Transformation Of Methane Research Articles

Anaerobic conversion of methane to acetonitrile over solid-state-pyrolysis-synthesized GaN catalysts

The anaerobic conversion of methane to acetonitrile (AcCN) using GaN catalysts synthesized through the solid-state pyrolysis of gallium nitrate hydrate and melamine was investigated. A series of GaN catalysts (unsupported GaN, 50 wt% GaN/SiO2, and 5 wt% GaN/SiO2) were prepared, and their physicochemical properties were analyzed. The as-synthesized GaN catalysts had higher porosities, lower crystallinities, and better activities than those of the commercial GaN. Among tested catalysts, 5 wt% GaN/SiO2 displayed the highest methane conversion rate and AcCN productivity at 700 °C. Residual carbonaceous and nitrogen species, such as sp2-N (N = C) and cyano-N (NC), are likely to participate in the transformation of methane to AcCN. The activity of post-reaction 5 wt% GaN/SiO2 could be partially rejuvenated by a calcination-nitridation-activation process.

Methane Transformation over Copper-Exchanged Zeolites: From Partial Oxidation to C–C Coupling and Formation of Hydrocarbons

Methane Transformation over Copper-Exchanged Zeolites: From Partial Oxidation to C–C Coupling and Formation of Hydrocarbons

Methane oxidation to methanol over copper-containing zeolite

Methane oxidation to methanol over copper-containing zeolite

Microbial Involvement in Carbon Transformation via CH4 and CO2 in Saline Sedimentary Pool.

Simple SummaryMethane and carbon dioxide are commonly found in the environment and are considered the most important greenhouse gases. Transformation of these gases is in large carried by microorganisms, which occur even in extreme environments. This study presents methane-related biological processes in saline sediments of the Miocene Wieliczka Formation, Poland. Biological activity (carbon dioxide and methane production or methane oxidation), confirmed by stable isotope indices, occurred in all of the studied Wieliczka rocks. CH4-utilizing microbes constituted 0.7–3.6% while methanogens (represented by Methanobacterium) only 0.01–0.5% of taxa present in the Wieliczka Salt Mine rocks. Water activity was the key factor regulating microbial activity in saline subsurface sediments. Generally, CO2 respiration was higher in anaerobic conditions while methanogenic and methanotrophic activities were dependent on the type of rock.Methane and carbon dioxide are one of the most important greenhouse gases and significant components of the carbon cycle. Biogeochemical methane transformation may occur even in the extreme conditions of deep subsurface ecosystems. This study presents methane-related biological processes in saline sediments of the Miocene Wieliczka Formation, Poland. Rock samples (W2, W3, and W4) differed in lithology (clayey salt with veins of fibrous salt and lenses of gypsum and anhydrite; siltstone and sandstone; siltstone with veins of fibrous salt and lenses of anhydrite) and the accompanying salt type (spiza salts or green salt). Microbial communities present in the Miocene strata were studied using activity measurements and high throughput sequencing. Biological activity (i.e., carbon dioxide and methane production or methane oxidation) occurred in all of the studied clayey salt and siltstone samples but mainly under water-saturated conditions. Microcosm studies performed at elevated moisture created more convenient conditions for the activity of both methanogenic and methanotrophic microorganisms than the intact sediments. This points to the fact that water activity is an important factor regulating microbial activity in saline subsurface sediments. Generally, respiration was higher in anaerobic conditions and ranged from 36 ± 2 (W2200%t.w.c) to 48 ± 4 (W3200%t.w.c) nmol CO2 gdw−1 day−1. Methanogenic activity was the highest in siltstone and sandstone (W3, 0.025 ± 0.018 nmol CH4 gdw−1 day−1), while aerobic methanotrophic activity was the highest in siltstone with salt and anhydrite (W4, 220 ± 66 nmol CH4 gdw−1 day−1). The relative abundance of CH4-utilizing microorganisms (Methylomicrobium, Methylomonas, Methylocystis) constituted 0.7–3.6% of all taxa. Methanogens were represented by Methanobacterium (0.01–0.5%). The methane-related microbes were accompanied by a significant number of unclassified microorganisms (3–64%) and those of the Bacillus genus (4.5–91%). The stable isotope composition of the CO2 and CH4 trapped in the sediments suggests that methane oxidation could have influenced δ13CCH4, especially in W3 and W4.

