Modelling the transient kinetics of heterogeneous catalysts. CO-oxidation over supported Cr and Cu

Abstract

Modelling the transient kinetics of heterogeneous catalysts. CO oxidation over supported Cr and Cu Dekker, F.H.M.; Klopper, G.; Bliek, A.; Kapteijn, F.; Moulijn, J.A. Published in:Chemical Engineering Science Link to publicationCitation for published version (APA): Dekker, F. H. M., Klopper, G., Bliek, A., Kapteijn, F., & Moulijn, J. A. (1994). Modelling the transient kinetics of heterogeneous catalysts. CO oxidation over supported Cr and Cu. Chemical Engineering Science, 49(24), 4375-4390. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract--This article illustrates the capabilities of the step response method in the determination of the mechanism and kinetics of a heterogeneously catalyzed reaction. The step response method was applied to investigate the CO oxidation over alumina-supported chromium and copper. Detailed mechanisms of this reaction were determined by measuring the isothermal reduction and oxidation of the catalysts via switching the gas-phase composition from inert (He) to either reducing (CO) or oxidizing (02) conditions, Modelling the obtained response curves has given information on the reaction rate constants of the elementary steps in the CO oxidation over the Cr and Cu catalyst. Here, only a minimum number of reaction steps and parameters have been used, but they are still physically acceptable. The reduction of the Cr catalyst was found to proceed via reaction of adsorbed CO. The activation energy of this process is 95 kJ mol -~. The dispersion of the Cr catalyst is 20%, whereas only half the metal atoms at the catalyst surface participate in the oxidation and reduction. The latter metal atoms are coordinated to about four removable oxygen atoms Reduction of the Cu catalyst takes place in three steps: first oxygen on the surface is removed via reaction of CO from the gas phase. Next the oxygen in the surface is removed via reaction of adsorbed CO, and finally the oxygen from the bulk of the catalyst that has diffused to the surface is removed. The activation energy of all three processes has been determined. The dispersion of the Cu catalyst was found to be about 22%, MODELLING THE TRANSIENT KINETICS OF H E T E R O G E N E O U S CATALYSTS. CO-OXIDATION OVER I N T R O D U C T I O NIn heterogeneous catalysis much effort is put into est...

Transient kinetic model of CO oxidation over a nanostructured Cu0.1Ce0.9O2− catalyst

“…The number of studies regarding CO oxidation over oxide catalysts is substantially lower [15,16]. Even less is the number of studies that include elementary-step modeling of the diffusion of subsurface lattice oxygen in carbon monoxide oxidation over oxide catalysts.…”

Chemical looping syngas from CO2 and H2O over manganese oxide minerals

“…We apply the mass action law and express the rate law as a function of the product of the initial surface concentration of oxygen vacancies (or Mn sites). This approach is similar to that of Dekker et al Whereas Dekker et al considered a lumped concentration of removable oxygen, we separate the surface reaction and lattice diffusion phenomena as follows: …”

Demonstrating the Potential of Chemiluminescence as a Tool to Characterize Heterogeneous Catalysis Using CO Oxidation on Copper‐Based Catalysts as an Example

“…3) Mars van Krevelen (MK) mechanism: The adsorbed CO on CuO reacts with lattice oxygen in the support material. The LH mechanism was reported for CuO, [12] both ER and LH mechanisms were reported for CuO/Al 2 O 3 , [13,14] the LH mechanism was reported for CuO/SiO 2 , [15] and the MK mechanism was reported for CuO/TiO 2 . [15] As shown in Figure 2, CL was obtained from CuO/Al 2 O 3 but not from CuO, CuO/SiO 2 , or CuO/TiO 2 .…”

“…Therefore, the CO 2 concentration showed a trough, in other word, showed two peaks. The first peak was attributed to the ER mechanism and the second peak was attributed to the LH mechanism ,. In order to validate that CL was emitted via the ER mechanism, the peak of the CL emitting profile should correspond to the first peak of the CO 2 concentration profile.…”