Ni-Cu Bimetallic Catalysts Research Articles

Development of Robust CuNi Bimetallic Catalysts for Selective Hydrogenation of Furfural to Furfuryl Alcohol under Mild Conditions

Furfuryl alcohol represents a pivotal intermediate in the high-value utilization of renewable furfural, derived from agricultural residues. The industrial-scale hydrogenation of furfural to furfuryl alcohol typically employs Cu-based catalysts, but their limited catalytic activity necessitates high-temperature and high-pressure conditions. Here, we develop robust CuNi bimetallic catalysts through direct calcination of dried sol–gel precursors under H2 atmosphere, enabling the complete conversion of furfural to furfuryl alcohol under mild conditions. By adjusting the calcination atmosphere and introducing small amounts of Ni, we achieve the formation of highly dispersed, ultrasmall Cu nanoparticles, resulting in a significant enhancement of the catalytic activity. The optimized 0.5%Ni-10%Cu/SiO2-CA(H2) catalyst demonstrates superior catalytic performance, achieving 99.4% of furfural conversion and 99.9% of furfuryl alcohol selectivity, respectively, at 55 °C under 2 MPa H2, outperforming previously reported Cu-based catalysts. The excellent performance of CuNi bimetallic catalysts can be attributed to the highly dispersed Cu nanoparticles and the synergistic effect between Cu and Ni for H2 activation. This research contributes to the rational design of Cu-based catalysts for the selective hydrogenation of furfural.

SBA-15 supported Ni-Cu catalysts for hydrodeoxygenation of m-cresol to toluene.

Amidst concerns over fossil fuel dependency and environmental sustainability, the utilization of biomass-derived aromatic compounds emerges as a viable solution across diverse industries. In this scheme, the conversion of biomass involves pyrolysis, followed by a hydrodeoxygenation (HDO) step to reduce the oxygen content of pyrolysis oils and stabilize the end products including aromatics. In this study, we explored the properties of size controlled NiCu bimetallic catalysts supported on ordered mesoporous silica (SBA-15) for the catalytic gas-phase HDO of m-cresol, a lignin model compound. We compared their performances with monometallic Ni and Cu catalysts. The prepared catalysts contained varying Ni to Cu ratios and featured an average particle size of approximately 2 nm. The catalytic tests revealed that the introduction of Cu alongside Ni enhanced the selectivity for the direct deoxygenation (DDO) pathway, yielding toluene as the primary product. Optimal performance was observed with a catalyst composition comprising 5wt.% Ni and 5wr.% Cu, achieving 85% selectivity to toluene. Further increasing the Cu content improved turnover frequency (TOF) values, but reduced DDO selectivity. These findings underscore the importance of catalyst design in facilitating biomass-derived compound transformations and offer insights into optimizing catalyst composition for more selective HDO reactions.

Highly efficient and selective hydrogenation of furfural to furfuryl alcohol and cyclopentanone over Cu-Ni bimetallic Catalysts: The crucial role of CuNi alloys and Cu+ species

The selective hydrogenation of furfural derived from biomass is of significant importance in the synthesis of valuable chemical compounds. In this work, Cu-Ni bimetallic catalysts with varying metal ratios were effectively synthesized using the urea deposition method and employed in catalytic hydrogenation of furfural (FA) to furfuryl alcohol (FOL) and cyclopentanone (CPO) in different solvents. The study revealed that the synergistic interaction between Cu and Ni favors the formation of CuNi alloys, thereby facilitating the reduction of CuO and NiO and resulting in larger amount of metallic species (Cu0/+ and Ni0), and promoting the formation of highly dispersed nanoparticles. Moreover, the formed Cu+ species can serve as Lewis acid sites and improve the adsorption of polarized C = O, thus significantly enhancing the selectivity to FOL. More importantly, the cooperation between Cu+ species and water can promote the aqueous-phase hydrogenation-rearrangement (AP-HR) of FA to CPO. Also, in-situ/on-line DRIFTS shows that Cu3Ni1/SiO2 preferentially adsorbs and activates C = O and prefers to form 4-hydroxy-2-cyclopentenone (HCP), which is the key intermediate to form CPO. DFT calculations agree with the in-situ/on-line DRIFTS, showing that Cu3Ni1 (111) crystal surface with the lowest d-band center and the strongest electronic effects presents the highest adsorption energies of H2, H2O, and FA, the lowest adsorption energies of H*, FOL, and CPO, and the lowest energy barriers of Piancatelli rearrangement of FOL to HCP. Under the optimum conditions, Cu3Ni1/SiO2 gives 99.9 % yield to FOL at 333 K in isopropanol and 96.7 % yield to CPO at 413 K in water. The low cost and high activity of Cu3Ni1/SiO2 make it a potential catalyst for the green production of FOL and CPO in industry.

