High Ni Loading Research Articles

Concurrently boosted oxygen reduction/evolution electrocatalysis over highly loaded CoNi/onion-like carbon hybrid nanosheets

Balancing the bicatalytic activities and stabilities between oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a critical yet challenging task for exploring advanced rechargeable Zinc–air batteries (ZABs). Herein, a hybrid nanosheet catalyst with highly dispersed and densified metallic species is developed to boost the kinetics and stabilities of both ORR and OER concurrently. Through a progressive coordination and pyrolysis approach, we directly prepared highly conductive onion-like carbon (OLC) accommodating dense ORR-active CoNC species and enveloping high-loading OER-active CoNi-synergic structures within a porous lamellar architecture. The resultant CoNi/OLC nanosheet catalyst delivers better ORR and OER activities showcasing a smaller reversible oxygen electrode index (ΔE = Ej10 − E1/2) of 0.71 V, compared to state-of-the-art Pt/C-RuO2 catalysts (0.75 V), Co/amorphous carbon polyhedrons (0.80 V), NiO nanoparticles with higher Ni loading (1.00 V), and most CoNi-based bifunctional catalysts reported so far. The rechargeable ZAB assembled with the developed catalyst achieves a remarkable peak power density of 270.3 mW cm−2 (172 % of that achieved by Pt/C + RuO2) and ultrahigh cycling stability with a negligible increase in voltage gap after 800 h (110 mV increase after 200 h for a Pt/C + RuO2-based battery), standing the top level of those ever reported.

Facile synthesis of Ni-phyllosilicate assisted by polyacrylamide at room temperature for CO2 hydrogenation to methane

To elucidate the effect of solution viscosity on the synthesis of Ni-phyllosilicate, polyacrylamide was incorporated to create a viscous aqueous medium containing of sodium metasilicate, nickel nitrate and NH4F. The enhanced viscosity promotes the dispersion of the initial formed crystal seeds and the growth of Ni-phyllosilicate, culminating in a Ni-rich NiPs-RT-6 of a high Ni content of up to 55.2 wt%. Residual polyacrylamide elimination was accomplished via calcination, concurrently enhancing metal-support interaction. The as-synthesized samples display a nanoflower morphology with nanospheres overlaid with numerous thin nanosheets. The relatively small Ni particles around 5.7 nm were obtained after reduction even at a very high Ni loading, owing to its strong metal-support interaction. NiPs-RT-6 achieves a CO2 conversion of 75.9% at 450 °C, 0.1 MPa, 60 L g−1·h−1, which closely approximates thermodynamic equilibrium. The turn over frequency for CO2 (TOFCO2) was substantial, calculated at 3.7 × 10−3 s−1, accompanied by activation energy (Ea) of 80.6 kJ·mol–1. In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) further disclosed that m-HCOO– serves as a crucial intermediate following a formate reaction pathway. With its high Ni content, finely distributed Ni particles, and strong metal-support interaction, NiPs-RT-6 demonstrates promising catalytic activity in CO2 methanation.

Construction of multi-porous Ni-based monolithic catalyst by combining wood carbon and SBA-15 for strengthening CO2 methanation

Monolithic catalysts meet the needs of practical application compared with powder catalysts. In this work, we constructed a Ni-based monolithic catalyst (Ni/SAB-15/WWC) by in situ growth of rod-like mesoporous SBA-15 in the microchannels of wood carbon. The small Ni-based nanoparticles (∼5.3 nm) were uniformly dispersed into the mesoporous channels via a post-loading method. The monolithic Ni/SAB-15/WWC catalyst with a multilevel porous structure could provide a laminar gas flow on the surface of Ni active sites, increasing the low-temperature activity and high-temperature durability of CO2 methanation. The Ni/SAB-15/WWC with low Ni loading (∼2%) displayed superior CO2 methanation catalytic performance in terms of low-temperature activity and CH4 selectivity compared with the powder Ni/SAB-15 with high Ni loading (∼15 %). The combination of wood carbon and mesoporous materials is an innovative strategy for the design monolithic catalysts with low metal loading and excellent catalytic performance.

Construction of Ni/In2O3 Integrated Nanocatalysts Based on MIL-68(In) Precursors for Efficient CO2 Hydrogenation to Methanol.

