the main side product. The highest yield of GVL (52.5%) was obtained over Pd(5.0)-Fe(5.0)/TiO2 catalyst at a temperature of 170 °C, initial H2 pressure of 4.0 MPa, solvent H2O 3 ml at a reaction time of 7 h. The yield of GVL slightly increased to 63.3% when the reaction time was prolonged to 15 h.

Highly Active and Durable Ordered Intermetallic PdFe Electrocatalyst for Formic Acid Electrooxidation Reaction

In this paper, we report the preparation of highly active and durable ordered intermetallic PdFe catalyst supported on carbon black for formic acid oxidation reaction (FAOR) by high-temperature hea...

Synthesis of Potentially Bioactive Carbohydrate Derivatives by Chemoslective Hydrogenation with PdFe Catalyst

AbstractA highly efficient and chemoselective hydrogenation method was developed using a bimetallic PdFe catalyst. Pd and Ni catalysts failed in the tests performed. However, PdFe supported on carbon catalyst (10% w/w Pd and a molar ratio Fe/Pd=0.5) achieved interesting results. The selective nitro and aldehyde group reductions on the aromatic aglycone moiety were satisfactory. The desired products were obtained with high conversion and selectivity. A set of aryl O‐glycosides, such as bioactive Gastrodin, were prepared in very good yields and high β‐anomeric selectivity.

Hydrogenation of Carbon Dioxide to C2–C4 Hydrocarbons Catalyzed by Pd(PtBu3)2–FeCl2 with Ionic Liquid as Cocatalyst

Direct hydrogenation of CO2 to C2+ hydrocarbons is very interesting, but achieving this transformation below 200 °C is challenging and seldom reported. Herein, a homogeneous catalytic system was developed composed of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6 ]), Pd(PtBu3 )2 , FeCl2 , and the ligand 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) for hydrogenation of CO2 under mild conditions, which resulted in C2 -C4 hydrocarbons in selectivities up to 98.3 C-mol % at 180 °C. The combination of [BMIm][PF6 ]) with Xantphos endowed the Pd-Fe catalysts with the ability of activating CO2 and H2 simultaneously via [HPd(PtBu3 )(BMIm-COO)(BMIm)(PF6 )Fe]+ species, thus catalyzing the formation of C2 -C4 hydrocarbons through CO2 hydrogenation. In addition, this catalytic system is stable and recyclable, which may have promising applications.

Fully Ordered and Trace Au‐Doped Intermetallic PdFe Catalyst with Extra High Activity and Durability toward Oxygen Reduction Reaction

AbstractDeveloping Pt‐free catalysts with high activity and durability is considered as an essential step for cost reduction and real commercialization of fuel cells. Previous Pt‐free catalysts are either lack of activity and/or insufficient in durability. Here we report the first synthesis of a carbon‐supported PdFe catalyst with a fully ordered intermetallic structure by controlling the atomic ratio of Pd and Fe and high‐temperature annealing for structural ordering. This intermetallic catalyst is then doped with a trace amount of Au (atomic ratio of Au/Pd: 1/50) mainly in the surface region of the ordered lattice. Such an Au‐doped intermetallic PdFe catalyst is finally demonstrated to possess a comparable catalytic activity and much better durability for oxygen reduction reaction than the commercial catalyst of Pt/C. For example, the half‐wave potential of the Au‐PdFe catalyst decreases at a rate 9 times slower than that of Pt/C catalyst after potential cycling under harsh electrochemical conditions. The excellent activity and durability of this new catalyst is attributed to the ordered structure of PdFe particles and the protective effect of the surface Au doping. This study provides a new strategy to developing Pt‐free catalysts, lowering the production cost, and accelerating the practical application of fuel cells.

PdFe bimetallic catalysts for debenzylation of hexabenzylhexaazaisowurtzitane (HBIW) and tetraacetyldibenzylhexaazaisowurtzitane (TADBIW)

PdM (M = Ni, Cu, Co, Fe) bimetallic catalysts were prepared by a precipitation and then reduction method. PdFe bimetal showed superior catalytic performance. The different supports (XC-72, AC, SiO2, Al2O3, TiO2) loaded PdFe catalysts were further investigated by physical adsorption, FESEM, XRD, TEM and XPS. It was found that Fe promoted the precipitation of Pd on the surface of the supports. Meanwhile TiO2 as more suitable supports improved the dispersion, surface concentration and available amount of Pd compared to other carriers and then accelerated the catalytic activities of PdFe bimetal for HBIW and TADBIW debenzylation.

