Nickel Bimetallic Catalysts Research Articles

Catalytic reforming of polypropylene to produce hydrogen: Influence of support characteristics and active metal type in catalyst

Hydrogen production by catalytic pyrolysis of waste plastics has attracted extensive attention in recent years. This paper takes hydrogen production as the starting point. A variety of supported nickel catalysts were developed for the catalytic pyrolysis of polypropylene using a two-stage fixed bed reactor. Based on the better characteristics of bimetallic catalysts, calcium, magnesium, iron doped nickel bimetallic catalysts were prepared to explore the improvement effect of catalytic hydrogen production performance. The micromorphology, structure composition and active substance distribution of different supported catalysts and bimetallic catalysts were measured. The experimental results show that the catalyst with powdered activated carbon as the support has the best catalytic performance of hydrogen production. In a series of molecular sieve catalysts, the smaller the Si/Al ratio of the support, the higher the catalytic performance. Among the bimetallic catalysts, Fe-Ni bimetallic catalysts have better catalytic advantages than Ca-Ni and Mg-Ni bimetallic catalysts, which is closely related to the stable Fe-Ni alloy structure formed on the catalyst surface. In conclusion, the differences in catalytic performance between catalyst support and active metal discussed in this paper will provide theoretical support for the catalytic pyrolysis technology of plastics to produce hydrogen.

Tailoring chemoselectivity of Fe/Ni catalyst for hydrogenation of carbonyl compound

Selective hydrogenation of carbonyl moiety in the presence of olefinic group and other reducible functionality is an industrially important transformation. However, the protocol of green chemistry cannot be sacrificed for its formidable challenging transformation. Therefore, iron nickel bimetallic recyclable catalyst (Fe/Ni) was used for base free hydrogenation of carbonyl compound with high activity and chemoselectivity in microwave environment. The microwave irradiation and pre-treatment of bimetallic catalyst (Fe/Ni) divert conversion/selectivity towards CO group as compared to CC or another reducible moiety. This is further confirmed by DFT calculations which shows that the CO site is strongly interacted with the surface compared to the CC site. The pyridine adsorption studies revealed that pre-treated (Fe/Ni) possess more acidic sites as compared to untreated catalyst. Furthermore, the selectivity of bimetallic catalysts towards hydrogenation of carbonyl function group was correlated with Fe content present in the matrix of catalyst.

Ni-nanoparticle-modified Cu nanowires for enhanced electrocatalytic nitrate removal

Copper (Cu)-based materials have been extensively studied for nitrate (NO3 −) removal as an inexpensive and abundant electrocatalyst for water purification through the nitrate reduction reaction (NO3RR). However, it typically suffers from nitrite (NO2 −) accumulation due to high selectivity toward nitrite formation. To address this issue, the authors herein report a strategy of modifying copper nanowires with nickel (Ni) nanoparticles to improve the NO3RR performance. The nickel nanoparticles both facilitate electron transfer from nickel to copper and enhance the conversion of nitrite, thereby improving the overall removal of nitrate with a minimal yield of nitrite. Through a facile liquid-phase deposition process, the loading amount of nickel nanoparticles can be easily tailored by simply changing the concentration of precursors, and the best copper/nickel molar ratio for nitrate removal performance is 20. At this ratio, the material simultaneously delivers a high nitrate removal rate of 92.2% and low nitrite selectivity of only 2.2% at −0.9 V against the reversible hydrogen electrode, accompanied with superior stability for a continuous NO3RR. This study thus offers an efficient, stable and low-cost copper–nickel bimetallic catalyst for NO3RR.

Photoinduced Cross-Coupling with a Supported Iridium–Nickel Bimetallic Catalyst

Key words covalent organic framework - iridium catalysis - nickel catalysis - photocatalysis - cross-coupling

Developing Iron-Nickel Bimetallic Oxides with Nanocage Structures As High-Performance Bifunctional Catalysts via the Ensemble Effect from Nitrogen Sources.

