Oxydehydrogenation Of Ethane Research Articles

N2O Assisted Ethane Transformation into Ethylene Using NiO−CeO2−ZrO2 Catalysts

AbstractNiO−CeO2 and NiO−CeO2−ZrO2 catalysts have been synthesized, electrochemically characterized (Mott‐Schottky (MS) measurements and Electrochemical Impedance Spectroscopy), physicochemically characterized (by N2 adsorption, XRD, Transmission Electron Microscopy and XPS) and tested in the N2O assisted ethane oxydehydrogenation. The use of low Zr‐loadings (Zr/Ce=0.1 at. ratio) has led to the optimal results in the ethylene production, improving those obtained by the Zr‐free NiO−CeO2 catalyst. However, high Zr‐loadings have meant a decrease in the olefin production. The catalytic results obtained have been explained considering the amount of oxygen vacancies, the crystalline phases formed and, especially, the nature of the surface Ni species. Importantly, the use of N2O as an oxidizing agent leads to a remarkable improvement in the selectivity to the olefin compared to that obtained employing molecular O2. Then, for a given ethane conversion the selectivity to ethylene is ca. 15 points higher using N2O than using O2. Another additional positive aspect of this NiO−CeO2−ZrO2 catalyst is its high catalytic stability.

Corrigendum: Selective catalytic and kinetic studies on oxydehydrogenation of ethane with CO 2 over lanthanide metal catalysts

Corrigendum: Selective catalytic and kinetic studies on oxydehydrogenation of ethane with CO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /> <mml:mn>2</mml:mn> </mml:msub></mml:math> over lanthanide metal catalysts

Selective catalytic and kinetic studies on oxydehydrogenation of ethane with CO2 over lanthanide metal catalysts

Selective catalytic and kinetic studies on oxydehydrogenation of ethane with CO2 over lanthanide metal catalysts

Ethane oxydehydrogenation over TiP2O7-supported NiO catalysts

Titanium pyrophosphate-supported NiO catalysts with different Ni loadings in the range from 10 to 26 wt. % were prepared by wet impregnation, characterized by nitrogen adsorption at −196 °C, ICP-OES, XRD, CO2-TPD and H2-TPR techniques and tested in ethane oxydehydrogenation (ODH) in the temperature range from 350 to 450 °C. With increasing the Ni loading, the surface area of the catalysts decreased while the NiO particle size, the basicity and the reducibility increased strongly influencing their catalytic performance. Increasing the Ni loading boosted ethane conversion that reached 36 and 50 % at 425 and 450 °C, respectively, for the highest nickel loading catalyst. Ethylene was the main reaction product for all the catalysts. The ethylene selectivity at isoconversion increases with increasing the Ni loading. The stability of the catalysts was studied at a temperature as high as their calcination temperature, i.e. 450 °C, and at lower temperature.

Double effect of La as a promoter for Ni/Al2O3 cordierite monoliths in the oxydehydrogenation of ethane (ODE)

In the present work different amounts of lanthanum were added to Ni/Al2O3 cordierite monoliths with the objective to enhance the catalytic performance of the un-promoted structured catalyst in the oxidative dehydrogenation of ethane (ODE). The impact of the amount of promoter on the catalytic performance of the structured catalysts is discussed through the use of different characterization techniques: LRS, FTIR, Py-TPD, TPR, XPS and SEM-EDX. The incorporation of La was found to increase ethane conversion by an increase in the reducibility of Ni species, with a drop in the ethylene selectivity. Despite this drop, at constant reaction temperature the olefin selectivity maintained a constant value with the increase of ethane conversion, generating a beneficial effect in these catalysts. The presence of La generated: i) a new type of Ni2+ species due to Ni-La-O interactions and ii) La-Al-O species, which moderated the Ni-Al ones promoting the drop of the ethylene selectivity. Both species also modify the total acidity and reduce the strong acid sites, preventing ethylene oxidation. Thus, as the ethylene production increases, its selectivity remains invariant. An optimal La/Ni ratio was found around 0.08, which generated appropriate interactions among the active species, boosting the ethylene yield at 400 °C by 2.7 times from 4.9% (un-promoted structured catalyst, Ni-M) to 13.4% (NiLa-M, La/Ni: 0.08).

