Nickel Loading Research Articles

Steam reforming of acetic acid over Ni/Al2O3 catalyst: Correlation of calcination temperature with the interaction of nickel and alumina

This study investigated the interaction of nickel species with alumina versus calcination temperature and nickel loading. A total of 22 Ni/Al2O3 catalysts, calcined at the temperature from 500 to 1000 °C at a 50 °C increment, were employed for the study. High calcination temperature led to the formation of nickel–alumina spinel via the solid phase reaction, which shifted the reduction temperature to higher ranges. The catalyst, however, still achieved good activity after full reduction of the nickel–alumina spinel. Nevertheless, the high calcination temperature led to the collapse of the small pores and the formation of the big one, resulting in the significant decrease of specific surface area. At higher nickel loadings, more nickel species weakly interacted with alumina formed as the reactive center of alumina was saturated. With the increase of nickel loading, the catalytic activities were not varied much but the catalytic stability and the resistivity towards coking enhanced. The coke produced over the catalyst at low nickel loading tended to be amorphous, while the coke produced at the high nickel loading was more fibrous. Furthermore, the coke produced at the low loading contained more small aromatic rings and more oxygen-containing functional groups. The higher nickel loading possibly promoted the catalytic cracking reactions to form more catalytic coke while the low nickel loading probably favored the polymerization reactions to form the polymeric coke. In addition, the calcination at the higher temperature could enhance the stability of the catalysts, which might be related to the enlarged pore sizes.

Thermal and kinetic behaviors of corn stover and polyethylene in catalytic co-pyrolysis

Thermal decomposition characteristics and kinetics of high-density polyethylene (HDPE), corn stover (CS), and their blended mixture (1:1 w/w ratio) during non-catalytic and catalytic co-pyrolysis were studied via thermogravimetric analysis (TGA). The results indicated synergetic interactions between the biomass and the plastics during co-pyrolysis as measured by weight loss (ΔW); this effect was attributed to radical interactions during co-pyrolysis. The pyrolysis catalysts with higher nickel loadings (5%, 10%, and 15%) appreciably diminished the solid residue. Kinetic studies indicated that the pyrolysis was a first-order reaction based on the fitted thermogravimetric data. The activation energy (E) and pre-exponential factor (A) ranged between 26.13 kJ/mol to 392.67 kJ/mol and between 156.24 min-1 to 9.19 x 1023 min-1, respectively. There was a kinetic compensation effect (KCE) observed among the two kinetic parameters. The activation energy (E) decreased for each pyrolysis stage with the presence of a catalyst. The results indicated that catalytic co-pyrolysis could provide great potential for reducing the pyrolysis energy input.

Comparative study of hydrogen storage on metal doped mesoporous materials

The hydrogen adsorption capacity of mesoporous materials MCM-41 modified with Co, Fe, Ti, Mg and Ni at 77 K and 10 bar was investigated. Various techniques including XRD, N2 adsorption and DRUV–vis were employed for the materials characterization. The results showed that a low nickel loading on MCM-41 support promoted the presence of hydrogen-favorable sites, increasing the hydrogen storage capacity.

Fluidizable Ni/Ce-meso-Al2O3 for gasification of glucose: Effect of catalyst reduction on hydrogen selectivity

A new template-free technique is applied to develop fluidizable Ce-Al2O3 support and impregnated with nickel. The Ni(x)/Ce-Al2O3 catalysts are evaluated in a fluidized CREC Riser Simulator using glucose as biomass surrogate. XRD shows that nickel is well-dispersed on Ce-Al2O3. The acidity of the catalysts decreased from 0.317 to 0.202mmol NH3/g-sample as the nickel loading was increased. In catalyst evaluation, it is found that the reduced catalysts favor bond cleavage, promotes water gas shift and steam reforming reactions to give hydrogen/syngas as more selective products. Ni(20)/Ce-Al2O3 exhibited lowest extent of coking and produced hydrogen rich syngas with H2/CO≈1.75:1.

