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Olefin polymerization is one of the most important chemical reactions in industry. This work presents a strategy that emphasizes the synergistic meta/para-steric hindrance of N-aryl groups and electronic effects in newly synthesized neutral salicylaldiminato nickel catalysts. These nickel(II) catalysts exhibit exceptional thermostability, ranging from 30 °C to 130 °C, demonstrating enhanced catalytic activities and broadly regulated polyethylene molecular weights (3–341 kg·mol−1) and controlled polymer branch density (2–102 brs/1000C). The preferred catalyst Ni3 with concerted steric and electronic effects enables the production of solid-state semi-crystalline polyethylene materials at temperatures below 90 °C. Notably, Ni3 exhibits an impressive tolerance of 110 °C and can withstand even the challenging polymerization temperature of 130 °C, leading to the production of polyethylene wax and oil. Also, functionalized polyethylene is produced. [ABSTRACT FROM AUTHOR]

Context: This study investigates the ethylene insertion reaction mechanism for polymerization catalysis, aiming to discern differences between Ni-α-imine ketone–type catalyst and their SiO2-supported counterpart. The reaction force analysis unveils a more intricate mechanism with SiO2 support, shedding light on unexplored factors and elucidating the observed lower catalytic activity. Furthermore, reactivity indexes suggest earlier ethylene activation in the supported catalyst, potentially enhancing overall selectivity. Finally, the reaction electronic flux analysis provides detailed insights into the electronic activity at each step of the reaction mechanism. In sum, this study offers a comprehensive understanding of the ethylene insertion reaction mechanism in both molecular and supported catalysts, underscoring the pivotal role of structural and electronic factors in catalytic processes. Methods: Density functional theory (DFT) calculations were conducted using the ωB97XD functional and the 6–31 + G(d,p) basis sets with Gaussian16 software. Computational techniques utilized in this study encompassed the IRC method, reaction force analysis, and evaluation of electronic descriptors such as electronic chemical potential, molecular hardness, and electrophilicity reactivity indexes. Additionally, reaction electronic flux analysis was employed to investigate electronic activity along the reaction coordinate. [ABSTRACT FROM AUTHOR]

The aim of this study was to deposit a Ni–La–Zr catalyst on a FeCrAl monolith by in situ growth of the catalyst on a metallic surface through immersion in a modified polymeric precursor solution. The prepared monolith was characterized by X-ray diffraction, atomic force microscopy, and scanning electron microscopy and was tested in a tri-reforming reaction of simulated biogas (CH4/CO2 = 3) for synthesis gas production. The monolithic catalyst presented better stability than the powdered catalyst under the 50-h test. In contrast, the powdered catalyst showed more pronounced deactivation, which was associated with higher carbon deposition. This study provides valuable information on a simple deposition method for Ni-based catalysts on FeCrAl monoliths for biogas tri-reforming reactions, which could have implications for biogas upgrading. [ABSTRACT FROM AUTHOR]

It has been shown that the nature of the metal precursor and the thermal effects during calcination determine the physicochemical properties of the catalysts and their catalytic activity in the levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) hydrogenation reactions. The endothermic effect during calcination of the inorganic nickel precursor promoted higher metal dispersion and stronger interaction with the alumina surface. In contrast, the exothermic effects during the calcination of organic nickel precursors resulted in smaller metal dispersion and lower interaction with the support surface. A clear relationship was found between the size of the metal crystallites and the yield of LA hydrogenation reaction. The smaller crystallites were more active in the LA hydrogenation reaction. In turn, the size of the metal particles and their nature of interaction with the surface of the alumina influence the hydrogenation pathways of the HMF. [ABSTRACT FROM AUTHOR]

The development of highly active, reusable catalysts for aqueous‐phase reactions is challenging. Herein, metallic nickel is encapsulated in a nitrogen‐doped carbon–silica composite (SiO2@Ni@NC) as a catalyst for the selective hydrogenation of vanillin in aqueous media. The constructed catalyst achieved 99.8% vanillin conversion and 100% 4‐hydroxymethyl‐2‐methoxyphenol selectivity at room temperature. Based on combined scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, and Raman analyses, the satisfactory catalytic performance is attributed to the composite structure consisting of an active metal, carbon, and silica. The hydrophilic silica core promoted dispersion of the catalyst in aqueous media. Moreover, the external hydrophobic NC layer has multiple functions, including preventing oxidation or leaching of the internal metal, acting as a reducing agent to reduce the internal metal, regulating the active‐site microenvironment by enriching the concentrations of H2 and organic reactants, and modifying the electronic structure of the active metal via metal–support interactions. Density functional theory calculations indicated that NC facilitates vanillin adsorption and hydrogen dissociation to promote aqueous‐phase hydrogenation. This study provides an efficient strategy for constructing encapsulated Ni‐based amphiphilic catalysts to upgrade biomass‐derived compounds. [ABSTRACT FROM AUTHOR]

Hydrocarbons, when used as the medium for transition metal catalyzed organic reactions and olefin (co‐)polymerization, are ubiquitous. Environmentally friendly water is highly attractive and long‐sought, but is greatly challenging as coordination‐insertion copolymerization reaction medium of olefin and polar monomers. Unfavorable interactions from both water and polar monomer usually lead to either catalyst deactivation or the formation of low‐molecular‐weight polymers. Herein, we develop well‐behaved neutral phosphinophenolato nickel catalysts, which enable aqueous copolymerization of ethylene and diverse polar monomers to produce significantly high‐molecular‐weight linear polar polyolefins (219–549 kDa, 0.13–1.29 mol %) in a single‐component fashion under mild conditions for the first time. These copolymerization reactions occur better in water than in hydrocarbons such as toluene. The dual characteristics of high molecular weight and the incorporation of a small amount of functional group result in improved surface properties while retain the desirable intrinsic properties of high‐density polyethylene (HDPE). [ABSTRACT FROM AUTHOR]

In this study, vermiculite was explored as a support material for nickel catalysts in two key processes in syngas production: dry reforming of methane with CO2 and steam reforming of ethanol. The vermiculite underwent acid or base treatment, followed by the preparation of Ni catalysts through incipient wetness impregnation. Characterization was conducted using various techniques, including X-ray diffraction (XRD), SEM–EDS, FTIR, and temperature-programmed reduction (H2-TPR). TG-TD analyses were performed to assess the formation of carbon deposits on spent catalysts. The Ni-based catalysts were used in reaction tests without a reduction pre-treatment. Initially, raw vermiculite-supported nickel showed limited catalytic activity in the dry reforming of methane. After acid (Ni/VTA) or base (Ni/VTB) treatment, vermiculite proved to be an effective support for nickel catalysts that displayed outstanding performance, achieving high methane conversion and hydrogen yield. The acidic treatment improved the reduction of nickel species and reduced carbon deposition, outperforming the Ni over alkali treated support. The prepared catalysts were also evaluated in ethanol steam reforming under various conditions including temperature, water/ethanol ratio, and space velocity, with acid-treated catalysts confirming the best performance. [ABSTRACT FROM AUTHOR]

