Chemical Looping Oxidative Dehydrogenation Research Articles

Molten-Salt-Mediated Chemical Looping Oxidative Dehydrogenation of Ethane with In-Situ Carbon Capture and Utilization.

The molten-salt-mediated oxidative dehydrogenation (MM-ODH) of ethane (C2H6) via a chemical looping scheme represents an effective carbon capture and utilization (CCU) method for the valorization of ethane-rich shale gas and concurrent mitigation of carbon dioxide (CO2) emissions. Here, stepwise experimentation with Li2CO3-Na2CO3-K2CO3 (LNK) ternary salts (i) assessed how each component of the LNK mixture impacted ethane MM-ODH performance and (ii) explored physicochemical and thermodynamic mechanisms behind melt-induced changes to ethylene (C2H4) and carbon monoxide (CO) yields. Of fifteen screened LNK compositions, nine exhibited ethylene yields greater than 50 % at 800 °C while maintaining C2H4 selectivities of 85 % or higher. LNK salts rich in Li2CO3 content yielded more ethylene and CO on average than their counterparts, and net CO2 capture per cycle reached a maximum of ~75 %. Extended MM-ODH cycling also demonstrated long-term stability of a high-performing LNK medium. Density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations suggested that the molten salt does not directly activate C2H6. Meanwhile, an empirical model informed by experimental data and reaction thermodynamics adequately predicted overall MM-ODH performance from LNK composition and provided insights into the system's primary drivers.

Interface engineering to construct heterostructured MoO3/SmMn2O5 for chemical looping oxidative dehydrogenation of ethane

Electronic structure and lattice oxygen in metal oxides play important roles in the chemical looping oxidative dehydrogenation of ethane. Herein, an interface strategy is proposed to tailor electronic structure and activate lattice oxygen of mullite SmMn2O5 via the interface fabrication with MoO3 for enhancing the reactivity of the sample. The optimized 2MoO3/SmMn2O5 oxygen carrier exhibited 50 % ethane conversion and 83.9 % ethylene selectivity higher than that of pure SmMn2O5 and pure MoO3. Density functional theory simulations and characterization results revealed that the interface of MoO3/SmMn2O5 regulated the d-band center, which tailored the adsorption of ethane. Besides, the interface of MoO3/SmMn2O5 also caused the charge transfer from Mn atoms in SmMn2O5 to O atoms in MoO3 and SmMn2O5, leading to a reduction of the Mn-O bond strength and an enhancement in the activity of the lattice oxygen and Oads. This study provides useful insights to regulate electronic structure and activate lattice oxygen of oxygen carrier through interfacial engineering for the practical application of ethane chemical looping oxidative dehydrogenation.

Enhancement of ethylene selectivity in chemical looping oxidative dehydrogenation of ethane using manganese-based redox catalysts supported on HY zeolite

As the crucial role of zeolite catalysts becomes increasingly prominent in refining and petrochemical industries, this study introduces a novel application of xMn / HY catalysts in ethane catalytic dehydrogenation via Chemical Looping Oxidative Dehydrogenation (CL-ODH). The synergistic effect of manganese oxides on the HY framework and a moderate amount of acidic sites within the catalyst facilitates the cleavage of C-H bonds and the desorption of olefins, which are vital for advancing ethane CL-ODH. We identified the reasons for maintaining high ethylene selectivity using advanced characterization techniques such as XRD, SEM, TEM, BET, H2-TPR, NH3-TPD, and Py-IR. Notably, under optimized conditions at 700 °C with a gas time-space velocity (GHSV) of 1800 mL·h−1·g−1, the 3Mn/HY catalyst achieved approximately 97.1 % selectivity for ethylene and a 22.7 % conversion of ethane. These findings present a scalable route for ethylene production, showcasing significant industrial relevance by potentially reducing energy costs and improving yield.