SiC-foam structured Ni-based catalyst derived from perovskites for methane value-added application: Enhanced resistance to Ni sintering and stability

• A novel monolithic SiC-foam supported perovskite composites were synthesized. • SiC-foam shows excellent thermal conductivity that resists cold-spots formation. • Ni-SrO/SiC-foam displays remarkable resistance to ni sintering. • Ni-SrO/SiC-foam exhibits high ni dispersion due to the lattice confinement of SrNiO 3 perovskite. Sustainable transformation of methane into methanol feedstock syngas is a promising direction in future energy generation. A monolithic SiC-foam (SiC-foam, denoted as SCf) supported structured Ni-SrO composite nanomaterial was prepared via reducing the SrNiO 3 perovskite. The Ni-SrO/SCf displays a stronger resistance to Ni-sintering/coke-deposition than the unmodified Ni/SCf due to its uniform Ni distribution as well as the strong Ni-SrO interaction. In the presence of Ni-SrO/SCf sample at a gas hourly space velocity (GHSV) of 24,000 mL CH4 CO2 g Cat −1 h − 1 and an operating temperature of 850 °C, the initial conversion rate of biogas (CH 4 /CO 2 ) was 70/94%, which gradually dropped to 55/72% within 40 h, but its activity remained stable for the next 60 h. By contrast, the conversion rate of biogas (CH 4 /CO 2 ) in the presence of Ni/SCf sample was decreased rapidly from 60/80 to 50/65% within 20 h, due to the severe coke deposition and Ni-sintering.

Active Components of Catalysts of Methane Conversion to Synthesis Gas: Brief Perspectives

Methane transformation into more valuable products has attracted extensive attention. Synthesis gas is an important intermediate product in the chemical industry. Several syngas production methods are available, depending on the purpose of the industrial application. A major limitation of the processes is the rapid deactivation of the catalyst, which has been commonly attributed to the sintering of the active sites of catalyst and carbon formations on these sites, induced by methane decomposition and CO disproportionation. The catalyst consists of an active component and support. Ceria-based systems have been extensively employed as the support because of their unique redox properties and high oxygen storage capacity. The most promising approach is to design an excellent active site of the catalyst, based on noble or transition metals. A comparison of perspective active components, especially polymetallic components, is considered here.

Unraveling the Mechanism of Methane Activation on Zn‐Modified Zeolites by Solid‐State NMR

AbstractMethane activation on metal‐containing zeolites is a hot topic because of the great potential of the application of these catalysts for the direct transformation of methane to methanol and aromatics under mild conditions. Solid‐state nuclear magnetic resonance (SS NMR) spectroscopy is a powerful technique for characterizing small alkane activation and transformation on heterogeneous catalysts. It can provide insights into the different steps of alkane molecule activation that are difficult to assess with alternative methods. In this Concept article, the recent advances in the investigations of methane activation on Zn‐modified zeolites performed with SS NMR are discussed. These studies demonstrate the breadth of information that can be obtained by SS NMR spectroscopy, such as the intermediates formed, the particular Zn species involved, the possible pathways of the alkane activation. The knowledge acquired with SS NMR provides the basis for the realization of the detected conversions of methane in practice.

Direct Low-Temperature Oxidative Conversion of Methane to Acetic Acid on Rhodium-Modified Zeolites

Oxidative conversion of methane to acetic acid at 150°С and a pressure of 6.5 MPa with the assistance of carbon monoxide on rhodium-modified ZSM-5 zeolites with different SiO2/Al2O3 molar ratios was studied. A decrease in SiO2/Al2O3 from 300 to 30 leads to a 2.7-fold increase in the acetic acid yield. Such behavior of the catalytic system correlates with an increase in the acidity, primarily with an increase in the density of Bronsted acid sites on the zeolite surface. Introduction of 0.1–0.5 wt % rhodium into the zeolite increases the acetic acid yield by a factor of more than 3. The highest acetic acid yield (0.53 mmol/gcat) is attained on the zeolite with SiO2/Al2O3 = 33 modified with 0.5 wt % Rh. The methane transformation to acetic acid occurs while involving both the acid sites of the zeolite and the sites formed by reactive rhodium particles.

