Carbon-supported Ni Catalysts Research Articles

Oxidative Amidation of Aldehydes with an N-Doped Carbon-Supported Ni Catalyst

Oxidative Amidation of Aldehydes with an N-Doped Carbon-Supported Ni Catalyst

Co-pyrolysis induced strong metal-support interaction in N-doped carbon supported Ni catalyst for the hydrogenolysis of lignin

Designing highly active and stable catalysts for the selective cleavage of the C-O bond of lignin is important to convert it into high-valued aromatic compounds. Herein, a facile synthetic strategy was developed using melamine as a soft template to prepare a highly active catalyst consisting of highly dispersed Ni nanoparticles on defective N-doped carbon support. The results indicated that the decomposition of melamine during the pyrolysis process induced the nitrogen atoms into aromatic carbon. The introduction of N-doped carbon support acted as anchor points for the Ni nanoparticles, strengthening the metal-support interaction. Approximately 100 conversion of the representative lignin model compounds, including 2-phenylethyl phenyl ether, were converted into their aromatic monomers under mild conditions. The as-prepared catalyst was stable and reusable after five cycles with no apparent signs of deactivation. Moreover, the theoretical calculation revealed that N-doped carbon supported Ni-based catalyst possessed a lower activation energy of C-O bond than only carbon supported Ni-based catalyst for the C-O bond cleavage in hydrogenolysis of lignin and its model compounds.

Coal char supported Ni catalysts prepared for CO2 methanation by hydrogenation

Catalytic CO2 methanation is a potential solution for conversion of CO2 into valuable products, and the catalyst plays a crucial role on the CO2 conversion and CH4 selectivity. However, some details involved in the CO2 methanation over the carbon supported Ni catalysts are not yet fully understood. In this work, commercial coal char (CC) supported Ni catalysts were designed and prepared by two different methods (impregnation-thermal treatment method and thermal treatment-impregnation method) for CO2 methanation. Effects of the preparation conditions (including the thermal treatment temperature and time, the mass ratio of CC:Ni and the preparation method), as well as the reaction temperature of CO2 methanation, were investigated on the catalyst morphology, reducibility, structure and catalytic performance. Fibrous Ni-CC catalyst is achieved and shows high CO2 conversion (72.9%–100%) and CH4 selectivity (>99.0%) during the 600-min methanation process. Adverse changes of the catalyst surface and textural properties, reducibility, particle size and morphology are the potential factors leading to the catalyst deactivation, and possible solutions resistant to the deactivation were analyzed and discussed. The CO2 methanation mechanism with the CO route was proposed based on the oxidation-reduction cycle of Ni in this work.

Selective cleavage of C–O bond in lignin and lignin model compounds over iron/nitrogen co-doped carbon supported Ni catalyst

The utilization of lignin to produce high value-added chemicals is conducive to alleviating the fossil energy crisis. Herein, Ni nanoparticles supported on iron/nitrogen co-doped carbon was prepared by co-pyrolysis and solvothermal reduction method for catalytic hydrogenolysis (CH) of dealkaline lignin and its model compounds. The catalysts were prepared under different calcination temperature, N/C ratio and Ni loading, and the optimal catalyst was Ni10%@Fe/NC0.33–800 (calcination temperature: 800 °C, N/C ratio: 0.33, Ni loading: 10%) based the on the CH of benzyl phenyl ether (BPE). Ni10%@Fe/NC0.33–800 showed good catalytic performance on the selective cleavage of C-O bond of lignin and its model compounds. The BPE conversion reached up to 97.7% over Ni10%@Fe/NC0.33–800 under mild conditions (230 °C, 1 MPa H2, and 0.5 h) with toluene and cyclohexanol as major products. Catalyst characterizations suggest that N content affects the formation of NiFe alloy and the synergistic effect between Ni and Fe plays an important role in CH of BPE. Moreover, Ni10%@Fe/NC0.33–800 could promote the cleavage of C-O bonds in dealkaline lignin through CH and hence enhance producing aromatics such as phenols, aromatic ethers, and aromatic esters, among which phenols are the main aromatics with guaiacols predominant.

Electronic Ni–N interaction enhanced reductive amination on an N-doped porous carbon supported Ni catalyst

Reductive amination on Ni/N-doped porous carbon catalyst was enhanced by the formation of Ni–Nx sites and the electronic interaction of N and Ni species, which promoted the reductive amination of CO bonds and reduced the activation energy.

