master thesis subjects – 2017-2018 - ugent · pdf filemaster thesis subjects –...

LABORATORY FOR CHEMICAL TECHNOLOGY

Technologiepark 914, 9052 Gent, Belgium

T: 0032 (0)9 331 17 56

E.: [email protected]

Master Thesis subjects – 2017-2018

1. Development of a bifunctional material for CO production from CO2 by catalyst-assisted

combined chemical looping

2. Kinetic modeling of the pyrolysis of lignin model compounds

3. Aldol condensation catalyzed by electrospun aminated silica nanofibers

4. Process intensification through reactive flow modulation

5. Reactive CFD Simulations for Oxidative Coupling of Methane in Gas-Solid Vortex Reactor in

Static Geometry

6. Investigation of biomass fast pyrolysis via pyrolytic degradation of model Compounds

7. Mechanistic study of Fischer-Tropsch synthesis

8. Design of a Carbon Neutral Process for the Synthesis of Methanol

9. Reactive CFD Simulations for biomass fast pyrolysis in Gas Solid Vortex Reactors

10. Retrieving intrinsic kinetic parameters using pulsed laser polymerization

11. Kinetic Analysis of Pharmaceutical Reactions : Synthesis of Diphenhydramine

12. Kinetics Simulation in Emission Control: Catalytic Oxidation of Tricholoroethene Plasma

Degradation Products

13. Numerical evaluation of the experimental data resulting from hydrogen permeation

measurements

14. Polarity driven kinetics: Esterifications over ion-exchange resins

15. Mechanistic study of ethanol oxidation on gold silver catalysts

16. Shedding light on Thin Film Solar Cell Performance through fundamental modelling in CAPS-

1D and the microKinetic Engine

17. The μ-Kinetic Engine (μKE): towards a versatile tool for complex feed conversion simulation

and parametric identification

18. Mass transfer in a vortex reactor: experimental and theoretical study

19. Analysing BIG data: QXAS on Ni-Fe catalysts

20. Modeling the formation of oxygenates during Fischer-Tropsch synthesis using the method of

moments

21. Computational investigation of penultimate effects in RAFT polymerization

22. High emissivity coatings in steam cracking furnaces

23. Kinetic modelling of oxidative coupling of methane

24. Microkinetics for methane dry reforming over Fe-Ni-(M)/MgAl2O4

25. Experimental investigation of particle segregation in a Gas Solid Vortex Unit (GSVU)

26. Genesys: automatic generation of kinetic models

27. Computational Fluid Dynamic simulation of heterogeneous catalytic reactors

28. Modeling of non-isothermal controlled radical polymerization reactors

29. Pyrolysis of cyclic and oxygenated compounds: a combined modelling and experimental study

30. Automatic generation of microkinetic models for polycyclic aromatic hydrocarbon formation

during pyrolysis of hydrocarbons

If you need more information about a master thesis subject: contact the referred coach(es) or

promotor(s). Their respective coordinates can be found @ https://www.lct.ugent.be/people

The list has been compiled on 16-Jun-2017.

FACULTY OF ENGINEERING AND ARCHITECTURE

Department of Chemical Engineering and Technical Chemistry Laboratory for Chemical Technology

Director : Prof. Dr. Ir. Guy B. Marin

Laboratory for Chemical Technology • Technologiepark 914, B-9052 Gent • www.lct.ugent.be Secretariat : T +32 9 331 17 57 • F +32 9 331 17 59 • [email protected]

Supervisor(s): Dr. Vladimir V. Galvita

Coach: ir. Lukas Buelens

Development of a bifunctional material for CO production from CO2 by catalyst-assisted combined chemical looping

Aim

The purpose of this thesis subject is to synthesize, characterize and test a bifunctional material for

conversion of CH4 and CO2 into CO by catalyst-assisted combined chemical looping.

Justification

Today, global research interest with respect to mitigating CO2 emissions is shifting from a short-term strategy

of CO2 capture and storage towards a long-term closed-loop approach, CO2 capture and utilization.

Generation of syngas from CO2 and H2O and its subsequent conversion into chemicals or clean fuels can be

particularly interesting when using processes driven by renewable energy. Besides providing a method for

CO2 valorisation, such an approach allows to store renewable energy in times of abundance. The stored

energy can be released in times of shortage.

Here, the objective is to convert CO2 and CH4 into

CO by means of catalyst-assisted combined chemical

looping. This method combines a catalyst for CH4

reforming with an iron oxide and calcium oxide

material. A mixture of CH4 and excess CO2 are

reformed over a catalyst (e.g. Ni) to form syngas. This

syngas reduces the iron oxide material upon its

oxidation to CO2 and H2O. The produced CO2 is fixated

as CaCO3 and, hence, the effluent solely consists of

H2O. The materials are regenerated by decomposition

of CaCO3 to CaO and CO2, which reoxidizes iron oxide while producing CO. This decomposition can be

realized either isothermally by means of a sweep gas, or by elevating temperature. Compared with

conventional dry reforming of CH4, this process allows an intensified production of CO from CH4 and CO2:

Conventional dry-reforming: CH4 + CO2 → 2CO + 2H2

Catalyst-assisted combined chemical looping: CH4 + 3CO2 → 4CO + 2H2O

The high operating temperature (700-800°C) along with structural changes of the

solid materials are known to cause deactivation due to sintering or formation of inert

solid phases. Particle growth due to sintering results in a decrease of the specific

surface area. By means of a mesoporous metal oxide shell (e.g. ZrO2, SiO2, …), a

physical barrier between particles can be formed which will tremendously improve

thermal stability while allowing mass transport through the pores.

