Bimetallic Pd-Ni Catalysts Research Articles

Role of Ni in Bimetallic PdNi Catalysts for Ethanol Oxidation Reaction

Bimetallic PdNi catalysts have garnered great interest in the study of ethanol oxidation reactions (EORs), though mechanistic insights into their catalytic performances are lacking, which hinders f...

Liquid-phase hydrogenation of N-nitrosodimethylamine over Pd-Ni supported on CeO2-TiO2: The role of oxygen vacancies

Catalytic liquid-phase hydrogenation of N-nitrosodimethylamine (NDMA) over CeO2, TiO2 and CeO2-TiO2 (CexTi, x referred to the molar ratio of Ce to Ti) supported Pd-Ni bimetallic catalysts (Pd-Ni/CexTi) was investigated. Characterization results indicated that Ce-O-Ti solid solutions formed through the incorporation of Ti4+ into the CeO2 lattice, resulting in increased specific surface areas and reduced average crystal sizes of CexTi. Ti doping also promoted the generation of oxygen vacancies (Ov) on the surface of CexTi. For Pd-Ni/CexTi, the amount of oxygen vacancies first increased and then decreased with the increasing of Ti content, and the maximum content of Ov was observed on Pd-Ni/Ce4Ti. Consequently, Pd-Ni/Ce4Ti had the smallest metal particle sizes, due to the strong metal-support interaction formed between Pd-Ni and Ov. Pd-Ni/CexTi exhibited much higher catalytic activities than that of Pd/CeO2 and Pd/TiO2 for NDMA reduction, and the Pd-Ni/Ce4Ti had the highest activity. The catalytic activity of Pd-Ni/CexTi was relevant to the oxygen vacancies on the support, which influenced the metal dispersion and the adsorption of intermediate product of NDMA reduction.

Modern Ni and Pd–Ni Catalysts Supported on Sn–Al Binary Oxide for Oxy‐Steam Reforming of Methanol

AbstractMonometallic Ni and bimetallic Pd–Ni catalysts supported on mono‐SnO2 and SnO2–Al2O3 binary oxide are prepared using a wet impregnation and subsequent impregnation method. The catalysts are tested in oxy‐steam reforming of methanol (OSRM) and characterized. The activity measurements show that palladium‐promoted nickel catalysts supported on SnO2–Al2O3 exhibit high activity, selectivity towards hydrogen formation, and stability. The effect of Pd on reducibility, surface acidity, and morphology of the Ni supported catalyst, as well as its catalytic properties in OSRM, are discussed in detail.

Hydrogenation of 2-ethylanthraquinone with bimetallic monolithic catalysts: An experimental and DFT study

We studied the hydrogenation of 2-ethylanthraquinone (eAQ) over Pd/SiO2/COR (COR = cordierite) monometallic and Pd-M/SiO2/COR (M = Ni, Fe, Mn, and Cu) bimetallic monolithic catalysts, which were prepared by the co-impregnation method. Detailed investigations showed that the particle sizes and structures of the Pd-M (M = Ni, Fe, Mn, and Cu) bimetallic monolithic catalysts were greatly affected by the second metal M and the mass ratio of Pd to the second metal M. By virtue of the small particle size and the strong interaction between Pd and Ni of Pd-Ni alloy, Pd-Ni bimetallic monolithic catalysts with the mass ratio of Pd/Ni = 2 achieved the highest H2O2 yield (7.5 g/L) and selectivity (95.3%). Moreover, density functional theory calculations were performed for eAQ adsorption to gain a better mechanistic understanding of the molecule-surface interactions between eAQ and the Pd(1 1 1) or PdM(1 1 1) (M = Ni, Fe, Mn, and Cu) surfaces. It was found that the high activity of the bimetallic Pd-Ni catalyst was a result of strong chemisorption between Pd3Ni1 (1 1 1) and the carbonyl group of eAQ.

