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The chemical looping oxidative dehydrogenation (CL‐ODH) of ethane represents a highly effective approach for converting ethane into the value‐added product ethylene. This investigation focused on the synthesis of SrMnO3 and its halide ions doped derivatives (SrMnO3Cl and SrMnO3Br) through the sol‐gel method. The performance of these perovskites, employed as oxygen carriers in CL‐ODH of ethane, was explored. The results unveiled several advantageous outcomes arising from the incorporation of halide ions (Cl− and Br−) with larger radius into the oxygen sites of the SrMnO3 perovskite. Halide ions doping notably induced cell volume expansion and enhanced lattice fringe spacing. Furthermore, it contributed to elevated oxygen vacancy concentration, increased Mn4+/Mn3+ molar ratio, and improved oxygen ions mobility within the bulk lattice. Fixed‐bed experiments demonstrated that these redox catalysts, doped with halide ions, exhibited outstanding activity and stability during cycling tests, exhibiting enhanced both ethylene selectivity and yield in CL‐ODH of ethane. In summary, the introduction of halide ions into SrMnO3 emerges as a promising strategy for enhancing the performance of CL‐ODH in ethane conversion for SrMnO3 based oxygen carriers. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The support properties can be tuned through changing the addition amount of Zr. As a result, the formation and stability of Co species can be regulated, then, the relationships between different Co species and reaction pathways have been revealed. [Display omitted] TiO 2 , ZrO 2 and a series of TiO 2 -ZrO 2 (TxZ1, x means the atomic ratio of Ti/Zr = 10, 5, 1, 0.2 and 0.1) composite oxide supports were prepared through co-precipitation, and then 3 wt% Co was loaded through wetness impregnation methods. The obtained 3 wt% Co/TiO 2 (3CT), 3 wt% Co/ZrO 2 (3CZ) and 3 wt% Co/TxZ1 (3CTxZ1) catalysts were evaluated for the oxidative ethane dehydrogenation reaction with CO 2 (CO 2 -ODHE) as a soft oxidant. 3CT1Z1 catalyst exhibits excellent catalytic properties, with C 2 H 4 yield, C 2 H 6 conversion and CO 2 conversion about 24.5 %, 33.8 % and 18.0 % at 650 °C, respectively. X-Ray Diffraction (XRD), in-situ Raman, UV–vis diffuse reflectance spectra (UV–vis DRS), H 2 temperature-programmed reduction (H 2 -TPR), Electron paramagnetic resonance (EPR) and quasi in-situ X-ray Photoelectron Spectroscopy (XPS) have been utilized to thoroughly characterize the investigated catalysts. The results revealed that 3CT1Z1 produced TiZrO 4 solid solution with more metal defect sites and oxygen vacancies (Ov), promoting the formation of Co2+-TiZrO 4 structure. Furthermore, the presence of Ov and Ti3+can facilitate the high dispersion and stabilization of Co2+, as well as suppressing the severe reduction of Co2+, leading to superior ethane oxidative dehydrogenation activity. Besides, less Co0 is beneficial to ODHE reaction, because of its promotion effects for reverse water gas shift reaction; however, more Co0 results in dry reforming reaction (DRE). This work will shed new lights for the design and preparation of highly efficient catalysts for ethylene production. [ABSTRACT FROM AUTHOR]

Ni‐M‐O catalysts have demonstrated superior performance in the oxidative dehydrogenation of ethane (ODHE), but precise control over the content of active oxygen species is necessary to achieve optimal C2H4 selectivity. In this work, highly efficient Ni‐Al‐O catalysts were prepared by a plasma‐assisted strategy, and their catalytic properties were evaluated for ODHE reaction. Characterization results revealed that the working atmospheres (O2, H2 and Ar) can not only change the crystallite size of NiO, but also modulate the reduction properties of Ni‐Al‐O catalysts and the distribution of active oxygen species. Consequently, Ar and O2 plasma pretreatment increased the ODHE performance by increasing active surface oxygen, while H2 plasma‐treated catalyst showed a decrease in the catalytic performance compared to the original Ni‐Al‐O catalyst. Among them, O2‐Ni‐Al‐O exhibited 50.8 % ethane conversion and 70.3 % ethylene selectivity at 500 °C. It was accepted that the change in the ratio of defective oxygen to lattice oxygen (OV/OL) was the internal reason to illustrate its excellent performance. For series Ni‐Al‐O catalysts, C2H6 conversion increased linearly while C2H4 selectivity decreased with an increase in OV/OL value. [ABSTRACT FROM AUTHOR]

[Display omitted] • Relationship between ODH of ethane and electrochemical properties. • Optimal catalyst with Nb in the lattice and on the surface is n -type semiconductor. • Relationship between density of non-stoichiometric oxygen and selectivity to C 2 =. • Relationship between electrochemical properties and selectivity to C 2 =. In the present article, a relationship between the catalytic performance in the oxidative dehydrogenation of ethane (ODHE) for Nb-doped NiO catalysts and their electrochemical properties has been proposed. To do so, highly stable and selective Nb-doped NiO catalysts for the ODHE to ethylene have been synthesized by optimizing synthesis parameters such as the amount of oxalic acid in the synthesis gel and the calcination temperature. These catalysts have been characterized by means of XRD, HRTEM, Raman and UV–vis diffuse reflectance spectroscopies, TPR and XPS. Moreover, Electrochemical Impedance Spectroscopy (EIS), capacitance measurements (Mott-Schottky analysis) and cyclic voltammetries studies were also carried out. Electrochemical characterization indicates changes in the type of semiconductivity: p -type for samples calcined at 350 °C and the sample prepared in the absence of oxalic acid and calcined at 500 °C, to n -type for samples prepared in the presence of oxalic acid in the synthesis gel and calcined at 500 °C. According to the obtained results, the most selective catalysts present a low Nb-incorporation on the NiO lattice with a large amount of tiny Nb 2 O 5 nanoparticles covering NiO crystallites. This work presents, for the first time, a complete electrochemical characterization of Nb-doped NiO catalysts showing a correlation between electrochemical properties and catalytic performance. [ABSTRACT FROM AUTHOR]

