Showing papers on "Thermal decomposition published in 1979"
TL;DR: The catalytic activity of MnO 2 prepared by different methods has been determined from the initial rate of decomposition of H 2 O 2 and the conversion of CO to CO 2.
180 citations
IBM1
TL;DR: In this paper, a methoxy species (CH3O) was identified as a quasi-stable surface intermediate during the thermal decomposition of chemisorbed methanol.
179 citations
TL;DR: In this article, hydrogenated amorphous silicon has been deposited by a new technique of thermal decomposition of silane from a hot tungsten or carbon foil heated to about 1600°C.
Abstract: Hydrogenated amorphous silicon has been deposited by a new technique of thermal decomposition of silane from a hot tungsten or carbon foil heated to about 1600 °C. Initial measurements indicate that the resulting films have a fairly high photoresponse. Introduction of ammonia along with silane is seen to enhance the photoconductivity quite significantly.
148 citations
TL;DR: In this article, the effect of TMO catalysts on solid propellant burning and decomposition, oxidizer burning, and sandwich and condensed mixture combustion is discussed. But, the exact mechanism of the effect on the burning rate modification of composite solid propellants is not clear even today.
Abstract: Introduction T metal oxides (TMO) like Fe2O3, CuO, MnO2, CuCr2O4, etc., form a very popular group of catalysts for burning rate modification of composite solid propellants. Although it is well known that these oxides affect the decomposition characteristics of polymers and oxidizers like ammonium perchlorate (AP)' and potassium perchlorate, (KP) the exact mechanism of the effect on solid propellants is by no means clear even today. Much fragmentary literature is available on the effect of these oxides on propellant burning and decomposition, oxidizer burning and decomposition, and sandwich and condensed mixture combustion. It is the purpose of this review to bring the material together so that a comprehensive picture can be drawn of the mechanism of the action of these catalysts. It may be mentioned here that these oxides also catalyze hydrocarbon oxidation reactions by inducing free radical decomposition of hydroperoxides (formed by the contact of oxidizer and hydrocarbon).
91 citations
TL;DR: Amorphous MoS3, prepared by chemical or thermal decomposition of ammonium thiomolybdate, has been found to react readily with n butyl lithium and sodium and potassium naphthalides to give compositions MxMoS3 (0 ≤ x ≤ 4, M = Li, Na, K) as mentioned in this paper.
79 citations
77 citations
TL;DR: The thermal decomposition of 1-(2-cyano-2′-propoxy)-4-oxo-2,2,6,6-tetramethylpiperidine in solution has been studied as a function of solvent, temperature, and the presence of radical scavengers as discussed by the authors.
Abstract: The thermal decomposition of 1-(2-cyano-2′-propoxy)-4-oxo-2,2,6,6-tetramethylpiperidine in solution has been studied as a function of solvent, temperature, and the presence of radical scavengers. I...
68 citations
TL;DR: In this paper, the influence of the preparation history of α-Fe2O3 on its reactivity has been investigated in the context of hydrogen reduction of the metal ion Cu2+, Ni2+, and Ti4+ in a stream of oxygen, air or nitrogen at temperatures of 500-1200°C for one hour.
66 citations
66 citations
TL;DR: Glassy carbon (Sigradur G(R)) can substitute for PTFE vessels in a pressure-bomb device for the wet decomposition of organic and inorganic substances with, e.g., nitric, chloric or hydrofluoric acid or mixtures thereof, in the determination of trace elements.
65 citations
TL;DR: The thermal decomposition of vanadium, chromium, manganese, iron, cobalt and nickel metallocenes in vacuum has been studied in this article, showing that the thermal stability of the electron-deficient π-complexes of metals to the left of the Periodic System changes in parallel with the thermodynamic functions of the metal-ring bond dissociation.
TL;DR: In this paper, the authors used laser microprobe analysis and dynamic mass spectrometric techniques to identify the primary volatile degradation products and initial pyrolysis reactions that control polymer degradation.