Highly Efficient and Selective Hydrogenation of Biomass-Derived Furfural Using Interface-Active Rice Husk-Based Porous Carbon-Supported NiCu Alloy Catalysts.

A series of bimetallic NixCuy catalysts with different metal molar ratios, supported on nitric acid modified rice husk-based porous carbon (RHPC), were prepared using a simple impregnation method for the liquid-phase hydrogenation of furfural (FFA) to tetrahydrofurfuryl alcohol (THFA). The Ni2Cu1/RHPC catalyst, with an average metal particle size of 9.3 nm, exhibits excellent catalytic performance for the selective hydrogenation of FFA to THFA. The 100% conversion of FFA and the 99% selectivity to THFA were obtained under mild reaction conditions (50 °C, 1 MPa, 1 h), using water as a green reaction solvent. The synergistic effect of NiCu alloy ensures the high catalytic activity. The acid sites and oxygen-containing functional groups on the surface of the modified RHPC can enhance the selectivity of THFA. The Ni2Cu1/RHPC catalyst offers good cyclability and regenerability. The current work proposes a simple method for preparing an NiCu bimetallic catalyst. The catalyst exhibits excellent performance in the catalytic hydrogenation of furfural to tetrahydrofurfuryl alcohol, which broadens the application of non-noble metal bimetallic nanocatalysts in the catalytic hydrogenation of furfural.

Elucidating the structure-activity relationship of the bimetallic Ni-Cu catalysts for CO2 hydrogenation

The conversion of carbon dioxide (CO2) into high-value products plays a critical role in mitigating atmospheric CO2 levels. Recently, low-cost Ni-based catalysts have been garnering attention due to their exceptional hydrogenation ability. This study focuses on the synthesis of Cu-Ni bimetallic catalysts for CO2 hydrogenation and the systematic evaluation of the relationship between structural evolution and catalytic activity. Through investigation of the selectivity regulation of Cu on Ni-based catalysts, it was discovered that the addition of Cu led to a significant shift in catalytic activity and selectivity. Specifically, the Cu addition transitioned the reaction from being CH4-selective to CO-selective. Moreover, the introduction of Cu preferentially generated a Cu-Ni alloy during the reaction, which resulted in a significant number of *CO species with strong adsorption strength at the interface. Consequently, the subsequent hydrogenation of these *CO species was impeded, rendering the catalyst CO-selective.

Electrochemical conversion of 5-hydroxymethylfurfural over CuNi bimetallic catalysts: the synergistic effect of interfacial active sites

ECO of HMF to FDCA and ECR to BHMF with high yield have been studied on CuNi-based bimetallic catalysts. The presence of the Cu–O–Ni interfacial area was beneficial for promoting the catalytic performance in ECO.

Balancing act: influence of Cu content in NiCu/C catalysts for methane decomposition.