Ethylene is mainly produced by steam cracking of naphtha or light alkanes in the current petrochemical industry. However, the high-temperature operation results in high energy demands, high cost of gas separation, and huge CO2 emissions. With the growth of the verified shale gas reserves, oxidative dehydrogenation of ethane (ODHE) becomes a promising process to convert ethane from underutilized shale gas reserves to ethylene at a moderate reaction temperature. Among the catalysts for ODHE, MoVNbTeOx mixed oxide has exhibited superior catalytic performance in terms of ethane conversion, ethylene selectivity, and/or yield. Accordingly, the process design is compact, and the economic evaluation is more favorable in comparison to the mature steam cracking processes. This paper aims to provide a state-of-the-art review on the application of MoVNbTeOx catalysts in the ODHE process, involving the origin of MoVNbTeOx, (post-) treatment of the catalyst, material characterization, reaction mechanism, and evaluation as well as the reactor design, providing a comprehensive overview of M1 MoVNbTeOx catalysts for the oxidative dehydrogenation of ethane, thus contributing to the understanding and development of the ODHE process based on MoVNbTeOx catalysts. [ABSTRACT FROM AUTHOR]

The effect of gadolinium additives on the morphology, phase composition, and catalytic properties of MoVSbNbGdOx/SiO2 catalysts in the oxidative dehydrogenation of ethane to ethylene (ODE) is studied. It is shown that gadolinium concentration has a significant effect on the catalytic properties. At an optimum gadolinium content (Gd/Mo = 0.01–0.015), an increase in catalytic activity and ethylene selectivity is observed: at a temperature of 400°C, the ethylene yield achieves 72%, the ethane conversion is higher than 91%, and the ethylene selectivity is higher than 79%. According to X-ray diffraction analysis and scanning and transmission electron microscopy, the main component of the catalyst is the M1 phase stabilized both in the bulk and on the surface of SiO2 particles. The modification of the catalyst with gadolinium significantly affects the morphology of the M1 phase particles. At an optimum gadolinium content, heat treatment leads to the formation mostly of M1 phase particles with a needle-like morphology and the most developed [001] plane emerging on the surface, which exhibit the maximally high activity in ODE. The M1 phase particles with this morphology are mostly stabilized in the bulk of porous spherical SiO2 particles; therefore, they do not undergo strong agglomeration and sintering. A smaller portion of the M1 phase particles with a plate-like morphology, which exhibit a lower catalytic activity, as well as the M2 phase particles, are stabilized on the outer surface of the SiO2 particles. In the catalyst containing no Gd additives, M1 phase particles with a plate-like morphology are mostly formed; this factor leads to a decrease in the catalyst activity. The synthesized catalyst exhibits a long-term stable on-stream behavior in the reaction medium without a deterioration of the properties. [ABSTRACT FROM AUTHOR]

Boron and nitrogen co-doped carbon nanospheres (B X CN) were fabricated using graphitic carbon nitride (g-C 3 N 4) as the precursor and the nitrogen source, and boric acid as the boron source. They featured high specific surface area and porous structure. Besides, the doping of B brought improved chemical and thermal stability of the material. They were further used as catalysts for the oxidative dehydrogenation of ethane (ODHE) for the first time. The B X CN demonstrated higher conversion of ethane and higher selectivity towards ethylene, compared with other carbon catalysts such as carbon nanotubes reported in literature. An ethane conversion of 15.8% with a selectivity of 56.0% towards ethylene were achieved on B 0 · 1 CN at a reaction temperature of 525 °C. The B 0 · 1 CN showed an excellent stability within 7 h ODHE test at 450 °C. This work offers a new strategy of using heteroatoms co-doped carbon-based catalysts with improved activity for ODHE under lower temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]

The oxidative dehydrogenation of ethane (ODHE) to ethylene is a process with many advantages (such as energy conservation and coke resistance). Herein, flower‐like Ni−Al−O catalysts with hierarchical structure and high surface areas were fabricated through a hydrothermal route and were applied to ODHE using O2 as oxidant. Compared with NiO alone, the Al3+ insertion into NiO matrix not only increases the C2H4 selectivity by 3–4 times, but also prevents the generation of CO2 and CH4 above 500 °C. At 550 °C, all Ni−Al−O catalysts maintain approximately 50 % ethylene selectivity regardless of Al content. The ethylene yield of 29.5 % with C2H4 selectivity 55.7 % over Ni−Al0.8‐O sample can be reached at 500 °C. Moreover, the Ni−Al0.8‐O catalyst presents a good stability and has no loss of activity after 100 h continuous evaluation. The various characterizations were carried out for investigating the nature of as‐prepared Ni−Al−O catalysts with different Al loadings. Experimental results demonstrate that the addition of Al not only affects the structure and texture properties of NiO, but also impacts the reducibility of Ni species and the amount of active oxygen species. It is found that the Al3+ substitution results in: (1) smaller NiO size; (2) larger specific surface area; (3) weaker reducibility and (4) fewer non‐stoichiometric oxygen species. Therefore, the significant improvement of ethylene selectivity is observed in Ni−Alx‐O catalysts. [ABSTRACT FROM AUTHOR]

The oxidative dehydrogenation of ethane in the presence of CO2 was studied on SiO2-supported chromium oxide catalytic systems with different texture characteristics. The highest activity was displayed by the samples deposited on SiO2 with a high specific surface area. On the 5%CrОх/SiO2 catalyst, the ethylene selectivity was ~80% at ~50% conversion of ethane. The results of our physicochemical analysis showed that the catalyst activity depended on the content of Cr(VI) particles, whose formation depended on the nature of support. [ABSTRACT FROM AUTHOR]

Ethylene is mainly produced by steam cracking of naphtha or light alkanes in the current petrochemical industry. However, the high-temperature operation results in high energy demands, high cost of gas separation, and huge CO2 emissions. With the growth of the verified shale gas reserves, oxidative dehydrogenation of ethane (ODHE) becomes a promising process to convert ethane from underutilized shale gas reserves to ethylene at a moderate reaction temperature. Among the catalysts for ODHE, MoVNbTeOx mixed oxide has exhibited superior catalytic performance in terms of ethane conversion, ethylene selectivity, and/or yield. Accordingly, the process design is compact, and the economic evaluation is more favorable in comparison to the mature steam cracking processes. This paper aims to provide a state-of-the-art review on the application of MoVNbTeOx catalysts in the ODHE process, involving the origin of MoVNbTeOx, (post-) treatment of the catalyst, material characterization, reaction mechanism, and evaluation as well as the reactor design, providing a comprehensive overview of M1 MoVNbTeOx catalysts for the oxidative dehydrogenation of ethane, thus contributing to the understanding and development of the ODHE process based on MoVNbTeOx catalysts.

