Download or read book Fundamentals Determining Activity and Product Selectivity in the Oxidative Coupling of Methane Over MnOx M2WO4 SiO2 M written by Anna Zanina and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present thesis contributes to a better understanding of one of the most promising catalysts for the oxidative coupling of methane (OCM) reaction, i.e., MnOx-Na2WO4/SiO2. Oxygen species involved in selective and unselective pathways were investigated using O2 and N2O as the oxidants. Spatially resolved and steady-state kinetic analyses combined with oxygen isotopic exchange tests were used to identify the activity-defining descriptor over M2WO4/SiO2 (M=Na, K, Rb, or Cs). The effects of alkali metal for both bi- and trimetallic compositions on activity and selectivity were establishedeng

Download or read book Methane Conversion by Oxidative Processes written by Wolf and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt: A reasonable case could be made that the scientific interest in catalytic oxidation was the basis for the recognition of the phenomenon of catalysis. Davy, in his attempt in 1817 to understand the science associated with the safety lamp he had invented a few years earlier, undertook a series of studies that led him to make the observation that a jet of gas, primarily methane, would cause a platinum wire to continue to glow even though the flame was extinguished and there was no visible flame. Dobereiner reported in 1823 the results of a similar investigation and observed that spongy platina would cause the ignition of a stream of hydrogen in air. Based on this observation Dobereiner invented the first lighter. His lighter employed hydrogen (generated from zinc and sulfuric acid) which passed over finely divided platinum and which ignited the gas. Thousands of these lighters were used over a number of years. Dobereiner refused to file a patent for his lighter, commenting that "I love science more than money." Davy thought the action of platinum was the result of heat while Dobereiner believed the ~ffect ~as a manifestation of electricity. Faraday became interested in the subject and published a paper on it in 1834; he concluded that the cause for this reaction was similar to other reactions.

Download or read book Methane Conversion by Oxidative Processes written by Eduardo E. Wolf and published by Springer. This book was released on 1992 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt: A reasonable case could be made that the scientific interest in catalytic oxidation was the basis for the recognition of the phenomenon of catalysis. Davy, in his attempt in 1817 to understand the science associated with the safety lamp he had invented a few years earlier, undertook a series of studies that led him to make the observation that a jet of gas, primarily methane, would cause a platinum wire to continue to glow even though the flame was extinguished and there was no visible flame. Dobereiner reported in 1823 the results of a similar investigation and observed that spongy platina would cause the ignition of a stream of hydrogen in air. Based on this observation Dobereiner invented the first lighter. His lighter employed hydrogen (generated from zinc and sulfuric acid) which passed over finely divided platinum and which ignited the gas. Thousands of these lighters were used over a number of years. Dobereiner refused to file a patent for his lighter, commenting that "I love science more than money." Davy thought the action of platinum was the result of heat while Dobereiner believed the ~ffect ~as a manifestation of electricity. Faraday became interested in the subject and published a paper on it in 1834; he concluded that the cause for this reaction was similar to other reactions.

