Ni-containing Catalysts Research Articles

Efficiency study of nickel-containing glass-fiber catalysts for CO2 methanation

The work is dedicated to the synthesis and investigation of Ni-containing catalysts based on glass-fiber carriers (GFC) with an additionally deposited secondary layer of porous SiO2 for the process of carbon dioxide methanation. Ni-based GFCs were prepared using the surface thermosynthesis (STS) and pulse surface thermosynthesis (PSTS) methods, involves heat treatment of the catalyst with the supported Ni precursor at a high heating rate; such procedure was not applied earlier for production of CO2 methanation catalysts. The GFC sample prepared by the PSTS method with a fuel additive in the precursor composition is characterized by a more uniform distribution of Ni particles on the catalyst surface and better dispersion of Ni, smaller crystallite size: NiO crystallites in this freshly prepared GFCs are smaller than 10 nm and Ni crystallites in reduced catalysts are <30 nm. As a result, this sample demonstrated the highest apparent activity in the methanation reaction among all synthesized GFCs, it has also showed a significantly higher specific activity per unit mass of nickel compared to the commercial Ni-Al2O3 analogue. The synthesized catalysts are original, they can be effectively applied for development of novel highly efficient technologies for energy conversion/storage systems and greenhouse gas emission control.

Fe2O3/γ-Al2O3 and NiO/γ-Al2O3 catalysts for the selective catalytic oxidation of ammonia

Ammonia, a significant atmospheric pollutant, requires effective emission control due to its inherent toxicity and the generation of secondary pollutants like particulate matter. This control can be achieved through various methods, including catalytic processes. Therefore, our study focuses on evaluating the potential of catalysts based on iron oxide and nickel oxide supported on γ–Al2O3 for the selective catalytic oxidation of NH3 to N2 (NH3-SCO). The γ–Al2O3 was obtained by thermal decomposition of aluminum hydroxide, and 5 or 10 wt% of Fe or Ni was added through wetness incipient impregnation. XRD diffractograms confirmed the formation of the γ–Al2O3 phase. XRD, H2-TPR, and UV–vis DRS data showed the presence of Fe2O3, NiO, and NiAl2O4 in the catalysts. Introducing metal oxides onto the support led to a drop in the specific area, pore size, pore volume, and NH3 desorption, which was higher for the catalysts containing Fe. The catalysts were active in NH3-SCO, and the insertion of Fe or Ni was essential because it promoted a significant increase in the NH3 conversion (∼75 % Fe and ∼55 % Ni), compared to pure support (∼8 %), mainly from 400 °C. However, doubling the metal content has not resulted in a considerable increase in NH3 conversion. The N2 selectivity was higher for the catalysts containing Ni (∼85 %) from 400 °C compared to catalysts containing Fe (∼76 %). Such behavior was due to the larger surface area of the Ni-containing catalysts. Despite that, the 5Fe/γ–Al2O3 catalyst emerged as the most effective option for NH3-SCO applications, combining higher NH3 conversion and good N2 selectivity.

Co and Ni-containing catalysts for heavy oil refining: the effect of ethanol on the composition and structure of catalytic cracking products

The study deals with the products of thermal processing of heavy oil in the presence of Ni- and Co-containing catalysts that are formed in situ from the mixture of corresponding salts with ethanol. In comparison with thermal cracking, in the catalytic process the yield of bright fractions increases from 51 to 63 % and the yield of coke decreases from 3 to 2 wt.%. In the case of mixed Ni and Сo catalyst, the least yields of gas (5 wt.%) and coke (0.1 wt.%) are observed. A decrease in the sulfur content occurs in the products of both thermal (by 17 %) and catalytic cracking (from 12 to 32 rel.%) predominantly due to its removal as gaseous products. The structuralgroup characteristics of the averaged asphaltene molecules were studied before and after heavy oil cracking. XRD of solid cracking products was used to identify Ni0.96S, Ni9S8 and Co9S8 phases.

