Ni Catalysts Research Articles

Decarboxylative Cross-Coupling Enabled by Fe and Ni Metallaphotoredox Catalysis.

Decarboxylative cross-coupling of carboxylic acids and aryl halides has become a key transformation in organic synthesis to form C(sp2)-C(sp3) bonds. In this report, a base metal pairing between Fe and Ni has been developed with complementary reactivity to the well-established Ir and Ni metallaphotoredox reactions. Utilizing an inexpensive FeCl3 cocatalyst along with a pyridine carboxamidine Ni catalyst, a range of aryl iodides can be preferentially coupled to carboxylic acids over boronic acid esters, triflates, chlorides, and even bromides in high yields. Additionally, carboxylic acid derivatives containing heterocycles, N-protected amino acids, and protic functionality can be coupled in 23-96% yield with a range of sterically hindered, electron-rich, and electron-deficient aryl iodides. Preliminary catalytic and stoichiometric reactions support a mechanism in which Fe is responsible for the activation of carboxylic acid upon irradiation with light and a NiI alkyl intermediate is responsible for activation of the aryl iodide coupling partner followed by reductive elimination to generate product.

Effects of nitrogen vacancy sites of oxynitride support on the catalytic activity for ammonia decomposition

Nitrogen-containing compounds such as imides and amides have been reported as efficient materials that promote ammonia decomposition over nonnoble metal catalysts. However, these compounds decompose in an air atmosphere and become inactive, which leads to difficulty in handling. Here, we focused on perovskite oxynitrides as air-stable and efficient supports for ammonia decomposition catalysts. Ni-loaded oxynitrides exhibited 2.5–18 times greater catalytic activity than did the corresponding oxide-supported Ni catalysts, even without noticeable differences in the Ni particle size and surface area of the supports. The catalytic performance of the Ni-loaded oxynitrides is well correlated with the nitrogen desorption temperature during N2 temperature-programmed desorption, which suggests that the lattice nitrogen in the oxynitride support rather than the Ni surface is the active site for ammonia decomposition. Furthermore, NH3 temperature-programmed surface reactions and density functional theory (DFT) calculations revealed that NH3 molecules are preferentially adsorbed on the nitrogen vacancy sites on the support surface rather than on the Ni surface. Thus, the ammonia decomposition reaction is facilitated by a vacancy-mediated reaction mechanism.

Ni Catalysts for Thermochemical CO2 Methanation: A Review

Ni Catalysts for Thermochemical CO2 Methanation: A Review

Nanostructured Ni–Co catalysts: Effect of impregnation sequence and complexing agent

This paper explores the synthesis by the impregnation method using citric acid and the characterization of bimetallic Nickel–Cobalt (Ni–Co) catalysts, focusing on their application in ethanol steam reforming leveraging the demonstrated improved stability and catalytic activity observed in previous works when Co is introduced into Ni catalysts. The study aims to investigate the effects of the sequence of incorporation of Ni and Co in the catalyst support in order to optimize the catalytic performance. The results indicate that the optimal sequence for introducing Co and Ni significantly enhanced the catalytic performance in ethanol steam reforming and it was associated to a higher Ce+3/Ce+4 ratio and a stronger active site-support interactions that modified the CNT growth mechanism, preventing increasing pressure drop through the reactors. The best catalytic performance corresponded to the system, Co/Ni/MgAl2O4–CeO2, in which Co was incorporated after Ni.

Catalytic Impedance Spectroscopy: Concept and Application on CO2 Methanation.

Complex modeling of periodic excitation combined with time-resolved product detection is used to describe the complex response function of a catalytic system. We describe this concept of catalytic impedance spectroscopy (CIS) and the underlying general experimental approach and a concrete setup. The feasibility of CIS is experimentally demonstrated along the catalytic CO2 methanation reaction. The measurements confirm the theoretically anticipated rate-determining step of HCO* → CH* on Ni catalysts. Limitations and prospects of CIS to unravel reaction mechanisms are discussed.

