ODH Of Ethane Research Articles

Chemical looping oxidative dehydrogenation of ethane over Fe-Co/HZSM-5 redox catalyst

Chemical looping oxidative dehydrogenation (CL-ODH) has been extensively investigated as a green strategy for light olefins production from alkanes/naphtha without thermodynamic equilibrium constraints. However, achieving high ethylene selectivity as well as promising ethane conversion at relatively low-temperature (≤600 °C) in CL-ODH of ethane is still challenging. Herein, we show that Fe-Co dual-metal oxides supported by HZSM-5 zeolite can be used as appropriate redox catalysts for low-temperature CL-ODH of ethane. By tuning the loading mass ratio of Fe: Co oxides on the HZSM-5 support, 87 % ethylene selectivity and 23 % ethane conversion can be attained at 600 °C and 4800 mL·h−1·g−1 with the best-performing sample, i.e., 8Fe-2Co/HZ5(200). The stability of this sample was then assessed across 100 redox cycles, no obvious coking was observed within the entire test. Comparison test and physicochemical characterization results showed that both sample acidity and the role of dual-metal oxides are pivotal for ethane ODH to yield ethylene, in which dual-metal oxides are responsible for low-temperature ethane activation while proper amount of medium-strong acidity is critical for ethylene selectivity as well as activity. Overall, the present work demonstrates the feasibility of using HZSM-5 supported Fe-Co dual-metal oxides as redox catalyst for low-temperature CL-ODH of ethane, and provides a facile way for redox catalyst design to balance sample activity and selectivity.

Redox oxide@molten salt as a generalized catalyst design strategy for oxidative dehydrogenation of ethane via selective hydrogen combustion

The current study demonstrates a redox oxide @ molten salt core-shell architecture as a generalized redox catalyst design strategy for chemical looping – oxidative dehydrogenation of ethane. 17 combinations of redox active oxides and molten salts were prepared, evaluated, and characterized. X-ray diffraction indicates that the redox oxides and molten salts are fully compatible, forming separate and stable phases. X-ray photoelectron spectroscopy demonstrates that the molten salts aggregate at the redox oxide surface, forming a core-shell structure to block the non-selective sites responsible for COx formation. Up to ∼74 % single-pass olefin yields were achieved using the proposed redox catalyst design strategy. Statistical analyses of the performance data indicate the potential to achieve up to 86.7 % single-pass yield by simply optimizing the operating conditions using the redox catalysts reported in this study. Meanwhile, the generalizability of the catalyst design strategy offers exciting opportunities to further optimize the composition and performance of the redox catalysts for ethane ODH under a chemical looping scheme with significantly reduced energy consumption and CO2 emissions.

Linde Engineering and Clariant jointly develop revolutionary ethane ODH catalysts

Linde Engineering and Clariant jointly develop revolutionary ethane ODH catalysts

Tuning the properties of NiO supported on silicon-aluminum oxides: Influence of the silica amount in the ODH of ethane

Nickel-based catalysts (40 wt% Ni) with commercial silicon-aluminum oxides as supports were prepared. The variation of the silica amount (10%, 20% and 40%) was studied. These catalytic formulations were characterized by N2 adsorption, SEM/EDX, HR-TEM, XRD, LRS and XPS, and tested in the oxidative dehydrogenation of ethane (ODHE) to produce ethylene. Besides, they were compared with a nickel-based silica-supported catalyst (NiO/SiO2). The effect of the proportion of silica in the supports on the generated Ni species, and consequently on the respective catalytic performances, was investigated. The results showed that, despite of the same NiO loading in all catalysts, different NiO-support interactions and surface amounts of non-selective oxygen species were obtained. These features had an impact on the catalytic behavior of each formulation. Remarkably, while ethylene selectivity was high and almost the same, ethane conversion increased with the silica amount in the supports. On the other hand, as expected, pure silica as a support resulted in high conversion but markedly low selectivity, favoring the total ethane oxidation to carbon dioxide. This work demonstrates that it is possible to increment the alkane conversion without sacrificing the alkene selectivity by tuning the active species properties through the increase of the amount of silica in the supports.

Al2O3-Supported W–V–O bronze catalysts for oxidative dehydrogenation of ethane

Vanadium-containing hexagonal tungsten bronze (HTB) structures supported on Al2O3are more selective to ethylene during ethane ODH than supported vanadium oxides.

