Dispersed Nickel Research Articles

Conversion of Biomass-Derived Tars in a Fluidized Catalytic Post-Gasification Process

The present study deals with the development, characterization, and performance of a Ni-based catalyst over a ceria-doped alumina support as a post-gasification step, in the conversion of biomass-derived tars. The catalysts were prepared using the incipient wetness technique and characterized chemically and physically using NH3-TPD, CO2-TPD, H2-TPR, XRD, Pyridine-FTIR, N2 physisorption, and H2-Pulse Chemisorption. It was observed that the 5 wt% CeO2 reduced the strong and very strong acid sites of the alumina support and helped with the dispersion of nickel. It was noticed that the nickel crystallite sizes and metal dispersion remained unchanged as the nickel loading increased. The performance of the catalysts was studied in a mini-fluidized CREC Riser Simulator at different temperatures and reaction times. The selected tar surrogate was 2-methoxy-4-methylphenol, given its functional group similarities with lignin-derived tars. A H2/CO2 gas blend was used to emulate the syngas at post-gasification conditions. The obtained tar surrogate conversion was higher than 75%, regardless of the reaction conditions. Furthermore, the catalysts used in this research provided an enhancement in the syngas product composition when compared to that observed in the thermal experiments. The presence of hydrocarbons greater than CH4 (C1+) was reduced at 525 °C, from 96 ± 3% with no catalyst, to 85 ± 2% with catalyst and steam, to 68 ± 4% with catalyst and steam-H2/CO2. Thus, the catalyst that we developed promoted tar cracking, tar reforming, and water-gas shift reactions, with a H2/CO ratio higher than 3.8, providing a syngas suitable for alcohol synthesis.

Hydrogenation of glucose to sorbitol by using nickel hydroxyapatite catalyst

AbstractA series of nickel hydroxyapatite catalysts were synthesized by the co‐precipitation method followed by calcination and reduction. These catalysts were employed for the aqueous phase hydrogenation of glucose to sorbitol. The Ni‐HAP catalyst with comparatively high surface area and acid‐base strength gave high sorbitol selectivity in 1 h. Ni‐HAP‐4 catalyst with moderate Ni (3.5 wt. %) content having smaller and highly dispersed nickel particles gives an excellent yield of sorbitol, 97 % in 1 h. The Ni‐HAP‐4 catalyst works well with other polar protic solvents. Different characterization techniques like XRD, TEM, SEM‐EDS, BET, NH3‐TPD, and CO2‐TPD were employed to analyze the Ni‐HAP‐4 catalyst.

Atomic level dispersed nickel coupled with silver nanoparticle to boost the efficiency of CO2 conversion to CO via spin electrons regulation

Modulating the electronic configuration by coupling multi-scale active sites for electrocatalytic conversion of CO2 to CO is extremely challenging in terms of structural analysis and mechanism elucidation. Herein, a catalyst NiAD/AgNPs@CN with both atomic-level dispersed Ni and Ag nanoparticles on N-doped carbon substrate has been designed to reveal the true active sites and catalytic mechanism in complex materials. NiAD/AgNPs@CN exhibits CO Faraday efficiency (FECO) of 99.97% at −0.88 V (vs. RHE) in H-type cell and 91.77% FECO with a high current density of 79.70 mA/cm2 in flow cell. DFT calculations show that the tiny change in the energy level of spin electrons at atomic sites has a significant impact on the CO2 activation. The regulation of atomic Ni on Ag sites is the main reason for improving CO2RR performance. This work gives a new understanding on the catalytic mechanism of composite materials structured by atomic-level dispersed metal and nanoparticles.

Catalytic Supercritical Water Gasification of Canola Straw with Promoted and Supported Nickel-Based Catalysts.

