MASTER OF SCIENCES. Master Thesis - 30 ECTS credits Spring 2018 (Semester 4)

Size: px

Start display at page:

Download "MASTER OF SCIENCES. Master Thesis - 30 ECTS credits Spring 2018 (Semester 4)"

Teresa Clarke
6 years ago
Views:

1 Synthetically Aged Catalysts for NH 3 -SCR of Biodiesel Off-Gas University: Universität Leipzig Laboratory: Institute of Chemical Technology Prof. Dr. Roger Gläser / (-300 secr.) roger.glaeser@uni-leipzig.de The exhaust gas of diesel vehicles is a major source of nitrogen oxides (NO X ), which are produced at high temperatures during the combustion process in the engine. NO X are harmful pollutants and can cause acid rain, smog and ground-level ozone. Thus, an aftertreatment of the diesel exhaust gas is necessary. Current and future NO X emission standards can be met by using the NH 3 - Selective Catalytic Reduction (SCR) for NO X 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. Aim of the Project is a deeper understanding of the deactivation of NH 3 -SCR catalysts due to their operation using modern liquid biofuels such as biodiesel. In particular, a rapid test for the quantitative evaluation or estimation of the long-term stability of those catalysts is to be developed. The time-to-market of novel biofuels and novel catalysts systems is currently largely dependent on time consuming test runs in vehicles for the long-term stability of catalysts. By using a lab scale based rapid-test, the time-to-market could be shortened significantly. For this purpose, poisoning experiments with commercial monolithic catalysts will be conducted. In particular, different poisoning methods (gas phase/liquid phase poisoning) will be used on V 2 O 5 -WO 3 /TiO 2 (VWT) or on zeolite catalysts. The goal is to achieve equal deactivation and catalyst properties compared to long-term field-aged catalysts in a significantly reduced amount of time using a lab-based poisoning procedure. In the Master Thesis, poisoning experiments will be conducted using gas- and liquid-phase poisoning methods. In addition, a novel burner system will be used for more realistic poisoning conditions. The poisoned catalysts will be thoroughly characterized and the catalytic properties of the poisoned catalysts will be compared to the properties of catalysts aged in real vehicles on the road. Spectroscopic methods like Diffuse Reflectance Fourier Transform Spectroscopy (DRIFTS) and X-ray Fluorescence Spectroscopy (XRF) will be used for further characterization to get a deeper insight into the poisoning process. keywords: NH 3 -SCR, catalyst deactivation, exhaust aftertreatment, DRIFTS, XRF

2 Catalytic Studies of Hierarchically Structured Monolithic Catalysts for the Conversion of Benzene with Ethene into Ethylbenzene Main Laboratory: Institute of Chemical Technology Prof. Dr. Roger Gläser/Dr. Muslim Dvoyashkin 0341/ (-300 Secr.) One of the main focuses of modern heterogeneous catalysis research is placed on mass transfer limitations within nanoporous catalysts. For the reactions with typically high intrinsic reaction rates, such as, e.g., hydrogenation reactions, the mass transfer is often a rate-limiting step. To overcome these mass-transfer limitations, hierarchically structured catalysts may be applied. IN these catalysts, larger (meso- or macro-) pores can significantly facilitate transport for a rapid reactant delivery to and product removal from the active sites. However, 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. Thus, understanding of the transport mechanisms of reacting molecular species confined to nanopores of the catalyst becomes an essential prerequisite for improving the efficiency of catalytic reactors for a number of applications. Tasks of the present master thesis include: i.) preparation of hierarchically structured silica-alumina monoliths with different pore sizes by a sol-gel synthesis for liquid-phase conversion of benzene with ethane into ethylbenzene, ii.) characterization of prepared monoliths means of nitrogen sorption, ICP-OES, XRD, and SEM/TEM-EDX, and iii.) performing catalytic experiments in the alkylation of benzene with ethene to ethylbenzene, an important chemical intermediate to polystyrene plastics. These experiments will be carried out in the gas phase under continuous-flow conditions. keywords: benzene alkylation, monolithic catalysts, spectroscopic characterization

3 MgCr 2 O 4 as Novel Catalysts for Photocatalytic Water Splitting Main Laboratory: Institute of Chemical Technology Prof. Dr. Roger Gläser/Dr. Steffen Beckert 0341/ (-300 Secr.) roger.glaeser@uni-leipzig.de Converting solar energy directly into storable chemical energy, e.g., in the form of hydrogen, could be a solution for a carbon-free energy economy based entirely on renewable resources. Through photocatalytic water splitting, hydrogen can be produced by simply suspending a suitable solid photocatalyst in water and irradiating it with sunlight. A novel photocatalytic active material synthesized and investigated in our lab is MgCr 2 O 4. As opposed to materials typically used in photocatalytic water splitting, this material features a counterintuitive, but interesting feature: The rate of hydrogen formed under light irradiation increases with an increasing particle size of the MgCr 2 O 4 particles. In this master thesis, different novel synthesis routes for MgCr 2 O 4 will be reproduced and modified to achieve a reliable preparation and to observe controlled and widespread particle sizes. Furthermore, these materials will be thoroughly characterized by physico-chemical methods (elemental analysis (ICP- OES), XRD, N 2 sorption, SEM/TEM, TGA-DTA) and by photocatalytic experiments in aqueous suspension to understand the nanoscopic mechanisms of the water splitting on these attractive type of material. keywords: synthesis, photocatalysis, water splitting, physico-chemical characterization

