čas: 21.4.2021 19:44:58
Obnovit | RAW
Institute of Chemical Process Fundamentals of the CAS, v.v.i.
List of available PhD theses
Application of microreactors for study and optimization of reactions in field of fine chemicals and pharmaceuticals
Microreactors presents devices with small internal dimensions providing unique features for precise chemical processes control. These features are often employed for continuous processes control in field of fine chemicals and pharmaceuticals, where high product quality is required. Despite the high potential for improvement by synthesis in flow, the batch processes still prevail in industry. This thesis proposal therefore aims at the microreactor technology application, adaptation an optimization for continuous synthesis of fine chemicals and pharmaceutical components. The candidate should have a good knowledge of chemical and reaction engineering, organic chemistry and has good relation to experimental laboratory work to become familiar with microreactor technology, as well as with data acquisition and evaluation systems. To complete the delegated tasks, the personal abilities such as independence, creativity, open mind and team work skills will be required.
Design and optimization of 3D printed catalytic supports for gas-liquid flow conditions
3D printing technology provides new possibilities for the design and fabrication of chemical reactors and catalyst supports. Principally it brings the possibility to tailor the device or catalyst support to the selected process. Therefore, this work’s objective is the design and 3D printing of an optimal structure of catalyst support that is tailored to a model heterogeneous reaction. The optimized design will result from an experimental study of single- and two-phase flow hydrodynamics through structured fillings and process modeling by CFD (OpenFOAM, ANSYS Fluent). The candidate should have a good knowledge of chemical and reaction engineering and have good computer skills to learn data acquisition and evaluation systems, mathematical modeling software and 3D printing process. To complete the delegated tasks, personal abilities such as independence, creativity, and teamwork will be required.
Dynamics of multi-phase systems: gas-liquid-solid
Multiphase systems are all around us, in nature and in industry technologies and applications (sedimentation, fluidization, bubble columns, flotation apparatuses, etc.). Due to the complexity and applicability of these systems, it is seriously worth to study their hydrodynamic aspects. The present PhD research will focus on the experimental and theoretical description of processes controlling multiphase dispersions at microscale level (like bubble coalescence, bubble-particle collision) and their consequences on the flow regimes at the macroscale level (bubble columns, flotation apparatus, etc.). The obtained results will be valuable in many industrial applications (chemical and oil industry, food processing, metallurgy, pharmaceutical and environmental industry). Requirements
• Master degree in chemical or mechanical engineering, or physics and mathematics
• ability and willingness to study
• creative approach and team-work
Formation of microparticles from natural extracts using supercritical CO2
Natural extracts are marketed in the form of liquid, viscous preparations or as powders resulting from the drying of the liquid extract. Formation of powdered extracts helps to decrease the storage costs and increase the concentration and stability of active substances. However, conventional drying methods (spray drying, lyophilization etc.) have several disadvantages, such as the degradation of the product, contamination with organic solvents, and the production of large sized particles. More gentle technic for precipitation and particle formation is a supercritical antisolvent process (SAS). In the SAS process, a liquid solution of a solvent and a bioactive substance is injected into a supercritical fluid, which acts as antisolvent. This leads to supersaturation of the solute, which is compensated by nucleation and particle growth. The aim of the thesis is to evaluate the effects of pressure, temperature, solute concentration etc., on the properties of the particles produced by SAS from particular plant extract. Requirements:
• University degree in food chemistry and technology, natural substances, chemical engineering or organic technology.
• Positive and systematic approach to work duties, motivated, reliable.
Green, greener, greenest: thermodynamic properties of aqueous solutions of bio-based ionic liquids
The aim of this project is to gain a better understanding of the structure-property relationships in aqueous mixtures of choline-based ionic liquids (ILs) with various anions. Thermophysical and thermodynamic characterization of new ILs and their aqueous mixtures will be performed. Ionic liquids in general show a pronounced application potential e.g. in energy storage or separation processes. Furthermore, the relation between their structure and properties remains to a large extent unclarified, due to a very large number of structures that could be synthesized. Understanding these relationships in bio-based ionic liquids are particularly interesting in this regard. Water as one of the most ubiquitous and possibly greenest solvent is then a substance of choice when it comes to understanding the properties of mixtures. Required education and skills
• Master degree in physical chemistry, organic technology, chemical physics, chemical engineering;
• willingness to do experimental work and learn new things;
• team work ability.
