Hydrocracking of Tar Components from Hot Coke Oven Gas over a Ni/Ce-ZrO2/γ-Al2O3 Catalyst at Atmospheric Pressure

Ni/Ce-ZrO₂/γ-Al₂O₃ catalysts with different Ce-ZrO₂ contents and Ni loadings were prepared by a two step impregnation method and characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption, and temperature-programmed reduction. The catalysts were used for the hydrocracking of toluene and naphthalene, which were model tar compounds in hot coke oven gas, under atmospheric pressure at 800 °C. They showed excellent catalytic activity, stability, and some sulfur tolerance. Both toluene and naphthalene was converted into light fuel gases even at a low mole ratio of steam to carbon (S/C = 0.44). During the testing period of 7 h, no coke deposition was observed on the surface of the catalysts. The results indicated that the addition of Ce-ZrO₂ limited the sintering of Ni particles and enhanced the catalytic activity. The Ni/Ce-ZrO₂/γ-Al₂O₃ catalyst is promising for the direct removal of tar compounds in hot coke oven gas with low S/C ratios.     

Methane steam reforming over rhodium promoted Ni/Al2O3 catalysts

The effect of Rh addition upon catalyst characteristics and performance in methane steam reforming was investigated using Rh-promoted Ni/Al₂O₃ catalysts. The number of reduced metal atoms exposed on the surface increased for the Rh-promoted catalysts. Rh-promoted catalysts showed an increase in CH₄ reforming activity; however, constant turnover frequencies for promoted and unpromoted catalysts suggest that the increase in the number of metal surface atoms caused the activity enhancement. Rh also facilitated reduction of Ni/Al₂O₃.     

乙烷氧化脱氢用Ni/Al2O3催化剂中活性镍物种前驱体（英文）

Ni/Al2O3 catalysts for oxidative dehydrogenation(ODH) of ethane were prepared by impregnation of Al2O3 with nickel acetate or nickel nitrate,and by mechanical mixing of NiO and Al2O3.The Ni-based catalysts were characterized by N2 adsorption-desorption,X-ray diffraction,diffuse reflectance UV-visible diffuse reflectance spectroscopy,and temperature-programmed reduction of hydrogen.The results showed that formation of crystalline NiO particles with a size of < 8 nm and/or non-stoichiometric NiO species in the Ni/Al2O3 catalysts led to more active species in ODH of ethane under the investigated reaction conditions.In contrast,tetrahedral Ni species present in the catalysts led to higher selectivity for ethene.Formation of large crystalline NiO particles(22-32 nm) over Ni/Al2O3 catalysts decreased the selectivity for ethene.     

Carbon Dioxide Reforming of Methane to Synthesis Gas Over Ni/MgO-Al2O3-AlPO4 Catalysts

Carbon dioxide reforming of methane to synthesis gas was studied over Ni/MgO-Al₂O₃-AlPO₄ catalysts. The conventional Ni/Al₂O₃ and Ni/MgO-Al₂O₃ catalysts were included for comparison. These catalysts were characterized by nitrogen adsorption and hydrogen chemisorption. The results show that Ni/MgO-Al₂O₃-AlPO₄ was more active than the other two catalysts especially at high reaction temperatures. MgO-Al₂O₃-AlPO₄ has a large pore diameter with a very uniform pore size distribution. It can overcome the pore diffusion effect under high temperature reaction conditions.     

Characterization of La-promoted Ni/Al2O3 catalysts for hydrogen production from glycerol dry reforming

In the current paper, dry (CO₂)-reforming of glycerol, a new reforming route, was carried out over alumina (Al₂O₃)-supported, non-promoted and lanthanum-promoted nickel (Ni) catalysts. Both sets of catalysts were synthesized via a wet co-impregnation procedure. Physicochemical characterization of the catalysts showed that the promoted catalyst possessed smaller metal crystallite size, hence higher metal dispersion compared to the virgin Ni/Al₂O₃ catalyst. This was also corroborated by the surface images captured by the FESEM analysis. From temperature-programmed calcination analysis, the derivative weight profiles revealed two peaks, which represent a water elimination peak at a temperature range of 373 to 473 K followed by nickel nitrate decomposition from 473 to 573 K. In addition, BET surface area measurements gave 85.0 m²·g⁻¹ for the non-promoted Ni catalyst, whilst the promoted catalysts showed an average of 1% to 6% improvement depending on the La loadings. Significantly, reaction studies at 873 K showed that glycerol dry reforming successfully produced H₂. The 2%La-Ni/Al₂O₃ catalyst, which possessed the largest BET surface area, gave an optimum H₂ generation (9.70%) at a glycerol conversion of 24.5%.     

