Supported Nickel Catalysts Research Articles

Process Intensification in Ammonia Synthesis Using Novel Coassembled Supported Microporous Catalysts Promoted by Nonthermal Plasma

The Integrated Process Intensification approach is used for the synthesis of ammonia using novel coassembled microporous silica supported nickel catalysts and nonthermal plasma reactors operating at ca. 140 ± 10 °C and ambient pressure. The conversion levels of nitrogen and hydrogen to ammonia are similar to that achieved by the current industrial best practice which is, however, carried out at 100–250 bar and the temperatures 350–550 °C. In order to achieve continuous plasma generation, a novel catalyst, which has a surface area of ca. 200 m2/g in the form of lamellae with ca. 2 nm thick plates of nickel catalyst sandwiched between the silica support, has been used in the presence of plasma catalysis promoters in the form of spheres made from high permittivity material. In addition to process variables (flow rate, feed composition, and plasma power input), the effect of the electrode configuration on conversion was investigated. It is shown that the catalyst activity remained constant over a continuous p...

Effect of Design Parameters on the Internal Steam Reforming of Methane in Solid Oxide Fuel Cell Systems

The operation of solid oxide fuel cell systems with the internal steam reforming of methane over supported nickel catalysts is studied. A mathematical model including heterogeneous chemistry, electro-chemistry, mass transport, and porous media transport is developed to explore the thermal energy coupling between the steam reforming and the electrochemical reactions, independent of the geometrical structure. The role of catalyst activity, inlet temperature, current density, and operating pressure in the system behavior is evaluated. A sensitivity analysis is also performed for different design parameters. The effect of flow configuration on the operation of the system is analyzed and compared based on multiple performance criteria. It is shown that the internal steam reforming within the fuel cell system can result in an overall auto-thermal operation which increases efficiency and simplifies the design process. However, a local cooling effect may occur close to the entrance of the reformer. The use of less active catalysts can cause the slippage of the methane. To reduce both the overall temperature increase across the fuel cell and the local cooling caused by the endothermic steam reforming reactions, increasing the operating pressure is found to be an effective approach. High system efficiency is obtained with increasing the operating pressure or decreasing the current density. The more efficient system is found for a co-flow configuration, while significant temperature gradients near the entrance of the reformer are not desirable for ceramic solid oxide fuel cell systems.

Oxygen surface groups of activated carbon steer the chemoselective hydrogenation of substituted nitroarenes over nickel nanoparticles.

Oxygen surface groups of activated carbon, produced by nitric acid treatment, are not only able to prevent Ni particles from sintering but are also able to preferentially interact with the nitro group of substituted nitroarenes. The resulting Ni/ACOX catalyst is highly active and chemoselective for hydrogenation of nitroarenes to produce functionalized anilines and oximes.

Nickel catalysis for hydrogenation of p-dinitrobenzene to p-phenylenediamine

The activity of supported nickel catalysts (5–20% Ni) in the hydrogenation of p-dinitrobenzene to p-phenylenediamine was investigated. The catalysts were obtained by ureainduced precipitation. Activated carbon, alumina, titania, and silica gel were evaluated as supports. The most active catalysts, 5%Ni/TiO2 and 20%Ni/SiO2, provided 50–54% yields of p-phenylenediamine at complete dinitrobenzene conversion.

Study of Activated Carbon Supported Nickel Catalyst for Adsorption of Phenolic Wastewater

Study of Activated Carbon Supported Nickel Catalyst for Adsorption of Phenolic Wastewater

Ceria supported nickel catalysts for CO removal from H2-rich gas

AbstractCO in H2-rich gas must be removed to meet various requirements in industrial applications. Four methods, i.e., the precipitation method using aqueous ammonia, the complexing method using urea, the complexing method using citric acid and the precipitation method using ammonium carbonate, were adopted to prepare samples NiO/CeO2 as catalyst precursors for removal of CO from H2-rich gas via selective methanation reaction. The sample NiO/CeO2 prepared by the precipitation method using aqueous ammonia as precipitant exhibited the highest catalytic activity both for CO methanation and for CO2 methanation after reduction prior to the catalytic reaction. Chlorine ion was then doped to suppress CO2 conversion. Effect of chlorine doping was investigated. Over the optimal catalyst 40%Ni(Cl0.2)/CeO2, CO in the H2-rich gas was removed to below 10 ppm with selectivity of 60% or higher at reaction temperatures 230–250 °C in the test period of 75 h.