Hydrogels and their nanocomposites
Hydrogels are cross-linked polymers containing a large amount of water. They can be used, for instance, in medicine (contact lens, wound dressing materials, tissue engineering), and in vaste water treatment (they exhibit high adsorption ability for organic dyes). When suitable nanoparticles (mostly anorganic) are incorporated into a hydrogel structure, hydrogel nanocomposites are formed. They often exhibit even better physicaly-chemical properties than original hydrogels – typically their rigidity increases, and water swelling, pollutants adsorption or drug releasing ability changes. In this project, the preparation of novel hydrogel nanocomposites, their physicaly-chemical properties and potential using in the field of medicine and environmental engineering will be studied. The candidate should have a M.Sc. degree in chemical engineering, physical chemistry, or in a similar applied science field. Some experimental skill is appreciated. However, the enthusiasm for scientific work is only the principal requirement.
Hygroscopicity of aerosol particles
Hygroscopicity of aerosol particles is their ability to bind air humidity. This changes their shape, size and phase behavior. Hygroscopicity affects the ability of particles to become cloud condensation nuclei, their optical properties, global climate change, and human health. The aim of the project is to study hygroscopicity of aerosol particles in the laboratory and in the atmosphere. In the laboratory, aerosol particles composed of substances commonly found in atmospheric aerosols will be generated and their hygroscopicity studied using HTDMA spectrometer. At the National Atmospheric Observatory Kosetice, atmospheric aerosol will be sampled using spectrometers HTDMA, SMPS, APS and AMS. Moreover, samples on filters and impactors will be analyzed in the laboratory. Experimental results will be compared with model predictions.
Laser and heat-induced redox processes for deposition of novel structures for solar-light photocatalysis
There is great ongoing interest in semiconductors including TiO2-based materials due to their potential in solar energy-to-electric conversion (solar cells) and solar energy-to-chemical energy conversion (water splitting and photo-catalyzed degradation of pollutants in atmosphere and water). Much recent attention to improve these materials for efficient solar-light catalysis is documented in the literature. In this project we propose a novel approach to these materials based on redox paths between metal oxides, which are induced by laser excitation and conventional heat treatment. Highly non-equilibrium deposition conditions due to laser excitation are expected to affect the electronic structure and reactivity of potential reactants to form products not observed under ambient conditions.
Mixing and segregation of granular materials
Unlike liquids, the issue of segregation must also be addressed when mixing granular systems. Granular systems contain a large number of particles. However, the individual grains are not identical but may differ in size, density, hardness, shape, or other physical-chemical properties. This type of difference during particle motions often ultimately leads to the segregation of material with different properties. Although the segregation is a ubiquitous phenomenon that causes different dynamic behavior of granular particles, the reasons for its formation, intensity, and prediction of the resulting system behavior are not always completely clear. This work investigates the mechanisms of segregation during the mixing process and its effect on the dynamics of granular materials. The research will be carried out mainly using numerical simulations using the discrete element method. Required education and skills
• Master degree in chemical engineering, mathematical modeling, computer science;
• high motivation, willingness to learn new things;
• team spirit.
Modeling of particles adhesion and breakage during processing of powder materials
During the processing of powder materials, intense force interactions occur between the particles, resulting in the particles' adhesion to larger agglomerates or, conversely, their destruction and subsequent breaking. The adhesion of particles due to attractive interparticle interactions connected with particle's deformation is controlled by combining the grains' surface properties and the forces acting on the interacting particles. Particle breakage results from the interaction between the particle's internal strength and the forces acting on the particle. This work aims to describe the influence of adhesion and particle breakage on the powder materials' dynamics and transport properties. The research will be carried out mainly using numerical simulations using the discrete element method. It is assumed that adhesion's origin will be described by the theory of Johnson, Kendall, and Roberts. Models describing elastic bonds based on the definition of stiffness and bond damping will be used for particle breaking. Required education and skills
• Master degree in chemical engineering, physics, mathematical modeling, computer science;
• high motivation, willingness to learn new things, team spirit.
