High Ni Loading Research Articles

Ethylene Oligomerization over Nickel Supported Silica-Alumina Catalysts with High Selectivity for C10+ Products

The nickel (II) loading silica-alumina under various treatments in terms of aging temperature, Si/Al ratio and activation temperature were investigated by XRD, N2 adsorption-desorption, TEM, UV-Vis, NH3-TPD and XRF and then applied to catalyze the ethylene oligomerization. High aging temperature, low Si/Al ratio and high activation temperature were beneficial to high selectivity for C10+ products because of a reasonable match between Ni active sites and acid sites, high Ni loading content and less octahedral coordination Ni2+ species, respectively. Ni loading content was more important than the number of acid sites for high yield of C10+ products, and less octahedral coordination Ni2+ species favored less by-products produced at high reaction temperature. In addition, other experimental conditions, such as reaction temperature, weight hourly space velocity (WHSV) and nickel precursor were discussed in the paper.

A new systematic synthesis of ultimate nickel nanocatalysts for compact hydrogen generation

A new systematic synthesis: an AIO reactor can materialize ultimate Ni nanocatalysts containing active Ni nanoparticles (4.5 nm) with high Ni loading (25 wt%), using a programmed sequence based on simple melt-infiltration and thermal treatment.

Low Temperature Methanation of CO2 on High Ni Content Ni-Ce-ZrOδ Catalysts Prepared via One-Pot Hydrothermal Synthesis

Ni-Ce-Zr-Oδ catalysts were prepared via one-pot hydrothermal synthesis. It was found that Ni can be partially incorporated into the Ce-Zr lattice, increasing surface oxygen species. The catalysts possess high surface areas even at high Ni loadings. The catalyst with Ni content of 71.5 wt.% is able to activate CO2 methanation even at a low temperature (200 °C). Its CO2 conversion and methane selectivity were reported at 80% and 100%, respectively. The catalyst was stable for 48 h during the course of CO2 methanation at 300 °C. Catalysts with the addition of medium basic sites were found to have better catalytic activity for CO2 methanation.

Highly Efficient Electroreduction of CO2 on Nickel Single-Atom Catalysts: Atom Trapping and Nitrogen Anchoring.

Construction of single atom catalysts (SACs) with high activity toward electroreduction of CO2 still remains a great challenge. A very simple and truly cost-effective synthetic strategy is proposed to prepare SACs via a impregnation-pyrolysis method, through one-step pyrolysis of graphene oxide aerogel. Compared with other traditional methods, this process is fast and free of repeated acid etching, and thus it has great potential for facile operation and large-scale manufacturing. Both X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy images confirm the presence of isolated nickel atoms, with a high Ni loading of ≈2.6 wt%. The obtained 3D porous Ni- and N-codoped graphene aerogel exhibits excellent activity toward electroreduction of CO2 to CO, in particular exhibiting a remarkable CO Faradaic efficiency of 90.2%. Density functional theory calculations reveal that free energies for the formation of intermediate *COOH on coordinatively unsaturated NiN sites are significantly lower than that on NiN4 site, suggesting the outstanding activities of CO2 electroreduction originate from coordinatively unsaturated NiN sites in catalysts.

Cooling Induced Surface Reconstruction during Synthesis of High‐Ni Layered Oxides

AbstractTransition metal layered oxides have been the dominant cathodes in lithium‐ion batteries, and among them, high‐Ni ones (LiNixMnyCozO2; x ≥ 0.7) with greatly boosted capacity and reduced cost are of particular interest for large‐scale applications. The high Ni loading, on the other hand, raises the critical issues of surface instability and poor rate performance. The rational design of synthesis leading to layered LiNi0.7Mn0.15Co0.15O2 with greatly enhanced rate capability is demonstrated, by implementing a quenching process alternative to the general slow cooling. In situ synchrotron X‐ray diffraction, coupled with surface analysis, is applied to studies of the synthesis process, revealing cooling‐induced surface reconstruction involving Li2CO3 accumulation, formation of a Li‐deficient layer and Ni reduction at the particle surface. The reconstruction process occurs predominantly at high temperatures (above 350 °C) and is highly cooling‐rate dependent, implying that surface reconstruction can be suppressed through synthetic control, i.e., quenching to improve the surface stability and rate performance of the synthesized materials. These findings may provide guidance to rational synthesis of high‐Ni cathode materials.