Oxidative dehydrogenation of ethane on diluted or promoted nickel oxide catalysts: Influence of the promoter/diluter

Ti- and Nb- containing NiO catalysts have been synthesized by two different preparation methods: i) by precipitation (Me-Ni-O oxides, Me = Nb or Ti), in order to prepare promoted NiO catalysts; and ii) by wet impregnation on TiO2 or NbOx supports, in order to prepare diluted/supported NiO catalysts. The catalysts have been also characterized and tested in the oxidative dehydrogenation of ethane. The catalytic performance of Ti- and Nb-promoted catalysts strongly depends on the composition, although in both cases the optimal one is found at similar Ti or Nb loadings (ca. 90 wt% NiO), showing similar ethylene selectivity in the ODH of ethane (ca. 90% at 10–20% ethane conversion). However, in the case of diluted catalysts, the catalytic behavior of Ti- and Nb-containing catalysts is drastically different. Then, over TiO2-diluted NiO catalyst, the highest selectivity to ethylene (ca. 90% selectivity) is achieved at NiO loading of 20 wt.%. However, over Nb2O5-diluted NiO catalyst, selectivity to ethylene was lower than 70%. A discussion on the characteristics of selective catalysts is done. In this case, the best catalysts must present a low concentration of free NiO and TiO2 or Nb2O5 phases, maximizing the Ni-O-Ti or Ni-O-Nb interaction. Interestingly, this takes place at different NiO loading depending on the preparation method and the nature of promoted/diluter. The low selectivity to ethylene achieved by NiO diluted with Nb2O5 has been related to the low interaction of NiO with the surface of Nb2O5, which hinders the elimination of unselective electrophilic O species.

Metal solution precursors: their role during the synthesis of MoVTeNb mixed oxide catalysts

Crystals of MoVTeNbOxM1 phase for the ODH of ethane to ethylene.

A simple approach to describe hydrodynamics and its effect on heat and mass transport in an industrial wall-cooled fixed bed catalytic reactor: ODH of ethane on a MoVNbTeO formulation

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 (dt/dp) ranging from 3 to 6. The PHA allows the estimation of both turbulent viscosity (μt) 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 dt/dp=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.

Catalytic activity in the oxidative dehydrogenation of ethane over Ni and/or Co molybdate catalysts: Synthesis and characterization

Ni and/or Co molybdate based catalysts were synthetized by co-precipitation for the oxidative dehydrogenation of ethane reaction. The catalysts were characterized by several techniques such TGA-DTA, HT-XRD, XRD, LRS, N 2 adsorption, XPS and TPR. The results showed that the addition of Ni or Co to MMoO 4 matrices (M=Ni or Co) led to a high dispersion of additives into the molybdenum matrix without the formation of a significant amount of other bulk metal oxides. Compared to the pure MMoO 4 , the modified molybdenum (Ni 0.5 Co 0.5 MoO 4 ) presents a higher thermal stability (up to 1000 °C). It has a lower BET surface area and higher reduction temperature compared to those of the NiMoO 4 sample. In the ODH of ethane, Ni 0.5 Co 0.5 MoO 4 shows a lower catalytic activity compared to that of MMoO 4 samples; however, the ethylene selectivity is enhanced (exceeding 90%). As a result, these series of catalysts show improved efficiency for ethylene production in the ethane ODH reaction.

Flexible NiZr-based structured catalysts for ethylene production through ODH of ethane: Catalytic performance enhancement

Flexible structured catalysts based on Ni and Zr deposited on a ceramic paper made of SiO2-Al2O3 and ZrO2 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.

Oxidative dehydrogenation of ethane to ethylene over Mo-incorporated mesoporous SBA-16 catalysts: The effect of MoOx dispersion

A series of highly dispersed Mo-incorporated mesoporous SBA-16 catalysts (Mo-SBA-16) were successfully synthesized by one-step hydrothermal method. The effects of different Mo loadings and MoOx structure of the Mo-SBA-16 catalysts for the oxidative dehydrogenation of ethane (ODHE) were investigated. Framework-incorporation promotes a better dispersion of molybdenum oxo species. Different kinds of MoOx species are related to the activity and selectivity of ethylene for ODH of ethane. A small amount of Mo species was incorporated into the framework of SBA-16, which greatly increased the selectivity of ethylene, but the C2H6 conversion was slightly greater than that of Mo/SBA-16 catalysts. Meanwhile, for both Mo-SBA-16 and Mo/SBA-16 catalysts the selectivity of ethylene was significantly enhanced with the increasing of reaction temperature. Moreover, Mo-SBA-16 catalysts showed much higher selectivities of ethylene than Mo/SBA-16 ones, mainly due to the presence of isolated MoOx species in the framework of SBA-16. And the maximal selectivity to C2H4 of 75.7% was obtained over 0.05Mo-SBA-16 catalyst. The three-dimensional mesoporous channels of Mo-SBA-16 allowed a better diffusion of ethane and produced ethylene to improve the catalytic performance.

