Ni-Cu Bimetallic Catalysts Research Articles

Electrodeposited NiCu bimetal on carbon paper as stable non-noble anode for efficient electrooxidation of ammonia

Electrochemical remediation of ammonia-containing wastewater at low cell voltage is an energy-effective technology which can simultaneously recover energy via hydrogen evolution reaction. One of the main challenges is to identify a robust, highly active and inexpensive anode for ammonia electrooxidation. Here we present an alternative anode, prepared by electrochemical co-deposition of Ni and Cu onto carbon paper. This NiCu bimetallic catalyst is characterised by scanning electron microscope, scanning transmission electron microscope, X-ray diffraction, x-ray photoelelectron spectroscopy, cyclic voltammetry, linear sweep voltammetry and chronoamperometry techniques. The stability and activity of NiCu bimetallic catalyst are largely improved in comparison with Ni or Cu catalyst. Moreover this noble-metal-free NiCu catalyst even performs better than Pt/C catalyst, as NiCu is not poisoned by ammonia. An ammonia electrolysis cell is fabricated with NiCu/carbon paper as anode for ammonia electrolysis. The influences of pH value, applied cell voltages and initial ammonia concentration on cell current density, ammonia removal and energy efficiency are tested. An ammonia removal efficiency of ∼80% and coulombic efficiency up to ∼92% have been achieved. Ni-Cu bimetal on carbon paper is a stable non-noble anode for efficient electrooxidation of ammonia.

Selective hydrogenation of furfural to tetrahydrofurfuryl alcohol over Ni/CNTs and bimetallic Cu[sbnd]Ni/CNTs catalysts

A series of Ni, Cu and bimetallic CuNi catalysts with different metals loadings supported on CNTs were prepared by impregnation methods for liquid-phase hydrogenation of furfural to tetrahydrofurfuryl alcohol (THFA). Various effects of reaction parameters such as, reaction temperature, reaction time, hydrogen pressure, different supports and different loading amount of Ni over both monometallic and bimetallic catalysts were fully studied. Among the catalysts investigated, 10 wt% Ni/CNT and bimetallic CuNi catalysts showed high conversion of furfural and selectivity towards THFA. Bimetallic CuNi catalysts exhibit the best catalytic performance of 100% conversion of furfural and up to 90.3% selectivity towards THFA at mild condition of 130 °C, 40 bar hydrogen and 10 h reaction time. CuNi bimetallic synergistic effect has been interpreted through XPS measurement and a possible hydrogen-transfer mechanism is proposed. The features of the CNTs supported catalysts were investigated via XRD, XPS, TEM, H2-TPR and the N2 adsorption–desorption isotherms. The Ni and bimetallic CuNi catalysts prepared in this work is inexpensive and simple, which makes them a promising candidate for the conversion of furfural to THFA.

CuNi@C catalysts with high activity derived from metal–organic frameworks precursor for conversion of furfural to cyclopentanone

CuNi bimetallic nanoparticles embedded in carbon matrix (CuNi@C) were synthesized and applied in the selective conversion of biomass-derived furfural to cyclopentanone. The catalysts were prepared directly from thermolysis of Cu-based metal–organic frameworks (MOFs) impregnated with nickel nitrate. Compared with traditional precipitation method, relatively high surface area (91.6m2/g) and nano-sized (about 15nm) metallic copper and nickel particles can be obtained when molar ratio of nickel to copper was 0.5. Furthermore, the porous carbon matrix can not only act as a supporter but prevent the accumulation of metal particles. By varying the molar ratio of nickel to copper, CuNi0.5@C shows best catalytic performance (99.3% conversion of furfural and 96.9% yield of cyclopentanone) at optimum conditions (130°C, 5h, 5MPa) attributed to the above mentioned properties. In addition, the CuNi0.5@C can be reused four times with good activity and stability. Hence, current work presents a new and facile method to prepare CuNi bimetallic catalysts which has a brilliant performance in catalytic conversion of furfural to cyclopentanone.