Elucidation of reaction mechanism for m-cresol hydrodeoxygenation over Fe based catalysts: A kinetic study

Fe based catalysts are promising for hydrodeoxygenation (HDO) of lignin derived phenolics due to their high selectivity for aromatics. In this work, the reaction mechanism of m-cresol HDO on Fe catalysts and the kinetic consequence with Pd addition were elucidated by examining the effect of H2, H2O and m-cresol pressures on toluene formation rate on Fe and PdFe catalysts. A direct CO bond cleavage mechanism is proposed for HDO catalysis on both Fe and PdFe catalysts, while Pd provides a facilitated reaction pathway at the PdFe interface and therefore promotes the catalysis on Fe without changing the high selectivity towards aromatics.

Bimetallic Pd-Fe supported on γ-Al2O3 catalyst used in the ring opening of 2-methylfuran to selective formation of alcohols

This work presents the hydrogenation of 2-methylfuran (2-MF) in gaseous fluid phase into a catalytic reactor in order to obtain products with good properties to be used as biofuel. Bimetallic nanoparticles were obtained by impregnation on Al2O3 from the classic catalytic metals used in hydrogenation reactions such as platinum and palladium, combined with iron, to observe the catalytic activity and the selectivity to form interest biofuel compounds. Pt, Pd, Pt-Fe and Pd-Fe catalysts (with 0.5% wt. metal content) supported on alumina were reduced at 450°C and tested. At 200°C, Pt/Al2O3 and Pt-Fe/Al2O3 catalysts presented less than 19% conversion and the main formed product was pentene (90% selectivity). The Pd/Al2O3 catalyst conversion of 2-MF was of 5% at 200°C, obtaining 1-pentanol and 1-butanol as products, together with a 28% of selectivity. The Pd-Fe/Al2O3 catalyst presented the highest conversion of 2-MF at 200°C of 31%, the production of alcohols such as 1-pentanol, 2-pentanol and 1-butanol summed a selectivity of 39%. Since the Pd-Fe/Al2O3 catalyst presented the best performance, it was analyzed under high-resolution transmission electron microscopy technique. The HRTEM image revealed the presence of 5nm size nanoparticles over the alumina, and Pd and Fe oxide nanoparticles were identified measuring the interplanar distances of exposed planes. A FePd3 nanoparticle alloy was also identified, which was the difference in having a greater hydrogenation efficiency for the 2-MF molecule.

Carbon-Supported Pd and PdFe Alloy Catalysts for Direct Methanol Fuel Cell Cathodes.

Direct methanol fuel cells (DMFCs) are electrochemical devices that efficiently produce electricity and are characterized by a large flexibility for portable applications and high energy density. Methanol crossover is one of the main obstacles for DMFC commercialization, forcing the search for highly electro-active and methanol tolerant cathodes. In the present work, carbon-supported Pd and PdFe catalysts were synthesized using a sodium borohydride reduction method and physico-chemically characterized using transmission electron microscopy (TEM) and X-ray techniques such as photoelectron spectroscopy (XPS), diffraction (XRD) and energy dispersive spectroscopy (EDX). The catalysts were investigated as DMFC cathodes operating at different methanol concentrations (up to 10 M) and temperatures (60 °C and 90 °C). The cell based on PdFe/C cathode presented the best performance, achieving a maximum power density of 37.5 mW·cm−2 at 90 °C with 10 M methanol, higher than supported Pd and Pt commercial catalysts, demonstrating that Fe addition yields structural changes to Pd crystal lattice that reduce the crossover effects in DMFC operation.

Combining HDC and CWPO for the removal of p-chloro-m-cresol from water under ambient-like conditions

Catalysts supported on aluminium pillared clays (Al-PILCs) using Fe and Pd or Rh as active phases have been prepared and tested for a two-step treatment of p-chloro-m-cresol (PCMC) in water by catalytic hydrodechlorination (HDC) followed by catalytic wet peroxide oxidation (CWPO) under ambient-like conditions (25°C, 1atm). Both processes were first studied independently. HDC was investigated with Pd and Rh monometallic catalysts as well as Pd-Fe and Rh-Fe bimetallic ones. The bimetallic Pd-Fe catalyst showed the best performance, allowing complete dechlorination in less than 1h reaction time. On the other hand, CWPO of PCMC with a monometallic Fe catalyst allowed complete conversion of that pollutant but with only about 33% reduction of total organic carbon (TOC) after 4h. Then, a two-step approach consisting in HDC of PCMC followed by CWPO has been tested for the first time in two different ways. The first one used a Pd-Fe bimetallic catalyst in both steps while in the second approach monometallic Pd and Fe catalysts were used for HDC and CWPO, respectively. The HDC in alkaline medium allowed reducing significantly Fe leaching. This second approach yielded complete dechlorination followed by higher mineralization (>55%) with better efficiency of H2O2 consumption.