Nickel-containing catalysts for ethylene conversion to motor fuel components and light alkenes

Polyfunctional Ni-containing catalysts supported on the B2O3-Al2O3 and MoO3-Al2O3 were prepared by a sequential impregnation. They were evaluated in ethylene conversion to C5+ alkenes or propylene. The catalysts were characterized by X-ray diffraction, Fourier transformed infrared spectroscopy, Fourier transformed infrared spectroscopy of adsorbed CO, UV-VIS diffuse reflectance spectroscopy, temperature programmed reduction and temperature-programmed desorption of NH3. NiO/B2O3-Al2O3 samples containing Ni2+ cations chemically bonded to the acid support are the most effective catalysts for ethylene oligomerization. The NiO/MoO3-Al2O3 catalyst activity in the ethylene conversion to propylene is related with the presence of ethylene dimerization active sites, i.e. Ni2+ cations bonded to the support acidic sites, and active sites of metathesis in the form of monomolybdate species.

Primary alcohols as killers of Ni-based catalysts in transfer hydrogenation

The effect of different types of alcohols used as hydrogen donors on the activity of a metal Ni-based catalyst in the hydrogenation of benzofuran as a model substrate under transfer hydrogenation conditions has been studied. The hydrogenation process of benzofuran using 2-PrOH as a hydrogen donor leads sequentially to dearomatization and then to deoxygenation of the substrates. At the same time, the use of primary alcohols such as MeOH, EtOH and 1-PrOH as hydrogen donors leads to irreversible deactivation of the Ni-containing catalyst. A clear mechanism of deactivation of Ni-based metal catalysts by primary alcohols has been established. The interaction of the catalyst with primary alcohols at a temperature of 250 °C leads to the formation of an inactive Ni3C carbide phase, as well as sintering and segregation of metal particles on the surface of the alumina support.

Highly Selective and Stable Cu Catalysts Based on Ni-Al Catalytic Systems for Bioethanol Upgrading to n-Butanol.

The catalytic upgrading of ethanol into butanol through the Guerbet coupling reaction has received increasing attention recently due to the sufficient supply of bioethanol and the versatile applications of butanol. In this work, four different supported Cu catalysts, i.e., Cu/Al2O3, Cu/NiO, Cu/Ni3AlOx, and Cu/Ni1AlOx (Ni2+/Al3+ molar ratios of 3 and 1), were applied to investigate the catalytic performances for ethanol conversion. From the results, Ni-containing catalysts exhibit better reactivity; Al-containing catalysts exhibit better stability; but in terms of ethanol conversion, butanol selectivity, and catalyst stability, a corporative effect between Ni-Al catalytic systems can be clearly observed. Combined characterizations such as XRD, TEM, XPS, H2-TPR, and CO2/NH3-TPD were applied to analyze the properties of different catalysts. Based on the results, Cu species provide the active sites for ethanol dehydrogenation/hydrogenation, and the support derived from Ni-Al-LDH supplies appropriate acid-base sites for the aldol condensation, contributing to the high butanol selectivity. In addition, catalysts with strong reducibility (i.e., Cu/NiO) may be easily deconstructed during catalysis, leading to fast deactivation of the catalysts in the Guerbet coupling process.

Approaches to the design of efficient and stable catalysts for biofuel reforming into syngas: doping the mesoporous MgAl2O4 support with transition metal cations.