Catalytic activities of Mo-modified Ni/Al2O3 catalysts for thioetherification of mercaptans and di-olefins in fluid catalytic cracking naphtha

A series of molybdenum-modified Ni/Al₂O₃ catalysts were prepared, and their catalytic activities and stabilities for thioetherification of mercaptans and di-olefins in fluid catalytic cracking (FCC) naphtha were investigated. The sulfided catalyst samples were characterized by a range of physical techniques. The results showed that the addition of Mo to Ni catalysts could improve the degree of dispersion of Ni species in the carrier, inhibit the formation of NiAl₂O₄ crystallites, enhance the presulfidation degree of the metals, and change the chemical environment and electronic structure of Ni. These effects could significantly improve the activity of the Ni/Al₂O₃ catalysts for thioetherification in FCC naphtha. Furthermore, addition of a small amount of Mo improved the di-olefin selective hydrogenation ability of the Ni/Al₂O₃ catalyst and significantly reduced coke formation during the reaction.     

Interfacial Engineering of Ni/V2O3 Heterostructure Catalyst for Boosting Hydrogen Oxidation Reaction in Alkaline Electrolytes

Alkaline fuel cells can permit the adoption of platinum group metal-free (PGM-free) catalysts and cheap bipolar plates, thus further lowering the cost. With the exploration of PGM-free hydrogen oxidation reaction (HOR) catalysts, nickel-based compounds have been considered as the most promising HOR catalysts in alkali. Here we report an interfacial engineering through the formation of nickel-vanadium oxide (Ni/V₂O₃) heterostructures to activate Ni for efficient HOR catalysis in alkali. The strong electron transfer from Ni to V₂O₃ could modulate the electronic structure of Ni sites. The optimal Ni/V₂O₃ catalyst exhibits a high intrinsic activity of 0.038 mA cm⁻² and outstanding stability. Experimental and theoretical studies reveal that Ni/V₂O₃ interface as the active sites can enable to optimize the hydrogen and hydroxyl bindings, as well as protect metallic Ni from extensive oxidation, thus achieving the notable activity and durability.     

Steam reforming of ethylene glycol over Ni-based catalysts: the effect of K

The effect of K on the activities of Ni/Al₂O₃ catalysts in steam reforming of ethylene glycol was investigated. Ni/Al₂O₃ catalysts were prepared by incipient wetness impregnation and co-precipitation methods. The addition of K was achieved using an incipient wetness impregnation method. The prepared catalysts were characterized by N₂ physisorption, inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. Irrespective of the preparation method, the promotional effect of K was observed and the optimum K content (~5 wt%) was verified for K-promoted Ni/Al₂O₃ catalysts. The addition of K to the Ni–Al₂O₃ catalyst prepared by co-precipitation led to higher catalytic activity than addition of K to the Ni/Al₂O₃ catalyst prepared by incipient wetness impregnation.     

Synthesis of Highly-Dispersed Ni/Mesoporous Silica via an Ammonia Evaporation Method for Dry Reforming of Methane: Effect of the Ni Loadings

Mesoporous silica was used in conjunction with the ammonia evaporation method to prepare highly dispersed Ni catalysts for the dry reforming of methane (DRM). The effect of Ni dispersion on the catalytic performance was investigated by applying different Ni loadings. The pore structure, morphology, Ni dispersion, catalytic activity for DRM as well as the coke resistance were investigated. During the reaction at a relatively low temperature of 600 °C, all the three catalysts exhibited high stability in CH₄ and CO₂ conversion and excellent coke resistance, in comparison to Ni/SiO₂ catalyst prepared by the incipient wetness method. Among them, 10% Ni–SiO₂ exhibited the best catalytic performance with the maximum steady conversions of 62% and 69% for CH₄ and CO₂ at 600 °C, which was beneficial from its optimal Ni content and the presence of highly-dispersed metal nanoparticles confined in the mesopores.

     

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al_2O_3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were investigated. The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity （GHSV） and feed ratio were studied.     