Structural and surface properties of heterogeneous catalysts: Nature of the oxide carrier and supported particle size effects

Heterogeneous catalysts, investigated by several techniques, such as XRD, XPS, TEM, TPR/TPO, able to ascertain their structural, chemical, electronic and morphology properties are reviewed with respect to selected results obtained by the group during approximately the last twenty five years. The field of application covers different catalytic processes such as alkene hydrogenation over noble metal catalysts, hydrodesulfurization (HDS) and environmental catalysis. In particular the following subjects are described: the peculiarity of a support like pumice, in relation to the hydrogenation activity of the supported noble metals; supported gold and supported gold containing alloy catalysts for different types of reactions; the importance of the CoMoS precursors and the structure of bimetallic PdAu and PtAu for hydrotreating processes; the effect of a sulfatable oxide, such as TiO2, on the CH4 oxidation activity of supported Pd catalysts; different preparation methods influencing significantly the catalytic behavior of supported nickel catalysts for methane conversion processes. The reviewing of the different case studies illustrates the importance of the interaction between support and active metals ultimately determining the surface distribution of the active sites and their final catalytic activity.

Hydrogenation of CO2 to synthetic natural gas over supported nickel catalyst: effect of support on methane selectivity

Nickel-based catalysts were prepared by co-precipitation method and applied for the CO2 conversion to synthetic natural gas. Two batches of catalysts were prepared with the different amount of Ni and were characterized by various techniques such as XRD, TPD, TPR, XPS, and TEM. Catalytic activity was studied under atmospheric pressure, a temperature of 350 °C, GHSV of 2000 h−1 and N2:CO2:H2 = 4:1:4. Highest CO2 conversion achieved was 70 with 99 % selectivity to methane. The activity of catalysts depends on the nickel content and nickel dispersion. Selectivity to methane depends inversely on the concentration of weak and moderate strength basic sites. Comparable quantity of basic sites present over catalysts, the methane selectivity is observed to be similar but the CO2 conversion changed due to change in Ni content. Catalysts having equal amounts of Ni exhibited increase in CH4 selectivity with the decrease in basic sites.

CO2 selective hydrogenation to synthetic natural gas (SNG) over four nano-sized Ni/ZrO2 samples: ZrO2 crystalline phase & treatment impact

Two type zirconia (monoclinic and tetragonal phase ZrO2) carriers were synthesized via hydrothermal route, and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed thermal treatment at 300°C to 500°C, for the CO2 selective hydrogenation to synthetic natural gas (SNG). The catalysts were characterized by XRD, CO2-TPD-MS, XPS, TPSR (CH4, CO2) techniques. For comparison, the catalyst NZ-W-400 (monoclinic) synthesized in water solvent exhibited a better catalytic activity than the catalyst NZ-M-400 (tetragonal) prepared in methanol solvent. The catalyst NZ-W-400 displayed more H2 absorbed sites, more basic sites and a lower temperature of initial CO2 activation. Then, the thermal treatment of monoclinic ZrO2 supported nickel precursor was manufactured at three temperature of 350, 400, 500°C. The TPSR experiments displayed that there were the lower temperature for CO2 activation and initial conversion (185°C) as well as the lower peak temperature of CH4 generation (318°C), for the catalyst calcined at 500°C. This sample contained the more basic sites and the higher catalytic activity, evidenced byCO2-TPD-MS and performance measurement. As for the NZ-W-350 sample, which exhibited the less basic sites and the lower catalytic activity, its initial temperature for CO2 activation and conversion was higher (214°C) as well as the higher peak temperature of CH4 formation (382°C).

