Ni-based Bimetallic Catalysts Research Articles

Activity and product distribution in Ni-Co and Ni-Cu catalyst-mediated lignin depolymerization into phenolic substances with isopropanol H-donating solvent.

Lignin, a vital renewable biopolymer, serves as the Earth's primary source of aromatics and carbon. Its depolymerization presents significant potential for producing phenolic fine chemicals. This study assesses promoted Ni-based bimetallic catalysts (Ni-Co/C and Ni-Cu/C) supported on activated carbon in isopropanol for lignin depolymerization, compared to monometallic counterparts. BET, SEM, EDX, and XPS analyses highlight their physicochemical properties and promotional effects, enhancing hydrogenolysis activity and hydrogen transformation. Reaction parameter exploration elucidates the influence on lignin depolymerization, with cobalt and copper as promoters notably increasing conversion and monomer yield. Ni-Co/C exhibits the highest lignin conversion (94.2%) and maximum monomer yield (53.1 wt%) under specified conditions, with lower activation energy (36.1kJ/mol) and higher turnover frequency (31.6h-1) compared to Ni/C. FT-IR, GPC, GC-FID, and GC-MS analyses confirm effective depolymerization, identifying 20 monomer products. Proposed reaction mechanisms underscore the potential of Ni-based bimetallic catalysts for lignin valorization, offering insights into developing efficient catalytic systems for lignin hydrogenolysis. This research enhances understanding and facilitates the development of selective catalytic processes for lignin valorization.

Regenerable Ni-Au/La2O3 catalysts for dry reforming of methane

Dry reforming of methane (DRM) has been proposed as an effective way of converting CO2 and CH4, two major greenhouse gases, into synthesis gas (H2 + CO), a ubiquitous feedstock for various chemical industries. Ni-based bimetallic catalysts have been widely explored as an attractive route to improve DRM activity, selectivity, and stability. In this study, we synthesized LaNiO3 (LNO) and 1% Au-doped LaNiO3 (Au/LaNiO3 – A/LNO) using the modified sol-gel method. The material properties were studied using various characterization techniques, including XRD, BET, H2-TPR, TPO, STEM-HAADF with EDX mapping, Raman spectroscopy, and XPS. Ni nanoparticles with sizes ranging from 10 to 70 nm were successfully exsolved from the perovskite material after reduction at 800 °C. DRM activity of the reduced catalysts was probed from 400 to 800 °C. The Au-doped LNO exhibits significant enhancement in DRM activity at a lower temperature range (600–700 °C) compared to LNO. The A/LNO was also shown to retard coke formation and improve the selectivity for DRM. A computational study using density functional theory (DFT) reveals that the Ni3Au sites have a lower methane activation barrier due to the formation of NiAu alloy and the synergetic effect between Ni and Au.

Zn doped CeO2 supporting Ni–Pt catalysts toward robust hydrogen generation from hydrous hydrazine

Ni-based bimetallic catalysts with noble metals exhibit high activity and selectivity for hydrogen generation from hydrazine monohydrate. However, their poor service durability remains a critical challenge. This study investigated the use of Zn-doped CeO2 as a support for Ni–Pt catalysts to improve their long-term stability. A series of Ni–Pt/Zn-doped-CeO2 catalysts were prepared via a simple co-precipitation and reduction method. Compared to the pristine Ni50Pt50/CeO2 catalyst, the Zn doping can improve the stability of CeO2 support in the alkaline condition, and the X-ray photoelectron spectroscopy (XPS) analysis clearly indicates that Zn doping leads to a negative shift in the binding energy of connected Ni and thus enhances the stability of the electronic structure in the catalysts. The findings in this work suggest that Zn-modified CeO2 supporting Ni–Pt catalyst offer a promising approach to achieving a better balance between activity and durability for hydrogen generation catalysts.