Enhanced syngas production through dry reforming of methane with Ni/CeZrO2 catalyst: Kinetic parameter investigation and CO2-rich feed simulation

Natuna's natural gas reserve, which contains 70 %–v CO2 and 30 %–v CH4, opens a prospective method for producing syngas through the dry reforming of methane (DRM). This study used the equation and determination of kinetic parameters in a fixed-bed reactor to develop the operating conditions for the DRM process. The catalyst used was 10 %Ni/CeZrO2 and followed the Langmuir-Hinshelwood mechanism, with CH4 dissociation (activation of C–H bonds) on the Ni catalyst as the rate-determining step. According to the results, the simulation and experimental data have error values of ≤ 5 % and RMSE < 0.046. This indicates that the equation and kinetic parameters used in the simulation are valid for reactor modeling. Steady-state modeling was then conducted using a 1D quasihomogeneous model. The feed composition of CO2:CH4 = 70:30 (Natuna gas field composition) has optimized results with temperature 700 °C, CH4 conversion at 92 %, CO2 conversion at 28 %, and H2/CO ratio 1.42, and carbon formation at 7.1 mgC/gcat. This study also found that a higher CO2:CH4 feed ratio could reduce carbon formation during DRM.

Vitreous silica supported metal catalysts for direct non-oxidative methane coupling

Direct non-oxidative methane coupling (NMC) transforms methane into valuable chemicals and hydrogen, which is a promising pathway to boost industrial decarbonization. The reaction, however, is challenged by high C-H bond activation temperature, catalyst coking, and low selectivity towards hydrocarbon products. Here we studied the efficacy of five vitreous silica supported 3d transition metal (Mn, Fe, Co, Ni, and Cu) catalysts (denoted as M/SiO2-v) for NMC. These catalysts were prepared by flame fusion of mixtures of quartz and metal silicate precursors. The metal species in the as-synthesized catalysts were fully or partially oxidized, with their stability following the order of Mn > Fe ≈ Co > Ni > Cu in the NMC reaction. The Cu species has low methane reaction rate, due to the high adsorption and dissociation energies of methane. The Mn and Ni species have high methane reaction and coke formation rates, which is supported by easy kinetics of methane deep dehydrogenation to carbon. In contrast, Fe and Co species showed the best hydrocarbon product selectivity. Particularly, the Co species emerged as the optimal catalyst for NMC, showcasing a balanced methane activation, hydrocarbon formation, and low coke yield. The relationship between the evolved metal species under reaction conditions and their NMC performance was discussed. The present study screens and provides effective catalyst formulations for NMC reactions.

Strategic conversion of plastic containers with food waste into energy through thermochemical processes

Plastic valorization has received particular attention as an environmentally benign approach to achieve carbon neutrality and reduce greenhouse gas emissions. However, contaminated plastic and biomass waste mixtures suffer from single-stream recycling. Waste mixtures are currently discarded through landfilling and incineration. As a sustainable disposal and valorization method for converting plastic and biomass waste mixtures into energy-intensive products, especially syngas (H2 and CO), this study utilizes catalytic pyrolysis and a CO2 flow gas. A plastic container contaminated with a food waste mixture (PFW) was used as the model waste. The major products of the pyrolysis of PFW were liquid hydrocarbons (HC) (C7–30) and wax-like HCs with negligible formation of oxygen-containing HCs. However, the high production of wax-like HCs becomes a problem. Catalytic pyrolysis was employed to convert HCs into simpler product streams such as syngas. Although syngas formation tripled with the Ni catalyst, catalyst deactivation was observed. To suppress catalyst deactivation and promote CO formation, CO2 was introduced instead of N2. During the CO2-assisted catalytic pyrolysis, the syngas yield from PFW increased to 95.5 % because the chemical reactions between CO2 and liquid/wax-like HCs produced additional H2 and CO. The catalytic reaction with CO2 suppressed carbon deposition because long-chain HCs were converted to CO rather than coke.