Catalytic Abatement of Nitrous Oxide Coupled with Ethane Oxydehydrogenation over Mesoporous Cr/Al2O3 Catalyst

Waste nitrous oxide (N2O) was utilized as an oxidant for ethane oxydehydrogenation reaction at the temperature range from 450 °C to 700 °C over the mesoporous Cr/Al2O3 catalyst synthesized via the one-pot evaporation-induced self-assembly (EISA) method. The catalyst was characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption-desorption analysis. The obtained mesoporous material with favorable textural property and advantageous thermal stability was investigated as the catalyst for ethane oxydehydrogenation. It was found that the utilization of N2O as an oxidant for the oxydehydrogenation reaction of ethane resulted in simultaneous and complete N2O abatement. Moreover, the catalytic conversion of C2H6 to C2H4 was increased from 18% to 43% as the temperature increased from 450 °C to 700 °C. The increased N2O concentration from 5 vol % to 20 vol % resulted in an increased ethane conversion but decreased ethylene selectivity because the nonselective reactions occurred. Ethane was converted into ethylene with approximately 51% selectivity and 22% yield at 700 °C and N2O concentration of 10%. After a catalytic steady state was reached, no obvious decline was observed during a 15 h evaluation period.

Understanding the kinetic behavior of a Mo–V–Te–Nb mixed oxide in the oxydehydrogenation of ethane

Two kinetic models based on Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) mechanisms were developed to describe the oxydehydrogenation of ethane to yield ethylene over a Mo–V–Te–Nb catalyst. Obtained in a lab-scale fixed-bed reactor, experimental data at the steady-state were used to estimate the kinetic models parameters via a nonisothermal regression. Experiments were performed using an ethane, oxygen and nitrogen mixture as feedstock, spanning temperatures from 673 to 753K, inlet partial pressures of oxygen and ethane between 5.0 and 22.0kPa, and space–time from 10 to 70gcath(molethane)−1. Ethylene, CO and CO2 were the only detected products, the selectivity for ethylene ranged from 76% to 96% for an ethane conversion interval 4–85%. A series of tests feeding ethylene instead of ethane were also performed at 713K, varying inlet partial pressures and space–time in the same ranges as was done for ethane. Ethylene conversion was relatively low, 3–14%, the dominant product being CO with CO/CO2 ratios from 0.73 to 0.79. The LH mechanism was found to represent better the experimental data. The oxydehydrogenation of ethane was the reaction with the lowest activation energy, 108–115kJmol−1. Except for the conversion of ethane into CO2, deep oxidations were detected as very energetically demanding steps, 156–193kJmol−1. Competitive adsorption between reagents and products occurred in the two mechanisms particularly at relatively high reaction severity, water re-adsorption being weaker in comparison with COx re-adsorption.

Niobium-containing catalysts for oxydehydrogenation of hydrocarbons and alcohols

The first methods are developed for introducing niobium(V) into Mg-Al hydrotalcites used as precursors of oxide catalysts for oxydehydrogenation (OD) of alkanes and alcohols. Samples of niobium(V)-containing oxide catalysts are synthesized. Their catalytic properties are studied in oxydehydrogenation of ethane and ethylbenzene to styrene, oxidation dehydrocyclization of octane into ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to ketone (octane-(2)-one). It is ascertained that ethane transformation into ethylene is highly a selective highly process (92–97%) at low temperatures (450–500°C) in the presence of a niobium-containing catalyst; the catalyst is appreciably efficient in ethylbenzene transformation to styrene and dehydrocyclization of n-octane to ethylbenzene and styrene, and in oxydehydrogenation of secbutanol to octane-(2)-one. All the catalysts studied operate stably in OD reactions; no decrease in their activity or selectivity was detected after 50 h operation.

Nitrous oxide as an oxidant for ethane oxydehydrogenation

Waste nitrous oxide was used as an oxidant for ethane oxydehydrogenation performed at the range of temperature from 350 to 450°C over iron modified zeolite catalysts. Different zeolite matrices (zeolite ZSM-5 of different Si/Al ratio, H-Y, mordenite) modified with iron cations introduced into zeolite by means of ionic exchange were applied as catalysts for the reaction under study. Additionally, amorphous silica and alumina silica as well as silicalite of MFI structure were also used as a matrix for iron ions accommodation and they were tested for oxydehydrogenation reaction. It was found that only iron modified zeolites showed activity for reaction under study. Amorphous oxide supports and crystalline neutral silicalite modified with iron cations by means of impregnation were completely inactive for oxydehydrogenation reaction. The best catalytic performance was found on iron modified zeolites of MFI structure. The Si/Al ratio of the ZSM-5 matrix influenced the activity for ethane oxydehydrogenation reaction insignificantly. N2O oxidant was partly utilized for ethane oxidation (towards ethene or carbon oxides), while some part of the oxidant was decomposed to nitrogen and oxygen. Performing the reaction at 450°C resulted in a high ethene yield and complete N2O removal.

