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Journal ArticleDOI

Disproportionation of CO: I. Over iron and silicon-iron single crystals

01 Aug 1970-Journal of Catalysis (Academic Press)-Vol. 18, Iss: 2, pp 164-183
TL;DR: In this article, a detailed study of the catalytic disproportionation of CO over Fe and 3.5% Si-Fe single crystals in the range 550-800 °C has been made.
About: This article is published in Journal of Catalysis.The article was published on 1970-08-01. It has received 76 citations till now. The article focuses on the topics: Disproportionation & Reaction rate.
Citations
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Journal ArticleDOI
TL;DR: In this paper, single-walled carbon nanotubes (SWNTs) have been produced in a gas-phase catalytic process, where catalysts for SWNT growth form in situ by thermal decomposition of iron pentacarbonyl in a heated flow of carbon monoxide at pressures of 1-10 atm and temperatures of 800-1200°C.

1,812 citations

Journal ArticleDOI
TL;DR: In the presence of a nickel catalyst, acetylene decomposed to form carbonaceous solids with filamentary, amorphous, or laminar form as discussed by the authors, and parameters controlling the type of deposit have been established.

1,142 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the causes of deactivation of supported metal catalysts by carbon or coke formation, and found that deactivation can occur due to fouling of the metal surface, blockage of catalysts pores and voids, and actual physical disintegration of the catalyst support.
Abstract: Deactivation of supported metal catalysts by carbon or coke formation is a problem of serious magnitude in steam reforming, methanation, and other important catalytic processes. Its causes are generally threefold: (1) fouling of the metal surface, (2) blockage of catalysts pores and voids, and/or (3) actual physical disintegration of the catalyst support. Since loss of catalytic activity and physical destruction of the catalyst by carbon deposits can occur rapidly (within hours or days) under unfavorable conditions, understanding and control of these effects are of major technological and economical importance.

760 citations

Journal ArticleDOI
TL;DR: The HiPco process has been used to produce high-purity carbon single-walled nanotubes (SWNTs) using a gas-phase chemical-vapor-deposition process as mentioned in this paper.
Abstract: We have demonstrated large-scale production (10 g/day) of high-purity carbon single-walled nanotubes (SWNTs) using a gas-phase chemical-vapor-deposition process we call the HiPco process. SWNTs grow in high-pressure (30–50 atm), high-temperature (900–1100 °C) flowing CO on catalytic clusters of iron. The clusters are formed in situ: Fe is added to the gas flow in the form of Fe(CO)5. Upon heating, the Fe(CO)5 decomposes and the iron atoms condense into clusters. These clusters serve as catalytic particles upon which SWNT nucleate and grow (in the gas phase) via CO disproportionation: CO+CO⇒CO2+C(SWNT). SWNT material of up to 97 mol % purity has been produced at rates of up to 450 mg/h. The HiPco process has been studied and optimized with respect to a number of process parameters including temperature, pressure, and catalyst concentration. The behavior of the SWNT yield with respect to various parameters sheds light on the processes that currently limit SWNT production, and suggests ways that the producti...

704 citations

Book ChapterDOI
TL;DR: In this paper, the history of the development of methane conversion to synthesis gas is summarized as an introduction to the partial oxidation of methane, which is reviewed with emphasis on hot spots in reactors, major developments in the reduction of O 2 separation costs, and reaction mechanisms.
Abstract: The preparation of synthesis gas from natural gas, which is the most important step in the gas-to-liquid transformation, has attracted increasing attention in the last decade. Steam reforming, partial oxidation, and CO 2 reforming are the three major processes that can be employed to prepare synthesis gas. Because steam reforming was reviewed recently in this series [Adv. Catal. 47 (2002) 65], this chapter deals only with the latter two processes. The history of the development of methane conversion to synthesis gas is summarized as an introduction to the partial oxidation of methane, which is reviewed with emphasis on hot spots in reactors, major developments in the reduction of O 2 separation costs, and reaction mechanisms. The various catalysts employed in CO 2 reforming are examined, with emphasis on inhibition of carbon deposition.