Impact of B-site cations of MgX2O4 (X=Cr, Fe, Mn) spinels on the chemical looping oxidative dehydrogenation of ethane to ethylene

Chemical looping oxidative dehydrogenation (CL-ODH) provides a multifunctional conversion platform that can take advantage of the selective oxidation of lattice oxygen in oxygen carrier to achieve high-valued ethane to ethylene conversion. In this study, we explored the effect of B-site element in MgX2O4 (X=Cr, Fe, or Mn) spinel-type oxygen carriers on the performance of ethane CL-ODH. The properties test and characterization of MgX2O4 spinel were tested by fixed bed and H2-TPR, O2-TPD, TG, in-situ Raman, SEM, and TEM. The results showed that because MgCr2O4 only released a small amount of adsorbed surface oxygen, it tended to catalyze the conversion of ethane to coke and hydrogen. MgFe2O4 facilitated the deep oxidation of ethane into CO2 by providing more surface lattice oxygen. Meanwhile, since a significant amount of bulk lattice oxygen was released by the MgMn2O4 oxygen carrier, it could burn hydrogen in a targeted manner to advance the reaction and increased ethylene’s selectivity. Thereby, MgMn2O4 achieved an ethane conversion of 73.72% with an ethylene selectivity of 81.46%. Furthermore, the MgMn2O4 catalyst demonstrated stable reactivity and an ethylene yield of about 62.00% in ethane CL-ODH over the 30 redox cycles. The screening tests indicated that the B-site elements in MgX2O4 spinel oxides could significantly influence their ability to supply lattice oxygen, thereby affecting their performance in ethane CL-ODH reaction.

Unraveling the role of single-atom metal dopant over CeO2 catalyst in tuning catalytic performance of ethane oxidative dehydrogenation

Single-atom metal doped CeO2 (M1@CeO2) catalysts have exhibited better catalytic performance in methane and propane dehydrogenation, which may be applied to ethane dehydrogenation, revealing structure-activity relationship of M1@CeO2 catalysts is of great importance. In this work, DFT + U calculations together with kinetic Monte Carlo simulations were implemented to investigate the oxidative dehydrogenation stage (ODH) in ethane chemical looping-oxidative dehydrogenation (CL-ODH) over thirteen types of M1@CeO2 catalysts (M = Cr, Mn, Fe, Co, Ni, Ga, Mo, Ru, Rh, Pd, In, Ir and Pt). The results show that the doped single-atom metal and its adjacent O atoms act as active sites over four catalysts Rh, Pd, Ir and Pt doped CeO2, while only O atoms act as active sites over other nine catalysts M1@CeO2. Rh1@CeO2 was screened out to perform higher C2H4(g) selectivity of 98.8 % and C2H4(g) formation activity of 8.72×103 s−1 site−1 at 823.15 K with C2H6(g) partial pressure <0.2 bar, which is superior to the previously reported catalysts Pt, Pt3Sn, Pt3Ir, Ni3Mo, Co/g-C3N4 and Rh/ZrO2, and so on. A quantitative and quick descriptor, the binding strength of C2H5* intermediate is proposed to evaluate C2H4(g) formation activity. This study unravels the role of doped single-atom metal over CeO2 catalyst and help rationally design high-efficiency alkane dehydrogenation.

Binary Li/Na tungstates modified Mg6MnO8 as redox catalysts for enhanced performance of chemical looping oxidative dehydrogenation of ethane

The present investigation delves into the utilization of Mg6MnO8 modified with binary Li2WO4 and Na2WO4 tungstates as oxygen carriers for the chemical looping oxidative dehydrogenation (CL-ODH) of ethane. The Mg6MnO8-LiNaW2 oxygen carrier demonstrates remarkable performance, achieving up to 77.7 % ethane conversion, 86.5 % ethylene selectivity, and 67.2 % ethylene yield. HRTEM-EDS reveals the formation of a molten binary tungstates layer covering the solid Mg6MnO8 substrate. The molten binary tungstates layer effectively modulates the release of lattice oxygen in a step-wise manner during ODH reactions. XPS analysis reveals that the doping of Li/Na binary tungstates inhibits the formation of OH−/CO32− and Mn4+ species, thus preventing the deep oxidation of ethylene. The Mg6MnO8-LiNaW2 sample maintains stable reactivity and surface morphology throughout 20 redox cycles. DFT calculations further indicate that the modification with Li/Na binary tungstates promotes electron accumulation around the local environment of the Me-O bond, thereby reducing the formation energy (Eo) of oxygen vacancy in Mg6MnO8 and improving the oxygen vacancy concentration within the bulk of the oxygen carriers. The superior ethylene selectivity of the Mg6MnO8-LiNaW2 oxygen carrier can be attributed to the higher oxygen diffusion capability in the bulk of the Mg6MnO8 core, coupled with the lower oxygen transport rate through the molten tungstates layer.