A high-throughput reactor system for optimization of Mo–V–Nb mixed oxide catalyst composition in ethane ODH

75 Mo–V–Nb mixed oxide catalysts with a broad range of compositions were tested using a high-throughput reactor in order to optimize the composition for the ethane oxidative dehydrogenation reaction.

Highly Selective Supported Alkali Chloride Catalysts for the Oxidative Dehydrogenation of Ethane

Binary, ternary and quaternary molten eutectic alkali chloride catalysts, supported on mildly redox active oxides, were investigated for the oxidative dehydrogenation of ethane. The influence of different support oxides, on the catalytic performance, as well as that of different anions (bromide vs. chloride) and cations in a chloride eutectic system were studied. Metal oxides which react with chlorides are not suitable and lead to substantial deactivation. Especially supports forming volatile chlorides induce irreversible chloride depletion. Bromides catalyze oxidative dehydrogenation of ethane with higher rates, but lower olefin selectivities, highlighting the similarities and differences of Cl− and Br− in the redox cycle. Two catalysts were identified having olefin selectivities up to 98 % at 70 % ethane conversion, which ranges among the highest selectivities reported for ethane ODH.

Metal oxides modified NiO catalysts for oxidative dehydrogenation of ethane to ethylene

The sol–gel method was applied to the synthesis of Zr, Ti, Mo, W, and V modified NiO based catalysts for the ethane oxidative dehydrogenation reaction. The synthesized catalysts were characterized by XRD, N2 adsorption, SEM and TPR techniques. The results showed that the doping metals could be highly dispersed into NiO domains without the formation of large amount of other bulk metal oxide. The modified NiO materials have small particle size, larger surface area, and higher reduction temperature in contrast to pure NiO. The introduction of group IV, V and VI transition metals into NiO decreases the catalytic activity in ethane ODH. However, the ethylene selectivity is enhanced with the highest level for the Ni–W–O and Ni–Ti–O catalysts. As a result, these two catalysts show improved efficiency of ethylene production in the ethane ODH reaction.

Investigation of engineering aspects in ethane ODH over highly selective Ni0.85Nb0.15Ox catalyst

A wide range of operating variables is investigated in ethane oxidative dehydrogenation reaction over Ni0.85Nb0.15Ox mixed oxide catalyst. Ethane to oxygen ratio C2H6/O2=2 and feed composition of 10% C2H6/5% O2 were selected as the best trade-off between optimum selectivity and acceptable ethane conversion level. Although suppressing oxygen partial pressure was found to increase ethylene selectivity, a minimum oxygen concentration is required in order to maintain the catalyst in oxidized state. Staged oxygen admission leads to an increase in ethylene selectivity but in expense of ethane conversion, as confirmed by experimental and simulation results. Regarding reactor configuration, preliminary testing under fluid bed conditions proved quite promising. Finally, Ni0.85Nb0.15Ox mixed oxide presented satisfactory stability, as proven both by 100 h on stream stability test and by subjection to a steaming procedure after which the catalytic performance was not deteriorated.

Activity of the Ni–Al Mixed Oxides Prepared from Hydrotalcite-Like Precursors in the Oxidative Dehydrogenation of Ethane and Propane

The activity of Ni–Al mixed oxides obtained by the thermal pre-treatment of Ni–Al hydrotalcite-like precursors was studied in the ODH of ethane and propane. The activity of the Ni–Al mixed oxide catalysts was studied with respect to (i) the role of Ni content and (ii) the role of temperature during Ni–Al HTs thermal pre-treatment. The structure analysis and the activity of Ni–Al mixed oxides were discussed in three groups; (A) the catalysts pre-treated at 500 °C, (B) the catalysts pre-treated at 600 °C and (C) the Ni2–Al catalyst with constant Ni content pre-treated at 500–900 °C. Ni–Al mixed oxides were active and selective catalysts in the ODH of ethane even at 450 °C. On the other hand, the catalysts posses low selectivity to propene. It is supposed that the interaction of NiO with alumina phase plays the critical role in the active and selective catalysts. The Ni–Al mixed oxides were characterized by XRD, H2-TPR and diffuse reflectance spectroscopy.