This study describes a method to synthesize compounds with an arylidene group at the alpha position of N‐methyl‐2‐pyrrolidone (NMP) and an alcohol group at the gamma position in a single‐step reaction using NMP and aldehyde. The highest yields were obtained with Ni(glyme)Cl2 as a nickel catalyst and tert‐butyl hydroperoxide as the oxidant, and various aryl aldehydes reacted under optimal conditions to yield the target compounds. [ABSTRACT FROM AUTHOR]

An efficient and versatile synthesis of alcohols via transfer hydrogenation from ketones with isopropanol, utilizing [Ni(6,6′‐(OH)2‐2,2′‐bpy)][Br2] under alkaline conditions, has been documented. It was noteworthy that many readily reducible or labile functional groups such as nitro, cyano, and halide, within the same molecular framework, did not undergo any change under the standard reaction conditions. Furthermore, the gram scale transfer hydrogenation reaction was successfully carried out with good yield using a common route with only a single purification by column chromatography. [ABSTRACT FROM AUTHOR]

The physical properties of traditional polyolefin materials can be significantly improved by introducing polar groups, especially polar aromatic groups. However, it remains a major challenge to realize the highly effective copolymerization of ethylene with styrene derivatives. In this study, the direct copolymerization of ethylene with various polar styrene monomers bearing functional groups (o‐OMe, m‐OMe, p‐OMe, o‐Cl, m‐Cl, p‐ClSt, o‐F, o‐Br, p‐Me, p‐Ph, p‐Vinyl, p‐COOH, and C6F5) was achieved using phosphino‐dihydronaphtholate neutral nickel catalysts Ni1‐Ni3. Additionally, the catalytic behavior and the applicability of the polar monomer were evaluated in detail by copolymerization results. Catalysts Ni1‐Ni3 demonstrated inactivity towards the polymerization of polar styrene monomers but exhibited moderate catalytic activities in the copolymerization of ethylene with polar styrene monomers, yielding moderate‐molecular‐weight (Mw > 10 kDa) copolymers with the polar monomer contents ranging from 1.32 to 4.16 mol%. The steric and electronic effects of the substituent depending on the types and position in the phenyl ring considerably influenced the copolymerization behavior. Furthermore, comprehensive NMR analyses of the produced copolymers revealed that the polar monomers formed in‐chain insertions, saturated chain ends, and unsaturated chain ends after incorporation. [ABSTRACT FROM AUTHOR]

The search for alternative non‐noble transition metal catalysts able to evolve hydrogen has been the focus of intense research. Molecular complexes bearing redox‐active ligands have been reported as efficient electrocatalysts for hydrogen evolution reaction (HER). This study showcases a new family of nickel‐thiosemicarbazone complexes displaying significant activity for HER in DMF solvent using trifluoracetic acid as proton source. Following previous works in our group, the ligand was stereochemically tailored, placing methoxy groups at different locations and considering various combinations of positions. Three complexes within the series were shown to outperform the parent catalyst bearing the methoxy group in para position. Overall, the nickel catalyst having the chemical substituent in meta position displays the best catalytic performances while having the lowest overpotential. These results support that ligand stereochemical tailoring in metal complexes improves electrocatalytic HER and suggest that ligand tuning is a promising direction to enhance catalyst performances. [ABSTRACT FROM AUTHOR]

CO2 methanation is one of the advantageous processes of carbon capture and utilisation (CCU) technologies to circulate the carbon on Earth, mitigating the release and loss of CO2 into the atmosphere. Herein, a Ni/r-CeO2 catalyst was fabricated using a facile method of impregnating Ni(NO3)2·6H2O on CeO2 nanorods (r-CeO2), synthesised by hydrothermal method at low temperature (130 °C). The influence of Ni active phase content and activation condition on the characteristics and catalytic performances in CO2 methanation were investigated. The physicochemical properties of the synthesised catalyst were studied using several techniques: XRD, EDS, isotherm nitrogen adsorption, SEM, HR-TEM, H2-TPR, CO2-TPD and Raman. Catalytic activity survey and analysis show the excellent performance of Ni/r-CeO2 with a Ni loading of 15 wt% (15NiCe) calcined at 600 °C for 4 h and reduced at 450 °C for 2.5 h. By adjusting the nickel loading on ceria and altering synthesis conditions, it's possible to achieve highly dispersed NiO particles with an optimal size (∼13.9 nm), abundant oxygen vacancies, and the presence of medium-strength basic sites. This leads to improved catalytic activity, resulting in an equilibrium CO2 conversion rate of approximately 90% and 100% selectivity for CH4 at temperatures as low as 325°C. The 15Ni/r-CeO2 catalyst serves as a highly active low-temperature catalyst for CO2 methanation.

Biomass valorization is an essential strategy for converting organic resources into valuable energy and chemicals, contributing to the circular economy, and reducing carbon footprints. Glycerol, a byproduct of biodiesel production, can be used as a feedstock for a variety of high-value products and can contribute to reducing the carbon footprint. This study examines the impact of surface-level modifications of Mg, Cu, and Sn on Ni-Ce-Zr catalysts for the hydrogenolysis of glycerol, with in situ generated hydrogen. The aim of this approach is to enhance the efficiency and sustainability of the biomass valorization process. However, the surface modification resulted in a decrease in the global conversion of glycerol due to the reduced availability of metal sites. The study found that valuable products, such as H2 and CH4 in the gas phase, and 1,2-PG in the liquid phase, were obtained. The majority of the liquid fraction was observed, particularly for Cu- and Sn-doped catalysts, which was attributed to their increased acidity. The primary selectivity was towards the cleavage of the C–O bond. Post-reaction characterizations revealed that the primary causes of deactivation was leaching, which was reduced by the inclusion of Cu and Sn. These findings demonstrate the potential of Cu- and Sn-modified Ni-Ce-Zr catalysts to provide a sustainable pathway for converting glycerol into value-added chemicals. [ABSTRACT FROM AUTHOR]

