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  • 1
    Electronic Resource
    Electronic Resource
    An apparatus for adsorption dynamics studies using infrared measurement of the adsorbent temperature (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2130-2136 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An apparatus has been built for kinetics measurement in adsorption processes. It consists of a variable volume chamber where the adsorbent sample is placed. During the adsorption process the pressure and the sample temperature are measured. The temperature is measured by infrared detection achieving fast, sensitive, and nonintrusive measurements. Two methods are used for adsorption kinetics measurement: the volume step and the thermal frequency response. In the volume step method the volume is suddenly reduced and the adsorption process occurs at constant volume. Due to the sorption heat released during adsorption, the adsorbed mass is closely related to the sample temperature. This method permits one to determine the relevant thermodynamic parameters of the system and the kinetics up to 20 ms. The different mass transfer modes may then be separated. The thermal frequency response (TFR) method consists of achieving a periodic volume of the chamber. The amplitude and phase lag of the temperature, taking the pressure function as a reference, may be used to measure with great accuracy very fast kinetics (up to 1 ms). Moreover, it permits the easy discrimination of surface barrier from Fickian diffusion. Finally it allows one to measure microporous and macroporous mass transfer in the same experiment. It is shown that substantial improvements are obtained with the TFR method compared with the pressure frequency response method which was, until now, the best macroscopic method. Moreover, the TFR method has produced results in good accordance with the microscopic pulsed field gradient-nuclear magnetic resonance method. Volume step and TFR methods are limited to low pressure (less than ∼4 kPa) in consequence of nonisothermal gas compression. Experimental results are given to illustrate the possibilities of both methods. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148911
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  • 2
    Electronic Resource
    Electronic Resource
    A Temperature Frequency Response Method for Adsorption Kinetics Measurements (1999)
    Springer
    Adsorption 5 (1999), S. 135-143 
    Details
    ISSN: 1572-8757
    Keywords: diffusion ; kinetics measurements ; frequency response ; NaX zeolite ; silicalite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A Frequency Response Method based on the infrared measurement of the sample temperature has been developed for adsorption kinetics measurements. It consists in modulating the experimental chamber volume at constant frequency. The complex ratio of the temperature response over the pressure response is independent of time but is a function of the frequency depending on all the kinetics parameters of the system. This method is accurate and allows to measure very fast kinetics. Its major drawback is that a spurious signal is observed at high pressure in absence of adsorption. The results obtained with silicalite-propane and NaX-carbon dioxide are compared with results obtained from other techniques (NMR, permeation, etc.).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008965223931
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal frequency response method for the study of mass-transfer kinetics in adsorbents (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 700-712 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The frequency response method measuring the temperature and pressure of an adsorbent sample determines the mass- and heat-transfer kinetics in adsorbents, especially in zeolites. The temperature of the sample (large crystals or monolayers of pellets) is measured by infrared detection. The main aspects of the in-phase and out-of-phase functions as given by an analytical bidispersed model are described. They depend on characteristic times related to kinetic paprameters. Experimental results on adsorption of water on NaX zeolite (crystals or pellets) show that this method allows heat transfer to be very clearly delineated from mass-transfer modes and the separation of different mass-transfer modes. For a bidispersed sample, macro- and microporous mass-transfer parameters may be obtained with the same sample. Results on a contaminated 5A zeolite-propane system show the presence of mass-transfer resistance at the pellet surface. The infrared temperature measurement associated with the frequency response appears to be powerful in determining kinetic adsorption, and gives more information than the pressure measurement.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420311
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  • 4
    Electronic Resource
    Electronic Resource
    Single-step thermal method to measure intracrystalline mass diffusion in adsorbents (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2047-2057 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A single-step thermal method is used to measure intracrystalline mass diffusion. Sorption/desorption rates is zeolite samples (large crystals, monolayers of pellets, or even a single pellet) after a pressure of volume step are followed by monitoring the sample surface temperature by infrared detection. For a volume step, the pressure is also measured yielding the adsorbed mass. Sorption rates of water vapor in NaX are measured both on large 100 - μm crystals and pellets. This fast system correcsponds to the limit of the pressure-step termal method (using 100 -μm crystals). Sorption rates of methanol in the same large NaX crystals show good precision by the pressure-step method. The methanol results show that a surface barrier may occur after thermal regeneration of the sample in the presence of methanol traces. A major advantage of this method is that the shape of response curves can provide useful information on the nature of the masstransfer resistance despite its limits. Sorption rates of methanol vapor on mordenite H (zeolon) pellets prove that the intracrystalline diffusivity may be extracted from pellet measurements for a slow diffusing species.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410905
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