Sodium-tungsten-manganese supported on silica (Na-W-Mn/SiO2) and hydroxyapatite (HAp) are representative catalysts for oxidative coupling of methane (OCM). In this work, the effect of the HAp doping in a Na-W-Mn/SiO2 catalysts on the OCM performance was studied. To enhance the ethylene selectivity of the Na-W-Mn/SiO2 catalyst, silica supports were coated with HAp containing hydroxyl and phosphate groups as oxygen species. A series of Na-W-Mn/xHAp_SiO2 (x=1, 3, 5 and 7) catalysts with the different HAp coating cycles were prepared through the alternative soaking method, and X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that the amount of HAp doping was dependent on the HAp coating cycles. In addition, the change of oxygen species upon HAp doping was examined with X-ray photoelectron spectroscopy (XPS) and oxygen temperature-programmed desorption (O2-TPD) techniques. With HAp doping, the increase of oxygen species assigned to metal oxide responsible for selective oxidation of methane to ethylene was observed in O 1s XPS spectra. In addition, weakly bound oxygen species were observed with the introduction of HAp doping in O2-TPD profiles of prepared catalysts. The influence of these oxygen species on OCM catalytic performance was evaluated at an operating temperature of 775 °C and gas hourly space velocity of 18,000 ml/gcat·h. The amount of HAp doping provided reactive oxygen species for oxidative dehydrogenation of ethane, which resulted in as much as 120% increase in C2H4/C2H6 ratio over the Na-W-Mn/3HAp_SiO2 catalyst compared to the Na-W-Mn/SiO2 catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • HYSYS study predicted ethylene ODH yields with new diluents & process technology. • Additional storage for ODH reactor resulted in less downtime & process failures. • An upgrade to improve ethylene ODH profitability could use shale gas as a diluent. A HYSYS simulator was utilized to predict the performance of an ethylene oxidative dehydrogenation (ODH) production facility using alternative diluents and separation technology not currently used in the standard industrial process. An ODH process system was modeled with ethane being fed along with air into a reactor with simultaneous mixing with pure methane to lower the product gas temperature. The methane feed was later separated from the other product gases and eventually fed into a recycle stream. This process was fairly expensive due to the use of a demethanizer within the process recycle stream. Safety and operational improvements for the ODH process was another aspect of this analysis that yielded interesting results. By the inclusion of storage vessels before and after the ODH reactor, the reactor unit can operate even in the event of an upstream or downstream failure, resulting in less downtime for the process. [ABSTRACT FROM AUTHOR]

A multicomponent MoVSbNbCeOx/SiO2 oxide catalyst exhibiting high catalytic activity in the oxidative dehydrogenation of ethane to ethylene is synthesized by spray drying of a suspension of aqueous solutions of the precursors and the subsequent heat treatment in He at 350 and 600°C. At a temperature of 400–450°С in a wide ethane conversion range, the catalyst exhibits a fairly high activity and ethylene selectivity. In the presence of this catalyst, the maximum ethylene yield achieves 74% (ethane conversion of 91%, ethylene selectivity of 81.5%); this value significantly exceeds the yield in the presence of Sb-containing catalysts known from the literature. The catalyst exhibits a long-term stable on-stream behavior under reaction medium conditions without any change in the phase composition and a deterioration of the catalytic characteristics. It is shown that the catalytic properties of the synthesized catalyst are comparable to the properties of MoVTeNbOx, which is one of the best catalysts for this process. However, the use of a Te-containing catalyst is limited, because tellurium exhibits a high toxicity and volatility during the synthesis and use of the catalysts. According to X-ray diffraction analysis, the main components of the catalyst are M1 and M2 phases stabilized on a SiO2 surface. The HRTEM data show that a structural feature of the catalyst is the presence of an interface formed by the coherently intergrown crystals of the M1 and M2 phases. [ABSTRACT FROM AUTHOR]

• The MoVTeNbO catalysts for ODE were modified by Nd, Ge, Ga, Mn additives. • Additives influence on phase composition, surface acidity and elements distribution. • Modification enhances an ethylene space time yield by the factor of ∼1.5. • There is correlation between catalytic activity in ODE and amount of M1 phase. Modification by Nd, Mn, Ga, and Ge substantially affect both physicochemical and catalytic properties of MoVNbTeO oxides in the oxidative dehydrogenation of ethane (ODE). The introduction of modifying additives changes the content of the M1 phase, surface acidity, and surface composition. It does not have an influence on the state of Mo, V, Nb, and Te on catalyst surface, but it induces surface enrichment (Ga, Mn) or depletion (Ge, Nd) by the modifying element. All of these additives have positive effects on catalytic properties at the M/Mo (M = modifying element) ratio of 0.0075 ÷ 0.025. They exhibit an increase of activity and prevent ethylene over-oxidation. The relationship between the rate constant of total ethane transformation and the M1 content confirms that this phase is active in ODE. The correlation between ethylene selectivity and the relative number of intermediate acid sites is revealed, indicating the role of surface acidity on ethylene over-oxidation. [ABSTRACT FROM AUTHOR]

• Bi-modified MoVNbTeO catalysts possess enhanced tolerance toward severe reaction conditions during ODE process. • Incorporated bismuth influences on Te mobility within 6-membered channels of M1 structure. • The improved stability and activity of MoVNbTeO catalysts relates to enhanced Te surface concentration. This work presents the investigation of Bi-modified MoVNbTeO catalysts for oxidative dehydrogenation of ethane (ODE) using the combination of NAP-XPS, in situ XRD and XANES/EXAFS techniques. It was found that introduction of Bi improves the tolerance of catalysts toward severe reaction conditions (high temperature and/or enhanced ethane/oxygen ratio) resulting in a significant decrease in the degree of deactivation. In accordance with NAP-XPS data, the surface/subsurface Te concentration was maintained for Bi-containing MoVNbTeO catalysts even after treatment with a reducing reaction mixture (C 2 H 6 /O 2 >3) at temperatures up to 460 °C. In the case of the unmodified catalyst, such treatment resulted in the surface/subsurface depletion of Te due to the reduction into the Te° state followed by its sublimation into the gas phase. The incorporation of Bi within extended six-membered channels of the M1 structure was suggested based on XANES/EXAFS data. Such incorporation probably influences the mobility of Te within channels, resulting in the limitation of Te diffusion from the particle bulk to the surface. The improved tolerance of catalytically active M1 phase toward severe reaction conditions was confirmed by in situ XRD data during heating in a mixture of 8 wt % C 2 H 6 /He. [ABSTRACT FROM AUTHOR]