Lignocellulosic biomass such as canola straw is produced as low-value residue from the canola processing industry. Its high cellulose and hemicellulose content makes it a suitable candidate for the production of hydrogen via supercritical water gasification. However, supercritical water gasification of lignocellulosic biomass such as canola straw suffers from low hydrogen yield, hydrogen selectivity, and conversion efficiencies. Cost-effective and sustainable catalysts with high catalytic activity for supercritical water gasification are increasingly becoming a focal point of interest. In this research study, novel wet-impregnated nickel-based catalysts supported on carbon-negative hydrochar obtained from hydrothermal liquefaction (HTL-HC) and hydrothermal carbonization (HTC-HC) of canola straw, along with other nickel-supported catalysts such as Ni/Al2O3, Ni/ZrO2, Ni/CNT, and Ni/AC, were synthesized for gasification of canola straw on previously optimized reaction conditions of 500 °C, 60 min, 10 wt%, and 23-25 MPa. The order of hydrogen yield for the six supports was (10.5 mmol/g) Ni/ZrO2 > (9.9 mmol/g) Ni/Al2O3 > (9.1 mmol/g) Ni/HTL-HC > (8.8 mmol/g) Ni/HTC-HC > (7.7 mmol/g) Ni/AC > (6.8 mmol/g) Ni/CNT, compared to 8.1 mmol/g for the non-catalytic run. The most suitable Ni/ZrO2 catalyst was further modified using promotors such as K, Zn, and Ce, and the performance of the promoted Ni/ZrO2 catalysts was evaluated. Ni-Ce/ZrO2 showed the highest hydrogen yield of 12.9 mmol/g, followed by 12.0 mmol/g for Ni-Zn/ZrO2 and 11.6 mmol/g for Ni-K/ZrO2. The most suitable Ni-Ce/ZrO2 catalysts also demonstrated high stability over their repeated use. The superior performance of the Ni-Ce/ZrO2 was due to its high nickel dispersion, resilience to sintering, high thermal stability, and oxygen storage capabilities to minimize coke deposition.

Impact of Sr Addition on Zirconia-Alumina-Supported Ni Catalyst for COx-Free CH4 Production via CO2 Methanation.

Zirconia-alumina-supported Ni (5Ni/10ZrO2+Al2O3) and Sr-promoted 5Ni/10ZrO2+Al2O3 are prepared, tested for carbon dioxide (CO2) methanation at 400 °C, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, surface area and porosity, infrared spectroscopy, and temperature-programmed reduction/desorption techniques. The CO2 methanation is found to depend on the dispersion of Nickel (Ni) sites as well as the extent of stabilization of CO2-interacted species. The Ni active sites are mainly derived from the reduction of 'moderately interacted NiO species'. The dispersion of Ni over 1 wt % Sr-promoted 5Ni/10ZrO2+Al2O3 is 1.38 times that of the unpromoted catalyst, and it attains 72.5% CO2 conversion (against 65% over the unpromoted catalyst). However, increasing strontium (Sr) loading to 2 wt % does not affect the Ni dispersion much, but the concentration of strong basic sites is increased, which achieves 80.6% CO2 conversion. The 5Ni4Sr/10ZrO2+Al2O3 catalyst has the highest density of strong basic sites and the highest concentration of active sites with maximum Ni dispersion. This catalyst displays exceptional performance and achieves approximately 80% CO2 conversion and 70% methane (CH4) yield for up to 25 h on steam. The unique acidic-basic profiles composed of strong basic and moderate acid sites facilitate the sequential hydrogenation of formate species in the COx-free CH4 route.

Determination of Mass and Quantitative Productivity of the Process of Electrodispersion of Nickel Waste in Isopropyl Alcohol

The purpose of this study was to obtain electroerosive dispersed nickel by processing nickel waste by electrodispersing in isopropyl alcohol, as well as to study the performance of this process and the particle size of the obtained dispersed nickel.Methods. Nickel waste in the form of plates was processed into powder by electrodispersion at an experimental electroerosive dispersion plant (RF Patent No. 2449859) in an isopropyl alcohol medium. The study of the average particle size of the obtained electroerosive dispersed nickel was carried out using a laser particle size analyzer "Analysette 22 NanoTec".Results. For the first time, spherical nickel powders in the medium of isopropyl alcohol were obtained from industrial waste by the method of electroerosive dispersion. The parameters of the electroerosive dispersion unit necessary for the dispersion of nickel waste have been determined. A directly proportional dependence of the mass productivity of the process of electroerosion research of nickel waste dispersion on the voltage at the electrodes in isopropyl alcohol in the range of 120-220 V. has been experimentally established. The optimum for dispersing nickel waste in isopropyl alcohol is the voltage at the electrodes in the range of 200-220 V. It is established that the smallest particle size is nickel powder obtained at a voltage of 220 V at the electrodes, while the mass productivity at this value of the voltage at the electrodes is the maximum.Conclusion. Based on the presented experimental studies of the mass and quantitative productivity of the process of electroerosive dispersion of nickel waste in isopropyl alcohol, a high efficiency of the use of electrodispersion technology for obtaining dispersed nickel powder, which is not inferior to industrially used powders in terms of average particle size, has been established. It has been experimentally established that the smallest particle size has a nickel powder obtained at a voltage of 220 V on the electrodes, while the mass productivity at this value of the voltage on the electrodes is maximum.