A comprehensive characterisation of food waste for its sustainable and holistic management using thermochemical processes

ABSTRACT This work presents a comprehensive physico-chemical analysis of mixed food waste (MFW) as a good feed for the thermochemical conversion process followed by its utilisation in the pyrolysis and gasification processes. The chemical analysis showed that MFW contained not only typical biomass contents, such as lignin (15.04%), cellulose (26.20%) and hemicellulose (5.05%) but also nutrients, such as protein (12.15%), starch (14.13%) and lipids (25.02%). Additionally, physical analyses, such as TGA, XRD, FTIR and FESEM, shed light on thermal behaviour, morphological structural and functional substituents in food waste. Post-analysis, 100-gm food waste was processed first via pyrolysis to produce bio-oil (40%) and bio-char (27%), then the biochar generated from pyrolysis was used as a feed in the steam gasification process which produced syngas (2.75 m3/Kg) as a main product and food waste ash as a side product. This food waste ash, in turn, was used as a support and promoter for Ni catalyst whose use in steam gasification showed a substantial increase in syngas production (1.26 m3/Kg from RFW and 3.6 m3/kg from bio-char).

Mn-enhanced performance of the Ni-CaO/γ-Al2O3 dual function material for CO2 capture and in situ methanation

The CH4 yield over dual functional materials (DFMs) remains low and requires further improvement. In this work, we first examined the influence of Mn on the performance of the Ni-CaO/γ-Al2O3 DFM for CO2 capture and in situ methanation. Our results showed that the MnNi-DFM-3 (MnNi-CaO/γ-Al2O3 DFM) exhibited the best performance at 350 °C, with a CH4 yield of 0.56 mmol/g which is 4 times higher than that of the Ni-DFM-1 (Ni-CaO/γ-Al2O3 DFM) (0.14 mmol/g). Nanoscale characterization revealed that highly scattered Mn3O4 acted as a barrier preventing the agglomeration of Ni-based catalysts. Furthermore, our density functional theory (DFT) analysis demonstrated that the introduction of Mn enhanced the activation of CO2, promoted the dissociation of H2 and intermediates, and reduced the activation energy needed to produce carboxylic acid intermediates on the Ni catalyst. The prepared MnNi-DFM is promising to be a cheap efficient material for CO2 capture and in situ methanation. This work opens up a new pathway for enhancing the performance of DFMs using inexpensive transition metals.

Regeneration of methane splitting catalysts by interfacial hydrogenation

Methane splitting, also known as decomposition or pyrolysis, has a unique potential to accelerate the transition from the current carbon-based economy towards the foreseen hydrogen economy. Low-temperature catalytic methane splitting systems are unavailable due to fast catalyst deactivation, caused by solid carbon that encapsulates the catalyst. Catalyst regeneration must be performed to reactivate the catalyst and achieve a long-term operational lifetime. This can be accomplished by cyclically refeeding a portion of the produced hydrogen back to the catalyst, which promotes the hydrogenation of carbon atoms, preferentially at the interface between carbon deposits and catalytic nanoparticles. Interfacial hydrogenation ideally breaks the bonds that connect carbon allotrope products to the metal catalyst, causing the former to detach, and freeing the catalytic metal surface for further reaction. In this work, a proof-of-concept of this technology is provided, showing the full regeneration of a bulk-type Ni catalyst during 22 cycles of methane splitting, at 550 °C and 1 bar. Furthermore, a commercial SiO2-Al2O3-supported Ni catalyst has been used to study the regenerability of a highly active nanostructured material by interfacial hydrogenation, using different reactor designs. It has been demonstrated that regeneration is beneficial to improve the stability of Ni-based systems, at the applied working conditions. Nevertheless, tip-grown carbon nanotubes were considered as a cause of permanent deactivation, which could not be solved by refeeding hydrogen into the system.