Hydrothermal carbon-supported Ni catalysts for selective hydrogenation of 5-hydroxymethylfurfural toward tunable products

5-hydroxymethylfurfural (HMF), as one of the most important renewable platform-chemicals, is a valuable precursor for the synthesis of biofuels and bio-products. In this work, hydrothermal carbon (HC), with a large specific surface area and plenty of oxygen-containing functional groups, was derived from sucrose via a hydrothermal method, which could facilitate the dispersion and anchoring of Ni. The selectivities to 2,5-bis(hydroxymethyl)furan (BHMF), 2,5-dimethyltetrahydrofuran (DMTHF), and 2,5-dimethylfuran (DMF) were tuned by modulating Ni nanoparticle sizes and Ni/NiO ratios. The yield of BHMF can reach 88% with its selectivity up to 94% on the reduced 10%-Ni/HC catalyst with big Ni particle size; while the total yield of DMF + DMTHF is up to 94.6% at full HMF conversion on the calcined 5%-Ni/HC catalyst with small Ni particle sizes and balanced Ni/NiO ratios; for the calcined Ni/HC catalysts, the synergistic effect between Ni(0), favoring H2 activation and hydrogenation, and NiO, facilitating the hydrogenolysis of C–O bonds, could promote the selective hydrogenolysis of HMF to biofuel production (DMF and DMTHF).

Metal\u2013organic framework\u2013derived Ni@C and NiO@C as anode catalysts for urea fuel cells

Highly porous self-assembled nanostructured Ni@C and NiO@C were synthesized via calcination of a Ni-based metal–organic framework. The morphology, structure, and composition of as synthesized Ni@C and NiO@C were characterized by SEM, FIB-SEM, TEM, and XRD. The electro-catalytic activity of the Ni@C and NiO@C catalysts towards urea oxidation was investigated using cyclic voltammetry. It was found that the Ni@C had a higher residual carbon content and a higher specific surface area than NiO@C, thus exhibiting an enhanced electrochemical performance for urea oxidation. A direct urea fuel cell with Ni@C as an anode catalyst featured an excellent maximum power density of 13.8 mW cm−2 with 0.33 M urea solution in 1 M KOH as fuel and humidified air as oxidant at 50 °C, additionally showing excellent stability during continuous 20-h operation. Thus, this work showed that the highly porous carbon-supported Ni catalysts derived from Ni-based metal–organic framework can be used for urea oxidation and as an efficient anode material for urea fuel cells.

The role of surface properties in CO2 methanation over carbon-supported Ni catalysts and their promotion by Fe

CO2 methanation over activated carbon-supported Ni catalysts with enhanced surface chemistry properties and their improved performance by Fe promotion.

Biomass-derived carbon-supported Ni catalyst: an effective heterogeneous non-noble metal catalyst for the hydrogenation of nitro compounds

The biomass-derived carbon material supported Ni catalysts (Ni/C) demonstrated a high catalytic activity for the hydrogenation of nitro compounds into primary amines at room temperature.

Highly active carbon-supported Ni catalyst prepared by nitrate decomposition with a sacrificial agent for the hydrogen oxidation reaction in alkaline medium

Ketjenblack EC-600 JD supported Ni/C electrocatalysts with a nickel content of 50 and 60 wt% were prepared by impregnation with either Ni(OAc)2 or a mixture of Ni(OAc)2 and Ni(NO3)2 precursors, followed by freeze-drying and reduction with H2. XRD, TEM and cyclic voltammetry were applied for characterizing the catalysts. The use of Ni(OAc)2 as a sacrificial agent during decomposition of Ni(NO3)2 allows one to decrease significantly the size of nickel nanoparticles (from 37 to 12 nm) at a very high metal loading. Benefiting from the high dispersion and high specific activity, 60 % Ni/Ketjenblack EC-600 JD possesses remarkable mass activity (7 A∙g−1Ni) in the hydrogen oxidation reaction in an alkaline electrolyte.

N-doped porous carbon supported Ni catalysts derived from modified Ni-MOF-74 for highly effective and selective catalytic hydrodechlorination of 1,2-dichloroethane to ethylene

Metal-organic frameworks (MOFs) have received significant attention as promising precursors or sacrificial templates in the preparation of porous carbon supported catalysts. In this study, N-doped porous carbon supported Ni catalysts (denoted as Ni/NC) were prepared using furfuryl alcohol (FA) loaded Ni-MOF-74 as the precursor followed by NH4OH treatment and pyrolysis under N2 atmosphere. For comparison purpose, Ni catalysts supported on porous carbon (denoted as Ni/C) were also prepared by direct pyrolysis of Ni-MOF-74. The selective gas phase catalytic hydrodechlorination of 1,2-dichloroethane to ethylene was carried out to evaluate the catalytic performances of the catalysts. It was found that for Ni catalysts prepared at the same pyrolysis temperature, Ni particle sizes in Ni/NC catalysts were significantly smaller (20–40% smaller) than that of Ni/C. This reflected that pre-modification of Ni-MOF-74 using FA and NH4OH could effectively increase Ni dispersion in Ni catalysts derived from Ni-MOF-74. Moreover, Ni/NC had a markedly stronger ability to form spillover H2 owing to the enhanced metal-support interactions by N-doping. Accordingly, Ni/NC catalysts exhibited much higher catalytic activities than Ni/C catalysts. The turnover frequencies of Ni/NC catalysts were found to be 1.22–1.65 times higher than Ni/C catalysts. Increasing pyrolysis temperature led to decreased catalytic activities of both Ni/C and Ni/NC catalysts, due to the aggregation of Ni particles at higher treatment temperature. The findings from this study demonstrate that the MOF-mediated synthesis method offers a promising way to prepare Ni-based catalysts for catalytic hydrodechlorination of chlorinated hydrocarbons.