Improvement Effect of Ni to Pd-Ni/SBA-15 Catalyst for Selective Hydrogenation of Cinnamaldehyde to Hydrocinnamaldehyde

A series of Pd-Ni bimetallic catalysts supported on SBA-15 (0.2%Pd-x%Ni/SBA-15, x = 0.4, 0.7, and 1.2) were prepared through the impregnation method combined with the NaBH4 reduction method. X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoemission spectroscopy (XPS) and transmission electron microscope (TEM) were used to characterize the prepared catalysts. All the synthesized catalysts were evaluated for the liquid-phase hydrogenation of cinnamaldehyde (CAL). The addition of Ni obviously enhanced the CAL conversion and selectivity of C=C hydrogenation to hydrocinnamaldehyde (HALD) over the 0.2%Pd-x%Ni/SBA-15 catalysts. Meanwhile, 0.2%Pd-1.2%Ni/SBA-15 showed the best performance with 96.3% conversion and 87.8% selectivity toward HALD. This improvement was attributed to the synergistic effect between the Pd and Ni nanoparticles, enhancing the dispersion of Pd metal particles and increasing the content of surface Pd0 species. In addition, the influences of a few reaction factors including H2 pressure, reaction temperature, and reaction time were studied over 0.2%Pd-1.2%Ni/SBA-15.

A novel Pd-Ni bimetallic synergistic catalyst on ZIF-8 for Sonogashira coupling reaction

Monometallic Pd@ZIF-8, Ni@ZIF-8 and bimetallic PdxNiy@ZIF-8 catalysts have been successfully synthesized by a simple liquid impregnation-reduction method. The structure of catalysts and the electronic states of introduced metals were characterized and their catalytic performances were evaluated in Cu free and ligands free Sonogashira coupling reaction under atmosphere. Compared with monometallic catalyst, the as-synthesized bimetallic Pd5Ni95@ZIF-8 catalyst exhibited excellent catalytic performance with 94.50% yield. Therefore, the above experimental results suggested a synergistic effect derived from palladium and nickel, which enhanced Sonogashira coupling reaction obviously. Moreover, modification of Ni@ZIF-8 with trace of palladium can effectively promote its catalytic activity, indicating an economical way to develop efficient catalysts.

Up-gradation of α-tetralone to jet-fuel range hydrocarbons by vapour phase hydrodeoxygenation over Pd[sbnd]Ni/SBA-16 catalysts

Mesoporous molecular sieve SBA-16 supported PdNi bimetallic catalysts were synthesized by the co-impregnation method. PdNi/SBA-16 bimetallic Im3m mesoporous catalyst showed superior catalytic performance in the production of jet-fuel range hydrocarbons. Vapour phase hydrodeoxygenation of α-tetralone was carried out under ambient pressure and the highest selectivity (88.21%) for the isomerized product trans-decalin was obtained. PdNi impregnated on different mesoporous (MCM-41, SBA-15, KIT-6) and metal oxides (γ-Al2O3, CeO2, TiO2, ZrO2, SiO2) supports and the catalytic activity was compared with PdNi/SBA-16. Synergetic interaction between the Pd(111) and Ni(111) with increased total acidity enhanced the catalytic activity of PdNi/SBA-16. Among the bimetal, Nickel was found to be the most active metal for the complete reduction of aromatic ring, while Pd favoured the deoxygenation. The major products obtained from hydrodeoxygenation of α-tetralone were cis/trans-decalin, tetralin and α-tetralol.

Porous bimetallic PdNi catalyst with high electrocatalytic activity for ethanol electrooxidation

Porous bimetallic PdNi catalysts were fabricated by a novel method, namely, reduction of Pd and Ni oxides prepared via calcining the complex chelate of PdNi-dimethylglyoxime (PdNi-dmg). The morphology and composition of the as-prepared PdNi were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, the electrochemical properties of PdNi catalysts towards ethanol electrooxidation were also studied by electrochemical impedance spectrometry (EIS), cyclic voltammetry (CV) and chronoamperometry (CA) measurement. In comparison with porous Pd and commercial Pd/C catalysts, porous structural PdNi catalysts showed higher electrocatalytic activity and durability for ethanol electrooxidation, which may be ascribed to Pd and Ni property, large electroactive surface area and high electron transfer property. The Ni exist in the catalyst in the form of the nickel hydroxides (Ni(OH)2 and NiOOH) which have a high electron and proton conductivity enhances the catalytic activity of the catalysts. All results highlight the great potential application of the calcination-reduction method for synthesizing high active porous PdNi catalysts in direct ethanol fuel cells.