The mesoporous MgAl2O4 support is promising for the design of efficient and stable to coking catalysts for natural gas and biofuel reforming into syngas. This work aims at doping this support with transition metal cations (Fe, Cr, Ti) to prevent the incorporation of Ni and rare-earth cations (Pr, Ce, Zr), loaded by impregnation, into its lattice along with providing additional sites for CO2 activation required to prevent coking. Doped MgAl1.9Me0.1O4 (Me = Fe, Ti, Cr) mesoporous supports prepared by the one-pot evaporation-induced self-assembly method with Pluronic P123 triblock copolymers were single-phase spinels. Their specific surface area varies in the range of 115-200 m2 g-1, decreasing to 90-110 m2 g-1 after successive addition of the supporting nanocomposite active component 10 wt% Pr0.3Ce0.35Zr0.35O2 + (5 wt% Ni + 1% Ru) by impregnation. Mössbauer spectroscopy for iron-doped spinels confirmed the spatially uniform distribution of Fe3+ cations in the lattice without clustering being mainly located at the octahedral positions. Fourier-transform infrared spectroscopy of the adsorbed CO molecules was performed to estimate the surface density of metal sites. In methane dry reforming, the positive effect of MgAl2O4 support doping was observed from both a higher turn-over frequency as compared with the catalyst on the undoped support as well as the highest efficient first-order rate constant for the Cr-doped catalyst as compared with published data for a variety of Ni-containing catalysts based on the alumina support. In the reaction of ethanol steam reforming, the efficiency of catalysts on the doped supports is comparable, while exceeding that of Ni-containing supported catalysts reported in the literature. Coking stability was provided by a high oxygen mobility in the surface layers estimated by the oxygen isotope heteroexchange with C18O2. A high efficiency and coking stability were demonstrated in the reactions of methane dry reforming and ethanol dry and steam reforming in concentrated feeds for the honeycomb catalyst with a nanocomposite active component on the Fe-doped MgAl2O4 support loaded on the FeCrAl-alloy foil substrate.

A Novel Model Parameter for the Assessment of the Dimerization of n-Butenes over Ni-Containing Aluminosilicate Catalysts

Previous investigations on the dimerization of n-butenes over Ni-containing Al-MCM-41/ZSM-5 mixed-phase catalysts have shown a correlation between the conversion and the Ni/(Al + Ni) ratio as well as between the conversion and the metal–support interaction, which is represented by the reduction degree. In the present work, both approaches are combined to a novel model parameter, which allows to determine the proportion of active Ni species on the Al-Ni site pairs and thus provides crucial insights into formation of catalytically active nickel sites as well as their effects on the selective formation of low-branched dimers.

Use of Ni-containing catalysts for synthetic olive mill wastewater steam reforming

The olive oil mill wastewater (OMW) is a by-product (with a high organic load) derived from the production of the olive oil. The OMW steam reforming (OMWSR) process was studied herein, aiming to decrease the environmental damage of such effluents; simultaneously, the waste is economically and energetically valorized with the H2 production. Several Ni-containing catalysts were prepared and tested to compare their performances for the OMWSR using a synthetic OMW effluent; still, stability tests were also carried out. The materials were extensively characterized: thermogravimetric analysis, temperature-programmed oxidation/reduction, temperature-programmed desorption of CO2/NH3, chemisorption of H2, inductively coupled plasma optical emission spectrometry and physical adsorption-desorption of N2 at −196 °C. Amongst the materials tested, the Ni–Ru/SiO2 sample stood out, exhibiting high catalytic performance: at 400 °C, the H2 yield (>8 molH2·molOMW-1) and conversion of total organic carbon (≈75%) were high during all the 24 h of the long-term test, with only a small deactivation being noticed.

CO2 Methanation Over Ni-Sepiolite Catalysts

In this study, it was aimed to develop new catalysts to increase the conversion of environmentally harmful carbon dioxide gas to methane which is a valuable fuel. By using a natural clay mineral sepiolite (SEP) as support material; 6-8% (weight-weight) Ni-containing catalysts were prepared by impregnation. Catalysts were characterized by XRD and FT-IR analysis. Reaction conditions of catalytic hydrogenation of carbon dioxide for methane production were determined as: H2/CO2 = 4 molar ratio, the temperature range of 300-600°C at atmospheric pressure. The output gas mixture was analyzed using the µGC. The activities of the catalysts were determined in terms of carbon dioxide conversion and methane selectivity. 6%Ni/SEP and 8%Ni/SEP provided 65.76% and 68.42% carbon dioxide conversion at 400°C, respectively. In addition, both catalysts exhibited high methane selectivity at 300 and 400°C (>98%).