Ni/Al2O3 catalysts for CO methanation: Effect of Al2O3 supports calcined at different temperatures

The correlation between phase structures and surface acidity of Al₂O₃ supports calcined at different temperatures and the catalytic performance of Ni/Al₂O₃ catalysts in the production of synthetic natural gas (SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al₂O₃ catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al₂O₃ supports were adjusted by calcining the commercial γ-Al₂O₃ at different temperatures (600–1200 °C). CO methanation reaction was carried out in the temperature range of 300–600 °C at different weight hourly space velocities (WHSV = 30000 and 120000 mL·g^?1·h^?1) and pressures (0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al₂O₃ supports due to the rapid decrease of the specific surface area and acidity of Al₂O₃ supports. Interestingly, Ni catalysts supported on Al₂O₃ calcined at 1200 °C (Ni/Al₂O₃-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al₂O₃-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures (600, 800 and 1000 °C). These findings would therefore be helpful to develop Ni/Al₂O₃ methanation catalyst for SNG production.     

Carbon Dioxide Reforming of Methane over Ni Catalysts Supported on Al2O3 Modified with La2O3, MgO, and CaO

The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present review mainly focuses on CDR to produce synthesis gas over Ni/MO_x/Al₂O₃ (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La₂O₃, MgO, and CaO have been found. The addition of promoters to Al₂O₃-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent on the loading amount of promoters. For example, the highest CH₄ and CO₂ conversion were obtained when the ratios of metal M to Al were in the range of 0.04–0.06. In the case of Ni/La₂O₃/Al₂O₃ catalyst, the highest CH₄ conversion (96%) and CO₂ conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al₂O₃ catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH₄ conversion (91%) and CO₂ conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al₂O₃ catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH₄ conversion (89%) and CO₂ conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic performance of Al₂O₃-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization of metal oxide on Al₂O₃ and the basic property of metal oxide to prevent carbon formation.     

沸石负载Ni催化剂在甲烷干重整中的稳定性(英文)

Ni/γ-Al2O3 , Ni/Y-zeolite, and Ni/H-ZSM-5 catalysts were prepared using the incipient wetness impregnation method. Their catalytic performance in dry reforming of methane was studied. The fresh and used catalysts and deposited carbon were characterized using H2 temperature-programmed reduction, temperature-programmed oxidation, N2 adsorption-desorption, X-ray diffraction, and thermogravimetric analysis. The H-ZSM-5-supported Ni catalyst proved to be more stable than the other two catalysts, as it had the lowest carbon deposition.     

Dry reforming of methane over Ni/Ce0.62Zr0.38O2 catalysts: Effect of Ni loading on the catalytic activity and on H2/CO production

The activity of ceria–zirconia-supported nickel catalysts (Ni/CZ) with various loadings of nickel (2, 4 and 10 wt. %) was studied in the case of low-temperature dry reforming of methane (DRM). XRD, S_BET, SEM, TPD-CO₂ and thermogravimetry were used to determine the physicochemical properties of the catalysts and of the carbon deposits formed on the surface. It was found that the agglomerates of the Ni-active phase are formed on the surface of the support for high loadings of nickel. The best conversions of CO₂ and CH₄ and an optimum ratio H₂/CO = 1 were obtained for the catalysts with the highest Ni content. It was also found that loading has an influence on the amount of carbon deposits formed in the DRM process.     

Untersuchungen zur temperaturprogrammierten Reduktion und zur katalytischen Wirksamkeit von Ni/Al2O3

Investigations of Temperature-programmed Reduction and of Catalytic Activity of Ni/Al₂O₃ Different Ni/γ-Al₂O₃ catalysts were prepared by varying the Ni content and the temperature of the thermal pretreatment. These samples were investigated by the TPR technique and by the catalytic conversion of cyclohexane. Two species of oxidized Ni were formed during the calcination, easily reducible “bulk” NiO and heavily reducible “fixed” NiO. The proportion of fixed NiO increases with increasing calcination temperature and with decreasing Ni content. The selectivity of the cyclohexane conversion is shifted from hydrogenolytic methane formation towards dehydrogenating benzene formation by catalysts containing increasing amounts of fixed NiO. This shift is explained by an ensemble effect.     