Borohydride reduction of Al2O3 supported NiCu bimetallic catalysts for the hydrogenation of styrene: study of surface properties

The surface properties of Ni particles can be altered by the addition of a second metal. This influences its catalytic properties. Hence, the surface properties of a series of alumina (Al2O3) supported NiCu bimetallic catalysts prepared via chemical reduction using KBH4 were investigated. They were characterized using H2-chemisorption, H2-temperature programmed desorption, H2-temperature programmed reduction, X-ray diffraction and scanning electron microscopy analysis and tested for the hydrogenation of styrene in liquid phase. In the bimetallic catalysts, Ni and Cu existed as NiCu species or as separate phases. The Ni active sites favored the hydrogenation of styrene to only ethylbenzene. However, the extent of hydrogenation was mainly determined by the types of Ni active sites available on the catalyst which depended on the Cu/Ni ratio. The surface structure of the nickel phase is modified by incorporation of copper.

Pelletization of catalysts supported on activated carbon. A Case Study: clean synthesis of dimethyl carbonate from methanol and CO2

The synthesis of Cu-Ni bimetallic catalyst supported on pellets of activated carbon using carboxymethylcellulose (CMC) as a binder is reported. The effect of preparation conditions, such as binder concentration, AC/binder ratio, temperature, and pyrolysis heating rate on the surface area of the pellets, was evaluated. Cu and Ni metals were incorporated on the pellets by conventional incipient wetness impregnation. The support and the synthesized catalysts were characterized using N2 adsorption, H2 -TPR, XRD and SEM-EDS techniques. The pelletized catalysts were evaluated for the direct synthesis of dimethyl carbonate DMC (case study). An improved catalytic activity (e.g., ca. 20% increase in conversion) in structured pelletized catalyst in comparison to the powdered catalyst was found.

Selective Hydrogenolysis of Glycerol to 1,2-Propanediol Over Bimetallic Cu-Ni Catalysts Supported on γ-Al2O3

A series of Cu or Ni monometallic and Cu-Ni bimetallic catalysts supported on γ-Al2O3 were synthesized by incipient wetness impregnation method. X-ray diffraction results exhibited the formation of bimetallic Cu-Ni phase in the reduced Cu-Ni(1:1)/γ-Al2O3 catalyst. Among the catalyst examined for hydrogenolysis of glycerol, bimetallic catalysts exhibited higher catalytic activity than monometallic catalysts due to synergetic effect of Cu-Ni bimetal. Cu-Ni(1:1)/γ-Al2O3 catalyst displayed a maximum glycerol conversion of 71.6% with 92.8% selectivity to 1,2-propanediol at 210 °C and 4.5 MPa hydrogen pressure. The superior performance of Cu-Ni(1:1)/γ-Al2O3 catalyst was attributed to the formation of bimetallic Cu-Ni phase, high active metal surface area, small Cu-Ni particle size, and high acidic strength of the catalyst. Stability and reusability of Cu-Ni(1:1)/γ-Al2O3 catalyst was performed and detailed characterization results of fresh and used catalysts suggested that bimetallic Cu-Ni phase remained stable after reuses.

Dehydrogenation of primary aliphatic alcohols to aldehydes over Cu-Ni bimetallic catalysts

The catalytic conversion of non-activated primary aliphatic alcohols to aldehydes is a challenge, and monometallic Cu-based catalysts loaded on different supports have often been used for these reactions. Cu-Ni/γ-Al2O3 bimetallic catalysts were prepared and used for anaerobic dehydrogenation of 3,3-dimethyl-1-butanol to 3,3-dimethyl-1-butanal. These catalysts exhibited higher activity than Cu/γ-Al2O3 under the same reaction conditions, and a wide range of primary aliphatic alcohols were efficiently converted to the corresponding aldehydes over Cu-Ni/γ-Al2O3 under mild conditions.