The efficient and economic conversion of CO2 and renewable H2 into methanol has received intensive attention due to growing concern for anthropogenic CO2 emissions, particularly from fossil fuel combustion. Herein, we have developed a novel method for preparing Ni/In2O3 nanocatalysts by using porous MIL-68(In) and nickel(II) acetylacetonate (Ni(acac)2) as the dual precursors of In2O3 and Ni components, respectively. Combined with in-depth characterization analysis, it was revealed that the utilization of MIL-68(In) as precursors favored the good distribution of Ni nanoparticles (∼6.2 nm) on the porous In2O3 support and inhibited the metal sintering at high temperatures. The varied catalyst fabrication parameters were explored, indicating that the designed Ni/In2O3 catalyst (Ni content of 5 wt %) exhibited better catalytic performance than the compared catalyst prepared using In(OH)3 as a precursor of In2O3. The obtained Ni/In2O3 catalyst also showed excellent durability in long-term tests (120 h). However, a high Ni loading (31 wt %) would result in the formation of the Ni-In alloy phase during the CO2 hydrogenation which favored CO formation with selectivity as high as 69%. This phenomenon is more obvious if Ni and In2O3 had a strong interaction, depending on the catalyst fabrication methods. In addition, with the aid of in situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory (DFT) calculations, the Ni/In2O3 catalyst predominantly follows the formate pathway in the CO2 hydrogenation to methanol, with HCOO* and *H3CO as the major intermediates, while the small size of Ni particles is beneficial to the formation of formate species based on DFT calculation. This study suggests that the Ni/In2O3 nanocatalyst fabricated using metal-organic frameworks as precursors can effectively promote CO2 thermal hydrogenation to methanol.

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.

Facile low-temperature supercritical carbonization method to prepare high-loading nickel single atom catalysts for efficient photodegradation of tetracycline

Environmental photocatalysis is a promising technology for treating antibiotics in wastewater. In this study, a supercritical carbonization method was developed to synthesize a single-atom photocatalyst with a high loading of Ni (above 5 wt.%) anchored on a carbon-nitrogen-silicate substrate for the efficient photodegradation of a ubiquitous environmental contaminant of tetracycline (TC). The photocatalyst was prepared from an easily obtained metal-biopolymer-inorganic supramolecular hydrogel, followed by supercritical drying and carbonization treatment. The low-temperature (300°C) supercritical ethanol treatment prevents the excessive structural degradation of hydrogel and greatly reduces the metal clustering and aggregation, which contributed to the high Ni loading. Atomic characterizations confirmed that Ni was present at isolated sites and stabilized by Ni-N and Ni-O bonds in a Ni-(N/O)6C/SiC configuration. A 5% Ni-C-Si catalyst, which performed the best among the studied catalysts, exhibited a wide visible light response with a narrow bandgap of 1.45 eV that could efficiently and repeatedly catalyze the oxidation of TC with a conversion rate of almost 100% within 40 min. The reactive species trapping experiments and electron spin resonance (ESR) tests demonstrated that the h+, and ·O2− were mainly responsible for TC degradation. The TC degradation mechanism and possible reaction pathways were provided also. Overall, this study proposed a novel strategy to synthesize a high metal loading single-atom photocatalyst that can efficiently remove TC with high concentrations, and this strategy might be extended for synthesis of other carbon-based single-atom catalysts with valuable properties.

Ultra-Highly Active Ni-Doped MOF-5 Heterogeneous Catalysts for Ethylene Dimerization.

Here, an ultra-highly active Ni-MOF-5 catalyst with high Ni loading for ethylene dimerization is reported. The Ni-MOF-5 catalysts are synthesized by a facile one-pot co-precipitation method at room temperature, where Ni2+ replaces Zn2+ in MOF-5. Unlike Zn2+ with tetrahedral coordination in MOF-5, Ni2+ is coordinated with extra solvent molecules except for four-oxygen from the framework. After removing coordinated solvent molecules, Ni-MOF-5 achieves an ethylene turnover frequency of 352000h-1 , corresponding to 9040g of product per gram of catalyst per hour, at 35°C and 50bar, far exceeding the activities of all reported heterogeneous catalysts. The high Ni loading and full exposure structure account for the excellent catalytic performance. Isotope labeling experiments reveal that the catalytic process follows the Cossee-Arlman mechanism, rationalizing the high activity and selectivity of the catalyst. These results demonstrate that Ni-MOF-5 catalysts are very promising for industrial catalytic ethylene dimerization.