Program

Literature survey: (i) CO2 capture and conversion, (ii) synthesis of mesoporous metal oxides and

core-shell structured materials, and (iii) kinetic modelling of solid-gas reactions

Synthesis of a bifunctional material: CaO(core)-MOx(shell)+Fe2O3(impregnated)

Characterization of the prepared materials by SEM, STEM-EDX, TPR, (in situ) XRD, …

Activity and stability performance tests of the materials for catalyst-assisted chemical looping

Kinetic modelling of the separate processes





Supervisor(s): Prof. dr. ir. Kevin M. Van Geem; : Dr. Hans-Heinrich Carstensen

Coach: Dr. Hans-Heinrich Carstensen

Kinetic modeling of the pyrolysis of lignin model compounds

Aim

Development of a first-principle elementary step kinetic mechanism for dimethylfuran pyrolysis and validation against in-house and literature experimental data.

Justification

Furan derivatives including dimethyl furan are easily obtainable through catalytic conversion of the cellulosic fraction of biomass. For this reason, dimethyl furan has been studied intensively in the past few years. Among these studies was a flow reactor experiment performed at LCT, which was published in 2013. Since then, subsequent modelling studies casted doubts about the reliability of this data set. Consequently the experiments were repeated with the same but slightly modified bench-scale setup and indeed, the original data could not be reproduced. However, the product yields found with both sets of experiments are quite comparable and confirm (a) the formation of substantial amounts of phenol, not seen in any other experiment, and (b) the tendency to produce cyclopentadiene and molecular weight growth species. The new experimental data set, which seems to be in good agreement with expectations, has not been published yet.

Although several kinetic models for DMF exist, some contain estimated rate expressions while others seem to use irreversible reactions in order to reproduce experimental data. The relevant potential energy surfaces are incomplete or not developed at all. Despite the number of papers published on DMF chemistry, there is still a lot of room for improvement.

Program

• Literature research on experimental and theoretical furan, methyl furan (MF), and DMF pyrolysis and oxidation studies.

• Familiarization with electronic structure calculations using Gaussian software, and conversion of this data to thermodynamic and kinetic properties.

• Analyze the performance of existing kinetic models for DMF and identify important reaction pathways.

• Explore options to use automated mechanism generation programs such as RMG or Genesys to generate kinetic mechanisms for DMF pyrolysis

• Perform ab initio calculations on potential energy surfaces needed to develop an improved DMF mechanism.

• Validate the new model against all available data. Identify the important DMF converting reactions and the chemistry leading to oxygen-free aromatic species.

FACULTEIT INGENIEURSWETENSCHAPPEN EN ARCHITECTUUR

Department of Materials, Textiles, and Chemical Engineering Laboratory for Chemical Technology

Directeur: Prof. Dr. Ir. Guy B. Marin

Laboratorium voor Chemische Technologie • Technologiepark-Zwijnaarde 914, B-9052 Gent • www.lct.ugent.be Secretariaat : T +32 (0)9 331 17 57 • F +32 (0)9 331 17 59 • [email protected]

Promotor: prof. Karen De Clerck, prof. Joris W. Thybaut

Coach: Lode Daelemans, Anton De Vylder

Aldol condensation catalyzed by electrospun aminated silica nanofibers

Aim

Assessment of the applicability of silica nanofibers functionalized with amine groups as an effective catalyst for aldol condensation reactions.

Justification

Aldol condensations are important reactions to create new carbon-carbon bonds and yield larger and more complex molecules. They are widely used in the pharmaceutical industry as well as for the preparation of fine chemicals, perfumes and synthetic flavors. However, an unsustainable homogenous base catalyst such as NaOH or Na2CO3 is used to catalyze these reactions. In a search for more sustainable chemical processes, heterogeneous alternatives are being pursued. In this regard, amine functionalized silica materials have been proven to be successful catalysts. In this work, silica nanofibers functionalized with amine groups will be synthesized and their performance evaluated for the aldol condensation reaction.

Nanofibrous webs are considered as a novel class of materials consisting out of very thin fibers with typical diameters below 500 nm. The small diameter gives these materials interesting characteristics such as a large surface area, a high porosity (> 90%) and improved mechanical properties compared to the bulk polymer. Currently, electrospinning is the most efficient technique to produce such nanofibrous webs from a polymer solution. The solution is fed through a hollow needle and subjected to an electric field of 10 – 50 kV. When a drop of polymer solution leaves the needle and enters the electric field, it gets charged. This leads to a jet of polymer solution towards the collector plate. Before the jet reaches the grounded collector screen, instabilities occur which stretch the droplets

into fibers. As a result, the solvent evaporates and a web of nanofibers is obtained on the collector. Recently, we succeeded at UGent to use this technique for a one-step production of silica nanofibers. These nanofibers combine the properties of nanofibrous webs (flexibility, porosity, large surface area) with those of bulk silica (chemical resistance, temperature stable, mechanical properties, silica surface chemistry).

Program

Based on the activity previously measured on aminated bulk silica catalysts, a synthesis procedure will be devised for aminated silica nanofibers. Critical parameters such as the total amount, and distribution, of amine groups on the surface should be taken into account, as well as possible restrictions of the electrospinning process and the batch reactor for the catalytic tests. The considered test-reaction will be the aldol condensation of 4-nitrobenzaldehyde and acetone. Information obtained from these catalytic tests will then provide feedback to the catalyst synthesis steps and lead to improvements.





Supervisor(s): Prof. dr. ir. Van Geem K.M.

