Reaction Of Propane Research Articles

A chemical link between saturated and unsaturated aldehydes and ketenes in the interstellar medium. Laboratory experiments on the H-atom reactions of propenal (CH2CHCHO) and propanal (CH3CH3CHO) at low temperatures

A chemical link between saturated and unsaturated aldehydes and ketenes in the interstellar medium. Laboratory experiments on the H-atom reactions of propenal (CH2CHCHO) and propanal (CH3CH3CHO) at low temperatures

Synthesis of sustainable aviation fuels via (co–)oligomerization of light olefins

Within this study, the (co–)oligomerization of methanol-based olefins in the C2-4 range was investigated. The main objective was to increase the yield of oligomers with carbon chain lengths in the range of kerosene (C9-16). Commercially available mesoporous amorphous mixed silicon-aluminum oxides, optionally modified with nickel species, were applied as catalysts. Initially, single olefin feeds were employed, i.e. homo-oligomerization reactions of pure propylene and pure 1-butylene were studied at 120 °C and 32 bar olefin partial pressure, respectively. The co-oligomerization of olefin mixtures (C3+4 and C2+3+4), which can be obtained in Methanol-to-Olefins (MtO) processes, yields product mixtures with reduced selectivities to specific chain lengths. However, selectivities to kerosene-like olefins up to 85 % have been achieved and the main side product is gasoline. Investigations with varying reaction conditions reveal comparable effects as in the case of homo-oligomerization. The use of nickel-free catalysts resulted in the highest selectivities of kerosene-like olefins, but no ethylene was converted. The negative effects of nickel catalysts on fuel quality can be compensated by two consecutive catalyst beds, the first catalyst bed with a nickel-loaded silicon-aluminum oxide for ethylene conversion followed by a catalyst bed of neat silicon-aluminum oxide for the synthesis of highly branched, long chain oligomers. The reaction network for olefin oligomerization reactions is depicted, which can be simplified remarkably in the case of catalysts without nickel. A long-term experiment lasting for more than 200 h was conducted revealing a deactivation of the acid sites of the catalysts, but also the possibility of reactivation. Selectivity to kerosene-like olefins remained above 63 % and fuel characterization showed that the resulting kerosene fraction will be suitable for blending with conventional fuels.

Performance Descriptor of Subsurface Metal-Promoted Boron Catalysts for Low-Temperature Propane Oxidative Dehydrogenation to Propylene.

Boron-based catalysts have exhibited excellent olefin selectivity in the oxidative dehydrogenation of propane (ODHP) reaction. The substrate material should be a potential platform for performance modulation of boron catalysts in this reaction since the introduction of subsurface Ni promoters significantly improves the activity. In this study, we deciphered the substrate effect and identified a performance descriptor to comprehend the roles of subsurface materials in BOx/metal/BN ODHP catalysts by evaluating different metal promoters. Performance evaluation and transient infrared spectroscopic experiments demonstrate that the intrinsic activity and kinetic behaviors of the O-H bond dissociation/regeneration on the metal-promoted BOx overlayer are metal substrate-dependent. Combining density functional theory (DFT) calculations, it is found that the dissociation/regeneration inclination of the O-H bond in BOx(OH)3-x active species is controlled by the affinity of H for boron oxide species. The metal-O binding energy, which has been demonstrated to be linearly correlated with H affinity, can serve as a straightforward performance descriptor for both low-temperature radical initialization and ODHP reaction, revealing this reaction is controlled by the Sabatier principle, and moderate metal-O binding energy is essential for achieving remarkable performance in the BOx/M/BN catalysts. Following the guidance of a potential descriptor, Ni-Rh alloy substrates are investigated and the substrate with a Ni/Rh molar ratio of 15:1 significantly enhances the low-temperature intrinsic activity of the metal-modified BOx to 9.26 μmol/(m2·s), which reaches 105.9 times that of h-BN and is 18.3% larger than the monometallic BOx/Ni/BN catalysts.

