Bond In Ethane Research Articles

Main-group compounds selectively activate natural gas alkanes under room temperature and atmospheric pressure

Most C–H bond activations of natural gas alkanes rely on transition metal complexes. Activations by using main-group systems have been reported but required heating or photo-irradiation under high atmospheric pressure with rather low regioselectivity. Here we report that Lewis acid-carbene adducts facilely undergo oxidative additions to C–H bonds of ethane, propane and n-butane with high selectivity under room temperature and atmospheric pressure. The Lewis acids can be moved by the addition of a base and the carbene-derived products can be easily converted into aldehydes. This work offers a route for main-group element compounds to selectively functionalise C–H bonds of natural gas alkanes and other small molecules.

Isolated Pt Atoms Stabilized by Ga2O3 Clusters Confined in ZSM-5 for Nonoxidative Activation of Ethane.

Selective activation of light alkanes is an essential reaction in the petrochemical industry for producing commodity chemicals, such as light olefins and aromatics. Because of the much higher intrinsic activities of noble metals in comparison to non-noble metals, it is desirable to employ solid catalysts with low noble metal loadings to reduce the cost of catalysts. Herein, we report the introduction of a tiny amount of Pt (at levels of hundreds of ppm) as a promoter of the Ga2O3 clusters encapsulated in ZSM-5 zeolite, which leads to ∼20-fold improvement in the activity for ethane dehydrogenation reaction. A combination of experimental and theoretical studies shows that the isolated Pt atoms stabilized by small Ga2O3 clusters are the active sites for activating the inert C-H bonds in ethane. The synergy of atomically dispersed Pt and Ga2O3 clusters confined in the 10MR channels of ZSM-5 can serve as a bifunctional catalyst for the direct ethane-benzene coupling reaction for the production of ethylbenzene, surpassing the performances of the counterpart catalysts made with PtGa nanoclusters and nanoparticles.

Decoding Chemical Bonds: Assessment of the Basis Set Effect on Overlap Electron Density Descriptors and Topological Properties in Comparison to QTAIM.

Quantum chemical bonding descriptors based on the total and overlap density can provide valuable information about chemical interactions in different systems. However, these descriptors can be sensitive to the basis set used. To address this, different numerical treatments of electron density have been proposed to reduce the basis set dependency. In this work, we introduce overlap properties (OPs) obtained through numerical treatment of the electron density and present the topology of overlap density (TOP) for the first time. We compare the basis set dependency of numerical OP and TOP descriptors with their quantum theory of atoms in molecules (QTAIM) counterparts, considering the total electron density. Three single (C-C, C-O, and C-F) bonds in ethane, methanol, and fluoromethane and two double (C═C and C═O) bonds in ethene and formaldehyde were analyzed. Diatomic molecules Li-X with X = F, Cl, and Br were also analyzed. Eight parameters, including QTAIM descriptors and OP/TOP descriptors, are used to assess the basis dependency at the ωB97X-D level of theory using 28 basis sets from three classes: Pople, Ahlrichs, and Dunning. The study revealed that the topological overlap electron density properties exhibit comparatively lesser dependence on the basis set compared to their total electron density counterparts. Remarkably, these properties retain their chemical significance even with reduced basis set dependency. Similarly, numerical OP descriptors show less basis set dependency than their QTAIM counterparts. The excess of polarization functions increases charge concentration in the interatomic region and influences both QTAIM and OP descriptors. The basis sets Def2TZVP, 6-31++G(d,p), 6-311++G(d,p), cc-pVDZ, cc-pVTZ, and cc-pVQZ demonstrate reduced variability for the tested bond classes in this study, with particular emphasis on the triple-ζ quality Ahlrichs' basis set. We recommend against using basis sets with numerous polarization functions, such as augmented Dunning's and Ahlrichs' quadruple-ζ.

Bimetallic-Derived Catalytic Structures for CO2-Assisted Ethane Activation.

