Kinetics of supported palladium catalysts as coatings for the direct synthesis of H2O2
Bachelor's / Master's Thesis / Student Assistant
Background and Motivation
Hydrogen peroxide (H2O2) is an environmentally friendly oxidizing agent with promising future potential: It is estimated that the current annual production of three megatons will continue to rise to more than five megatons within the next five years. The standard process for industrial H2O2 production is the anthraquinone process. However, due to the many process steps and the limited reusability of organic anthraquinone, this process does not allow a decentralized H2O2 production.
The direct synthesis of hydrogen peroxide on the other hand is an attractive synthesis route in which both molecular hydrogen and oxygen are contacted with a heterogeneous catalyst in a single reaction step. In recent years, intensive research has been conducted on the understanding of the reaction mechanism as well as on new reactor concepts in order to achieve a knowledge-based increase in intrinsic and reactor selectivity, which currently stands in the way of the industrial implementation of this method. The reason for this is that in addition to hydrogen peroxide, water is produced thermodynamically favoured as a by-product in various subsequent and parallel reactions.
At IMVT a novel membrane microreactor is used to overcome these reaction engineering challenges. A polymer membrane allows a bubble-free dosing of the reactants H2 and O2 into the liquid reaction medium which continuously flows through the reaction channel. Due to the alternating dosage of the reactants, the hydrogen peroxide concentration is not limited by the saturation concentration of the gases, as the consumed substances are always "replenished". At the same time, specially developed 3D-printed channel inserts, so-called flow guiding elements, enable an intensified contact of the gases with the reaction medium. At the same time, these structures serve as carriers for the required catalyst.
Figure 1: Scheme of a Fluid Guiding Element with catalytically coated surfaces , adapted from  (left), reaction pathways of the direct synthesis of hydrogen peroxide (right)
For the further optimization of the catalyst synthesis and for the simulation of the reactor, data on the reaction characteristics are required, which can numerically represent the conversion / selectivity behavior of the catalysts within the relevant concentration range. The reactant concentrations can be quantified, among other things, with the aid of electrochemical sensors developed at IMTEK (University of Freiburg) within the framework of a DFG research project (http://www.promise.kit.edu/english/subprojects_catalysis.php).
Within the scope of a of a thesis (bachelor´s or master´s thesis), or a student research project (HiWi), the kinetic parameters of supported (bimetallic) Pd catalysts are to be determined experimentally. The focus is on the determination of concentration dependencies at constant temperature. The selectivity is to be determined from experiments with a continuous flow reactor with coated inserts.
Depending on the scope of the work and the background of the student, it is desired to extract the kinetic parameters by fitting the experimental data to kinetic time laws in MATLAB® routines.
The scope (bachelor's or master's thesis) and the focus of the thesis can be defined by individual consultation. The project is addressed at students of the faculties of chemistry or chemical engineering.
- Design of an experimental plan
- Carrying out the tests
- Fitting the experimental data in MATLAB®
- Students of chemical engineering / process engineering / chemistry
- Presentation of the results of the work within an institute seminar
- Language: English or German
Start: by arrangement
Examiner: Prof. Dr.-Ing. Roland Dittmeyer
Supervisor: Laura Trinkies (laura.trinkies∂kit.edu)