Performance Study of Ni/Si-MCM-41 Catalysts, Synthesized with Different Silica Sources, and their Application on Methane Dry Reform to Produce Green Hydrogen

The present work carried out an extensive and deepened study regarding the physicochemical characteristics of two Si-MCM-41-type supports, synthesized employing two distinct silica precursors, tetraethyl orthosilicate (TEOS) and rice husk ash (RHS), with the dispersion of nickel on the surface of the catalytic support. The direct influence of the active phase dispersion was analyzed, making a relationship with the formation of coke and with its performance on methane dry reform (DRM). The catalysts were prepared with 5, 10, and 20% (m/m) of Ni by wet impregnation method (with excess solvent), calcined at 800 ºC for 6 h, and characterized by the techniques of scanning electron microscopy and energy dispersive spectroscopy (SEM/ EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET)/Barret-JoyerHalenda (BJH), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), temperature-programmed ammonia desorption (TPD-NH3), and H2-temperature-programmed reduction (TPR). The DRM experiments were carried out at 800 °C for 24 h with a 1:1 CH4:CO2 molar ratio. Analyzes of gaseous products were performed in gas chromatography (GC) and the coke produced was estimated by temperature-programmed oxidation (TPO). The best reaction results were obtained for catalysts with 20% nickel, which were selective and stable within 24 h of reaction. Comparing the TEOS and RHS catalysts for 20% Ni, the DRM results were very similar. The catalysts on RHS support demonstrated a significant low formation of coke, which can be considered negligible in a 24 h reaction.

Non-oxidative calcination enhances the methane dry reforming performance of Ni/CeO2−x catalysts under thermal and photo-thermal conditions

Calcination in hydrogen or argon improved nickel dispersion and increased the abundance of oxygen vacancies in ceria nanorods. Visible light both accelerated the methane reforming rate and improved H2 selectivity by retarding the RWGS reaction.

A high-loading catalyst of highly dispersed nickel species on acid-treated mesoporous clay layers for efficient CO and CO2 methanation

The catalyst, consisting of nickel-amino acid framework nanocrystals on acid modified clay layers, exhibited excellent activity and stability in CO and CO2 methanations due to its high content of dispersed Ni species.

Photothermally driven decoupling of gas evolution at the solid-liquid interface for boosted photocatalytic hydrogen production.

The slow mass transfer, especially the gas evolution process at the solid-liquid interface in photocatalytic water splitting, restricts the overall efficiency of the hydrogen evolution reaction. Here, we report a novel gas-solid photocatalytic reaction system by decoupling hydrogen generation from a traditional solid-liquid interface. The success relies on annealing commercial melamine sponge (AMS) for effective photothermal conversion that leads to rapid water evaporation. The vapor flows towards the photocatalyst covering the surface of the AMS and is split by the catalyst therein. This liquid-gas/gas-solid coupling system avoids the formation of photocatalytic bubbles at the solid-liquid interface, leading to significantly improved mass transfer and conversion. Utilizing CdS nanorods anchored by highly dispersed nickel atoms/clusters as a model photocatalyst, the highest hydrogen evolution rate from water splitting reaches 686.39 μmol h-1, which is 5.31 times that of the traditional solid-liquid-gas triphase system. The solar-to-hydrogen (STH) efficiency can be up to 2.06%. This study provides a new idea for the design and construction of efficient practical photocatalytic systems.

Understanding the preparative chemistry of atomically dispersed nickel catalysts for achieving high-efficiency H2O2 electrosynthesis.