Non-thermal plasma enhanced dry reforming of CH4 with CO2 over activated carbon supported Ni catalysts

In this paper, the dry reforming of methane and carbon dioxide (DRM) under plasma assisted with nickel (Ni)/activated carbon (AC) catalyst was investigated. In order to determine the synergistic effect of plasma and catalyst, DRM under plasma without catalyst, catalyst alone, and plasma assisted with catalyst was separately studied. The experimental results demonstrated that the highest catalytic activity was achieved when DRM was run under plasma combined with Ni/AC catalyst, and carbon dioxide (64.6%) and methane (65.7%) conversion, as well as the yield of hydrogen (27.9%), carbon monoxide (32.5%) were obtained. Moreover, the AC reduced at 700 °C was regard as the optimum support for DRM, NiC700 under plasma condition exhibited the best performance of DRM ascribed to its mesopores structure, higher specific surface area, and stronger metal-support interaction (SMSI) between Ni and AC support.

Layered uniformly delocalized electronic structure of carbon supported Ni catalyst for catalytic reforming of toluene and biomass tar

Lignite rich in oxygen-containing species (OCSs) was employed as perfect ion-exchange material for high activity catalyst preparation. HCl treatment Shengli lignite (HSL) selectively removed the organic salt and improved capability of ion exchange. In this paper, highly desirable and layered carbon supported Ni catalyst was prepared by modified lignite. Thanks to the excellent role of Ni (1 1 1) plane and porous layered graphene-like delocalized electronic structure, specific structure of lignite provides an exchange platform in facilitating the Ni electron transfer during the catalytic reaction process. Ni loaded on HSL (Ni/HSL) showed the great catalytic activity and stability for reforming of toluene and biomass tar. Ni/HSL prepared at 650 °C shows the great activity and stability for toluene steam reforming (TSR) and biomass tar reforming (BTR). A series of instruments (XRD, SEM, TEM, H2-TPR, XPS, CO pulse adsorption, etc.) were employed for characterization. Based on these significant characterizations of catalyst, calculation of turnover frequency (TOF), and results of conversion of toluene and corncob tar. The results revealed the layered delocalized electronic structure of Ni/HSL, which has lower activation energy than other reported catalysts. Uniform dispersed catalyst was synthesized successfully for reforming of toluene and biomass tar.

Hydrothermal reaction of tryptophan over Ni-based bimetallic catalysts

The major products from hydrothermal reactions of tryptophan at 350 and 400 °C in the absence of catalyst were indole and methyl indoles, indicating simultaneous deoxygenation and deamination. In the presence of carbon-supported Ni and NiM catalysts (M = Ru, Cu, Pd, Pt) primary aromatic amines also appeared, via cleavage of the heterocyclic ring of the indoles. Ni and NiCu catalysts have the lowest selectivity for the formation of this family of compounds, while NiRu had the highest selectivity. Catalysts containing noble metals also produced monosubstituted alkylaromatics, due to the deamination of the aromatic amines, with the NiPt catalyst providing the highest molar yield (∼7%). We propose catalytic and non-catalytic hydrothermal reaction pathways for tryptophan based on the observed product distributions. The bimetallic particles were smaller than the pure Ni particles and the surfaces of NiRu and NiPd particles were enriched in Ni, relative to the nominal bulk composition.

Macroporous–mesoporous carbon supported Ni catalysts for the conversion of cellulose to polyols

The macro–mesoporous carbon supported Ni catalysts (Ni/MMC) are synthesized to effectively promote cellulose conversion.