[Display omitted] Manipulating metal valence states and porosity in the metal–organic framework (MOF) by alloying has been a unique tool for creating high-valent metal sites and pore environments in a structure that are inaccessible by other methods, favorable for accelerating the catalytic activity towards sensing applications. Herein, we report Fe3+-driven formation of catalytic active Ni3+ species in the amine-crafted benzene-dicarboxylate (BDC-NH 2)-based MOF as a high-performance electrocatalyst for glucose sensing. This work took the benefit of different bonding stability between BDC-NH 2 ligand, and Fe3+ and Ni2+ metal precursor ions in the heterometallic Ni x Fe (1- x) -BDC-NH 2 MOF. The FeCl 3 that interacts weakly with ligand, oxidizes the Ni2+ precursor to Ni3+-based MOF owing to its Lewis acidic behavior and was subsequently removed from the structure supported by Ni atoms, during solvothermal synthesis. This enables to create mesopores within a highly stable Ni-MOF structure with optimal feed composition of Ni 0.7 Fe 0.3 -BDC-NH 2. The Ni3+-based Ni 0.7 Fe 0.3 -BDC-NH 2 demonstrates superior catalytic properties towards glucose sensing with a high sensitivity of 13,435 µA mM−1 cm−2 compared to the parent Ni2+-based Ni-BDC-NH 2 (10897 μA mM−1 cm−2), along with low detection limit (0.9 μM), short response time (≤5 s), excellent selectivity, and higher stability. This presented approach for fabricating high-valent nickel species, with a controlled quantity of Fe3+ integrated into the structure allowing pore engineering of MOFs, opens new avenues for designing high-performing MOF catalysts with porous framework for sensing applications. [ABSTRACT FROM AUTHOR]

In the presented work, the catalytic performance of a nickel catalyst, in CO2 hydrogenation to methane, within a ZrO2 open-cell foam (OCF)-based catalyst was studied. Two series of analogous samples were prepared and coated with 100–150 mg of a Mg-Al oxide interface to stabilize the formation of well-dispersed Ni crystallites, with 10–15 wt% of nickel as an active phase, based on 30 ppi foam or 45 ppi foam. The main factor influencing catalytic performance was the geometric parameters of the applied foams. The series of catalysts based on 30 ppi OCF showed CO2 conversion in the range of 30–50% at 300 °C, while those based on 45 ppi OCF resulted in a significantly enhancement of the catalytic activity: 90–92% CO2 conversion under the same experimental conditions. Calculations of the internal and external mass transfer limitations were performed. The observed difference in the catalytic activity was primarily related to the radial transport inside the pores, confirmed with the explicitly higher conversions. [ABSTRACT FROM AUTHOR]

Abstract The development of highly active, reusable catalysts for aqueous‐phase reactions is challenging. Herein, metallic nickel is encapsulated in a nitrogen‐doped carbon–silica composite (SiO2@Ni@NC) as a catalyst for the selective hydrogenation of vanillin in aqueous media. The constructed catalyst achieved 99.8% vanillin conversion and 100% 4‐hydroxymethyl‐2‐methoxyphenol selectivity at room temperature. Based on combined scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, and Raman analyses, the satisfactory catalytic performance is attributed to the composite structure consisting of an active metal, carbon, and silica. The hydrophilic silica core promoted dispersion of the catalyst in aqueous media. Moreover, the external hydrophobic NC layer has multiple functions, including preventing oxidation or leaching of the internal metal, acting as a reducing agent to reduce the internal metal, regulating the active‐site microenvironment by enriching the concentrations of H2 and organic reactants, and modifying the electronic structure of the active metal via metal–support interactions. Density functional theory calculations indicated that NC facilitates vanillin adsorption and hydrogen dissociation to promote aqueous‐phase hydrogenation. This study provides an efficient strategy for constructing encapsulated Ni‐based amphiphilic catalysts to upgrade biomass‐derived compounds.

With the increasing demand for production of graphitic materials for various applications, it becomes crucial to get a fundamental understanding of how graphene layers grow on metal catalysts. Here, we performed an in situ heating transmission electron microscopy (TEM) study to understand the mechanism of graphitization of amorphous carbon (a-C) on Ni catalyst by following graphene growth at atomic resolution in real time. By discerning the Ni3C phase from the pure Ni phase during the graphitic carbon growth process, we demonstrate that growth occurs through the carbide graphitization of Ni3C. Additionally, during the graphitization, Ni diffusion has a crucial effect on the structure of the resulting graphene. Under our experimental conditions, we observed graphene contains islands of multilayers. Based on our in situ experimental results, we suggest a mechanism for graphitization of the a-C/Ni system and explain the dynamics resulting from Ni diffusion. Our study can contribute to the control of graphitization by using Ni catalyst in the production of graphene and other graphitic materials.

In classic cyanation reactions, toxic metal cyanide sources or complex organic cyanide sources are often used. Therefore, it is particularly important to develop a green and economical cyano source. Initially, 4-biphenylyl trifluoromethanesulfonate is chosen as the model substrate. Through extensive screening of catalysts, ligands, additives, reductant, temperature and other conditions, the optimal conditions are obtained (Ni(OTf)2, 1, 3-bis (diphenyphosphino)propane, Zn(OTf)2, Zn with a mole fraction of 0.1, 0.1, 0.2, 2, respectively, 0.7 mL CH3CN, N2, 60 h, 100 ℃). Subsequently, the generation and limitations of the substrates are studied under optimal conditions. It is found that substrates bearing electron-donating substituents exhibit an excellent efficiency for the cyanation of aryl trifluoromethanesulfonates. The cyanation of aryl trifluoromethanesulfonates is first realized under the catalysis of nickel with acetonitrile as a green and economical cyano source.

Solar‐driven photothermal conversion of carbon dioxide (CO2) to methane (CH4) is a promising approach to remedy energy shortage and climate changes, where highly efficient photothermal catalysts for CO2 methanation urgently need to be designed. Herein, nickel‐based catalysts (Ni/ZrO2) derived from metal–organic frameworks (MOFs) are fabricated and studied for photothermal CO2 methanation. The optimized catalyst 50Ni/ZrO2 achieves a stable CH4 production rate of 583.3 mmol g−1 h−1 in a continuous stability test, which is almost tenfold higher than that of 50Ni/C‐ZrO2 synthesized via commercial ZrO2. Physicochemical properties indicate that 50Ni/ZrO2 generates more tetragonal ZrO2 and possesses more oxygen vacancies (OVs) as well as enhanced nickel‐ZrO2 interaction. As a result, 50Ni/ZrO2 exhibits the strong abilities of light absorption and light‐to‐heat conversion, superior adsorption capacities of reactants (H2, CO2), and an intermediate product (CO), which finally boosts CH4 formation. This work provides an efficient strategy to design a photothermocatalyst of CO2 methanation through utilizing MOFs‐derived support. [ABSTRACT FROM AUTHOR]