Ni-based bimetallic catalysts for hydrogen production via (sorption-enhanced) steam methane reforming

The catalytic performance of a monometallic Ni/Al2O3 and three bimetallic catalysts (Ni3M1/Al2O3, with M = Cu, Fe, and Ge) for the (sorption-enhanced) steam methane reforming reaction was evaluated. Ni3Cu1/Al2O3 was found to be the optimal catalyst in terms of methane conversion, hydrogen yield, and purity. Ge also has a promoting effect on the monometallic Ni catalyst, whereas the addition of Fe negatively influenced its performance. Physico-chemical characterization of the materials indicated the formation of alloys upon activation of the materials with hydrogen. The addition of Cu increased the surface area and metal dispersion, and improved the overall morphology of the catalyst. The experimental observations were also supported by a numerical study combining Density Functional Theory-based calculations and Microkinetic modelling of the SMR process. Ni3Cu1 and Ni3Ge1 were calculated to have a similar level of catalytic activity as Ni, whereas Ni3Fe1 was unsuitable for the reaction. The SMR reaction was further improved by adding calcium oxide as the CO2 sorbent, which increased methane conversion, CO selectivity, hydrogen yield, and hydrogen purity. The highest methane conversion of 97 % was achieved by Ni/Al2O3 and Ni3Cu1/Al2O3 at 700 °C.

Modulation of species adsorption to promote the semi-hydrogenation of C2H2 to C2H4 over Ni-based catalysts

Nickel-based bimetallic catalysts exhibit excellent ethylene selectivity in acetylene hydrogenation reactions. However, the rational design and control of the interaction between active adsorbates and catalyst surfaces still remains a significant challenge. In this paper, the introduction of the second metals Fe, Co, Mn, and Mo dilutes the catalyst surface and alters the electronic properties of Ni. As a result of the geometric and electronic dual modulation between the bimetals, ethylene is adsorbed on the catalyst surface through weak π-bonds, which accelerates the desorption of ethylene. In addition, alloying a second metal in Ni significantly lowers the desorption energy of ethylene compared to the hydrogenation barrier, which improves the selectivity of the reaction, and the experimental findings further confirm the validity of the calculations. This work offering a new strategy to the development Ni-based bimetallic catalysts by modulating the strength of adsorbed species on the catalyst surface to attain superior catalytic performance in hydrogenation reactions.

The Effectiveness of Ni-Based Bimetallic Catalysts Supported by MgO-Modified Alumina in Dry Methane Reforming

Syngas is produced through the carbon dioxide reforming of methane. The traditional nickel-based catalysts are substantially destroyed by carbon deposition. The reforming reaction was conducted in a tubular microreactor at 700 °C using bimetallic Ni catalysts supported over 37% Al2O3 and 63% MgO mixtures. The impregnation process formed the catalysts, which were subsequently examined by N2-physisorption, XRD, H2-TPR, TGA, and Raman spectroscopy. The 2.5Ni+2.5Co/37%Al2O3+63%MgO bimetallic catalyst, which displayed 72% and 76% conversions of CH4 and CO2 over the course of a seven-hour procedure, was discovered to be the most active in DRM. The bimetallic catalyst with the largest weight loss in TGA, 2.5Ni+2.5Fe-MG63, had a loss of 61.3%, a difference of 26% and 21% in the activity performance of CH4 and CO2, respectively, of the tested bimetallic Ni catalysts was recorded. The long-time of 30 h on-stream CH4 and CO2 conversion reactions for 2.5Ni+2.5Co-MG63 and 2.5Ni+2.5Ce-MG63 catalysts showed the catalysts’ high stability. The TPO analysis for the 2.5Ni+2.5Cs-MG63 catalyst showed a peak at 650 °C, attributed to the oxidation of the filamentous carbon, whereas the TPO analysis for the 2.5Ni+2.5Co-MG63 catalyst depicted a peak at 540 °C, ascribed to the presence of amorphous/graphite carbon.

Mechanistic and microkinetic insights into the stability and activity of Ni3In catalyst for dry methane reforming

Dry methane reforming (DMR) reaction has garnered significant attention for its potential in consuming CO2 for environmental sustainability, as well as utilizing CH4 as a fossil resource with the highest hydrogen content. In-depth understanding the reaction mechanism with microkinetic modeling is essential for suppressing coke deposition and improving the stability of Ni catalysts. This study investigates the reaction intermediates and pathways of DMR on Ni3In alloy, which has been previously identified by theoretical high-throughput screening and experimental results as having improved resistance to carbon accumulation. Energetic profiles, determined through density functional theory calculations, reveal that the Ni3In catalyst exhibits an increased formation barrier for C* and lower adsorption strength compared to pure Ni catalyst. Microkinetic analysis using the CatMAP package demonstrates significantly lower carbon coverage on Ni3In than Ni catalysts. Importantly, the dissociation of CO2 plays a critical role in influencing the rate of CO formation, particularly at higher reaction temperatures. Furthermore, through flux analysis, we have identified the main reaction pathways for CO formation and highlighted the multiple pathways for oxidizing carbon-containing species to suppress carbon deposition on Ni3In catalyst. These findings not only provide theoretical support for the experimental stability of Ni-In catalysts but also offer valuable insights for the rational design of other Ni-based bimetallic catalysts employed in DMR reactions.