Thermal catalytic decomposition of methane is an innovative pathway to produce CO2-free hydrogen from natural gas. We investigated the role of Cu content in carbon-supported bimetallic NiCu catalysts. A graphitic carbon material was used as a model support, and we combined operando methane decomposition experiments in a thermogravimetric analyzer with in situ electron microscopy measurements. The carbon yield was maximum with around 30% Cu in the nanoparticles. Adding more Cu drastically lowered the carbon solubility in the metal nanoparticles, which lowered the initial reaction rate and overall carbon yield. In situ TEM measurements showed that the addition of Cu to the catalysts strongly influenced the metal nanoparticle shape and size during carbon growth, and the growth mode. NiCu particles were larger, remained spherical and facilitated steady CNF growth. In contrast, pure Ni nanoparticles fluctuated in shape, sometimes fragmented, and showed stuttering CNF growth. This was ascribed to fluctuating coverage of part of the Ni nanoparticle surface with amorphous carbon, which increased the chance of total encapsulation and hence deactivation of the individual Ni nanoparticles. This supports a picture where balancing the carbon supply, transport, and nucleation of amorphous and crystalline carbon is crucial. Our results also highlight the importance of combining statistically relevant measurements with microscopic information on individual nanoparticles to understand overall catalytic trends from the combined behavior of individual catalyst nanoparticles.

Effect of the physicochemical properties of bimetallic Ni-Cu catalysts for hydrogenation/hydrogenolysis of HMF varying the synthesis method

The evident necessity to transition away from a reliance on fossil resources implies the need to produce high-value-added chemicals from non-conventional sources, such as lignocellulosic biomass. The cellulosic fraction of this resource can be converted into 5-hydroxymethylfurfural (HMF), which can be further transformed to 2,5-bis(hydroxymethyl)furan (BHMF), a polymeric precursor, or 2,5-dimethylfuran (DMF), serving as a substitute or additive of conventional gasoline. This work investigates the effect of the synthesis method of the Ni-Cu/ZrO2 catalyst on the conversion of HMF to BHMF or DMF. The preparation process exerts influence on the dispersion of metals, the acidity of the catalyst, and the interaction of Ni-Cu. Consequently, product selectivity varied depending on the catalyst preparation method, with BHMF being the primary product when the catalyst was prepared through wet impregnation and DMF when precipitation was the chosen synthesis method. Concretely, a BHMF yield of 60% yield was achieved at 150 °C with the impregnated catalyst, while a 65% yield was obtained for DMF when employing the precipitation-prepared catalyst. Furthermore, a noticeable effect of the temperature on product selectivity was also detected.

Nickel oxide/copper nanocluster anchored in carbon-nitride nanosheets realizing ultrahigh stability and broad potential range for zero-gap membrane flow reactor towards CO2-into-CO electroreduction

CO2 electrochemical reduction is a sustainable approach to achieve chemical fixation of CO2 and storage of renewable energy. However, the catalyst which has the ability of mediating CO2 to a single product with a relatively high current density is highly demand. Herein, we reported a metallic nitrogen-carbon catalyst based on two kinds of metal phthalocyanines by a facile synthesis method. The synergistic effect of Cu and Ni and the active sites of nickel oxide/copper nanocluster endow the catalyst excellent performance towards CO2-into-CO electroreduction. Typically, the Cu-Ni bimetallic catalyst achieves high selectivity (85.2 %) at positive potential (−0.72 VRHE), with the stability of current density and product selectivity beyond 72 h. The volume ratio of CO/H2 can be effectively tuned (from 2:1, 1:1 to 1:2) by controlling the electrolysis potential, which is promising for synthesis gas in the Fischer-Tropsch reactions and methanol synthesis. Furthermore, the advantages are further amplified by applying it to zero-gap membrane flow reactor, which can enhance the selectivity over 90 % at a broad potential range (−2.5 ∼ −2.7 V) and achieve an current density of 9-fold of H-type cell. Our work proves a way for optimizing the CO2 electrocatalyst and electrolyzers.

Anti-coking Cu-Ni bimetallic catalyst for hydrogen production: Thermodynamic and experimental study of methanol autothermal reforming

Autothermal reforming has emerged as a promising route for hydrogen production from bio-methanol, offering a balance between hydrogen production and the energy demand of the process. To address the low catalytic performance of non-precious metal catalysts, one of the approaches is to introduce a second metal. In this work, a series of Cu-Ni bimetallic catalysts derived from Ca-Al hydrotalcite-like compounds were prepared by the urea hydrolysis method combined with hydrothermal treatment, featuring well-dispersion with a size of 3-5 nm. The electron redistribution triggered by the incorporation of Cu enhances the absorption of methanol at the electron-poor surface, leading to maintained catalytic activity at 450°C for 96 hours with few carbon-deposition observed for methanol autothermal reforming. The boundary conditions of the thermal-neutrality system are analyzed by thermodynamic calculations and similar trends to the simulation results were also obtained from experiments.