This study investigates the effect of cerium–zirconium supported nickel catalyst (Ni/CeZr(x)) on the dry reforming reaction of methane (CH4) and carbon dioxide (CO2) to produce hydrogen (H2) and carbon monoxide (CO) for use in petrochemical processes. CeZr supports were synthesized via template-assisted co-precipitation using CTAC as a template with varying pH values (5, 7, 8.5, and 10) and underwent hydrothermal processing. Nickel (10% by weight) was then loaded onto the support through incipient wetness impregnation. The dry reforming reaction was performed at 700 °C. Results revealed that as the pH increased from acidic to basic conditions, the precipitation and integration of ZrO2 and CeO2 improved, leading to the formation of CeZr(x) composite supports. The Ce/Zr ratio in Ni/CeZr(x) catalysts influenced the generation of oxygen vacancies (OV) on the catalyst surface, affecting CO2 and CH4 conversions and the H2/CO ratio. The Ni/CeZr(8.5) catalyst exhibited the highest activity and stability due to its high surface oxygen vacancy and the number of basic sites on the CeZr(8.5) surface. Moreover, this catalyst reduced coke formation by promoting CO2 adsorption and dissociation, which facilitated the formation of surface-bound oxygen species that reacted with the surface carbon species. [ABSTRACT FROM AUTHOR]

Syngas can be produced from biomethane via Partial Oxidation of Methane (POM), being an attractive route since it is ecofriendly and sustainable. In this work, catalysts of Ni supported on MgO–ZrO2 solid solutions, prepared by a one-step polymerization method, were characterized by HRTEM/EDX, XRD, XPS, H2-TPR, and in situ XRD. All catalysts, including Ni/ZrO2 and Ni/MgO as reference, were tested for POM (CH4:O2 molar ratio 2, 750 ºC, 1 atm). NiO/MgO/ZrO2 contained two solid-solutions, MgO–ZrO2 and NiO-MgO, as revealed by XRD and XPS. Ni (30 wt%) supported on MgO–ZrO2 solid solution exhibited high methane conversion and hydrogen selectivity. However, depending on the MgO amount (0, 4, 20, 40, 100 molar percent) major differences in NiO reducibility, growth of Ni0 crystallite size during H2 reduction and POM, and in carbon deposition rates were observed. Interestingly, catalysts with lower MgO content achieved the highest CH4 conversion (~ 95%), high selectivity to H2 (1.7) and CO (0.8), and low carbon deposition rates (0.024 g carbon.gcat−1 h−1) with Ni4MgZr (4 mol% MgO) turning out to be the best catalyst. In situ XRD during POM indicated metallic Ni nanoparticles (average crystallite size of 31 nm), supported by MgO–ZrO2 solid solution, with small amounts of NiO–MgO being present as well. The presence of MgO also influenced the morphology of the carbon deposits, leading to filaments instead of amorphous carbon. A combustion-reforming mechanism is suggested and using a MgO–ZrO2 solid solution support strongly improves catalytic performance, which is attributed to effective O2, CO2 and H2O activation at the Ni/MgO–ZrO2 interface. [ABSTRACT FROM AUTHOR]

A major cause of premature catalyst deactivation in the catalytic hydrogenation of fatty acids is the presence of impurities in the feedstock. With more oleochemical plants shifting to opportunistic crude palm oil (CPO) as their feedstock, the feedstock quality becomes an important factor in their procurement process. For CPO, the impurities level can be coarsely estimated by the deterioration of bleaching index (DOBI). A high DOBI value (e.g. DOBI > 2.99) indicates good quality CPO and ease in processing, while low DOBI value implies low level of carotene and/or high level of oxidised sludge oil, both of which could be detrimental to the processing of CPO. In our work, unsplit CPO feedstocks with varying DOBI value were directly hydrogenated in a laboratory‐scale pressure reactor with the presence of commercial nickel catalysts. Experimental results showed that catalyst deactivation was linked to DOBI value, where decreasing DOBI led to faster catalyst deactivation. For example, iodine value (IV) < 1.0 can be achieved for CPO with high DOBI value (2.97) after 150 min, and IV of 5–7 and IV > 20 were achieved for medium DOBI value (2.57–2.68) and low DOBI value (2.24), respectively. For CPO with low DOBI value (2.24), doubling the catalyst dosage ensured that the hydrogenated product met the low IV specification. This work showed that identifying the CPO with DOBI value presents an indicator to the manufacturer to find the right CPO tailored to the existing processes to maximise profitability. [ABSTRACT FROM AUTHOR]

Rate-controlled growth of carbon nanotubes (CNTs) and catalyst design are considered efficient ways for the preparation of CNTs with specific structures and properties. However, due to the difficulties in capturing the growth process of the CNTs with tiny size under a complex growth environment, the growth kinetics of CNTs and their correlation with the catalyst seed have been seldom revealed. Here, we investigated the growth process of CNTs from Ni nanoparticles (NPs) in real-time under atmospheric pressure using transmission electron microscopy equipped with a closed gas cell. It was found that the growth rates of CNTs fluctuated, and a phase transition from Ni3C to Ni, and a reshaping of the catalyst NPs occurred during the growth process. We demonstrated that CNTs dynamically interacted with the connected catalyst NPs and the fluctuated growth rates of CNTs were correlated with the structure change of catalyst NPs. The origin of the growth rate fluctuation is attributed to the change of carbon concentration gradient in catalyst NPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two fluorinated and one non–fluorinated complex of the type [(NHC)Ni(Cp)(Br)] were synthesized and characterized. • The non–fluorinated complex showed higher catalytic activity than the fluorinated ones in the C–S cross–coupling reaction. • The catalytic reaction mechanism was studied by theoretical calculations. • Strong nucleophilic substrates quenched the C–S cross–coupling by forming a stable intermediate complex. The catalytic activities of three Ni(II) complexes with fluorinated and non–fluorinated N–heterocyclic carbene (NHC) ligands were evaluated in the C–S cross–coupling reaction between iodobenzene and thiophenol. The complexes with fluorinated–NHC ligands exhibited lower catalytic activities compared to the non–fluorinated derivative. This can be attributed to the lower electron–donating character of the fluorinated ligands in comparison to the non–fluorinated ligand. Complex 3–Ni was tested towards different substrates, achieving moderate to good conversions. Additionally, the reaction mechanism of the C–S cross–coupling using two substrates, tert–butylthiol and 2,4–dichlorobenzenethiol, was determined. Tert–butylthiol produced a stable intermediate that inhibited the last step of the reaction mechanism (reductive elimination). On the other hand, 2,4–dichlorobenzenethiol formed a less stable intermediate, favoring the reductive elimination. This observation aligns with the lower yield observed when using tert–butylthiol compared to 2,4–dichlorobenzenethiol (20% vs 99%). [ABSTRACT FROM AUTHOR]

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Ni/Al2O3 catalysts (noted as Ni/Al-350, Ni/Al-500, and Ni/Al-700, respectively) were synthesized by a facile solution combustion method but at different combustion temperatures (350 °C, 500 °C, and 700 °C, respectively). For comparison, Ni/Al2O3 (noted as Ni/Al-100) was also prepared by the impregnation method and applied in the methanation reaction. The Ni/Al2O3 synthesized at the combustion temperature of 350 °C showed better performance than the others at higher combustion temperatures, and the activity for CO2 methanation followed an order of Ni/Al-350 > Ni/Al-500 > Ni/Al-700 > Ni/Al-100. The increase in the combustion temperature decreased active sites for the H2 and CO2 adsorption, which could be associated with the reduced Ni dispersion and basic sites, thus lowering its activity and increasing its carbon deposition rate.

