Kinetics of γ-alumina chlorination by carbon tetrachloride

Bertóti, I.; Pap, I.S.; Szèkely, T.; Tóth, A.

doi:10.1016/0040-6031(80)80092-x

Cited by 28 publications

(10 citation statements)

References 4 publications

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“…The results obtained in this study are summarized in Figure 1, which also shows, under noncritical conditions, the results of previous investigators (Bertoti et al, 1980(Bertoti et al, , 1982. The primary difference between the present results and those of previous investigators is that the present experiments were conducted at much higher pressures (densities) and lower temperatures.…”

Section: Resultssupporting

confidence: 52%

“…From the lack of particle size effect and from the high activation energy, it is clear that both the high-temperature/low-pressure and high-pressure (density)/low-temperature results are chemically controlled. Bertoti et al (1980) reported that the process was chemically controlled up to 547OC, so the higher rates obtained in the present study are most likely due to a change in a chemically controlled rate-limiting step.…”

Section: Resultsmentioning

confidence: 58%

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Acceleration of chlorination of alumina using supercritical CCl₄

et al. 1988

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In the Alcoa smelting process, anhydrous aluminum chloride is electrolytically converted to aluminum metal. This process could have a major impact on the aluminum industry if an efficient way of making the anhydrous aluminum chloride from alumina were found (Othmer et al., 1978). To make aluminum chloride, carbon and chlorine must be added to alumina. The carbon and chlorine reactants can take many forms, but carbon tetrachloride is convenient in that the carbon and chlorine are together in a single molecule. The net reaction is written as:The kinetics of this reaction have received considerable attention but the rates of the reaction have been too slow to justify industrial development.In this study, means of increasing the reaction rate by operating at supercritical conditions are experimentally investigated. The reaction product, AlCl,, is soluble in the supercritical reactant, and the solubility enhancement that supercritical fluids display is a reasonable explanation for the increases in the observed rate, which are reported. Experimental ProcedureAlumina, 5-10 g, solid, and excess carbon tetrachloride, 30-60 g, liquid, were combined in a batch reactor and heated rapidly to reaction conditions. Pressures of 4 to 10 MPa and temperatures of 563 to 643 K were supercritical with respect to carbon tetrachloride (T, = 283"C, P, = 4.5 MPa) and were monitored continuously. Conversions were determined by extracting the reaction products with water and measuring the amount of unconverted alumina. Alumina is the only water-insoluble solid in the reactor. At the conditions studied, particle size (mass average dia. 60 pm, number average dia. 6 pm N, BET surface area 60 m'/g) and the total mass of alumina charged had no effect on the reaction rate per unit mass and hence fluid-solid mass transfer is considered to be unimportant in the overall reaction rate process. Runs with smaller particles produced no increase in the reaction rate, which indicates that internal mass transfer limitations are not important.Reaction rates were measured by dividing the amount of alumina converted by the isothermal reaction time. A correction was made for the conversion during the heat-up period using the measured activation energy. This correction was verified experimentally by stopping several runs as soon as run temperature was reached. These runs yielded 1 to 5% conversion during heatup. Conversions ranged from 6 to 48% except for one high-temperature run where the conversion reached 73%. In addition, the assumption of irreversibility of the reaction for these conversions was verified by two runs showing very high conversion (88%) as run time was lengthened to 4 h. Results and DiscussionThe results obtained in this study are summarized in Figure 1, which also shows, under noncritical conditions, the results of previous investigators (Bertoti et al., 1980(Bertoti et al., , 1982. The primary difference between the present results and those of previous investigators is that the present experiments were conducted at much higher pressures (d...

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 58%

Acceleration of chlorination of alumina using supercritical CCl₄

et al. 1988

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“…The radicals • CCl 3 and • Cl can recombine to form Cl 2 and C 2 Cl 6 , and by dissociation of C 2 Cl 6 it is possible to form C 2 Cl 4 [8].…”

mentioning

confidence: 99%

Kinetics of the gas-phase chlorination of activated carbon with carbon tetrachloride