4 Salt/Zeolite Composites with Increased Heat Storage Density Main Laboratory: Institute of Chemical Technology Prof. Dr. Roger Gläser/Dr. Steffen Beckert 0341/ (-300 Secr.) Technologies for an efficient energy storage become increasingly important for a stable renewables-based energy supply. For the purpose of long-term heat storage, thermochemical systems based on the sorption of water are of utmost scientific interest. In our group, we investigate composites of hygroscopic salts and zeolite-based granulates. These composites provide superior heat storage densities of up to 260 kwh m -3 as compared to hot water tank storage (sensible heat storage) with about 90 kwh m -3, which is the current state of the art in commercial heat storage devices. The composite materials prepared in our group so far feature a decreased heat storage density as compared to the salt-free zeolite-based granulate at low to moderate salt loadings. This is caused by the so-called inclusion of salt ions into the micropores of the zeolites and, thereby, a blockage and/or shielding of the water adsorption sites. In this master thesis, the objective is to reduce the salt inclusion effect. Therefore, the preferred deposition of hygroscopic salt within the secondary pore system of commercial zeolite-based granulates is addressed. Accordingly, adequate preparation routes and material systems need to be identified. The composites will be thoroughly characterized by physico-chemical methods (elemental analysis (ICP-OES), XRD, N 2 sorption, SEM/TEM, TGA-DTA) to elucidate the microscopic phenomena involved. Moreover, the thermochemical properties will be studied in a lab-scale apparatus allowing for sensitive monitoring of heat storage properties under different conditions relevant to applications in real heat storage devices. keywords: thermochemical heat storage, zeolites, sorption, inclusion, physico-chemical characterization

5 Title: Synthesis and Characterization of Porous Coordination Polymers Main Laboratory: : Institute of Inorganic Chemisty Prof. Dr. Harald Krautscheid and doctoral students 0341/ (36160 Secretary) krautscheid@rz.uni-leipzig.de Metal Organic Frameworks (MOFs), or porous coordination polymers, are interesting crystalline materials for application in adsorption, gas separation, catalysis, proton conductivity etc. The bridging organic ligands and the metal ions or secondary building units (SBU) as network nodes determine the crystal structure including pore size and properties of the inner surface. Our group focuses on synthesis and characterization of MOFs with bridging ligands combining neutral triazole and anionic donor groups (carboxylate or phosphonate). Beside X-ray diffraction methods (single crystal structure analysis, powder diffraction) simultaneous thermal analysis is applied to characterize the new materials; adsorption measurements and catalytic test reactions are performed by our cooperation partners. An additional focus is on structurally flexible MOFs in which interactions between the network and guest molecules cause structural changes. keywords: Synthesis - MOFs - X-ray diffraction - crystal structure analysis

6 Title: Molecular Precursors for Semiconductor Materials Main Laboratory: : Institute of Inorganic Chemisty Prof. Dr. Harald Krautscheid and doctoral students 0341/ (36160 Secretary) krautscheid@rz.uni-leipzig.de Synthesis methods are developed for molecular complexes that contain all required chemical elements for the preparation of inorganic materials. These precursors are investigated regarding their transformation into solid state products and their properties. Examples are polynuclear organometallic complexes containing Cu, Ga or In, S or Se atoms that can be thermolyzed to CIGS semiconductors for photovoltaic cells. keywords: Synthesis - precursor complexes- X-ray diffraction - structure analysis