Study of mayenite produced from waste eggshell as support for Ni–Co catalysts for biomass tar cracking

Ultrasonication-promoted synthesis was applied to produce mayenite (M-CES) with properties similar to mayenite produced with commercial reagents, using calcined eggshell waste as a calcium source. Monometallic 10Ni/M-CES (10 wt.% Ni) and 10Co/M-CES (10 wt.% Co) and bimetallic 5Ni5Co/M-CES (5 wt.% Ni and 5 wt.% Co) catalysts were synthesized by the wet impregnation method. Catalyst 10Co/M-CES showed a noticeably lower metal dispersion when compared to the Ni-containing catalysts. 5Ni5Co/M-CES bimetallic catalyst showed the highest metal dispersion, and XRD analysis proved the Ni–Co alloy formation. The performance of Ni–Co catalysts for hydrocarbon cracking was evaluated by methane and propane catalytic decomposition. The alloy formation between Ni and Co in the bimetallic catalyst provided a reduction in the start temperature of the cracking reaction of approximately 80 °C and 110 °C for methane and propane, respectively, when compared to monometallic catalysts. A synergistic effect was also observed by a decrease in carbon deposition and an increase in the catalytic activity of 5Ni5Co/M-CES. The use of eggshell waste to produce mayenite support for tar cracking catalysts has proved to be attractive to add value to the eggshell waste.

Direct Reduction in Greenhouse Gases by Continuous Dry (CO2) Reforming of Methane over Ni-Containing SHS Catalysts

The world of energy is on the cusp of profound transformation. Hydrogen or hydrogen-containing fuel mixtures in the form of synthesis gas, as carriers of clean energy, will be in the short term among the most efficient solutions to pressing environmental problems, reducing the amount of greenhouse gases as well as pollution of cities and dependence on oil-based fuels. Carbon dioxide conversion of methane is the most promising method for the production of synthesis gas due to the simultaneous consumption of two greenhouse gases and, accordingly, a successful solution to environmental problems. Ni/Mn-based catalysts have been prepared by self-propagating high-temperature synthesis (SHS) for this process. The samples were characterized by X-ray diffraction, scanning electron microscopy, and nitrogen porosimetry. The effects of the catalysts’ composition on activity, selectivity, and product yield were investigated. The influence of the content of Ni, Mn on the behavior of catalysts has been established. Comparison of spinels with different component ratios showed that they have a defective structure. Non-stoichiometric spinels with highly defective catalyst structures were obtained due to very high heating and cooling rates during SHS. They work as active sites, which underlies the high activity of the catalysts.

Production of Hydrogen and Carbon Nanofibers by the Catalytic Decomposition of Methane over Ni-Containing Catalysts

This paper is devoted to technology for producing pure hydrogen by catalytic decomposition of light hydrocarbons. A set of nickel-containing catalysts was prepared using the corresponding salts. The content of active metal (Ni) varied from 10 to 90 wt %. The activity of the catalyst in the process of methane decomposition was studied. It has been found that the most promising method for the synthesis of catalysts is the melting of salts of metal. The maximum yield of hydrogen was 416 L/gcat at a Ni content of 90 wt % at a temperature of 675 °C and a pressure of 5 atm.

Kinetic Regularities of Methane Dry Reforming Reaction on Nickel-Containing Modified Ceria–Zirconia

The Ni-containing catalysts based on ceria–zirconia doped with Ti and Ti+Nb were prepared by the solvothermal method in supercritical fluids. Ni deposition was carried out by incipient wetness impregnation and the one-pot technique. All materials were investigated by a complex of physicochemical methods (XRD, BET, TEM, H2-TPR). Samples catalytic properties were studied in methane dry reforming in the plug-flow reactor. Conversions of CH4 and CO2, H2/CO ratio, and CO and H2 yields were measured, and detailed kinetics analysis was carried out. The influence of Ni loading method and support modification on the catalytic behavior in the methane dry reforming process was studied. The preparation method of catalysts affects the textural characteristics. For one-pot samples, pore volume and surface area are lower than for impregnated samples. For catalysts on modified supports, strong metal–support interaction was shown to increase catalytic activity. A reduction pretreatment of samples was shown to have significant influence on their catalytic properties. The kinetic parameters such as reaction rate constant at 700 °C, effective activation energy, and TOF were estimated and analyzed.

Ni-Containing Catalysts

Murray Raney used Nickel for the first time as a hydrogenation catalyst over one century ago [...]