Electrochemical hydrogen peroxide (H2O2) production via two-electron oxygen reduction reaction (2e- ORR) has received increasing attention as it enables clean, sustainable, and on-site H2O2 production. Mimicking the active site structure of H2O2 production enzymes, such as nickel superoxide dismutase, is the most intuitive way to design efficient 2e- ORR electrocatalysts. However, Ni-based catalysts have thus far shown relatively low 2e- ORR activity. In this work, we present the design of high-performing, atomically dispersed Ni-based catalysts (Ni ADCs) for H2O2 production through understanding the formation chemistry of the Ni-based active sites. The use of a precoordinated precursor and pyrolysis within a confined nanospace were found to be essential for generating active Ni-N x sites in high density and increasing carbon yields, respectively. A series of model catalysts prepared from coordinating solvents having different vapor pressures gave rise to Ni ADCs with controlled ratios of Ni-N x sites and Ni nanoparticles, which revealed that the Ni-N x sites have greater 2e- ORR activity. Another set of Ni ADCs identified the important role of the degree of distortion from the square planar structure in H2O2 electrosynthesis activity. The optimized catalyst exhibited a record H2O2 electrosynthesis mass activity with excellent H2O2 selectivity.

Investigation of interactions of nickel with pyrolytic products in pyrolysis of poplar with nickel acetate via furnace or microwave heating

Metal/biochar is an important catalyst with feature of easy recovering of metal via combustion of biochar carrier. During preparation of metal/biochar, interaction of metal with biochar affects evolution of pyrolytic products and dispersion of metal. Heating mode could influence interaction of metal with pyrolytic products. This was investigated by pyrolysis of sawdust loaded with nickel acetate at 400 or 600 °C with furnace and microwave heating, respectively. The results showed that cracking of biochar and volatiles was effectively promoted with Ni, generating more gases while reducing aliphatic organics and heavy phenolics in bio-oil. The enhanced cracking facilitated aromatization in microwave heating, forming biochar of higher thermostability and gases with more hydrogen. However, the furnace heating at 600 °C formed Ni/biochar of more developed pores than from microwave heating (409.1 versus 385.0 m2g−1). Microwave heating could induce merging of micropores on biochar, resulting in migration and aggregation of Ni. This led to lower capability for chemical adsorption of hydrogen and dispersion of nickel, further leading to inferior activity of Ni/biochar from microwave heating for hydrogenation of vanillin or furfural. The in-situ IR characterization of the pyrolysis showed the furnace heating reserved more oxygen-containing organics and aliphatic structures, promoting dispersion of nickel.

Production of nickel and cobalt metal powders under autoclave conditions

This paper presents the results of studies on the reduction of dispersed cobalt and nickel metal powders from their salts in ammonia-alkaline aqueous solutions under hydrothermal autoclave conditions. A unified and environmentally friendly method for producing these powders has been developed. Hydrazine hydrate, with a 25–50 % excess of the stoichiometric ratio, was used as a reducing agent. This choice allows for obtaining metal phases that are chemically uncontaminated by decomposition products. The experiments determined the conditions for the quantitative reduction of cobalt (II) and nickel (II) ions from ammonia-alkaline aqueous solutions. The synthesis temperature for the dispersed phases ranged from 110 to 155 °C. It has been demonstrated that under the conditions used, the process is completed quantitatively within 60 min. Metal concentrations in the solutions were determined using atomic absorption spectroscopy. The results of the X-ray phase analysis confirm that cobalt forms in the HCP lattice, while nickel forms in the FCC lattice. No other phases, including X-ray amorphous phases, were observed. It was found that with an increase in the hydrothermal synthesis temperature from 110 to 155 °C, the specific surface area of cobalt increased by more than 1.5 times, and that of nickel black powders increased by approximately 2 times. Scanning electron microscopy revealed that cobalt is formed in the shape of lamellar particles with a lateral size of about 500 nm and a thickness of 50 nm, which aggregate into fractal structures. Nickel is represented by spherical particles arranged in chain-like structures. Using X-ray photoelectron spectroscopy, it was determined that the surface of the materials is covered with oxidized forms. The surface atomic concentration of cobalt (0) was approximately 2 %, while that of nickel (0) was about 25 %.