Metal-air batteries will serve as renewable and ecofriendly energy-storage systems in the future because of their high theoretical energy-density performance and unlimited resources, using oxygen as fuel materials compared with commercial lithium-ion batteries. However, the unsuitable inactive reactions at the air-electrode interface (the oxygen reduction reaction and the oxygen evolution reaction) in the metal-air battery are major challenges. In this study, we report nitrogen (N)-doped iron (Fe) and nickel (Ni) bimetallic catalysts with a hollow structure (Fe-Ni nanocage) as outstanding bifunctional catalysts, which have not been reported previously. The open structure in the catalysts simultaneously has an active inner cavity and an outer shell; catalysts have a high active surface area, resulting in remarkable electrochemical performance. Furthermore, the electron transfer phenomenon due to the "ensemble effect" generates a higher catalyst activation. Nitrogen has a higher electronegativity than the metal cations, so doped nitrogen sources draw the electron into iron and nickel cations, and the deprived oxidation state of the metal cations accelerates the electrocatalytic performance.

Structure-controlled growth of vertically-aligned carbon nanotube forests using iron–nickel bimetallic catalysts

A Fe–Ni catalyst prepared via mechanical alloying using a CCVD system for VACNT growth and its advanced characterization are presented.

Synthesis of graphene nanosheets by emitted black carbon and its sustainable applications

Abstract An approach has been made to convert Black carbon (BC) into two-dimensional novel Graphene nanosheets (GNS) by simpler approach carried-out for the conversion of facile using Black carbon (BC) by purging Catalytic-Chemical vapor deposition (C-CVD) technique. Iron and Nickel (Fe-Ni) bi-metallic catalyst supports 92 % GNS yield, as opposed to other lower yields method and using less-cost effective catalysts. The synthesized GNS is employed for the photo-catalytic degradation of Rhodamine-B (RhB) in addition with Janus Green (JG) in a single step which resolves two organic dye contaminant issues with non-toxic molecular intermediates at the same time, under influence of solar light exposure. The Anti-bacterial properties activity of selected gram-negative and gram-positive and fungal activity was systematically achieved. GNS is highly stable and shows less toxicity against the Human embryonic kidney (HEK-293) cell lines and safer to the environment. Furthermore, regeneration efficiency of GNS, which was still at its higher value even after five consecutive cycles of recycling testing, GNS can perform the quite superior result than the earlier reported studies on structurally altered graphene and other graphitic based materials. The fusion of these investigations introduces a new course, promising way to achieve the new era in environmental remediation and utilization of these materials in future eco-friendly approaches.

Highly Efficient Polydopamine-coated Poly(methyl methacrylate) Nanofiber Supported Platinum⁻nickel Bimetallic Catalyst for Formaldehyde Oxidation at Room Temperature.

We fabricated one fibrous-membrane type of flexible and lightweight supported catalyst via loading platinum–nickel nanoparticles (PtNi NPs) directly on the polydopamine-coated polymethylmethacrylate electrospun-fibers (PMMA@PDA). The polymer support with the PDA layer provided numerous active sites, leading to well-monodispersed and sized PtNi NPs on the nanofibers. Through the rational design of PtNi NPs, the resultant catalyst system exhibited 90% conversion for decomposing HCHO (10 ppm) at room temperature with only a low dosage (0.02 g), retaining the high activity for 100 h. This superior catalytic performance stems from the formate oxidation, which was the key intermediate during HCHO decomposition, and was promoted by the existence of a sufficient Pt–OH–Ni interface in the PtNi NPs with an appropriate Pt/Ni ratio of 1:5. Such tailored Pt-based nanoparticles ideally work together with the polymer nanofibers as a support for catalytic reaction. Compared with classical catalysts, our system can handle a comparable efficiency with much lower air resistance and remarkably lower dosage. Furthermore, the membrane-like morphology provides easy handling and minimizes the leaching of catalyst nanoparticles.

Fe–Ni–MCM-41 Catalysts for Hydrogen-Rich Syngas Production from Waste Plastics by Pyrolysis–Catalytic Steam Reforming

A two-stage pyrolysis–catalytic steam reforming process was used with mesoporous MCM-41 supported iron and nickel bimetallic catalysts for hydrogen-rich syngas production from a simulated mixture of waste plastics. Different Fe/Ni weight ratios (00:20, 05:15, 10:10, 05:15, and 20:00) have been investigated to determine the influence on hydrogen production. The results showed that the presence of Fe and Ni together produced a synergistic enhancement of the total gas yield and hydrogen and carbon monoxide production. For example, the (10:10) Fe–Ni–MCM-41 catalyst produced the highest gas yield of 95 wt %, the highest H2 production of 46.1 mmol H2 g–1plastic, and the highest CO production at 31.8 mm g–1plastic. The (10:10) Fe–Ni–MCM-41 catalyst produced a volumetric hydrogen concentration of 46.7 vol %, and carbon monoxide was 32.2 vol %. The (10:10) Fe–Ni–MCM-41 catalyst also showed the lowest carbon deposition on the catalyst. The carbon deposits were mainly of the amorphous encapsulating type for the iron...

Rhodium–Nickel Bimetallic Catalyst for Hydrogenation of Phthalates

Key words hydrogenation - rhodium catalysis - nickel catalysis - nanoparticles - plasticizers - cyclohexane-dicarboxylates

Vapor phase hydrogenolysis of glycerol to 1,2-propanediol over γ-Al2O3 supported copper or nickel monometallic and copper–nickel bimetallic catalysts

Vapor phase hydrogenolysis of glycerol was investigated over γ-Al2O3 supported copper or nickel monometallic and copper–nickel bimetallic catalysts prepared by incipient wetness impregnation method. Catalytic results demonstrated that bimetallic catalysts were more selective to 1,2-propanediol (1,2-PDO) as compare to monometallic catalysts. Bimetallic copper–nickel phase promoted the selective hydrogenolysis of C–O bond and limited the cleavage of C–C bond which significantly reduced the formation of undesirable products. Very high 1,2-PDO yield of 88% at 98.5% glycerol conversion was achieved over 20 wt% Cu–Ni (1:1)/γ-Al2O3 catalyst at very low hydrogen to glycerol mole ratio of 54.6 and at 220 °C and 0.75 MPa pressure. Superior performance of 20 wt% Cu–Ni (1:1)/γ-Al2O3 catalyst was attributed to strong synergetic interaction due to the formation of copper–nickel bimetallic phase as confirmed by the XRD result. Times-on-stream study and the characterization results of the spent catalyst confirmed the structural stability of the copper–nickel bimetallic phase of 20 wt% Cu–Ni (1:1)/γ-Al2O3 catalyst and negligible carbon deposition (0.03 mmol carbon gcat−1 h−1) on the catalyst after prolonged contact under hydrogen environment.

Promotional effect of Au on reduction of Ni(II) to form Au–Ni alloy catalysts for hydrogenolysis of benzylic alcohols

Gold–nickel bimetallic catalysts were prepared from Au/NiO and Au(OH)3–Ni(OH)2–NiCO3 coprecipitates by treatment with hydrogen. Gold promoted the reduction of Ni(II) to Ni(0) at relatively low temperatures in the range of 100–150°C, which was confirmed by H2-TPR and in situ XAFS measurements, whereas NiO without Au was not fully reduced even at 300°C. The obtained catalysts were characterized by XRD, HAADF-STEM, XAFS, and 197Au Mössbauer, and these analyses revealed the formation of Au–Ni alloy components in the obtained catalysts. Au existed as Au nanoparticles together with Au–Ni alloy components in Au–Ni-1 prepared from Au/NiO by H2 treatment. When Au(OH)3–Ni(OH)2–NiCO3 was treated in a flow of H2 to produce Au–Ni-2, the formation of Au NPs was not clearly observed, thereby meaning that Au atoms were highly dispersed as a single atom and/or small clusters in the obtained catalysts. Moreover, most of the Au atoms were alloyed with Ni atoms for Au–Ni-2. The obtained Au–Ni-1 and Au–Ni-2 exhibited superior catalytic activities for the selective hydrogenolysis of benzylic alcohols into alkylbenzene derivatives in terms of reaction rates normalized by catalyst surface area. Accordingly, Au–Ni-1 and Au–Ni-2 recorded the reaction rates of 4.79 and 9.79mmolL−1h−1m−2, respectively. These values were greater than that obtained for Raney Ni (0.14mmolL−1h−1m−2). In addition, Au–Ni-2, which contains higher Au–Ni alloy content, showed greater reaction rates when compared to Au–Ni-1. Since Au/TiO2 showed poor catalytic activity for the hydrogenolysis, Au–Ni alloy enhanced the catalytic activities of Ni(0).

Ni and Rh[sbnd]Ni catalysts supported on Zeolites L for hydrogen and syngas production by biogas reforming processes

This study examined the use of three different Zeolites L as catalyst support for biogas valorisation – a renewable resource – through reforming processes. These aluminosilicates are characterised by their high surface areas, affinity for CO2, and thermal stability, which makes them an interesting and promising support for reforming reactions at high temperature. Three nickel monometallic and their homologous rhodium–nickel bimetallic catalysts were prepared by the incipient wetness impregnation method for each type of Zeolite L. Significant physicochemical differences between the Zeolites L and catalysts were noticed by the characterisation using scanning electron microscope (SEM), transmission electron microscope (TEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), H2 chemisorption, N2 physisorption, temperature programmed reduction (TPR) X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The catalysts were tested in dry reforming (DR), steam reforming (SR) with steam to carbon (S/C) ratio of 1.0 and 2.0; oxidative reforming (OR) at O2/CH4=0.25; and tri-reforming (TR) with S/C ratio of 1.0 and O2/CH4=0.25. For all the experiments, a synthetic biogas, which consisted of 60% CH4 and 40% CO2 (vol.), was fed to a fixed bed reactor system at 1073K and atmospheric pressure. The same experimental conditions and reactions were studied in previous works of the authors, in which γ-Al2O3 was used as a catalyst support. Thus, this work allows comparing the achieved activities by the tested catalysts supported on those different supports. Among the processes studied, for the biogas SR at S/C=1.0 and TR processes, H2/CO ratios near to 2.0 were obtained, which is an appropriate ratio for the Fischer–Tropsch synthesis (FTS). In the case of the catalysts tested, the Rhodium (Rh) incorporation improved their activity. RhNi catalyst based on Zeolite L (30–60nm) is the most active catalyst for hydrogen generation.

Study of Cu–Ni/SiO2 catalyst prepared from a novel precursor, [Cu(H2O)6][Ni(dipic)2].2H2O/SiO2, for water gas shift reaction

Silica-supported copper–nickel bimetallic catalyst was prepared from [Cu(H2O)6][Ni(dipic)2].2H2O/SiO2 precursor. The cationic–anionic complex, [Cu(H2O)6][Ni(dipic)2].2H2O, was prepared from the reaction of (NH4)2[Ni(dipic)2] with Cu(NO3)2.3H2O in water and characterized by elemental analysis, conductometric and various spectroscopy techniques such as FT-IR, UV–vis and atomic absorption. The physicochemical characteristics of both precursor and calcined catalyst were carried out using X-ray diffraction, thermal analysis methods (TGA and DSC), FT-infrared, scanning electron microscopy and BET specific surface area. The catalyst was evaluated for water gas shift reaction. When the Cu–Ni/SiO2 catalyst was used for water gas shift reaction at 300°C and atmospheric pressure, the CO conversion and CO2 selectivity were about 97.83% and 98.67%, respectively, showing higher activity and selectivity than the reference catalyst prepared by impregnation conventional method.

Liquid Phase Hydrodechlorination of Chlorobenzene over Bimetallic Supported Zirconia Catalyst

Mesoporous zirconia was prepared by the surfactant-assisted route, using cetyltrimethylammonium bromide as cationic surfactant. The synthesized zirconia was employed as support for copper and nickel bimetallic catalysts in the hydrodehalogenation reaction of chlorobenzenes and substituted chlorobenzenes at room temperature. The catalysts were characterized by nitrogen adsorption–desorption, X-ray powder diffraction, Fourier-transfer infrared spectroscopy (FTIR), transmittance electron micrograph (TEM), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The nitrogen adsorption–desorption studies revealed that the modified samples retain the mesoporosity. TEM studies showed uniform distribution of metals having 5–10 nm particles size on the support surface. The bimetallic catalyst exhibited a higher H2 chemisorption capacity relative to monometallic catalysts. For catalytic hydrodehalogenation of chlorobenzene, bimetallic...

Heterogeneous Supported Catalysts for Butadiene Polymerization: The Effect of Calcination Temperature and Solvent

The polymerization of butadiene was studied using heterogeneous cobalt nickel (oxide) bimetallic catalyst. The prepared catalyst was subjected to calcination at different temperatures. This treatment results in the formation of different phases with multiple oxidation states. The characterization of the catalyst was carried out by XRD, SEM, EDX, TGA, FTIR and TPR/TPD. The catalytic activity was studied for the polymerization of butadiene gas in toluene, n-hexane and ethanol in a Parr reactor system. The products obtained, were characterized by FTIR, GC/MS, 1 H and 13 C NMR spectroscopy, Laser Light Scattering (LLS) and GPC. The best activity was achieved on the catalyst sample calcined at 1173 K in ethanol solvent. The product contains aliphatic and aromatic carbonyl compounds and polybutadiene terminated by OH group. The GPC and LLS studies indicates that polydispersity of the products are in the narrow range and high molecular weight product. The study reflects that the catalytic reaction conditions, the calcinations temperatures which control the oxidation state, phase of the catalyst and stability of the catalyst are mainly responsible for the change in products selectivity.