Coach: Jens Dedeyne

Process intensification through reactive flow modulation

Aim

The aim of this work is to investigated the short and long term effects of implementing swirl generating turbulators in tubular reactors, designed for steam cracking. The influence of the design parameters on heat transfer and pressure drop will be examined, as well as the coking behaviour of the enhanced reactor surface.

Justification

Steam cracking of hydrocarbons is an indispensable process in chemical industry as it is the dominant method for the production of light olefins, the basic chemical building blocks. To increase the efficiency of this process, 3D turbulators are often introduced to enhance radial mixing and heat transfer. Improvement of these factors lead to lower coking rates. This is very important to ethylene producers as coke deposition on the reactor inner surface reduces heat transfer, leading to higher tube metal temperatures and higher pressure drops and hence limits the run length. On the downside, implementation of turbulators leads to a bigger pressure drop, which implies a decreased selectivity towards the desired light olefins.

Thanks to ever increasing computational power, it is made possible to study the effect of 3D geometries with Computational Fluid Dynamics (CFD). To fully investigate the influence of these turbulators, Large Eddy Simulations will be an indispensable tool for the determination of the flow field and associated properties. Validation of these results will be performed with experimentally obtained data acquired in cooperation with VKI.

Program

1. Cold flow simulations will be performed, using OpenFOAM, for a range of turbulator geometries in order select the most promising geometries.

2. LES simulations will be performed to further fine tune the design and implementation of these geometries such that overall performance of the reactor, based on pressure drop and heat transfer, is improved.

3. Non-reacting flow experiments will be performed on a cold flow setup for different coil geometries at the VKI. These experiments will provide validation for the simulation results.

4. Reactive flow simulations will be performed on the most promising design. Here focus will be on product selectivities at different stages of the run as well as on the coking behaviour and the overall run length.

Figure 1: Stereoscopic PIV setup at VKI to determine the velocity field





Supervisor(s): Prof. dr. ir. Mark Saeys

Coach: Dr. ir. Chitrakshi Goel

Reactive CFD Simulations for Oxidative Coupling of Methane in Gas-Solid Vortex Reactor in Static Geometry

Aim

The aim of this project is to perform reactive CFD simulations for the oxidative coupling of methane in a gas–solid vortex reactor in static geometry (GSVR–SG)

Justification

Oxidative coupling of methane (OCM) has been considered as a promising route for the conversion of methane to ethylene, a valuable central building block for the chemical industry. However, highly exothermic reactions and low yields of C2 products (ethane and ethylene) inhibit the use of OCM as an industrial process, even though Siluria has started to commercialize this technology using a smart combination of processes. These challenges can be partially overcome in a gas-solid vortex reactor in a static geometry (GSVR−SG), a novel reactor technology, which exhibits short gas-phase residence times and efficient heat and mass transfer.

In the GSVR−SG, fluidizing gas enters the reactor tangentially via a series of rectangular slots situated on the circumferential wall of the reactor, while the catalyst powder is introduced in the swirling flow field. (See Figure) Fluidization is achieved by a balance between the centrifugal force from the rotation and the drag force with the gas. With this novel reactor technology, the ethylene yield limit of 30% in fixed bed reactors is expected to be broken. In this project, simulations will be used to select an optimal reactor geometry and to guide the selection of reactor conditions and catalyst properties, relying on separate kinetic studies. This project is part of a European program, ADREM, to develop novel technologies for adaptable and economic methane valorization.

Program

1. Literature study on rotating fluidized bed technologies.

2. Perform CFD simulation for the oxidative coupling of methane in a vortex reactor (GSVR-SG).

3. Study the effect of operating conditions, reactor geometry and catalyst properties on the methane conversion and the ethylene yield in order to identify optimum conditions to be tested experimentally.





Supervisor(s): Prof. dr. ir. Kevin Van Geem and dr. Hans-Heinrich Carstensen

Coach: ir. Sri Bala Gorugantu

Investigation of biomass fast pyrolysis via pyrolytic degradation of model compounds

Aim

Develop a detailed understanding of lignin pyrolysis chemistry by investigating the thermal decomposition of lignin model compounds through experimentation and kinetic modeling.

Justification

In the past decade, lignocellulosic biomass has been intensively studied as a resource for alternative fuels and chemicals. One promising avenue is the thermochemical route, in which lignocellulosic biomass is subjected to fast pyrolysis, a process which results in large quantities of bio-oil next to smaller amounts of gaseous products and char. Lignocellulosic biomass consists of cellulose (30-50 wt.%), hemicellulose (15-30 wt.%), lignin (10-30 wt.%), and ash (5-10 wt.%) on a dry basis. Lignin, a heterogeneous polymer made up of phenolic molecules like syringol (S), guaiacyl (G) and p-hydroxyphenyl (P) units linked by several types of bonds, is of special interest because (a) it is not yet fully utilized in current bio-refining concepts, and (b) due to its composition it has the potential as source for interesting high-value chemicals such as vanillin, resins and adhesives.

To design and optimize a suitable process for the production of high-quality bio-oil or fine chemicals, it is important to understand the detailed chemistry of biomass fast pyrolysis. Given its complexity and inhomogeneity, experimental and theoretical studies are generally performed with model compounds, that resemble some features of real biomass.

Program

• Literature study on lignin model compounds such as dimers and trimers, experimental and modelling approaches for fast pyrolysis of lignin.

• Experimental study of the pyrolysis of lignin model compounds using the tandem micropyrolyser setup.

• Apply and extend kinetic models available in the literature to simulate the experimental data.