296 citations

References
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Journal ArticleDOI
01 Apr 1953-Nature
TL;DR: In this article, it has been shown that carbon is formed by the interaction of carbon monoxide and iron oxide in the so-called iron spots in the brick, which can penetrate considerable thicknesses of brickwork, and a similar form of carbon growth is observed if iron ore, magnetite or any form of iron oxide is substituted for the brick samples.
Abstract: IN the course of experimental work on the deposition of carbon in the brickwork of blast furnaces (deposition which may cause the disintegration of the bricks), it has been found by electron micrography that the carbon is deposited as minute vermicular growths which can penetrate considerable thicknesses of brickwork. The carbon is formed by the interaction of carbon monoxide and iron oxide in the so-called iron-spots in the brick. It has been found possible to reproduce this reaction in the laboratory by exposing samples of brick containing iron spots to the action of carbon monoxide at an optimum temperature of about 450° C. Moreover, a similar form of carbon growth is observed if iron ore, magnetite or any form of iron oxide is substituted for the brick samples.

230 citations

Journal ArticleDOI
TL;DR: In this article, the e-carbide is hexagonal with lattice constants a = 4767A and c = 4354A, and its structure belongs to the space group P 6 3 22, iron atoms occupying 6 g positions with the parameter x = 1/3 and carbon atoms 2 d positions.
Abstract: Thin iron films formed by evaporation were carburized in CO gas stream The carbides e, χ and θ were found to be formed in the temperature ranges (i) below 250°C, (ii) from 250° to 350°C and (iii) above 350°C, respectively The e-carbide is hexagonal with lattice constants a = 4767A and c = 4354A, and its structure belongs to the space group P 6 3 22, iron atoms occupying 6 g positions with the parameter x = 1/3 and carbon atoms 2 d positions Irreversible phase transitions from e to χ and from χ to θ take place at 380°∼400°C and at about 550°C, respectively By the transitions changes in the chemical compositions may be very small Observation on the crystal growth suggests that a mechanism of the e-carbide formation is different from that of the χ- and θ- carbide formations

106 citations

Journal ArticleDOI
TL;DR: In this article, the phase transformation of γ-Fe 2 O 3 to α-Fe O 3 was studied by electron diffraction and the orientation relationship of the transformation is (111) γ //(0001) α and [1\bar10] γ //[01\bar 10] α.
Abstract: Phase transformation of γ-Fe 2 O 3 to α-Fe 2 O 3 was studied by electron diffraction. Above 400°C γ-Fe 2 O 3 is transformed to α-form which consists of twins. The orientation relationship of the transformation is (111) γ //(0001) α and [1\bar10] γ //[01\bar10] α . The twinning plane of transformation product was determined to be basal or (01\bar10) Plane. The transformation mechanism consists of the re-stacking of close-packed oxygen ion layers and the synchronous displacement of ferric ions located at the interstices of oxygen. These cooperative movements are discussed by dislocation models.

104 citations

Journal ArticleDOI
TL;DR: In this article, single crystal films of γ-Fe 2 O 3 were epitaxially grown on a (100) surface of MgO by the halidedecomposition method.
Abstract: Single crystal films of γ-Fe 2 O 3 were epitaxially grown on a (100) surface of MgO by the halide-decomposition method. Chemical analysis, electrical conductivity and, optical absorption measurements showed that the crystals contain no ferrous ions. X-ray diffraction assigned a cubic spinel structure and ruled out the presence of ordering of cation vacancies. Magnetization measurement and ferromagnetic resonance experiments were performed on these films which revealed the value of saturation magnetization and the anisotropy constants. The effective Bohr magneton number per iron atom was determined to be 1.45 at 0°K, which is considerably larger than that expected from Neel's theory. The Curie temperature is 743°K, which is lower than that found in ordinary γ-Fe 2 O 3 powder. These results conclude that the vacancies at 16 d sites are randomly distributed and nearly twenty percent of the total vacancies occupy 8 a sites.

101 citations