Electrocatalytic reduction of furfural for selective preparation of 2-methylfuran over a sandwich-structured Ni-Cu bimetallic catalyst

Electrocatalytic reduction of furfural for selective preparation of 2-methylfuran over a sandwich-structured Ni-Cu bimetallic catalyst

Design of Ni-Cu supported halloysite for enhanced degradation of chitosan

Bimetallic Ni-Cu catalysts supported on halloysite nanotubes with different metal contents (Hal-Ni80Cu20, Hal-Ni70Cu30, Hal-Ni42Cu58) were prepared and employed in the catalytic degradation of chitosan (CS). The relationship between catalytic performances of the catalysts with the different metal contents were studied. The highest catalytic activity was reported for Hal-Ni42Cu58 due to the higher proportion of the active Cu2+ in the catalytic degradation. Furthermore in Hal-Ni42Cu58, CuO persisted dominantly with Ni(OH)2 as compared to Hal-Ni80Cu20 where Cu(OH)2 was also available. Overall, the bimetallic-supported Hal catalysts displayed better catalytic activities than monometallic supported catalysts due to the synergistic effect between the metals.

Selective aqueous-phase hydrogenation of furfural to cyclopentanol over Ni-based CNT catalysts

Cyclopentanol (CPL) was an eco-friendly solvent as well as important platform chemical which could be generated from biomass-derived furfural (FFA). In this paper, A series of Ni, Cu, Mo, Co bimetallic catalysts with different metals loadings supported on Carbon nanotubes (CNT) were synthesized by an impregnation method for aqueous-phase hydrogenation of FFA to obtain CPL. Various effects of reaction parameters such as, reaction solvent, reaction temperature, reaction time, and different loading amount of Ni over bimetallic Ni-based CNT catalysts were fully investigated. Among the catalysts studied, (15 + 5) wt% NiCu/CNT catalysts showed high conversion of FFA and 88% selectivity towards CPL in water and 96% selectivity towards acetal in methanol at mild condition of 160℃, 2 MPa hydrogen and 4 h reaction time. NiCu bimetallic synergistic effect was interpreted through H2-TPR and NH3-TPD measurement and a possible pathway was proposed. The features of the CNT supported catalysts were investigated via XRD, XPS, TEM, H2-TPR and NH3-TPD. The Ni and bimetallic NiCu catalysts synthesized in this work were inexpensive and simple, which made them a promising candidate for the conversion of biomass-derived FFA to CPL.

Bimetallic NiCu catalysts supported on a Metal-Organic framework for Non-oxidative ethanol dehydrogenation

Non-oxidative ethanol dehydrogenation is a promising route to produce acetaldehyde and hydrogen from sustainable feedstock. Bimetallic NiCu catalysts have shown high efficiency and selectivity for this chemical transformation. In this study, we leverage the high porosity and uniform catalyst deposition sites on a Zr-based metal–organic framework (MOF) catalyst support, NU-1000, to understand how the changes in Cu:Ni ratio affects the reactivity for non-oxidative ethanol dehydrogenation. We found that increasing the Ni2+ concentration significantly reduces the activation energy of the reaction due to the role of Ni2+ in suppressing the onset of Cu reduction. This study illustrates how MOFs can be used as catalyst supports to fine-tune the catalyst compositions and understand their effect on the overall catalytic performances.

