Unit Mass Of Catalyst Research Articles

Characteristic analysis and kinetics description for biochar-based catalysts coking during the biomass catalytic pyrolysis

Coke formation is one of the major obstacles in the development of catalytic pyrolysis of biomass. The experiments were carried out on poplar wood chips using the biochar-based catalysts (poplar biochar: ZSM-5 = 1:2) to study the coke formation characteristics of biochar-based catalysts and to develop the kinetic models of coke formation. It is shown that the high temperature and long reaction time promoted the conversion of carbon from amorphous coke to graphitized coke. The higher the degree of graphitization of the coke, the higher the combustion temperature and the richer the cyclized structure. Activated coke and neutral coke were gradually converted to inert coke per unit mass of catalyst. Based on the experimental data, combined AIC evaluation system, it is found that the MMCGM (monolayer-multilayer coke growth model) can only describe the coke formation at low temperature well. Therefore, the kinetic model of carbon particle stacking model was established. This model can well describe the coke formation process on biochar-based catalysts. This study is expected to provide a guide for understanding the characteristics of catalyst coke formation and optimizing pyrolysis conditions and reactors.

Fe–Ni–Ce–Zr-modified CuO–ZnO catalyst for methanol steam reforming

Four copper-based catalysts were prepared by co-precipitation method. The catalysts were characterized by scanning electron microscopy, N2 adsorption-desorption, temperature programmed reduction process (H2-TPR), X-ray diffraction (XRD) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) to explore the effects of different components on catalyst activity. The performance of different catalysts for hydrogen production via methanol steam reforming was evaluated on a fixed-bed reactor. The effects of different components, reaction temperature and gas hourly space velocity (GHSV) on the catalytic performance were investigated. The results exhibited that among the investigated catalysts, 1# and 2# catalysts had the higher catalytic activity and stability. Under the conditions of 280 °C, a molar ratio of methanol to water of 1:1.3, and a GHSV of 13.3 L/(g·h), the methanol conversion rate reached 99.9%, the CO concentration was as low as 0.29%, and the selectivity was only 1.16%. The H2 production flow rate per unit mass of catalyst was 270 mL/(min·g). After 60 h of start-stop experiments, the methanol conversion rate remained above 98.4%, the CO concentration was always lower than 0.5%, and the start-up speed was significantly faster than that of the commercial catalyst M650. This study provided an effective method for the preparation of catalysts for methanol steam reforming.

Machine learning-assisted crystal engineering of a zeolite

It is shown that Machine Learning (ML) algorithms can usefully capture the effect of crystallization composition and conditions (inputs) on key microstructural characteristics (outputs) of faujasite type zeolites (structure types FAU, EMT, and their intergrowths), which are widely used zeolite catalysts and adsorbents. The utility of ML (in particular, Geometric Harmonics) toward learning input-output relationships of interest is demonstrated, and a comparison with Neural Networks and Gaussian Process Regression, as alternative approaches, is provided. Through ML, synthesis conditions were identified to enhance the Si/Al ratio of high purity FAU zeolite to the hitherto highest level (i.e., Si/Al = 3.5) achieved via direct (not seeded), and organic structure-directing-agent-free synthesis from sodium aluminosilicate sols. The analysis of the ML algorithms’ results offers the insight that reduced Na2O content is key to formulating FAU materials with high Si/Al ratio. An acid catalyst prepared by partial ion exchange of the high-Si/Al-ratio FAU (Si/Al = 3.5) exhibits improved proton reactivity (as well as specific activity, per unit mass of catalyst) in propane cracking and dehydrogenation compared to the catalyst prepared from the previously reported highest Si/Al ratio (Si/Al = 2.8).

Electrochemical Reduction of Nitrates on CoO Nanoclusters‐Functionalized Graphene with Highest Mass Activity and Nearly 100% Selectivity to Ammonia

AbstractNO3− is a prominent waste byproduct in ammunition industries, and valorization of NO3− into NH3 is desired. NH3 synthesized from waste using renewable energy could be used as an energy storage medium. For such a process, higher selectivity, stability, and enhanced activity per unit mass of catalyst is required. This work reports CoO nanoclusters functionalized on graphene as an efficient catalyst for electrochemical NO3− reduction to NH3 with >98% NH3 Faradaic efficiency and an NH3 current density (geometric) of ≈400 mA cm−2. A highest NH3 yield of 25.63 mol g−1 h−1 is obtained. The developed catalyst prevents the NN coupling step which is required for promoting the selectivity of NH3 over N2. Density functional theory calculations reveal that CoO NC/graphene has similar selectivity to that of polycrystalline Co and that higher activity can be obtained with lower catalyst loading.