Reaction mechanism and kinetic modeling for the hydrodeoxygenation of triglycerides over alumina supported nickel catalyst

The present work provides a systematic study to delineate the reaction mechanism and develop a mechanistic kinetic model for the hydrodeoxygenation (HDO) of triglycerides (TG) over alumina supported nickel catalyst. The HDO of 1:2 molar mixtures of tripalmitin and tristearin was studied in a batch reactor over a wide range of process conditions. The results showed that TG instantaneously converted to respective fatty acids. The fatty acids further converted to the fatty aldehydes. The fatty aldehydes, then, rapidly converted to alkanes by two parallel reaction pathways. The decarbonylation of fatty aldehyde (RP-I) was the dominating route compared to the reduction of the fatty aldehyde to fatty alcohol followed by its dehydration and hydrogenation (RP-II). A mechanistic kinetic model was developed based on the observed reaction pathway to correlate the experimental results. The rate constants for the conversion of palmitic acid and stearic acid to alkanes were matched closely with each other thereby demonstrating that HDO is independent of fatty acid chain length. The developed kinetic model was further validated using experimental data at various hydrogen-to-nitrogen mole ratios in the gas phase. Furthermore, the rate constants obtained for various catalyst loadings were correlated by a linear equation with zero intercept.

Liquid Phase Furfural Hydrotreatment to 2-Methylfuran on Carbon Supported Nickel Catalyst - Effect of Process Conditions

Liquid Phase Furfural Hydrotreatment to 2-Methylfuran on Carbon Supported Nickel Catalyst - Effect of Process Conditions

Catalytic reforming of toluene and naphthalene (model tar) by char supported nickel catalyst

The purpose of this study was to utilize gasification derived char as a catalyst support for tar removal. Red cedar char collected from downdraft bed gasification was chemically activated into activated carbon and impregnated with nickel acetate and nickel nitrate. The effects of nickel salts precursor, nitric acid treatment of support and reduction of nickel in hydrazine medium on catalyst performance were studied. It was found nickel nitrate was a better nickel precursor than nickel acetate for preparation of char supported nickel catalyst. The catalyst impregnated with nickel nitrate was found more active in steam reforming of toluene than the catalyst impregnated with nickel acetate. TEM results indicated that nickel particle size of the catalyst impregnated with nickel nitrate was much smaller than that of the catalyst impregnated with nickel acetate. Toluene showed higher removal efficiency than naphthalene. The presence of naphthalene decreased the toluene removal.

Attapulgite clay supported Ni nanoparticles encapsulated by porous silica: Thermally stable catalysts for ammonia decomposition to COx free hydrogen

Porous silica encapsulated attapulgite (ATP) clay supported nickel catalysts were prepared by successive precipitation-deposition method, which were tested in an ammonia decomposition for production of COx-free hydrogen. The textural and structure properties of Ni/ATP catalysts and silica encapsulated Ni/ATP catalysts were characterized by X-ray diffraction, scanning and transmission electron microscopy, N2 sorption, thermogravimetry-differential thermal analysis, hydrogen temperature-programmed reduction. The results reveal that ATP supported Ni catalysts possess a suitable specific surface area and pore volume, as well as nano-structure. Ni nanoparticles are mostly located on the external surface of ATP supports. With an increase on Ni loading content from 10 to 50 wt % (theoretical value), the ammonia conversion increases gradually. Owning to porous silica enwrapping, the Ni-30/ATP@SiO2 catalysts show a higher specific activity (17.0 mol gNi−1 h−1, 650 °C) and stability than Ni-30/ATP catalysts.

Effect of the structure of Ni/TiO2 catalyst on CO2 methanation

CO2 methanation over supported nickel catalysts attracts an increasing attention. However, the mechanism with it is still in debate. It is confirmed here that the structure of Ni/TiO2 catalyst has a significant effect on CO2 methanation. The catalyst with Ni (111) as the principal exposing facet shows higher activity with higher methane selectivity. The maximum activity for CO2 methanation is obtained at 350 °C with a CO2 conversion of 73.2% and a CO2 conversion rate of 1.56 molCO2gcat−1h−1 at a high GHSV of 60,000 h−1. This rate is higher than those reported CO2 conversion rates in the literature. According to the FTIR analysis, CO2 methanation over catalyst with Ni (111) as the principal exposing facet follows the mechanism via CO intermediate, while the catalyst with multi-facets takes the pathway of the direct hydrogenation of formate, with which nickel is only functional for hydrogen dissociation.

