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    Selective oxidation of ethylene to ethylene oxide on silver catalysts at industrial conditions: reactor profiles, kinetics and chlorine inhibition
    (2025)
    Berg, Viktor
    ;
    Horn, Raimund
    In this work, the direct epoxidation reaction of ethylene to ethylene oxide and the influence of cofeeding halogenated hydrocarbons was investigated. Kinetic investigations were conducted to determine intrinsic parameters using a newly designed and constructed isotherm fixed-bed reactor and a compact profile reactor (CPR), which was used to fit the kinetic parameters from measured concentration and temperature profiles at industrial reaction conditions. Also, the CPR was used to study the mechanism of chlorine moderation of the supported silver catalyst, revealing the competitive adsorption behavior of chlorine and oxygen on the same active sites. A pilot-scale reactor was designed and built to validate the kinetic parameters by a 2D pseudohomogeneous profile simulation.
    Publicationtype: Doctoral Thesis
      66  126
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      83
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    Strategies and process development for particle formation from aquasolv lignin and innovative applications into consumer goods
    (2022)
    Gil Chavez, Gilda
    ;
    Smirnova, Irina
    Aquasolv lignin is a high-molecular weight biopolymer obtained after the pre-treatment of lignocellulosic biomass with liquid hot water (LHW) under elevated pressure followed by enzymatic hydrolysis. Due to its free-of-solvent nature and vegetal primary source, lignin applicability opens to high value products as the case for cosmetic, food and pharmaceutical industries. However, current process yields a heterogeneous material and does not control characteristics such as particle size and morphology, such features being important due to their direct impact in biological behaviour and technical properties; for instance, bioavailability, flowability and solubility in pharmaceutical excipients. The selection of an appropriate method to obtain particles with controlled mean size appears crucial to further product development and formulation. In this regard; a whole process line from crude biomass to lignin powders for the food and pharmaceutical industries has been developed. In the present study, the focus was to tailor the final quality of the lignin in terms of particle size and water content by using spray drying technology. A three-factor central composite rotatory design was used, and the independent variables selected for the set of experiments were inlet temperature, nozzle pressure and feeding rate. The effect of these factors and their interaction was studied and used to model the particle formation and properties of lignin. A thorough evaluation of the bioactive properties and cytototoxicity of the obtained AS lignin particles was assessed in vitro, and for the first time, the non cytotoxicity and hypocholesterolemic effect of AS lignin was demonstrated in vivo in a rat model. The results of this thesis are the basis for further valorizing lignin from second generation biorefineries and apply the material into valuable product formulation by using the principles of particle engineering design.
    Publicationtype: Doctoral Thesis
      220  878
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    Automatisierte Probennahme- und Verarbeitungstechniken für metabolische Stoffwechseluntersuchungen von Mikroorganismen
    (2022)
    Hans, Enrico
    ;
    Zeng, An-Ping
    The work deals with the further development of an automated rapid filtration for microorganisms at biomass concentrations of up to 32 g/L. It could be shown that external influences such as a strong foam formation has no influence on the quality of the results and that a reduction in the sample size can allow a rapid filtration under one second, which could not be realized so far In the cultivations carried out, the influence of a genetic modification of a Corynebacterium glutamicum could be shown. With a developed spiral separator, a separation of particles in the micrometer range and their original liquid could be realized and a formal relationship could be described.
    Publicationtype: Doctoral Thesis
      163  623
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    Item type:Publication, Access status: with files ,
      120  358
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    Experimental and numerical investigation of particle-fluid systems in geotechnical engineering
    (2021)
    Kanitz, Manuela
    ;
    Grabe, Jürgen
    The macroscopic behaviour of saturated soil is complex and driven by the interaction of pore water and soil grains at particle-scale level. This PhD-thesis is concerned with the numerical and experimental investigation of particle-scale physics in saturated soil. Unresolved coupled CFD-DEM is used for the numerical simulations. Four different geotechnical problems are investigated, where fluid-particle interaction forces have a significant influence. The numerical and experimental results are compared to identify the limits and benefits of unresolved CFD-DEM in geotechnical engineering.
    Publicationtype: Doctoral Thesis
      423  746
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    Aeration control of solidifying lipid matrices
    (2020-02)
    Ehlermann, Linda
    ;
    Smirnova, Irina
    Aerated chocolate is one important lipid based product and its texture differentiation is of great importance for the food industry. The aim of this project is to find the most suitable process control for various dimensions of consumer preference. The high pressure aeration was experimentally investigated with the aim to develop a kinetic model of foam formation. It was found, that the differentiation through product texture can be realised by varying the chocolate composition or the process parameters. A MATLAB Model for the prediction of bubble formation, growth and coalescence was successfully developed and evaluated. This findings could further enable a better control of the chocolate aeration process to obtain the production of various aerated chocolate products.
    Publicationtype: Doctoral Thesis
      349  1459
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    Item type:Publication, Access status: without files ,
      116
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    Stabile Amylasen für die biotechnologische Anwendung : Screening und Charakterisierung
    (Mensch und Buch Verlag (mbv), 2019)
    Meyer-Heydecke, Neele
    ;
    Antranikian, Garabed
    Publicationtype: Doctoral Thesis
      71
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      81