Ni–Me–O mixed metal oxides for the effective oxidative dehydrogenation of ethane to ethylene – Effect of promoting metal Me

This work examines the effect of Li, Mg, Al, Ga, Ti, Nb and Ta on the properties and catalytic behavior of Ni-based mixed metal oxides in the ethane oxidative dehydrogenation reaction. In all mixed oxides, with the exception of Ta, the dopants modify the NiO lattice, which contracts or expands depending on the radius of the cation, indication for the formation of solid solutions. This systematic study of doping metals varying from low (+1) to high valence (+5) elements clearly demonstrates the large effect of the dopants’ valence. O 2-TPD experiments showed that increasing the valence of the foreign cation reduces the non-stoichiometric oxygen due to the cation deficient nature of the host oxide, in complete agreement with the principle of controlled valence. Temperature-programmed isotopic oxygen exchange measurements portray furthermore that not only the quantity but also the lability of the oxygen species reduces with increasing dopant valence. These electrophilic oxygen species catalyze the total oxidation reactions of ethane to CO x , and thus their reduction/elimination favors the selective oxidation to ethylene. Ni–Nb–O exhibited the best catalytic performance with a 46% ethene yield at 400 °C, while Ni–Li–O demonstrated the worst results with a respective yield of 8.42%. Based on the results of the present work, it can be inferred that the catalytic properties of NiO in ethane ODH can be tuned with doping, based on the nature of the dopant in Me-promoted NiO catalysts. Depending on the valence of the foreign species, the dopants can increase or decrease the unselective electrophilic oxygen radicals of NiO, leading to, respectively, reduced or enhanced ethane ODH activity.

Oxidative dehydrogenation of ethane over vanadium-based hexagonal mesoporous silica catalysts

Vanadium-containing hexagonal mesoporous silica catalysts were tested in oxidative dehydrogenation of ethane. V-HMS catalysts (0.3–9.0 wt.% V) were prepared by impregnation with solution of vanadyl acetylacetonate, and by incorporation of vanadium in the synthesis process. The prepared catalysts achieved a different distribution of vanadium species (isolated monomeric units with tetrahedral coordination, oligomeric units connected by V O V bonds up to distorted tetrahedral coordination, two-dimensional polymeric units in octahedral coordination, and bulk vanadium oxides). The contribution deals with the understanding of the relationship between the distribution of vanadium species and their activity in ODH of ethane. It has been found that both monomeric and oligomeric vanadium species play important role in ODH of ethane. The activity correlated with the population of oligomeric tetrahedrally coordinated vanadium species, which were evidenced by the UV–vis band at 315 nm. To analyze this effect, V-HMS catalysts were characterized by means of UV–vis spectroscopy, H 2-TPR and N 2-adsorption.

Characterization and Reactivity of TiO2/SiO2 Supported Vanadium Oxide Catalysts

Several TiO2/SiO2 supports and supported vanadium oxide (vanadia) catalysts of varying titania and vanadia content are synthesized and characterized. Titania rutile phase is not detected for the TiO2/SiO2 supports even up to a calcinations temperature of 1073 K. The supported vanadia catalysts were also studied for the ethane and propane ODH reaction and compared with TiO2 (Degussa P25) supported catalysts. Surface vanadia species are present on the titania or silica part of the TiO2/SiO2 support depending on the titania and vanadia loading of the catalyst. Depending on the vanadia loading in the V2O5/TiO2/SiO2 catalyst the anatase to rutile phase transformation may occur below 1073 K. Furthermore, the ODH activity is retained or decreases less rapidly compared to the TiO2 supported catalyst as the calcination temperature is increased. Consequently, the TiO2/SiO2 supported vanadia catalysts do provide certain advantages compared to the TiO2 (Degussa P25) supported system.

HRTEM characterization of the nanostructural features formed in highly active Ni–Nb–O catalysts for ethane ODH

In this work, we report an in-depth structural characterization of pure NiO and Ni–Nb–O mixed oxide catalysts (Nb/Ni = 0–0.25), highly active and selective materials for ethylene production via ethane ODH, using high resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray analysis (EDS). This study led to the identification and investigation of the nanostructural features formed in the Nb-doped NiO catalysts and their relation with the excellent catalytic functionality of the Ni–Nb–O materials. It was found that low-temperature treatment of pure NiO leads to the formation of a non-stoichiometric oxidic phase with characteristic structural defects due to cationic deficiency, as demonstrated by microscopy results. On the Nb-doped oxides, two distinct structural phases, formed via the reaction of the Nb cations with the cationic vacancies, were identified: a NiO phase having Nb cations incorporated in the host lattice, which retains its initial cubic structure (Ni–Nb solid solution), and a highly distorted Nb-rich phase, precursor for the formation of the mixed NiNb2O6 crystal compound. The reduction of the structural defects in NiO via their interaction with the niobium ions was correlated with the extremely high selectivity of the Ni–Nb–O catalysts to ethylene in the ethane ODH reaction, since these vacancies lead to the formation of strong oxidizing electrophilic oxygen species (O), responsible for the total oxidation of ethane to CO2. # 2007 Elsevier B.V. All rights reserved.