Hydrocracking of heavy oil residues with the participation of Ni-bentonite

In the article, Ni-bentonite catalyst was synthesized by exchange method. Natural bentonite mineral and synthesized catalyst were studied by XRD, XRF, TGA/TDA, TEM, EDX-mapping (map), nitrogen adsorption-desorption at 196 °C, H2-TPD and NH3-TPD analysis methods. A new processing technology was introduced at the «Hydrocracking of heavy oil residues» (SPR-1) facility with the participation of fuel oil bentonite and Ni-bentonite catalysts. The catalytic efficiency of dispersed nickel catalyst in the hydrocracking process of fuel oil under optimal conditions (430 °C, 4.0 MPa) was studied. The results of the experiments are 47% from catalyst-free hydrocracking of fuel oil; 54.7% with bentonite addition; The yield of light colored petroleum products showed a corresponding increase to 67.1% when Ni-bentonite was used. Keywords: fuel oil; hydrocracking; bentonite; gasoline fraction; diesel fraction.

Balanced anchoring sites and volatile matter in biochar render Ni/biochar with higher metal dispersion and superior activity in hydrogenation of vanillin

Metal/carbon catalysts could be prepared via simple calcination of biochar impregnated with salt of metal precursors. Abundance of oxygen-containing functionalities on biochar affects dispersion of nickel via influencing availability of anchoring sites for nickel ions in impregnation step. Biochar with high content of volatile matter tended to have more oxygen-containing species, but the volatiles released in calcination of Ni/biochar could experience secondary condensation, forming carbonaceous deposit and covering nickel sites. Therefore, the balanced distribution of oxygen-containing functionalities and volatile matter in biochar on dispersion of nickel were investigated via preparation of Ni/biochar catalysts with biochar support obtained at varied pyrolysis temperature (200, 300, 400 and 500 °C). The results indicated that the calcination of Ni/biochar-200 with biochar produced via pyrolysis at 200 °C encapsulated nickel from the deposit of secondary condensation of the volatiles, while the lack of abundance of O-containing species of biochar-400 and biochar-500 led to the growth of nickel species large crystals in their supported catalysts. In comparison, Ni/biochar-300 showed the highest dispersion of nickel and thus the highest activity for hydrogenation of vanillin to produce 2-methoxy-4-methylphenol (yield: 89.4%). The in-situ IR characterization of functionalities of biochar versus temperature and residence time indicated that the pyrolysis at 300 °C enhanced formation of –OH groups, the main anchoring sites of nickel ions. Nonetheless, abundant C = O at 400 °C and developed aromatic ring structures at 500 °C were not effective for dispersion of nickel species.

γ-Al2O3 sacrificial template method for preparing flower-like Ni–Mg–Al catalysts for dry reforming of methane

A series of NiMgAl-X catalysts are prepared by adding the γ-Al2O3 as a sacrificial template method through co-precipitation and applied to the dry reforming of methane (DRM). The catalysts were characterized by XRD, SEM, TEM, H2-TPR, CO2-TPD, Raman, TPH, and TG. The results show that the appropriate addition of γ-Al2O3 can improve the structural stability of the catalyst so that the catalyst can maintain a well-shaped flower-like lamellar structure after calcination at 700 °C, improve the nickel dispersion and surface alkalinity to a certain extent, and improve its catalytic activity while maintaining good stability. The NMA-1 catalyst exhibits the highest catalytic activity of 73.7% and 83.2% conversion of CH4 and CO2 respectively after 50 h reaction, which is increased by 4.3% and 3.0% compared to the NMA catalyst.