It has been shown that the nature of the metal precursor and the thermal effects during calcination determine the physicochemical properties of the catalysts and their catalytic activity in the levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) hydrogenation reactions. The endothermic effect during calcination of the inorganic nickel precursor promoted higher metal dispersion and stronger interaction with the alumina surface. In contrast, the exothermic effects during the calcination of organic nickel precursors resulted in smaller metal dispersion and lower interaction with the support surface. A clear relationship was found between the size of the metal crystallites and the yield of LA hydrogenation reaction. The smaller crystallites were more active in the LA hydrogenation reaction. In turn, the size of the metal particles and their nature of interaction with the surface of the alumina influence the hydrogenation pathways of the HMF.

In this study, vermiculite was explored as a support material for nickel catalysts in two key processes in syngas production: dry reforming of methane with CO2 and steam reforming of ethanol. The vermiculite underwent acid or base treatment, followed by the preparation of Ni catalysts through incipient wetness impregnation. Characterization was conducted using various techniques, including X-ray diffraction (XRD), SEM–EDS, FTIR, and temperature-programmed reduction (H2-TPR). TG-TD analyses were performed to assess the formation of carbon deposits on spent catalysts. The Ni-based catalysts were used in reaction tests without a reduction pre-treatment. Initially, raw vermiculite-supported nickel showed limited catalytic activity in the dry reforming of methane. After acid (Ni/VTA) or base (Ni/VTB) treatment, vermiculite proved to be an effective support for nickel catalysts that displayed outstanding performance, achieving high methane conversion and hydrogen yield. The acidic treatment improved the reduction of nickel species and reduced carbon deposition, outperforming the Ni over alkali treated support. The prepared catalysts were also evaluated in ethanol steam reforming under various conditions including temperature, water/ethanol ratio, and space velocity, with acid-treated catalysts confirming the best performance.

Abstract Barium doping effect on the activity and stability of nickel‐based catalysts, supported on yttria‐stabilized zirconia (Ni‐YZr), was investigated in dry reforming of methane. Catalysts were characterized by several techniques (nitrogen sorption, X‐ray diffraction [XRD], scanning electron microscopy with energy dispersive X‐ray, transmission electron microscopy [TEM], thermogravimetric analysis [TGA], temperature programmed oxidation, CO2‐TPD, H2‐TPR) and were tested in a fixed‐bed reactor at 800°C and 42,000 mL/h gcat. Barium played a crucial role in enhancing catalyst reducibility and CO2 adsorption at high temperatures, as indicated by the activity and stability of the Ni‐YZr catalyst. The addition of 4.0 wt% of barium appeared to be the optimal loading, allowing for CH4 conversion of 82%, which remained constant for 7 h of reaction, compared with 72% of barium‐unpromoted Ni‐YZr at 800°C. TEM images of the spent catalysts revealed the formation of multiwalled carbon nanotubes on all samples. The TGA analysis showed, however, that an increase in baria loading significantly reduced the coke formation amount, indicating the inhibition of coke formation and the enhancement of the catalytic activity. Such improvement in activity and stability was attributed to the incorporation of barium into YZr support, as revealed by XRD analysis, which inhibited the sintering of the catalysts support.

Abstract Solar‐driven photothermal conversion of carbon dioxide (CO2) to methane (CH4) is a promising approach to remedy energy shortage and climate changes, where highly efficient photothermal catalysts for CO2 methanation urgently need to be designed. Herein, nickel‐based catalysts (Ni/ZrO2) derived from metal–organic frameworks (MOFs) are fabricated and studied for photothermal CO2 methanation. The optimized catalyst 50Ni/ZrO2 achieves a stable CH4 production rate of 583.3 mmol g−1 h−1 in a continuous stability test, which is almost tenfold higher than that of 50Ni/C‐ZrO2 synthesized via commercial ZrO2. Physicochemical properties indicate that 50Ni/ZrO2 generates more tetragonal ZrO2 and possesses more oxygen vacancies (OVs) as well as enhanced nickel‐ZrO2 interaction. As a result, 50Ni/ZrO2 exhibits the strong abilities of light absorption and light‐to‐heat conversion, superior adsorption capacities of reactants (H2, CO2), and an intermediate product (CO), which finally boosts CH4 formation. This work provides an efficient strategy to design a photothermocatalyst of CO2 methanation through utilizing MOFs‐derived support.

Application of bioisostere plays an important role in drug discovery. α‐Aminoboronic acid is the familiar bioisostere of α‐amino acid. Developing reactions for the synthesis of a wide variety of α‐aminoboronic acid is one important task for synthetic chemistry. Herein, we report the development of nucleophilic C‐borylation chemistry for N‐arylimines catalyzed by nickel. The reaction proceeds through the insertion of a borylnickel species into the C=N bond to afford the corresponding α‐aminoboronate, which was isolated as acetamide after trapping with acetic anhydride. N‐Benzyl imine is also tolerated by the developed reaction. [ABSTRACT FROM AUTHOR]