Production of 2-methyl furan, a promising 2nd generation biofuel, by the vapor phase hydrodeoxygenation of biomass-derived furfural over TiO2 supported Cu[sbnd]Ni bimetallic catalysts

This work investigates the vapor phase hydrodeoxygenation (HDO) of FFR to 2-MeF over a series of TiO2-supported mono and bimetallic Cu-Ni catalysts with a fixed Cu content (10 wt%) and varying Ni content (0–20 wt%). The catalysts were synthesized through a simple wet impregnation method, and their properties were studied in depth through an array of analytical techniques such as X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), Scanning Electron Microscopy (SEM), N2-physisorption, Raman spectroscopy, and NH3-temperature programmed desorption (TPD). The catalyst characterizations revealed that the addition of Ni in progressively larger amounts resulted in greater dispersion of Cu species and an increase in the surface area & porosity of the bimetallic catalysts, arising from the strong interactions between NiO and CuO species. Detailed studies were carried out to evaluate the effect of various process parameters such as Ni content, temperature, and contact time on the selectivity of 2-MeF. Ni content of the bimetallic catalysts and temperature played a significant role in product distribution than the contact time. The bimetallic catalyst with the composition 10%Cu-10%Ni was observed to be the optimum, providing a FFR conversion of 100%, and a 2-MeF selectivity of 84.5% at 200 °C, H2/FFR molar ratio = 15, and WHSV = 0.87 gFFR h−1 gcatalayst−1 after 6 h time-on-stream (TOS). During the long-term catalytic activity evaluation, the catalyst exhibited a stable 100% FFR conversion and ∼ 85% selectivity towards 2-MeF over a period of 12 h. Even after a period of 15 h, conversion and selectivity values remained >90% and 70%, respectively.

Selective hydrogenation reactions of 5-hydroxymethylfurfural over Cu and Ni catalysts in water: Effect of Cu and Ni combination and the reagent purity

This work studies the catalytic properties of Cu and Ni catalysts, as well as the effect of Cu and Ni combination on the activity and selectivity during the aqueous phase hydrogenation of 5-hydroxymethylfurfural (HMF) in a batch reactor, at 60 °C under 30 bar H2. Catalysts with different Ni/Cu ratios (10 wt%) were synthesized over a high surface area graphite (HSAG). While Ni provides the bimetallic catalyst the capacity for hydrogenation of CO and CC groups, Cu contributes to suppress the hydrogenation of the furan ring, reaching a 99% of selectivity to the partial hydrogenated product, 2,5-di-hydroxymethylfuran (DHMF), over 5Cu5Ni/HSAG. The increase of reaction temperature (180 °C) conduced to the hydrolytic ring-opening and rearrangement of HMF. Under such reaction conditions, monometallic Ni afforded the highest yield towards the hydrogenative rearrangement product, 3-hydroxymethylcyclopentanone (81%). However, Cu and CuNi bimetallic catalysts were less reactive to the ring-rearrangement reaction and showed higher tendency to deactivation, especially when the HMF supplier contain sulfur impurities.

Development and Testing of Ni-Cu Bimetallic Catalysts for Effective Syngas Production via Low-Temperature Methane Steam Reforming

In the present work, novel bi-metallic catalysts for syngas production at low temperature steam reforming are developed, characterised and tested. Steam methane reforming by using bi-metallic Ni-Cu catalysts found to balance the product of CO to CO2 ratios, while affected the water gas shift reaction by increasing the hydrogen selectivity up to 600°C. The addition of different amounts of Cu (3, 5, 7, 10 wt%) to the Ni catalyst for methane steam reforming showed different reactivity trends. One of the major outcomes of this work is the maximum load capacity of Cu (5wt.%Cu) to maintain the reactivity. For comparison purposes, mono-metallic catalysts of Cu and Ni were developed and tested along with the bi-metallic ones. The activity of the reaction decreased by doping more than 5wt.%Cu which affected the amount of hydrogen produced. This is related to the possible limited number of available sites required for hydrogen adsorption to maintain the reaction of methane steam reforming. Another important outcome of this work is the bi-metallic Ni-Cu catalysts did not decrease the amount of carbon formation.