Effect of nickel loading on the performance of nano- and micro-sized ZSM-5 catalysts for methanol to hydrocarbon conversion

Methanol to hydrocarbon process is becoming increasingly important as methanol can be manufactured from flare gas, biomass, shale gas and coal. In this work, micro- and nano- sized ZSM-5 zeolites have been modified with low level nickel loading and tested for methanol to hydrocarbon process. It is shown that nano-sized ZSM-5 catalyst doped with nickel with or without H2 reduction has higher yield of hydrocarbon than the micro-sized ZSM-5 catalyst. Pretreatment of the NiO/ZSM-5 catalyst with H2 reduction does not decrease aromatics yield in the hydrocarbon products, but in contrast increases the yield of C1-C4 gaseous products, which may be due to the lower loading (1.0% in wt.) of nickel metal substitution. The introduction of NiO to ZSM-5 catalyst increases acid amount and also acid strength, which may be due to the nickel entering the framework, thus changing the coordination environment of Si and Al. The structure of nano-sized ZSM-5 catalyst is more affected by the loading of nickel, such as more AlO5 units. In terms of catalytic performance, nano-sized ZSM-5 catalyst has high yield for hydrocarbon production, less gaseous yield, and less aromatics, which is probably due to the shorter distance for the diffusion and contact time of the dehydrated products over the acid sites.

Metallic nickel supported on mesoporous silica as catalyst for hydrodeoxygenation: effect of pore size and structure

Catalytic hydrodeoxygenation (HDO) of anisole, a methoxy-rich lignin-derived bio-oil model compound, was carried out over a series of Ni-containing (5, 10, 20, and 30 wt%) catalysts with commercial silica and ordered mesoporous silica SBA-15 as support. Both supports and catalysts were characterized by N2 adsorption–desorption isotherms, X-ray diffraction, CO chemisorption, and transmission electron microscopy (TEM). Catalytic reaction was performed at 250 °C and 10 bar H2 pressure. Depending on the catalyst support used and the content of active metal, the catalytic activity and product distribution changed drastically. Increase of the nickel loading resulted in increased anisole conversion and C6 hydrocarbon (benzene and cyclohexane) yield. However, loading more Ni than 20 wt% resulted in a decrease of both conversion and C6 yield due to agglomeration of Ni particles. In addition, Ni/SBA-15 samples exhibited much stronger catalytic activity and selectivity toward C6 hydrocarbon products compared with Ni/silica catalysts. The differences in catalytic activity among these catalysts can be attributed to the effect of the pore size and pore structure of mesoporous SBA-15. SBA-15 can accommodate more Ni species inside channels than conventional silica due to its high pore volume with uniform pore structure, leading to high HDO catalytic activity.

Ordered Mesoporous NiCeAl Containing Catalysts for Hydrogenolysis of Sorbitol to Glycols

Cellulose-derived sorbitol is emerging as a feasible and renewable feedstock for the production of value-added chemicals. Highly active and stable catalyst is essential for sorbitol hydrogenolysis. Ordered mesoporous M–xNiyCeAl catalysts with different loadings of nickel and cerium species were successfully synthesized via one-pot evaporation-induced self-assembly strategy (EISA) and their catalytic performance were tested in the hydrogenolysis of sorbitol. The physical chemical properties for the catalysts were characterized by XRD, N2 physisorption, H2-TPR, H2 impulse chemisorption, ICP and TEM techniques. The results showed that the ordered mesopores with uniform pore sizes can be obtained and the Ni nanoparticles around 6 nm in size were homogeneously dispersed in the mesopore channels. A little amount of cerium species introduced would be beneficial to their textural properties resulting in higher Ni dispersion, metal area and smaller size of Ni nanoparticles. The M–10Ni2CeAl catalyst with Ni and Ce loading of 10.9 and 6.3 wt % shows better catalytic performance than other catalysts, and the yield of 1,2-PG and EG can reach 56.9% at 493 K and 6 MPa pressure for 8 h after repeating reactions for 12 times without obvious deterioration of physical and chemical properties. Ordered mesoporous M–NiCeAl catalysts are active and stable in sorbitol hydrogenolysis.

Kinetics of Steam Gasification of Glucose as a Biomass Surrogate over Ni/Ce–Mesoporous Al2O3 in a Fluidized Bed Reactor

This study reports the kinetics of steam gasification of glucose as a biomass surrogate over a new Ni(x)/Ce-doped Al2O3 (x = 5, 10, 15, and 20 wt %) catalyst in a fluidized bed reactor. The presence of ceria plus successive nickel impregnation helped in conserving the catalyst’s high surface area (i.e., 102 m2/g at 20 wt % nickel loading). Incorporation of ceria dopant suppressed coke formation during steam gasification of 15 wt % glucose in the fluidized bed reactor at 650 °C and 1 atm in the order Ni(20) < Ni(15) < Ni(10) < Ni(5)/Ce-doped Al2O3. The detailed kinetic model comprises reactant adsorption, surface reaction, and product desorption steps, involving the water gas shift reaction (WGS), steam reforming of methane (SRM), and reverse dry reforming of methane (RDRM). Ni(20)/Ce-doped Al2O3 with the best performance in terms of syngas production, and the least tendency for coking, was used for the kinetic studies (for T = 550–700 °C and t = 5–25 s). The results of the model simulation indicate that t...