SP 1 sp H NMR (400 MHz, CDCl SB 3 sb ): = 8.09 (d, I J i = 8.7 Hz, 1 H), 7.77 (d, I J i = 8.0 Hz, 1 H), 7.69 (d, I J i = 8.8 Hz, 1 H), 7.49 (t, I J i = 7.3 Hz, 1 H), 7.38-7.30 (m, 2 H), 4.32 (s, 1 H), 3.86-3.63 (m, 2 H), 3.22-3.14 (m, 1 H), 3.14-3.03 (m, 1 H), 3.00 (s, 3 H), 2.72-2.58 (m, 2 H), 2.14-1.97 (m, 2 H), 1.71 (t, I J i = 12.7 Hz, 1 H), 1.66-1.57 (m, 1 H), 1.04 (t, I J i = 7.1 Hz, 3 H). SP 1 sp H NMR (400 MHz, CDCl SB 3 sb ): = 6.97 (d, I J i = 7.8 Hz, 1 H), 6.84 (d, I J i = 9.7 Hz, 2 H), 4.10-3.91 (m, 2 H), 3.25 (p, I J i = 6.0 Hz, 1 H), 3.03-2.85 (m, 2 H), 2.82 (s, 3 H), 2.71 (t, I J i = 11.9 Hz, 1 H), 2.51-2.38 (m, 1 H), 2.27 (s, 3 H), 1.93-1.68 (m, 3 H), 1.60 (d, I J i = 13.1 Hz, 1 H), 1.23 (t, I J i = 7.0 Hz, 3 H). SP 1 sp H NMR (400 MHz, CDCl SB 3 sb ): = (isomer 1) = 7.18 (q, I J i = 7.9 Hz, 1 H), 7.11-7.05 (m, 1 H), 6.98-6.87 (m, 2 H), 4.93 (ddd, I J i = 49.2, 7.8, 4.9 Hz, 1 H), 4.23-4.09 (m, 2 H), 3.34-3.25 (m, 1 H), 3.02-2.91 (m, 1 H), 2.90-2.79 (m, 1 H), 2.85 (s, 3 H), 2.79-2.62 (m, 1 H), 2.51-2.29 (m, 1 H), 1.85-1.72 (m, 2 H), 1.71-1.58 (m, 2 H), 1.28 (t, I J i = 7.1 Hz, 3 H); (isomer 2) = 7.18 (q, I J i = 7.8 Hz, 1 H), 7.11-7.05 (m, 1 H), 6.98-6.87 (m, 2 H), 4.54 (ddd, I J i = 49.8, 10.7, 2.6 Hz, 1 H), 4.23-4.09 (m, 2 H), 3.34-3.25 (m, 1 H), 3.02-2.91 (m, 1 H), 2.90-2.79 (m, 1 H), 2.84 (s, 3 H), 2.51-2.29 (m, 1 H), 2.06-1.92 (m, 1 H), 1.85-1.72 (m, 2 H), 1.71-1.58 (m, 2 H), 1.27 (t, I J i = 7.1 Hz, 3 H). SP 1 sp H NMR (400 MHz, CDCl SB 3 sb ): = 7.17 (dd, I J i = 8.5, 2.0 Hz, 1 H), 7.07 (d, I J i = 2.0 Hz, 1 H), 6.71 (d, I J i = 8.5 Hz, 1 H), 4.01 (q, I J i = 7.0 Hz, 2 H), 3.18 (p, I J i = 5.3 Hz, 1 H), 2.95-2.76 (m, 2 H), 2.73 (s, 3 H), 2.72-2.63 (m, 1 H), 2.38-2.25 (m, 1 H), 1.78-1.60 (m, 3 H), 1.59-1.50 (m, 1 H), 1.19 (t, I J i = 7.1 Hz, 3 H). [Extracted from the article]

Ni and Co catalysts supported on ITQ-6 zeolite have been synthesized and evaluated in the steam reforming of ethanol (SRE). Catalysts were also characterized by means of N 2 adsorption-desorption, XRD, H 2 -TPR, and H 2 -chemisorption. ITQ-6 containing Co (Co/ITQ-6) presented a higher conversion of ethanol and production of hydrogen than ITQ-6 containing Ni (Ni/ITQ-6). The lower size of the metallic cobalt particles shown in Co/ITQ-6 seems to be the major responsible of its higher catalytic performance. Regarding the reaction by-products (CO, CH 4 , C 2 H 4 O and CO 2), Co/ITQ-6 showed the lowest selectivity at medium and high temperatures (773 and 873 K). At low reaction temperatures (673 K) the dehydrogenation reaction predominates in the Co/ITQ-6, what it is supported by the high concentration of acetaldehyde detected at this temperature. In the case of the Ni/ITQ-6 the main side reaction at 673 K seems to be the methanation reaction since large concentrations of methane are detected. Stability studies were also carried out showing lower deactivation of Co/ITQ-6 at large reaction times (24 h). Characterization of the exhausted catalysts after reaction showed the presence of coke in both catalysts. Nevertheless, Co/ITQ-6 presented the lowest coke deposition. In addition, Co/ITQ-6 exhibited the lowest metal sinterization, what could be also account for the lower deactivation exhibited by this sample. This fact could be related to the higher interaction between the cobalt metallic particles and the ITQ-6 support as the H 2 -TPR studies demonstrate. • Ethanol steam reforming catalysts based on Co or Ni supported on ITQ-6 zeolite is prepared by the first time. • Higher ethanol conversion and hydrogen selectivity is exhibited by the catalyst with Co. • The lower size of the metal Co particles is the major responsible of its higher catalytic activity. • Higher stability is exhibited by the Co catalyst (lower coke deposition and sinterization of the metallic particles). [ABSTRACT FROM AUTHOR]

Cellulose is one of the main components of plant matter, which makes it a viable target for biomass conversion to fuels. The direct conversion of cellulose to methane utilizing nickel‐based catalysts often has challenges associated with it. Carbon agglomeration creating nickel‐carbon nanoparticles deactivating catalytic hydrogenation of cellulose has been well reported. Utilizing rare‐earth metals as promoters increases the conversion of cellulose to methane, albeit with deactivation of the catalyst in the form of nickel‐rare‐earth‐carbon nanoparticles. Adding an additional zinc metal promoter eliminates the carbon agglomeration and allows for increased methane yields. Herein, we report an 81 % methane yield from cellulose in 48 hours utilizing a Ni/Zn/Y/Al2O3 catalyst at 225 °C and under 50 bar H2 pressure. [ABSTRACT FROM AUTHOR]

The catalytic hydrogenation of nitroarenes using hydrogen gas as reducing agent to form substituted aniline derivates is an important reaction in industry and academic research. Here, we report on the nitroarene hydrogenation capability of a nanostructured nickel catalyst synthesized from a nickel salen complex and a commercially available porous silica support. Our catalyst allows the selective hydrogenation of nitroarenes under mild conditions while tolerating various functional groups and hydrogenation‐sensitive examples such as iodine, nitrile or olefinic groups. The use of the nickel salen complex as metal precursor is crucial for the high activity and selectivity observed. [ABSTRACT FROM AUTHOR]

The hydrotreating of kerosene was studied to develop a crude kerosene distillate to produce products with specifications suitable for marketing as kerosene and rocket grade fuel. To saturate the aromatic structures from kerosene, hydrogenation experiments were carried out in a batch steel reactor with different amounts (20 ml and 40 ml) of crude kerosene, using silica-supported nickel and kieselguhr supported nickel-sulfur catalysts. The catalysts were analyzed with Brunauer, Emmett ve Teller (BET), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and x-ray diffraction analysis (XRD). The aromatic fractions and paraffin structures content of the obtained samples were examined. The experiments were carried out at 200–220 °C temperature with 5 bar hydrogen initial pressure for 2 h. The obtained products were analyzed by performing a 1H NMR analysis. According to proton NMR result, the ratio of paraffinic methylene, beta methyl, epsilon methylene groups of 20 ml crude kerosene with kieselguhr supported nickel-sulfur is more than 4.5 times compared to crude kerosene, and % the percentage of aromatic hydrogen structures of it is two times lower. As a result of hydrogenation experiments with both nickel-based catalysts, aromatic hydrogen structures in crude kerosene were reduced. The total H/C ratio of rocket grade hydrocarbon fuels increased after hydrogenation experiments. For this reason, the scope of ongoing research can be extended to hybrid rocket propellants (SP-1) used in hybrid rocket engines. • The total H/C ratio of rocket grade fuels increased after hydrogenation experiments. • Doubling kerosene amount with kieselguhr catalyst reduces the hydrogenation rate. • Paraffinic groups of the samples increased compared to the unrefined kerosene. • Research can be extended to hybrid rocket propellants (SP-1) used in rocket engines. [ABSTRACT FROM AUTHOR]