Investigating the Effect of Ni Loading on the Performance of Yttria-Stabilised Zirconia Supported Ni Catalyst during CO2 Methanation

CO2 methanation was studied on Ni-based yttria-stabilised zirconia (Ni/YSZ) catalysts. The catalysts were prepared by the wet impregnation method, where the amount of Ni content was varied from 5% to 75%. Thereafter, the prepared catalysts were analysed by BET, XRD, SEM and H2-TPR. BET results showed an initial increase in the surface area with an increase in Ni loading, then a decrease after 30% Ni loading. The XRD results revealed that the Ni crystallite size increased as the Ni loading increased, while the H2-TPR showed a shift in reduction peak temperature to a higher temperature, indicating that the reducibility of the catalysts decreased as the Ni loading increased. The activity of the synthesised catalysts for CO2 methanation was studied by passing a mixture of H2, CO2 and N2 with a total flow of 135 mL min−1 and GHSV of 40,500 mL h−1 g−1 through a continuous flow quartz tube fixed-bed reactor (I.D. = 5.5 mm, wall thickness = 2 mm) containing 200 mg of the catalyst at a temperature range of 473 to 703 K under atmospheric pressure and a H2:CO2 ratio of 4. The tested Ni/YSZ catalysts showed an improvement in activity as the reaction temperature increased from 473 K to around 613 to 653 K, depending on the Ni loading. Beyond the optimum temperature, the catalyst’s activity started to decline, irrespective of the Ni loading. In particular, the 40% Ni/YSZ catalyst displayed the best performance, followed by the 30% Ni/YSZ catalyst. The improved activity at high Ni loading (40% Ni) was attributed to the increase in hydrogen coverage and improved site for both H2 and CO2 adsorption and activation.

Supporting high-loading Ni on SBA-15 as highly active and durable catalyst for ammonia decomposition reaction

Although supported Ni is generally considered the most active non-noble metal catalyst for decomposing NH3 to produce COx-free H2, its activity is not sufficient. Herein, supporting high-loading Ni on SBA-15 is explored to alleviate the low intrinsic activity issue of Ni. SBA-15 supports with tunable textual properties are synthesized to support Ni catalyst for NH3 decomposition. Characterization shows that Ni catalyst with a loading close to 40 wt% supported on SBA-15 with the largest specific surface area (Ni/SBA-15-80) exhibits a NH3 decomposition performance much better than those reported on other Ni-based NH3 decomposition catalysts, resulting from its favorable textural properties and high Ni loading. In addition, Ni/SBA-15-80 shows excellent catalytic stability, with no activity degradation over an 80-h NH3 decomposition test. This work reveals the importance of textural properties of support and Ni loading to NH3 decomposition performance and can provide a new idea for synthesizing high-performance NH3 decomposition catalysts.

Ni-CeO2 Catalyst with High Ni Loading Prepared by Salt-Assisted Solution Combustion for CO2 Methanation

An Ni-CeO2 catalyst with high Ni loading (50 wt.%) prepared by a salt-assisted solution combustion method was characterized by different methods and used for CO2 methanation. The specific surface area of the Ni-CeO2 catalyst prepared by salt-assisted solution combustion is 7 times that of the catalyst prepared by conventional solution combustion. The Ni-CeO2 catalyst prepared by salt-assisted solution combustion has smaller particle sizes of Ni and exhibits excellent activity at low temperatures. The high Ni loading and small Ni particle size can provide more metal Ni site and Ni-CeO2 interface, which help to improve the CO2 methanation performance.

Hydrogenation of 2-methylnaphthalene over bi-functional Ni catalysts

Nickel catalysts were synthesized by incipient wetness impregnation and coprecipitation and compared to a commercial Ni/kieselguhr catalyst for selective hydrogenation of 2-methylnaphthalene to yield methyldecalin. The catalysts were characterized using N2 physisorption, TGA, XRD, and TEM. The apparent activation energy for hydrogenation depends on the support identity, with the highest value (87 kJ/mol) obtained for Ni/SiO2-Al2O3 and the lowest (30 kJ/mol) for Ni/kieselguhr. The selectivity to cis-/trans-methyldecalin varied as a function of both catalyst identity and reaction conditions, with high selectivity to cis-methyldecalin obtained using catalysts with higher Ni loadings and at lower reaction temperatures. The impregnation of a precious metal onto coprecipitated Ni catalysts also changed their selectivity, as catalysts containing ruthenium selectively formed cis-methyldecalin, whereas platinum catalysts produced mostly trans-methyldecalin. This research demonstrates that Ni catalysts can be useful for producing inexpensive catalysts for hydrogenation of polyaromatic-containing feedstocks.