et al. 2011

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The chlorination of activated charcoals KAU and SCN with CCl 4 vapor in the temperature range 300-600°C and also the thermal stability of the added chlorine has been studied. It is shown that chlorination with CCl 4 vapor led to the addition of up to 22 mass % (6.2 mmol/g) of chlorine to the surface layer of the carbon. The added chlorine is desorbed from the surface with formation of HCl, while at temperatures above 500°C desorption of chlorine goes practically to completion. The effective rate constants and the energies of activation of the processes of chlorination and desorption have been found.Investigation of the halogenation of carbon materials (CM) has prospects in connection with several problems. In the first place halogenation and subsequent nucleophilic substitution of halogen is a classical organic method, characterized by high yields for the introduction into the molecule of various groups containing N, S, O and other heteroatoms [1][2][3]. Secondly, the study of the results of halogenation under various conditions (amount of halogen added, evolution of hydrogen halides, etc.) as a result of a sufficiently selective process permits the establishment of the concentration of active centers in the surface, and thus obtains valuable information about the structure and characteristics of the surface layers of various CM. Most important is the determination of the temperature range in which the maximum amount of halogen is added to the surface of the CM.Halogenation of CM, and chlorination in particular, has attracted sufficient study [4][5][6]. However the kinetics of chlorination, the influence of temperature, reaction time, and the nature of the chlorinating agent on the concentration and properties of the surface chlorine have been insufficiently studied.In the present work the kinetics of the chlorination of activated carbon (AC) in CCl 4 vapor over a wide temperature range and the thermochemical properties of the chemisorbed chlorine have been studied. This method was chosen because in practice it does not lead to the parallel oxidation of the surface of the activated carbon.For this study two activated carbons were used -KAU (natural) and SCN (synthetic) with specific surfaces of 1300 and 1100 m 2 /g and pore volumes of 0.45 and 0.41cm 3 /g respectively. Chlorination was carried out both non-isothermally and isothermally with gravimetric control of the path of the reaction with rate of flow of the argon carrier gas of 50 mL/min. The concentration of CCl 4 in thee flow was 17.4 torr (2.03·10 -3 mol/L) and the argon was saturated with CCl 4 vapor at 20°C. The weight of aliquots of AC was 50 mg. 2640040-5760/11/4704-0264

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“…Sustancias como fosgeno (CI2CO) [3,4], cloruro de etileno (C2CI4 ) [5], tetracloruro de carbono (CCI4 ) [4,[6][7][8] y mezclas CI2-CO [9][10][11][12][13] son efectivas en la formación del cloruro metálico. No obstante ninguno de estos reactivos es utilizado en los procesos industriales.…”

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Estudio de la reacción de cloración de la circonia en presencia de carbono: desarrollo de un sistema termogravimétrico especialmente adecuado para el estudio cinético de reacciones de cloración de óxidos

Pasquevich¹

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El objetivo de este Trabajo de Tesis fuá desarrollar un Sistema Termogravimétrico, adecuado para el estudio de reacciones de cloración, y aplicarlo al estudio de la cinética de la reacción de CI2 con C y ZrO2; reacción que conduce a la formación de ZrCI4; producto de interés en la industria nuclear. El diseño, construcción y calibración del Sistema Termogravimétrico, construido sobre la base de una electrobalanza Cahn 2000, fue una parte muy importante de la Tesis. En la construcción del Sistema Termogravimétrico se realizó: el diseño; el montaje propiamente dicho; la calibración, con vistas a aplicarlo al estudio cinético de la reacción a estudiar y el acoplamiento con un sistema de adquisición de datos. En este aspecto, las calibraciones y su aplicación a estudios de cinética química significaron una contribución original a las técnicas termogravimétricas. La cloración de óxidos metálicos en presencia de carbono se conoce con el nombre de reacciones de carbocloración y se aplica fundamentalemnte a la obtención industrial de los cloruros de titanio y circonio. Una característica del sistema de reacción propuesto para este estudio, es la escasa información bibliográfica sobre el mismo, o sobre sistemas similares. Esta escasa información previa hizo necesario la realización del estudio de los sistemas de interacción parciales : CI2-C y CI2-ZrO2. La interacción CI2-C se estudió por termogravimetría. Se realizó también mediciones complementarias por espectrometría de masa de haz modulado. Por otra parte, el sistema Cl2-ZrO2 fue estudiado, fundamentalmente, por difracción de rayos X y por microscopía electrónica de transmisión. Una vez realizados los estudios mencionados se estuvo en condiciones de iniciar el estudio de la reacción de carbocloración, que involucra a ambas interacciones parciales, además de la reacción quimica misma. Los resultados obtenidos en estos estudios permitieron proponer un mecanismo para la metaestabilidad de la fase tetragonal de la circonia y un mecanismo para la interacción CI2-C; pusieron en evidencia que la carbocloración de circonia ocurre por dos mecanismos de reacción diferentes y permitieron proponer un mecanismo de reacción para cada una de las etapas de reacción.

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Kinetics of γ-alumina chlorination by carbon tetrachloride

Cited by 28 publications

References 4 publications

Acceleration of chlorination of alumina using supercritical CCl₄

Acceleration of chlorination of alumina using supercritical CCl₄

Kinetics of the gas-phase chlorination of activated carbon with carbon tetrachloride

Estudio de la reacción de cloración de la circonia en presencia de carbono: desarrollo de un sistema termogravimétrico especialmente adecuado para el estudio cinético de reacciones de cloración de óxidos

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Kinetics of γ-alumina chlorination by carbon tetrachloride

Cited by 28 publications

References 4 publications

Acceleration of chlorination of alumina using supercritical CCl4

Acceleration of chlorination of alumina using supercritical CCl4

Kinetics of the gas-phase chlorination of activated carbon with carbon tetrachloride

Estudio de la reacción de cloración de la circonia en presencia de carbono: desarrollo de un sistema termogravimétrico especialmente adecuado para el estudio cinético de reacciones de cloración de óxidos

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Acceleration of chlorination of alumina using supercritical CCl₄

Acceleration of chlorination of alumina using supercritical CCl₄