Catalytic modification of MgH2 hydrogen storage properties by La–Ni catalysts

In this paper, it is experimentally demonstrated that the La–Ni catalyst contributes to the hydrogen storage performance of MgH2. Firstly, La–Ni (La: Ni = 1: 5.7) catalysts are prepared by CaH2 reduction method, and then MgH2+x wt.% La–Ni (x = 0, 3, 5, 7) composite alloys were prepared by ball milling method. The present work focuses on the structural and hydrogen ab/desorption properties of the composite alloys, and analysis the modulatory effect and influence mechanism of different La–Ni catalyst additions on the hydrogen storage properties of MgH2. The findings show that the composite alloys have the same diffraction peaks and that the main phase of the composite alloys is the MgH2 phase, with the addition of the LaNi5 phase, the Mg2Ni phase and a small amount of Mg phase. The mutual reversible transformations of LaH3 and Mg2Ni and Mg2NiH4 play a catalytic role in the hydrogen ab/desorption process. Moreover, the addition of La–Ni catalyst plays a dramatic improvement effect on the kinetic performance of MgH2 ab/desorption. When the addition of La–Ni catalyst is 5 wt.%, the composite alloy exhibits the most excellent hydrogen uptake and release kinetics. The MgH2+5 wt.% La–Ni composite alloy absorbs 4.2 wt.% H2 within 2 min at 473 K and releases 3.43 wt.% H2 within 150 min at 503 K. Fitting the hydrogen release activation energy of the composite alloys shows that the hydrogen release activation energy of the composite alloys decreases first and then increases, and there is a minimum hydrogen release activation energy of 101.81 kJ/mol H2 when the addition amount x = 5 wt.%.

Highly efficient selective hydrogenation of furfural to tetrahydrofurfuryl alcohol over MOF-derived Co-Ni bimetallic catalysts: The effects of Co-Ni alloy and adsorption configuration

The targeted conversion of furfural (FA) over inexpensive catalyst is a critical and challenging project. Herein, CoNi alloy catalysts (xCoyNi/C) were prepared through one-step pyrolysis of metal–organic frameworks and used in furfural (FA) hydrogenation to tetrahydrofurfuryl alcohol (TFOL). The formation of CoNi alloy leads to a reconfiguration of the electronic structure on the metal surface, which affects the adsorption of functional groups on FA and furfuryl alcohol (FOL). In situ FT-IR analysis and DFT calculations verify that bimetallic CoNi alloy catalyst exhibits more suitable reactants adsorption and hydrogenation rate in comparison with the monometallic Co and monometallic Ni catalysts. Meanwhile, CoNi alloy significantly reduces the activation barrier from FOL to TFOL. Hence, the 1Co1Ni/C catalyst gives the highest TFOL yield of > 99 %. This study provides a simple strategy for the preparation of alloy catalysts for tuning product selectivity and presents practical potential for upgrading biomass-derived platform molecules.

Effect of Ga-Promoted on Ni/Zr + Al2O3 Catalysts for Enhanced CO2 Reforming and Process Optimization

AbstractIn this study, zirconia-modified alumina support (S) was used to investigate Ga-promoted Ni catalysts for dry reforming of methane (DRM). The catalysts (Ni + (0–3) wt% Ga/S) were prepared using the wet impregnation method and calcined at 700 °C for 3 h. The inclusion of Ga enhanced the surface area, basicity, and metal-support interaction of the Ni-Ga/S catalysts. Smaller Ni particles containing Ga were seen in the TEM. The most active and stable catalyst was Ni + 2.0 Ga/S, having a conversion of 35% CO2 and 28% CH4 at 600 °C and displaying less (17%) carbon deposition. Furthermore, the DRM process was optimized by a mathematical model. The model determined the optimal conditions as follows: temperature (800 °C), gas flow rate (GHSV—30,000 ml h−1gcat−1), and methane to carbon dioxide ratio (1:1). The model predicts CH4 and CO2 conversions of 76.76% and 82.0%, respectively, and an H2/CO ratio of 1.02, compared to experimental results showing CH4 conversion at 74.56%, CO2 conversion at 83.25%, and an H2/CO ratio of 1.01. The model demonstrates excellent agreement with the experimental observations, exhibiting less than 3% error. Graphical Abstract