Computational fluid dynamics study on hydrodeoxygenation of pyrolytic bio-oil model compound, guaiacol, in fluidized bed reactor

Bio-oil is a reliable renewable alternative to petroleum for wide range of applications such as transportation fuels, power generation and source of many value-added chemicals for petrochemical industry. However, compared to petroleum, the physical and chemical properties of bio-oil such as high oxygen content, high moisture content and low pH are some limiting factors for its real-life applications. Thus, requires upgrading to improve its quality and catalytic hydrodeoxygenation (HDO) is one of the best available bio-oil upgrading techniques. Further, bio-oil is a complex mixture of various organic compounds such as acids, ketones, aldehydes, esters, acids and many phenolic compounds thus difficult to study as a whole mixture. Accordingly, it is often followed by researchers to select a model compound under a given compound catalogue for HDO study; and the same is followed in this work by selecting guaiacol of phenolic catalogue. This HDO study in a fluidized bed reactor has been carried out using computational fluid dynamics (CFD) based solver, ANSYS Fluent 14.5. The operating conditions includes bio-oil mass rate per unit mass of catalyst (WHSV) ​= ​1, 3 and 5 h−1; fluidizing medium velocity (u) ​= ​0.075, 0.15 and 0.25 ​m/s; catalyst load ​= ​0.06 ​kg and temperature (T) ​= ​548, 573, and 598 ​K. From the results, it is understood that the phenol is a primary product with approximately 66% while the cyclopentanone (≈22%) and methanol (≈11%) are other products. The cyclopentanone production by HDO of guaiacol is favourable at high temperature whereas low temperature conditions favour production of methanol and phenol by HDO of guaiacol.

Magnetic Properties of Efficient Catalysts Based on La‐Doped Ceria‐Supported Nickel Nanoparticles for rWGS Reaction. Influence of Ni Loading

AbstractThe influence of Ni loading on Ce0.9La0.1O1.95‐supported Ni catalysts for CO2 reduction with hydrogen (reverse water gas shift reaction) is studied. The samples are prepared by solution combustion synthesis (SCS), leading to materials with high thermal resistance, purity, and crystallinity, consisting of metallic nickel nanoparticles supported on La‐doped ceria. The study of the ferromagnetic Curie temperature (TC) and magnetization cycles suggest that the Ni nanoparticles are superparamagnetic, exhibiting magnetic order at room temperature, with TC strongly dependent on the particle size; this spans from 1.9, up to 80 nm. The structural study from synchrotron X‐ray diffraction data and Raman spectroscopy clearly show the presence of oxygen vacancies in the fluorite crystal structure of the Ce0.9La0.1O2−δ matrix, which increase in the spent catalysts by forming a greater proportion of Ce3+ compared with their fresh counterparts. This is confirmed from the Raman spectra, showing an increase in the relative intensity of the band placed between 520 and 610 cm−1. All the catalysts show very high reaction rate per unit mass of catalyst; the CO2 conversion after 6 h for the catalyst with 10% Ni molar (Ni0.1/Ce0.9La0.1) is 57% (2.4 moles CO·h−1·g catalyst−1), very close to the thermodynamic equilibrium (59.3%).

The role of sulfur sinks and micro-structured supports on the performance of sulfur-sensitive non-PGM catalysts

The presence of traces of sulfur dioxide (i.e. 1–10 ppmV) alongside residual methane emissions induces the rapid deactivation of typical methane abatement catalysts. As a result, sulfur-induced poisoning is the main challenge faced by after-treatment technologies for residual methane abatement. The aim of this study was to synthesise a series of cobalt and molybdenum catalysts and assess their performance under realistic after-treatment conditions. The series of catalysts was characterised by BET, XRD, XPS, TPR, TGA under air flow, SEM, EDX and in situ DRIFTS. In addition, the performance of Co100 supported on an alumina hollow fibre was assessed under similar reaction conditions and characterised by SEM and EDX. It was found that the catalytic activity of the series of cobalt and molybdenum catalysts decreased in the following order: Co100 > Co80Mo20 > Co60Mo40. In addition, it was discovered that the other two catalysts (i.e. Co25Mo75 and Mo100) were inactive at 450 °C due to the lack of highly active Co3+ species. Among the active catalysts, Co100 and Co80Mo20 experienced an initial activation followed by a gradual deactivation whereas Co60Mo40 experienced a 1 h interval with stable methane conversion levels in between the activation and deactivation. The delay in poisoning of the active cobalt (II,III) oxide phase of Co60Mo40 was attributed to the sulfur sink-properties of the cobalt molybdenum oxide present in this catalyst (i.e. 44 wt%). Finally, Co100 supported on an alumina hollow fibre achieved the highest methane conversion per unit mass of catalyst and its performance was stable for a duration of 2.5 h. The high activity was attributed to the large surface area provided by the geometry of the support while the higher resistance to sulfur poisoning was credited to the sulfur sink-properties of the alumina, which delayed the poisoning of the active phase.