Abstract: Detailed results of the overall thermal degradation of poly(butylene terephthalate) are reported. Laser microprobe analysis and dynamic mass spectrometric techniques were used to identify the primary volatile degradation products and initial pyrolysis reactions that control polymer degradation. A complex multistage decomposition mechanism was observed which involves two major reaction pathways. Initial degradation occurs by an ionic decomposition process that results in the evolution of tetrahydrofuran. This is followed by concerted ester pyrolysis reactions that involve an intermediate cyclic transition state and yield 1,3-butadiene. Simultaneous decarboxylation reactions occur in both decomposition regimes. Finally, the latter stages of polymer decomposition were characterized by evolution of CO and complex aromatic species such as toluene, benzoic acid, and terephthalic acid. Activation energies of formation for the main pyrolysis products were determined from the dynamic measurements of the major ion species and indicate values of E = 27.9 kcal/mole for the production of tetrahydrofuran and E = 49.7 kcal/mole for the production of butadiene.
Patent•
11 Jun 1979TL;DR: The molybdenum disulfide of the invention also has desirable properties for use in catalyzed hydrogenation and hydrotreating reactions, i.e., hydrodenitrogenation and hydrodesulfurization reactions, particularly when employed in nickel or cobalt-promoted form as discussed by the authors.
Abstract: High surface area molybdenum disulfide, MoS 2 , is produced by the thermal decomposition of selected ammonium thiomolybdate salts at temperatures of about 300°-800° C., with said salts being heated to decomposition temperature at a rate in excess of about 15° C./min., e.g., about 20°-30° C./min., in an essentially oxygen-free atmosphere. The product molybdenum disulfide has superior catalytic properties for the water gas shift and methanation reactions compared with conventional MoS 2 . The stability of the catalyst is enhanced by decomposing the thiomolybdate salt in admixture with an inert, preformed particulate diluent or by bulk doping said salt with tungsten or vanadium prior to decomposition of the salt. The molybdenum disulfide of the invention also has desirable properties for use in catalyzed hydrogenation and hydrotreating reactions, i.e., hydrodenitrogenation and hydrodesulfurization reactions, particularly when employed in nickel or cobalt-promoted form.
TL;DR: In this article, the location of Fe in the octahedral sheet is characterized by two absorption bands, at 865-875 and 3607 cm - I, assigned as 6 AI-OH-Fe and v OH respectively.
Abstract: Fe substitution for AI in kaolinite (from Venezuelan laterites) is proved by infrared spectroscopy and chemical techniques. The location of Fe in the octahedral sheet is characterized by two absorption bands, at 865-875 and 3607 cm - I, assigned as 6 AI-OH-Fe and v OH respectively. The detection of the 865 cm - L band requires the use of CsC1 for the preparation of the disks heated to 270~ so that the clay delaminates as a result of a kaolinite-CsCl-H20 complex formation. The 3607 cm- l absorption is detected when KI disks are prepared. These two characteristic frequencies persist after either thermal decomposition or selective chemical dissolu tion of free iron and aluminium hydroxides. Selective chemical dissolutions by consecutive treatments for; (1) the removal of free iron oxides, (2) gibbsite removal and (3) extractions of Fe and AI from kaolinite, give additional evidence about the occurrence of this solid solution.
TL;DR: In this article, the formation of microporous alumina from various gibbsite samples has been studied under conditions of controlled residual pressure and decomposition rate, and the information obtained from thermal analysis, nitrogen adsorption, scanning calorimetry, and X-ray diffraction are consistent with a model in which the reaction interface advances parallel to the basal plane of the crystal, "drilling" micropores at the place of the "structural channels" of the gibbsite lattice and where the width of the micropore is controlled by the desorption stage.
TL;DR: When aqueous dispersions of Na+smectite or n-butylammonium-vermiculite react with sulfate salts of Fe(II), Co(II) or Ni(II)- bipyridyl or 1, 10-phenanthroline complexes in excess of the cation-exchange capacities, intersalated phases with spacings of about 29.5 A are obtained as mentioned in this paper.