Download or read book Catalytic Conversion of Carbon Monoxide and Methane Over Metal and Metal Oxide Catalysts written by Wenchi Liu and published by . This book was released on 2018 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysis is of vital importance in a wide range of areas including energy processing and chemical production. Catalytic conversion of C1 sources such as carbon monoxide and methane to make hydrocarbon fuels and oxygenated products has far reaching implications especially in the context of the gradual depletion of crude oil resource and the potential surge in the natural gas production in the coming decades. The control over reaction activity and selectivity for the conversion CO and CH4 in the Fischer–Tropsch synthesis and oxidative coupling of methane (OCM) have received tremendous attention and have been proved challenging. This dissertation focuses on the catalytic conversion of CO (Fischer–Tropsch synthesis) using supported cobalt based bimetallic nanoparticle model catalysts and the oxidative coupling of methane with noble metal promoted metal oxide catalysts. Using colloidal synthesis, a series of cobalt based bimetallic nanoparticles Co–M (M = Mn, Ru, Rh, and Re) with well-defined sizes, shapes, and compositions were obtained. Detailed synthesis procedures were presented and key synthetic parameters were discussed. The as-synthesized nanoparticles were subjected to extensive in-situ X-ray spectroscopy studies using ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and X-ray absorption spectroscopy (XAS) under catalytic relevant conditions. Composition wise, the results indicate the surface concentration of Co on the as-synthesized Co–M bimetallic particles is slightly less than the bulk atomic Co %. While oxidation treatment led to a slight increase of the surface Co, major effect was seen after the reduction treatment where surface segregation of the second metal resulted in a drastic decrease of the surface Co content. The effect is more pronounced at elevated reduction temperatures. Under reaction conditions, the surface compositions remained similar to those after the reduction treatment at high temperatures. Among the bimetallics tested, the Co–Mn system is relatively less susceptible to surface reconstructions induced by oxidation and reduction treatments. In addition, the reducibility of Co was also shown to be modified depending on the second metal present and Re was proved to be most efficient in leading to a facile reduction of Co. Catalytic performance of the bimetallic catalysts supported on mesoporous silica MCF–17 indicates a positive effect in the catalytic activity for Co–Rh and Co–Mn systems, while Co–Re and Co–Cu showed decreased activity. Less pronounced promotion effect of the second metal on the product distribution was observed with only a slight increase in the selectivity towards C5+ products. The selectivities for CH4 and C5+ of the various Co–M bimetallic catalysts generally resemble those of pure Co catalysts. Although in extremely low selectivity, alcohols were also formed with Co–Rh and Co–Cu bimetallic catalysts. The appearance of longer chain alcohol such as propanol, which was not present for pure Co catalysts, is an evidence for potential synergistic promotion. For oxidative coupling of methane (OCM), the promotion effect of noble metals (Pt, Ir, and Rh) on the performance of MnxOy-Na2WO4/MCF–17 catalysts was investigated. The introduction of noble metals had little effect on the surface area and phase composition of the original catalyst but led to a more reduced nature of the surface oxide species. Catalytic study revealed an enhanced selectivity towards both C2 and C3 hydrocarbons as compared to the undoped MnxOy-Na2WO4/MCF–17 catalyst in the order of Rh-doped > Ir-doped > Pt-doped samples together with a lower olefin to paraffin ratio. A more optimized strength of interaction between the carbon intermediates and the catalyst surface was suggested, which in combination with the improved reducibility of Mn and W species are believed to be responsible for the improved performance. In addition, monodispersed leaf-like manganese–tungsten–oxide (Mn–W–Ox) nanoparticles and hydroxylated hexagonal boron nitride (h-BN) were synthesized and used as novel catalysts in OCM reaction. Preliminary results indicate that the MCF–17 supported Mn–W–Ox nanoparticle catalyst showed a CH4 conversion of 5.4% and C2 selectivity of 42% with good stability over time. On the other hand, hydroxylated h-BN exhibited good activity (~20% CH4 conversion) with moderate selectivity towards C2 hydrocarbons (20%–30%). However, the hydroxylated h-BN catalysts faced serious deactivation, which was not eliminated by lowering the reaction temperature or the oxygen concentration in the reaction gas feed.

Download or read book Methane and Alkane Conversion Chemistry written by M.M. Bhasin and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: Natural gas, an abundant natural energy and chemical resource, is underutilized. Its inherent high energy content is compromised by its volatility. Storage and transportation problems abound for liquified natural gas. Several of the drawbacks of the utilization of natural gas, particularly its high volatility, could be offset by development of an economical and efficient process for coupling and/or further homologation of its principal component, methane. Alternatively, other conversion strategies such as partial oxidation to methanol and syngas, to oxygenates or conversion to such products via the intermediacy of chlorides should also be considered. Given the energy-intensive regimes necessary for the likely activation of methane, it was inevitable that researchers would tum to the use of heterogeneous catalysts. Heterogeneous catalysis is now a relatively mature discipline with numerous and diverse reactions being explored alongside informative studies on surface characterization, mechanism, and theory. Relationships to important related areas such as homogeneous catalysis, organometallic chemistry, and inorganic chemistry have become firmly established within this discipline. The field of methane and alkane activation is now over ten years old. The first decade of investigation produced results plagued by low yields and low-moderate conversions with well-articulated mechanistic limitations. As we begin the second decade of inquiry, novel strategies have brought increasing yields and conversions to such products as ethane, ethylene, methanol, and formaldehyde. These new approaches utilize separation of products via membranes or adsorbents. Moreover, additional mechanistic insight has been forthcoming from theoretical and computational examination as well as experimental investigation.