Atomistic simulations of the free-energy landscapes of interstellar chemical reactions: the case of methyl isocyanate

ABSTRACT Although complex organic molecules are observed in a wide variety of environments, chemical reaction networks heading to their formation are higly debated. It is a major endeavour to model the rates of reactions and incorporate them into chemical networks. The vast majority of the computational investigations in astrochemistry take into consideration oversimplified molecular models where chemical reactions are simulated under vacuum conditions (gas phase) and with crudely approximated entropic contributions to the free energy. We use density functional theory-based molecular dynamics techniques coupled with state-of-the-art metadynamics methods to investigate the role of ices embedding the reactants in shaping the free-energy landscape of selected reactions. Ices are chemically defined at the same level of theory of the reactants themselves. We consider as test case the transformation of methane and isocyanic acid into molecular hydrogen and methyl isocyanate, a species bearing similarities with peptide bonds. We examine the thermodynamically unfavoured case of very stable reactants to magnify modifications in the energy configuration induced by a solid amorphous water ice, either pure or mixed with CO. The presence of an active medium modifies significantly the free-energy surface, widening the path connecting reactants and products, and decreasing substantially the energy barriers. Ices not only act as gatherers of reactants, but also create thermodynamic conditions favouring chemical evolution.

Splitting Dioxygen over Distant Binuclear Fe Sites in Zeolites. Effect of the Local Arrangement and Framework Topology

Activation of dioxygen is of extreme importance due to its potential for transformation of methane to valuable products and applications in other selective oxidation reactions. Distant binuclear ca...

Splitting dioxygen over distant binuclear transition metal cationic sites in zeolites. Effect of the transition metal cation

AbstractSplitting dioxygen to yield highly active oxygen species attracts enormous attention due to its potential in direct oxidation reactions, mainly in transformation of methane into valuable products. Distant binuclear cationic Fe(II) centers in Fe‐ferrierite have recently been shown to be active in splitting dioxygen at room temperature to form very active oxygen species able to oxidize methane to methanol at room temperature as well. Computational models of the distant binuclear transition metal cationic sites (Co(II), Mn(II), and Fe(II)) stabilized in the ferrierite matrix were investigated by periodic density‐functional theory calculations including molecular dynamics simulations. The results reveal that the M(II) cations capable of the M(II) → M(IV) redox cycle with the M…M distance of ca 7.4 Å stabilized in two adjacent β sites of ferrierite can split dioxygen. Our study opens the possibility of developing tunable zeolite‐based systems for the activation of dioxygen employed for direct oxidations.

Reaction: Porous Organic Polymers for Uranium Capture

Cafer T. Yavuz received his PhD from Rice University in 2008 with a Welch scholarship under the supervision of Vicki Colvin. He then worked as a postdoctoral scholar at the University of California, Santa Barbara, with Galen Stucky. He started his independent group in 2010 at KAIST, Korea. He is currently a professor of chemistry at the King Abdullah University of Science and Technology in Saudi Arabia. His research focuses on the design and synthesis of nanoscale and porous materials for applications in energy and the environment. He uses fine chemistry in confined spaces to enable rapid and targeted transformations of CO2, methane, and water.

Effect of Copper State in Cu/H-ZSM-5 on Methane Activation by Brønsted Acid Sites, Studied by 1H MAS NMR In Situ Monitoring the H/D Hydrogen Exchange of the Alkane with Brønsted Acid Sites

With regard to possible involvement of zeolite Bronsted acid sites (BAS) in the activation of methane molecules for methane transformation to methanol, the effect of different Cu(II) species loaded...

Catalytic conversion of C1 molecules under mild conditions

C1 catalysis based on the transformation of methane, carbon monoxide, methanol and carbon dioxide offers great potential for the sustainable production of fuels and chemicals in response to the decrease of the energy consumption and plant maintenance. While the relatively inert nature of CH and CO bond (e.g., methane and carbon dioxide) and uncontrollable coupling of CC bond render the selective activation and controllable transformation of C1 molecules to high-value-added products challenging in C1 chemistry. Catalytic conversion of C1 energy molecules under mild conditions enables a better control of the selectivity of the desired products, however, which requires highly active catalysts to lower the reaction energy barriers. Besides designing efficient catalysts to promote C1 molecules conversion, employing electro-catalysis and photo-catalysis to circumvent the thermodynamic limitations is regarded as promising ways for C1 catalysis at low temperatures. Benefiting from the advanced technology for catalyst synthesis, reactor design, mechanism understanding, catalytic conversion of C1 molecules under mild conditions has made significant progress from 2010 to 2020. In this review, we summarized the typical catalytic processes and representative catalysts for transforming methane, carbon monoxide, methanol and carbon dioxide into high value-added chemicals with a reaction temperatures below 200 °C driven by thermo-catalysis, electro-catalysis, and photo-catalysis. Besides, a short perspective is offered to highlight possible future research directions towards C1 molecules conversion under mild conditions. It is expected to provide a useful reference for the readers to design better catalysts and reaction process for mild conversion of C1 molecules efficiently in future.