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.

Oxygen carrier prepared by solvent-free grinding and biomass based oxygenates for chemical looping oxidative dehydrogenation of isobutane

The chemical looping oxidative dehydrogenation of isobutane is an effective and novel strategy for producing isobutene. It is extremely necessary but challenging to design excellent oxygen carriers for this strategy. Here, a solvent-free grinding approach is presented to prepare ZnMo0.45V0.55Ox oxygen carrier with tailorable oxygen vacancy content via biomass based oxygenate as carbothermal reductive agent. As a result, ZnMo0.45V0.55Ox-0.3 vitamin C oxygen carrier demonstrates a much higher isobutane conversion of 17.61 % and isobutene selectivity of 82.55 %, whereas it is 7.99 % of isobutane conversion and 22.66 % of isobutene selectivity for ZnMo0.45V0.55Ox without vitamin C addition. The performance for the ZnMo0.45V0.55Ox-0.3 vitamin C is closely related to the surface area and the metal-oxygen bond strength. Large surface area can provide more accessible active sites, which can facilitate the isobutane's diffusion, adsorption and activation. High oxygen vacancy content results in weak metal-oxygen bond strength, which leads to high mobility of lattice oxygen.

Halide ions doped SrMnO3 for chemical looping oxidative dehydrogenation of ethane

AbstractThe 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 &amp; Sons, Ltd.

Role of oxygen transfer and surface reaction in catalytic performance of VOx-Ce1–xZrxO2 for propane dehydrogenation

The bulk oxygen transfer and surface reaction as important parts of the chemical looping-related process are crucial for the rational design of new redox catalysts. This paper describes an experimental study on the effect of bulk oxygen transfer and surface reaction in Ce1–xxO2 supported VOx redox catalysts for the chemical looping oxidative propane dehydrogenation reaction. It was found that the introduction of Zr dictates the reaction performance of the redox catalyst by modulating the bulk oxygen transfer and surface reaction. The kinetic study reveals that the instantaneous reduction rate of the redox catalysts is determined by the H-abstraction step in the surface reaction. The introduction of Zr can reduce the activation energy of the H-abstraction step, which leads to the enhancement of the instantaneous reduction rate. Meanwhile, the oxygen supply capacity of the cerium oxide is increased by Zr, allowing the surface reaction to proceed over longer durations. Furthermore, the reaction model derived from the kinetics study is validated using a number of (quasi) in situ techniques. This study provides fundamental insights into the role of bulk oxygen transfer and surface reaction in chemical looping or related process.

Regulating lattice oxygen mobility of FeOx redox catalyst via W-doping for enhanced chemical looping oxidative dehydrogenation of ethane

The precise regulation of lattice oxygen mobility toward matched surface reaction kinetics is the key issue for rational design of chemical looing oxygen carriers. Herein, we successfully regulated lattice oxygen reactivity of FeOx redox catalyst via a W-doping strategy to realize efficient chemical looping oxidative dehydrogenation (CL-ODH) of ethane to ethylene. Specifically, the addition of W could significantly increase the binding energy of Fe-O bond, inhibiting the over-quick lattice oxygen migration toward over-oxidation. On this basis, the mild reduction of active Fe3O4 and slowly released oxygen ions involving in dehydrogenation at a matched kinetic rate could greatly prolong the active period, leading to a record high ethane processing capacity (120 ml·gcat−1·cycle−1) and productivity of ethylene (selectivity ∼83 %) during continuous dehydrogenation-regeneration cycles. This work provides a highly active CL-ODH catalyst and new insight into metal oxide redox chemistry.

