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Modelling of xylene isomerization on structured zeolite catalysts
2005 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Xylene isomerization is a powerful probe reaction to characterise the catalytic activity of a ZSM-5 catalyst. This is due to the catalyst’s diffusional and steric ability, also known as product and transition state selectivity. ZSM-5 is also widely utilised for the manufacturing process of the xylene isomers, in particular the para-xylene. Para-xylene enhancement is highly desirable in the chemical process industry, as this xylene isomer is a vital component for the manufacturing process of useful products, such as packaging material. Finding a numerical model that provides highly accurate measurements of the ZSM-5 catalytic properties during manufacture will therefore be beneficial. It has been theoretically proven that high diffusional limitations on ZSM-5 catalysts can result in higher yield of para-xylene. The aim of this project was to develop a valid numerical model for xylene isomerization that considers high diffusion limitations. The triangular model is an attempt to provide a more direct relationship between the model parameters and the physical properties of a ZSM-5 catalyst. The model is strongly influenced by the research that James Wei published in 1982. The project procedures involved using an existing valid numerical model “the linear model”, the triangular model, simulated and experimental data. The data were implemented in the linear model at first. Numerically simulated and experimental concentration data were acquired from the model. The retrieved concentrations were later employed in the triangular model, obtaining simulated and experimental rate constants. Interpreting the rate constants results was used as a validation of the triangular model. The numerical models were based on ZSM-5 film catalyst with slab shaped crystals. External mass transfer resistance was neglected in the models. The models also considered the microporous region (configurational region). As a result of this, only the intramolecular mechanism of the xylene isomerization reaction was considered. Experimental data from ZSM-5 films on sand, quartz and alumina supports from previous work was utilized. The film thickness of the samples was 150, 230, 800 and 2300 nm. A tubular reactor operating at 450 Celsius was used in the experiments. Its characteristics and evaluation is only mentioned briefly in this thesis. Conclusion from the project was: - The triangular model was denoted as not valid.

Place, publisher, year, edition, pages
Keyword [en]
Physics Chemistry Maths, Xylene
Keyword [sv]
Fysik, Kemi, Matematik
URN: urn:nbn:se:ltu:diva-56634ISRN: LTU-EX--05/028--SELocal ID: d639d55d-b5c8-4851-84c9-396e5192fe7dOAI: diva2:1030021
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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