Download or read book The Partial Oxidation of Methane to Formaldehyde Over Molybdenum Oxide based Catalysts written by Marianne Rose Smith and published by . This book was released on 1992 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Partial Oxidation of Methanol to Formaldehyde Over Molybdenum tin Oxide Catalysts written by Rowaida George Zoumot and published by . This book was released on 1992 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vapor phase air oxidation of methanol to formaldehyde was investigated over molybdenum oxide, tin oxide and their mixtures in an integral flow reactor at atmospheric pressure between temperature of 513 and 573 K, a space time of 10-40 hr g-cat/g-mol methanol and a molar ratio of 0.04-0.1 mol CH3OH/mol air. Experiments were done under such conditions that the effects of internal and external heat and mass transfer effects were negligible. The effects of several process variables, temperature, space time and methanol/air ratio on the conversion of methanol and the selectivity of the catalyst for formaldehyde production were determined. The results indicated that the impact of the process variables on the conversion, selectivity and yield of formaldehyde were in the following decreasing order T > W/F > R. A screening study indicated the optimum catalyst composition to be 50% SnO2 and 50% MoO3, while conversion increased with temperature and W/F selectivity decreased. This catalyst proved to be highly active and selective to formaldehyde production. Selectivity and yield of up to about 100% were obtained at 100% conversion at a temperature of 553 K, a space time (W/F) of 40 g-cat/g-mol methanol per hour and a molar ratio (R) of 0.04 mol CH3 OH/mol air. The rate expression r=k1P2M 1+k1P2M2k 2PO2 was deduced assuming a steady-state involving two-stage irreversible oxidation-reduction process. It represented the experimental data satisfactorily. Arrhenius plots of the two rate constants gave activation energies of 31.7 and 18.1 kcal/g-mol.
Download or read book The Partial Oxidation of Methanol to Formaldehyde Over Molybdenum containing Catalysts written by Tsong-Jen Yang and published by . This book was released on 1982 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Partial Oxidation of Methanol to Formaldehyde Over Sb Mo Oxide Catalysts written by Rafael Alfredo Díaz Real and published by . This book was released on 1991 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The kinetics of the vapor phase air oxidation of methanol to formaldehyde over molybdenum oxide catalysts, antimony oxide catalyst, and their mixtures (both supported and unsupported), at atmospheric pressure and different operating conditions, have been studied in a fixed-bed integral reactor heated by a fluidized sand bath. The effect of various process variables, namely the process temperature (T), the ratio of catalysts to feed flow rate or space time (W/F), and the ratio of methanol fed to air (R), on conversion and yield have been determined. A screening study at varying operating conditions was performed to determine the optimum composition of a Sb$\sb2\rm O\sb4$-MoO$\sb3$ mixture. On the basis of this study a catalyst containing 67% $\rm Sb\sb2O\sb4$-33% MoO$\sb3$ was selected for the detailed kinetic study of oxidation of methanol to formaldehyde. The operating conditions studied were as follows: temperature in the range 623 to 698 K, space times from 5 to 50 $\rm g\sb{cat}/mol\sb{CH\sb3OH}h\sp{-1},$ and methanol to air ratios in the range 0.04 to 0.10 mol$\rm\sb{CH\sb3OH}h\sp{-1}/mol\sb{air}h\sp{-1}.$ This catalyst proved to be highly active and selective to formaldehyde formation. Yields up to $\sim$100% were obtained. Best operating conditions found were obtained at a space time of 27.5 for a methanol/air ratio of 0.06 and a temperature of 698 K. The rate equation for the oxidation of methanol to formaldehyde was derived on the basis of a two-stage redox mechanism$$\eqalign{\rm CH\sb3OH\sb{(g)} + S\sb{ox}\ {\buildrel{k\sb1}\over{\to}}\ &\rm HCHO\sb{(g)} + H\sb2O\sb{(g)} + S\sb{red}\cr\rm O\sb{2\sb{(g)}} + &\rm S\sb{red}\ {\buildrel{k\sb2}\over{\to}}\ S\sb{ox}\cr}$$where S$\rm\sb{ox}$ represents an active site of lattice oxygen and S$\rm\sb{red}$ represents a reduced site of lattice oxygen. The rate equation for the temperature of 648 to 698 K which correlated the data was$$\rm r = {k\sb1P\sb{M}\over 1+{k\sb1P\sb{M}\over 2k\sb2P\sb{O\sb2}}}$$where k$\sb1$ and k$\sb2$ are the temperature dependent rate constants of steps one and two. The equations relating k$\sb1$ and k$\sb2$ with temperature were$$\eqalign{&\rm ln\ k\sb1 = -6.4039-{6.9153\times10\sp3\over T}\cr&\rm ln\ k\sb2 = -3.0154 + {1.8809\times10\sp3\over T}\cr}$$ Several spectroscopic and analytical techniques, viz, electron spin resonance (ESR), x-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and adsorption studies were used to characterize the catalysts. The surface are of the catalyst used in the kinetic study was 6.1 m$\sp2$/g as determined by the BET method. A preliminary study of the Sb-Mo oxide mixture (load of $\sim$5 wt%) supported on Y zeolite was also carried out. Maximum yield obtained was comparable to that obtained with pure MoO$\sb3.$ A new catalyst has been developed that gave nearly 100% conversion and 100% yield. The industrial potential of this catalyst is very promising.