Methane decomposition into COx free hydrogen and multiwalled carbon nanotubes over ceria, zirconia and lanthana supported nickel catalysts prepared via a facile solid state citrate fusion method

Methane decomposition is the most effective route for the simultaneous production of COx-free hydrogen and nanocarbon. In this work, a set of porous ceria, zirconia and lanthana supported nickel catalysts were successfully synthesized via a facile solid state citrate fusion method and used for the thermocatalytic decomposition of undiluted methane for the first time. The catalysts were completely characterized for their crystalline, structural, textural and reduction properties and correlated to their catalytic performance. The active phase of fresh catalysts was found to be NiO in the CeO2 and ZrO2 supported catalysts whereas the formation of lanthanum nickel oxide solid solution was observed in the Ni/La2O3 catalyst. Various attractive porous morphologies of the fresh catalysts were confirmed by scanning electron microscopic studies. All of the catalysts exhibited high catalytic activity and stability for methane decomposition. The yield of hydrogen and carbon increased significantly with increasing the reaction temperature from 600°C to 700°C. A maximum initial hydrogen yield of 62%, 61% and 58% and a final carbon yield of 1360wt%, 1159wt% and 1576wt% was achieved over ceria, zirconia and lanthana supported catalysts respectively, at 700°C. The surface area of the catalysts could not have any significant effect on the catalytic efficiency and it was fully depended on the metal support interaction. The Ni/La2O3 catalyst showed high catalytic stability than ceria and zirconia supported catalysts due to the enhanced surface dispersion of finely crystallized Ni nanoparticles on the lanthana matrix aroused by the reduction of lanthanum nickel oxide. Moreover, bulk deposition of highly uniform multiwalled carbon nanotubes with high graphitization degree (ID/IG=0.95) with different diameters depending on the Ni crystalline size was observed over the catalysts.

Synthesis Gas Production via the Biogas Reforming Reaction Over Ni/MgO–Al2O3 and Ni/CaO–Al2O3 Catalysts

The energetic utilization of biogas, a gas mixture consisting mainly of CH4 and CO2 via the reforming or the dry reforming of methane reaction is of enormous interest as it converts these two greenhouse gases into synthesis gas (H2/CO mixtures). Nickel based catalysts have been extensively studied for both reactions, as they are highly active, but they suffer from fast deactivation by coking that can even lead to reactor blocking. It is thus desirable to learn more about their coking behavior, and their structural and catalytic stability. In this work, un-promoted and promoted with 6.0 wt% MgO or CaO alumina supported nickel catalysts (8.0 wt% Ni) were studied for the biogas reforming reaction. Supported nickel catalysts were synthesized following the wet impregnation method. The as synthesized Ni/Al2O3, Ni/MgO–Al2O3, Ni/CaO–Al2O3 samples were characterized by various techniques such as XRD, SEM, ICP and BET. Catalytic testing experiments were performed in a fixed-bed reactor at temperatures ranging from 500 to 850 °C and a feed gas mixture with a molar CH4/CO2 ratio of 1.5 simulating an ideal model biogas. It was concluded that the Ni/MgO–Al2O3 and Ni/CaO–Al2O3 catalysts exhibit higher values for XCH4, XCO2, YH2 compared to the ones of the Ni/Al catalyst for temperature ranging between 550 and 750 °C, while the opposite is evidenced for T > 750 °C. It was also evidenced that the presence of magnesium or calcium oxide in the support ensures a quite stable H2/CO molar ratio approaching to unity (ideal for the produced syngas) even for low reaction temperatures.

Enantio-differentiating hydrogenation of methyl acetoacetate over tartaric acid modified Ni catalyst at atmospheric pressure of hydrogen assisted by hydrogen transfer reaction

The enantio-differentiating hydrogenation of methyl acetoacetate was carried out under the atmospheric pressure of hydrogen (gauge pressure: 0 MPa) assisted by hydrogen transfer from 2-propanol. It was revealed that the tartaric acid-NaBr-modified supported nickel catalyst, especially Ni/CeO2, produced a higher enantioselectivity than the modified Raney nickel catalyst under the atmospheric pressure of hydrogen. Catalyst preparation and hydrogenation conditions for the hydrogenation over the modified Ni/CeO2 were studied. The Ni/CeO2 prepared by calcination at 773 K and reduction at 773 K gave the best result. The enantioselectivity of 64 % (22 % conversion) was attained under the atmospheric pressure of hydrogen at 323 K assisted the by hydrogen transfer from the solvent.