This study focuses on the development and optimization of nanostructured anode electrodes for solid oxide fuel cells (SOFCs) by infiltration method. Ni (nickel) catalyst in the form of a nickel nitrate solution is infiltrated into porous YSZ (yttria stabilized zirconia) backbone fabricated by tape casting. Numerous electrolyte-supported cells are fabricated to investigate the effects of several significant infiltration fabrication parameters such as catalyst loading and infiltration sintering temperature. Conventional cell with screen printed Ni-YSZ anode is also fabricated for comparison. Electrochemical performances and microstructural properties of the cells are examined and evaluated. The best peak performance of 0.398 W/cm2 at 800 °C is obtained from the cell, which is infiltrated 9 times with 2 M solution followed by firing at 800 °C. The conventional cell, on the hand, exhibits only 0.174 W/cm2 under the same testing conditions in spite of the relatively higher Ni catalyst content in the anode. Furthermore, the optimized cell produces 0.169 W/cm2 maximum power density at 700 °C. The overall results reveal that nickel catalyst infiltration is a very effective method to improve the cell performance by providing increased number of electrochemical reaction zones within the anode electrode due to nanostructured nickel catalyst formed around the main YSZ phase. [ABSTRACT FROM AUTHOR]

An efficient temperature control C−S and C−N bond formation under mild nickel‐catalysed domino cross‐coupling conditions is described. The advantages of this approach are good functional group compatibility, cheaper nickel catalyst, and use of mild base. In addition, to the best of our knowledge this methodology is the first successful example of nickel‐catalysed synthesis of 2‐Arylsulfonyl Aryl cyanamides and 2‐Aminophenyl Benzothiazole. [ABSTRACT FROM AUTHOR]

Copper and iron-based bimetallic nickel catalysts supported on Mesostructured Silica Nanoparticles (MSNs) with compositions of 50% Ni–5% Cu/MSN and 50% Ni–5% Fe/MSN were prepared using an impregnation method, and they were compared with a monometallic 50% Ni–MSN catalyst for their activity and stability in methane decomposition reaction. The influence of promoters, such as Cu and Fe, at different reaction temperatures (700 °C, 800 °C and 900 °C) was investigated. The results revealed that the Cu and Fe-promoted catalysts significantly increased the hydrogen yield in methane decomposition compared with the unpromoted catalyst. This could be attributed to the formation of Ni–Cu and Ni–Fe bimetallic alloys in the catalysts, respectively, and this favored the stability of the catalysts. With increasing reaction temperature, the hydrogen yield also increased. However, the hydrogen yield and the lifetime of the nickel catalyst were enhanced upon the addition of iron compared to copper at all the reaction temperatures. The analysis conducted over the spent catalysts validated the formation of multi-walled carbon nanotubes with a bamboo-like internal channel over the catalysts along with a high crystallinity and graphitization degree of the carbon produced. [ABSTRACT FROM AUTHOR]

Catalytic methane (CH4) dry reforming (MDR) reaction proceeds with the formation of carbon; hence the effects of the catalyst preparation method on the type of carbon are worth investigating. This study investigated the performance of 20 wt% nickel praseodymium (III) oxide (20 wt% Ni/Pr2O3) catalysts prepared by incipient wetness impregnation (IWI), ultrasonic wet impregnation (US-WI), and Pechini sol–gel (PSG) methods. The catalysts crystallite size was approximately 21.3 nm, 21.3 nm, and 10.6 nm, for IWI, US-WI, and PSG catalysts, respectively. Study of the temperature effecton the MDR system showed that higher temperatures favored the MDR reaction with the side reaction playing vital roles. The catalyst synthesized by the PSG method showd higher carbon gasification rate with the stability up to 24 h, whereas catalysts from other synthesis methods were only active for less than 2 h, which could be due to the formation of higher amount of filamentous carbon, balance in oxygen species, and the smaller crystallite size of the PSG-20 wt% Ni/Pr2O3. The PSG-20 wt% Ni/Pr2O3 catalyst accumulated more filamentous carbon than graphitic carbon. In contrast, the IWI and US-WI catalysts accumulated mainly graphitic carbon which encapsulated the Ni0 sites, resulting in excess carbon deposition and reactor clogging within 2 h on stream. [ABSTRACT FROM AUTHOR]

Biomass valorization is an essential strategy for converting organic resources into valuable energy and chemicals, contributing to the circular economy, and reducing carbon footprints. Glycerol, a byproduct of biodiesel production, can be used as a feedstock for a variety of high-value products and can contribute to reducing the carbon footprint. This study examines the impact of surface-level modifications of Mg, Cu, and Sn on Ni-Ce-Zr catalysts for the hydrogenolysis of glycerol, with in situ generated hydrogen. The aim of this approach is to enhance the efficiency and sustainability of the biomass valorization process. However, the surface modification resulted in a decrease in the global conversion of glycerol due to the reduced availability of metal sites. The study found that valuable products, such as H2 and CH4 in the gas phase, and 1,2-PG in the liquid phase, were obtained. The majority of the liquid fraction was observed, particularly for Cu- and Sn-doped catalysts, which was attributed to their increased acidity. The primary selectivity was towards the cleavage of the C–O bond. Post-reaction characterizations revealed that the primary causes of deactivation was leaching, which was reduced by the inclusion of Cu and Sn. These findings demonstrate the potential of Cu- and Sn-modified Ni-Ce-Zr catalysts to provide a sustainable pathway for converting glycerol into value-added chemicals.

The binder jetting printing technique enables in situ impregnation of alumina using a Ni(NO3)2-containing ink (NI), facilitating omission of impregnation. NI was compared to wet impregnation (WI). Full characterization by quasi-in situ XPS, XAS and TPR revealed the presence of Ni as NiAl2O4 spinel. TPR analysis identified surface NiO and NiAl2O4 species with facilitated reduction by NI, in addition to the respective species in bulk form. Post-processing affects active site accessibility by coverage. 3D printing limited the Ni loading, but XPS revealed higher metal dispersion by NI. CO2 hydrogenation confirmed active Ni/Al2O3 catalysts with enhanced activity by NI.

