NiCe/γ-Al 2 O 3 coated onto cordierite monoliths applied to Oxidative Dehydrogenation of Ethane (ODE)

Modeling and experimental analysis of CO2 methanation reaction using Ni/CeO2 monolithic catalyst

In this study, the effect of the cell density of monolithic catalysts was investigated and further mathematically modeled on cordierite supports used in CO2 methanation. Commercial cordierite monoliths with 200, 400, and 500 cpsi cell densities were coated by immersion into an ethanolic suspension of Ni/CeO2 active phase. SEM-EDS analysis confirmed that, owing to the low porosity of cordierite (surface area < 1 m2 g-1), the Ni/CeO2 diffusion into the walls was limited, especially in the case of low and intermediate cell density monoliths; thus, active phase was predominantly loaded onto the channels' external surface. Nevertheless, despite the larger exposed surface area in the monolith with high cell density, which would allow for better distribution and accessibility of Ni/CeO2, its higher macro-pore volume resulted in some introduction of the active phase into the walls. As a result, the catalytic evaluation showed that it was more influenced by increments in volumetric flow rates. The low cell density monolith displayed diffusional control at flow rates below 500 mL min-1. In contrast, intermediate and high cell density monoliths presented this behavior up to 300 mL min-1. These findings suggest that the interaction reactants-catalyst is considerably more affected by a forced non-uniform flow when increasing the injection rate. This condition reduced the transport of reactants and products within the catalyst channels and, in turn, increased the minimum temperature required for the reaction. Moreover, a slight diminution of selectivity to CH4 was observed and ascribed to the possible formation of hot spots that activate the reverse water-gas shift reaction. Finally, a mathematical model based on fundamental momentum and mass transfer equations coupled with the kinetics of CO2 methanation was successfully derived and solved to analyze the fluid dynamics of the monolithic support. The results showed a radial profile with maximum fluid velocity located at the center of the channel. A reactive zone close to the inlet was obtained, and maximum methane production (4.5 mol m-3) throughout the monolith was attained at 350 °C. Then, linear streamlines of the chemical species were developed along the channel.

Phase-pure M1 MoVNbTeOx/TiO2 nanocomposite catalysts: high catalytic performance for oxidative dehydrogenation of ethane

The introduction of TiO2 can improve the catalytic performance of phase-pure M1 MoVNbTeOx in the ODHE process, in which the STY enhancement of M1/40TiO2 at 400 °C and W/F = 7.55 gcat h molC2H6−1 reached ∼76%.

Unravelling the redox mechanism and kinetics of a highly active and selective Ni-based material for the oxidative dehydrogenation of ethane

Bridging the gap between catalysis and reaction engineering during the kinetic analysis of the oxidative dehydrogenation of ethane over a highly active and selective Ni-based material.

Effect of reduction temperature on the structure and catalytic performance of mesoporous Ni–Fe–Al2O3 in oxidative dehydrogenation of ethane

The effects of reduction temperature on the structure and catalytic performance of mesoporous Ni–Fe–Al₂O₃ are investigated for the first time.

Present state of the art of and outlook on oxidative dehydrogenation of ethane: catalysts and mechanisms

Oxidative dehydrogenation of alkanes is a more appropriate approach than other conventional methods of light olefin production. Recently, several researchers have focused on more economical and cleaner processes because of the high demand for olefins and environmental problems. This paper reviews a series of catalysts for the oxidative dehydrogenation of ethane, including transition-metal oxides, rare earth metal oxides, calcium oxide, supported alkali chlorides, molecular sieves, as well as monolithic, perovskite, and carbon catalysts. Also, a detailed literature review is presented for the comparison of effective parameters such as acid-base property, redox property, oxidant types, and oxygen species. Mechanisms proposed for the oxidative dehydrogenation of ethane are also presented. Recommendations for future researches are also discussed based on catalyst design, promotors, and reaction conditions.

FeCrAlloy Monoliths Coated with Ni/Al2O3 Applied to the Low-Temperature Production of Ethylene

This paper investigates the oxidative dehydrogenation of ethane to produce ethylene at low temperatures (500 °C) in metallic structured substrates. To check this point, the FeCrAlloy® monoliths with different channel sizes (289–2360 cpsi) were prepared. The monoliths were coated with a Ni/Al2O3 catalyst (by washcoating of alumina and the latter nickel impregnation) and characterized by Scanning Electron Microscopy and Energy-Dispersive X-ray analysis (SEM-EDX), Temperature-Programmed Reduction (TPR), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The catalytic results showed that all monoliths coated with ~300 mg of catalyst presented similar ethane conversion (15%) at 450 °C. However, the lowest selectivity to ethylene was found for the monolith with the lower channel size and the higher geometric surface area, where a heterogeneous catalyst layer with Ni enriched islands was generated. Therefore, it can be said that the selectivity to ethylene is linked to the distribution of Ni species on the support (alumina). Nevertheless, in all cases the selectivity was high (above 70%). On the other hand, the stability in reaction tests of one of the coated monoliths was done. This structured catalyst proved to be more stable under reaction conditions than the powder catalyst, with an initial slight drop in the first 8 h but after that, constant activity for the 152 h left.

Anion insertion enhanced electrodeposition of robust metal hydroxide/oxide electrodes for oxygen evolution

Electrochemical deposition is a facile strategy to prepare functional materials but suffers from limitation in thin films and uncontrollable interface engineering. Here we report a universal electrosynthesis of metal hydroxides/oxides on varied substrates via reduction of oxyacid anions. On graphitic substrates, we find that the insertion of nitrate ion in graphene layers significantly enhances the electrodeposit–support interface, resulting in high mass loading and super hydrophilic/aerophobic properties. For the electrocatalytic oxygen evolution reaction, the nanocrystalline cerium dioxide and amorphous nickel hydroxide co-electrodeposited on graphite exhibits low overpotential (177 mV@10 mA cm⁻²) and sustains long-term durability (over 300 h) at a large current density of 1000 mA cm⁻². In situ Raman and operando X-ray diffraction unravel that the integration of cerium promotes the formation of electrocatalytically active gamma-phase nickel oxyhydroxide with exposed (003) facets. Therefore, combining anion intercalation with cathodic electrodeposition allows building robust electrodes with high electrochemical performance.

Electrodeposition provides a facile fabrication means for electrochemical devices but weak substrate-deposit interactions cause poor performance. Here, authors utilize anion insertion within graphitic layers to improve the material interfaces and construct highly active O₂-evolving electrocatalysts.