ConspectusIn recent years, the simultaneous upgrading of CO2 and ethane has emerged as a promising approach for generating valuable gaseous (CO, H2, and ethylene) and liquid (aromatics and C3 oxygenates) chemicals from the greenhouse gas CO2 and large-reserved shale gas. The key challenges for controlling product selectivity lie in the selective C-H and C-C bond cleavage of ethane with the assistance of CO2. Bimetallic-derived catalysts likely undergo alloying or oxygen-induced segregation under reaction conditions, thus providing diverse types of interfacial sites, e.g., metal/support (M/M'Ox) interface and metal oxide/metal (M'Ox/M) inverse interface, that are beneficial for selective CO2-assisted ethane upgrading. The alloying extent can be initially predicted by cohesive energy and atomic radius (or Wigner-Seitz radius), while the preference for segregation to form the on-top suboxide can be approximated using the work function, electronegativity, and binding strength of adsorbed oxygen. Furthermore, bimetallic-derived catalysts are typically supported on high surface area oxides. Modifying the reducibility and acidity/basicity of the oxide supports and introducing surface defects facilitate CO2 activation and oxygen supplies for ethane activation.Using in situ synchrotron characterization and density functional theory (DFT) calculations, we found that the electronic properties of oxygen species influence the selective cleavage of C-H/C-C bonds in ethane, with electron-deficient oxygen over the metal (or alloy) surface promoting nonselective bond scission to produce syngas and electron-enriched oxygen over the metal oxide/metal interface enhancing selective C-H scission to yield ethylene. We further demonstrate that the preferred structures of the catalyst surfaces, either alloy surfaces or metal oxide/metal inverse interfaces, can be controlled through the appropriate choice of metal combinations and their atomic ratios. Through a comprehensive comparison of experimental results and DFT calculations, the selectivity of C-C/C-H bond scission is correlated with the thermodynamically favorable bimetallic-derived structures (i.e., alloy surfaces or metal oxide/metal inverse interfaces) under reaction conditions over a wide range of bimetallic catalysts. These findings not only offer structural and mechanistic insights into bimetallic-derived catalysts but also provide design principles for selective catalysts for CO2-assisted activation of ethane and other light alkanes. This Account concludes by discussing challenges and opportunities in designing advanced bimetallic-derived catalysts, incorporating new reaction chemistries for other products, employing precise synthesis strategies for well-defined structures with optimized site densities, and leveraging time/spatial/energy-resolved in situ spectroscopy/scattering/microscopy techniques for comprehensive structural analysis. The research methodologies established here are helpful for the investigation of dynamic alloy and interfacial structures and should inspire more efforts toward the simultaneous upgrading of CO2 and shale gas.

Electrocatalytic Scission of Unactivated C(sp3)-C(sp3) Bonds through Real-Time Manipulation of Surface-Bound Intermediates.

Electrocatalysis plays a critical role in future technologies for energy storage and sustainable synthesis, but the scope of reactions achievable using electricity remains limited. Here, we demonstrate an electrocatalytic approach to cleave the C(sp3)-C(sp3) bond in ethane at room temperature over a nanoporous Pt catalyst. This reaction is enabled by time-dependent electrode potential sequences, combined with monolayer-sensitive in situ analysis, which allows us to gain independent control over ethane adsorption, oxidative C-C bond fragmentation, and reductive methane desorption. Importantly, our approach allows us to vary the electrode potential to promote the fragmentation of ethane after it is bound to the catalyst surface, resulting in unprecedented control over the selectivity of this alkane transformation reaction. Steering the transformation of intermediates after adsorption constitutes an underexplored lever of control in catalysis. As such, our findings widen the parameter space for catalytic reaction engineering and open the door to future sustainable synthesis and electrocatalytic energy storage technologies.

A greener route to ethylene

Chemical companies want to reduce greenhouse gas emissions wherever they can, and one of their first targets is their most notorious source of carbon dioxide: the steam cracker. Steam cracker furnaces burn massive amounts of natural gas and other hydrocarbons to achieve the temperatures of approximately 900 °C needed to break the carbon-hydrogen and carbon-carbon bonds in ethane, naphtha, and other feedstocks to make building-block chemicals like ethylene and propylene. Steam crackers emit around 1.2 metric tons (t) of CO 2 per 1 t of ethylene produced, according to a recent paper in Catalysts . Many large petrochemical companies are greening their ethylene production. Dow, for instance, is building a cracker in Alberta that will capture its CO 2 for sequestration underground. For the longer term, the company, along with Shell Chemicals, is testing electric furnaces that would run on renewable power. And many chemical companies are developing entirely new