Supervisor(s): Prof. Dr. Ir. Mark Saeys

Coach: Ir. G.T. Kasun Kalhara Gunasooriya

Mechanistic study of Fischer-Tropsch synthesis

Aim

The mechanism of Fischer-Tropsch synthesis (FTS), the conversion of CO and H2 to a wide range of hydrocarbons and oxygenates, remains intensely debated. Insight into the mechanism will provide opportunities to control selectivity. In this project, we conduct a mechanistic study of FTS on ruthenium and rhodium catalysts using computational catalysis.

Justification

FTS of clean fuels is rapidly gaining attention as the process to convert a wide range of hydrocarbon reserves to clean fuels. It is currently being implemented on an immense industrial scale. The process starts from synthesis gas, a mixture of CO and H2, and produces products ranging from methane to light olefins, long-chain hydrocarbons and oxygenates, depending on the reaction conditions and the catalyst material. Since synthesis gas can be obtained from natural gas, biomass and even CO2 and renewable H2, Fischer-Tropsch synthesis also provides an industrial scale path to renewable liquid fuels and base chemicals. The selectivity between these fuels and various base chemicals is governed by the sequence of

C-O scission, C-C coupling and hydrogenation/dehydrogenation steps. Insight into the factors controlling this sequence will provide guidelines to design more active, stable, and selective catalysts, the ultimate goal in catalysis research. Catalyst design and kinetic modeling often start from molecular-scale hypotheses about the reaction mechanism, the structure of the active sites and the nature of the rate and selectivity determining steps. These concepts are hard to evaluate experimentally since molecules are nearly impossible to observe. Computational catalysis has therefore become a crucial tool to analyze molecular-scale concepts and elucidate their electronic origin. In combination with characterization and experimental kinetic validation, insights gained from computational catalysis can be translated all the way to the industrial scale, as we have demonstrated for several important reactions.

Program

• Literature study on FTS mechanisms on different catalysts.

• Computational catalysis for several key steps (CO scission, C-C coupling and (de)hydrogenation) on Rh and Ru catalysts and comparison with Co.

• Extend the existing Co-based microkinetic model to Rh and Ru catalysts to evaluate the effect of the catalyst choice on the product selectivity.

• Formulate guidelines to design catalysts with controllable selectivity.





Supervisor(s): Prof. dr. ir. Mark Saeys

Coach: ir. G.T. Kasun Kalhara Gunasooriya, dr. César Alejandro Urbina-Blanco

Design of a Carbon Neutral Process for the Synthesis of Methanol

Aim

To design and assess the techno-economic impact of a carbon-neutral process for the production of fuels integrating CO2 capture from air, electrochemical hydrogen production and catalytic hydrogenation of CO2.

Justification

Carbon-based fuels and materials form the basis of our high standard of living. A drastic change away from a carbon-based society is not expected. However, to avoid the dangerous build-up of CO2 in the atmosphere and the associated climate change, a transition from a society based on cheap and abundant fossil reserves to a society based on CO2-neutral activity is required. Using clean energy sources to produce fuels is a way to reduce CO2 emissions, hence helping the environment while creating new opportunities for the chemical industry.

To realize this goal, multiple steps are required, i.e., direct CO2 capture from air, electrochemical water splitting using photovoltaic electricity, and CO2 hydrogenation to methanol. Methanol is a unique platform molecule which can serve as fuel and building block of the chemical industry. Each of these individual steps in the process has reached a certain level of maturity, but the combination and integration of these processes has not yet been studied.

In this project, a process is designed for the production of methanol, integrating CO2 capture, hydrogen production, and CO2 hydrogenation to determine optimal working regime and integration. Our goal is to then perform a techno-economic analysis, establish the feasibility of this process, and understand the bottlenecks to implement this technology. In addition, alternative schemes will be considered, e.g., direct CO2 electroreduction, and integration with biomass.

Program

• Literature survey on the state-of-the-art for the individual steps: CO2 hydrogenation, direct CO2 capture and the production of solar hydrogen.

• Design an integrated process for the production of methanol using state-of-the-art technology, as well as future expected state-of-technology .

• Perform a techno-economic evaluation of the overall process to identify technolgy bottlenecks.

• Evaluate alternative technologies.





Supervisor(s): Prof. dr. ir. Kevin M. Van Geem and Prof. Geraldine Heynderickx Coach: Ir. Shekhar R. Kulkarni

Reactive CFD Simulations for biomass fast pyrolysis in Gas Solid Vortex Reactors

Aim

To perform reactive CFD simulations for biomass fast pyrolysis on the Gas Solid Vortex Reactor (GSVR) and to compare performances of various kinetics models. Justification

Biomass fast pyrolysis has become synonymous with renewable energy source over the last few

years. Fast pyrolysis can harvest energy out of biomass and produce fuel grade liquid, commonly known as bio-oil. Additionally, commercially valuable chemicals like 4-ethylguaiacol, furfural, creosol, catechol, etc. are found in the bio-oil fraction coming from fast pyrolysis, making this process more valuable and attractive. Though fast pyrolysis can result in as high as 70% bio-oil yield, it is highly dependent on vapor residence time inside the reactor, heat transfer to the solid particles and rapid cooling of the generated vapors.

Gas-solid vortex reactors (GSVR) are a new generation of multiphase reactors having a configuration of rotating beds in static geometry. Very high tangential gas injection velocities (~80-120 m/s) and momentum transfer makes the particles rotate inside the reactor in a relatively denser bed than fluidized beds. High slip velocities (5-6 m/s) as compared to the conventional reactors like gravitational fluidized bed reactors (1-2 m/s) result in very high convective heat transfer coefficients (~500-800 W/m2K) in vortex reactors. Due to the higher gas velocities, the residence time of the gas phase for these reactors is also lower than in the conventional ones. With these advantages, GSVR makes a suitable candidate to perform fast pyrolysis of lignocellulosic biomass. The latter can be studied both experimentally and numerically.