Oxycracking of hydrocarbons: chemistry, technology and economic potential

In 1993, Huff and Schmidt reported the oxydehydrogenation of ethane to ethene at millisecond contact time. Shell Chemicals performed a study to confirm these claims and explore the technical scope and economic potential of this technology. The technical and economical results are summarised here and compared with various oxydehydrogenation and oxycracking studies that have been reported in the literature since then. Beyond confirming the initial claims and later findings, we also disclose new results such as the conversion of methane to ethene and the cracking alkenes to alkynes and dienes. The economic analysis concluded that this technology would at best provide marginal cost benefits over the existing steam cracker technology. However, it does not offer sufficient economic advantages to justify the development costs and take the implementation risks. The same seems to apply to several oxycracking technologies reported in the literature.

Is True Ethane Oxydehydrogenation Feasible

Oxydehydrogenation of ethane as a route to ethylene has the attractive feature of removing the thermodynamic equilibrium conversion limitation of the simple dehydrogenation. For example, in the dehydrogenation of ethane to ethylene, the maximum conversion possible at 1000 °C is 51%, while essentially complete (100%) conversion is possible even at ambient conditions. The best catalysts discovered to date are those from Union Carbide's work (in the late 1970s and early 1980s), which operate at 300-400 °C. These reducible Mo–V–Nb oxide catalysts are thought to react via a surface ethoxide intermediate on a Mo or V site that can then undergo a β-elimination process to form ethylene. On the other hand, the surface ethoxide can be oxidized further to form surface acetate, which leads to acetic acid on hydrolysis with water. Aside from these low-temperature reducible catalysts, many catalysts containing reducible metal oxides and non-reducible metals are known to convert ethane to ethylene at 500-800 °C. It is proposed that these catalysts are essentially dehydrogenation catalysts where the H2 formed from straight dehydrogenation or during a surface intermediate stage after H-abstraction is converted to H2O, thereby shifting the dehydrogenation equilibrium. Therefore, the big question, the challenge, and the opportunity remains as to whether true oxydehydrogenation is possible at relative low-to-moderate temperatures? This challenge/opportunity will be discussed in the backdrop of some of the recent advances in alkane activation.

Heteropoly Compounds as Precursors of Catalysts for Oxydehydrogenation of Ethane

Lacunary tungstophosphoric heteropoly compounds of Keggin structure modified with excess of manganese ions and subsequently calcined at 430-500 °C show high activity and selectivity in oxydehydrogenation of ethane. Steady state ethane conversion is about 25% and selectivity towards ethene 60%. The active catalytic system being a result of reaction between a lacunary heteropoly compound and excess of manganese (II) cations does not show the Keggin structure anymore.

Nanostructured ceria-based catalysts for oxydehydrogenation of ethane with CO2

Nanostructured cerium oxides, pure or doped with CaO, prepared from amorphous acetate precursors obtained by the freeze drying method, exhibit high surface areas and are active and selective catalysts for the oxydehydrogenation of ethane (ODE) using CO2as an oxidant. The incorporation of Ca into a solid solution in the ceria framework reduces the activity but improves markedly the selectivity to ethene and the efficiency of CO2. Under reaction conditions, the pure ceria was stable even at 1023 K, while the surface area of the Ca-containing sample decreased markedly. This change was accompanied by a drastic increase in the selectivity to ethene, allowing to obtain yields of ethene up to 22% with 91% selectivity.