Synergistic Effect of Bimetallic Ni-Based Catalysts Derived from Hydrotalcite on Stability and Coke Resistance for Dry Reforming of Methane

Synergistic Effect of Bimetallic Ni-Based Catalysts Derived from Hydrotalcite on Stability and Coke Resistance for Dry Reforming of Methane

Recent progress of the transition metal-based catalysts in the catalytic biomass gasification: A mini-review

Biomass is regarded as an important renewable resource, which plays a critical role in the development of sustainable energy systems. Biomass can be converted into energy or valuable chemicals by combustion, liquefaction, pyrolysis, and gasification. Among these processes, thermal gasification cracks biomass into light species at high temperatures, which can be applied to biomass with the greatest variety. As the target product of biomass gasification, syngas or H2-rich gas are very important intermediates in the petrochemical industry. However, the troublesome tar produced during gasification could bring a series of problems. Catalytic biomass gasification is a promising strategy to greatly alleviate these issues. The transition metal-based catalysts for catalytic biomass gasification have been studied in the last decades. Various transition metal catalysts for biomass gasification are reviewed in this article, including monometallic and bimetallic Ni-based catalysts, and other Fe-, Co-, and Pt-based catalysts. The performance of these catalysts is evaluated based on applied reaction parameters, the quality of produced syngas, and the performance of tar reduction. The applications of DFT calculation and AI for mechanism studies of biomass gasification have been summarized, and the cause of catalyst deactivation and regeneration of spent catalysts are also discussed. Therefore, the target of this article is to elucidate conventional biomass conversion pathways and review the recent progress on catalyst development in the biomass gasification process.

H2-rich syngas production from biogas reforming: Overcoming coking and sintering using bimetallic Ni-based catalysts

Dry reforming of methane is a very appealing catalytic route biogas (mainly composed by greenhouse gases: carbon dioxide and methane) conversion into added value syngas, which could be further upgraded to produce liquid fuels and added value chemicals. However, the major culprits of this reaction are coking and active phase sintering that result in catalysts deactivation. Herein we have developed a highly stable bimetallic Ni–Rh catalyst supported on mixed CeO2–Al2O3 oxide using low-noble metal loadings. The addition of small amounts of rhodium to nickel catalysts prevents coke formation and improves sintering resistance, achieving high conversions over extended reaction times hence resulting in promising catalysts for biogas upgrading.

Plasma-catalytic reforming of biogas into syngas over Ni-based bimetallic catalysts

Biogas reforming to syngas is an attractive route for the efficient utilization of biogas. In this work, plasma-catalytic dry reforming of biogas into value-added fuels and chemicals over Ni-based bimetallic catalysts was achieved using dielectric barrier discharge (DBD). The coupling DBD with 10Ni3Co exhibited the best reaction performance, reflected by the highest gas conversion, main gas product yield and selectivity, and fuel production efficiency (FPE). This hybrid process also favored the suppression of carbon deposition on the catalyst surface and the reduction of energy cost for both gas conversion and product formation. The maximum CO2 and CH4 conversion (29.8% and 49.1%) was obtained when the discharge power was 60 W, while a low discharge power (30 W) led to the highest FPE of 12.3%. By using Ni-based catalysts, we were able to tune the product distribution, favoring the generation of C3-C4 hydrocarbons and syngas while reducing the production of C2 hydrocarbons, with 10Ni3Co providing the most favorable results. Compared to other spent catalysts, the lowest carbon deposition (2.9%) was detected on the spent 10Ni3Co after 150 min of plasma reforming. Catalyst characterizations and density functional theory (DFT) calculations showed that the 10Ni3Co catalyst was superior due to a combination of factors such as a higher specific surface area, improved capability to adsorb CO2, strong interactions between the metals and the support, enhanced reducibility and the formation of a Ni-Co alloy. Furthermore, a simplified kinetics model was developed to better understand the effects of Ni-based bimetallic catalysts on the overall energy constant for the conversion of reactants in plasma-catalytic reforming of biogas.