Download or read book Partial Oxidation of Methanol to Formaldehyde Over Mo Sn Oxide Catalysts written by Rowaida George Zoumot and published by . This book was released on 1992 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Catalytic Reaction Synthesis for the Partial Oxidation of Methane to Formaldehyde written by Maria-Guadalupe Cardenas-Galindo and published by . This book was released on 1993 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Formaldehyde Synthesis Via the Partial Oxidation of Methane Over Supported Metal Oxide Catalysts written by Aidan William Sexton and published by . This book was released on 1995 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of the Partial Oxidation of Methane to Formaldehyde Over Vanadium Oxide Catalysts Supported on Silica written by Benoit J. Kartheuser and published by . This book was released on 1993 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Oxidation of Methanol with Air Over Oxide Catalysts written by Wesley Rasmus Peterson and published by . This book was released on 1929 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Oxygen in Catalysis written by Adam Bielanski and published by CRC Press. This book was released on 1990-11-29 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: A description of catalytic systems commonly used as model systems in the laboratory and as industrial catalysts in large-scale operations, and a discussion of the mechanisms operating in these reactions. Attempts to describe the elementary steps by quantum chemical methods are also shown, as are rec
Download or read book Study of Partial Oxidation of Methanol Over Finely Divided Molybdenum Oxide written by Jong Shik Chung and published by . This book was released on 1984 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Methane Oxidation Over Dual Redox Catalysts Final Report 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 C2 hydrocarbons, was found to be directed by the catalyst used. In this project, it was discovered that a moderate oxidative coupling catalyst for C2 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 C2 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/La2O3 has been discovered for potentially commercially attractive process for the conversion of methane to C2 hydrocarbons, (ii) a new principle has been demonstrated for selectivity switching from C2 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 Selective Methane Oxidation Over Promoted Oxide Catalysts Quarterly Technical Progress Report September 8 1992 November 30 1992 written by and published by . This book was released on 1993 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Support effects on catalytic reactions, especially of highly exothermic oxidation reactions, can be very significant. Since we had shown that a MoO3/SiO2 catalyst, especially when used in a double bed configuration with a Sr/La2O3 catalyst, can selectively oxidize methane to formaldehyde, the role of the SiO2 support was investigated. Therefore, partial oxidation of methane by oxygen to form formaldehyde, carbon oxides, and C2 products (ethane and ethene) has been studied over silica catalyst supports (fumed Cabosil and Grace 636 silica gel) in the 630-780°C temperature range under ambient pressure. When relatively high gas hourly space velocities (GHSV) were utilized, the silica catalysts exhibit high space time yields (at low conversions) for methane partial oxidation to formaldehyde, and the C2 hydrocarbons were found to be parallel products with formaldehyde. In general, the selectivities toward CO were high while those toward CO2 were low. Based on the present results obtained by a double catalyst bed experiment, the observations of product composition dependence on the variation of GHSV (i.e. gas residence time), and differences in apparent activation energies of formation of C2H6, and CH2O, a reaction mechanism is proposed for the activation of methane over the silica surface. This mechanism can explain the observed product distribution patterns (specifically the parallel formation of formaldehyde and C2 hydrocarbons).
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 Catalysis and the Mechanism of Methane Conversion to Chemicals written by Toshihide Baba and published by Springer Nature. This book was released on 2020-04-18 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces various types of reactions to produce chemicals by the direct conversion of methane from the point of view of mechanistic and functional aspects. The chemicals produced from methane are aliphatic and aromatic hydrocarbons such as propylene and benzene, and methanol. These chemicals are created by using homogeneous catalysts, heterogeneous catalysts such as zeolites, and biocatalysts such as enzymes. Various examples of methane conversion reactions that are discussed have been chosen to illustrate how heterogeneous and homogenous catalysts and biocatalysts and/or their reaction environments control the formation of highly energetic species from methane contributing to C-C and C-O bond formation.
Download or read book FT IR Studies on Partial Oxidation of Methane Over Ferric Molybdate Catalysts written by Surajit Fuangfoo and published by . This book was released on 1997 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reactions of methane on Fe$\sb2$O$\sb3$, MoO$\sb3$ and ferric molybdate catalysts were studied in situ using the Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) technique. The ferric molybdate catalysts were prepared by coprecipitation of ferric nitrate and ammonium paramolybdate solutions. The experiments were carried out at the temperatures of 673, 703 and 743 K, and at the pressure of 1 and 3 MPa. This study revealed that MoO$\sb3$ is the active catalyst for the partial oxidation of methane to formaldehyde and Fe$\sb2$O$\sb3$ gives carbon dioxide. Both methanol and formaldehyde can be obtained from the ferric molybdate catalysts. The formation of methoxy (OCH$\sb3$), adsorbed formaldehyde, dioxymethylene (OCH$\sb2$O), and formate (OCHO) species were observed on the catalyst surface. A mechanism based on the reaction of methane with the surface of the ferric molybdate catalysts to produce methoxy groups which are further oxidized to dioxymethylene was proposed. The formation of carbon oxides is attributed to either the decomposition of dioxymethylene or to the formation of formate species. The kinetic parameters of the elementary reactions in the proposed mechanism were determined.