Solid volume fraction field in reactive GSVR

At LCT, we explore vortex reactors through means of CFD simulations in ANSYS FLUENT. The

experimental reactor that will provide the data to validate the simulation results is already installed and under trial. On the CFD side, both a cold flow and a hot flow, non-reactive vortex unit has been tested experimentally and numerically. In this master thesis a comparable numerical study of the reactive setup will be performed. It will allow to affirm the GSVR to be a suitable candidate for biomass fast pyrolysis. Program

1. Literature study on fast pyrolysis studies in fluidized beds and GSVRs. 2. Testing various reaction mechanisms for biomass fast pyrolysis from simple to complex and to validate

them using available experimental data. 3. Study the segregation of various solid fractions (fresh biomass, partially reacted biomass, char) which

have different densities and particle sizes during biomass pyrolysis. 4. Study the effect of particle size on biomass fast pyrolysis.





Supervisors: Prof. dr. ir. Dagmar R. D’hooge, dr. ir. Paul H.M. Van Steenberge

Coach: ir. Yoshi W. Marien

Retrieving intrinsic kinetic parameters using pulsed laser polymerization

Aim

The goal of this master thesis is the determination of individual rate coefficients (e.g. propagation and β-scission) using pulsed laser polymerization (PLP).

Justification

To optimize existing industrially applied radical polymerization processes and to develop new polymer materials kinetic modeling is indispensable. The success of kinetic modeling for these purposes depends largely on the accuracy of the intrinsic rate coefficients used. Since the estimation of these coefficients by multi-response regression to polymerization data is very demanding, the independent determination of these kinetic parameters is beneficial. Pulsed laser polymerization (PLP) is one of the most interesting polymerization methods allowing to follow “single” reactions. PLP involves a periodic series of laser pulses in which initiator radicals are formed from a photoinitiator at each pulse (Figure 1; left). A part of these radicals initiates chain growth, while the other part undergoes termination with radicals formed at a previous laser pulse. Depending on the PLP conditions applied and the monomer selected, the obtained molar mass distribution (MMD) can possess specific characteristics allowing the determination of certain intrinsic rate coefficients. For example, under well-chosen PLP conditions the consecutive inflection points of the PLP MMD (Figure 1; right) correspond to radicals which have been terminated after one, two, … pulses. From these inflection points the intrinsic propagation rate coefficient can be derived.[1] Recently, conditions have also been identified for the determination of the backbiting rate coefficient.[2] However, for important side reactions such as β-scission and macromonomer propagation no such conditions have yet been determined. In this work, a detailed kinetic Monte Carlo model for PLP is used to investigate whether certain individual reactions can be studied using specific PLP conditions.

[1] Y. W. Marien, P. H. M. Van Steenberge, C. Barner-Kowollik, M.-F. Reyniers, G. B. Marin, D. R. D’hooge, Macromolecules 2017. [2] Y. W. Marien, P. H. M. Van Steenberge, K. B. Kockler, C. Barner-Kowollik, M.-F. Reyniers, D. R. D'hooge, G. B. Marin, Polym. Chem. 2016, 7, 6521.

Program

1. Performing a literature study on the available methods for the determination of individual rate coefficients in (controlled) radical (co)polymerization and the available PLP data as a function of the monomer range, focusing in particular on PLP in aqueous media.

2. An available computer code for the kinetic modeling of PLP is used to relate specific side reactions to characteristics of the PLP MMD as a function of the PLP conditions.

3. Simulation of PLP in aqueous media. 4. Extension of the available PLP computer code to penultimate copolymerization kinetics. 5. Extension of the available PLP computer code to controlled radical polymerization.

Figure 1. Radical concentration profile (left) and molar mass distribution (right) allowing the determination of kp via its inflection points.





Supervisor(s): prof. dr. ir. Kevin M. Van Geem, prof. dr. ir. Christian Stevens

Coach: ir. Pieter Plehiers

Kinetic Analysis of Pharmaceutical Reactions: Synthesis of Diphenhydramine

Aim

The aim of this master thesis is to study the kin etics of the reactions that are relevant or related to the synthesis of Diphenhydramine. The study will be based on ab-initio calculations. The initial goal is to obtain kinetic data for these reactions. Ideally, this data will be used to obtain group-additive values (GAV’s) so kinetics for a wider range of related reactions can be predicted. Justification

Diphenhydramine is an anti-histamine that is used for the treatment of allergies, but also as sedative and pain-killer. As is the case for most pharmaceutically active molecules, a “good” synthesis is known. However, none of these known syntheses can guarantee that they are optimal. Work is being done on software to determine an “optimal” synthesis, based on automated retro-synthetic analysis. [1] Solely searching for potential synthetic pathways is not a major challenge: the reaction network generation tool Genesys is (with some minor changes) already capable of doing so. However, with increasing complexity of the synthesis, the number of possible pathways increases exponentially. Hence, the number of investigated pathways must be drastically reduced. This can be done by continuously scoring the syntheses and only continuing with the most promising ones. This score depends on many things such as reactant availability, separation, … One very important factor is the kinetics of the constituting reactions. Obviously, faster reactions will be preferred above slower ones.

The problem with pharmaceutical reactions is that very little is known/published on the kinetics, especially as detailed as desired. Best-case scenarios for pharmaceutical kinetics is the publication of yields and conversions. These can give some idea of the kinetics, but provide very little room for extrapolation and predictive use. With the development of on-the-fly generation of kinetic data in Genesys, it is possible to efficiently calculate kinetic data for several molecules at once, accelerating the generation of kinetic data. Once kinetic data is available for several different types of molecules, a regression of these data can be performed in order to determine GAV’s for several new groups.