Improved resistance against coke deposition of titania supported cobalt and nickel bimetallic catalysts for carbon dioxide reforming of methane

The catalytic behavior of bi-metallic Co–Ni/TiO2 catalysts for CO2 reforming of CH4 to synthesis gas was investigated under atmospheric pressure with a particular attention to carbon deposition. The catalysts with optimized Co/Ni ratios showed high catalytic stability towards the reaction with very little amount of deposited carbon at a wide range of reaction temperature (773–1123 K). The results suggest that adjusting of composition of the active metals (Co and Ni) can kinetically control the elementary steps (formation of carbon species and its removal by oxygen species) of CH4/CO2 reaction.

Titania-supported cobalt and nickel bimetallic catalysts for carbon dioxide reforming of methane

Titania-supported cobalt and nickel bimetallic catalysts were investigated for CO 2 reforming of methane to synthesis gas at 1023 K under ambient pressure. Bimetallic Co–Ni/TiO 2 catalysts with an appropriate Co/Ni ratio showed highly stable activities without carbon deposition. Whereas the monometallic Co/TiO 2 catalyst deactivated rapidly because of the oxidation of metal, 10 mol% substitution of nickel for cobalt suppressed the oxidation of metal, providing a high catalytic stability. However, the catalysts with excess nickel content (>80 mol%) underwent carbon formation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that a homogeneous alloy of cobalt and nickel was formed from bulk to the surface by the H 2 reduction, and the alloy was stable during reforming. The advantages of the bimetallic catalysts are high resistance to undesirable metal oxidation and coking, through the control of reactions between CH 4 and CO 2.

Carbon monoxide hydrogenation over various titania-supported Ru–Ni bimetallic catalysts

A series of titania-supported ruthenium–nickel bimetallic catalysts, with total metal loading of ∼4.5 wt.% in each, was prepared and characterized for various physico-chemical properties. The hydrogenation of carbon monoxide was studied over these catalysts in the temperature range of 483–493 K, weight hourly space velocity of 1.5 h −1, H 2/CO mole ratio of 2, and at atmospheric pressure. The effects of ruthenium loading and pretreatment procedures on the hydrogenation activities of these catalysts and product selectivities were studied. The catalyst containing 3.6 wt.% Ni and 0.82 wt.% Ru produced highest proportion of C 5+ hydrocarbons (60 wt.%). High olefin selectivities (40 wt.% for C 2 = and 93 wt.% for C 3 =, respectively) were observed with catalysts containing only ruthenium (5 wt.%). The effect of metal–metal interaction in the bimetallic catalysts on product selectivities was also studied.

99/01978 Partial oxidation of methane to syngas over Pt/A 2O 3 and Pt/CeO 2/Al 2O 3: Yan, Q.-G. et al. Gaodeng Xuexiao Huaxue Xuebao, 1998, 19, (8), 1300–1303. (In Chinese)

Partial oxidation of methane to synthesis gas was carried out using supported iridium–nickel bimetallic catalysts, in order to reduce loading levels of iridium and nickel, and to avoid carbon deposition on nickel-based catalysts by adding iridium. The performance of supported iridium–nickel bimetallic catalysts in synthesis gas formation depended strongly upon the support materials. La2O3 gave the best performance among the support materials tested. Ir(0.25 wt%)–Ni(0.5 wt%)/La2O3 afforded 36% conversion of methane (CH4/O2=5) to give CO and H2 with the selectivities of above 90% at 800°C, and those at 600°C were 25.3% conversion of methane and CO and H2 selectivities of about 80%, respectively. Reduced monometallic Ir(0.25 wt%)/La2O3 and Ni(0.5 wt%)/La2O3 catalysts did not produce synthesis gas at 600°C. A higher conversion of methane was obtained by synergistic effects. The product concentrations of CO, H2, and CO2, and CH4 conversion were maintained in high values, even increasing the space velocity of feed gas over Ir–Ni/La2O3 catalyst, indicating that rapid reaction takes place. As a by-product, a small amount of carbon deposition was observed, but carbon formation decreased with increasing the space velocity. On the other hand, with reduced monometallic Ni(10 wt%)/La2O3 catalyst, yield of synthesis gas and carbon decreased with increasing the space velocity.