Chemical looping conversion of ethane to ethanol via photo-assisted nitration of ethane

Ethane is an abundant and cheap hydrocarbon. Selective conversion of ethane to ethanol has economic value but is difficult to achieve due to overoxidation. Here, we report a chemical looping strategy established to selectively convert ethane (C 2 H 6 ) to ethanol (C 2 H 5 OH) using molecular oxygen (O 2 ) as the end oxidant and nitrogen dioxide (NO 2 ) as a relay oxidant. Visible light is used to excite NO 2 to drive a radical reaction with C 2 H 6 to produce ethyl nitrate (C 2 H 5 ONO 2 ) at −10°C with a selectivity of >80% and an ethane conversion of >90%. C 2 H 5 ONO 2 is hydrolyzed to generate C 2 H 5 OH and nitric acid (HNO 3 ), thus completing a chemical loop for the conversion of ethane to ethanol. DFT calculations show that the introduction of light overcomes the barrier of ethane activation at a relatively low temperature and thus avoids ethyl nitrate decomposition and overoxidation, leading to the high selectivity of ethyl nitrate. A chemical looping is proposed to convert ethane to ethanol Selective nitration of ethane produces ethylnitrate in high yields Atmospheric reaction is used for preparative synthesis Photocatalysis is used to activate inert C–H bond at mild conditions The activation of the inert C–H bonds in ethane, an abundant hydrocarbon gas, is an important step in alkane upgrading. He et al. put forward a chemical looping strategy to convert ethane to ethanol via selective photoactivated nitration under mild conditions.

C-H bond activation in light alkanes: a theoretical perspective.

Alkanes are the major constituents of natural gas and crude oil, the feedstocks for the chemical industry. The efficient and selective activation of C-H bonds can convert abundant and low-cost hydrocarbon feedstocks into value-added products. Due to the increasing global demand for light alkenes and their corresponding polymers as well as synthesis gas and hydrogen production, C-H bond activation of light alkanes has attracted widespread attention. A theoretical understanding of C-H bond activation in light hydrocarbons via density functional theory (DFT) and microkinetic modeling provides a feasible approach to gain insight into the process and guidelines for designing more efficient catalysts to promote light alkane transformation. This review describes the recent progress in computational catalysis that has addressed the C-H bond activation of light alkanes. We start with direct and oxidative C-H bond activation of methane, with emphasis placed on kinetic and mechanistic insights obtained from DFT assisted microkinetic analysis into steam and dry reforming, and the partial oxidation dependence on metal/oxide surfaces and nanoparticle size. Direct and oxidative activation of the C-H bond of ethane and propane on various metal and oxide surfaces are subsequently reviewed, including the elucidation of active sites, intriguing mechanisms, microkinetic modeling, and electronic features of the ethane and propane conversion processes with a focus on suppressing the side reaction and coke formation. The main target of this review is to give fundamental insight into C-H bond activation of light alkanes, which can provide useful guidance for the optimization of catalysts in future research.

Covalent and Ionic: Bonding Characteristics of HZnCH and ZnCH2and Their Interconversions

AbstractThe structures of zinc carbene ZnCH2and zinc carbyne HZnCH, and the conversion transition states between them are optimized at B3LYP/aug‐cc‐pVTZ, MP2/aug‐cc‐pVTZ, and CCSD/aug‐cc‐pVTZ levels of theory. The thermodynamic energies with CCSD(T) method are further extrapolated to basis set limit through a series of basis sets of aug‐cc‐pVXZ (X=D, T, Q, 5). The Zn−C bonding characteristics are interpreted by molecular plots, Laplacian of density plots, the integrated delocalization indices, net atomic charges, and derived atomic hardness. On the one hand, the studies demonstrated the efficiency of DFT method in structure optimizations and the accuracy of CBS method in obtaining thermodynamic energies; On the other hand, the density analysis of CCSD/aug‐cc‐pVDZ density demonstrates that both the sharing interaction and ionic interaction are important in ZnCH2ad HZnCH. The3B1state of ZnCH2is the global minimum and formed in visible light, but its small bond dissociation energy (47.0 kcal/mol) cannot keep the complex intact under UV light (79.4–102.1 kcal/mol). However, the3Σ−state of HZnCH can survive the UV light due to the greater Zn−C dissociation energy (100.7 kcal/mol). The delocalization indices of Zn…C in both3B1of ZnCH2(0.777) and the3Σ−state of HZnCH (0.785) are close to the delocalization index of the single C−C bond of ethane (0.841), i. e. the nomenclature of Zinc carbene and Zinc carbyne is incorrect. The stronger Zn−C bond in the3Σ−state of HZnCH than in the3B1state of ZnCH2can be attributed to the larger charge separation in the former. It was found that the Zn−C bonds in related Zinc organic compounds were also single bonds no matter whether the organic groups are CR, CR2, or CR3. The ionic interactions were discussed in terms of the atomic hardness that were in turn related to ionization energy and electron affinity. The unique combination of covalent and ionic characteristics in the Zn−C bonds of organic Zinc compounds could be the origin of many interesting applications of organic Zinc reagents.