Nanosheets of Ni/Clay as high efficient catalysts for hydrogenation of aromatics

Using montmorillonite (MMT), a natural layered clay, as the layered precursor, nanosheets of Ni/MMT are obtained via a facile method, in which the nickel components are introduced on to the surface of the exfoliated MMT nanosheets dispersed in water via deposition-precipitation with nickel nitrate and urea. Due to their unique properties originated from the two-dimensional (2D) structure, which favors mass transfer and diffusion of the aromatics and their hydrogenation products over the catalyst during reaction, the obtained nanosheets of Ni/Clay show higher efficient for hydrogenation of aromatics than Ni/SBA-15 and Ni/γ-Al2O3 catalysts. And the highest TOF for hydrogenation of tetralin over the nanosheets of Ni/Clay is obtained as nickel loading being high to 18.5%.

Steam reforming of acetic acid over Ni/Al2O3 catalysts: Correlation of nickel loading with properties and catalytic behaviors of the catalysts

In this study, steam reforming of acetic acid over the Ni/γ-Al2O3 catalysts with varied nickel contents (from 2.5 to 40 wt%) was performed, aiming to investigate the effects of nickel loading on properties and catalytic behaviors of the catalysts. The results show that the interaction of nickel species with alumina varies with varied nickel loading. At lower nickel loadings, the nickel strongly interacting with alumina are the main species, while with the saturation of the reactive sites of alumina via loading more nickel, the proportion of the nickel species weakly interacting with alumina increased remarkably. Excess nickel on alumina can fill the pores, decreasing the reduction degree of nickel oxides, the specific area (from ca. 277 to 132 m2 g−1 with the increase of nickel loading to 40 wt%), the pore volume, and the pore diameters. Nickel loading also significantly affects the catalytic activity, stability of the catalyst and the resistivity towards coking. With the increase of nickel loading to 10 wt%, the activity of the catalyst reached a plateau. The further increase of nickel loading did not further increase the activity, but increased the stability and the tolerance towards the deactivation induced by coking. In addition, with higher nickel loadings, the coke formed has more large aromatic ring system.

Green synthesis of Ni supported hematite catalysts for syngas production from catalytic cracking of toluene as a model compound of biomass tar

In this work, natural limonite (NL) was selected as the precursor of hematite (H) to prepare the Ni-based catalysts (Nix/H) for catalytic cracking of toluene. The influences of nickel loading and reaction temperature on catalytic cracking of toluene as well as the lifetime of catalyst were evaluated and the gas products were determined. The catalysts before and after catalytic cracking were characterized by XRD (X-ray diffraction), H2-TPR (H2 temperature-programmed reduction), TEM (Transmission electron microscopy), XPS (X-ray photoelectron spectroscopy). The results showed that the catalytic activity of Nix/H was obviously improved after the Ni addition due to the formation of Ni-Fe alloy. Toluene conversion increased at first with increasing of Ni loading from 0 to 6% and then decreased from 6 to 10%. High toluene conversion of 96% and stability were achieved as the Ni loading was 6% at the reaction temperature of 800 °C. Meanwhile, toluene was mainly decomposed into CO, H2, CH4, CO2 and hematite was transformed into magnetite due to the consumption of active lattice oxygen during the catalytic cracking reaction. However, the decrease in catalytic activity of Nix/H with the increase of reaction time should be attributed to the metal carbide type coke formation.

Nickel supported on YSZ: The effect of Ni particle size on the catalytic activity for CO2 methanation

The catalytic conversion of carbon dioxide to synthetic CH4 was studied on five Ni/YSZ samples, with the same nickel loading (10 wt%) but different Ni particle size. The catalysts, prepared by different methods, were characterized combining morphological (BET, TEM), structural (XRD, in-operando XAS), electronic (XPS, in-operando XANES) analysis and H2-TPR experiments. The results showed that catalytic activity and CH4 selectivity depended on size and morphology of Ni particles, and that type and amount of deposited carbon strongly depended on Ni0 morphology. The kinetic measurements revealed that both H2 and CO2 reactants were activated on Ni sites, and that YSZ support was not directly involved in the reaction mechanism.The most efficient catalyst was that prepared by wet impregnation with Ni(EDTA)2− complex due to the high Ni0 dispersion.This catalyst showed low amount of carbon and remarkable stability over time on stream. In-operando XAS showed that it did not undergo deactivation by Ni0 → Ni2+ oxidation using high CO2 concentration, thus it is applicable in dynamic conditions like those typical in the energy storage from renewable sources process.