Enhanced catalytic reduction of N-nitrosodimethylamine over bimetallic Pd-Ni catalysts

Catalytic reduction of N-nitrosodimethylamine (NDMA) was investigated over γ-Al2O3 supported bimetallic Pd-Ni catalysts (3%(PdxNi1−x)). NDMA could be reduced to dimethylamine over 3%(Pd0.8Ni0.2) with a metal-loading-normalized pseudo-first-order rate constant of 836±21Lgme−1h−1.Characterization results showed that the reducibility of PdO (or NiO) was improved by addition of Ni (or Pd) in 3%(PdxNi1−x); Pd-Ni ensembles were formed in 3%(PdxNi1−x) and there was an electronic transfer from Pd to Ni; metal dispersion was affected by the formation of Pd-Ni ensembles and a volcano curve of metal dispersion via Pd/Ni ratio was observed. The activity profiles demonstrated that TOF had a significant positive relationship with metal dispersion of 3%(PdxNi1−x), indicating high metal dispersion favor NDMA reduction.NDMA reduction over 3%(Pd0.8Ni0.2) catalyst could be described by Langmuir-Hinshelwood model, reflecting an adsorption controlled reduction mechanism. The reduction mechanism of NDMA over 3%(Pd0.8Ni0.2) catalyst was proposed to be that H2 was activated by Pd, and H spillover from Pd to Ni/NiO reduced NDMA though N-N cleavage.

Ordered mesoporous alumina-supported bimetallic Pd–Ni catalysts for methane dry reforming reaction

To compare the influence of Pd addition to Ni supported on ordered mesoporous alumina catalyst, prepared highly ordered mesoporous alumina (MA) was used as catalyst support for methane dry reforming under atmospheric pressure.

Catalytic Effect of Pd-Ni Bimetallic Catalysts on High-Temperature Co-Electrolysis of Steam/CO2 Mixtures

The performance of solid oxide electrolysis cells for high-temperature co-electrolysis of steam/CO2 mixtures was enhanced by raising the amount of Pd-Ni bimetallic catalysts fabricated inside their fuel-electrode substrate. High-temperature co-electrolysis has been proposed as a promising technology to store renewable electrical energy in the form of chemical energy and convert CO2 to valuable syngas. To deploy it into energy markets, it is essential to improve its energy storage efficiency and syngas productivity. In this study, the catalytic effect of Pd-Ni bimetallic catalysts on electrochemical performance and CO2 conversion was examined to meet these needs. Their homogeneous morphology and distribution were obtained by using an advanced infiltration technique. Increasing the amount of Pd-Ni bimetallic catalysts promotes a reverse water gas shift (RWGS) reaction enhancing steam transport toward the functional layer and hence decreasing a concentration overpotential. This raises a limiting current density and reduces an overvoltage imposed on the cells, in particular, at high current density. In addition, the enhanced RWGS reaction kinetics driven by a higher amount of Pd-Ni bimetallic catalysts loadings enables increasing the CO2 conversion rate and CO concentration in the product stream. These may enhance the energy storage capacity and lowers the energy requirements for high-temperature co-electrolysis.

ChemInform Abstract: Hydrogenation of (N,N‐Disubstituted Aminomethyl)nitrobenzenes to (N,N‐Disubstituted Aminomethyl)anilines Catalyzed by Palladium—Nickel Bimetallic Nanoparticles.

AbstractA stable nanosized Pd‐Ni bimetallic catalyst is prepared by heating Raney‐Ni and Na2PdCl4 in water.

Sulfur adsorption and release properties of bimetallic Pd–Ni supported catalysts

The formation of hydrogen sulfide in car exhaust is undesirable due to unpleasant odor and toxicity of H2S gas. H2S release can be suppressed by the addition of a NiO scavenger to a three-way catalyst (TWC). In this work, Pd–Ni bimetallic catalysts were prepared by the co-addition of Pd and Ni to γ-Al2O3 or Al2O3-La2O3 support, by the impregnation method. Different concentrations of a propionic acid aqueous solution were used as the impregnation solvent. The structure of prepared catalysts was characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature-programmed reduction (TPR) techniques. Catalyst poisoning by SO2 was simulated under lean conditions and H2S release under rich conditions. XRD and TPR measurements revealed the effect of the impregnation solvent concentration on the ratio between NiO and NiAl2O4 spinel species and the reducibility of Ni species. Co-addition of Pd with Ni was proven to be beneficial for H2S suppression. Prepared bimetallic catalysts released considerably less H2S compared to physical mixtures of Pd/Al2O3 with NiO. The presence of bulk and well dispersed NiO on Pd–Ni catalysts assisted in sulfur release in the form of sulfur oxides rather than H2S. Bimetallic catalysts supported on Al2O3-La2O3 were found to release more H2S compared to catalysts on γ-Al2O3. The use of diluted solvent in bimetallic catalysts preparation decreased H2S release from Pd–Ni catalysts.