Optimization of reaction parameters for bio-oil production by catalytic pyrolysis of microalga Tetraselmis suecica: Influence of Ni-loading on the bio-oil composition

In this work, a marine microalga Tetraselmis suecica was pyrolyzed in a fixed-bed reactor in the presence of a series of zeolite (Si/Al = 30) supported Ni catalysts to increase the hydrocarbon composition of the pyrolysis oil by a two-step process - devolatilization followed by catalytic treatment. A 3 wt% Ni-loading on zeolite showed the highest hydrocarbon content of 55.38%, in which aliphatic hydrocarbons and aromatic hydrocarbons were 35.21% and 20.17%, respectively. Besides, the oxygen-containing compounds decreased from 42.88% to 9.55% while the nitrogen-containing compounds decreased from 40.68% to 35.07%. The activity of the Ni-loaded catalysts was found to increase up to 3 wt % Ni-loading and decrease at higher loadings in similar lines to catalyst acidity measurements. Besides, the catalytic activity decreased with an increase in crystallite size of Ni at higher Ni loadings. The results indicate that the Ni-loaded catalysts can deoxygenate pyrolysis oils, but it is necessary to address the removal of the nitrogenous compounds. Pyrolysis temperature and Ni-loading play an important role in the removal of oxygen and nitrogen from the bio-oil. The quality of the bio-oil can be affected by the presence of strong acid sites, nickel-loading and the pore size.

Optimal Ni loading towards efficient CH4 production from H2 and CO2 over Ni supported onto fibrous SBA-15

The transformation of SBA-15 into fibrous type SBA-15 (F-SBA-15) as well as the influence of Ni loadings (1, 3, 5, and 10 wt%) towards an efficient CH4 production from H2 and CO2 were explored. The synthesized catalysts were characterized using XRD, BET, ICP-MS, FTIR, FESEM-EDX, TEM, and in-situ FTIR adsorbed pyrrole. Increasing Ni loadings onto F-SBA-15 support promoted excellent performance towards CO2 methanation. The efficacy in CO2 methanation over Ni/F-SBA-15 increased with a sequence of 1%Ni/F-SBA-15 < 3%Ni/F-SBA-15 < 5%Ni/F-SBA-15 ≈ 10%Ni/F-SBA-15, indicating the superior performance and stability of 5%Ni/F-SBA-15. The increasing trend was due to the fibrous morphology of support which enhanced the quantity of SiONi bond, triggered better Ni dispersion, strengthen metal-support interaction, and increased the basicity. However, higher Ni loadings (10 wt%) onto F-SBA-15 slightly declined the performance and stability of CO2 methanation due to the limited spaces for substitution of Ni species with the silanol groups of F-SBA-15 upon the bulk Ni phase, poorer Ni dispersion, weaker metal-support interaction, and lower basicity. The new finding of combination between fibrous SBA-15 (F-SBA-15) with an optimum Ni loading contributed towards an outstanding performance and thus could be applied in various applications.

Is the CO2 methanation on highly loaded Ni-Al2O3 catalysts really structure-sensitive?

Highly loaded Ni-Al2O3 catalysts (14–88 wt.-% Ni) were prepared by dry impregnation, wet impregnation, deposition precipitation and coprecipitation and tested in the CO2 methanation. By means of ICP-OES, XRD, TPR, H2 chemisorption, N2 physisorption and thermogravimetry, different Ni species were identified, and their dependence on the synthesis method and the Ni loading was investigated. The catalysts prepared had Ni particle sizes of 5–91 nm and Ni surface areas of 5–51 m2 g−1. It could be shown that the turnover frequency (TOF) does not depend on metal-support interactions, the metal-support interface or the particle size. Hence, the CO2 methanation on Ni-Al2O3 catalysts is clearly a structure-insensitive reaction. There is a linear correlation between the conversion and the Ni surface area at constant modified residence time. Hence, catalysts with the highest Ni surfaces, i.e., the samples prepared by deposition precipitation and coprecipitation, reached the highest weight time yields. The prerequisites for high Ni surface areas at high Ni loadings could be elucidated: During the synthesis, Ni has to be able to completely penetrate the mesopores of the support. Furthermore, a linear correlation between the selectivity to CO and the weight percentage of the impurity Na could be revealed. The stability of the supported catalysts was highly dependent on the spatial distribution of Ni and the stability of the support: A high dispersion or the presence of unsupported Ni reduced the stability. Furthermore, the stability of the supported catalysts was smaller than the one of the coprecipitated catalysts, where the stability decreased with increasing nNi/nAl.