Rh- and Rh–Ni–MgO-based structured catalysts for on-board syngas production via gasoline processing

Rh/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl and Rh/Ni–MgO/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl FeCrAlloy wire mesh supported catalysts were prepared via multistep procedure. They were characterized by XRD, SEM and TEM techniques. A comparative study of autothermal reforming (ATR) of isooctane and simulated gasoline (blends of isooctane, ortho-xylene and naphthalene) over Rh/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl and Rh/Ni–MgO/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl was performed. Both catalysts showed excellent performance in ATR of isooctane at molar ratios of O2:C = 0.51 and H2O:C = 2.59, T = 750°С and GHSV = 10000 h−1. In the ATR of isooctane – o-xylene blend in presence of Rh–Ni-containing catalyst carbon formation was observed. Rh-containing catalyst demonstrated rather good activity and stability even in the case of isooctane – o-xylene – naphthalene blend.

Use of Ni-Containing Catalysts for the Olive Mill Wastewater Steam Reforming

The olive oil mill wastewater (OMW) is a by-product (with a high organic load) derived from the production of the olive oil. The OMW steam reforming (OMWSR) process was studied herein, aiming to decrease the environmental damage of such effluents; simultaneously, the waste is economically and energetically valorized with the H2 production. Several Ni-containing catalysts were prepared and tested to compare their performances for the OMWSR using a synthetic OMW effluent; still, stability tests were also carried out. The materials were extensively characterized: thermogravimetric analysis, temperature-programmed oxidation/reduction, temperature-programmed desorption of CO2 /NH3, chemisorption of H2, inductively coupled plasma optical emission spectrometry and physical adsorption-desorption of N2 at -196 oC. Amongst the materials tested, the Ni-Ru/SiO2 sample stood out, exhibiting high catalytic performance: at 400 oC, the H2 yield (> 8 molH2·molOMW) and conversion of total organic carbon (≈ 75 %) were high during all the 24 h of the long-term test, with only a small deactivation being noticed.

Catalytic decomposition of methane on Ni-containing catalysts prepared by heterophase sol-gel method

The most promising catalysts for the catalytic decomposition of methane are nickel-containing systems, since nickel has high activity, thermal stability, thermal conductivity, and relatively low cost. In this work, catalysts were prepared by the heterophase sol-gel method and investigated using catalytic equipment. The catalysts showed high stability and lifetime during the catalytic decomposition of methane at temperatures ranging from 535 to 675°C.

Influence of flowrate and composition of the alkanes dehydrogenation process feedstock on by-products concentration in the linear alkylbenzene sulfonic acid manufacturing technology

Synthesis of surfactants based on linear alkylbenzenesulfonates is a complex multi-stage process that includes the following stages: alkanes dehydrogenation on Pt-containing catalyst, dienes hydrogenation on Ni-containing catalyst, HF-catalyzed alkylation of benzene with alkenes, and sulfonation of linear alkylbenzenes (LAB) with sulfur trioxide in a film reactor yielding alkylbenzene sulfonic acid (ABSA). When developing mathematical models of multi-stage processes it is necessary to consider the contingency of the apparatuses in the chemical-technological system. The design of the sulfonation reactor, as well as the feedstock composition and the dehydrogenation unit performance, i.e., the LAB flowrate to sulforator, significantly affects the ABSA synthesis efficiency. The studies were performed using the unsteady mathematical models of conjugated dehydrogenation and sulfonation processes. As a result, we determined the optimal design of the sulfonation reactor with number of tubes n = 40 and diameter d = 43 mm. We also outlined the preferred method for increasing the ABSA yield by switching to a double-reactor alkane dehydrogenation scheme with a flowrate of 100 m3/h for two dehydrogenation reactors. This increases yield of alkenes and LAB by 71 %wt.

Steam Conversion of Methane on Fechral

The vapor conversion of methane on Ni-containing catalysts on structured metal supports made from a Fe–Cr–Al alloy (fechral) is studied. A very high hydrogen content is observed in the products of the reaction for low percent 1% Ni/fechral catalysts (around 75% at 870°C).