Highlights • ODHE was studied in a cobalt-free dual-phase OTM reactor. • Ethylene selectivity in membrane mode was enhanced compared to co-feed mode. • High ethylene yield over 60% was obtained at 725 °C. • CGO-BFMC shows good chemical stability and catalytic performance for ODHE. Abstract In this work, the oxidative dehydrogenation of ethane (ODHE) was investigated in a cobalt-free dual-phase membrane Ce 0.9 Gd 0.1 O 2-δ - BaFe 0.9 Mg 0.05 Ce 0.05 O 3-δ (CGO-BFMC) with good chemical stability and catalytic performance. Two operation modes were taken to compare the catalytic performance of CGO-BFMC membrane for ODHE. Compared to the co-feed mode with gaseous oxygen, the selectivity and yield of ethylene in membrane mode were significantly enhanced by 18% and 15%, respectively, which probably benefits from the continuous supply of selective oxygen species via oxygen transporting membrane. An ethylene yield of 63% was obtained at 725 °C, which was steadily operated in lab for over 200 h. No obvious decline in selectivity and yield of ethylene was observed, and the spent membrane was still dense after 200 h of operation. [ABSTRACT FROM AUTHOR]

Highlights • Improved performance of MoVNbTeO x catalyst in ODH process by inserting oxygen into catalyst lattice through manganese ions. • Revealed the phase-pure M1 catalyst properties before and after the introduction of MnO x. • Proposed an inference of oxygen diffusion process during preparation by detailed characterization and controlled trial Abstract M1 phase of MoVNbTe oxide catalyst is a promising catalyst for oxidative dehydrogenation of ethane (ODHE) process. Raising V5+ concentration in the catalyst is an effective way to improve the catalytic performance while thermal oxidation in air has limited effect on the increase of vanadium valence state. In this work, manganese is introduced into the catalyst system, acting as oxygen facilitator, making M1 oxidized by gas phase oxygen at lower temperature during the preparation process. The influence of manganese addition amount and combination method on catalyst activity is studied. BET, XPS, SEM, TEM, ICP, TPR, and TPD characterizations are performed to study the correlation between catalyst properties and catalytic performance. Corresponding to the valence state increment, the catalyst promoted by MnO x gives an improved catalytic performance, e.g. , over 20% improvement in ODHE process at 400 °C based on the ethane conversion. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Sorbents exhibit better cyclic performance of ∼ 0.6 g/g in CO 2 in-situ capture and conversion condition. • Sorbent prepared by sol–gel method has the excellent performance with 0.41 g/g and 0.58 g/g. • The spinel catalyst was first reported in the in-situ CO 2 capture and conversion. • The CO 2 uptake capacity and ethylene yield can increase with the decrease of content of sorbent in DFM. • The critical mechanism of in-situ CO 2 capture and conversion was summarized. The coupling technology (CaLODHE) of calcium looping (CaL) and oxidative dehydrogenation of ethane (ODHE) has recently attracted numerous attentions. However, the optimization of the CaO-based sorbent in CaLODHE has not been extensively reported to date. In this work, a comparative study of the CO 2 capture performances of the CaO-based sorbents by different synthesis methods (i.e., dry-mixing, wet-mixing, sol–gel, and coprecipitation) tested in CaL and CaLODHE conditions was conducted. The results show that the sorbent by the sol–gel method in CaLODHE condition has the highest cyclic capture performances of around 0.6 g/g during 20 cycles, attributed to the porous structure and homogeneously dispersed CeO 2. In addition, the dual functional material (DFM) with CaO-based sorbent and MgGaAlO 4 catalyst was first synthesized and the performances of DFM with different mixing ratios of sorbent and catalyst were investigated. The results show that the DFM with the sorbent and catalyst of the same quality has a balanced performance, and the CO 2 uptake capacity and conversion are 0.27 g/g and 57%, and the ethane conversion and ethylene selectivity are 56.9% and 74.2%, respectively. In addition, the reaction mechanism of CaLODHE was also proposed in depth. [ABSTRACT FROM AUTHOR]

• Impact of the axial effective thermal conductivity (k eff,z) on hot spots prediction. • Adequate characterization of k eff,z from adiabatic experimental conditions. • Considering k eff,z is crucial to avoid runaway mispredictions. • Evaluation of the Oxidative Dehydrogenation of Ethane industrial reactor model. The impact of axial conductive heat transfer on the simulation and prediction of hot spots and, more particularly, runaway, within an industrial-scale wall-cooled packed-bed reactor with low tube-to-particle diameter ratio (d t /d p ∼ 3) has been assessed in this work. To this purpose, the effective axial conductivity (k eff,z) was first determined from adiabatic experiments in a bench-scale packed bed in the absence of reaction. Next, non-adiabatic and non-isothermal bench-scale and industrial-scale packed bed experimental data were used in the assessment of the impact of axial heat conduction on the prediction of the temperature profile. The so-called Pseudo-local Internal Heat Transfer Approach (PL-IHTA) was used for the adequate description of the radial temperature gradients. Finally, an industrial-scale wall-cooled packed bed reactor for the highly exothermic catalytic oxidative dehydrogenation of ethane was modeled to assess the impact of the axial thermal conductivity on temperature profile simulations. When disregarding axial heat conduction or adopting literature-based values for k eff,z , determined from either experiments at low d t /d p ratios (<8) and Re p ≤ 1000 or high d t /d p ratios (>8) and Re p ≤ 700 at a wide panel of operating configurations, runaway is simulated at conditions where it has not been observed experimentally or a negligible hot-spot prediction is obtained. When considering the k eff,z determined for the specific reactor configuration in this work, hot spots are predicted at Re p of 700 and 1400, but no runaway. The discrepancies between experimental findings and temperature profiles simulated using literature-based values for k eff,z indicate the need for a specific determination of k eff,z in packed bed reactors with low d t /d p ratio to more accurately predict hot spots, resulting in more reliable reactor design and operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanisms of C 2 H 6 oxidation and C 2 H 4 production on sIrO2(1 1 0) were revealed. • Diffusion kinetics is critical to properly understand the simulated TPRS spectra. • The results provide further insights into controlling the reactivity of metal oxides to increase the selectivity. The catalytic oxidative dehydrogenation of alkane can be an attractive way to produce olefines from light alkanes which are major components of natural gas. This study examined C 2 H 6 oxidation on a stochiometric IrO 2 (1 1 0) surface, which has a high potential to produce C 2 H 4 production at a low temperature of ∼ 400 K using density functional theory calculation and microkinetic simulation. The DFT simulation predicted two main complete oxidation mechanisms of dehydrogenation-based oxidation and C 2 H x O formation-based oxidation. With DFT-derived energetic data, microkinetic simulation for C 2 H 6 oxidation was performed on stochiometric IrO 2 (1 1 0) TPRS spectra. The simulation confirmed that C 2 H 6 oxidation during TPRS mainly follows the dehydrogenation-based complete oxidations (C 2 H 6 → C 2 H 5 → C 2 H 4 → C 2 H 3 → C 2 H 2 → C 2 H → C 2 → C 2 O → CO + C). In addition, the production of C 2 H 4 (g) stems from the cooperative steps of C H bond recombination from C 2 H 3 and subsequent desorption. The computational findings cannot be produced without the proposed concept of a surface diffusion-limited reaction, which can resolve the errors of overestimated rates by the mean field approach. This finding suggests that the diffusion kinetics can be critical for understanding the TPRS features when simulating TPRS spectra by mean field-based microkinetic simulation. Our results provide a solid understanding of C 2 H 6 oxidation and C 2 H 4 production mechanisms on sIrO 2 (1 1 0). [ABSTRACT FROM AUTHOR]