Applied Investigation of Methyl, Ethyl, Propyl, and Butyl Mercaptan as Potential Poisons in the Gas Phase Polymerization Reaction of Propylene.

The polypropylene (PP) synthesis process is crucial in the plastics industry, requiring precise control as it directly impacts the catalytic activity and the final product's performance. This study investigates the effects of trace amounts of four different mercaptans on the polymerization of propylene using a fourth-generation Ziegler-Natta (ZN) catalyst. Various concentrations of these mercaptans were tested, and results showed that their presence significantly reduced the melt flow index (MFI) of the final PP. The most notable MFI decrease occurred at 37.17 ppm of propyl mercaptan and 52.60 ppm of butyl mercaptan. Methyl and ethyl mercaptan also reduced the MFI at lower concentrations, indicating that mercaptans act as inhibitors by slowing down the polymerization process and reducing the fluidity of molten PP. The highest MFI increase was observed at lower concentrations of each mercaptan, suggesting that smaller molecular inhibitors require less concentration. This trend was also seen in the catalyst's productivity, where lower concentrations of methyl mercaptan reduced PP production more effectively than higher concentrations of butyl mercaptan. Fourier transform infrared spectroscopy (FTIR) identified interactions between the mercaptans and the ZN catalyst. Computational analysis further supported these findings, providing insights into the molecular interactions and suggesting possible inhibition mechanisms that could impact the final properties of polypropylene.

Mechanism Insights into Allylic Hydroxylation versus Epoxidation of Propene Catalyzed by Model Catalyst Iron Phthalocyanine in the Presence of Hydrogen Peroxide.

High-valent metal-oxo species are key reactive intermediates in many biological and biological oxidation reactions. Herein, allylic hydroxylation (C-H) versus epoxidation (C═C) reactions of propene with a model catalyst iron phthalocyanine (FePc) in the presence of hydrogen peroxide were investigated contrastively, aiming to probe the active intermediates, structure-activity relationship, and reaction pathways. Our results showed that H2O2 as an oxygen-donor reagent can be easily decomposed on FePc to produce key active intermediates O═FePc and O═FePc═O with the energy barriers of 19.57 and 23.89 kcal/mol, respectively. In the selective oxidation of propene, O═FePc has a small preference for C═C epoxidation over C-H hydroxylation while O═FePc═O has a small preference for C-H hydroxylation. Since the electron-withdrawing O axial ligand in O═FePc═O further increases the radical character (Fe-O·) and Fe-O bond length of the iron-oxo moiety, O═FePc═O has better catalytic performance in both C═C epoxidation and C-H hydroxylation than O═FePc. Furthermore, in the whole reaction processes, the dual-hydrogen bonds between the two terminal H atoms of the alkene and allylic groups of propene and oxygen atom of the iron-oxo moiety would lead to the reaction toward C═C epoxidation while the single-hydrogen bond between the terminal H atom of the allylic group and the oxygen atom of the iron-oxo moiety would lead to the reaction toward C-H hydroxylation, implying that the weakly interacting hydrogen bonds affecting oxidation pathways also play a very important role in the regioselectivity of C═C epoxidation and C-H hydroxylation.

The fabrication of potassium ion modification on Cu2O(111) for enhanced propylene oxide selectivity: Insights from density functional theory

Utilizing the alkali metal effect to enhance catalyst performance is an effective approach in the development of highly efficient catalysts. Herein, we report a K+ ion-modification strategy on Cu-based catalysts for the direct epoxidation of propylene (DEP) using molecular oxygen, a reaction deemed as one of the “dream reactions” in heterogeneous catalysis. By elaborately engineering of K+-modified Cu2O(111) catalyst, we unveil the versatile roles played by K+ ions in promoting catalytic performance for DEP. Firstly, K+ ions stabilize the surface coordination structures of Cu2O(111). Secondly, K+ ions make the dissociation of adsorbed O2* less likely, thus facilitating the reaction of propylene with O2*. Furthermore, both K+ and two-coordinated Cu+ serve as active centers in this reaction. Lastly, K+ ions create unique surface coordination structures favorable for propylene oxide (PO) formation. The density functional theory (DFT) calculations demonstrate that the effective utilization of the alkali metal effect can engineer highly efficient Cu-based catalysts for DEP.

