Preparation of Highly Active Nickel Catalysts Supported on Mesoporous Nanocrystalline γ‐Al2O3 for Methane Autothermal Reforming

Autothermal reforming (ATR) of methane was carried out over nanocrystalline Al₂O₃‐supported Ni catalysts with various Ni loadings. Mesoporous nanocrystalline γ‐Al₂O₃ powder with high specific surface area was prepared by the sol‐gel method and employed as support for the nickel catalysts. The prepared samples were characterized by X‐ray diffraction, Brunauer‐Emmett‐Teller, temperature‐programmed reduction, temperature‐programmed hydrogenation, and scanning electron microscopy techniques. It is demonstrated that the methane conversion increased with increasing in Ni content and that the catalyst with 25 wt % Ni exhibited the highest activity and a stable catalytic performance in the ATR process, with a low degree of carbon formation. Furthermore, the effects of the reaction temperature, the calcination temperature, the steam/CH₄ and O₂/CH₄ ratios, and the gas hourly space velocity on the catalytic performance of the 25 % Ni/Al₂O₃ catalyst were investigated.     

High-Performance Bimetallic Catalysts for Low-Temperature Carbon Dioxide Reforming of Methane

Catalytic dry reforming of methane (DRM) is a promising way for renewable syngas production due to the utilization of both CO₂ and CH₄ greenhouse gases. Current approaches were made to improve the catalytic activity and coke resistance by introducing a second metal into the Ni-based catalytic system. This bimetallic catalytic system showed a significant improvement in coke resistance due to the synergistic effect of both metals towards the reaction. This review summarizes recent developments in bimetallic catalysts in DRM which focused on the evaluation of catalysts, deactivation studies, and reaction mechanisms of developed bimetallic catalysts.     

CH4／CO2催化重整制合成气的研究进展

甲烷和二氧化碳反应催化重整制取合成气有效利用两种温室气体,对改善人类生存环境和缓解能源危机具有重要意义,近年来引起广泛研究者的关注。本文参阅了许多有关甲烷与二氧化碳催化重整制合成气的相关文献,概述了近年来在此研究中催化剂的选择、载体的作用、助剂的影响及催化剂积炭等方面的研究进展。     

Coprecipitated Ni‐Co Bimetallic Nanocatalysts for Methane Dry Reforming

Methane dry reforming was studied over nanostructure bimetallic Ni‐Co‐MgO catalysts. The catalysts were prepared by coprecipitation with different Ni‐Co contents and characterized by XRD, BET, N₂ adsorption/desorption, temperature‐programmed reduction (TPR), SEM, and temperature‐programmed oxidation (TPO) techniques. XRD results let conclude that all samples contained MgO crystallite phases. With a higher Ni content the intensity of the diffraction peaks became stronger, indicating growth of the crystallite size of the prepared solid solutions. BET analysis demonstrated that a higher Ni‐Co content decreased the surface area. The optimal catalyst could be determined which had the highest activity and a good stability in dry reforming reaction.     

Catalytic Performance of Coal Char for the Methane Reforming Process

A new concept of combined coal gasification and methane reforming in a single reactor was proposed as an alternative path for syngas production using coal and coalbed methane. Here, the results of this process are summarized. The experimental work was carried out in a fixed‐bed reactor. Methane cracking, CO₂/steam reforming of methane over coal char, and the effects of chars made from different types of parent coal on methane conversion were examined. The catalytic effect of coal char on methane cracking and reforming increased with decreasing coalification degree. A synergistic effect was observed in that, while the coal char catalyzed the methane reforming reactions, gasification of the coal char took place simultaneously, which counter‐balanced the deposition of carbon especially for the methane‐steam‐char system.     

Effect of the Mg/Al Atomic Ratio of Ni‐Mg‐Al Catalysts for the Hydrodealkylation of 1,2,4‐Trimethylbenzene

The hydrodealkylation of 1,2,4‐trimethylbenzene (1,2,4‐TMB) to benzene, toluene and xylenes (BTX) was investigated on Ni‐Mg‐Al catalysts prepared by the coprecipitation method. The catalytic performances of these catalysts were considerably influenced by the Mg content of the catalyst. The catalysts were characterized via X‐ray diffraction, H₂‐temperature‐programmed reduction, NH₃‐temperature‐programmed desorption (TPD), CO₂‐TPD, and Fourier transform infrared spectroscopy. The results demonstrated that the appropriate amount of Mg species significantly affected the structural properties and caused the Ni nanoparticles to become highly dispersed. The higher activity of the catalysts might be ascribed to the homogenous distribution of the Ni nanoparticles, and the synergetic effects between Ni⁰, NiAl₂O₄ and MgAl₂O₄ were the key factor for obtaining the BTX.     