Decoupling the relative rate of hydrogen uptake via convection and mass transfer by a single catalytic pellet in a scaled down trickle bed reactor

Heterogenous hydrogenations of high value chemicals are a widely used class of reaction that potentially benefit from the advantages continuous processing possesses. Trickle bed reactors offer a viable alternative to batch manufacture, however further understanding of the interplay between hydrogen mass transfer and catalytic reaction is required to facilitate the uptake of such technologies.To isolate the transport processes, the hydrogenation of styrene was conducted with a single 1% palladium on carbon pellet immobilized within glass beads with a liquid feed either hydrogen saturated or hydrogen free and the liquid flow rate was varied. The transfer rate of hydrogen was found to be significantly affected by the hydrogen content in the feed. The observations are well described by a new model in which the pellet film is treated as a plug flow reactor, with mass transfer from the gas phase to the film modelled as diffusion through a stagnant film, and mass transfer from the film to the catalyst surface and the subsequent reaction modelled as resistances in series.Our findings indicate that the provision of inert mass transfer area to saturate the fluid with hydrogen can significantly increase the productivity per unit mass of catalyst. In addition, by controlling the ratio of catalytic and inert surface the hydrogen concentration close to the catalyst surface can be tuned. This could be utilised to adjust both the activity and selectivity of the system and therefore, give trickle bed reactors an advantage in chemical manufacturing processes.

Cermets Ni/(Ce0.9Ln0.1O1.95) (Ln = Gd, La, Nd and Sm) prepared by solution combustion method as catalysts for hydrogen production by partial oxidation of methane

Catalysts based on Ni/(Ce0.9Ln0.1O1.95) (Ln = Gd, La, Nd and Sm) have been developed and tested for hydrogen production by partial oxidation of methane. The synthesis method (SCS, solution combustion synthesis) produces macroporous composite materials composed of ceramic (cer, Ce0.9Ln0.1O1.95) and metallic (met, Ni) phases, without the need of an activation stage prior to the catalytic reaction. The catalysts have been characterized by different techniques: X-ray diffraction, N2 adsorption-desorption, Hg porosimetry, Scanning Electron Microscopy, Temperature Programmed Reduction, H2 and O2 pulse chemisorption, X-ray photoelectron spectroscopy and Raman spectroscopy. With the exception of the lanthanum-loaded catalyst, the catalysts are highly active, selective and stable; being the one doped with gadolinium the most efficient. Correlations structure-activity point out that the excellent catalytic performance is related to the high catalytic surface area per unit mass of catalyst and to an appropriate balance of nickel dispersion to oxygen vacancies of the support.

Compositional Optimization of Alloy FexNiy(OH)2 Nanoparticles for Alkaline Electrochemical Oxygen Evolution