Characterization of MnAPO-5 for Ethane Oxydehydrogenation

Manganese-substituted AlPO4-5 molecular sieve (MnAPO-5) was characterized by temperature-programmed reduction (TPR) and diffuse reflectance UV−Vis and electron paramagnetic resonance (EPR) spectroscopies, and the results were compared with those of manganese oxides impregnated on AlPO4-5 (Mn/AlPO4-5). It was found from TPR that the manganese interacted strongly with the aluminophosphate surface in MnAPO-5. Higher temperatures were required to reduce the manganese species on MnAPO-5 by hydrogen than to reduce those on Mn/AlPO4-5. The TPR, UV−Vis, and EPR results indicate that Mn2+ or Mn3+ was the major oxidation state of manganese in MnAPO-5, in which a small amount of MnO2 or Mn2O3 was also found. O2- was observed from AlPO4-5, MnAPO-5, and Mn/AlPO4-5 by EPR at gzz = 2.021, gxx = 2.008, and gyy = 2.003; it existed on the surface of the aluminophosphate rather than being associated with manganese on either MnAPO-5 or Mn/AlPO4-5. A kinetic model involving oxygen and ethane adsorption was proposed for ethane oxydehydrogenation over MnAPO-5. The surface reaction was the rate-determining step. The activation energy for the reaction and the enthalpy and entropy changes for the adsorptions of ethane and oxygen were obtained in this study. Because positive entropy and enthalpy changes for oxygen chemisorption on the MnAPO-5 surface were found, it is proposed that surface rearrangement around the Mn catalytic center occurred during oxygen chemisorption.

An 18O 2 Temperature-Programmed Isotope Exchange Study of Transition-Metal-Containing ZSM-5 Zeolites Used for Oxydehydrogenation of Ethane

The oxydehydrogenation of ethane was studied over a number of transition-metal containing ZSM-5 catalysts, e.g., Co-H-ZSM-5, Cu-Na-ZSM-5, Nb-ZSM-5, and V-ZSM-5. It has been shown that the introduction of transition metal cations into ZSM-5 zeolite, either as charge balancing cations (Co 2+, Nb 5+) or as lattice cation (V 5+), enhances the activity and selectivity of the catalysts for the oxydehydrogenation of ethane. The 18O 2 temperature-programmed isotope exchange technique was used to probe the likely active sites on the catalysts. It was demonstrated that the introduction of transition metal cations results in the formation of active sites responsible for the formation of single-step double exchange between gas phase oxygen and lattice oxygen. The activity for formation of single-step double exchange 16O 2 is a good indicator for the activity for oxydehydrogenation of ethane to form ethylene. The introduction of transition metal cations (Cu 2+, Co 2+, etc.) into ZSM-5 zeolite lowers the temperature required for isotope exchange between gas phase oxygen and lattice oxygen. The temperature required for isotope exchange depends on the cations introduced. The activity for facilitating single-step double exchange between gas phase 18O 2 and lattice oxygen ( 16O) and the activity for oxydehydrogenation of ethane to ethylene decrease in the same order: Co-H-ZSM-5 > Cu-Na-ZSM-5 > [V]-ZSM-5 > Nb-ZSM-5 > Na-ZSM-5 ∼ H-ZSM-5 ∼ Cu-ZSM-5. It appears that the structural defects created by introducing transition metal cations are responsible for the enhanced activity and selectivity for the oxydehydrogenation of ethane. NH 3-TPD results show that the presence of strong Brønsted acid sites are undesired for oxydehydrogenation reactions. However, the presence of relatively weaker acid sites is not harmful for the reaction.

Surface chemistry in the oxidative coupling of methane

The various aspects of the chemistry involved in the oxidative coupling of methane are considered, with special focus on the surface chemistry, i.e., on the heterogeneous part of this complex hetero-homogeneous process. The elementary steps which control either the primary or the secondary reactions are analysed in the light of recent results obtained with state-of-the-art techniques such as the isotopic transient kinetics and the fast pulse TAP reactor. The two main routes for methane activation via homolytic or heterolytic splitting of the CH bond are discussed together with the modes of oxygen activation and their dependence on the catalyst nature. A tentative list of various active sites corresponding to the specific stages of the reaction is provided. In view of a better understanding of the secondary conversion of ethane into ethylene and further on into CO x , recent studies devoted to the oxydehydrogenation of ethane are reviewed with an introduction to the development of low temperature processes. The occurrence of a single mechanism or of several ones adapted to the various families of active catalysts is discussed on the basis of the huge amount of literature available at the present time.