Green synthesis of MCM-41 derived from renewable biomass and construction of VOx-Modified nickel phyllosilicate catalyst for CO2 methanation

In order to achieve green synthesis of MCM-41 and address the sintering problem of Ni-based catalyst supported on silica material, MCM-41 with regular spherical morphology was prepared using sodium silicate extracted from renewable equisetum fluviatile as silicon source, and then a group of nickel phyllosilicates were synthesized via the reaction of MCM-41 sphere and nickel nitrate under hydrothermal condition. Much denser nanosheets corresponding to lamellar nickel phyllosilicate were formed on the surface of MCM-41 sphere with the raise of hydrothermal temperature in the range of 180–220 °C, resulting in the nickel content varying from 17.2 to 41.8 wt%. Fine Ni particles with size smaller than 6 nm could be obtained on the 750oC-reduced catalyst owing to the strong nickel-silica interaction derived from Ni-phyllosilicate. After the addition of V2O5 promoter, Ni particle size was further reduced to around 4.5 nm at high Ni loading above 30 wt%. Vanadium species was in the mixed valence state of V(III), V(IV) and V(V) after reduction, which increased the electron cloud density of Ni0, resulting in high catalytic activity of the VOx-modified Ni-phyllosilicate catalyst for CO2 methanation. In a 100 h-400oC-lifetime test and 600 °C-steam hydrothermal treatment, the VOx-modified Ni-phyllosilicate catalyst also showed high long-term stability, excellent sintering resistance of metallic nickel particles and high hydrothermal stability due to the strong surface confinement effect of nickel phyllosilicate and promotion of VOx species. In all, this work provided a green synthesis of MCM-41 as well as an efficient Ni/SiO2 catalyst derived from nickel phyllosilicate for CO2 methanation.

Highly Efficient Ni-Phyllosilicate Catalyst with Surface and Interface Confinement for CO2 and CO Methanation

For the conventional Ni/SiO2 catalyst, it is a challenge to address the sintering problem of Ni particles, especially at high Ni loading. A series of Ni-phyllosilicate catalysts were prepared through the hydrothermal reaction of mesoporous SiO2 nanorods (SRs) and nickel nitrate, followed by an impregnation modification of CeO2. Hydrothermal temperature played an important role in the formation of nickel phyllosilicate. A small amount of Ni-phyllosilicate with a Ni content of 18.56 or 23.88 wt % was formed at a low hydrothermal temperature of 120 or 160 °C, and a large amount of nanosheet-like Ni-phyllosilicate with the Ni content as high as 31.65 wt % was obtained at a high hydrothermal temperature of 200 °C. The prepared Ni-phyllosilicate catalysts were beneficial to obtain Ni particles with small sizes (3.3–6.3 nm), even though they were reduced at 750 °C and possessed high Ni loadings (18.56–31.65 wt %) owing to the surface and interface confinement of nickel phyllosilicate. After the modification of CeO2 using an impregnation method, the CeO2 promoter could further reduce the Ni particle size and increase hydrogen and carbon dioxide uptakes. The CeO2-modified Ni-phyllosilicate catalyst (NPS-180-5C) was the best catalyst in this work, which could reach the thermodynamic equilibrium of CO methanation above 350 °C and exhibited high catalytic activity for CO2 methanation. In addition, for the 55 °C-100 h-lifetime test for CO2 methanation and 600 °C-6 h-100% steam treatment tests, NPS-180-5C also showed an excellent antisintering property and higher hydrothermal stability than the impregnated one (N/SR-Im) owing to its special structure and confinement effect as well as promotion of CeO2 species. In all, the CeO2-modified SR-derived Ni-phyllosilicate catalyst could not only effectively suppress the problem of easy sintering of metallic Ni particles on the conventional Ni/SiO2 catalysts but also exhibit high catalytic activity and hydrothermal stability, which was a promising catalyst for both CO2 and CO methanation reactions.

Robust nickel silicate catalysts with high Ni loading for CO2 methanation.