Catalytic performance of Pd–Ni bimetallic catalyst for glycerol hydrogenolysis

Catalytic conversion of glycerol from biodiesel production to value-added chemicals and fuels is actually of great interest for industrial chemical research. Bimetallic catalysts are confirmed superior to monometallic catalysts in terms of catalytic activity and selectivity for glycerol hydrogenolysis. Accordingly, a series of Pd–M (M = Fe, Co, Ni, Cu, Zn) bimetallic catalysts were prepared in this work via coprecipitation to investigate the promoting effect of Pd. The relationship between the catalytic performance and metal-support interaction was also discussed. Through the catalyst screening, Pd–Ni bimetallic catalyst exhibited moderate activity and the highest selectivity towards ethylene glycol. At 493 K and hydrogen pressure of 6.0 MPa, the glycerol conversion and selectivity of ethylene glycol reached 89% and 22% respectively. XRD and TEM patterns showed that the Pd nanoparticles with an average size of ∼4 nm were uniformly dispersed in the supports. H2-TPR revealed that the reduction temperatures of metal oxides were significantly decreased by the introduction of Pd component. XPS curves indicated that unique performance of the Pd–Ni bimetallic catalyst might be attributed to the formation of Pd–Ni alloy. And the required metal-support interaction was assumed responsible for the cleavage of C–C bond and generation of ethylene glycol. In the end, hydrogenolysis reactions for the main products of glycerol conversion were carried out over Pd–Ni catalyst to explore the possible reaction pathways for glycerol hydrogenolysis.

Highly selective and stable PdNi catalyst derived from layered double hydroxides for partial hydrogenation of acetylene

An effective and versatile synthetic approach is presented to prepare highly selective and stable bimetallic PdNi catalyst for selective hydrogenation of acetylene. NiMgAl-layered double hydroxide (LDH) was synthesized by separate nucleation and aging steps, followed by the introduction of PdCl42− to obtain the catalyst precursor. The positive charge of NiMgAl-LDH layer offers an opportunity to realize uniform dispersion of PdCl42−, which facilitates the formation of bimetallic PdNi nanoparticles. Upon thermal reduction of PdCl42−/NiMgAl-LDH precursor, highly dispersed bimetallic PdNi/MgAl-MMO catalyst was obtained. As comparison, MMO-supported PdNi catalyst was also prepared by the co-impregnation and sol-immobilization method. The catalyst derived from LDH precursor exhibited much higher activity and selectivity toward ethene than that prepared by other two methods, which could be attributed to smaller metal particle size and stronger interaction between two metals. Furthermore, because of preferable structure stability, this catalyst also possessed higher stability of activity. Preferable structure stability of the catalyst could be due to the net trap effect of MgAl-MMO microcrystals stemming from LDH precursor, which provided fixed positions for the PdNi nanoparticles during the reaction.

Preparation and characterization of Pd–Ni bimetallic catalysts for CO and C3H6 oxidation under stoichiometric conditions

Ni additive in the three-way catalyst (TWC) has been known for its high activity in H2S suppression. However, the effect of Ni on the activity of TWC in stoichiometric exhaust gas conversion is less studied. In the present work characterization of bimetallic Pd–Ni catalysts supported on γ-Al2O3 or γ-Al2O3–La2O3 for potential TWC application was performed. The catalysts were prepared by wet co-impregnation and impregnation-evaporation methods. Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), temperature-programmed reduction (TPR), UV–vis diffuse reflectance spectrometry (UV–vis DRS), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) techniques were employed to confirm the effect of Ni addition on the catalysts structure. XRD, TPR, and STEM characterization was employed in order to evaluate the presence of Pd–Ni interaction. The activity of the catalysts was tested in the oxidation reaction of CO and C3H6 under stoichiometric conditions. Based on the obtained results, we confirmed the structure of prepared catalysts and the effect of Pd–Ni interaction on the catalytic activity of Pd–Ni catalysts in CO and C3H6 oxidation. XRD and TPR characterization suggested that Pd and Ni are competing for the support sites. The observed competition affected Pd-support and Ni-support interactions and consequently activity. Fresh bimetallic catalysts had higher catalytic activity compared to monometallic ones due to higher active metal loading and the presence of NiO phase. It was concluded that the catalytic activity of aged bimetallic catalysts is not affected by the addition of Ni. For that reason, addition of Ni as a second metal to Pd-based catalysts for TWC reactions can be considered in the future studies.