Program

• Literature survey on existing kinetic/experimental data relevant to the synthesis of diphenhydramine

• Ab-initio calculation of the properties of reactants, intermediates and products appearing in the synthesis of diphenhydramine, taking into account the specific conditions of the reactions: liquid phase and (homogeneously) catalyzed.

• Determination of kinetic parameters for the reactions in the (known) synthetic pathways for diphenhydramine

• Regression of group additive values for the specific groups occurring in the species that are involved in the reaction of the syntheses.

1. Szymkuć, S.; et al.., Angewandte Chemie International Edition 2016, 55, (20), 5904-5937.

17176: Kinetics Simulation in Emission Control: Catalytic Oxidation of Tricholoroethene Plasma Degradation Products

Promotor(en):

• prof. Joris Thybaut

• prof. Rino Morent

Begeleider(s): • Jolien De Waele • Sharmin Sultana

Aantal studenten:

1 Richting:

Master of Science in Chemical Engineering [EMCHEM] Master of Science in de ingenieurswetenschappen: chemische technologie [EMSHEI]

Aantal masterproeven:

1 Academiejaar: 2017-2018

Probleemstelling:

Justification

Mathematical modelling of chemical and physical phenomena is an important tool in the elucidation of underlying mechanisms and can, if done properly, provide adequate guidelines for material design and process optimization. The prior knowledge of the modeler on the investigated reaction is often (too) determining for the success of simulation efforts. It is, hence, mandatory, to devise a strategy with respect to available techniques and theories which will assist rather than confuse novices in the field.

In order to maximize the information gained from modelling efforts in the most effective manner, a methodological approach will be developed. The Laboratory of Chemical Technology (LCT) is expert in the modeling of the intrinsic kinetics of large-scale chemical reactions and will team up with the Plasma Technology group from the Applied Physics department to demonstrate the versatility of the proposed methodology for the further catalytic oxidation of tricholoroethene and its degradation products after a plasma treatment.

Emissions of volatile organic compounds (VOCs) significantly contribute to air pollution and need to be abated adequately. Plasma techniques followed by conventional catalysis offer some strategic advantages in this respect, i.e., a plasma pretreatment of the VOCs to be abated allows reducing the required temperature in the post catalytic treatment.

Program

Assessment of the reactor configuration and operating conditions for the acquisition of intrinsic reaction kinetics. Measurement of an intrinsic kinetics data set in which operating conditions such as the temperature, inlet partial pressures and space time will be systematically varied. A qualitative analysis of the data set will provide guidelines for kinetic model construction and subsequent model regression. The latter will result in an enhanced insight in the oxidation reaction mechanism as well as in concrete guidelines for the selection of the most adequate catalyst.

Technologiepark and Technicum

Doelstelling:

Development and implementation of a modeling methodology for catalyst selection and design. Demonstration and validation of this methodology for the oxidation of trichloroethene and its degradation products after plasma treatment.

17401: Numerical evaluation of the experimental data resulting from hydrogen permeation measurements

Promotor(en):


• prof. Kim Verbeken

Begeleider(s):

• Ana Obradovi? • ir. Emilie Van den

Eeckhout

Aantal studenten: 1 Richting:

Master of Science in Chemical Engineering [EMCHEM] Master of Science in Sustainable Materials Engineering [EMMAEN]



Trefwoorden:

Hydrogen diffusion, Permeation, Numerical simulation

Probleemstelling:

The absorption of hydrogen by metals is a well-known problem for many electrochemical processes. Due to processes where hydrogen is involved, such as corrosion of metals, cathodic protection, fuel cell of battery, electroplating of metals, an embrittlement of the metal can occur. Hydrogen embrittlement caused by the diffusion of hydrogen in metals, and more particularly in steel, has been widely discussed. Interaction with the microstructure can lead to hydrogen trapping. The steel is embrittled when the ductility has lowered compared to its intrinsic ductility. Consequently, cracks are formed earlier than expected and unpredicted failure of the material can take place. This unexpected breakdown is due to reversibly or irreversibly trapped hydrogen at various metallurgical defects in the steel and must be avoided in all cases.

The problem is nowadays very important and very topical. Therefore, it is important to obtain a more thorough understanding of the phenomenon described above. Due to its practical importance, the study of hydrogen diffusion remains very relevant. For this purpose, an electrochemical permeation technique developed by Devanathan and Stachurski is commonly used. This technique records continuously with time the diffusive hydrogen flow, by registering small currents resulting from the hydrogen oxidation. These data provide information concerning the hydrogen diffusion and trapping behaviour in the material, but their interpretation is complex and still provides important challenges.

Doelstelling:

In this thesis you will analyse the experimental data obtained from the hydrogen permeation test in order to develop an optimal processing method. The experimental set-up and operating conditions used will be translated in a set of mathematical equations containing a well-selected set of parameters. The latter will be determined a priori via separate characterization measurements or will be determined by regression of the model to the experimental data. The assessment will start with a simple mean-field diffusion model and will gradually be extended with parallel diffusion mechanisms and/or potentially rate-limiting ad-/desorption phenomena.