Abstract: When aqueous dispersions of Na+-smectite or n-butylammonium-vermiculite react with sulfate salts of Fe(II), Co(II), or Ni(II) bipyridyl or 1, 10-phenanthroline complexes in excess of the cation-exchange capacities, intersalated phases with spacings of about 29.5 A are obtained. Thermal decomposition of the intersalated complex cations affords expanded phases with a d(001) spacing near 18 A for the smectites and near 28 A for the vermiculites. These phases are stable to temperatures of at least 550°C. Nitrogen surface areas of the fired products are as high as 400 m2/g.
TL;DR: Studies were undertaken to provide the basic physicochemical information necessary for preparing a suitable parenteral formulation of cefoxitin sodium, finding that the extent of loss in the crystalline solid at the end of the more rapid initial phase can be correlated with the water content of the solid.
TL;DR: In this paper, a model was proposed to explain the decomposition mechanism integratedly throughout the various partial pressures of carbon dioxide; the formation of the intermediate governed the decarbonation rate and the crystallization of MgCO 3 from the amorphous lower carbonate at ∼500°C.
TL;DR: The thermal decomposition of aryl diazonium salts of nonfluorinated acids in anhydrous media, generated by protonation of piperidyl triazenes, gives products resulting from reaction with added nucleophiles including high specific activity 18F-fluoride ions as mentioned in this paper.
Abstract: Thermal decomposition of aryl diazonium salts of nonfluorinated acids in anhydrous media, generated by protonation of piperidyl triazenes, gives products resulting from reaction with added nucleophiles including high specific activity 18F-fluoride ions.
Patent•
11 Jun 1979TL;DR: The molybdenum disulfide of the invention also has desirable properties for use in catalyzed hydrogenation and hydrotreating reactions, i.e., hydrodenitrogenation and hydrodesulfurization reactions, particularly when employed in nickel or cobalt-promoted form as mentioned in this paper.
Abstract: High surface area molybdenum disulfide, MoS 2 , is produced by the thermal decomposition of selected substituted ammonium thiomolybdate salts at temperatures of about 300°-800° C., with said salts being heated to decomposition temperature slowly, in an essentially oxygen-free atmosphere, through the temperature interval in which the substantial portion of the particular substituted ammonium thiomolybdate salts decompose. The product molybdenum disulfide has superior catalytic properties for the water gas shift and methanation reactions compared with conventional MoS 2 . The stability of the catalyst is enhanced by decomposing the thiomolybdate salt in admixture with an inert, preformed particulate diluent or by bulk doping said salt with tungsten or vanadium prior to decomposition of the salt. The molybdenum disulfide of the invention also has desirable properties for use in catalyzed hydrogenation and hydrotreating reactions, i.e., hydrodenitrogenation and hydrodesulfurization reactions, particularly when employed in nickel or cobalt-promoted form.
TL;DR: In this paper, the thermal decomposition of heptane in the presence of steam was studied in a flow reactor with large inner surface, and experiments were performed at atmospheric pressure in a temperature range of 680-760 OC for a mass ratio of steam to hydrocarbon 3:l.
Abstract: The thermal decomposition of heptane in the presence of steam was studied in a flow reactor with large inner surface. The experiments were performed at atmospheric pressure in a temperature range of 680-760 OC for a mass ratio of steam to hydrocarbon 3:l. The reaction products were analyzed by gas chromatography. For the identification both comparison of retention indices with those of standard compounds and literature data and mass spectrometry were used. The conversion process appeared to be a first-order reaction with a frequency factor of 1.34 X 10'' s-' and an activation energy of 195.5 kJ mol-'. The composition of the mixture of reaction products was in agreement with the Rice-Kossiakoff theory, except for ethane and 1-hexene.
