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Kinetic analysis of temperature-programmed reactions

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Kanervo, Jaana
dc.date.accessioned 2012-02-10T09:00:21Z
dc.date.available 2012-02-10T09:00:21Z
dc.date.issued 2003-10-16
dc.identifier.isbn 951-22-6747-0
dc.identifier.issn 1235-6840
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/2120
dc.description.abstract Temperature-programmed desorption (TPD), reduction (TPR) and oxidation (TPO) are thermoanalytical techniques for characterising chemical interactions between gaseous reactants and solid substances. The data collected by these techniques are commonly interpreted on a qualitative basis or by utilising simple, approximate kinetic methods. However, temperature-programmed techniques can also be regarded as transient response techniques and the experimental data can be utilised for dynamic modelling. This work comprises case studies on kinetic analysis of TPR, TPD and TPO related to the characterisation of heterogeneous catalysts. The emphasis is on methodological aspects and on assessing the potential of temperature-programmed data as a source of kinetic information. Kinetic analysis was applied to the TPR results for series of alumina-supported chromium oxide and vanadium oxide catalysts. Hydrogen was used as the reducing agent. Different kinetic models were tested against the experimental data and parameters were estimated. The chromium oxide and vanadium oxide contents of the catalysts were clearly reflected in the reduction behaviour and in the best-fit kinetic models and their parameters. The kinetic results suggested that reduction takes place via a topochemical mechanism, as growing domains, on both supported chromium and supported vanadium oxide catalysts with close to monolayer content. The interaction of hydrogen with a commercial nickel catalyst was studied in TPD experiments under continuous flow and ambient pressure. A model to account for the heterogeneity in the chemisorption interaction and for the readsorption was formulated and tested against experimental data. The heterogeneity was described by introducing a sufficient number of different adsorption states. The rapid readsorption occurring during TPD was taken into account by describing the intrinsic dynamics of an adsorption state as a quasi-equilibrium adsorption/desorption between the gas phase and the surface. A model with two adsorption states of hydrogen was able to describe the experimental data with physically acceptable parameters in the temperature range of 323-673 K. The regeneration kinetics of a deactivated cracking catalyst was investigated on the basis of the experimental evolution rates of carbon monoxide and carbon dioxide during TPO. Different kinetic models were tested and kinetic parameters were estimated. A power-law kinetic expression with orders unity and 0.6 for coke and oxygen, respectively, was capable of describing the experimental data. In each case study, a phenomenological model was established and the kinetic parameters of the model were determined via nonlinear regression analysis in MATLAB® environment. The results demonstrate that common catalyst characterisation data on reduction, desorption and oxidation collected in the temperature-programmed mode can fruitfully be subjected to detailed kinetic analysis. Mechanism and parameter identifiability require diversity in the experimental data, which can be achieved, for example, by applying multiple heating rates in experiments. Kinetic analysis extends the interpretability of temperature-programmed reactions in catalyst characterisation and it is potentially useful for the elucidation of fundamental reaction mechanistic information and establishing kinetic models for engineering applications. en
dc.format.extent 76, [49]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.ispartofseries Industrial chemistry publication series / Helsinki University of Technology en
dc.relation.ispartofseries 16 en
dc.relation.haspart Kanervo J. M. and Krause A. O. I., 2001. Kinetic analysis of temperature-programmed reduction: behavior of a CrO<sub>x</sub>/Al<sub>2</sub>O<sub>3</sub> catalyst. The Journal of Physical Chemistry B 105, pages 9778-9784.
dc.relation.haspart Kanervo J. M. and Krause A. O. I., 2002. Characterisation of supported chromium oxide catalysts by kinetic analysis of H<sub>2</sub>-TPR data. Journal of Catalysis 207, pages 57-65.
dc.relation.haspart Kanervo J. M., Harlin M. E., Krause A. O. I. and Bañares M. A., 2003. Characterisation of alumina-supported vanadium oxide catalysts by kinetic analysis of H<sub>2</sub>-TPR data. Catalysis Today 78, pages 171-180.
dc.relation.haspart Kanervo J. M., Reinikainen K. M. and Krause A. O. I., Kinetic analysis of temperature-programmed desorption. Applied Catalysis A: General, in press.
dc.relation.haspart Kanervo J. M., Krause A. O. I., Aittamaa J. R., Hagelberg P., Lipiäinen K. J. T., Eilos I. H., Hiltunen J. S. and Niemi V. M., 2001. Kinetics of the regeneration of a cracking catalyst derived from TPO measurements. Chemical Engineering Science 56, pages 1221-1227.
dc.subject.other Chemistry en
dc.title Kinetic analysis of temperature-programmed reactions en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Chemical Technology en
dc.contributor.department Kemian tekniikan osasto fi
dc.subject.keyword kinetic analysis en
dc.subject.keyword temperature-programmed reactions en
dc.subject.keyword kinetic modelling en
dc.subject.keyword heterogeneous catalysts en
dc.subject.keyword temperature-programmed desorption en
dc.subject.keyword temperature-programmed reduction en
dc.subject.keyword temperature-programmed oxidation en
dc.identifier.urn urn:nbn:fi:tkk-000880
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.contributor.lab Laboratory of Industrial Chemistry en
dc.contributor.lab Teknillisen kemian laboratorio fi
local.aalto.digifolder Aalto_63601
local.aalto.digiauth ask

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