17186: Polarity driven kinetics: Esterifications over ion-exchange resins

Promotor(en):


• prof. Jeriffa De Clercq

Begeleider(s): • ir. Jeroen Lauwaert • Kenneth Toch

Aantal studenten:

1 Richting:




Trefwoorden:

Kinetic modelling, experimental design, model discrimination, esterification, biodiesel, resin, catalysis

Probleemstelling:

Justification:

The esterification of carboxylic acids with an alcohol is a very old and well-known reaction for ester production. One of the first studies about the equilibrium of acetic acid and ethanol has been published in 1863. Later, esters became of great importance in various industrial products including fragrances, flavors, solvents, plasticizers, medicinal and surface-active agents. In addition, esterification reactions are used to produce millions of tons of polyesters from dicarboxylic acids and diols. In the last decades, the interest in the esterification and transesterification reactions has been rising even further because of their applications in the production of biodiesel.

In industry, (trans)esterification reactions are catalyzed by means of homogeneous acids or bases. However, in a search for more sustainable chemical processes, heterogeneous alternatives for the homogenous catalyst are being pursued. The use of heterogeneous catalysts has many advantages over homogeneous ones, such as the easy separation of the catalyst from the reaction products, an increased reusability, the ability to tune the product yields to the current market situation via shape selectivity, and the ability to combine different types of active sites.

Within the large group of heterogeneous catalysts, acidic ion exchange resins are promising materials. These resins are composed of a cross-linked polystyrene network wherein functional groups, e.g., sulfonic acids, have been grafted onto the benzene ring. When the material is dry, the polymer chains are ‘as close to each other as atomic forces allow’ and (most of) the active sites are inaccessible. Upon contact with a liquid, the material swells and the pores are opened. Note that absorption by resins typically occurs very selectively, among others depending on the polarity of the components. Additionally, the polarity has an effect on the thermodynamic non-ideality of the system. This polarity is not only affected by the solvent, but varies also strongly throughout the reaction due to concentration changes.

Program:

First, several thermodynamic models which are able to describe the selective absorption behavior of ion exchange resins will be developed. Additionally, kinetic models for homogeneous as well as heterogeneous catalyzed esterifications will be proposed. These models will be regressed against data which are already available. Subsequently, experimental design techniques will be used to identify the most ‘informative’ reaction conditions and solvent properties to be used in further experimentation in order to enhance the parameter estimations and enable model discrimination.

Doelstelling:

Elucidating the behavior of acidic ion-exchange resins in esterification reactions using experimental design, (kinetic) modelling and model discrimination techniques.

17063: Mechanistic study of ethanol oxidation on gold silver catalysts

Promotor(en):


• prof. Mark Saeys

Begeleider(s): • Jenoff De Vrieze

Aantal studenten:

1 Richting:




Probleemstelling:

Justification

Selective oxidation of alcohols to aldehydes and carboxylic acids over gold-based catalysts using molecular oxygen provides a sustainable pathway for the production of carbonylic and carboxylic compounds that otherwise use expensive oxidants and/or harmful organic solvents. Selective oxidation of ethanol to acetaldehyde, while limiting the formation of methane, CO2 and ethylene, is particularly interesting because bio-ethanol is increasingly available and acetaldehyde is one of the key intermediates in chemical industry. To improve the selectivity and activity of gold-based catalysts, different promoter elements were investigated. From these experimental studies, it was found that gold-silver catalysts are the most promising. The mechanism of ethanol oxidation on gold catalysts and the role of water and oxygen are already well established as shown in Figure 1. However, the role of silver and other promotors remains poorly understood, hampering the optimization of gold-based oxidation catalysts with high activity and selectivity. To guide the design of an optimal ethanol oxidation catalyst, a detailed insight in the effect of the silver promotors on the selectivity and activity is required.

Computational catalysis will be applied in combination with experimental and characterization data from TU Wien and ETH Zurich to elucidate the role of promoters and to study the effect of the promotor content on the catalyst performance.

Program

The following activities will be performed during the project:

• A literature review on ethanol oxidation and the gold-based catalysts for selective alcohol oxidation reactions.

• Elucidation of the role of silver as a promoter in gold oxidation catalysts by applying density functional theory and microkinetic modelling for a model AuAg(111) surface.

• Investigation of the effect of silver content on the selectivity of the ethanol oxidation process.

1. B. N. Zope, D. D. Hibbitts, et al., Science, 2010, 330, 74-78.

Doelstelling:

Investigation of the role of silver promoters in gold catalyzed alcohol oxidation reactions. Investigation of the effect of silver on the kinetics of the most relevant elementary steps and determination of the effect of the silver content on the acetaldehyde selectivity in ethanol oxidation.

17623: Shedding light on Thin Film Solar Cell Performance through fundamental modelling in SCAPS-1D and the microKinetic Engine

Promotor(en):


• prof. Johan Lauwaert

Begeleider(s):

• Kenneth Toch • Ana Obradovi? • dr. ir. Samira Khelifi

Aantal studenten:

1 Richting:




Trefwoorden:

microkinetic modeling; solar cell performance

Probleemstelling:

In thin film solar cell technology, materials with Kesterite structure are very promising, with an efficiency up to 12.6%. In the case of Si- containing S- or Se-based Kesterite, the band gap can be adjusted between 1.6-2.1 eV as confirmed by first principle calculations and optical measurements on single crystals. This will help to pave the path for this technology to become a suitable top cell candidate for tandem devices, e.g., based on already available high-efficiency crystalline silicon (c-Si) bottom cells. Within the European Project SWiNG (Development of Thin film Solar cells based on WIde band Gap kesterite absorbers) such a thin film solar cell with a transparent back contact is produced, see Figure 1, intended to be deposited on top of the state-of-the-art c-Si solar cell.