TL;DR: In this article, the thermal decomposition of ferrous sulphate heptahydrate was carried out in air under dynamic and isothermal conditions, and the intermediate phases were identified by chemical analysis and an X-ray technique.
Abstract: The thermal decomposition of ferrous sulphate heptahydrate was carried out in air under dynamic and isothermal conditions. The intermediate phases were identified by chemical analysis and an X-ray technique. Ferrous sulphate heptahydrate is converted to tetrahydrate and monohydrate, but this conversion is accompanied by oxidation. Fe(OH)SO4 and Fe2O(SO4)2 are formed as oxidation products, and the latter decomposes to ferric oxide directly and/or through Fe2(SO4)3.
TL;DR: The products of thermal decomposition of RDX in vacuum have been determined mass spectrometrically below and above the melting point by employing a cell with an elongated office to form a collimated beam as mentioned in this paper.
01 Sep 1979-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, a laboratory study was carried out on the conversion of ammonium jarosite to iron oxide with recovery of reagents as byproducts, which resulted in the development of three process possibilities: 1) thermal decomposition with separate recovery of hematite, ammonia and sulfur dioxide, 2) decomposition of jarosite in an aqueous slurry to hematitic and ammonium sulfate, or 3) decomposition in an acid-based slurgharge to magnetite, ammonium and magnetite.
Abstract: Precipitation of iron as a jarosite is used in various hydrometallurgical processes. There are several advantages to this route, for example excellent liquid-solid separation characteristics, selective precipitation of iron in environmentally more stable form, recovery of sulfur as sulfuric acid and higher zinc extraction. However, jarosite precipitation also has disadvantages, the major being the high cost of reagents. A laboratory study was therefore carried out on the conversion of ammonium jarosite to iron oxide with recovery of reagents as byproducts. The investigation resulted in the development of three process possibilities: 1) thermal decomposition with separate recovery of hematite, ammonia and sulfur dioxide, 2) decomposition of jarosite in an aqueous slurry to hematite and ammonium sulfate, or 3) decomposition in an aqueous slurry to magnetite and ammonium sulfate. The conditions affecting the decomposition of jarosite by all three methods have been defined and the chemical, mineralogical and physical characteristics of the iron products are identified.
TL;DR: In this article, the pyrolysis of triethylgallium was studied in a toluene carrier gas system in the temperature range of 464.7 to 700.7 K and a pressure range of 0.82 to 3.73 K.
Abstract: The pyrolysis of triethylgallium has been studied in a toluene carrier gas system in the temperature range of 464.7 to 700.7 K and a pressure range of 0.82 to 3.73 kPa. From the data obtained from this work, the following mechanism for the thermal decomposition of the metal alkyl is proposed:where [1] is the rate determining step. After runs below 606 K were corrected for the contribution of a concurrent residual reaction, a least-squares analysis of experimental results from 567 to 651 K based on both product and residual alkyl analysis gaveat 1.60 kPa.The rate constant, k1, is very slightly pressure-dependent as revealed by tests at 648.0 K (80% and 45% decomposition). Studies indicate there is no detectable surface catalysis effect. Similarly, no effect was observed for changes in concentration or contact time.The mechanism for the formation of polymeric gallium hydride in reaction [4] is not clearly defined and may consist of more than one step. Reaction [5] is slow but based on the C2H4:H2 ratio must...
TL;DR: In this article, the first two stages of the thermal decomposition of calcium oxalate monohydrate have been established from non-isothermal thermogravimetric studies, and the rate-controlling processes are phase boundary reactions; the dehydration step assumes spherical symmetry whereas the decomposition step follows cylindrical symmetry.
TL;DR: In this paper, a 2,5-furandicarbonyl chloride with bisphenol A was studied in four systems, and the results showed that a white, film-forming polymer with an intrinsic viscosity of 0.5 was obtained.
TL;DR: The low temperature atmospheric pressure kinetics of silicon deposition by the thermal decomposition of silane were studied in this article, where the activation energy for this desorption is 30 kcal mol −1.