Interfacial Active Sites for CO2 Assisted Selective Cleavage of C–C/C–H Bonds in Ethane

Summary Selective upgrading of underutilized ethane in shale gas with greenhouse gas CO2 can produce syngas via dry reforming (C–C bond scission) or ethylene via oxidative dehydrogenation (C–H bond scission). However, it remains challenging to identify active sites responsible for the selective bond cleavage in ethane due to the complexity of supported catalysts. Herein, the ethane-CO2 reaction over CeO2-supported catalysts was investigated to unravel the functions of distinct interfacial sites by combining kinetic measurements with in situ characterizations and calculations: the Pd/CeOx interface is responsible for supplying reactive oxygen species, electron-deficient oxygen species on Pd surface boosts the non-selective bond scission to produce syngas, electron-enriched oxygen in the FeOx/Pd interface enhances the selective scission of C–H bond to yield ethylene, and the FeOx/CeO2 interaction mediates oxygen supply and confines metal ensembles. The current work identifies opportunities for using different interfacial structures in upgrading abundant shale gas and CO2.

Theoretical study on the activation of C-H bond in ethane by PdX+ (X = F, Cl, Br, H, and CH3) in the gas phase.

The mechanism of C-H bond activation of ethane was catalyzed by palladium halide cations (PdX+ (X = F, Cl, Br, H, and CH3)), which was investigated using density functional theory (DFT) at B3LYP level. The reaction mechanism was taken into account in triplet and singlet spin state potential energy surfaces. For PdF+, PdCl+, and PdBr+, the high spin states were the ground states, whereas the ground states were the low spin states in PdH+ and PdCH3+. The reaction of PdF+, PdCl+, and PdBr+ with ethane occurred via a typical "two-state reactivity" mechanism. In contrast, for PdH+ and PdCH3+, the overall reaction performed on the ground state PESs in a spin-conserving manner. The crossing points between two potential energy surfaces were observed and effectively decreased the activation barrier in PdX+/C2H6 (X = F, Cl, and Br). The minimum energy crossing points (MECP) were obtained used the algorithm in Harvey method. The natural valence electron configuration calculations were analyzed by natural bond orbital. The distribution and contribution of the front molecular orbital of the initial complexes could be further understand by the density of states. The feature of the bonding evolution in the main pathways was studied using topological analysis including localized orbital locator and atoms in molecules.

Tools for Prescreening the Most Active Sites on Ir and Rh Clusters toward C-H Bond Cleavage of Ethane: NBO Charges and Wiberg Bond Indexes.

B3LYP calculations were carried out to study the insertion of iridium (Ir) and rhodium (Rh) clusters into a C–H bond of ethane, which is often the rate-limiting step of the catalytic cycle of oxidative dehydrogenation of ethane. Our previous research on Ir catalysis correlates the diffusivity of the lowest unoccupied molecular orbital of the Ir clusters and the relative activities of the various catalytic sites. The drawback of this research is that the molecular orbital visualization is qualitative rather than quantitative. Therefore, in this study on C–H bond activation by the Ir and Rh clusters, we conducted analyses of natural bond orbital (NBO) charges and Wiberg bond indexes (WBIs), both of which are not only quantitative but also independent of the basis sets. We found strong correlation between the NBO charges, the WBIs, and the relative activities of the various catalytic sites on the Ir and Rh clusters. Analyses of the NBO charges and the WBIs provide a fast and reliable means of prescreening the most active sites on the Ir and Rh clusters and potentially on other similar transition-metal clusters that activate the C–H bonds of ethane and other light alkanes.