Multiple Traces of Families of Epoxy Derivatives as New Inhibitors of the Industrial Polymerization Reaction of Propylene.

In this study, the impact of ethylene oxide, propylene oxide, 1,2-butene oxide, and 1,2-pentene oxide on the polymerization of propylene at an industrial level was investigated, focusing on their influence on the catalytic efficiency and the properties of polypropylene (PP) without additives. The results show that concentrations between 0 and 1.24 ppm of these epoxides negatively affect the reaction's productivity, the PP's mechanical properties, the polymer's fluidity index, and the PP's thermal properties. Fourier transform infrared spectroscopy (FTIR) revealed bands for the Ti-O bond and the Cl-Ti-O-CH2 bonds at 430 to 475 cm-1 and 957 to 1037 cm-1, respectively, indicating the interaction between the epoxides and the Ziegler-Natta catalyst. The thermal degradation of PP in the presence of these epoxides showed a similar trend, varying in magnitude depending on the concentration of the inhibitor. Sample M7, with 0.021 ppm propylene oxide, exhibited significant mass loss at both 540 °C and 600 °C, suggesting that even small concentrations of this epoxide can markedly increase the thermal degradation of PP. This pattern is repeated in samples with 1,2-butene oxide and 1,2-pentene oxide. These results highlight the need to strictly control the presence of impurities in PP production to optimize both the final product's quality and the polymerization process's efficiency.

Kinetic study of propane ODH on electrospun vanadium oxide-based submicron diameter fiber catalyst

A rigorous kinetic study of the oxidative dehydrogenation (ODH) reaction of propane on a vanadium oxide-based submicron diameter fiber catalyst has been developed. The proposed kinetic model simulates the conversion-selectivity profiles, the surface coverage of the different adsorbed species and the oxidation state of the catalyst for the studied operating conditions of temperature, space–time and inlet partial pressures of propane and oxygen. The activation energy of the rate determining step (RDS), the first hydrogen abstraction from propane, is 104 kJ·mol−1. The model predicts that although the reaction seems to be pseudo-zero order with respect to oxygen in a broad range of conditions, the catalyst may not be fully oxidized during reaction. The accuracy of the model when predicting the oxidation state of the catalyst has been experimentally confirmed by analyzing the catalytic fixed bed after reaction. The reduction degree of the catalyst will depend on its intrinsic chemical nature and reaction conditions, increasing with the space–time and in detriment of the overall reaction rate. Consequently, the propane turnover frequency (TOF) will also depend on the reaction conditions and space–time, even changing along the fixed-bed reactor.

Pairing Ga/Al-Zeolites with tailored acidity as tandem catalysts for the conversion of alcohols to olefins