Production of aromatic hydrocarbons by hydro-liquefaction of high-density polyethylene (HDPE) over Ni/HZSM-5

HDPE hydro-liquefaction to produce aromatics was studied by optimizing reaction parameters. Ni loading (0–20 wt%), reaction temperature (360–420 °C), catalyst to reactant ratio (0.02-0.08) and reaction time (0–4 h) were investigated using Ni/HZSM-5 catalyst. The maximum aromatic yield (28.9%) was obtained over 15 wt% Ni/HZSM-5 at 400 ℃ for 1 h and using catalyst to reactant ratio of 0.06. GC–MS analysis showed that mono-ring aromatics were enriched, with xylene having the highest selectivity (20.4–27.3%). The effects of parameters on product distribution were further studied. Both high Ni loading, high temperature and high catalyst to reactant ratio gave rise to the formation of other C10-C12 benzene. Xylene was easily formed at the reaction temperature of 380 °C and catalyst to reactant ratio of 0.04. The primary reaction competing with aromatic hydrocarbon production was the cracking of liquid hydrocarbons to produce gas. A possible reaction pathway was also proposed to clarify the overall hydro-liquefaction of HDPE for aromatic hydrocarbons.

Ni stabilised on inorganic complex structures: superior catalysts for chemical CO2 recycling via dry reforming of methane

CO2 utilisation is becoming an appealing topic in catalysis science due to the urgent need to deal with greenhouse gases (GHG) emissions. Herein, the dry reforming of methane (DRM) represents a viable route to convert CO2 and CH4 (two of the major GHG) into syngas, a highly valuable intermediate in chemical synthesis. Nickel-based catalysts are economically viable materials for this reaction, however they show inevitable signs of deactivation. In this work stabilisation of Ni in a pyrochlore-perovskite structure is reported as a viable method to prevent fast deactivation. Substitution of Zirconium by Ni at various loadings in the lanthanum zirconate pyrochlore La2Zr2O7 is investigated in terms of reactant conversions under various reaction conditions (temperature and space velocity). XRD analysis of the calcined and reduced catalysts showed the formation of crystalline phases corresponding to the pyrochlore structure La2Zr2-xNixO7-δ and an additional La2NiZrO6 perovskite phase at high Ni loadings. Carbon formation is limited using this formulation strategy and, as a consequence, our best catalyst shows excellent activity for DRM at temperatures as low as 600 °C and displays great stability over 350 h of continuous operation. Exsolution of Ni from the oxide structure, leading to small and well dispersed Ni clusters, could explain the enhanced performance.

Hydrotreatment of 2‐Methoxyphenol over High Ni‐Loaded Sol‐Gel Catalysts: The Influence of Mo on Catalyst Activity and Reaction Pathways

AbstractMo (content ranging from 0 to 18.8 wt%) is used as an additive in Ni‐containing sol‐gel derived catalysts NiCuMo/SiO2 for the hydrotreatment of guaiacol as a model compound in biomass derived pyrolysis liquids. The catalysts had a high Ni loading, from 39 to 51 wt%, promoted by copper with an atomic ratio Cu/Ni close to 0.12. The experiments were done in autoclave at 320 °C, at a hydrogen pressure of 9 MPa. Addition of molybdenum results in an increase in activity of the catalyst, accompanied with an increase in selectivity towards the deoxygenation reactions. This is attributed to the formation of solid solutions NiMo(Cu) and 4+ and 5+ charge states of Mo on the catalyst surface. Moreover, an increased mean metal particles size is observed at higher Mo loading, due to the weakening of the interaction between the active component (Ni) and the stabilizer (SiO2) in the presence of Mo.

BASF opens new chemical catalysts production plant in China

CO2 methanation using nickel-based catalysts has attracted large interest as a promising power-to-gas route. Ni nanoparticles supported on nitrogen-doped CNTs with Ni loadings in the range from 10 wt% to 50 wt% were synthesized by impregnation, calcination and reduction and characterized by elemental analysis, X-ray powder diffraction, H2 temperature-programmed reduction, CO pulse chemisorption and transmission electron microscopy. The Ni/NCNT catalysts were highly active in CO2 methanation at atmospheric pressure, reaching over 50% CO2 conversion and over 95% CH4 selectivity at 340 °C and a GHSV of 50,000 mL g−1 h−1 under kinetically controlled conditions. The small Ni particle sizes below 10 nm despite the high Ni loading is ascribed to the efficient anchoring on the N-doped CNTs. The optimum loading of 30 wt%–40 wt% Ni was found to result in the highest Ni surface area, the highest degree of conversion and the highest selectivity to methane. A constant TOF of 0.3 s−1 was obtained indicating similar catalytic properties of the Ni nanoparticles in the range from 10 wt% to 50 wt% Ni loading. Long-term experiments showed that the Ni/NCNT catalyst with 30 wt% Ni was highly stable for 100 h time on stream.