Lattice Oxygen Regulation of Perovskites for Chemical Looping Oxidative Dehydrogenation of Ethylbenzene to Styrene

The direct dehydrogenation process produces over 90% of global styrene. However, it is hampered by high energy consumption due to equilibrium limitation, a high steam/ethylbenzene feeding ratio, and complicated separation procedures. In this study, we propose the synthesis of a novel perovskite-structured metal oxide as the redox catalyst for chemical looping oxidative dehydrogenation (CL-ODH) of ethylbenzene into styrene. Lower ethylbenzene activation temperature and higher oxygen storage capacity contributing to high ethylbenzene conversion are achieved by Mn doping of the B site in SrFeO3−δ, and styrene yield is further enhanced by Ba doping of the A site. The optimized Sr0.8Ba0.2Fe0.2Mn0.8O3−δ catalyst exhibits favorable dehydrogenation activity but is deactivated in the first five redox cycles due to the severe carbonation and perovskite structure decomposition. The decarbonization treatment on the catalyst at 950 °C in an O2 atmosphere restores the perovskite structure and dehydrogenation activity, resulting in 85% ethylbenzene conversion and 89% styrene selectivity at 550 °C. Ethylbenzene on the catalyst undergoes full combustion via adsorbed oxygen, ODH of ethylbenzene into styrene and H2O using lattice oxygen, and direct dehydrogenation without available lattice oxygen. The proposed redox catalyst demonstrates efficient conversion of ethylbenzene into styrene, showing great potential for the energy conservation and process intensification of styrene production.

Molybdenum-based oxygen carrier for chemical looping oxidative dehydrogenation of isobutane

Compared with steam cracking, oxidative dehydrogenation of isobutane to produce isobutene has advantages, but its application is limited by capital intensive air separation needed to provide O2. A chemical looping oxidative dehydrogenation strategy for isobutane to isobutene is proposed to tackle this problem, in which the oxygen carrier provides lattice oxygen. The synthesis of the oxygen carrier from the perspective of electronic structure and metal–oxygen bond strength is highly desirable to enhance the performance of the chemical looping oxidative dehydrogenation of isobutane. Herein, the electronic structure and metal–oxygen bond strength of a Mo-based oxygen carrier are regulated by doping Zn, V and Mg. The results show that Mg0.2Zn0.8Mo0.45V0.55Ox with 35% isobutane conversion and 82% isobutene selectivity is superior to MoO3, ZnMoOx and ZnMo0.45V0.55Ox. It indicates that the electronic structure and metal–oxygen bond strength via doping Zn, V and Mg are responsible for the promoted performance of Mg0.2Zn0.8Mo0.45V0.55Ox. This study provides important insights for the oxygen carrier design and optimization through regulating electronic structure and metal–oxygen bond strength.

Numerical modeling of chemical looping oxidative dehydrogenation of ethane in parallel packed beds

Chemical looping oxidative dehydrogenation (CL-ODH) of ethane has the potential to be a highly efficient alternative to steam cracking for ethylene production. Accurate reactor modeling is of critical importance to efficiently scale up and optimize this new technology. This study reports a one-dimensional, heterogeneous packed bed model to simulate the CL-ODH of ethane to ethylene with a Na2MoO4-promoted CaTi0.1Mn0.9O3 redox catalyst. The overall reaction kinetics was well-described by coupling the gas-phase steam cracking of ethane with the reduction kinetics of the redox catalyst by H2 and C2H4. The impact of H2 on the formation rate of CO2 byproduct from C2H4 conversion was also thoroughly investigated to validate the applicability of the kinetic model under operational environments. The temperature variation within the different CL-ODH steps and the temperature distribution along the bed were also carefully considered. The accuracy of the model was validated by experiments conducted in a large lab-scale packed bed reactor (200 g catalyst loading), with an average deviation of 2.8% in terms of ethane conversion and ethylene yield. The model was subsequently used to optimize the operating parameters of the CL-ODH reactor, indicating that up to 63.7% single-pass C2 + olefin yield can be achieved with the current redox catalyst bed whereas further optimization of the redox catalyst to inhibit C2H4 activation can result in 69.4% single-pass C2 + yield while maintaining low CO2 selectivity.