Zeolites are versatile catalysts owing to their tunable acidity where the active site(s) can be placed within the crystal framework or as extra-framework species in confined pores. A common approach to tailor Brønsted acidity is heteroatom exchange involving the replacement of framework aluminum with alternative elements. Introduction of heteroatoms often results in less acidic catalysts that can be used in tandem reactions for targeted reactive intermediates. In this study, we prepare a series of three different zeolites with MWW, CHA, and MFI frameworks as aluminosilicates and gallosilicates to demonstrate their performance in alcohol dehydration reactions. The two reactions examined in this study are methanol conversion to dimethyl ether and ethanol conversion to ethylene. Our findings reveal that Ga-zeolites exhibit superior performance with Ga-MCM-22 (MWW) achieving nearly 100 % alcohol conversion and selectivity to desired products at contact times that are significantly less than most dehydration catalysts reported in literature. The unique properties of Ga-zeolites are attributed to their reduced acid site strength via a direct (one-pot) synthesis that avoids conventional time-intensive, multi-step post-synthesis modifications of Al-zeolites. Here we demonstrate the use of Ga-zeolites as tandem catalysts when paired with a downstream Al-zeolite in a dual-bed reactor configuration to convert cheaper reagents (alcohols) upstream to more desired intermediates as feeds for downstream catalysts to produce light olefins. We demonstrate that dual beds using Ga-zeolite – Al-ZSM-5 (upstream–downstream) pairings outperform single bed configurations with Al-ZSM-5 or a physical mixture (Ga-/Al-zeolite) for methanol to hydrocarbons reactions, with notable improvements in catalyst lifetime and increased light olefins selectivity. Similarly, dual beds using Ga-zeolite – Al-SSZ-13 (upstream–downstream) pairings result in improved performance for ethanol to propylene reactions with significant increases in propylene selectivity (>20 %) compared to a conventional single bed configuration of Al-SSZ-13. Overall, this study offers a new perspective on the use of heteroatom-exchanged zeolite catalysts in tandem reactions as a means of capitalizing on their reduced acid site strength and suggests differences in the intrinsic acidity of zeolite crystal structures.

Highly Anti-Markovnikov Selective Oxidative Arene Alkenylation Using Ir(I) Catalyst Precursors and Cu(II) Carboxylates.

The Ir(I) complex [Ir(μ-Cl)(coe)2]2 (coe = cis-cyclooctene) is a catalyst precursor for benzene alkenylation using Cu(II) carboxylate salts. Using [Ir(μ-Cl)(coe)2]2, propenylbenzenes are formed from the reaction of benzene, propylene, and CuX2 (X = acetate, pivalate, or 2-ethylhexanoate). The Ir-catalyzed reactions selectively produce anti-Markovnikov products, trans-β-methylstyrene, cis-β-methylstyrene, and allylbenzene, along with minor amounts of the Markovnikov product, α-methylstyrene. The selectivity for the anti-Markovnikov products changed as the reaction progressed. For example, in a reaction that uses 240 equiv of Cu(OHex)2 (related to Ir), the selectivity for the anti-Markovnikov products increases from 18:1 at 3 h to 42:1 at 42 h with 30 psig of propylene at 150 °C. Studies of product stability have revealed that the increase in the selectivity for anti-Markovnikov products is not the result of an isomerization process or the selective decomposition of specific products. Rather, the change in selectivity correlates with the ratio of Cu(II) to Cu(I) in the solution, which decreases as the reaction progresses. We propose that the identity of the active catalyst changes as Cu(I) is accumulated, resulting in the formation of an active catalyst that is more selective for anti-Markovnikov products. Using a 4:1 Cu(I)/Cu(II) ratio at the start of the reaction, a 65(3):1 anti-Markovnikov/Markovnikov ratio is observed.

Theoretical Study on Ethylamine Dissociation Reactions Using VRC-VTST and SS-QRRK Methods.

Barrierless bond dissociation reactions play an important role in fuel combustion. In this work, the pressure-dependent dissociation rate constants of ethylamine (EA) are accurately determined using variable-reaction-coordinate variational transition-state theory combined with the system-specific quantum Rice-Ramsperger-Kassel method. Before the kinetics calculations, the performances of four density functional theory methods in describing the bond dissociation of EA are evaluated against the benchmark method, FIC-MRCISD(T)+Q/cc-pVTZ, and the MN15-L/cc-pVTZ method is the best choice. By comparison of the Gibbs free energies and the rate constants for the bond dissociation reactions of EA, ethanol, and propane, the influence of functional groups on the reaction kinetics is discussed. The kinetics calculations show that the dissociation rate constants of EA are sensitive to pressure at low pressures and high temperatures, and the dominant channel is the reaction that yields C2H5 and NH2 radicals. A literature combustion model of EA is updated with our calculations, and the satisfactory agreement between the model predictions and reported ignition delay times of EA suggests the reliability of our calculations.