It has recently been demonstrated by Bell and co-authors [1] that intentional iron doping into a nickel hydroxide film causes significant enhancement in electrochemical performance for the oxygen evolution half reaction (OER) of alkaline electrolysis. A subsequent study by Boettcher and co-authors [2] demonstrated that unintentional iron doping of a nickel hydroxide catalyst occurs from ppm- to ppb-level iron contaminants in alkaline electrolytes; the iron incorporates into the nickel hydroxide structure, and causes at least an order of magnitude increase in current density. Freibel et al. subsequently demonstrated that iron may in fact be the active site of OER, with nickel hydroxide acting as a host [3]. The majority of the work thus far investigating how iron content in an FexNiy(OH)2 catalyst affects OER has been performed on thin film catalysts; Burke et al. specifically describe the need for catalyst architectures that reduce mass transport limitations and allow improved access to more active sites per unit mass of catalyst [4]. As a result, there is an interest in developing nanoscale catalysts that are composed of iron and nickel and result in greatly improved performance metrics for OER over their thin film counterparts. Here, we will present results for the optimization of a FexNiy(OH)2 nanoparticle catalyst. In this work, the nanoparticles are synthesized with an alloy morphology and the atomic ratio of iron to nickel is varied from 1:5 to 5:1. Once synthesized, the nanoparticles are evaluated in 1 M KOH that has been purified to remove any iron impurities. Electrochemical performance of this series of nanoparticle catalysts will be discussed as well as our efforts to characterize the nanoparticles with electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction. [1] M.W. Louie, A.T. Bell, An investigation of thin-film Ni-Fe oxide catalysts for the electrochemical evolution of oxygen, J. Am. Chem. Soc., 135 (2013) 12329-12337. [2] L. Trotochaud, S.L. Young, J.K. Ranney, S.W. Boettcher, Nickel-iron oxyhydroxide oxygen-evolution electrocatalysts: The role of intentional and incidental iron incorporation, J. Am. Chem. Soc., 136 (2014) 6744-6753. [3] D. Friebel, M.W. Louie, M. Bajdich, K.E. Sanwald, Y. Cai, A.M. Wise, M.-J. Cheng, D. Sokaras, T.-C. Weng, R. Alonso, R.C. Davis, J.R. Bargar, J.K. Norskov, A. Nilsson, A.T. Bell, Identification of highly active Fe sites in (Ni,Fe)OOH for electrocatalytic water splitting, J. Am. Chem. Soc., 137 (2015) 1305–1313. [4] M.S. Burke, L.J. Enman, A.S. Batchellor, S.H. Zou, S.W. Boettcher, Oxygen evolution reaction electrocatalysis on transition metal oxides and (oxy)hydroxides: Activity trends and design principles, Chemistry of Materials, 27 (2015) 7549-7558.

Production of H2-free CO by decomposition of formic acid over ZrO2 catalysts

The decomposition of formic acid (HCOOH) over ZrO2 catalysts synthesized by precipitation method was investigated and their catalytic activity based on unit mass of catalyst was compared by varying the calcination temperature in the 500–1000°C range. The calcined ZrO2 samples were characterized using temperature-programed desorption (TPD) of iso-propanol (IPA), H2O, and HCOOH as well as X-ray diffraction (XRD), pyridine-adsorbed infrared spectroscopy (Py-IR) and N2 sorption. The catalytic activity as a function of the calcination temperature of ZrO2 showed a volcano-type curve with a maximum at 900°C. The catalytic activity of ZrO2 in the decomposition of HCOOH well correlated with Brönsted acid site density, and it was influenced by the crystalline phase of ZrO2. Furthermore, the evolution of the Brönsted acid site density measured by Py-IR as a function of the calcination temperature was in good accordance with the desorption temperature determined by IPA- and HCOOH-TPD experiments. When H2O vapor was added, the conversion of HCOOH slightly decreased, while the CO selectivity remained almost constant. However, when CO was supplied, the conversion of HCOOH decreased continuously, and the selectivity to H2 gradually increased, indicating that the formation of zirconium suboxides with characteristics approaching those of metals was successful using CO as a reductant.

Performance of an ultrafiltration membrane bioreactor (UF-MBR) as a processing strategy for the synthesis of galacto-oligosaccharides at high substrate concentrations.

The performance of an ultrafiltration membrane bioreactor for galacto-oligosaccharides (GOS) synthesis using high lactose concentrations (470g/L) and β-galactosidase from Aspergillus oryzae was assessed. Tested processing variables were: transmembrane-pressure (PT), crossflow-velocity (CFV) and temperature. Results showed that processing variables had significant effect on the yield, the enzyme productivity and the flux but did not on GOS concentration and reaction conversion obtained. As expected, the use of high turbulences improved mass transfer and reduced the membrane fouling, but the use of very high crossflow-velocities caused operational instability due to vortex formation and lactose precipitation. The use of a desirability function allowed determining optimal conditions which were: PT (4.38bar), CFV (7.35m/s) and temperature (53.1°C), optimizing simultaneously flux and specific enzyme productivity Under these optimal processing conditions, shear-stress and temperature did not affect the enzyme but long-term operation was limited by flux decay. In comparison to a conventional batch system, at 12.5h of processing time, the continuous GOS synthesis in the UF-MBR increased significantly the amount of processed substrate and a 2.44-fold increase in the amount of GOS produced per unit mass of catalyst was obtained with respect to a conventional batch system. Furthermore, these results can be improved by far by tuning the membranearea/reactionvolume ratio, showing that the use of an UF-MBR is an attractive alternative for the GOS synthesis at very high lactose concentrations.