Small Amounts of Rh-Promoted Ni Catalysts for Methane Reforming with CO2

Small amounts of Rh-promoted Ni/-Al₂O₃ catalysts possessed higher activity than pure Ni/-Al₂O₃, Rh-Al₂O₃ catalysts and exhibited excellent coke resistance ability in methane reforming with CO₂. XRD, H₂-TPR, CO₂-TPD and coking reaction (via CH₄ temperature-programmed decomposition) indicated that Rh improved the dispersion of Ni, retarded the sintering of Ni and increased the activation of CO₂ and CH₄ on the surface of catalyst.     

Catalytic Activity of Cu/SBA‐15 for Peroxidation of Pyridine Bearing Wastewater at Atmospheric Condition

In this study, Cu‐loaded Santa Barbara amorphous (SBA)‐15 catalysts were synthesized by impregnation method and further used for catalytic wet peroxidation (CWPO) of pyridine from aqueous solution using hydrogen peroxide as oxidant. The synthesized catalysts have been characterized by Brunauer–Emmett–Teller surface area: temperature‐programmed reduction, H₂‐chemisorption, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. Characterization results indicate good dispersion of Cu species inside the porous structure of SBA‐15. The effect of various parameters such as Cu loading on SBA‐15, pH, catalyst dose, H₂O₂ concentration, and temperature have been studied for their effect on CWPO of pyridine. More than 97% pyridine removal and 92% total organic carbon removal was achieved at optimum condition. Cu/SBA‐15 showed stable performance during reuse for six cycles with negligible copper leaching. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2577–2586, 2013     

Ni Catalyst Coating on Fecralloy® Microchanneled Foils and Testing for Methane Steam Reforming

The procedure following the washcoating of three different Ni catalyst systems (MgO, Al₂O₃, and CeO₂/Al₂O₃ supported) on pretreated Fecralloy® microchanneled foils under controlled milling times and viscosities of the slurries is described. The activity of the prepared coatings is also presented. Four different series of coated foils were prepared: one per each catalyst system, keeping constant the average particle size on 5 μm, and one extra series to study the effect of reducing the average particle size of the MgO‐supported catalyst system to 3 μm. For each coating, scanning electron microscopy pictures were taken and specific surface areas and average densities of the catalyst layers were estimated. Finally, each series of coated foils was stacked and tested in a microreactor for the methane steam reforming (MSR) reaction under different conditions.     

Synthesis of TPA impregnated SBA‐15 catalysts and their performance in polyethylene degradation reaction

Tungstophosphoric acid (TPA)‐containing mesoporous santa barbara amorphous (SBA)‐15 materials were synthesized by impregnation of TPA into hydrothermally synthesized SBA‐15. TPA was incorporated to the porous framework of silica with different W/Si ratios, using TPA hydrate as the acid source. The synthesized materials had a surface area range of 212–825 m² g^?1, depending on the TPA loading and exhibited Type IV adsorption–desorption isotherms. Energy dispersive spectrometry and X‐ray photoelectron spectroscopy (XPS) analyses showed that TPA was successfully penetrated into mesopores of the SBA‐15 material. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis of the pyridine adsorbed synthesized materials revealed the existence of Lewis and Brønsted acid sites in the synthesized materials. Their performances were tested in the degradation of polyethylene by thermogravimetric analysis. An increase in TPA content significantly lowered the degradation temperature and activation energy of the polyethylene degradation reaction. In the presence of TPA‐incorporated SBA‐15 catalyst, activation energy was reduced to approximately half‐value of the value found in the absence of the catalyst. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2466–2472, 2012     

镍盐前驱体对Ni/SBA-15催化剂上甲烷干重整反应性能的影响

研究了不同镍盐前驱体(硝酸镍、乙酸镍和氯化镍)制备的Ni/SBA-15催化剂对甲烷干重整反应催化性能的影响。与硝酸镍和氯化镍相比,以乙酸镍为前驱体制备的催化剂在不同反应温度下具有优异的催化活性,在700℃下,经过20 h连续的稳定性测试,催化剂仍表现出良好的稳定性和选择性。利用N_2吸附-脱附、XRD、XPS、H_2-TPR和TG对催化剂结构、表面物种和还原性等进行分析。结果表明,乙酸镍制备的Ni/SBA-15催化剂具有较低的NiO结晶度以及良好的分散度、优越的氧化还原性能和抗积碳性能。此外,活性组分Ni与载体SBA-15之间的相互作用有利于其良好的催化活性。     