不同载体Ni基负载型催化剂对甲烷部分氧化制合成气催化行为研究

采用浸渍法制备了单一载体(Al₂O₃、ZrO₂、CeO₂)和ZrO₂、CeO₂改性的Al₂O₃复合载体的Ni催化剂,考察了在甲烷部分氧化制备合成气反应中的催化性能。通过N₂-物理吸附、H₂程序升温还原、X射线衍射、NH₃程序升温脱附和程序升温氧化等技术对催化剂进行了表征。结果表明,在单一载体催化剂中,Ni/Al₂O₃具有较大的比表面积,其初始反应活性较高,但该催化剂表面易形成大量的积炭而快速失活。Ni/ZrO₂和Ni/CeO₂催化剂比表面积较小,活性金属Ni在其表面分散性差,催化剂具有较低的CH₄转化率。而CeO₂和ZrO₂改性的Al₂O₃复合载体催化剂,具有较大的比表面积,反应活性明显高于单一载体催化剂。CeO₂-Al₂O₃复合载体催化剂具有最高的反应活性和较好的反应稳定性。同时表明,含CeO₂催化剂反应后表面积炭较少,CeO₂的储放氧功能增强了催化剂对O₂的活化,提高催化剂活性的同时,可以抑制积炭的生成。     

State of Ni in catalysts for glycerol hydrogenation and methane steam reforming as studied by X-ray absorption spectroscopy

X-ray absorption spectroscopy is used to study 1% Ni/Al₂O₃, 5% Ni/Al₂O₃, and 5% Ni/TiO₂ catalysts for glycerol and methane conversion. The effect of treatment in H₂ under microwave irradiation on the reduction of part of the nickel to the metallic state in the titanium oxide-supported catalyst is demonstrated.     

Promotion effect of additive Fe on Al2O3 supported Ni catalyst for CO2 methanation

In this paper, the effect of additive Fe on Ni/Al₂O₃ catalyst for CO₂ methanation was studied. A series of bimetallic Ni–Fe catalysts with different Ni/Fe ratios were prepared by impregnation method. For comparison, monometallic Fe‐based and Ni‐based catalysts were also prepared by the same method. The characterization results showed that adding Fe to Ni catalyst on the premise of a low Ni loading(≦12 wt.%) enhanced CO₂ methanation performance. However, when the Ni loading reached 12 wt.%, the catalytic activity decreased with the increase of Fe content, but still higher than the corresponding Ni‐based catalyst without Fe. Among them, the 12Ni3Fe catalyst exhibited the highest CO₂ conversion of 84.3 % and nearly 100% CH₄ selectivity at 50000 ml g^‐1 h^‐1 and 420 °C. The enhancement effect of adding Fe on CO₂ methanation was attributed to the dual effect of suitable electronic environment and increased reducibility generated by Fe species.     

Autothermal Reforming of Methane over Ni Catalysts Supported on CuO-ZrO2-CeO2-Al2O3

Ni catalysts supported on various mixed oxides of Al2O3 with rare earth oxide and transitional metal oxides were synthesized. The studies focused on the measurement of the autothermal reforming of methane to hydrogen over Ni catalysts supported on the mixed oxide ZrxCe30-xAl70Oδ (x=5, 10, 15). The catalytic performance of Ni/Zr10Ce20Al70Oδ was better than that of other catalysts. XRD results showed that the addition of Zr to Ni/Ce30Al70Oδ prevented the formation of NiAl2O4 and facilitated the dispersion of NiO. Effects of CuO addition to Zr10Ce20Al70Oδ were also investigated. The activity of Ni catalyst supported on CuO-ZrO2-CeO2-Al2O3 was somewhat affected and the Ni/Cu5Zr10Ce20Al65Oδ showed the best catalytic performance with the highest CH4 conversion, yield of H2, selectivity for H2 and H2/CO production ratio in operation temperatures ranging from 650 to 750℃.     

Understanding the Origin of Highly Selective CO2 Electroreduction to CO on Ni,N-doped Carbon Catalysts

Ni,N-doped carbon catalysts have shown promising catalytic performance for CO₂ electroreduction (CO₂R) to CO; this activity has often been attributed to the presence of nitrogen-coordinated, single Ni atom active sites. However, experimentally confirming Ni−N bonding and correlating CO₂ reduction (CO₂R) activity to these species has remained a fundamental challenge. We synthesized polyacrylonitrile-derived Ni,N-doped carbon electrocatalysts (Ni-PACN) with a range of pyrolysis temperatures and Ni loadings and correlated their electrochemical activity with extensive physiochemical characterization to rigorously address the origin of activity in these materials. We found that the CO₂R to CO partial current density increased with increased Ni content before plateauing at 2 wt % which suggests a dispersed Ni active site. These dispersed active sites were investigated by hard and soft X-ray spectroscopy, which revealed that pyrrolic nitrogen ligands selectively bind Ni atoms in a distorted square-planar geometry that strongly resembles the active sites of molecular metal–porphyrin catalysts.