Advancements of MOFs in the Field of Propane Oxidative Dehydrogenation for Propylene Production.

Compared to the currently widely used propane dehydrogenation process for propylene production, propane oxidative dehydrogenation (ODHP) offers the advantage of no thermodynamic limitations and lower energy consumption. However, a major challenge in ODHP is the occurrence of undesired over-oxidation reactions of propylene, which reduce selectivity and hinder industrialization. MOFs possess a large number of metal sites that can serve as catalytic centers, which facilitates the easier access of reactants to the catalytic centers for reaction. Additionally, their flexible framework structure allows for easier adjustment of their pores compared to metal oxides and molecular sieves, which is advantageous for the diffusion of products within the framework. This property reduces the likelihood of prolonged contact between the generated propylene and the catalytic centers, thus minimizing the possibility of over-oxidation. The research on MOF catalyzed oxidative dehydrogenation of propane (ODHP) mainly focuses on the catalytic properties of MOFs with cobalt oxygen sites and boron oxygen sites. The advantages of cobalt oxygen site MOFs include significantly reduced energy consumption, enabling catalytic reactions at temperatures of 230 °C and below, while boron oxygen site MOFs exhibit high conversion rates and selectivity, albeit requiring higher temperatures. The explicit structure of MOFs facilitates the mechanistic study of these sites, enabling further optimization of catalysts. This paper provides an overview of the recent progress in utilizing MOFs as catalysts for ODHP and explores how they promote progress in ODHP catalysis. Finally, the challenges and future prospects of MOFs in the field of ODHP reactions are discussed.

O2 and CO2 assisted oxidative dehydrogenation of propane using ZrO2 supported vanadium and chromium oxide catalysts

Zirconia supported vanadium oxide (vanadia) and chromium oxide (chromia) catalysts of 1–3 wt% of V or Cr were prepared, characterized, and tested for the oxidative dehydrogenation (ODH) of propane (C3H8) with O2 and CO2. Characterization results reveal that 2.5% metal loading is in slight excess of monolayer loadings for this ZrO2, which has a surface area of 48 m2.g−1. The reaction results reveal that supported vanadia catalysts are better for O2-ODH and supported chromia catalyst are better for CO2-ODH at a reaction temperature of 550 °C. Furthermore, the C3H8 conversion and propene (C3H6) yield increases with loading and the highest conversion and yield are also achieved at 2.5% metal loading. With higher loadings the conversion and yield decreases, clearly indicating that the surface metal oxide species are more active than their crystalline counterparts. As the contact time increases, for inlet stoichiometric ratios of the reactants for the two reactions, C3H8/CO2 = 1 and C3H8/O2 = 2, C3H8 conversion and C3H6 yield both monotonically increase and appear to approach a constant value; however, the difference between C3H8 conversion and C3H6 yield also increases. The C3H6 selectivity during O2-ODH (∼30%) is much lower than C3H6 selectivity during CO2-ODH (86–94%). Furthermore, during CO2-ODH of propane the conversions of C3H8 and CO2 are similar, and it appears that under the operating conditions used, the dry reforming of propane does not occur. Overall, the CO2-ODH of propane reaction at 550 °C using stoichiometric ratios of C3H8/CO2 over ZrO2 supported chromia catalyst provides a better C3H6 yield and selectivity, with an additional advantage of converting CO2.

Biomolecule-derived three-dimensional N, P co-doped carbon nanosheets for the efficient oxidative dehydrogenation of propane.