Visible-Light-Driven Methane Conversion with Oxygen Enabled by Atomically Precise Nickel Catalyst

It remains an extreme challenge to activate thermodynamically unfavorable, chemically inert methane molecules under mild conditions. Herein, we report a molecular-like nickel-thiolate hexameric clu...

Efficient plasma-catalysis coupling for CH4 and CO2 transformation in a fluidized bed reactor: Comparison with a fixed bed reactor

The transformation of methane and carbon dioxide by coupling plasma and catalysis was investigated using a fluidized bed reactor and the results, in terms of reactant conversion and yields in products, were compared with those obtained in a fixed bed reactor. A series of alumina, including a commercial sample and various meso-macro materials synthesized in the laboratory, was tested in this study. Their surface areas varied from 260 to 312 m2 g−1 depending on their calcination temperature. A correlation between reactant conversion and surface area of alumina was highlighted for the plasma-fluidized bed, the best conversions being reached with the alumina presenting the highest surface area. CH4 conversion increased from 8.5 to 12.1% for S = 260 and 312 m2 g−1 respectively and the CO2 conversion from 3.4 to 6.2% for a deposited power of 4 W, in an excess of CO2. This correlation was not corroborated for the fixed bed reactor. It proves that an efficient coupling of plasma and catalysis can be expected as soon as solid particle are moving in the gas flow, enhancing the plasma-surface interaction.

A Disruptive Innovation for Upgrading Methane to C3 Commodity Chemicals

C123 is a €6.4 million European Horizon 2020 (H2020) integrated project running from 2019 to 2023, bringing together 11 partners from seven different European countries. There are large reserves of stranded natural gas waiting for a viable solution and smaller scale biogas opportunities offering methane feedstocks rich in carbon dioxide, for which utilisation can become an innovation advantage. C123 will evaluate how to best valorise these unexploited methane resources by an efficient and selective transformation into easy-to-transport liquids such as propanol and propanal that can be transformed further into propylene and fed into the US$6 billion polypropylene market. In C123 the selective transformation of methane to C3 hydrocarbons will be realised via a combination of oxidative conversion of methane (OCoM) and hydroformylation, including thorough smart process design and integration under industrially relevant conditions. All C123 technologies exist at TRL3 (TRL = technology readiness level), and the objectives of C123 will result in the further development of this technology to TRL5 with a great focus on the efficient overall integration of not only the reaction steps but also the required purification and separation steps, incorporating the relevant state-of-the-art engineering expertise.

DFT исследование гомолитического разрыва C–H связей алканов и реакции дегидрирования пропиленгликоля на кластерах Fe4O7, NiFe3O7 и их протонированных и гидроксилированных формах