From macro- to nano-engineering of a promising CeO 2 -ZrO 2 -doped NiO-Al 2 O 3 /Ni-foam catalyst has been demonstrated for the oxidative dehydrogenation of ethane to ethylene (ODE), through facial wet chemical etching of a Ni-foam followed post modification with CeO 2 and ZrO 2 . The NiO-Al 2 O 3 /Ni-foam (denoted as NANF) achieved a high ethane conversion of 25.2% but with a very low ethylene selectivity of 43.1% at 450 °C. ZrO 2 -doping of the NANF led to a remarkable improvement in the ethylene selectivity but serious deterioration of activity while the CeO 2 -doping showed an opposite effect. Co-doping of the NANF using optimal amount of CeO 2 and ZrO 2 markedly promoted not only the activity but also the selectivity to ethylene. For example, over the 1CeO 2 -5ZrO 2 -NANF (CeO 2 :1 wt%, ZrO 2 :5 wt%) catalyst, a high ethane conversion of 40.3% was obtained with a 60.6% ethylene selectivity for a feed gas of C 2 H 6 /O 2 /N 2 = 1/1/8 at 500 °C and a gas hourly space velocity of 18,000 cm 3 g −1 h −1 , corresponding to a high ethylene productivity of 510 g Ethylene kg cat −1 h −1 . In nature, co-doping with CeO 2 and ZrO 2 synergistically tamed the NiO for selective H-abstraction of the ethane molecules other than over oxidation of them. [ABSTRACT FROM AUTHOR]

Unmodified and sulfate-modified SBA-15-supported CrO catalysts were prepared by impregnation method. The physico-chemical properties of the supports and catalysts were determined by nitrogen adsorption/desorption, powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), laser-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (UV-DRS), inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR) techniques. Oxidative dehydrogenation of ethane to ethylene (ODE) with CO as oxidant was carried out on these catalysts in a fixed-bed reactor at temperatures in the range of 600-700 °C and at atmospheric pressure. The changes in structural and textural properties because of sulfate modification were identified. Sulfate modification affected the nature of interaction of CrO species with the SBA-15 support. During the evaluation, it was observed that sulfate modification enhances ethane conversion and ethylene selectivity of the catalyst. Better dispersion of CrO and the increase in Cr/Cr ratio seem to be the reasons for the higher performance of the sulfate-modified catalysts compared to that of the unmodified catalyst. [ABSTRACT FROM AUTHOR]

• Alkali and alkaline earth perovskites have similar active sites for OCM and ODHE. • Moderate and strong basic sites assist OCM and moderate basic sites expedite ODHE. • V f affects CH 4 , C 2 H 6 , and O 2 conversions, while χ A + χ B affects basicity. • Crystal phase transition and metal-oxygen energy alter moderate basic sites. • Moderate V f , low electronegativity, and variable crystal phase augment reactivity. In this study, alkali metal and alkaline earth metal perovskites have been synthesized using simple preparation methods for catalyzing the oxidative coupling of methane (OCM) and oxidative dehydrogenation of ethane (ODHE). The influence of their structural parameters (such as tolerance factor t, unit cell free volume (V f), electronegativity of A- and B-site elements, average metal-oxygen energy, and crystalline phase transition) on basic sites and reaction performance is also systematically investigated. The results show that these two perovskites have similar active sites for OCM and ODHE reactions, with the moderate and strong basic sites favoring the OCM reaction and the moderate basic site facilitating the ODHE reaction. The surface basicity of these perovskites reflects the electron-donating ability of lattice oxygen, which in turn affects the production of reactive oxygen species (O 2 −, O 2 2−, and O−). Moderate basic sites are abundant and closely related to oxygen vacancies, with high oxygen vacancy concentrations generating abundant reactive oxygen species. Meanwhile, V f values of perovskites govern the CH 4 , C 2 H 6 , and O 2 conversions, the electronegativity of elements affects the catalyst basicity, and the average metal-oxygen energy and crystalline phase transition alter the moderate basic sites. Overall, it concludes that perovskites should meet the following conditions to achieve excellent catalytic performance for OCM and ODHE: moderate V f , low electronegativity of A- and B-site elements, low average metal oxygen energy, and a crystalline structure that changes with temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