Methane Reforming Processes: Advances on Mono- and Bimetallic Ni-Based Catalysts Supported on Mg-Al Mixed Oxides

Ni-based catalysts supported on Mg-Al mixed oxides (Mg(Al)O) have been intensively investigated as catalysts for CH4 reforming processes (i.e., steam reforming (SMR) and dry reforming (DRM)), which are pivotal actors in the expanding H2 economy. In this review, we provide for the first time an in-depth analysis of homo- and bimetallic Ni-based catalysts supported on Mg(Al)O supports reported to date in the literature and used for SMR and DRM processes. Particular attention is devoted to the role of the synthesis protocols on the structural and morphological properties of the final catalytic materials, which are directly related to their catalytic performance. It turns out that the addition of a small amount of a second metal to Ni (bimetallic catalysts), in some cases, is the most practicable way to improve the catalyst durability. In addition, besides more conventional approaches (i.e., impregnation and co-precipitation), other innovative synthesis methods (e.g., sol-gel, atomic layer deposition, redox reactions) and pretreatments (e.g., plasma-based treatments) have shown relevant improvements in identifying and controlling the interaction among the constituents most useful to improve the overall H2 productivity.

Retrofitting of carbon-supported bimetallic Ni-based catalysts by phosphorization for hydrogen evolution reaction in acidic media

Commercial bimetallic Ni–Mo and Ni–Re electrocatalysts supported on advanced conductive carbon are high-performing materials for H2 evolution reaction in alkaline medium, but they cannot be applied in acidic medium due to the rapid dissolution of metals. In this work, we solve this issue by introducing a convenient phosphorization protocol to convert these commercial metallic electrocatalysts into the respective phosphides, rendering them stable under acidic conditions, and thus providing a pathway to electrocatalysts for water reduction in acidic electrolyte. The novel materials demonstrate high performance, as reflected by the measured low overpotentials, shallow Tafel slopes, fast kinetics, as well as excellent stability and durability. This work opens the possibility to expand the applicability of commercial supported metallic catalysts and electrocatalysts through retrofitting via phosphorization.

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.

Synergistic trimetallic Ni–Cu–Sn catalysts for efficient selective hydrogenation of phenylacetylene

Selective hydrogenation of phenylacetylene is the most effective way to remove a small amount of phenylacetylene from styrene, but it is still a challenge to develop catalysts with high activity and selectivity. Herein, a series of non-precious bimetallic Ni3M/SiO2 (M = Zn, Sn, Cd, Fe, Co, Cu, or Mo) and trimetallic Ni3Cu–Sn/SiO2 catalysts were prepared and applied to selective hydrogenation of phenylacetylene. A trade-off between activity and selectivity was observed on Ni3M/SiO2, where Ni3Cu/SiO2 showed the best hydrogenation activity because of the hydrogen spillover effect of the Ni–Cu alloy, while Ni3Sn/SiO2 exhibited the highest selectivity to styrene due to the active-site isolation effect of the Ni–Sn alloy. Impressively, trimetallic Ni3Cu–Sn/SiO2 offered superior catalytic performance (94 % styrene selectivity at >99 % phenylacetylene conversion) as compared to bimetallic catalysts, owing to the synergistic effect among Ni, Cu, and Sn. In the case of Cu and Sn co-doping, the hydrogen spillover on the Ni–Cu alloy was deeply suppressed by Sn, which enabled an effective modification of the geometric and electronic structures of Ni to favor styrene desorption. The hydrogenation activity of Ni3CuSn0.3/SiO2 can be readily enhanced by increasing the metal loading and further improved by elevating the reaction temperature and pressure, but meanwhile the high selectivity is little affected. This work demonstrates a multi-metal synergistic strategy to break the activity–selectivity trade-off of Ni-based bimetallic catalysts in the selective hydrogenation of alkynes.