Mixed oxides supported low-nickel formulations for the direct amination of aliphatic alcohols with ammonia

Abstract The present study focuses on the selective synthesis of primary amines from aliphatic alcohols and ammonia using alumina-ceria supported nickel formulations based on very low nickel loading (≤2 wt%) and without any additive or external H 2 supply. The effect of the catalyst preparation methods and modes of nickel impregnation were studied in detail and comprehensively characterized. The best formulation afforded 80% n -octanol conversion with 78% selectivity to n -octylamine at optimized reaction conditions, which were far better than control catalysts and benchmark Ni-alumina formulations relying on high Ni loadings. The enhanced activities of the alumina-ceria supported nickel catalysts was attributed to three combined effects: (1) a higher reducibility of surface nickel oxide species, (2) the genesis of very small and homogeneously distributed nickel nanoparticles (2–3 nm), and (3) a strong decline in the formation of nickel aluminates. Furthermore, unlike benchmark Ni catalysts, these formulations afforded a higher resistance to leaching.

Dispersed and high loading Ni catalyst stabilized in porous SiO2 matrix for substituted natural gas production

Substituted natural gas (SNG) production via methanation reaction from syngas generated through gasification of coal/biomass can increase the energy diversity and reduce the dependence of fossil oil especially for those areas where fossil oil resources are scarce. In this study, the preparation, characterization and catalytic performance of a Ni-based methanation catalyst, consisting of highly dispersed nano-Ni particles encapsulated in a mesoporous silica (mSiO2) matrix, named as Ni#mSiO2, is reported. Very small Ni particles (∼3nm) were successfully synthesized via a two-step coprecipitation method with high Ni loading up to ∼40% in the mSiO2. The Ni#mSiO2 catalyst has shown improved Ni sintering, coking and sulfur resistance compared to a commercial Ni methanation catalyst. The superior performance of Ni#mSiO2 as compared to the supported Ni catalyst is attributed to the stabilization of Ni particles by the porous SiO2 matrix. This novel Ni#mSiO2 catalyst is robust and suitable to produce SNG from syngas derived from gasification process.

Evaluation of the catalytic surface of Ni impregnated meso-microporous silica KIT-6 in CH4 dry reforming by inverse gas chromatography

Inverse gas chromatography (IGC) was employed in evaluating the catalytic surface of meso-microporous KIT-6 impregnated Ni (0.5–2.0 wt%) in methane dry reforming reaction. The free energy of adsorption did not changed significantly for the sample modified with highly dispersed Ni species (0.5 wt%). At higher Ni loadings, higher free energy of adsorption and enthalpy of adsorption of the probes were observed, together with high dispersive interaction and specific interaction of aromatics. The results indicated that during the impregnation, Ni species preferably penetrated into the microporous region to form Ni particles and became ‘unaccessible’. This feature was used to understand the dependence of activity on Ni loading for the gas phase catalytic methane reforming with carbon dioxide on Ni/KIT-6. The lower TOF at low metal loadings was attributed to Ni particles located in the micropores which result in diffusional constraint of reactants and products.

New insights into the role of Ni loading on the surface structure and the reactivity of nZVI toward tetrabromo- and tetrachlorobisphenol A

Nanoscale zero-valent iron (nZVI) and nickel/nanoscale zero-valent iron (Ni/nZVI) bimetallic particles were explored for tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA) dehalogenation under ambient condition. The characteristics of the fresh and aged nanoparticles were analyzed by SEM, BET, XRD, XPS and FTIR, and found out that bimetal nanoparticles accelerated the corrosion of Fe0 in the synthesized particles during the reaction. The results shows that the addition of Ni to nZVI particles with low Ni loading (⩽0.5wt%) significantly enhanced dehalogenation of TBBPA and TCBPA compared to the pure nZVI, while high Ni loading (>0.5wt%) did less favor. The observed pseudo first-order rate constant (kobs) of 0.5%Ni/nZVI for TBBPA and TCBPA were 3.74 (±0.29)×10−2 and 0.95 (±0.04)×10−2min−1, which were about 27 and 20 times higher than that of nZVI, respectively, probably due to the formation of highly activated hydrogen atom (H*) and galvanic cells. Ni/nZVI with lower Ni loading (<0.5wt%) resulted in partial dehalogenation of TBBPA and TCBPA, while with higher Ni loading (⩾0.5wt%) curtailed the accumulation of intermediates and completely transformed them to bisphenol A (BPA). A dramatic decrease in oxidation–reduction potential (ORP) values from about +300 to −750mV after Ni/nZVI addition indicates that Ni/nZVI is an effective material to achieve highly reducing conditions. Both ORP and pH shows a correlative tendency with TBBPA and TCBPA removal efficiency. This suggests that ORP and pH can serve as indicators for the reductant reactivity.

