čas: 23.4.2021 00:05:10
Obnovit | RAW
Department of Organic Technology
List of available PhD theses
Application of milling and co-milling processes to formulation of poorly soluble drugs
Poorly soluble drugs (BCS II and IV classes) represent an important segment of marketed drugs. Improving solubility or at least the drug release kinetics is therefore a continuing challenge, which is approached by many ways on several levels. The milling, nano-milling, and/or co-milling processes of a drug with optional other excipients provide a way how to change the phase composition of the drug, increase the specific surface of drug particles, modify that surface, and also form composite particles. This study should be aimed at the options and possibilities of improving the drug release by all the above mechanisms, especially those related to particle technology. The study should involve both the preparation of particles and their formulation into suitable dosage forms and seek optimized approaches bringing the best performance while complying with the requirements of industrial manufacturability of the formulation.
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.
Layered double hydroxides as sorbents for biologically active substances
Double layered hydroxides, also known as hydrotalcite or anionic clays, are an important group of materials with a wide range of applications. They can be applied as catalysts, catalyst precursors or ion exchangers, in sorption and decontamination processes. They can also be used for the intercalation of various substances including drugs. The aim of this work will be to prepare these materials, modify their surface with silanol based compounds and to characterize them by suitable methods. The prepared materials will be used as support materials for the immobilization of selected active substances.
Mathematical models of composite materials prepared by dispersing solid particles of a filler in a liquid polymer matrix
The work is aimed at the mathematical modelling of composite materials, the preparation of which includes the creation of a suspension of solid particles in a liquid mixture of a solvent and a polymer precursor, volume contraction of the suspension caused by evaporating the solvent and by forming a solid polymer matrix. The initial suspension is modelled using the random sequential addition of particles of various shapes. Then, the motion of particles of the filler in the shrinking suspension is simulated. Each model microstructure and the corresponding microstructure of the real composite material sample are characterised using statistical measures and these measures are subsequently compared with each other for the quality of the model to be evaluated. The real microstructures are deduced from digital images of their polished sections that are observed using a scanning electron microscope.
Modeling of drug release from the solid dispersions by diffusion erosion models
This work is aimed at the study of the drug release from the solid dosage forms comprsing solid dispersions. Such formulations exhibit a well-defined structure, and the drug dissolution can be studied not only by classical dissolution techniques, but also by the apparent intrinsic dissolution. Several fronts develop in dosage forms of this type, where thos fronts corresponds to the liquid penetration, drug leaching and erosion of the residual matrix. Such processes can be described by diffusion-erosion models, which allow determining their rate controlling steps and characteristic rates to be used for the design of controlled release drugs.
Nanoparticulate formulation approaches for topical delivery
Human skin represents a unique protecting barrier which, however, limits the trans/dermal drug delivery. Nanoparticulate systems show a great potential to improve drug permeation across the skin barrier, though their exact interaction mechanism with the skin barrier has not been fully understood yet. The aim of this work will be development and characterization of advanced nanoparticulate systems containing selected actives. Effectivity of the formulations will be determined in vitro on isolated skin or by other techniques. For deeper understanding interactions between the nanoparticles and skin barrier, biophysical techniques (e.g. infrared and Raman spectroscopy or X-ray diffraction) will be applied. The main outputs of the work will be effectivity evaluation of the particular formulation approaches and elucidating of interactions between the nanoparticles and skin barrier.
Prediction and experimental determination of transport properties of mixed-matrix membranes
The work is aimed at simulation and experimental determination of transport properties of mixed-matrix membranes that differ from each other in polymer and filler materials. In addition, the membranes containing different fractions of filler particles will be investigated. Statistical treatment of obtained data will accompany the experimental determination of permeability. Permeability will also be modelled on the basis of reconstructed microstructures of the membranes and transport properties of components forming the membranes.
Preparation of electrospun nanofibrous carriers for deposition of catalyst nanoparticles and immobilization of living cells
The main aim of the proposed PhD project is focused on assessment of the specific properties of the novel polymeric nanofibrous materials prepared by electrospinning technique in applications as effective catalyst supports and promising scaffolds for living cells (in cooperation with the University of South Bohemia). Other targets of this project will be specifically addressed to the optimization of the electrospinning process parameters with respect to properties of the prepared supports, deposition of the catalytically active centers or living cells. Additionally, assessment of the effect of support microstructure on the phenomenological kinetics of model reactions and adhesion of the cells will be performed as well. Studied model reactions will involve both reaction in gas-phase (the total oxidation of volatile organic compounds) and liquid-phase (selective hydrogenation of unsaturated hydrocarbons). Required education and skills:
• Master degree in chemical technologies, chemical engineering or biotechnology;
• methodical and creative approach to work;
• willingness to perform experimental work and learn new issues.