Preparation of nanostructured materials for C2-C3 hydrocarbon generation from CO2 in electrochemistry
Reduction of waste gaseous products in industry anticipates a capture or other form of CO2 decrease. Simultaneously, a burst production of electrical energy from wind farms and/or photovoltaics parks enables an (electrochemical) generation of simple hydrocarbons from a waste CO2. Therefore, it is advisable to search for novel electrode materials for effective electrochemical reactions. The materials will be based on selected metal silicides and germanides prepared in nanostructured form. The doctoral student will synthetize the materials using laser chemistry and CVD and study by means of analytical techniques available in laboratory.
Strength and fluidity of granular media
Mechanics of granular media (sand, clay, silt, debris, etc.) is central to many problems in geology and technology. Natural hazards such as earthquakes or landslides are triggered by mechanical instability of embedded granular gauges. On the other hand, conditions leading to good fluidity of granular media are often sought in civil engineering, pharmacy, and chemical technology. Therefore, understanding of mechanisms controlling the strength of granular media is of high importance. The student will run computer simulations of a shearing granular layer and will study conditions leading to flow. The resulting theoretical picture should enlighten mechanisms that are most effective in degrading mechanical strength. In particular, the effect of pore fluid and oscillations of boundaries will be studied in detail. Required education and skills
• Master degree in chemical engineering, physics, geology, mathematical modeling, computer science;
• high motivation, willingness to learn new things;
• team spirit.
Study of bubble and drop interactions with a vortex structure
Gas-liquid or liquid-liquid dispersions are encountered in numerous technological and biotechnological processes. The fluid particles (bubbles or droplets) break in the turbulent liquid flow and form a complex multiphase system. Understanding the particle breakup mechanism at turbulent flow conditions is important because theoretical models describing this mechanism are essential for the numerical modeling of complex multiphase systems. The postgraduate project will be focused on the experimental study of dynamic behavior of bubbles and drops after their interaction with a turbulent vortex in order to determine the breakup rate of original particles and the size distribution of newly formed particles. The breakage mechanism will be studied in dependence on various hydrodynamic and physico-chemical conditions of the studied system. Department is well equipped for the study of bubble/drop breakup in turbulent flow. Cells for controlled generation of bubble, toroidal vortices and intense turbulent flow are available, as well as all the control and evaluation software. Requirements for the applicant: master degree in chemical or mechanical engineering; ability to teamwork; systematic and creative approach to scientific problems; interest in experimental work.
Study on transformations of organic aerosols
Secondary organic aerosols (SOA) as important components of atmospheric aerosols influence Earth’s climate, human health and life expectancy. They are produced by atmospheric photooxidations of anthropogenic and biogenic volatile organic compounds (BVOCs) via gas-to-particle conversion. Terpenes and isoprenes belong to the most abundant chemical species detected in BVOC emissions. They can be oxidized to form semi- and low-volatile carbonyls, acids, and other products, transitioning between gas and particulate phase. To correctly describe these transformations by mathematical models, knowledge of thermodynamic and transport properties of these compounds is needed. The doctoral student will study these phenomena using advanced aerosol instrumentation including on-line chemical and physical characterization of particles by mass spectrometry.
Transformations of aerosol particles due to changes in gaseous environment
The aerosol particles are omnipresent in the atmosphere, influencing many processes on the Earth starting from the global warming to health effects. They tend to be both in physical and chemical equilibrium with their gaseous environment, but due to dynamic changes in the atmosphere or during their transport to human lungs, the particles change during their lifetime. Therefore, it is necessary to study their answers to these changes to be able to predict their fate and effects after their release to or formation in the atmosphere. The study will be carried out using a newly developed system of laminar flow reactors enabling to control ambient conditions of particle neighborhood. The doctoral student is supposed to study these phenomena using advanced methods of aerosol instrumentation including on-line chemical and physical characterization of particles by aerosol mass spectrometry. Required education and skills
• Master degree in chemical engineering, physical chemistry, organic technology, chemical physics, meteorology ... ;
• willingness to do experimental work and learn new things;
• team work ability.