MoVO, MoVTeO and MoVTeNbO mixed oxides, prepared hydrothermally and heat-treated in N 2 at 400, 500 or 600 °C, are active and selective catalysts in the oxidative dehydrogenation (ODH) of ethane, although their catalytic behaviour strongly depends on the composition and the activation temperature of the material. Thus, the selectivity to ethylene over samples heat-treated at 400 or 600 °C, decreases according to the following trend: MoVTeNb-600 > MoV-400 > MoVTe-600 > MoVTe-400 > MoVTeNb-400 >> MoV-600 (with catalysts heat-treated at 500 °C presenting an intermediate performance). This catalytic performance can be explained to a high extent by the presence of the M1 phase in the best catalysts. Interestingly, the temperature of formation and decomposition of the M1 phase strongly depends on the chemical composition of the catalysts, leading to different trends depending on the heat-treatment temperature. Not only the presence of the M1 phase determines the catalytic performance but also the V4+/V5+ ratio in the surface of catalysts. Additionally, a comprehensive brand-new electrochemical characterization of the catalysts has been carried out for MoV-based samples with M1 phase. Accordingly, the best catalytic behaviour in terms of selectivity to ethylene in the ethane ODH was observed in those materials presenting higher charge-transfer resistances at the interfacial active parts and n -type semiconductivity with few O-vacancies. Besides, lower current densities obtained in cyclic voltammetries (related to low electrochemical activity) has been associated with higher selectivity in the ODH reaction. [Display omitted] • Comparison of different MoVO, MoVTeO and MoVTeNbO M1 phase catalysts in ethane ODH. • The M1 crystalline phase is key to obtain good selectivity to ethylene in ethane ODH. • Catalytic performance optimized by the higher presence of surface V4+ species. • Correlations between electrochemical and catalytic properties in M1-based materials. [ABSTRACT FROM AUTHOR]

The incorporation of hydrodynamics in an industrial wall-cooled packed bed reactor model is essential to describe the performance of highly exothermic oxidation reactions. Although the conventional hydrodynamic approach (CHA), Navier-Stokes equations coupled to Darcy-Forchheimer terms, has been the most used approximation to describe velocity profiles in these packed bed reactors, it is itself inconsistent and the computation time for its numerical solution, when coupled to the reactor model, is still demanding. This work is aimed at developing a practical but reliable hydrodynamic approach (PHA) to describe velocity profiles in packed bed reactors presenting a low tube to particle diameter ratio. In this approach, velocity profiles are described at the core and close to the wall of the reactor. The core model makes use of the Darcy-Forchheimer equation (DFE), and the wall model makes use of Navier-Stokes equations (NSE) using an effective viscosity to account for turbulence. The PHA predicts similar results to those obtained by the CHA and properly fits velocity observations from packed beds with a tube to particle diameter ratio (d t /d p ) ranging from 3 to 6. The PHA allows the estimation of both turbulent viscosity (μ t ) involved in the viscous term of the NSE and parameters influencing viscous (α) and inertial (β) flow resistances in Darcy and Forchheimer terms, respectively. Then, hydrodynamics is coupled to a heat transport model accounting for conductive anisotropy to fit temperature observations in absence of reaction from a pilot-scale packed bed reactor with a d t /d p = 3.048. Hydrodynamics and heat transfer results are, then, transferred to a pseudo heterogeneous reactor model to simulate the behavior of a novel technology to perform the oxidative dehydrogenation of ethane on a multimetallic MoVNbTeO formulation. This is the first study modeling this reactor system accounting for hydrodynamics, information that is essential for its conceptual design in future studies. Finally, it is worth stressing that the PHA, coupled to the heat transport model or the reactor model, leads to significantly lower computation times than the CHA, which is attributed to the analytical rather than numerical solution of the former. [ABSTRACT FROM AUTHOR]

A one-dimensional non-isothermal steady state model was developed to simulate the performance of three-reactor configurations for the oxidative dehydrogenation of ethane (ODHE) to ethylene. These configurations consist of side feeding reactor (SFR), conventional fixed bed reactor (CFBR) and membrane reactor (MR). The performance of these reactors was compared in the terms of CH conversion, CH and CO selectivity and temperature profiles. The use of sectional air injections on the wall of SFR with a limited number of injection points showed that the performance of reactor significantly improves and optimum pattern of oxygen consumption is also obtained. Moreover, our SFR with a liquid coolant medium operates in an effectively controlled temperature profile that is comparable with that of the MR, which is cooled by a coolant stream of air. Hence, an enhancement in the level of selectivity is obtained for the SFR configuration. Consequently, the side feeding procedure can decrease the high operating temperature problem and low ethylene selectivity in the ODHE process. According to obtained results, the SFR would be a proper alternative for both the MR and CFBR. [ABSTRACT FROM AUTHOR]

The oxidative dehydrogenation of ethane (ODE) into ethylene over a Mo-V-Nb-Te-O mixedoxide catalyst in a cyclic mode with alternate feeding of ethane and air has been investigated. The amount of oxide-phase oxygen involved in the reaction has been estimated by titrating the oxygen of the active phase of the catalyst with ethane. The reactivity of this oxygen increases with an increasing temperature. The amount active oxygen involved in ODE at 360-400°C is 0.2-0.6 mmol/g. [ABSTRACT FROM AUTHOR]

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.

The template-induced mesoporous Ni–Al oxide catalysts synthesized by a template-assisted self-assembly route show the good mobility of selective oxygen species and tuned physico-chemical properties, thus promoting their catalytic performance and stability for the oxidative dehydrogenation of ethane using O 2 as an oxidant. [Display omitted] • Template-induced mesoporous Ni–Al mixed oxides are successfully prepared. • Structural effect and strong interaction are crucial to enhance ODHE performance. • Template-induced mesoporous Ni–Al mixed oxides exhibit preferable ODHE performance. • Adding template significantly enhances coking resistance. • Ni–Al–F127 catalyst shows a C 2 H 4 yield of 37.3 % and prominent stability for 150 h. Oxidative dehydrogenation of ethane is a potential industrial process to produce ethylene. In this work, the template-induced mesoporous Ni–Al mixed oxide catalysts synthesized by the template-assisted self-assembly method were investigated for the oxidative dehydrogenation of ethane to ethylene using O 2 as an oxidant. The template-induced structure evolution is an effective means to modulate physico-chemical properties of the Ni–Al mixed oxide, thus, it further improves the catalytic performance. All the mesoporous Ni–Al–template catalysts present higher C 2 H 6 conversions and C 2 H 4 selectivities than bulk NiO and non-porous Ni–Al–O catalysts in the temperature range of 350–500 °C. Meanwhile, up to 49.6% C 2 H 6 conversion and 75.3% C 2 H 4 selectivity (37.3% of C 2 H 4 yield) can be obtained over Ni–Al–F127 catalyst at 500 °C. And the mesoporous Ni–Al–F127 catalyst exhibits a superior stability after a long run. The structure–performance correlation indicates that the remarkable catalytic performance is ascribed to the synthesis driven structural effect. The strong interaction between Ni and Al cations caused by the addition of template promotes the formation of small NiO particles and the better dispersion of NiO, which decreases the content of non-selective oxygen species and increases the availability of lattice oxygen. [ABSTRACT FROM AUTHOR]