Replacing Precious Metals with Carbide Catalysts for Hydrogenation Reactions

Pd–Ni bimetallic catalysts have been shown as more efficient catalyst for selective hydrogenation than the monometallic Pd catalyst. However, there is still precious component Pd in the catalyst, and the catalyst cost is still high. The current chapter will design non-precious catalyst for selective hydrogenation for dienes.

Effect of oxide supports on Pd–Ni bimetallic catalysts for 1,3-butadiene hydrogenation

Our previous work showed that the Pd–Ni bimetallic catalyst had better hydrogenation activity and 1-butene selectivity in the selective hydrogenation of 1,3-butadiene. In the present work, the effect of oxide supports on the hydrogenation of 1,3-butadiene was studied over Pd–Ni bimetallic catalysts supported on γ-Al2O3, SiO2, CeO2, ZrO2 and TiO2. Transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS) were used to characterize the particle size and the extent of Pd–Ni bimetallic bond formation, respectively. The support effect affected the bimetallic particle structure, but appeared to have no apparent influence in the hydrogenation activity. All the bimetallic catalysts showed ∼100% selectivity to butenes; however, the supports affected the 1-butene selectivity. PdNi/γ-Al2O3 showed the highest 1-butene selectivity of ∼80% at 1,3-butadiene conversions lower than 50% but decreased rapidly at higher conversion. The different performance of the supports in 1-butene selectivity might be attributed to strong metal-support interaction (SMSI), the oxygen defects and the geometric/electronic effect on the catalysts.

Bimetallic Pd-Ni core-shell nanoparticles as effective catalysts for the Suzuki reaction

A simple and efficient solution-based method for the synthesis of Pd-Ni bimetallic nanoparticles (NPs) has been developed. A series of Pd-Ni bimetallic NPs were readily achieved by reduction of PdCl2 and Ni(acac)2 (acac = acetylacetonate) in the presence of oleylamine (OAm), oleic acid (OA) and benzyl alcohol. Furthermore, by using high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectrometry (EDS) mapping and X-ray diffraction (XRD), we demonstrate that the as-prepared Pd-Ni bimetallic NPs have core-shell structures with a Pd-rich core and a Ni-rich shell. In addition, the as-obtained Pd-Ni bimetallic NPs with varying compositions show excellent catalytic activities in the Miyaura-Suzuki reaction. When the nickel molar percentage was 0.23 to 0.65, the conversion with the as-obtained Pd-Ni bimetallic catalysts was above 90%. It is believed that this strategy can be employed to produce a variety of other well-defined core-shell type multimetallic nanostructures.

Selective hydrogenation of 1,3-butadiene on Pd[sbnd]Ni bimetallic catalyst: From model surfaces to supported catalysts

The selective hydrogenation of 1,3-butadiene serves as a means to purify the butene stream generated from cracking naphtha or gas oil. To identify selective hydrogenation catalysts, 1,3-butadiene was studied on single crystal Ni/Pd(111) bimetallic surfaces, utilizing density functional theory (DFT) calculations and temperature-programmed desorption (TPD). DFT calculations predicted that the Pd-terminated bimetallic surface should be more active and selective to produce 1-butene, which were verified experimentally using TPD. The promising results on model surfaces were extended to γ-Al2O3-supported catalysts using both batch and flow reactors. Extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) confirmed the formation of bimetallic nanoparticles. The PdNi bimetallic catalyst showed higher hydrogenation activity and 1-butene selectivity than the monometallic catalysts. The excellent correlation between model surfaces and supported catalysts demonstrates the feasibility of designing effective bimetallic catalysts for selective hydrogenation reactions.