Catalytic hydrotreatment of fast-pyrolysis oil using non-sulfided bimetallic Ni-Cu catalysts on a δ-Al2O3 support

Fast pyrolysis oil from lignocellulosic biomass is an attractive energy carrier. However, to improve the product characteristics such as a reduced polarity and higher thermal stability, upgrading is required. We here report activities on the catalytic hydrotreatment of fast pyrolysis oil using bimetallic NiCu/δ-Al2O3 catalysts with various Ni/Cu ratios (0.32 to 8.1 w/w) at a fixed total metal intake of about 20wt% with the objective to improve product properties for co-feeding applications in conventional oil refineries. Hydrotreatment reactions were initially carried out for a model compound (anisole, continuous set-up, 300°C, 10bar) and subsequently for fast pyrolysis oil (batch autoclave, 1h at 150°C followed by 3h at 350°C, at 100bar initial pressure). Best results, i.e. the highest hydrodeoxygenation yield for experiments with anisole (75mol%), and an upgraded oil with the most favorable properties for fast pyrolysis oil (high H/C ratio, low Mw of 500g/mol, low thermogravimetric residue of 6.8wt%), were obtained for a catalyst with a Ni to Cu wt% ratio of eight (16Ni2Cu). For this catalyst, hydrogen consumption was the highest (146NL/kgPO). The findings were rationalized using a reaction network model earlier developed for Ru/C. Analysis of catalyst (ICP, HRTEM, XRD and TGA) before and after reaction showed the occurrence of leaching of both active metals (Ni and Cu) and support, as well as coke deposition on the support. The most active catalyst in the series (16Ni2Cu) also gave lowest leaching and coking levels in the series.

Ethanol steam reforming over Ni-Cu/Al 2O 3-M yO z (M = Si, La, Mg, and Zn) catalysts

Ni-based catalysts doped with copper additives were studied on their role in ethanol steam reforming reaction. The effects of Cu content, support species involving Al 2O 3-SiO 2, Al 2O 3-MgO, Al 2O 3-ZnO, and Al 2O 3-La 2O 3, on the catalytic performance were studied. Characterizations by TPR, XRD, NH 3-TPD, XPS, and TGA indicated that catalysts 30Ni5Cu/Al 2O 3-MgO and 30Ni5Cu/Al 2O 3-ZnO have much higher H 2 selectivity than 30Ni5Cu/Al 2O 3-SiO 2, as well as good coke resistance. H 2 selectivity for 30Ni5Cu/Al 2O 3-MgO catalyst was 73.3% at 450 °C and increased to 94.0% at 600 °C, whereas for 30Ni5Cu/Al 2O 3-ZnO catalyst, the H 2 selectivity was 63.6% at 450 °C and 95.2% at 600 °C. These Al 2O 3-MgO and Al 2O 3-ZnO supported Ni-Cu bimetallic catalysts may have important applications in the production of hydrogen by ethanol steam reforming reactions.

CO Hydrogenation Catalyzed by Supported Ni-Cu Bimetallic Catalysts

A series of Ni-Cu/ZnO and a series of Ni-Cu/SiO2 catalysts were prepared by coprecipitation and impregnation methods, respectively, and studied in CO hydrogenation. The results revealed the presence of metal-support interactions between Cu and ZnO, and between Ni and ZnO, and a bimetallic interaction between Ni and Cu. The bimetallic interaction affected the metal-support interactions.

Structure and catalytic properties of Cu-Ni bimetallic catalysts for hydrogenation

The dependence of catalytic activity and selectivity of Cu-Ni bimetallic catalysts for oil hydrogenation on Cu∶Ni ratios have been investigated while they were reduced at low temperature (230 °C). Two maxima occurred at Cu2Ni1 and Cu1Ni3 in the activity-Cu∶Ni curve. Cu riched catalysts have higher selectivity than Ni riched ones, and may cause dehydrogenation and isomerization of linoleate at the beginning of the reaction. The structures of the catalysts reduced at different temperatures have been studied by means of XRD, XPS, EXAFS and FMR et al. The structure of the catalysts reduced at 230 °C can be described as an aggregate of Cu particles inlaid with Ni atoms and unreduced NiO, and the easily reduced Cu always segregates on the surface, while homogeneous solid solution particles can be formed in the case 400 °C being used as reduction temperature.