Kinetics for hydrogen production by methanol steam reforming in fluidized bed reactor

Hydrogen is one of the best energy carriers. Fluidized bed reactor provides a promising approach for hydrogen production. To describe the hydrogen generating rate with methanol steam reforming in fluidized bed reactor quantitatively, dual-rate kinetic models of the reactions with exponent form were developed, including that of steam reforming reaction (SR) and decomposition reaction (DE). The reaction rate per unit mass of catalyst was related to partial pressures of components. The exponentials in kinetic equations were obtained by linear least-squares method based on the experimental data. The variance homogeneity test (F test) shows that the dynamic models are feasible with high accuracy, which can be used to predict the generating rate of hydrogen under different reaction temperatures and feed flow rates in fluidized bed reactor. The SR and DE activation energy obtained indicates that ESR <EDE, which can explain the previous observation that the CO2 selectivity decreased with the temperature increase.

Mathematical Modeling and Performance Study of Fischer-tropsch Synthesis of Liquid Fuel over Cobalt-silica

Abstract A numerical one-dimensional pseudo-homogeneous mathematical model of a fixed bed reactor for Fischer-Tropsch (FT) synthesis was developed over a simulated nitrogen-rich syngas (33% hydrogen, 17% carbon monoxide and 50% nitrogen (volume basis)), on a cobalt-silica catalyst. An algorithm was developed and the MATLAB codes were written in order to predict the product selectivity (H2O, CO2 and hydrocarbons i.e. CH4, C2, C3, C4 and C5+) and syngas conversion (CO and H2). In order to predict the kinetic parameters, the global search optimization subroutine (from MATLAB Global Optimization) was used. The model was fitted with experimental data at five different operating conditions with respect to conversion and selectivity. Discrimination between the model and the experiments was determined by the mean absolute relative residuals percentage (MARR %) and the value was 13.29%. The Effects of operating conditions such as reaction temperature, total pressure, flow rate and H2/CO molar ratio were investigated on the catalytic performance of the cobalt-silica for synthesis of liquid fuel. The model was studied in the range of 200-260 °C, 1-25 bar, reduced gas flow rate (per unit mass of catalyst) of 2.4-3.6 NL gcat-1 h-1 and H2/CO = 1.75-2.75 (mole basis).

Fischer–Tropsch synthesis on Co/ZnO – Two step activation procedure for improved performance

A two-step activation procedure (CO followed by synthesis gas, CO/SG) was employed prior to Fischer–Tropsch synthesis in a fixed-bed reactor using cobalt over ZnO catalyst (10wt% Co/ZnO). The use of the CO/SG activation procedure resulted in superior performance (higher activity and lower methane selectivity) compared to one step activations with CO or H2. High catalyst activity, in terms of CO conversion and reaction rate per unit mass of catalyst, following the CO/SG activation is attributed to the presence of hexagonal cobalt phase, which was identified from XRD measurements. Temperature programmed hydrogenation (TPH) and oxidation (TPO) were used to obtain information on the nature of cobalt phases and types of carbon on the catalyst surface after the CO activation, and after the CO/SG activation. Carbon deposited during activation of the catalyst with synthesis gas had an effect on 1-olefin content and catalytic activity.

Effect of micropores diffusion on kinetics of CH 4 decomposition over a wood-derived carbon catalyst

In order to optimise hydrogen production from biomass gasification, catalytic conversion of methane contained in a surrogate biomass syngas (CH 4 14%; CO 19%; CO 2 14%; H 2 16%; H 2O 30%; N 2 7%) is investigated over a fixed bed of porous wood char as a function of temperature (800–1000 °C) and space time (1.6–6.2 min g L −1). Determination of Thiele modulus evidences a change of kinetic regime from chemically- to diffusion-controlled when the temperature increases; this finding is particularly relevant when porous chars having an average pore width of 1 nm are used as catalysts. Mass diffusion transfers are accounted for by a model introducing an internal effectiveness factor. Knudsen diffusion in micropores is shown to limit the conversion rate of methane per unit mass of catalyst, and explains why such a rate is not proportional to the BET surface area, especially when the latter is higher than typically 300 m 2/g. It is concluded that diffusion limitations in micropores should be taken into account, otherwise underestimated activation energy and intrinsic kinetic constant are obtained in some experimental conditions.