Download or read book Oxidative Coupling of Methane written by Vinzenz Fleischer and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanistic Studies on the Oxidative Coupling of Methane written by Chunlei Shi and published by . This book was released on 1993 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oxidative Coupling of Methane to C2 Hydrocarbon on Na2WO4 Mn SiO2 RHA Or Mullite Supports written by and published by . This book was released on 2007 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Da yu de han diao yu de written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oxidative Coupling of Methane Over La09 Sr01 O14 5 Catalyst written by Biren Dhirendra Ajmera and published by . This book was released on 1995 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Oxidative Coupling of Methane Over Alkali and Palladium Promoted Manganese Molybdate written by Donna K. Gardner and published by . This book was released on 1994 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oxidative Coupling of Methane Over Alkali promoted Manganese Molybdate Catalysts written by Sharon Anne Driscoll and published by . This book was released on 1993 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oxidative Coupling of Methane Over Chloride modified Magnesium Oxide Catalysts written by Paul Gary Hinson and published by . This book was released on 1996 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Influences of Support Material Variation on Structure and Catalytic Performance of MnxOy Na2WO4 SiO2 Catalyst for the Oxidative Coupling of Methane written by Mahmut Yildiz and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Selective Methane Oxidation Over Promoted Oxide Catalysts Quarterly Report March 1 May 31 1996 written by and published by . This book was released on 1996 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Series of catalysts consisting of MoO3, V2O5, TiO2, and SnO2 impregnated onto oxide supports consisting of SiO2 (Cab-O-Sil), TiO2 or SnO2 were previously prepared and tested for the selective oxidation of methane to oxygenates, and it was found that the V2O5/SiO2 catalyst was the most active and most selective toward the formation of formaldehyde. These catalysts have been characterized by laser Raman spectroscopy after dehydration and during the methane oxidation reaction with a CH4/02 = 10/1 reaction mixture at 500°C in a continuous flow in situ reaction cell. With the V2O5/SiO2 catalyst (the most active catalyst among those studied), no significant structural changes were revealed by in situ Raman analyses, indicating that the fully oxidized surface sites were related to the high formaldehyde selectivivity. Over the V2O5/TiO2 and V2O5/SnO2 catalysts, CO and CO2 were the principal products produced by oxidation of methane. For the first time, in situ Raman analysis clearly showed that for these latter catalysts, the surface vanadium(V) oxide species were partially reduced under the steady-state reaction conditions. The performance of the V2O5/TiO2/SiO2 catalyst was similar to that of the V2O5TiO2 catalyst, consistent with the earlier observation that vanadia was largely bound to the titania overlayer. It appears that formaldehyde selectivity decreased with increasing catalyst reducibility, but no direct correlation of catalyst activity with reductibility was observed.

Download or read book Methane Oxidation Over Dual Redox Catalysts written by and published by . This book was released on 1992 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic oxidation of methane to partial oxidation products, primarily formaldehyde and C[sub 2] hydrocarbons, was found to be directed by the catalyst used. In this project, it was discovered that a moderate oxidative coupling catalyst for C[sub 2] hydrocarbons, zinc oxide, is modified by addition of small amounts of Cu and Fe dopants to yield fair yields of formaldehyde. A similar effect was observed with Cu/Sn/ZnO catalysts, and the presence of a redox Lewis acid, Fe[sup III] or Sn[sup IV], was found to be essential for the selectivity switch from C[sub 2] coupling products to formaldehyde. The principle of double doping with an oxygen activator (Cu) and the redox Lewis acid (Fe, Sn) was pursued further by synthesizing and testing the CuFe-ZSM-5 zeolite catalyst. The Cu[sup II](ion exchanged) Fe[sup III](framework)-ZSM-5 also displayed activity for formaldehyde synthesis, with space time yields exceeding 100 g/h-kg catalyst. However, the selectivity was low and earlier claims in the literature of selective oxidation of methane to methanol over CuFe-ZSM-5 were not reproduced. A new active and selective catalytic system (M=Sb, Bi, Sn)/SrO/La[sub 2]O[sub 3] has been discovered for potentially commercially attractive process for the conversion of methane to C[sub 2] hydrocarbons, (ii) a new principle has been demonstrated for selectivity switching from C[sub 2] hydrocarbon products to formaldehyde in methane oxidations over Cu, Fe-doped zinc oxide and ZSM-5, and (iii) a new approach has been initiated for using ultrafine metal dispersions for low temperature activation of methane for selective conversions. Item (iii) continues being supported by AMOCO while further developments related to items (i) and (ii) are the objective of our continued effort under the METC-AMOCO proposed joint program.

Download or read book Oxidative Coupling of Methane Over Sm2O3 Catalysts written by Satish Nararyan Kamat and published by . This book was released on 1989 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: