Bachelor, practical courses and master theses occupy an important position in the study program. Bachelor's and master's theses lead to an academic degree and mark the completion of the study section. Guiding students through this work is therefore very important to us.

Within our research areas, we advise the students on the selection of topics and jointly formulate the objectives and tasks of the work. During the work, the students are supported by PhD students and group leaders and the entire team of the research group. The intensive scientific supervision of the students also continues during the planning and writing of the written qualification theses. The individual performance of the students is thus promoted by the team of the working group. Joint leisure activities of the team provide a balance to the scientific work.

Utilization of renewable ressources

Value added chemicals through photocatalytic conversion of CO2

The aim of this work is the photocatalytic conversion of CO2 using sunlight. Using these two abundantly available and renewable resources value added chemicals can be produced in a very sustainable way. In the framework of the project different reaction engineering based concepts for the heterogeneous catalyzed CO2-conversion will be worked out and compared to biological (cell-based) systems. Furthermore, different ways of quantification of catalyst performance (i.e. molar amount of product formed per time and illuminated area) will be worked out. These concepts will then be applied to compare inorganic with cell-based catalysts in the photocatalytic conversion of CO2 using different reactor geometries and setups. Concerning the aimed products of the CO2-conversion special emphasis will be put on creating C-C-coupling products (e.g. oxalates or tartrates) in addition to methane and methanol. These substances can then be used as building blocks in the production of pharmaceutics, bulk and fine chemicals. Using the knowledge gained this way it will be possible to evaluate the potential of sunlight driven photocatalytic CO2-conversion as cornerstone in an integrative bio economy and enable the sustainable use of CO2 as building block to value added chemicals

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Michael Goepel):

  • Synthesis and characterization of photocatalysts based on TiO2, Bi2WO6, BiVO4 and other oxides, as well as polymeric photocatalysts based on g-C3N4 and Graphene
  • Conduction of photocatalytic experiments in the batch mode:
    • Investigations on the influence of process variables (such as gas-pressure, catalyst concentration, pH-value and cocatalysts)
    • Investigations on the influence of the light source (intensity, spectrum)
    • Photoreforming of aqueous methanol solutions as model reaction
  • Development of a concept for the quantification of photocatalytic conversion to enable better comparison
  • Comparison of inorganic catalytic systems with biological (cell-based) catalyst for the photocatalytic CO2-conversion (in cooperation with Umweltforschungszentrum (UFZ Leipzig)

 

Aqueous-phase processing of carboxylic acids

Carboxylic acids like levulinic acid, succinic acid, acetic acid, formic acid, lactic acid and glycolic acid are compounds that are accessible from biomass by chemical or biotechnological processes. They have the potential to serve as important intermediates, so called platform chemicals, in the production of value-added chemicals. Therefore, strategies are required to convert carboxylic acids into useful products efficiently. Aqueous-phase processing is an approach applying heterogeneous catalysis directly on biocatalysis-derived mixtures containing carboxylic acids and large quantities of water. In cases of levulinic acid and glycolic acid, hydrogenation reactions are studies to selectively obtain γ-valerolactone and ethylene glycol, respectively. Both reactions proceed at elevated temperature and pressure over supported metal catalysts. These catalyst systems can be modified in terms of support material, metal phase and additional promoters to influence catalytic activity and selectivity of the hydrogenation reaction as well as the stability of the catalyst in the aqueous phase.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Michael Goepel):

  • Development of Ru-based catalysts for the aqueous-phase hydrogenation of glycolic acid by preparation, characterization and catalytic experiments
    • Influence of support material
    • Influence of the preparation method on bimetallic catalysts
    • Influence of promoters
  • Investigation on the influence of reaction conditions on the heterogeneously catalyzed hydrogenation of glycolic acid by systematic catalytic studies
  • Investigation on the hydrogenation of glycolic acid originating from algae-based photobioreactors

 

Novel bimodal monolithic catalysts for continuous flow reactors

Monolithic reactors offer a lot of potential advantages over common packed bed reactors such as a lower pressure drop, higher external surface area and higher mechanical strength. An important focus in the development of such catalysts are the mass transfer limitations that might occur within nanoporous catalysts, especially for reactions with typically high intrinsic reaction rates, such as hydrogenation and alkylation reactions. This problem can be addressed by developing hierarchically structured catalysts, in which larger pores (meso or macropores) can significantly facilitate transport for a rapid reactant delivery to the active sites and product removal, while the smaller pores (micropores) serve as reaction centers. A rational design of such catalysts implies an optimum between the fraction (and size) of larger pores and the total surface area accessible for catalysis via a smaller pore system and is the aim of this study.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Michael Goepel):

  • Synthesis of hierarchically structured silica-alumina monoliths with different pore sizes and subsequent impregnation with Pt and Pd and/or additional functionalization with acid sites.
  • Characterization of the monolithic catalysts via techniques such as: nitrogen sorption, mercury intrusion, inductively coupled plasma optical emission spectroscopy, hydrogen chemisorption and transmission electron microscopy.
  • Catalytic studies in liquid phase hydrogenation of aromatics or acid catalyzed model reactions such as estrification in the batch and continuous flow mode including analysis of the reaction products via gas chromatography or online UV-vis spectroscopy.

 

Catalysts and reactors under dynamic conditions for energy storage and conversion

As part of a DFG-funded priority program, the work focuses on the conversion and the value addition of CO2 over catalysts operated under dynamic conditions. These catalysts need not only to be highly active in the CO2 conversion to methane or methanol, but also need to tolerate rapid changes in reaction conditions. Hence, the chemical properties and the structure of the catalyst play an important role. To understand the reaction mechanism of the low-temperature methanol synthesis, investigations of the equilibria and kinetics of CO2 sorption are of great importance. The second project part deals mainly with the synthesis of Ni- or Ru-containing, monolithic catalysts with tunable porosity to convert CO2 to methane. By developing hierarchically structured catalysts with a high catalytic activity the understanding of mass and heat transport within the catalyst should be understood.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Juliane Titus)

  • Investigation of CO2 sorption kinetics in functionalized mesoporous silicas by breakthrough experiments
  • Synthesis of monolithic, Ni-containing Al2O3 or ZrO2 catalysts
  • Generation of hierarchical pore networks and control of pore size distributions in monolithic Al2O3 to reduce transport limitation effects
  • Investigations of the affinity of CO2 on alumina-based catalysts

Innovative catalytic systems

Influence of alkyl structures on the epoxidation of fatty acid methyl esters (FAMES) over hierarchically structured TS-1

Titanium-substituted silicate 1 (TS‑1) is one of the most important catalyst in the oxidation of organic molecules with diluted hydrogen peroxide. The expected mass transfer limitations using microporous TS‑1 in the epoxidation auf FAMES can be reduced by introducing additional porosity (resulting in a bimodal or hierarchical pore system). In addition to that the catalytic activity of TS-1 can potentially be engineered via modification of the hydrophobic properties. For this purpose, composite catalysts consisting of TS-1 and activated carbon are synthesized and investigated in the epoxidation of FAMES.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Michael Goepel):

  • Synthesis and characterization (for example via: nitrogen sorption, mercury intrusion. X-ray diffraction, scanning electron microcopy and thermogravimetric analysis) of TS-1 and hierarchical TS-1 synthesized via top-down and bottom-up approaches
  • Evaluation on the influence of the pore system on the activity of TS-1 in the epoxidation of FAMES
  • Investigations on the influence of hydrophobicity of TS-1/activated carbon composite catalysts in the epoxidation of FAMES.

 

Immobilization of organocatalysts on spherical, nanoporous silica for use in microfluidic systems

The focus of this work is the immobilization of organocatalysts on spherical, nanoporous silica materials with different pore structures. Model reactions are applied to study the catalytic activity and selectivity of the synthesized solid catalysts. In addition to the influence of the pore width distribution and the pore arrangement, the influence of the silica’s surface properties needs to be considered. As liquid phase reactions, the α-amination and the Brönsted acid catalyzed Friedel-Crafts alkylation were chosen. The materials to be synthesized are chosen in a way that allows an easy transfer and application in microchip reactors. The results of the macroscale range can then be compared with those from the chip.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Juliane Titus)

  • Synthesis of nanoporous spherical supports for chip-based microreactors.
  • Phosphorylation of silica-based support materials for Friedel-Crafts alkylation.
  • Comparison of industrial catalysts with innovative Brönsted acid catalysts for the Friedel-Crafts alkylation in a batch and flow reactor (synthesis of bisphenols).
  • Investigation of enantioselectivity in α-amination catalyzed by immobilized Jörgensen-Hayashi catalysts in a continuous-flow fixed-bed reactor.
  • Single-particle catalysis: using a TEMKIN reactor to characterize individual catalyst particles.

 

Novel support materials for enzyme immobilization

Compared to chemical catalysts enzymes show benefits in concerns of mild reaction conditions and chemo-, regio- and stereoselectivity. Besides the benefits of bio-catalysis for the use in green and sustainable processes, enzymes show disadvantages by application in solution. The recycling and reuse is almost not possible. Additionally, they have a short-term stability and produce high costs for isolation and purification. These disadvantages can be overcome by immobilization on support materials. Silica materials can be used as support due to their thermal, mechanical and chemical stability as well as adjustable pore width. New silica-support materials inhibiting hierarchical pore structure should be synthesized and characterized and their qualification for application in bio-catalysis should be tested.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. David Poppitz):

  • Synthesis of hierarchical silica support materials with adjustable pore width by pseudomorphic  transformation
  • Characterization (e.g. nitrogen sorption, X-ray powder diffraction, scanning electron microscopy)
  • Enzyme immobilization and determination of the catalytic activity
  • Preparation of electron transparence samples for characterization in the transmission electron microscope (TEM)
  • Imaging, evaluation and processing of three-dimensional electron-tomography data

Emission reduction

Investigations on aging behavior of catalysts for the selective catalytic reduction of NOx containing exhaust gases in presence of ammonia

Current and future NOX emission standards for vehicles can be met by using the NH3-Selective Catalytic Reduction (SCR) process for NOx reduction in the exhaust gas. During the lifetime of a vehicle, the SCR catalyst undergoes an aging process. This leads to deactivation and lower NOx reduction performance.

To understand the deactivation process and the changes of the catalysts material properties during aging in the vehicle, deactivated catalysts need to be characterized. Those include vehicle-aged as well as synthetically aged catalysts. Catalytic experiments are used to find correlations between material properties and the NOx reduction performance. The work will be carried out in the context of a research project with close contact to industry.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Magdalena Jablonska)

  • DRIFTS investigations on adsorbed NO, NH3 and pyridine on aged SCR catalysts
  • TPR/TPO method development and studies on aged SCR catalysts

 

Development of catalysts for low temperature selective catalytic reduction of NOx-containing exhaust gases in presence of ammonia

The abatement of NOx from industrial exhaust gases of stationary sources is conducted by selective catalytic reduction (SCR) with ammonia as reducing agent. Commonly used catalysts are V2O5-WOx/TiO2 or V2O5-MoOx/TiO2. With the aim of achieving a more energy-efficient SCR-process, new low-temperature-active catalysts have to be developed to lower the reaction temperature from 400 °C to 200 °C. For this purpose, the ecologically critical V- and W-oxides should be substituted by cheap and less harmful Mn-, Fe- or Cu-oxides as catalytically active components. With the objective of obtaining the denitrification of exhaust gases at low temperatures, catalysts with a support of alumina or titania shall be prepared and comprehensively characterized by physico-chemical methods. For the elucidation of SCR-activity and resistance to catalyst poisoning through H2O and SOx on-line IR-spectroscopic and temperature programmed investigations of the adsorption/desorption of NOx and NH3 in dry gas-flow and in presence of poison will be conducted. Since especially the long-time stability of the catalysts is of interest for practical application, investigations of the activity for NH3-SCR over multiple days both in presence and absence of catalyst poisons will be carried out.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Wladimir Suprun):

  • Synthesis and characterization of transition metal oxide containing catalysts for low- temperature SCR-deNOx based on deactivated VWT-catalysts
  • Investigation of the adsorption of NH3 and NOx over poisoned MnOx-containing catalysts for low temperature SCR
  • Effects of TiO2 support materials on the activity of MnOx/TiO2 catalysts for low temperature NH3-SCR
  • Investigation of long-time stability and poisoning of MnOx-containing SCR catalysts
  • Synthesis and characterization of “core-shell” low temperature SCR catalysts based on alumosilicate supports

 

Hierarchical micro-/mesoporous systems dedicated to the selective ammonia oxidation into nitrogen and water vapor.

The selective catalytic oxidation of ammonia into nitrogen and water vapor (NH3-SCO) seems to be the most promising method for elimination of NH3 from diesel cars – AdBlue system (the selective catalytic reduction of NOx by on-board generated NH3 from urea solution). Currently commercially applied, Pt-based catalysts provide high activity, however also low selectivity to N2 (especially above 573 K). Among evaluated materials, Cu- and/or Fe-containing zeolites present a class of highly active, N2 selective and stable catalysts (also in the presence of H2O). However, NH3-SCO can be controlled by the intra-particle diffusion due to the microporous nature of zeolites. The existence of mesopores may facilitate the transport of the reactants to and from the active surface sites, and thus, enhance ammonia adsorption and its oxidation. In view of these challenges, investigations aim to obtain a deeper understanding of property/activity relationships over metal-containing zeolites with micro-/mesopore systems in NH3-SCO.

Topics for bachelor and master theses as well as practical courses (contact person: Dr. Eng. Magdalena Jablonska):

  • Preparation and physicho-chemical characterization of mono-/bimetallic micro-/mesoporous zeolites
  • Study of the catalytic activity, selectivity and stability in the selective ammonia oxidation into nitrogen and water vapor over applied materials
  • Investigation of the influence of the kind and/or content of transition/noble metal introduced in the materials and the preparation methods (ion-exchange, impregnation, etc.) on their activity, N2 selectivity and stability in NH3-SCO
  • Correlations between texture (microporous or hierarchical systems), physico-chemical properties of the supports and catalysts and their activity, N2 selectivity and stability in catalytic test

Diffusion and reaction dynamics

Titanosilicate molecular sieve ETS-10 is a microporous material that can be used as a catalyst in acid- and base- catalyzed reactions. One such example is conversion of oils with methanol to fatty acid methyl esters as a reaction product. The project will include preparation of ETS-10 and the post-synthetic treatment with hydrogen peroxide aimed at introduction of network of mesopores. Parent and treated materials will be characterized by scanning electron microscopy, X-ray diffractometry, nitrogen sorption and temperature-programmed desorption of ammonia and/or carbon dioxide.

Contact person: Dr. Muslim Dvoyashkin

You may also like

Institute of Chemical Technology

Read more

Publications

Read more