MOF-derived NiM@C catalysts (M = Co, Mo, La) for in-situ hydrogenation/hydrodeoxygenation of lignin-derived phenols to cycloalkanes/cyclohexanol

MOF-derived Ni-based bimetallic catalysts were found to be effective for the in-situ hydrogenation/hydrodeoxygenation of lignin-derived monophenols and dimers with isopropanol as the hydrogen-donor solvent (without external hydrogen). The synergistic effects of bimetallic catalysts were studied, and their catalytic properties afforded the best conversion rate of phenols and cyclohexanol/cycloalkane yields. The detailed physicochemical characterization was conducted by means of XRD, H2-TPR, NH3-TPD, and pyridine-IR analysis. The effects of reaction temperature (200–260 ℃) and reaction time (2–5 h) on the performance of lignin-derived monophenols and dimers were investigated. During the in-situ hydrogenation/hydrodeoxygenation of lignin-derived phenols, the steric effects and the effects of various functional groups, notably methoxy groups, were investigated. In-situ conversion of lignin-derived phenols with isopropanol was achieved over different Ni/M ratios of NiM@C (M = Co, Mo, and La) catalysts, from which NiLa0.33@C produced satisfactory yields of cyclohexanol/cycloalkanes.

Unveiling the origin of enhanced catalytic performance of NiCu alloy for semi-hydrogenation of acetylene

Ni-based bimetallic catalysts are widely explored for semi-hydrogenation of acetylene due to their enhanced catalytic performance. However, the comprehensive understanding of performance promoted by Ni-based alloy still remains elusive to date. Herein, supported NiCu/ZrO2 catalysts were fabricated to unveil the origin of improved selectivity and stability. Owing to the electronic and geometric modification of active Ni sites by Cu atoms, NiCu/ZrO2 ensures weak adsorption of key intermediates and easy desorption of ethylene, leading to an improved selectivity towards ethylene. DFT calculations indicate that both the activation barriers for the acetylene deep dehydrogenation pathway and the CC bond cleavage pathway on NiCu alloy are higher, suggesting that NiCu/ZrO2 would show superior stability over Ni/ZrO2. Therefore, the ID/IG ratio obtained via in-situ Raman, which represents the anti-coking ability of catalysts, can be employed as a descriptor of catalytic stability. These findings bring new insight for designing efficient heterogeneous catalysts for selective hydrogenation.

Reductive Amination of 5-Hydroxymethylfurfural to 2,5-Bis(aminomethyl)furan over Alumina-Supported Ni-Based Catalytic Systems.

Mono- and bimetallic Ni-based catalysts were prepared by screening 6 supports and 14 secondary metals for reductive amination of 5-hydroxymethylfurfural (5-HMF) into 2,5-bis(aminomethyl)furan (BAMF), among which γ-Al2 O3 and Mn were the best candidates. By further optimization of the reaction conditions at 0.4 g catalyst loading for 0.5 g substrate of 5-HMF and 160 °C of reaction temperature, 10Ni/γ-Al2 O3 and 10NiMn(4 : 1)/γ-Al2 O3 achieved the highest BAMF yields of 86.3 and 82.1 %, respectively. Although the BAMF yield values were comparable with that over Raney Ni, the turnover frequencies based on the initial BAMF yield and unit weight of Ni for 10NiMn(4 : 1)/γ-Al2 O3 , 10Ni/γ-Al2 O3 , and Raney Ni were calculated as 0.41, 0.09, and 0.04 h-1 , respectively. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy showed that the existence of MnOx well dispersed on the γ-Al2 O3 support and its electron transfer effect with Ni particles on the surface of the support contributed to the high efficiency and better recyclability for the five-time reused 10NiMn(4 : 1)/γ-Al2 O3 catalyst.

Selective Hydrogenation Properties of Ni-Based Bimetallic Catalysts

Metallic Ni shows high activity for a variety of hydrogenation reactions due to its intrinsically high capability for H2 activation, but it suffers from low chemoselectivity for target products when two or more reactive functional groups are present on one molecule. Modification by other metals changes the geometric and electronic structures of the monometallic Ni catalyst, providing an opportunity to design Ni-based bimetallic catalysts with improved activity, chemoselectivity, and durability. In this review, the hydrogenation properties of these catalysts are described starting from the typical methods of preparing Ni-based bimetallic nanoparticles. In most cases, the reasons for the enhanced catalysis are discussed based on the geometric and electronic effects. This review provides new insights into the development of more efficient and well-structured non-noble metal-based bimetallic catalytic systems for chemoselective hydrogenation reactions.

Coke-resistant Ni-based bimetallic catalysts for the dry reforming of methane: effects of indium on the Ni/Al2O3catalyst

In the quest for highly efficient coke-resistant catalysts for the dry reforming of methane (DRM) to produce syngas, a series of Ni–In/γ-Al2O3catalysts with various Ni contents were preparedviaa “two-solvent” method and used for the DRM reaction.