Novel and active Bi2Zr1.9M0.1O7 (M = Mn, Fe, Co, Ni) catalysts for soot particle removal: Engineering surface with rich oxygen defects via partial substitution of Zr‐site

Novel and active Bi₂Zr_1.9M_0.1O₇ (M = Mn, Fe, Co, Ni) catalysts for soot particle removal: Engineering surface with rich oxygen defects via partial substitution of Zr‐site

Catalytic hydrothermal liquefaction of Azolla filiculoides into hydrocarbon rich bio-oil over a nickel catalyst in supercritical ethanol

Hydrothermal liquefaction (HTL) is one of the most promising thermochemical techniques for converting wet biomass into crude oil-like products (bio-oil). In this study, Catalytic hydrothermal liquefaction of Azolla filiculoides (AZ) was performed over a various loading of nickel (Ni) on magnesium oxide (MgO) catalyst for the higher and quality bio-oil production. The key operating parameters such as temperature, reaction holding time, amount of Ni on MgO supports catalyst, and reaction solvents were investigated in the presence of a hydrogen environment. There was a 12.8 wt% increase in bio-oil yield and a 6.3 wt% decrease in biochar yield with addition of 15 wt% Ni catalysts compared to the non-catalytic reaction bio-oil yield (44.0 wt%). Results confirmed the highest total bio-oil yield of 56.8 wt% was attained at 280 °C with the catalyst amount of 15 wt% at a residence time of 45 min. Gas chromatography-mass spectrometry (GC-MS), FT-IR, CHNS, TGA, and NMR analyses were performed on the bio-oil, identifying 32.8 % long-chain hydrocarbons (C12-C16) along with small amounts of alcohols, alkanes, and esters. The boiling point distribution revealed that bio-oil produced using the Ni/MgO catalyst contained a significantly higher proportion of diesel-range hydrocarbons (42.4 %). Furthermore, the bio-oil yield under ethanol solvent and Ni catalysts showed higher heating value (HHV) 42.2 MJ/kg. Overall in the presence of Ni hydrogenation efficient catalysts on MgO in the liquefaction reaction promoted the deoxygenation and hydrogenation reaction.

C–H bond activation over chitosan based Fe(III) and Ni(II) catalysts

Chitosan (Cs) supported heterogeneous catalysts of Fe(III) and Ni(II) is developed by the equimolar reaction of two schiff base ligands, L1 [Cs-HACP] and L2 [ANI-HACP] and Metal salts {where Metal = Fe(III) and Ni(II)}with chitosan. The L1 ligand is prepared by the reaction of chitosan (Cs) and ortho hydroxyl (HACP) acetophenone in methanol and L2 ligand is prepared by the condensation of aniline (ANI) and ortho hydroxyl acetophenone (HACP) in solvent free condition. The prepared catalysts {M-[Cs-L1-L2]Cl2} are characterized by different analytical techniques viz. scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), Raman, UV-VIS-NIR, X-ray photoelectron spectroscopy (XPS) and computational studies. The catalytic behavior of newly synthesized catalysts are tested for the C–H activation using 70 % tert-butyl hydroperoxide (TBHP). The best results are obtained for tetralin oxidation. The order of catalytic reactivity of {M-[Cs-L1-L2]Cl2}catalyst is in decreasing order: {Fe(III)-[Cs-L1-L2]Cl2} > {Ni(II)-[Cs-L1-L2]Cl2}. The {Fe(III)-[Cs-L1-L2]Cl2} gives maximum conversion 81.99 % of tetralin with 84.50 % selectivity of tetralone (T-lone) and 6.47 % selectivity of tetralol (T-lol) after 5 h of reaction at 80 °C temperature. The chitosan based heterogeneous catalyst is easy to separate and recover. It can be recycled seven times.