Flexible structured catalysts based on Ni and Zr deposited on a ceramic paper made of SiO 2 -Al 2 O 3 and ZrO 2 fibers showed to be active and selective for the Oxidative Dehydrogenation of Ethane. Zirconium promoter strongly interacted with nickel oxide and produced structural changes that affected the NiO redox behavior, crystal growth and lattice order which enhanced selectivity towards ethylene. The variation of the concentration of the precursor solution used and the addition of zirconia short fibers, affected the catalytic performance. The lower the concentration of the solution used to incorporate the catalyst, the better the catalytic performance. The addition of zirconia fibers also showed beneficial effects on ethylene production. [ABSTRACT FROM AUTHOR]

The present work investigates the preparation of NiCe/γ-Al 2 O 3 coated cordierite monoliths for oxidative dehydrogenation of ethane (ODE) reaction through a two steps procedure: the primer deposition of a γ-Al 2 O 3 coating consisting in a mixture of micro and nanoparticles via the washcoating method and the latter incorporation of the active phase by impregnation. Moreover, a modification in these two steps was made: the suppression of some calcination steps to save energy in the manufacture process. The structured catalysts, named as Ni(X)Ce(Y)-M, where X = 13 or 19 wt%. Ni and Y = 5 or 8 wt%. Ce respectively, with respect to the alumina loading, were characterized by SEM/EDX, XRD, FTIR, LRS and XPS, and their catalytic activity was tested in the ODE reaction. Furthermore, their mechanical resistance to vibration was studied. Similar results corresponding to the un-promoted system are also presented for comparison. It was found that the co-impregnation of nickel and cerium was affected by the suppression of some calcinations: a preferential absorption of Ce rather than Ni occurred, generating at the end a catalytic coating with a higher Ce/Ni ratio than that of the precursor solution and a lower Ni loading than that of Ni(13)-M. On the other side, in the NiCe-based catalysts the properties of the active sites remained the same despite the increment in the active phase, at a fixed Ce/Ni nominal atomic ratio of 0.17. In the case of the Ni(19)Ce(8)-M system, although the Ni/Al atomic ratios were found lower than those of the nominal ones by EDX and XPS and ethylene selectivity decayed, ethane conversion resulted markedly higher, leading to an improved ethylene yield. [ABSTRACT FROM AUTHOR]

The operational stability of a mixed oxide catalyst of Mo-V-Te-Nb-O composition in the oxidative dehydrogenation of ethane (ratio of CH: O = 3: 1) is studied in a flow reactor at temperatures of 340-400°C, a pressure of 1 atm, and a WHSV of the feed mixture of 800 h. It is found that the selectivity toward ethylene is 98% at 340°C, but the conversion of ethane at this temperature is only 6%; when the temperature is raised to 400°C, the conversion of ethane is increased to 37%, while the selectivity toward ethylene is reduced to 85%. Using physical and chemical means (XPS, SEM), it is found that the lack of oxidant in the reaction mixture leads to irreversible changes in the catalyst, i.e., reduced selectivity and activity. Raising the reaction temperature to 400°C allows the reduction of tellurium by ethane, from the +6 oxidation state to the zerovalent state, with its subsequent sublimation and the destruction of the catalytically active and selective phase; in its characteristics, the catalyst becomes similar to the Mo-V-Nb-O system containing no tellurium. [ABSTRACT FROM AUTHOR]

The morphology, crystal structure, and phase composition of MoVTeNbO catalysts modified with K, Ca, Zr, or Bi were studied, and the effects of promoters on their catalytic properties in the oxidative conversion reaction of ethane were examined. With the use of high-resolution transmission electron microscopy (HRTEM), it was found that Bi and K were inserted into the structure of the active phase M1 and potassium changed its morphology. Zr and Ca formed individual oxides and molybdates. Changes in the structure of the promoted models affected their catalytic properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ni and Ni–Ce/Al2O3 coatings on metallic foams were active and selective for the ODE. [•] The cerium addition increased considerably the ethylene productivity. [•] Catalytic features of the structured systems depend on the calcination temperature. [•] The presence of chromium in the catalytic coatings mainly affects the selectivity. [•] The structured systems showed higher ethylene productivity than powder catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Ni and Ni–Ce oxides alumina-supported formulations onto alpha-alumina foams were prepared, characterized and evaluated in the oxidative dehydrogenation of ethane (ODE) reaction. The catalysts were appropriately deposited on ceramic foams with a uniform, mechanically stable coverage. Besides, the structured systems were active and selective in the ODE reaction, demonstrating that the incorporation method was successful to obtain adequate active sites. Cerium markedly improved the ethane conversion due to a synergistic effect with nickel oxide, thus leading to a significant increment in ethylene productivity compared to that of the cerium-free system. An optimal Ce/Ni ratio was found which maximized the catalytic performance. [Copyright &y& Elsevier]

It is shown that catalytic activity of mixed oxide catalyst of Mo-V-Te-Nb-O composition in oxidative dehydrogenation (OD) of ethane is determined to a substantial degree by the Nb-to-(CO) ratio in niobium-containing precursors. A pH value of 2.8 to 3.0 for a mixture is optimal when conducting the hydrothermal synthesis of a mixed oxide catalyst; this is achieved by using oxaloniobic acid as a niobium-containing precursor. It is determined that substituting antimony for tellurium results in a loss of catalyst activity during the OD of ethane. The optimum Te content in a catalyst is 0.17 mol %. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel catalytic papers were prepared for oxidative dehydrogenation of ethane. [•] The papers present an interconnected network structure with fibers covered by alumina. [•] The systems exhibit NiO as active phase and show high activity for ODE. [•] Catalytic paper with Ce/Ni=0.17 atomic ratio showed the highest productivity. [ABSTRACT FROM AUTHOR]