Non-metallic heteroatom-doped carbon materials are promising catalysts for the oxidative dehydrogenation of propane (ODHP), but their controlled synthesis remains challenging. Herein, a novel three-dimensional N, P co-doped carbon nanosheet (NPC-NS-T) catalyst is prepared, which shows an impressive catalytic performance in the ODHP reaction with high propane conversion (20.0%) and high selectivity for propene (62.1%) and olefins (64.5%) at 500 °C along with good long-time stability. Comprehensive experimental characterizations revealed that incorporation of appropriate P can not only help to form more CO species on the surface of NPC-NS-T but also inhibit the consumption of CO species under ODHP conditions, thereby remarkably improving the catalytic performance. This work could pave the way for developing efficient biomass-derived carbon catalysts for the oxidative dehydrogenation reactions of propane.

Metal-doped M-NH4-PW catalyst with enhanced electron transfer for formaldehyde-propylene condensation to 4-methyl-1,3-dioxane

Recognizing and modifying the acid property-dependent catalytic characteristics of catalysts are of great importance for Prins condensation reaction. Herein, a series of metal-doped M-NH4-PW catalysts (M=Pt, Fe, Ir, Ru) are successfully synthesized for Prins condensation reaction of formaldehyde and propylene to produce 4-methyl-1,3-dioxane. Our findings demonstrate that the catalytic performance of M-NH4-PW catalysts is influenced by the chemical nature of metal site properties with different electron transfer abilities. Specifically, the new Lewis acid decorated by Pt metal on 4-H site is more favorable for the selective adsorption of formaldehyde and activation of its CO bond. Additionally, the synergistic effect between Pt metal sites and nearby O in [PW12O40]3− promotes the formation of CC bonds between protonated formaldehyde and propylene. Consequently, the Pt-NH4-PW catalyst exhibits high conversion (> 80 %) and simultaneous selectivity towards 4-methyl-1,3-dioxane selectivity (65 %). This strategy may provide valuable insights for developing efficient multifunctional catalysts for Prins condensation reactions.

Secondary reactions of propylene on Ga/γ-Al2O3 propane dehydrogenation catalysts

Supported Ga catalysts have been widely studied for propane dehydrogenation (PDH). In this study, Ga/γ-Al2O3 catalysts were evaluated for PDH. The propylene selectivity decreased with increasing propane conversion. It is generally thought that propylene and light gas by-products occur from chemisorbed propane and are, therefore, primary products. By extrapolating the product selectivities to zero per cent propane conversion, the initial propylene selectivity was near 100% and is a primary product. The light gas selectivities, however, are near 0% indicating that these are secondary products. The direct reaction of propylene produced the same light gas products, e.g., methane, ethylene, propane, butenes and pentenes, observed for PDH and confirmed that these occur by an independent reaction of propylene. Thus, while the intrinsic PDH propylene selectivity is high, these secondary propylene reactions lower the selectivity, especially, at higher conversions and higher partial pressures.

Ultrathin 3D CoMn nanoflowers coupled diatomite for highly efficient catalytic oxidation of CO and propane

Manganese oxides are promising catalysts for the treatment of VOC gas pollutants due to variable valences and abundant oxygen vacancies. The surface properties of manganese oxides significantly affect their catalytic activity. Thus, the development of appropriate modulation strategies for manganese oxides is of great significance. Herein, ultrathin (1–2 nm) three-dimensional (3D) CoMn nanoflowers have been in-situ planted on the surface of a naturally abundant resource – diatomite. Due to the open diffusion channels of diatomite and 3D coordination of CoMn nanoparticles, more open space and exposed sites are created for the transport and migration of O2, CO and propane. Compared to the pure CoMn, the obtained cobalt-manganese/diatomite (CoMn/Dia) composite contains more surface defect sites and oxygen vacancies, resulting in 90 % of carbon monoxide (CO) and propane (C3H8) conversion at as low as 108 °C and 250 °C, respectively. Density functional theory (DFT) results demonstrate that the doping of Co elements and the ultrathin structure of CoMn nanoflowers induce the formation of oxygen vacancies and weaken the Mn-O-Co bond in CoMn/Dia composites, which significantly accelerate the oxygen cycling during the oxidation reactions of CO and propane. In addition, the prepared CoMn/Dia catalyst exhibits excellent stability with consistent catalytic efficiency achieved for 70 h. Due to the simple synthesis method and lower cost raw materials, this research provides new insight into the scale-up production of efficient and economical Mn-based catalysts.