7 Zeolites with Enhanced Hydrothermal Stability for the Valorization of Biomass Derived Compounds by Aqueous-Phase In-Situ Hydrogenation Main Laboratory: Institute of Chemical Technology Prof. Dr. Roger Gläser/Dr. Nicole Wilde 0341/ (-300 Secr.) Lignocellulosic biomass and its derivatives have been identified as renewable alternatives to fossil resources for the sustainable production of liquid fuels and valuable chemicals. A major challenge for the effective utilization of these sustainable resources is to develop cost-efficient methods for the transformation of highly functionalized oxygenates into value-added chemicals with the aim to supplement and ultimately replace fossil resources. Compared to other processes for the conversion of biomass, aqueous phase processing (APP) is highly energy efficient since it is conducted at mild reaction conditions, i.e., >500 K and 5 MPa. In addition, APP allows the direct conversion of low-value wet lignocellulosic biomass derivatives. For reducing the oxyfunctionality of biomass to achieve value-added products hydrogenation during upgrading is necessary. Up to now, in most investigations added hydrogen gas has been used, which is non-sustainable and expensive. In this context, APP is particularly beneficial, since hydrogen can be generated during the process from, e.g., formic acid, abundant in lignocellulosic biomass. However, the APP imposes new requirements on solid catalysts, especially on the hydrothermal stability of solid supports. Zeolites are of interest as catalysts for APP due to their availability, relatively low cost and structure variety. However, their stability is limited in liquid water even at moderate temperatures under 500 K. In this context, the master thesis aims at a systematic preparation of conventional and hierarchically structured zeolites with enhanced stability for the valorization of biomass derived compounds by APP. The stability of the zeolites will be investigated in the APP. The fresh and spent materials will be thoroughly characterized by N 2 sorption, NH 3 -TPD, UV-Vis- and DRIFT-spectroscopy as well as thermogravimetric and chemical analysis. After selecting the most stable zeolites, mono- and bimetallic active phases supported on these zeolites will be prepared and their catalytic activity will be investigated in the APP of a complex lignocellulosic biomass derived model mixture. keywords: Biomass, Aqueous-Phase Processing, Zeolites, Spectroscopic Characterization

8 Spring 2015 (Semester 4) Title: Carbaboranes as Versatile Inorganic Building Blocks in Biologically Active Molecules University 1: Leipzig University Laboratory: Prof. Dr. Evamarie Hey-Hawkins, Institute of Inorganic Chemistry, Department of Chemistry and Mineralogy PhD students and postdocs of the group (see (secretary ) n.a. Carbaboranes are highly hydrophobic and extremely stable icosahedral carbon-containing boron clusters. The cage framework of these clusters can easily be modified with a variety of substituents both at the carbon and at the boron atoms. We are interested in substituted carbaboranes which can be used in medicine as suitable boron neutron capture therapy (BNCT) agents or as pharmacophores in which the carbaborane replaces the phenyl rings in drug candidates. This topic involves the synthesis of respective compounds, their full characterization by NMR, MS, IR and X-ray crystallography, and for selected examples, test of their biological activity in collaboration with biochemists. keywords: Boron clusters, cancer therapy, biomimetic compounds

9 Spring 2015 (Semester 4) Title: Hybrid Materials: Inorganic Polymers University: Leipzig University Laboratory: Prof. Dr. Evamarie Hey-Hawkins, Institute of Inorganic Chemistry, Department of Chemistry and Mineralogy PhD students and postdocs of the group (see (secretary ) n.a. Strained inorganic phosphorus-based rings will be employed in ring-opening polymerisation or copolymerisation reactions, or catalytic dehydrogenation of suitable precursors will be employed as an innovative route to novel inorganic/organometallic polymers that are more than just carbonbased polymer mimics. These polymers can function as scaffolds, e.g., for transition metals (homoor heterometallic) with applications in catalysis or as novel materials with interesting magnetic (molecular magnets) and optical (non-linear optics) properties. This topic involves the synthesis of respective building blocks, their full characterization by NMR, MS, IR and X-ray crystallography, the preparation of the respective polymers and for selected examples, test of their physical properties in collaboration with physicists and physical chemists. keywords: Inorganic polymers, hybrid materials, applications in catalysis, molecular magnets, non-linear optics

10 Spring 2015 (Semester 4) Title: Tailored Phosphines and their Application in Catalysis University: Leipzig University Laboratory: Prof. Dr. Evamarie Hey-Hawkins, Institute of Inorganic Chemistry, Department of Chemistry and Mineralogy PhD students and postdocs of the group (see (secretary ) n.a. Phosphine-based ligands are designed in which the phosphanyl group is located inside a basket-, bucket- or tub-like cavity. Transition metal complexes thereof should allow selective transformation of molecules (regio-, stereo-, enantioselectivity) depending on the size and shape of the cavity, similar to the function of enzymes (bioinspired synthesis) or zeolites (heterogeneous catalysis). Furthermore, suitable phosphorus-based ligands such as (chiral) ferrocenylphosphines and related bimetallic catalysts (for tandem catalysis) will be immobilised on surfaces (e.g., graphite, gold, silica, etc.) or incorporated in polymers (via copolymerisation). A major target will be to manipulate or vary the properties by external stimuli (electrochemically, UV-vis, ph, etc.). The application of these immobilised molecular switches will be scrutinised with respect to changing the catalytic activity at will and shutting down or activating catalysts to trigger catalytic events. keywords: Catalysis, immobilised catalysts, catalyst design, selectivity, chirality

MASTER OF SCIENCES. Project case study - 10 ECTS credits Autumn 2017 (Semester 3)

MASTER OF SCIENCES. Project case study - 10 ECTS credits Autumn 2017 (Semester 3) Characterization of Nanoporous Catalysts for Heterogeneously Catalysed Transesterification of Oils into Biodiesel Laboratory: Institute of Chemical Technology Tutor(s) : Prof. Dr. Roger Gläser/Dr. Muslim