Ex-situ catalytic upgrading of biomass pyrolysis volatiles over thermal-decomposition products of spent lithium-ion batteries for bio-oil deoxygenation and hydrogen-rich syngas production

Spent lithium-ion batteries rich in transition metals are highly potential to catalyze the biomass pyrolysis process. This research provided insight into the performance and mechanism of ex-situ catalytic upgrading of biomass pyrolysis volatiles over the thermally pyrolyzed spent Ni–Co–Mn ternary batteries (PyNCM) for the first time. The results showed that the PyNCM exhibited high catalytic activities for the secondary decompositions of pyrolysis volatiles, resulting in 12.6% reduction on bio-oil yield and 57.5% promotion on syngas productivity. The magnetic Ni and Co compounds in PyNCM were primarily responsible for the enhanced volatile deoxygenations, and the maximum H2 yield reached 2.66 mmol g−1 biomass. Two levels of synergistic catalysis were identified: (1) the synergy among the transition metals established multiple active centers to promote the H2 selectivity; (2) the non-magnetic graphite and lithium could probably improve the dispersion and surface oxygen vacancies of nickel and cobalt to further enhance the catalytic activity.

Looking for an Optimal Composition of Nickel-Based Catalysts for CO2 Methanation

A detailed critical analysis of the scientific literature data concerning catalysts for CO2 methanation based on nickel supported over oxides was performed. According to the obtained information, it seems that an ionic support is necessary to allow a good nickel dispersion to produce very small nickel metal particles. Such small metal particles result in being very active toward methanation, limiting the production of carbonaceous materials. The use of support and/or surface additives gives rise to medium surface basicity, allowing medium-strong adsorption of CO2, and it is also advisable to increase the reaction rate. A medium nickel loading would allow the free support geometric surface to be covered densely by small nickel metal particles without the production of larger Ni crystals. It is also advisable to work at temperatures where Ni(CO)4 formation is not possible (e.g., >573 K). The promising properties of systems based on doped Ni/Al2O3, doped with basic and re-active oxides such as MnOx or/and CeO2, and those based on Ni/CeO2 were underlined.

Achieving super dispersed metallic nickel nanoparticles over MCM-41 for highly active and stable hydrogenation of olefins and aromatics

Hydrogenation of olefins and aromatics is of significance for fuel processing and hydrogen storage, and developing nickel (Ni) catalyst highly active at low reaction temperature is the key to low the process cost. Herein we developed an ammonium citrate assisted impregnation method to fabricate loaded Ni catalyst (NiM-2) for hydrogenation. The Ni2+ species are anchored on the support MCM-41 strongly and evenly in form of Ni-citrate complex via the H-bonding between Si-OH group of MCM-41 and –COO- of citrate. During reduction, the carbon layerstemporarily formed by carbonization of citrate species inhibit the transfer and sintering of Ni species, and finally induces ultra-small metallic Ni nanoparticles after carbon layers slow decomposition by Ni species. Low coordination numbers and strong electron interaction between small metallic Ni nanoparticles and MCM-41 support upshift the d-band center of metallic Ni atoms. In hydrogenation, the small particle size and easier reduction for oxidized Ni species provide abundant active sites for reaction, and the upshifted d-band center induces strongly adsorption and activation of C = C bonds, which is confirmed for the first time in our work. As a result, the catalyst exhibits superior activity compared with reported and commercial Ni-based catalysts for hydrogenation of olefins and aromatics. Specifically, the catalyst with higher Ni loading (18%) exhibits good activity under room temperature and 0.1 MPa for hydrogenation of dicyclopentadiene and are comparable to Pd catalysts, making it as one of the best non-precious metal catalysts for hydrogenation reaction. And also, NiM-2 shows extremely high stability.

Enhancing Catalytic Performance with Sol‐Gel Hydrotalcite‐Derived Nickel Oxide Catalysts for Dry Reforming of Methane: An Examination on Reactivity and Coke Formation

AbstractHydrotalcite‐based materials are preferred as catalysts due to their versatility and easiness of their synthesis. This work studies supported nickel catalysts made from hydrotalcites through sol‐gel synthesis, Ni‐EDTA impregnation, and coprecipitation. The synthetized hydrotalcites present nanocapsular morphology and dispersed nickel nano‐oxide particles after calcination at 500 °C. The catalysts were evaluated at 600 °C and 800 °C for 8 hours and demonstrated high conversions and varying yields, with sol‐gel oxide catalysts (SgOxMix) showing the best performance with the highest reactivity and controlled coke formation at 800 °C after 14 hours of testing. The mixed oxide morphology promotes electronic effects and inhibits carbon encapsulation of metallic particles. Principal component analysis was performed to explain fluctuations in the reaction pathway.