Rationalizing kinetic behaviors of isolated boron sites catalyzed oxidative dehydrogenation of propane

Boron-based catalysts exhibit high alkene selectivity in oxidative dehydrogenation of propane (ODHP) but the mechanistic understanding remains incomplete. In this work, we show that the hydroxylation of framework boron species via steaming not only enhances the ODHP rate on both B-MFI and B-BEA, but also impacts the kinetics of the reaction. The altered activity, propane reaction order and the activation energy could be attributed to the hydrolysis of framework [B(OSi≡)3] unit to [B(OSi≡)3−x(OH···O(H)Si≡)x] (x = 1, 2, “···” represents hydrogen bonding). DFT calculations confirm that hydroxylated framework boron sites could stabilize radical species, e.g., hydroperoxyl radical, further facilitating the gas-phase radical mechanism. Variations in the contributions from gas-phase radical mechanisms in ODHP lead to the linear correlation between activation enthalpy and entropy on borosilicate zeolites. Insights gained in this work offer a general mechanistic framework to rationalize the kinetic behavior of the ODHP on boron-based catalysts.

Selective Oxidative Dehydrogenation of Ethane and Propane over Copper‐Containing Mordenite: Insights into Reaction Mechanism and Product Protection

AbstractCopper(II)‐containing mordenite (CuMOR) is capable of activation of C−H bonds in C1‐C3 alkanes, albeit there are remarkable differences between the functionalization of ethane and propane compared to methane. The reaction of ethane and propane with CuMOR results in the formation of ethylene and propylene, while the reaction of methane predominantly yields methanol and dimethyl ether. By combining in situ FTIR and MAS NMR spectroscopies as well as time‐resolved Cu K‐edge X‐ray absorption spectroscopy, the reaction mechanism was derived, which differs significantly for each alkane. The formation of ethylene and propylene proceeds via oxidative dehydrogenation of the corresponding alkanes with selectivity above 95 % for ethane and above 85 % for propane. The formation of stable π‐complexes of olefins with CuI sites, formed upon reduction of CuII‐oxo species, protects olefins from further oxidation and/or oligomerization. This is different from methane, the activation of which proceeds via oxidative hydroxylation leading to the formation of surface methoxy species bonded to the zeolite framework. Our findings constitute one of the major steps in the direct conversion of alkanes to important commodities and open a novel research direction aiming at the selective synthesis of olefins.

Selective Oxidative Dehydrogenation of Ethane and Propane over Copper-Containing Mordenite: Insights into Reaction Mechanism and Product Protection.

Copper(II)-containing mordenite (CuMOR) is capable of activation of C-H bonds in C1 -C3 alkanes, albeit there are remarkable differences between the functionalization of ethane and propane compared to methane. The reaction of ethane and propane with CuMOR results in the formation of ethylene and propylene, while the reaction of methane predominantly yields methanol and dimethyl ether. By combining in situ FTIR and MAS NMR spectroscopies as well as time-resolved Cu K-edge X-ray absorption spectroscopy, the reaction mechanism was derived, which differs significantly for each alkane. The formation of ethylene and propylene proceeds via oxidative dehydrogenation of the corresponding alkanes with selectivity above 95 % for ethane and above 85 % for propane. The formation of stable π-complexes of olefins with CuI sites, formed upon reduction of CuII -oxo species, protects olefins from further oxidation and/or oligomerization. This is different from methane, the activation of which proceeds via oxidative hydroxylation leading to the formation of surface methoxy species bonded to the zeolite framework. Our findings constitute one of the major steps in the direct conversion of alkanes to important commodities and open a novel research direction aiming at the selective synthesis of olefins.