Effect of Ce Content on the Chemical Looping Oxidative Dehydrogenation of Propane to Propylene over a VOx-CeO2/γ-Al2O3 Oxygen Carrier

The chemical looping oxidative dehydrogenation of propane to propylene (CL-ODHP) replaces molecular oxygen with lattice oxygen (Olatt) in oxygen carriers. This method boosts propylene selectivity by avoiding the deep oxidation of propane. Herein, a series of 10V-XCe/Al oxygen carriers with different Ce contents were prepared to realize different VOx-CeOy interactions. The effect of the Ce content in 10V-XCe/Al oxygen carriers on the CL-ODHP reaction was studied and the optimal Ce content was determined. CeO2 prevents the outward diffusion and evolution of Olatt in VOx carriers to the adsorbed electrophilic oxygen species (Oelec), effectively inhibiting the loss of Olatt, improving the selectivity of propylene, and extending the lifetime and activity of the oxygen carriers. After characterizing and analyzing the oxygen carriers, it was found that 10V-3Ce/Al has the highest specific surface area, highest oxygen capacity, and lowest reducibility. The 10V-3Ce/Al also delivers the highest oxidative dehydrogenation performance. At 550 °C, the average propylene and COx selectivity values of 10V-3Ce/Al were 81.87% and 7.28%, respectively (vs. 62.79% and 25.64% respectively, for 10V/Al). It is demonstrated that 10V-3Ce/Al exhibits good cycle stability with no significant decrease in catalytic performance after 15 cycles. In situ diffuse-reflectance infrared Fourier-transform spectroscopy indicates that CL-ODHP on 10V-3Ce/Al undergoes the Mars-van Krevelen mechanism. The migration and evolution of Olatt in oxygen carriers is controlled by reasonably modifying the metal oxide interactions to improve propylene yield. This work will thus guide the subsequent development of novel and efficient CL-ODHP oxygen carriers.

Research Progress on Propylene Preparation by Propane Dehydrogenation.

At present, the production of propylene falls short of the demand, and, as the global economy grows, the demand for propylene is anticipated to increase even further. As such, there is an urgent requirement to identify a novel method for producing propylene that is both practical and reliable. The primary approaches for preparing propylene are anaerobic and oxidative dehydrogenation, both of which present issues that are challenging to overcome. In contrast, chemical looping oxidative dehydrogenation circumvents the limitations of the aforementioned methods, and the performance of the oxygen carrier cycle in this method is superior and meets the criteria for industrialization. Consequently, there is considerable potential for the development of propylene production by means of chemical looping oxidative dehydrogenation. This paper provides a review of the catalysts and oxygen carriers employed in anaerobic dehydrogenation, oxidative dehydrogenation, and chemical looping oxidative dehydrogenation. Additionally, it outlines current directions and future opportunities for the advancement of oxygen carriers.

Coupling acid catalysis and selective oxidation over MoO3-Fe2O3 for chemical looping oxidative dehydrogenation of propane

Redox catalysts play a vital role in chemical looping oxidative dehydrogenation processes, which have recently been considered to be a promising prospect for propylene production. This work describes the coupling of surface acid catalysis and selective oxidation from lattice oxygen over MoO3-Fe2O3 redox catalysts for promoted propylene production. Atomically dispersed Mo species over γ-Fe2O3 introduce effective acid sites for the promotion of propane conversion. In addition, Mo could also regulate the lattice oxygen activity, which makes the oxygen species from the reduction of γ-Fe2O3 to Fe3O4 contribute to selectively oxidative dehydrogenation instead of over-oxidation in pristine γ-Fe2O3. The enhanced surface acidity, coupled with proper lattice oxygen activity, leads to a higher surface reaction rate and moderate oxygen diffusion rate. Consequently, this coupling strategy achieves a robust performance with 49% of propane conversion and 90% of propylene selectivity for at least 300 redox cycles and ultimately demonstrates a potential design strategy for more advanced redox catalysts.

