University of Twente Student Theses


Kinetic modelling of LDPE hydrogenolysis using non-linear regression

Lee, T.K.H. van der (2023) Kinetic modelling of LDPE hydrogenolysis using non-linear regression.

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Abstract:The issue of plastic pollution has escalated in recent decades, with no clear solution for recycling it into usable high-quality materials. One possible method to address this is a low-temperature chemical process called hydrogenolysis which can break down polyolefins into valuable resources such as naphtha. However, there has been limited research on the kinetic modelling of this process, which could potentially offer deeper insights into the chemical and physical occurrences. The reaction process involves a gas phase, initially comprising solely of hydrogen, and a liquid phase with a catalyst, where the hydrocarbons crack into smaller components. This thesis researches how the experimental results can be predicted by a kinetic model when using non-linear regression in Matlab and assuming Knudsen diffusion. The results from the model will be compared to the provided experimental results from the SPT group of the University of Twente. This process will use LDPE feedstock and a porous 5wt% Ru/C catalyst. The purpose of this thesis is to offer more detailed insight into the experimental outcomes and the processes occurring within the reactor. The objective of the research is to attain a model that can accurately forecast the yield, pressure, and residual hydrogen from the experimental results. The model will predict mass transport between the gas and liquid phase, internal resistances of the catalyst, and factors such as the dependence on the hydrogen concentration, changing density and volumes, and the compressibility of the gas phase. The results indicate that the model has a good ability to predict experimental outcomes, with only a few exceptions. After analysing the results, it can be inferred that the yield obtained from the experimental measurements may not be entirely precise and could be higher for certain smaller compounds. The evaporation of hydrogen is also likely not coupled with the evaporation of the hydrocarbons based on the liquid diffusion ratio. Finally, it is not possible to describe the effectiveness of the catalyst solely through Knudsen diffusion. More information about the catalyst characteristics is also needed. These findings hold significant importance as they offer precise suggestions for improving both the experimental measurements and the modelling of the chemical process.
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:35 chemistry, 58 process technology
Programme:Chemical Engineering BSc (56960)
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