Evaluation of Cobalt, Nickel, and Palladium Complexes as Catalysts for the Hydrogenation and Improvement of Oxidative Stability of Biodiesel

Developing effective catalysts that can selectively hydrogenate C=C bonds in biodiesel samples is vital as it tackles the major problem of oxidative stability, which greatly limits the utilization of biodiesel as an alternative fuel. In this work, Co, Ni, and Pd catalysts stabilized with the bidentate nitrogen ligands N-(3-(triethoxysilyl)propyl)pyridin-2-ylmethylimine and N-(3-(triethoxysilyl)propyl)picolinamide were synthesized, characterized, and used as pre-catalysts in the transfer hydrogenation of C=C bonds in fatty acid methyl esters. The active catalysts from the Co, Ni, and Pd complexes sequentially hydrogenate the C18:2 chains to C18:1, which is further converted to C18:0 in the FAMEs of both methyl linoleate and jatropha biodiesel. The hydrogenation process was kinetically controlled, and after 3 h it yielded a biodiesel sample that contained 25.83% C16:0, 12.52% C18:2, 41.54% C18:1, 14.47% C18:0 and 3.0% C18:2 isomers. The un-hydrogenated jatropha diesel, hydrogenated jatropha diesel, and a B20 blend of jatropha were tested for susceptibility to oxidation reactions using the Rancimat method and FTIR spectroscopy, and the partial hydrogenation had improved the induction period by 3 h.

Metal‐N Coordination in Lithium‐Sulfur Batteries: Inhibiting Catalyst Passivation

Lithium‐sulfur (Li‐S) batteries exhibit great potential as the next‐generation energy storage techniques. Application of catalyst is widely adopted to accelerate the redox kinetics of polysulfide conversion reactions and improve battery performance. Although significant attention has been devoted to seeking new catalysts, the problem of catalyst passivation remains underexplored. Herein, we find that metal‐N coordination has a previously overlooked role in preventing the catalyst passivation. In the case of nickel, the Ni catalyst reacts with S8 to produce NiSx compounds on the surface, leading to catalyst passivation and slow the kinetics of LiPSs conversion. In contrast, when Ni is coordinated with N (typically Ni‐N4), S8 remains stable on the surface. The Ni‐N4 exhibits excellent resistance to passivation and rapid kinetics of LiPSs conversion. Consequently, the sulfur cathode with Ni‐N4 exhibits a high rate capability of 604.11 mAh g‐1 at 3 C and maintains a low capacity decay rate of 0.046% per cycle over 1000 cycles at 2 C. Furthermore, preventing S passivation in M‐N coordination applies not only to Ni‐N4 but also to various coordination numbers and transition metals. This study reveals a new aspect of metal‐N coordination in inhibiting catalyst passivation, improving our understanding of catalysts in Li‐S batteries.

Metal-N Coordination in Lithium-Sulfur Batteries: Inhibiting Catalyst Passivation.

Lithium-sulfur (Li-S) batteries exhibit great potential as the next-generation energy storage techniques. Application of catalyst is widely adopted to accelerate the redox kinetics of polysulfide conversion reactions and improve battery performance. Although significant attention has been devoted to seeking new catalysts, the problem of catalyst passivation remains underexplored. Herein, we find that metal-N coordination has a previously overlooked role in preventing the catalyst passivation. In the case of nickel, the Ni catalyst reacts with S8 to produce NiSx compounds on the surface, leading to catalyst passivation and slow the kinetics of LiPSs conversion. In contrast, when Ni is coordinated with N (typically Ni-N4), S8 remains stable on the surface. The Ni-N4 exhibits excellent resistance to passivation and rapid kinetics of LiPSs conversion. Consequently, the sulfur cathode with Ni-N4 exhibits a high rate capability of 604.11 mAh g-1 at 3 C and maintains a low capacity decay rate of 0.046 % per cycle over 1000 cycles at 2 C. Furthermore, preventing S passivation in M-N coordination applies not only to Ni-N4 but also to various coordination numbers and transition metals. This study reveals a new aspect of metal-N coordination in inhibiting catalyst passivation, improving our understanding of catalysts in Li-S batteries.