Structured microreactors for the heterogeneously catalyzed gas-phase dehydration and partial oxidation of 1-butanol

Structured microreactors are considered as a tool to study catalytic activity and intrinsic kinetics because of their characteristic mass and heat transfer advantages. In this thesis, microreactor structures coated with catalysts (γ-Al2O3, Au/TiO2, Pd/TiO2 and Au-Pd/TiO2) were applied to study the activity and to investigate the kinetics of the heterogeneously catalyzed gas-phase reactions in dehydration and partial oxidation of 1-butanol. In addition, the morphology and durability of the prepared noble metal catalyst coatings (Au/TiO2, Pd/TiO2 and Au-Pd/TiO2) were studied. A structured microreactor coated with γ-Al2O3 catalyst having a layer thickness of 15-30 µm was used for the heterogeneously catalyzed gas-phase dehydration of 1-butanol. The kinetic parameters were estimated from the produced experimental data. A dynamic 2D plug flow reactor type model with diffusion-reaction in the catalyst layer confirmed insignificant internal mass transfer resistances and prevalence of the kinetic regime. A computational fluid dynamics study using 3D and 2D-axisymmetric models incorporating fluid flow non-idealities, revealed the presence of axial and radial concentration gradients. The insights from the simulations revealed the catalyst layer thickness and the microchannel dimensions as key parameters to improve the performance of microreactors applied for the heterogeneously catalyzed gas-phase reactions. New heterogeneous catalyst coatings of titania-supported mono- and bimetallic gold and palladium were prepared and tested for the 1-butanol partial oxidation. A sol-immobilization method was used for catalyst preparation and coatings were prepared via a suspension method. A layer thickness of 17±7 µm with an average metal nanoparticle size of 3.6 nm was achieved. The Au/TiO2 catalyst coatings were most selective towards n-butyraldehyde, whereas Pd/TiO2 and Au-Pd/TiO2 catalysts were more selective towards propene, CO and CO2. The kinetic experiments were performed using Au/TiO2 coated catalyst. Kinetic modeling was performed by applying 1D-pseudohomogeneous plug flow reactor type model and dynamic 2D model incorporating axial dispersion effects in gas-phase. The model simulations reproduced the experimental data. In this thesis, preparation of active, selective and durable Au/TiO2 coated catalysts was demonstrated. The activity of the prepared Au/TiO2 coated catalyst was reproducible for 57 tested runs that is reported, in the author's knowledge, for the first time for the nanogold catalyst. In addition, kinetic modeling and reactor simulations were performed successfully to describe the system dynamics of both the dehydration and partial oxidation reactions of 1-butanol.