Sorption enhanced aqueous phase reforming of biodiesel byproduct glycerol for hydrogen production over Cu-Ni bimetallic catalysts supported on gelatinous MgO

Hydrogen production from sorption enhanced aqueous phase reforming (APR) of biodiesel byproduct glycerol was studied by Ni-based monometallic and bimetallic catalysts supported on gelatinous MgO supports. Compared with Ni-based monometallic catalyst, the H2 selectivity and glycerol conversion of the Cu–Ni bimetallic catalyst were found to be increased more than 3% and 30%, respectively. Meanwhile, higher reaction temperature was found to have higher H2 yield with lower H2 selectivity. The H2 yield using the catalyst with gelatinous MgO support was 1.25 times higher than that of calcined support. Through in-situ CO2 capture, the addition of CaO to the Cu–Ni bimetallic catalyst increased more than 58.3% and 14.4% of the H2 yield and selectivity, respectively. An analysis about liquid product component indicate that the presence of CaO promote the further cleavage of the C–C bond, which further increased the conversion of glycerol. Furthermore, it was found that the presence of CaO could also improve the stability of the catalyst through the control experiments.

A bimetallic strategy to tailoring the surface formation energy and d-band center of Ni-based catalyst for efficient and stable catalytic hydrogenation of dioctyl phthalate

Hydrogenation of dioctyl phthalate (DOP) is an effective strategy to synthesize cyclohexane-1,2-dioctyl phthalate (CDP), an environmentally friendly plasticizer. Many catalysts have already been developed to achieve the hydrogenation of DOP. However, due to the stability of their aromatic rings, the high costs of noble metal catalysts, and the harsh reaction conditions, the fabrication of non-noble metal catalysts with high activity and stability is still challenging. In this work, we report a bimetallic strategy built on the confinement effect to prepare a Ni2.5Cu0.5Al1 bimetallic catalyst using Ni-Cu hydrotalcite as the precursor. Results show that DOP conversion and selectivity of CDP could both reach 99%; also, the suggested bimetallic catalyst exhibits excellent stability under harsh reaction conditions, e.g., the catalyst can be recycled up to 9 times with no change in conversion and selectivity. Certain characterizations and theoretical calculations show that introduction of an appropriate amount of Cu can reduce the surface formation energy and d-band center, which can simultaneously improve the activity and stability of the Ni-based catalysts. Therefore, the proposed Ni-Cu bimetallic catalyst is an attractive option for the synthesis of environmentally friendly plasticizers by DOP hydrogenation.

Screening of Nickel and Platinum Catalysts for Glycerol Conversion to Gas Products in Hydrothermal Media

The production of low-carbon gaseous fuels from biomass has the potential to reduce greenhouse gas emissions and promote energy sustainability, stability and affordability around the world. Glycerol, a large-volume by-product of biodiesel production, is a potential feedstock for the production of low-carbon energy vectors. In this present work, an aqueous solution of pure glycerol was reacted under hydrothermal conditions using a total of 10 types of heterogeneous catalysts to evaluate its conversion to gas products (hydrogen, methane, CO, CO2 and C2–C4 hydrocarbon gases). Two bimetallic Ni-Fe and Ni-Cu catalysts, three Pt-based catalysts and physical mixtures of the five catalysts were tested. The reactions were carried out in a batch reactor for 1 h reaction time, using a 9:1 mass ratio of water/glycerol (10 wt%) and the reaction temperatures ranged between 250–350 °C using and without using 1 g of catalyst. The effects of the catalysts and reaction conditions on the conversion of glycerol in terms of carbon and hydrogen gasification efficiencies, selectivity and yields of components in the gas products were investigated. CO2 remained the most dominant gas product in all experiments. The results indicated that increasing the reaction temperature favoured gas formation and both carbon and hydrogen gasification efficiencies. The combination of Ni-Cu and Pt/C catalysts was the most selective catalyst for gas formation at 350 °C, giving carbon gasification efficiency of 95.6 wt%. Individually, the catalyst with the highest hydrogen production was Pt/C and the highest propane yield was obtained with the Ni-Cu bimetallic catalyst. Some catalysts showed good structural stability in hydrothermal media but need improvements towards better yields of desired fuel gases.