Preparation of a LaNiO3/γ‐Al2O3 Catalyst and its Performance in Dry Reforming of Methane

LaNiO₃/γ‐Al₂O₃ catalysts containing 10, 15, 20, and 25 wt % Ni were prepared by a combination of sol gel with propionic acid as solvent and an impregnation method (LNA‐acid) as well as with ethanol as solvent and addition of acetic acid (LNA‐eth). Catalytic activities towards CO₂ reforming of CH₄ were tested in a fixed‐bed reactor at 700 °C, 750 °C, and 800 °C. LNA‐eth with 20 wt % Ni exhibited the best activities in dry reforming of methane and a good activity and stability, when it was tested at 800 °C during 75 h time‐on‐stream.     

Ni–Fe Catalysts Based on Perovskite-type Oxides for Dry Reforming of Methane to Syngas

LaNi_(1−x)Fe_xO₃ (x=0, 0.2, 0.4 and 0.7) perovskite-type catalysts were modified by the partial substitution of nickel by iron, aiming to increase the stability and resistance to carbon deposition during the methane dry reforming reaction. The results showed that a suitable combination of precipitation and calcination steps could result in oxides with the desired structure and with improved properties from the point of view of heterogeneous catalysis. The partial substitution of Ni by Fe in the perovskite structure resulted in decreasing rates of conversion of both reactants. However, the stability of the catalyst during the reaction was highly increased. These substituted catalysts were shown to be stable and the LaNi_0.8Fe_0.2O₃ catalyst, calcined at 800 °C for 5 h, was the most active in the reaction conditions.     

Conjugated linoleic acid formation by hydrogenation/isomerisation of safflower oil over bifunctional structured catalyst Rh/SBA‐15

Directed isomerisation of safflower oil under very low hydrogen partial pressure of 7 psi over a novel bifunctional highly structured rhodium‐based catalyst (Rh/SBA‐15), having narrow pore size distribution ranging from 4 to 8 nm, and BET‐specific surface of ≈1,000 m² g^?1, was investigated as a new chemocatalytic approach for vegetable oil hardening and simultaneously producing health‐beneficial conjugated linoleic acids (CLA). Time course profiles of (cis‐9, trans‐11)‐; (cis‐10, trans‐12)‐; (trans‐10, cis‐12)‐; (cis,cis)‐ and (trans, trans)‐octadecadienoic isomers (CLAs) as well as the other fatty acids traditionally encountered during the hydrogenation of vegetable oils are presented and discussed under selected process conditions. Preliminary results show that it is possible to tailor characteristics of the hydrogenation catalyst in such way to confer its bi‐functional activity: hydrogenation and conjugation isomerisation. © 2011 Canadian Society for Chemical Engineering     

Steam and Dry Reforming Processes Coupled with Partial Oxidation of Methane for CO2 Emission Reduction

CO₂ is thought to contribute to global climate change. A novel integrated process of steam methane reforming (SMR) and dry methane reforming (DMR) coupled to partial oxidation of methane (POX) has been developed that utilizes the compensating heat effects of DMR and POX and recycles a large amount of CO₂ to the DMR+POX section. Both SMR and the integrated process were simulated using Aspen Plus and were optimized to operate under their respective optimum operating conditions. Modified mitigation cost (MMC) was implemented as the evaluation method. The results demonstrate that the combined process is more efficient than the SMR process due to its reutilization of CO₂ and lower requirement of raw materials.     

Effect of Nickel Addition on Ceria‐Supported Platinum Catalysts for Medium‐Temperature Shift Reaction in Fuel Processors

Medium‐temperature shift reaction (MTS, 280–340 °C) has received much attention for use in fuel processors. In this study, bifunctional Pt‐Ni/CeO₂ catalysts were prepared by different Pt (0.1–0.5 %) and Ni (5–20 %) loadings, and investigated for MTS reaction. X‐ray diffraction, N₂ adsorption and temperature‐programmed reduction tests were used to characterize the prepared samples. The results showed that Pt‐Ni bimetallic catalysts have higher CO conversion in comparison to Pt/CeO₂ monometallic catalyst. Furthermore, the sequential synthesis method of Pt and Ni impregnation was preferred to the simultaneous one, which is due to the better Pt dispersion on catalytic surface. Steam to carbon ratio variations study showed the maximum CO conversion to be in the range of 4.5.