Metal particles supported on SiO2-OH nanosphere: New insight into interactions with metals for cellulose conversion to ethylene glycol

The catalytic transformation of cellulose to polyols is one of the significant strategies to overcome the shortage of fossil fuels. Here we report a simple but effective preparation method for Ni-W/SiO2 catalysts by introduction of chelating agents (ammonium hydroxide and ethanediamine) coupled with organic reducing agent (ethylene glycol). The ethylene glycol (EG) yield from microcrystalline cellulose could reach up to 63.3% at 240 °C, 5.0 MPa H2 for 2.0 h over 15%Ni-20%W/SiO2-EEG catalyst. Moreover, some key parameters of process conditions including calcining temperature, reaction temperature and time, H2 pressure and the recycling use of catalysts were investigated. Both theoretical and experimental studies suggested that 15%Ni-20%W/SiO2-EEG catalyst showed the best activity and stability for cascading steps for EG formation at this reaction condition. By the detailed analysis of Ni-W/SiO2 catalysts after calcination via FT-IR, XRD, XPS, thermogravimetry (TG), TEM and element mapping, it could be concluded that on the surface of 15%Ni-20%W/SiO2-EEG catalyst, the particles showed less agglomeration and more homogeneous on the surface of SiO2. Some NixWy alloys (NiW, Ni2W4C) were also formed. Furthermore, it was found that the introduction of ethanediamine could promote the actual loading of nickel and tungsten species slightly according to the analysis of ICP-OES test.

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.

Iridium promoted Ni‐Co/Al2O3‐ZrO2 catalyst for dry reforming of methane

AbstractCO2 reforming of methane to produce synthesis gas was examined in a fixed bed reactor, using a combined nickel‐cobalt based catalyst supported on a mixed oxide (modified alumina with ZrO2) obtained by the sol‐gel method. The loading of nickel and cobalt was kept at 0.0500 g/g (1:1), while the amount of Ir varied between 0.0000 to 0.0100 g/g. The reforming reactions were performed at 700 °C. The time on stream profile for 360 min showed that all catalysts were very active and stable. The promoter doping of 0.0250 g/gCo‐0.0250 g/gNi‐X g/g Ir/(Al2O3‐ZrO2) catalysts augmented the activity regarding the CH4 and CO2 by 20 %. The catalysts were characterized by means of TGA, TPR, TPD, XRD, and SEM. The TGA and TPR results showed that the promoter depressed the carbon deposition and upgraded the reducibility of the active metals in that order. While the TPD analysis illustrated the basic sites of the catalyst are of medium strength.

Hydrotreatment of the carbohydrate-rich fraction of pyrolysis liquids using bimetallic Ni based catalyst: Catalyst activity and product property relations

The use of novel nickel based catalysts for the catalytic hydrotreatment of pyrolytic sugars, the carbohydrate-rich fraction of pine derived pyrolysis liquids, is reported. The catalysts are characterized by a high nickel loading (38 to 57wt%), promoted by Cu, Pd, and/or Mo and a SiO2 based inorganic matrix. Experiments were carried out at 180°C and 120bar initial hydrogen pressure (room temperature) in a batch reactor set-up to gain insight in catalyst activity and product properties as a function of the catalyst composition. The most promising catalyst in terms of activity, as measured by the hydrogen uptake during reaction, was the Ni-Mo/SiO2-Al2O3 catalyst whereas the performance of the monometallic Ni/SiO2-Al2O3 catalyst was the lowest. As a result, the product oil obtained by the bimetallic Ni-Mo catalyst showed the highest H/C ratio and the lowest molecular weight of all catalysts tested. A detailed catalyst characterization study revealed that addition of Mo to the Ni catalyst suppresses the agglomeration of nickel nanoparticles during the catalytic hydrotreatment reaction.