CrOx/Ce1−xZrxO2 for chemical looping propane oxidative dehydrogenation: The redox interaction between CrOx and the support

Propane dehydrogenation is an attractive alternative for propylene production to petroleum-based routes. However, overcoming deactivation and toxicity of catalysts in propane direct dehydrogenation (PDH), and over oxidation in oxidative dehydrogenation (ODHP) remain challenging. Here, a chromium-based catalyst supported on a Ce-Zr solid solution is constructed for chemical looping oxidative propane dehydrogenation (CL-ODHP). A dual modulation of oxygen species by Zr doping was unraveled by characterizations and DFT calculation: the oxygen of surface CrOx was constrained while the oxygen mobility of the Ce-Zr support was promoted. Based on these properties, the interaction between surface CrOx and the support further enables an oxygen “donor–acceptor”, which potentially functions as in situ activation and regeneration of redox CrOx species as well as blockage of non-selective oxygen released from the Ce-Zr support. The optimized material (7.5Cr/Ce0.8Zr0.2O2) achieves propane conversion up to 50% and propylene yield of 31% at 600 °C, and has the lowest Cr content among previously reported Cr-based catalysts that have comparable performance. These results provide insights for the design of highly active and selective redox catalysts for chemical looping as a reaction engineering strategy for the upgrading of propane dehydrogenation processes.

Unraveling the Surface State Evolution of IrO2 in Ethane Chemical Looping Oxidative Dehydrogenation

Based on the advantages of favorable thermodynamics and coking resistance of ethane oxidative dehydrogenation and the challenge of low ethylene selectivity, chemical looping oxidative dehydrogenation (CL-ODH) over the IrO2 catalyst was examined, including the dehydrogenation and regeneration processes. The stoichiometric S-IrO2 and reduced R-IrO2 catalysts as two extreme states of the IrO2 surface structure with dynamic changes were considered. Density functional theory (DFT) calculations and kinetic Monte Carlo simulations showed that the mechanisms of ethane dehydrogenation over S-IrO2 and R-IrO2 catalysts were quite different. Over the S-IrO2 catalyst, ethane oxidative dehydrogenation to C2H4(g) with H2O(g), CO(g), and CO2(g) taking away surface lattice oxygen, followed by lattice oxygen migration from the bulk to the surface, leads to the reduction of the S-IrO2 catalyst. Over the R-IrO2 catalyst, ethane directly dehydrogenates to C2H4(g) and H2(g). Furthermore, the oxidation degree in the regeneration process is greater than the Ov concentration in the dehydrogenation process, which can easily achieve oxygen replenishment in the regeneration process. More importantly, the IrO2 catalyst can be neither completely reduced in the dehydrogenation process nor completely oxidized in the regeneration process, both S-IrO2 and R-IrO2 simultaneously exist for the IrO2 catalyst, and both 750 K and 0.8 bar C2H6(g) pressure were obtained to be the optimal reaction conditions; thus, for ethane CL-ODH over the IrO2 catalyst, the proposed mechanism starts from the oxidative dehydrogenation process; with the consumption of surface lattice oxygen and the oxygen migration from the bulk to the surface, the oxidative and nonoxidative dehydrogenations occur simultaneously until the regeneration. The present study broadens the understanding of ethane CL-ODH over metal oxide catalysts and provides valuable information for the optimization of the CL-ODH process and the development of other high-performance metal oxide catalysts in other alkane CL-ODH processes.

Ce-Doped LaMnO3 Redox Catalysts for Chemical Looping Oxidative Dehydrogenation of Ethane

As a novel reaction mode of oxidative dehydrogenation of ethane to ethylene, the chemical looping oxidative dehydrogenation (CL-ODH) of ethane to ethylene has attracted much attention. Instead of using gaseous oxygen, CL-ODH uses lattice oxygen in an oxygen carrier or redox catalyst to facilitate the ODH reaction. In this paper, a perovskite type redox catalyst LaMnO3+δ was used as a substrate, Ce3+ with different proportions was introduced into its A site, and its CL-ODH reaction performance for ethane was studied. The results showed that the ratio of Mn4+/Mn3+ on the surface of Ce-modified samples decreased significantly, and the lattice oxygen species in the bulk phase increased; these were the main reasons for improving ethylene selectivity. La0.7Ce0.3MnO3 showed the best performance during the ODH reaction and showed good stability in twenty redox cycle tests.