Preparation of mesoporous nanocrystalline Ni-MgAl2O4 catalysts by sol-gel combustion method and its applications in dry reforming reaction

A surfactant assisted sol-gel combustion method was employed for the synthesis of mesoporous nanocrystalline magnesium aluminate spinel with the high specific surface area as support for nickel catalysts in the dry reforming reaction. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption (BET), Fourier transform infrared spectroscopy (FTIR), temperature programmed reduction and oxidation (TPR, TPO) techniques. The effects of several process parameters such as metal nitrate to citric acid (MN/CA) and citric acid to PEG (polyethylene glycol), (CA/PEG) ratios, pH and calcination temperature were investigated. The obtained results showed that the addition of surfactant has a significant effect on the surface area. The XRD analysis showed that the single-phase MgAl2O4 was formed at 700°C. The results revealed that the catalyst with 10wt.% Ni content and 97.1 (m2g−1) surface area and particle size of 13.7 (nm) exhibited high CH4 and CO2 conversions. In addition, CO2 conversion was higher than the CH4 conversion in all temperatures because of the occurrence of reverse water gas shift reaction.

Nickel supported on iron-bearing olivine for CO2 methanation

Calcined olivine supported nickel catalysts (Ni/olivine) were prepared by incipient wetness method and used for CO2 methanation. To investigate the structure-activity relationships of the catalysts, the structure of the olivine during calcination and that of the Ni/olivine after calcination and reduction were illustrated by means of powder X-ray diffraction, temperature programmed reduction, Mőssbauer spectroscopy and BET surface area measurement, and the CO2 methanation were evaluated by using Ni/olivine with different calcination temperatures of the olivine, Ni loadings, calcination and reduction temperatures of the catalyst. It was found that the FeOx phase formed on the surface of the calcined olivine was extracted from the olivine during its calcination, laying the base for the interaction between the surface FeOx and the NiO supported. The Ni–Fe alloy as the effective active component was formed on the calcined olivine containing mainly (MgxFe1−x)2 SiO4 and the thermal induced FeOx phase, from the reduced NiO and the partially reduced FeOx during the reduction of the Ni/olivine. The unreduced FeOx between the active phase Ni–Fe alloy and the olivine body, as the very support of the Ni–Fe alloy, plays an important role in CO2 methanation. With 6 wt.% Ni/olivine prepared under optimized condition as catalyst, at temperature of 400 °C and a H2/CO2 mole ratio of 6.0 and an hourly space velocity of 11,000 h−1, the CO2 methanation achieved 98% CO2 conversion with 99% selectivity to CH4. The Ni/olivine with strong resistance to coke deposition and abrasion could be a promising methanation catalyst, especially for fluidized bed operation.

Nickel Oxide Catalysts for Partial Oxidation of Methane to Synthesis Gas

<p class="Default">Nickel catalysts supported on different carriers (θ-Al<sub>2</sub>O<sub>3</sub>, γ-Al<sub>2</sub>O<sub>3</sub>, HZSM-5 with γ-Al<sub>2</sub>O<sub>3</sub>, HZSM-5, and NaX) have been investigated for the partial oxidation of methane. All the supported nickel catalysts showed a high activity for the formation of synthesis gas, and γ-Al<sub>2</sub>O<sub>3</sub> was the most effective among all the tested carriers. The effect of the heat-treatment temperature of the 3 wt.% Ni/γ-Al<sub>2</sub>O<sub>3</sub> catalyst on its catalytic activity was studied, and a considerable decrease in its activity was observed by the heat-treatment of the catalyst at 1000 °C compared with the catalysts prepared by the 300–800 °C – calcination. The XRD analysis suggested the formation of NiAl<sub>2</sub>O<sub>4</sub> that is a non-reducible compound at the high calcination temperature. The addition of a modifier (Co, Ce, or La) to the 3 wt.% Ni/γ-Al<sub>2</sub>O<sub>3</sub> catalyst increased the selectivity to H<sub>2</sub> and CO with the decreasing selectivity to CO<sub>2</sub>, and the highest selectivity to H<sub>2</sub> was obtained by the 5 wt.% NiLa/γ-Al<sub>2</sub>O<sub>3</sub>. The developed 5 wt.% NiLa/γ-Al<sub>2</sub>O<sub>3</sub> catalyst showed a high stability for 30 h for the partial oxidation of methane at 750 °C. The methane conversion reached 95%, selectivity to hydrogen 83% and 52% to carbon monoxide.</p>