Activation Pathway of C‐H and C–C Bonds of Ethane by Pd Atom with CO2 as a Soft Oxidant

AbstractEthane and CO2 can be converted to synthesis (CO and H2) via the dry reforming pathway and formed important industrial raw material ethylene through oxidative dehydrogenation pathway, which are relating to the C−C bond and C−H bond cleavage, respectively. In this study, density functional theory was used to study the activation reaction of ethane C−H bond, C−C bond on Pd atom with CO2 as oxidant. CH3CH3→CH2CH3+H→CH2CH2+2H is the dominant path for dehydrogenation to ethylene. Adding an appropriate amount of H2 can reduce the deep dehydrogenation of ethylene and increase the selectivity. Under the condition of 873 K with Pd atom as catalyst, it is more inclined to ethane/CO2 reforming reaction. The main route for generating CO is CH3CH2+H→CH3+CH3→CH2→CHOH→CHO→CO. H atoms are conducive to the activation of CO2, CO2+H→COOH→CO+OH is the dominant reaction pathway for CO2 activation. The first reaction in the whole system is the first C−H bond cleavage of ethane.

Selective C-H Functionalization of Methane and Ethane by a Molecular SbV Complex.

Owing to the strong nonpolar bonds involved, selective C-H functionalization of methane and ethane to esters remains a challenge for molecular homogeneous chemistry. We report that the computationally predicted main-group p-block SbV (TFA)5 complex selectively functionalizes the C-H bonds of methane and ethane to the corresponding mono and/or diol trifluoroacetate esters at 110-180 °C with yields for ethane of up to 60 % with over 90 % selectivity. Experimental and computational studies support a unique mechanism that involves SbV -mediated C-H activation followed by functionalization of a SbV -alkyl intermediate.

Selective C−H Functionalization of Methane and Ethane by a Molecular SbV Complex

AbstractOwing to the strong nonpolar bonds involved, selective C−H functionalization of methane and ethane to esters remains a challenge for molecular homogeneous chemistry. We report that the computationally predicted main‐group p‐block SbV(TFA)5 complex selectively functionalizes the C−H bonds of methane and ethane to the corresponding mono and/or diol trifluoroacetate esters at 110–180 °C with yields for ethane of up to 60 % with over 90 % selectivity. Experimental and computational studies support a unique mechanism that involves SbV‐mediated C−H activation followed by functionalization of a SbV‐alkyl intermediate.

Combining CO2 Reduction with Ethane Oxidative Dehydrogenation by Oxygen-Modification of Molybdenum Carbide

The surface properties that determine the selectivity of Mo2C catalysts in ethane oxidative dehydrogenation with CO2 as a soft oxidant were investigated using a combination of pulse experiments and in-situ spectroscopic methods. Oxygen modification was discovered to be crucial for inhibiting the cleavage of the C–C bond in ethane and enhancing the production of ethylene. The addition of the Fe promoter accelerated the formation of surface oxygen species and stabilized them from reduction by ethane, leading to a shorter induction period, higher ethylene yield, and improved stability.

Energy decomposition analysis of single bonds within Kohn–Sham density functional theory

An energy decomposition analysis (EDA) for single chemical bonds is presented within the framework of Kohn-Sham density functional theory based on spin projection equations that are exact within wave function theory. Chemical bond energies can then be understood in terms of stabilization caused by spin-coupling augmented by dispersion, polarization, and charge transfer in competition with destabilizing Pauli repulsions. The EDA reveals distinguishing features of chemical bonds ranging across nonpolar, polar, ionic, and charge-shift bonds. The effect of electron correlation is assessed by comparison with Hartree-Fock results. Substituent effects are illustrated by comparing the C-C bond in ethane against that in bis(diamantane), and dispersion stabilization in the latter is quantified. Finally, three metal-metal bonds in experimentally characterized compounds are examined: a [Formula: see text]-[Formula: see text] dimer, the [Formula: see text]-[Formula: see text] bond in dizincocene, and the Mn-Mn bond in dimanganese decacarbonyl.