Procedures for design and installation of relief valves in the refinery-petrochemical industry
In the field of industrial safety, relief valves hold a key and absolutely irreplaceable role. They are the last autonomous barrier, which are able to protect technological equipment against overpressure and thus avert extraordinary situations leading often to serious accidents. However, the inappropriate design, setting and operation of these technological elements can paradoxically contribute to the loss of integrity of the equipment during releasing pressure from the protected pressure equipment and cause an even more serious situation. Although the role of relief valves in industrial practice is absolutely indispensable, the relevant theory of their design, selection and appropriate installation is not known to the wider technical community in the field of chemical technology design. The doctoral dissertation thesis will focus on the comparison of international standards and the so-called "best engineering practice" and corresponding recommendations for the design and selection of relief valves. The findings will be compared with industrial practice in the field of refining and petrochemical technologies with different years of installation and commissioning from the 70s of the 20th century to the present. An analysis will be performed on individual case studies, including a detailed assessment of the availability and completeness of operational documentation, definition of individual relieve scenarios, capacity design of a relief valve or a set of relief valves and appropriate design and arrangement of relevant piping systems as well. The calculations will be performed using mathematical models in steady state and dynamic mode in Aspen Hysys, which also contains a specialized tool for assessment and designing relief systems for pressure vessels. Individual tools will be used for calculations and will be evaluated in terms of complexity and usability for common engineering practice. The determination of frequent shortcomings and deviations from standards and recommendations in the relief valve systems design and the resulting risks evaluation will be the output of the doctoral thesis. Basic recommendations for industrial practice will be defined. The verification of relief valves and their modifications on operating technologies and at the same time, new relief valves designing procedures will be described. The individual recommendations will be aimed at minimizing operating and investment costs in compliance with all safety elements and rules.
Processing possibilities of materials derived from thermal cracking of waste polymers
Processes design to dispose of waste polymer material, such as plastics and rubber, are being currently introduced in the industry. In these processes, the material undergoes slow pyrolysis or gradual thermal cracking of original polymers and potentially usable materials are formed. For example, condensed gasses from the process represent a certain kind of fuel and are currently co-incinerated with other fuels in powerful boilers. But these material streams can represent a significant source of hydrocarbon for the industry. A potentially better way is to engage such a material stream into an appropriate node in the refinery-petrochemical complex. Specifically, the steam-cracking process has the potential to transform the stream into valued products. This would replace current energetic use by the material use, which is more valuable in terms of resources usage and usually is economically more beneficial. The composition of these condensates is strongly dependent on the input material and conditions of the primary thermal treatment and therefore the composition varies in a broad range. These condensates may contain valuable hydrocarbons fractions, but also oxygen-, sulfur-, and nitrogen-containing organic compound, halogens, metals in the form of salts, even solid particles which may not evaporate under standard operating temperatures. Therefore, such a material stream cannot be connected directly to the processing, but necessarily will require some form of pre-treatment. Moreover, it is necessary to evaluate the potential impact of these impurities presence on the following process (and next following processes) from many different points of view, e.g. catalyst poisoning in following processing steps, contamination of final product or corrosion, of the equipment.
Solvent effects in acid catalyzed reactions
Acid-catalyzed reactions are of large importance in the production of fine chemicals. The influence of the type of acid catalyst, type of acid sites, temperature, and occasionally pressure on the reaction course is widely studied. Used solvent is often chosen based on preliminary experiments or on literary data. Recently, the trend showing the influence of the solvent on the reaction course is visible. Typically, the properties of the solvent such as basicity and polarity are included in the discussion. The aim of the work will be the study of the solvent's influence on the course of the chosen acid-catalyzed reaction. The influence of the solvent properties will be the goal. Possible synergy between solvent and catalyst from the point of view of selectivity or reaction rate will be evaluated. The used catalysts will be characterized by available methods (XRD,TPD pyridine, IR, UV-Vis, etc.). The interaction solvent-acid site-substrate will be discussed. For the evaluation also theoretically based calculation may be used.
Technological utilization of streams comprising methylated cyclopentadiene derivatives
The Diels-Alder reaction of cyclopentadiene and methylcyclopentadiene forms methyl derivatives of dicyclopentadiene. There are three positional isomers of methylcyclopentadiene therefore the Diels-Alder cycloaddition reactions result in a mixture of a number of co-dimers, referred to as methyldicyclopentadienes (MDCPD) and dimethyldicyclopentadienes (DMDCPD). The mixture of MDCPD and DMDCPD isomers is present in products of the pyrolysis of hydrocarbon mixtures. Due to the chemical reactivity of these co-dimers, the industrial end use can be assumed in applications such as the production of unsaturated polyester resins, epoxy resins or modified hydrocarbon resins. The main objective of the dissertation will be to assess the possibilities of using the mixtures of MDCPD and DMDCPD for the preparation of various types of resins, with regard to the variability in the composition and the presence of methyl groups. The obtained results will define the industrial possibilities of using MDCPD and DMDCPD mixtures and will be used for the conceptual technology design.
Two-dimensional materials as a catalytic support
Two-dimensional (2D) materials exhibit increased catalytic activity in 2D material supported metallic nanoparticles in comparison with their bulk counterparts. The increase in activity attributes to specific 2D support-nanoparticle interactions. The project is focused on an investigation of the specific interactions for graphene, as reference support, and ‘materials beyond graphene’ based on phosphorus, arsenic, antimony, and bismuth. To suggest a mechanism of the specific interactions, we will investigate a spatial-temporally resolved catalytic activity of supported catalyst prepared by lithography and chemical routes. By tuning of a spatial distribution and size of the active sites, we will identify individual contributions, including an exclusive effect of the support, causing the increase in catalytic activity. The suggested mechanism, also verified by standard methods of catalytic testing, will bring a new insight into the understanding of nanoparticles-2D support interaction and open new possibilities for the rational design of 2D material supported metal catalysts.