CO2 is the main component of greenhouse gases and also an important carbon source. The hydrogenation of CO2 to methane using Ni-based catalysts can not only alleviate CO2 emissions but also obtain useful fuels. However, Ni-based catalysts face one major problem of the sintering of Ni nanoparticles in the process of CO2 methanation. Thus, this work has synthesized a series of efficient and robust nickel silicate catalysts (NiPS-X) with different nickel content derived from nickel phyllosilicate by the hydrothermal method. It was found that the Ni loading plays a critical role in the structure and catalytic performance of the NiPS-X catalysts. The catalytic performance gradually increases with the increase of Ni loading. In particular, the highly dispersed NiPS-1.6 catalyst with a high Ni loading of 34.3 wt% could obtain the CO2 conversion greater than 80%, and the methane selectivity was close to 100% for 48 h at 330 °C and the GHSV of 40,000 mL g-1 h-1 . The excellent catalytic property can be assigned to the high dispersion of Ni nanoparticles and the strong interaction between the active component and the carrier, which is derived from a unique layered silicate structure with lots of nickel phyllosilicate and a large number of Lewis acid sites.

Effect of nickel loading on the performance of Ni/MgAl2O4 catalysts for LPG steam reforming

Ni catalysts with different loadings (10, 15 and 20 wt%) supported on MgAl2O4 were studied for Liquefied Petroleum Gas (LPG) steam reforming. In-situ X-ray diffraction (XRD) and XANES (X-ray absorption near-edge structure), analyses showed that the initial reduction temperature was related to the percentage of Ni present in the catalyst. Extended X-ray absorption fine structure (EXAFS) data indicated similar Ni-Ni interatomic distances for all the samples and very close to the simulated value found for reference of Ni0, indicating the complete reduction of the samples. MgAl2O4 supported Ni catalysts were active for LPG steam reforming at 873 K, with some deactivation after 24 h of reaction. The samples with higher Ni loadings (20Ni/MgAl2O4 and 15Ni/MgAl2O4) showed similar LPG steam reforming products, with H2 representing around 78% of the products detected in the gas phase (dry molar basis). 10Ni/MgAl2O4 was less active, although it also presented high H2 formation. Thermogravimetric analysis showed that carbon deposition was a significant factor for catalyst deactivation.

Nickel nanoparticles supported on nitrogen–doped carbon nanotubes are a highly active, selective and stable CO2 methanation catalyst

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.

Mechanism of Nickel Phyllosilicate Formation by Laser Ablation in Liquid

One-step synthesis of nickel-phyllosilicate (Ni-PS) nanocomposites was achieved using a femtosecond-reactive laser ablation in liquid (fs-RLAL) technique. The focusing of intense femtosecond laser pulses onto a silicon wafer immersed in aqueous nickel nitrate generated Ni-PS with high Ni loading in excess of 20 wt % under alkaline pH conditions. Analysis of the dissolved species in solution present after laser processing revealed that silicic acid was the key dissolved ablation product that reacted with the nickel nitrate to form the Ni-PS under alkaline conditions. When the solution was below pH 7, no silicic acid was generated from ablation, and consequently, no Ni-PS was formed in the dried product. The mechanism of Ni-PS formation from fs-RLAL of a silicon wafer immersed in aqueous nickel nitrate solutions is discussed. On the basis of this mechanism, it is expected that the fs-RLAL method will be capable of generating a variety of metal-phyllosilicates from different metal salt precursors.

Three-Dimensional Mesoporous Ni-CeO2 Catalysts with Ni Embedded in the Pore Walls for CO2 Methanation

Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO2 methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO2-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO2-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO2 methanation. Furthermore, the 50% Ni-CeO2-CSC catalyst was stable for 50 h at 300° and 350 °C in CO2 methanation. The characterization results illustrate that the 50% Ni-CeO2-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO2. On the contrary, the 50% Ni-CeO2-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO2 methanation due to the larger size of the Ni and CeO2 particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO2-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO2 methanation.

Three-Dimensional Networked Ni-Phyllosilicate Catalyst for CO2 Methanation: Achieving High Dispersion and Enhanced Stability at High Ni Loadings

It is a great challenge for nickel-based catalysts to obtain high-temperature stable Ni nanoparticles with high dispersion at high loadings. To address this problem, a group of three-dimensional (3...

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.