An intensification process for the selective oxidation of hydrocarbons integrates a catalytic reactor and an oxygen separation membrane. This work presents the study of oxidative dehydrogenation of ethane at 1123 K in a catalytic membrane reactor based on mixed ionic-electronic conducting (MIEC) membranes. The surface of a membrane made of Ba0.5Sr0.5Co0.8Fe0.2O3− δ has been activated using different porous catalytic layers based on rare earth-doped cerias (fluorite structure) and the porous catalytic coating was deposited by screen printing (coating around 15 μm). The different catalyst formulations were developed by partial substitution of Ce and were synthesized by co-precipitation followed by cobalt impregnation when required. Specifically, seven different catalysts based on the system Ce1− xLn xO2− δ ( x=0.1 or 0.2; Ln=Tb, Pr, Er, Gd, and Tb+Er), including the effect of cobalt addition (2 % molar) in Ce0.8Tb0.2O2− δ, were studied. The ceria catalysts were studied by XRD, SEM, DC-conductivity as a function of oxygen partial pressure, and the high-temperature stability in a CO2 environment was assessed using thermogravimetry. Then, the influence of the ceria catalytic coating on the oxygen permeation flux through the MIEC membrane was studied using argon and methane as the sweep gas in the permeate side. Finally, oxidative dehydrogenation of ethane reaction tests were performed at 1123 K, as a function of the ethane concentration in the feed. The use of a disk-shaped membrane in the reactor made it possible to prevent the direct contact of gaseous oxygen and hydrocarbons and thus to increase the ethylene yield. High ethylene yields (up to ≈84 %) were obtained using a catalytic coating based on 20 % Tb-doped ceria including macropores produced by the addition of graphite platelets in the screen printing ink. The high yields obtained in this kind of catalytic membrane are attributed to the combination of: the high catalytic activity; the control of the oxygen concentration in the gas phase (reaction chamber); and the appropriate fluid dynamics, enabling the fast ethylene evacuation. [ABSTRACT FROM AUTHOR]

Abstract: MoVTe(Sb)NbO catalysts have been prepared using the slurry method and tested as catalysts for the oxidative dehydrogenation of ethane. The influence of both the addition of silica to the starting slurry during the preparation and of a final heat treatment under nitrogen at 873K after the dissolution of the M2 phase formed concomitantly to the active M1 active phase has been studied. While the parameters change the texture of the catalysts without modification of the catalytic sites, they have opposite effects on catalytic properties. The addition of silica increases the conversion without modifying the selectivity to ethylene and the final heat treatment decreases the conversion but increases the selectivity. These effects have been explained respectively by a decrease of the agglomeration and sintering of the M1 phase crystallites and a decrease of the number of small pores, where total oxidation takes place. These effects could be leveraged to optimize the preparation protocol and obtain more efficient catalysts for the oxidative dehydrogenation of ethane. [Copyright &y& Elsevier]

Abstract: In this paper we present the synthesis, characterization and catalytic behaviour in the oxidative dehydrogenation of ethane of NiO–CeO2 mixed oxides. The addition of cerium oxide to NiO strongly modifies its catalytic performance, although the changes in the catalytic behaviour depend on the catalyst composition. The incorporation of low amounts of cerium oxide to NiO multiplies the productivity to ethylene in the oxidative dehydrogenation of ethane by a factor of ca. 7, which is the result of an increase in both catalytic activity and selectivity to ethylene. The enhanced activity has been related to the remarkable increase of the surface area of catalyst and the low crystal sizes of NiO that takes place when a tiny amount of cerium oxide is incorporated to the NiO. The higher selectivity to ethylene has been related to the modification of the nature of Ni–O species, which implies a lower production of carbon oxides. On the other hand, high activity and selectivity is also observed over catalysts rich in cerium (with Ni/Ce ratios between 0.2 and 3). In this case, a different mechanism can be proposed in which the high capacity of CeO2 to bomb oxygen from bulk to surface and the partial formation of NiO and Ce1−x Ni x O2 facilitates a faster reoxidation of active Ni-sites by a synergic effect improving catalytic activity. [Copyright &y& Elsevier]

Li/MgO is one of the most frequently investigated catalysts for the oxidative coupling of methane. Besides catalytic testing, it is also a suitable system to perform surface science experiments and quantum chemical calculations, which is not possible for many other active catalysts. However, the real structure of Li/MgO, the nature of the active center and the structure - activity relationship remain unclear, despite all the research that has been done. The aim of this review is to summarize the available knowledge on Li/MgO to structure and accelerate and improve the ongoing work on this catalytic system. [ABSTRACT FROM AUTHOR]

Abstract: Ni–W–O mixed oxides were prepared through the evaporation of aqueous solutions of nickel nitrate and ammonium tungstate and calcined in air at 500°C for 2h. The catalysts were characterized by several techniques (N2 adsorption, X-ray diffraction, temperature-programmed reduction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy of adsorbed CO, and 18O/16O isotope exchange) and tested in the oxidative dehydrogenation of ethane. The catalytic activity and catalyst reducibility decrease when the W content increases. Thus, nickel sites seem to be the active centers for ethane activation in these catalysts. However, the selectivity to ethylene strongly changes depending on the Ni/W ratio. In W-rich catalysts, in which NiWO4 and WO3 are mainly observed, a strong influence of ethane conversion on the selectivity to ethylene is observed. However, in Ni-rich catalysts, in which NiO crystallites and WO x nanoparticles are mainly observed, ethane conversion hardly influences the selectivity to ethylene. It has been demonstrated that the nature of the Ni sites and the characteristics and number of the acid sites determine the catalytic behavior of these catalysts. The presence of Lewis acid sites with high acid strength in W-rich catalysts facilitates the decomposition of ethylene during ethane oxidation. [Copyright &y& Elsevier]

Abstract: Gamma-alumina-supported MoO x , MoVO x (Mo/V=11) and MoVPO x (Mo/V=11, V/P=1) catalysts were prepared and their properties studied by several techniques (EDX-SEM, XRD, XPS, LRS, TPR). Acid–base and catalytic properties were determined by carrying out 2-propanol decomposition and oxidative dehydrogenation of ethane to ethene, respectively. In situ X-ray diffraction and X-ray photoelectron spectroscopy after pre-treatment were carried out in redox conditions (with H2/N2, C2H6/N2 as reducing and O2/N2 as oxidant). The catalytic performance increases along MoO x