Ethane Oxydehydrogenation over Supported Vanadium Oxides

Ethane oxydehydrogenation to produce ethylene was studied over vanadium oxides supported on either silica gel, HZSM-5, silicalite, or AlPO[sub 4]-5. Characterization of the catalysts was carried out by X-ray photoelectron spectroscopy for the vanadium binding energy, temperature-programmed desorption of ammonia for the number of acidic sites on the supports, and redox titration for the number of chemisorption sites on vanadium oxides. The results of kinetic studies showed that the ethane oxydehydrogenation rates over vanadium oxide were enhanced by the presence of acidic sites on the supports. The rate equations thus derived suggested that the reduction of vanadium oxide sites by adsorbed ethane was the rate-determining step. It is likely that the support acidity can either promote the vanadium oxide reduction activity or increase the equilibrium constant of ethane adsorption on the catalyst.

Kinetic study of ethane oxydehydrogenation over AlPO-5

The kinetics of ethane oxydehydrogenation to produce ethylene over AlPO-5, a member of the aluminophosphate molecular sieve family, has been investigated over the temperature range 748--798 K at atmospheric pressure. It was observed that parallel reactions to ethylene and carbon oxides occur on the surface. A kinetic model involving oxygen adsorption was proposed for the ethane oxydehydrogenation. On the basis of the kinetic analysis, it is suggested that the reactions of ethane on the surface through two different sites are the rate-determining step. The apparent activation energy was 83 kcal/mol. For oxygen adsorption on the surface, the changes of enthalpy and entropy were {minus}23 kcal/mol and {minus}25 cal/mol K, respectively. These explain the adsorption phenomena reasonably.

Kinetics of the water-gas shift reaction over several alkane activation and water-gas shift catalysts

The water-gas shift reaction (WGS) over three commercial WGS catalysts and four oxide catalysts used for alkane activation has been studied at atmospheric pressure and in the temperature range of 160 to 600 °C. The oxide catalysts used were two ethane oxydehydrogenation catalysts, namely Mo 19V 5Nb 1O x and V 5Nb 1O x , and two methane coupling catalysts, namely Ca 3NiK 0.05O x and LiMgO x . The commercial water-gas shift catalysts used were two Fe 3O 4-Cr 2O 3 catalysts and one CuZnO/Al 2O 3 catalyst. All catalysts except the ethane oxidehydrogenation catalysts and LiMgO x showed high activity for the water-gas shift reaction below 400°C. It is evident that Fe, Cr, Zn, Cu and Ni oxides or metals enhance the water-gas shift reaction. The commercial CuZnO/Al 2O 3 catalyst was the most active WGS catalyst per gram of the catalyst at 160–250°C, whereas the Fe 3O 4-Cr 2O 3) catalysts showed high activity above 300 °C. The specific rates of Ca 3NiK 0.05O x , and LiMgO x were, however, higher than the specific rates of the commercial catalysts. The apparent activation energies for the conversion of carbon monoxide to carbon dioxide were 53 kJ/mol for CuZnO/Al 2O 3, 68 kJ/mol for LiMgO x , 86 kJ/mol for Ca 3NiK 0.05O x , 95 kJ/mol and 110 kJ/mol for the Fe 3O 4-Cr 2O 3 catalysts, 101 kJ/mol for Mo 19V 5Nb 1O x , and 132 kJ/mol for V 5Nb 1O x . For the commercial catalysts, the power-law rate model with concentration exponents of carbon monoxide and water close to one and zero, respectively, gave the best results. For V 5Nb 1O x , and Ca 3NiK 0.05O x , the concentration exponents of carbon monoxide and water close to 0.5 fit the results best. For Mo 19V 5Nb 1O x , the reaction was first order in carbon monoxide concentration whereas for LiMgO x , it was zero order in carbon monoxide concentration and 0.5 order in water concentration. Ca 3NiK 0.05O x and LiMgO x were active for the water-gas shift reaction in the temperature range of oxidative methane coupling. Thus, it is probable that the water-gas shift reaction can occur during methane coupling when these catalysts are used. The water-gas shift reaction is, however, unlikely to occur during the oxidative dehydrogenation of ethane since the conversions of carbon monoxide to carbon dioxide were very low at 350–500°C.

ChemInform Abstract: Oxydehydrogenation of Ethane over ZSM‐5 Zeolite Catalysts. Effect of Steam.

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