Calculation of Kinetic Parameters and Active Sites Concentration for a New Multiple Site Model in Bulk Propylene Polymerization with the MgCl -Supported Ziegler-Natta Catalyst Using the Genetic Algorithm Method

A comprehensive triple-site-model was studied. This model was based on the new molecular dynamics outcomes obtained from the researchers on the different active sites that exist on the heterogeneous Ziegler-Natta catalyst. The model was composed of high-isospecific site (IS), low-isospecific site (IS), and aspecific site (AS). A transformation occurred on the high isotactic site and a second isotactic site was generated, as the low-isospecific site. The model is able to predict experimental results of bulk propylene polymerization with great accuracy. Moreover, the kinetic parameters and constants for each individual site has an Arrhenius type behavior. These parameters were determined using genetic algorithm adaptation method. The concentration of each type of sites, the isotactic and atactic fraction were determined during the polymerization, per unit mass of catalyst. A very good agreement was found in between the model and reported experimental results.

Stability and stabilization ofD-amino acid oxidase from the yeastTrigonopsis variabilis

The use of DAO (D-amino acid oxidase) for the conversion of cephalosporin C has provided a significant case for the successful implementation of an O(2)-dependent biocatalyst on an industrial scale. Improvement of the operational stability of the immobilized oxidase is, however, an important goal of ongoing process optimization. We have examined DAO from the yeast Trigonopsis variabilis with the aim of developing a rational basis for the stabilization of the enzyme activity at elevated temperature and under conditions of substrate turnover. Loss of activity in the resting enzyme can occur via different paths of denaturation. Partial thermal unfolding and release of the FAD cofactor, kinetically coupled with aggregation, contribute to the overall inactivation rate of the oxidase at 50 degrees C. Oxidation of Cys(108) into a stable cysteine sulfinic acid causes both decreased activity and stability of the enzyme. Strategies to counteract each of the denaturation steps in DAO are discussed. Fusion to a pull-down domain is a novel approach to produce DAO as protein-based insoluble particles that display high enzymatic activity per unit mass of catalyst.

Vanadium oxide supported on mesoporous Al 2O 3: Preparation, characterization and reactivity

The application of different techniques (diffuse reflectance-UV–vis, 51V NMR, FT-IR of adsorbed pyridine and TPR-H 2) in the characterization of vanadia supported on mesoporous Al 2O 3 catalysts shows that the nature of the vanadium species depends on the V-loading. At V-content lower than 15 wt.% of V-atoms (30% of the theoretical monolayer), vanadium is mainly in a tetrahedral environment. Higher V-contents in the catalyst leads to the formation of octahedral V 5+ species and V 2O 5-like species. Both XRD and textural results indicate that the mesoporous structure of the support is mostly maintained after the vanadium incorporation, and therefore high surface areas were obtained on the final catalysts. Al 2O 3-suppported vanadia catalysts are active and selective in the oxidative dehydrogenation of ethane, although the catalytic behavior depends on the V-loading. High rates of formation of ethylene per unit mass of catalyst per unit time have also been observed as a consequence of the high dispersion of V-atoms on the surface of the support.

Vanadium oxide supported on mesoporous Al2O3Preparation, characterization and reactivity

The application of different techniques (diffuse reflectance-UV–vis, 51V NMR, FT-IR of adsorbed pyridine and TPR-H2) in the characterization of vanadia supported on mesoporous Al2O3 catalysts shows that the nature of the vanadium species depends on the V-loading. At V-content lower than 15 wt.% of V-atoms (30% of the theoretical monolayer), vanadium is mainly in a tetrahedral environment. Higher V-contents in the catalyst leads to the formation of octahedral V5+ species and V2O5-like species. Both XRD and textural results indicate that the mesoporous structure of the support is mostly maintained after the vanadium incorporation, and therefore high surface areas were obtained on the final catalysts. Al2O3-suppported vanadia catalysts are active and selective in the oxidative dehydrogenation of ethane, although the catalytic behavior depends on the V-loading. High rates of formation of ethylene per unit mass of catalyst per unit time have also been observed as a consequence of the high dispersion of V-atoms on the surface of the support.