The results of a DFT study of elementary acts, both catalytic transformations of alkanes on hydride-hydroxyl forms of Fe4O7 and NiFe3O7 clusters, and processes of hydrocarbons transformation on iron and nickel-oxide clusters without initially hydride-hydroxyl filling are presented. Homolytic scission of the C–H bonds of alkanes on the hydride-hydroxyl form of the Fe4O7 cluster is accompanied by the formation of alkyl radicals capable of biradicals recombination according to the singlet type. There is also an additional reaction direction, which is represented by a singlet intra-associative rearrangement generating alcohols chemisorbed with the iron atom of the Fe4O6 cluster. This reaction is irreversible, proceeds with a large exothermic effect of 45.90 kcal∙mol-1, sufficient to overcome the chemisorption bond and diffuse into the volume of the supercritical fluid. The calculated characteristics of the interaction of alkanes with an iron-positioned hydroxyl group indicate that the activation energies of the forward direction of elementary acts in the homologous series: primary and secondary C–H bonds, lie in the range of 30.91-32.74 kcal∙mol-1, that is, these reactions are not very selective and strongly endothermic, since the activation energies of the reverse directions of the corresponding elementary acts are in the range of 1.40-3.27 kcal∙mol-1. The transition in the homologous series from the primary and secondary C–H bonds of propane to the tertiary C–H bonds of isobutane significantly changes the activation specificity of the homolytic scission of C–H bonds. The relative activation energy of the forward direction of the reaction decreases by about 8.00 kcal∙mol-1. A reaction system with the participation of the nickel-iron-oxide cluster NiFe3O7 and propane has been studied quantum-chemically. The result of the interaction of these reagents is the formation of isopropyl alcohol (propan-2-ol), which is chemisorbed with the nickel atom of the NiFe3O6 cluster. This reaction is irreversible and proceeds with a large exothermic effect of 50.95 kcal∙mol-1. The energetics of this process qualitatively coincides with the activation characteristics of the second stage of methane transformation on the Fe4O6 cluster; however, in this case, the reaction is a one-stage. It is noted that when carrying out various SCF extraction processes, for example, during the purification and regeneration of nickel and iron oxide catalysts, it should be borne in mind that the use of a propane-butane mixture as a supercritical fluid can be accompanied by its saturation with heavier hydrocarbons of linear and branched structure and alcohols. However, in real technological SCF processes, it is realistic to select the optimal temperature and flow regime that minimizes this effect. In the presence of a pre-reaction complex involving the hydrogen bond of the hydroxyl group of the initial propylene glycol and the interstitial oxygen atom (Fe–O–Fe) of the Fe4O7 cluster, a one-stage reaction with the oxidation product 1-hydroxypropan-2-ol becomes possible. The Fe4O6 iron oxide cluster with four coordinated iron centers having a hydroxyl group bound to each of them interacts with propylene glycol to form 1-hydroxypropan-2-ol, and the Fe–OH and Fe–O–Fe cluster substructures are the oxidative centers. In this case, the product of the reaction is a water molecule chemisorbed on the iron center and a hydrogen atom chemisorbed on the Fe–O–Fe substructure. This reaction is extremely exothermic (Q = 62.55 kcal∙mol-1) and has a very low activation energy for the forward direction of the reaction. By the example of the described heterogeneous hydrate-dissociative effects involving metal oxide surfaces and simple or functionalized alkanes, it can be seen that it is the protonated and hydroxylated forms of metal oxide surfaces that are responsible for elementary acts related to supercritical water oxidation.

Catalytic Oxidation of Methane to Oxygenated Products: Recent Advancements and Prospects for Electrocatalytic and Photocatalytic Conversion at Low Temperatures.

Methane is an important fossil fuel and widely available on the earth's crust. It is a greenhouse gas that has more severe warming effect than CO2. Unfortunately, the emission of methane into the atmosphere has long been ignored and considered as a trivial matter. Therefore, emphatic effort must be put into decreasing the concentration of methane in the atmosphere of the earth. At the same time, the conversion of less valuable methane into value‐added chemicals is of significant importance in the chemical and pharmaceutical industries. Although, the transformation of methane to valuable chemicals and fuels is considered the “holy grail,” the low intrinsic reactivity of its C—H bonds is still a major challenge. This review discusses the advancements in the electrocatalytic and photocatalytic oxidation of methane at low temperatures with products containing oxygen atom(s). Additionally, the future research direction is noted that may be adopted for methane oxidation via electrocatalysis and photocatalysis at low temperatures.

Aerobic oxidation of methane to formaldehyde mediated by crystal-O over gold modified tungsten trioxide via photocatalysis

General indirect transformation of methane into formaldehyde is based on methanol as intermediate yet leading to low selectivity. Herein, we report a direct photocatalytic conversion of methane to formaldehyde over gold modified cuboid-shaped tungsten trioxide with exposed (002), (020) and (200) facets containing crystal-O at room temperature (25 °C). Under light irradiation, high spin state crystal-O− ion as a hole can active CH bond in methane and subsequently be consumed to form formaldehyde, then renovated by the addition of oxygen. Isotopic 13CH4 and 18O2 tests reveal that formaldehyde indeed stems from the combination of methane and crystal-O on the exposed (002), (020) and (200) facets. Besides, metallic gold deposited on the surface of cuboid-shaped tungsten trioxide can extract the photoexcited electrons and further enhance the formation of crystal-O− ions. The productivity of formaldehyde over optimized catalyst can reach 7202 μmol g-1 with approximate 100 % selectivity within 24 h reaction time.