The effect of synthesis parameters on ordered mesoporous nickel alumina catalyst for CO2 methanation

A series of ordered mesoporous nickel alumina catalysts were synthesized via the evaporation induced self-assembly technique (EISA). Varying synthesis parameters such as the type of acid, nickel loading, calcination temperature as well as synthesis method influenced the catalyst morphology and its activity towards CO2 methanation. Catalyst prepared without acid formed macroporous structures with a very low surface area (47m2g−1), whereas using a mixture of hydrochloric and citric acid resulted in incomplete formation of mesoporous micelles with surface area of 173m2g−1. On the other hand, using nitric acid lead to complete formation of long cylindrical micelles with a combined surface areas up to 260m2g−1 and highly dispersed nickel clusters with a size of 3–5nm. An optimum calcination temperature of 700°C was determined yielding the highest CO2 conversion and CH4 selectivity. This catalyst displayed a stable performance and did not exhibit any sign of deactivation during a 150h test. Catalysts calcined at lower and higher temperatures had smaller surface areas as well as lower catalytic activity.

Fate of toxic metals during estuarine mixing of fresh water with saline water.

Metals are among the most common environmental pollutants, and their presence in high concentration in waters and biota have devastating effects on flora, fauna, and human health. Flocculation process of metals during estuarine mixing can reduce the environmental hazards of metals and also can provide micronutrients to the aquatic system. The present investigation provides a thorough study of eliminating colloidal elements of copper, manganese, nickel, lead, and zinc during estuarine mixing of Shalmanrood River water with Caspian Sea water in Iran. The processes of flocculation were carried out in six different salinity regimes (0.45-2.4ppt). The obtained result is indicative of non-conservative behavior of the studied metals. Higher flocculation resulted in a lower salinity regime. The obtained results indicated that most of the metals were eliminated during the initial mixing of fresh water with sea water at 0.45-0.9ppt salinity interval. The trend of flocculation rates of elements is as follows: Zn (59.3%) > Pb (47.6%) > Mn (37.5%) > Cu (29.2%) > Ni (27%).The annual average load of copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) from Shalmanrood River to Caspian Sea decreases as a result of flocculation process from 9.9, 7.7, 8.9, 5.1, and 23.2tons per year to 7, 4.8, 6.5, 2.7, and 9.4tons per year, respectively. According to the cluster analysis, parameters such as temperature, pH, and Eh do not have any impact on flocculation of elements expect for Pb. The only parameter that influences the flocculation of Mn is the salinity. Metal speciation studies that are carried out by Eh-pH software show that the studied metals are present as oxides (Zn, Cu, and Ni) and hydroxides (Mn and Pb).

Preparation of high catalytic activity biochar from biomass waste for tar conversion

High catalytic activity biochar from biomass waste by co-processing of H2O/CO2 activation and nickel loading for the conversion of tar model compound (toluene) were prepared. Raw char was produced by pyrolyzing pine wood sawdust at 800°C for 1h, then activated by CO2 or H2O (15vol.% in N2) at 800–900°C for 20–80min. The nickel loading amount was 2mmol/g-char (11.74wt.%). The catalytic cracking of toluene was carried out in a lab-scale fixed bed reactor at 800°C with a residence time of 0.13s. The results showed that activation significantly improved the average toluene conversion from 40.1% by raw char to 93.2% by activated char (H80). High porosity and hierarchical pore structure, more defects in graphene-like carbon structure and oxygen containing groups on the surface (CO) contributed to the higher catalytic activity of activated chars. The nickel loading increased the toluene conversion of raw char (Ni-char) and activated char (Ni-C900) from 40.1 to 80.8% and from 77.7 to 94.9%, respectively, due to the additional supply of active sites. The toluene conversion ratio of Ni-C900 was larger than that of Ni-char due to a more uniform dispersion of nickel on the activated char support. Thus, the raw biochar should be initially activated before used as catalyst or catalyst support to obtain a higher and more stable catalytic activity for tar conversion.

Rapid Quantification of Film Thickness and Metal Loading for Electrocatalytic Metal Oxide Films

The thicknesses and metal loadings of amorphous nickel, iron, and iridium oxide films widely used for solar fuel electrocatalysis were determined by cross-sectional scanning electron microscopy (SEM) and X-ray fluorescence (XRF) spectroscopy measurements. The thicknesses for a series of films, which were systematically varied from 10 to 400 nm using photodeposition techniques, were accurately measured by cross-sectional SEM using a protocol that successfully resolves the relevant catalyst layers. XRF measurements recorded on each of the films provided a strong linear correlation (R2 > 0.97) with the thicknesses determined by cross-sectional SEM. The electrochemical surface areas (ECSAs) determined by double-layer capacitance measurements, a technique widely used in the electrocatalysis community, showed a linear relationship for iridium oxide film thicknesses but not with those consisting of nickel and iron. These results highlight the limitations of using ECSA to determine catalyst film thicknesses and m...