Effect of atomic-layer-deposited TiO2 on carbon-supported Ni catalysts for electrocatalytic glycerol oxidation in alkaline media

Thin TiO2 layers were deposited onto a carbon-supported Ni catalyst (Ni/C) through atomic layer deposition (ALD) and the resulting TiO2-coated Ni/C (ALD(TiO2)-Ni/C) was utilized for electrochemical glycerol oxidation in alkaline media. X-ray photoelectron spectroscopy analysis demonstrated that the Ni surface phase of ALD(TiO2)-Ni/C mainly consisted of Ni(OH)2 while that of uncoated Ni/C was a mixed phase of NiO and Ni(OH)2. The ALD(TiO2)-Ni/C exhibited electrocatalytic activity at least 2.4 times higher than that of Ni/C. Density functional theory calculations were used to investigate how the modified Ni surface with the TiO2 coating affects the adsorption/desorption of glycerol.

Multicomponent NiSnCeO2/C catalysts for the low-temperature glycerol steam reforming

In this work, the low-temperature hydrogen production via glycerol steam reforming over activated carbon-supported Ni and Ni-Sn catalysts promoted by ceria was studied. A combination of N2 adsorption, powder X-ray diffraction, temperature-programmed reduction with H2, X-ray photoelectron spectroscopy and TEM analysis were used to characterise the Ni-Sn-CeO2 interactions and the CeO2 dispersion over the activated carbon support. The catalytic activity results show that the presence of ceria enhances the water-gas shift reaction, thus promoting the selectivity towards hydrogen. The inclusion of Sn stresses the influence of ceria in the displayed performance. Moreover, the formation of a Ni-Sn alloy seems to be an efficient way to mitigate Ni sintering and therefore to improve the overall catalyst’s stability.

Preparation of mesoporous activated carbon supported Ni catalyst for deoxygenation of stearic acid into hydrocarbons

Deoxygenation of stearic acid has been investigated over the supported Ni nanoparticles on the mesoporous activated carbon (MAC) under relatively mild conditions (260°C), where the MAC was obtained from Kraft lignin by H3PO4 activation. The precursor and catalyst have been characterized by X-ray diffraction (XRD), N2 adsorption–desorption measurements and transmission electron microscopy (TEM). The influence of the H2 pressure, Ni loading, reaction time, and initial concentration of stearic acid on the composition and yield of hydrocarbons has also been checked. A high C17 to C18 hydrocarbons yield of 81.3%, a C17 hydrocarbon selectivity of 94%, and a conversion of 100% were obtained at 260°C, 6 bar H2 pressure, and stearic acid concentration of 0.15 mol/L after 10 h of reaction time over the 25 wt % Ni/MAC catalyst. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 607–612, 2015

Hydrothermal gasification of phenol water on novel carbon-supported Ni catalysts prepared by the sol–gel method using tartaric acid and alminum tri-sec-butoxide

The purpose of this study is to prepare novel carbon-supported Ni (Ni/C/Al2O3) catalysts by the sol–gel method and to perform the hydrothermal gasification of phenol water as a model of wastewater. Catalysts were prepared by the combination of aluminum tri-sec-butoxide (ASB) and tartaric acid as an organic template and the addition of active metal, nickel nitrate hexahydrate at the preparation of catalysts. After calcination under the nitrogen atmosphere, the larger amounts of active metal species were built at the carbon skeletal in the catalysts. Introduction of tartaric acid dispersed metal Ni with high loading on carbon derived from ammonium tartrate. Hydrothermal gasification was performed under the following conditions: 350°C, pressure of 20MPa, phenol water of 2–20 g/L, and LHSV of 48h−1. 16N63C21A catalyst, which represents 16wt.% Ni, 63% carbon in tartalic acid, and 21% Al2O3 at the preparation of the catalyst, showed the highest activity and the highest carbon balance between feed and products within 8 h among all the Ni catalysts. The activity of each catalyst increased with the elapse of time and the phenol conversion reached 100 % under the condition and phenol concentration of 2g/L. No deactivtion was observed.

Control of selectivity, activity and durability of simple supported nickel catalysts for hydrolytic hydrogenation of cellulose

Efficient conversion of cellulose to sorbitol and mannitol by base metal catalysts is a challenge in green and sustainable chemistry, but typical supported base metal catalysts have not given good yields of hexitols or possessed durability. In this study, it has been demonstrated that a simple carbon-supported Ni catalyst affords up to 67% yield of hexitols in the conversion of cellulose, and that the catalyst is durable in the reuse experiments 7 times. In addition, the catalyst can be separated by a magnet thanks to a high content of Ni. Physicochemical analysis has indicated that the use of carbon supports has two benefits: no basicity and high water-tolerance. CeO2, ZrO2, γ-Al2O3 and TiO2 cause side-reactions due to basicity, and SiO2, γ-Al2O3 and CeO2 are less stable in hot water. Another important factor is high Ni loading as the increase of Ni content from 10 wt% to 70 wt% significantly improves the yield of hexitols and the durability of catalysts. Larger crystalline Ni particles are more resistant to sintering of Ni and surface coverage by Ni oxide species.