Ni Nanoparticles Supported on Cage-Type Mesoporous Silica for CO2 Hydrogenation with High CH4 Selectivity.

Ni nanoparticles (around 4 nm diameter) were successfully supported on cage-type mesoporous silica SBA-16 (denoted as Ni@SBA-16) via wet impregnation at pH 9, followed by the calcination-reduction process. The Ni@SBA-16 catalyst with a very high Ni loading amount (22.9 wt %) exhibited exceptionally high CH4 selectivity for CO2 hydrogenation. At a nearly identical loading amount, the Ni@SBA-16 catalysts with smaller particle size of Ni NPs surprisingly exhibited a higher catalytic activity of CO2 hydrogenation and also led to a higher selectivity on CH4 formation than the Ni@SiO2 catalysts. This enhanced activity of the Ni@SBA-16 catalyst is suggested to be an accumulative result of the advantageous structural properties of the support SBA-16 and the well confined Ni NPs within the support; both induced a favorable reaction pathway for high selectivity of CH4 in CO2 hydrogenation.

Effective adsorption and concentration of carnosine by nickel species within mesoporous silica

Carnosine (Car) abundantly exists in meat-derived wastes and has various functions with attractive application as food supplement. Therefore, it is of vital importance to recover Car from the low-value food stuff. Herein, carboxyl group functionalized mesoporous silica of SBA-15 was synthesized to facilely incorporating NiO, ZnO and CoO for Car extraction. Among these, Ni/SBA-15 has the highest adsorption capability. The correlation between the most significant parameters was optimized, and the effects of these parameters on the adsorption efficiency of Car were investigated. Due to the adequate pore size and high Ni loading, the adsorption capacity of Car approached as high as 0.839 mmol/g. The excellent adsorption characteristics of the current adsorbents toward Car were preserved in a commonly used pH window and could be hardly infected by the background salts. The pseudo-second-order rate equation effectively described the uptake kinetics. The Langmuir model exhibited a better fit to adsorption isotherm than the Freundlich model. Therefore, nickel species within functionalized SBA-15 is a kind of efficient materials for recovering histidine-containing peptides from egg-laying hens and makes it a favorable candidate as chromatographic column materials for histidine-containing dipeptides analysis.

Hydrogen production from chemical looping steam reforming of glycerol by Ni based Al-MCM-41 oxygen carriers in a fixed-bed reactor

This paper describes the synthesis of a series of Ni based Al-MCM-41 oxygen carriers with and without Ce promoter and their application in chemical looping steam reforming of glycerol. The Al-MCM-41 is derived from montmorillonite. The oxygen carriers were prepared by direct-synthesis and post-synthesis method. A variety of technologies including N2 adsorption-desorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), H2 temperature-programmed reduction (H2-TPR), and transmission electron microscopy (TEM) were conducted to characterize the fresh and used oxygen carriers. The results show the direct-synthesis oxygen carrier possesses excellent textual properties, such as high Ni loading, small particle size, large pore volume, and uniform pore size. The incorporation of Ce could effectively control particle size via strong metal support interaction, promote the homogeneous distribution of Ni, and enhance oxygen mobility capability and water gas shift reaction. And thus shorten ‘dead time’ during the fuel feed step. The CeNi/Al-MCM-41 displayed the superior activity and excellent long-term stability, which could be due to the strengthened anti-sintering and coke capability.

Carbon produced by the catalytic decomposition of methane on nickel: Carbon yields and carbon structure as a function of catalyst properties

The interplay of carbon quantity, carbon type, methane decomposition activity and catalyst deactivation by deposited carbon are all important aspects to be considered in assessing the practical use of the catalytic methane decomposition route, using nickel/titania catalysts.Increasing the nickel loading from 7% to 20% in Ni/TiO2 increased methane decomposition conversion but the activities and carbon yields per unit Ni fell as the nickel content increased. The carbon produced on high Ni-loaded samples is more graphitic in nature. Filaments of carbon are the main products and the diameter increases as the Ni particle size on the catalyst increases, which, in turn, increasing at higher Ni loadings. Studies of binary supports on the activity of nickel demonstrated that not all systems led to improved catalyst performance. But, in these systems, factors such as metal-support interaction are also important. Introduction of copper to the supported nickel system exerts an effect on the morphology of the carbon nanostructures produced but other aspects are little affected.