Probing Dative and Dihydrogen Bonding in Ammonia Borane with Electronic Structure Computations and Raman under Nitrogen Spectroscopy.

Although ammonia borane is isoelectronic with ethane and they have similar structures, BH3NH3 exhibits rather atypical bonding compared to that in CH3CH3. The central bond in ammonia borane is actually a coordinate covalent or dative bond rather than the conventional covalent C-C bond in ethane where each atom donates one electron. In addition, strong intermolecular dihydrogen bonds can form between two or more ammonia borane molecules compared to the relatively weak dispersion forces between ethane molecules. As a result, ammonia borane's physical properties are very sensitive to the environment. For example, gas-phase and solid-state ammonia borane have very different BN bond lengths and BN stretching frequencies, which led to much debate in the literature. It has been demonstrated that the use of cluster models based on experimental crystal structures led to better agreement between theory and experiment. Here, we employ a variety of cluster models to track how the interaction energies, bond lengths, and vibrational normal modes evolve with the size and structural characteristics of the clusters. The M06-2X/6-311++G(2df,2pd) level of theory was selected for this analysis on the basis of favorable comparison with CCSD(T)/aug-cc-pVTZ data for the ammonia borane monomer and dimer. Fourteen unique fully optimized molecular cluster geometries, (BH3NH3)n≤12, and nine crystal models, (BH3NH3)n≤19, were used to elucidate how the local environment impacts ammonia borane's physical properties. Computational results for the BN stretching frequencies are also compared directly to the Raman spectrum of solid ammonia borane at 77 K using Raman under liquid nitrogen spectroscopy (RUNS). A strong linear correlation was found to exist between the BN bond length and stretching frequency, from an isolated monomer to the most distorted BH3NH3 unit in a cluster or crystal structure model. Excellent agreement was seen between the frequencies computed for the largest crystal model and the RUNS experimental spectra (typically within a few wavenumbers).

MoO3 Nanoclusters Decorated on TiO2 Nanorods for Oxidative dehydrogenation of ethane to ethylene

Preparation of metal oxide supported nanostructure appears to be interesting and challenging because of the well-defined morphology and highly accessible active sites responsible for catalysis. Here we present an easy approach to synthesize a novel hybrid material composed of highly dispersed MoO3 nanoclusters on TiO2 nanorods of diameter 80–150nm and length between 1–1.5μm. These hybrid nanostructure catalysts exhibited excellent oxidative dehydrogenation activity for the conversion of ethane to ethylene with an ethylene yield of 50.7% in the presence of O2. The result shows markedly high synergy between the surface Mo+6 and ultrathin TiO2 nanorods, which selectively activates the CH bond of ethane for the production of ethylene.

Optimizing Open Iron Sites in Metal-Organic Frameworks for Ethane Oxidation: A First-Principles Study.

Activation of the C-H bonds in ethane to form ethanol is a highly desirable, yet challenging, reaction. Metal-organic frameworks (MOFs) with open Fe sites are promising candidates for catalyzing this reaction. One advantage of MOFs is their modular construction from inorganic nodes and organic linkers, allowing for flexible design and detailed control of properties. In this work, we studied a series of single-metal atom Fe model systems with ligands that are commonly used as MOF linkers and tried to understand how one can design an optimal Fe catalyst. We found linear relationships between the binding enthalpy of oxygen to the Fe sites and common descriptors for catalytic reactions, such as the Fe 3d energy levels in different reaction intermediates. We further analyzed the three highest-barrier steps in the ethane oxidation cycle (including desorption of the product) with the Fe 3d energy levels. Volcano relationships are revealed with peaks toward higher Fe 3d energy and stronger electron-donating group functionalization of linkers. Furthermore, we found that the Fe 3d energy levels positively correlate with the electron-donating strength of functional groups on the linkers. Finally, we validated our hypotheses on larger models of MOF-74 iron sites. Compared with MOF-74, functionalizing the MOF-74 linkers with NH2 groups lowers the enthalpic barrier for the most endothermic step in the reaction cycle. Our findings provide insight for catalyst optimization and point out directions for future experimental efforts.