2 and 5 wt.% nickel was supported on different MgO to Al 2 O 3 (M/A) ratios (0.5, 1 and 1.5) and evaluated in reverse water gas shift (RWGS) reaction. The catalysts were prepared by impregnation method and the nanocrystalline supports were synthesized by simple surfactant (CTAB) assisted precipitation technique. The following catalytic activity was observed for 2% & 5% Ni supported on different M/A ratios; M/A = 1 > M/A = 1.5 > M/A = 0.5. The perceived order was related to difference in the structural properties of supports and catalysts. The BET results revealed decrease of specific surface area with increase in M/A ratio, mesoporous structure for M/A = 0.5 and 1 and meso-macroporous structure for M/A = 1.5. The effect of nickel loading on the support with M/A = 1 was also investigated. 1.5% Ni showed high CO 2 conversion of 39.2% at 700 °C and CO selectivity higher than 90% at all temperatures. Increase of nickel loading higher than 1.5% was in favor of CH 4 formation. The TEM images of 1.5% Ni on M/A = 1 revealed uniform distribution of Ni particles with average size of 4.9 nm. The H 2 -TPR analysis displayed shifting of maximum temperature of the main peak (γ) to higher temperatures with increase of M/A ratio in the support, indicating harder reducibility of catalysts with higher MgO content. The 1.5% Ni supported on M/A = 1 (MgAl 2 O 4) showed great catalytic stability and CO selectivity (>98%) after 15 h on stream. • MgO/Al 2 O 3 (M/A) supports were prepared by CTAB assisted co-precipitation method. • 2 &5 wt.% Ni were supported on different M/A ratios and evaluated in RWGS reaction. • The following catalytic activity M/A = 1 > M/A = 1.5 > M/A = 0.5 was observed for catalysts. • Optimization of Ni loading was performed on the support with M/A = 1. • 1.5% Ni on M/A = 1 showed CO selectivity >90% at all temperatures (400 °C < T < 700 °C). [ABSTRACT FROM AUTHOR]

Ruthenium/nickel ex-solved perovskite catalysts have been synthesized by incipient impregnation. As-synthesized and spent catalysts have been characterized by XRD, TPR-H 2 , SEM-EDX and TEM analyses. Reduced catalysts have been tested in the autothermal reforming of ethanol, in the temperature range of 600–800 °C. All tested catalysts gave the total conversion of ethanol in the range of investigated temperatures, confirming the oxidative ability and oxygen storage capacity of perovskite, that promotes the catalyst activation. The highest hydrogen yield (83%) is obtained by ruthenium/nickel ex-solved perovskite containing the 0.5 wt% of Ru (SFMN/0.5Ru catalyst) at 600 °C. Increasing the amount of Ru in the catalyst an inhibiting effect is observed: high Ru content modifies the metal species and their reducibility. H 2 yield strongly decreases (lower than the 50%) for the catalyst containing the 1 wt% of ruthenium (SFMN/1Ru catalyst), at all the reaction temperatures tested. At 600 °C, were the highest H 2 yield is registered, the coke deposition increases with this order: SFMN/1Ru< SFMN/0.5Ru< SFMN, confirming the positive role of noble catalyst toward the inhibition of carbon species formation. By comparison of all catalytic aspects (ethanol conversion, hydrogen yield, coke deposition and stability) the catalyst showing the best performance is ruthenium/nickel ex-solved perovskite with 0.5 wt% of Ru content (SFMN/0.5Ru). • Ruthenium/nickel ex-solved perovskite catalyst gave complete ethanol conversion above 600 °C. • The highest H 2 selectivity is obtained by SFMN/0.5Ru catalyst. • 0.5% loading noble metal catalysts are suitable for autothermal reforming of ethanol with low carbon formation. • The Ru-containing catalyst is stable for 15 h of reaction and can be reused after regeneration. [ABSTRACT FROM AUTHOR]

Branched polyolefins with controllable topology structures were generated from the chain-walking (co)polymerizations of ethylene, 1-pentene (1P) and 2-pentene (2P) using Brookhart-type a-diimine Ni(II)-based catalysts possessing different para-substituted groups, {[(4-R-2-Et-6-Me-C6H2N = C)2Nap]NiBr2, Nap: 1,8-naphthdiyl; R = CHMePh, Ni1; R = Ph, Ni2; R = H, Ni3}. The X-ray diffraction analysis demonstrated that the crystalline structure of Ni1' is in centrosymmetric dimer structure mode with the bimetallic Ni center connected by two bromide bridges. The para-sec-phenethyl moiety in the catalyst Ni1 obviously improved its catalytic performance and thermal stability in the ethylene polymerization. The Ni1/Et2AlCl system showed great catalytic activities (up to 7.73×106 g·mol−1·h−1) and achieved polyethylene (PE) with alkyl chains, including Me, Et, n-Pr, n-Bu, sec-Bu branches and longer chains (Lg). Compared with the 1-pentene polymerization, this catalyst system successfully mediated the polymerization of 2P to give highly branched polymers with approximately 195 branches/1000C possessing Me, Et, and n-Pr branches and a long methylene sequence due to the monomer isomerization. The Et branches derived from 2,3-insertion is slightly less than the sum of Me and n-Pr branches derived from 3,2-insertion, indicating that the 3,2-insertion mode is a slightly favorable pathway in the polymerization of 2P. [ABSTRACT FROM AUTHOR]

This study aims to utilize biochars derived from residual biomass as supports for Ni-based catalysts. For the preparation of the biochars, byproducts of agro-industrial activities were used, such as espresso coffee residue (C) and rice husks (R). Sufficient quantities of the respective biochars (BioC and BioR) were prepared via pyrolysis at 850 °C of the aforementioned materials under limited oxygen conditions. The biochars were further treated with hot water (WBioC, WBioR), H3PO4 or H2SO4 solution (BioC-P, BioC-S, BioR-P, BioR-S), and NaOH solution (BioC-A and BioR-A), and the obtained solids were characterized using various physicochemical techniques. The biochars produced were microporous with high surface areas (367–938 m2g−1). The most promising biochars were selected as supports for the preparation of nickel catalysts (10 wt.% Ni) with high Ni dispersion (mean crystal size: 8.2–9.8 nm) and suitable acidity. The catalysts were evaluated in a high-pressure semi-batch reactor for the transformation of waste cooking oil (WCO) into green diesel. The 10Ni_BioC-P catalyst exhibited the best performance, resulting in a complete conversion of the WCO but a low hydrocarbon yield (7.5%). Yield improvement was achieved by promoting this catalyst with molybdenum. The addition of Mo increased the hydrocarbon yield by almost three times (19.5%). [ABSTRACT FROM AUTHOR]