To support this development, the performance of these solar cells is modelled with an in-house developed, user-friendly software package SCAPS-1D (Solar Cell Capacitance Simulator). SCAPS-1D provides insights in the working principle of such an advanced stack of layers as a solar cell. Besides predicting the solar cell performance, SCAPS-1D can also simulate a lot of the common characterization techniques, e.g., External Quantum Efficiency, Capacitance-Profiling and Current-Voltage. As a result, it is widely used and a valuable tool in designing and understanding solar cells. Unfortunately, SCAPS-1D needs a tremendous amount of parameters to describe the physical working principle of the solar cell and, hence, it is not possible to use it in a regression software tool.

Another in-house developed software package, i.e., microKinetic Engine (µKE), is typically used in regression and modelling chemical reaction kinetics. However, during the last years, it has proven to be a versatile tool in the modelling of solar cell performance and determining the different parameter values which largely affect the solar cell performance. The software perfectly allows to exploit the duality between chemical reaction networks and electrical circuits.

Doelstelling:

This master-thesis will start from a reliable SCAPS model for a wide band gap Kesterite solar cell with transparent back contact. The numerical data for dark and light current voltage curve will be expanded with extra parasitic current pathways. This model, based on the SCAPS data with extra mechanisms, will be implemented in µKE to estimate the impact of different processing on the performance of the solar cell. Statistical regression will be used to assign this performance loss or gain to a specific mechanism.





Supervisor(s): Prof. Joris W. Thybaut

Coach: Dr. Ana Obradović, Dr. Kenneth Toch

The µ-Kinetic Engine (µKE): towards a versatile tool for complex feed conversion simulation and parametric identification

Aim

Enhancing the efficiency in the coupling between automated reaction network generation and the µ-Kinetic Engine. Guaranteeing the stability of the numerical solvers as well as the consistency of the solutions, specifically for large reaction networks. Identifying significant parameters in non-reactive systems exhibiting peculiar similarities with chemical kinetics, such as electronic circuits in solar cells.

Justification

Process design, optimization and control are relying more and more on detailed modeling. Fundamental models, which describe the occurring phenomena at the elementary step level without assuming a rate-determining step, provide an unprecedented insight into the investigated system. An in-house, user-friendly tool has been developed for such model construction, i.e., the µ-Kinetic Engine (µKE), aiming at microkinetic modeling of chemical reactions. A particular focus is on the treatment of catalytic reaction networks without requiring any programming effort of the end users.

Dedicated modeling tools are required when dealing with complex feed conversion. Complex feeds involve large reaction networks. One way to allow describing these large networks is via the integration of automated reaction network generation (ReNGeP) in the µKE. A particular feature in the case of complex feeds is that a significant number of elementary steps is quasi-equilibrated. This typically results in instabilities in numerical solvers for simulation purposes. The challenge is to identify the elementary steps that are quasi-equilibrated and dynamically adapt the corresponding set of equations to be solved.

On top of this, the µKE’s ability to identify the significant parameters of non-reactive systems, such as solar cells, will be assessed with the available experimental data.

Program

- Literature review on automation in regression as applied to chemical kinetics and beyond - Analysis of the existing software Fortran codes related to the µKE, such as ReNGeP for automated

reaction network generation - Identification and implementation of quasi-equilibrated reaction steps during regression and

dynamical adaptation of the corresponding equations in the µKE - Identification of significant parameters in selected solar cell models by regression





Supervisor(s): Prof. Dr. ir. Kevin M. Van Geem; Dr. Patrice Perreault

Coach: Dr. Patrice Perreault

Mass transfer in a vortex reactor: experimental and theoretical study

Aim

The aim of this thesis is to quantify the mass transport coefficient in a reactive gas-solid vortex reactor (GSVR) via a combined experimental and theoretical study.

Justification

Conventional fluidized beds are widely used in the chemical process industry. Among other advantages, fluidization enhances heat and mass transfer between gas and particles. However, bypassing of valuable reactants occur via the bubbles. One possible solution is to take advantage of the increased acceleration in rotating fluidized beds (high-G field), thereby increasing the onset of the bubbling regime. In the GSVR-SG developed at the LCT, the gas is injected tangentially via multiple gas inlet slots at the outer cylindrical wall. The gas serves both to impart a rotational motion to the solids and as the fluidization gas. The gas moves radially and exits via a chimney located at the center of the reactor. The GSVR-SG also allows to work with dense thin beds without gas channeling, at higher superficial gas velocities.

Up to now, the experimental studies with the GSVR-SG have mainly focused on the hydrodynamic aspect in cold flow setups (e.g. effect of the particle diameter and density, as well as gas injection velocity on the solid particles velocity profile, bed stability, and solid particles losses; radial pressure profiles). To fill the gap between the existing knowledge and that required to ease the deployment of the GSVR technology, we propose to extend the hydrodynamic characterization studies performed to characterize the mass transfer.

Program

• Literature survey on mass transfer coefficient correlations, as well as potential physical phenomenon that can be used for experimental quantification;

• Prepare and conduct an experimental plan to investigate the effect of design and operational variables on reactor-scale mass transfer coefficients;

• Experimentally determine the average mass transfer coefficients over a wide range of experimental conditions;

• Establish correlations for mass transfer coefficients in terms of the conventional dimensionless groups, and compare the results with the correlations that apply to gravitational fields (e.g. using the Chilton-Colburn J-factor analogy (the "jD factors" for mass transfer).





Supervisor(s): Dr. Hilde Poelman

Coach: Dr. Hilde Poelman

Analysing BIG data: QXAS on Ni-Fe catalysts

Aim

BIG data are increasingly encountered in research as measurements become more complex and acquisition times are reduced. In order to master these amounts of data, new analyses methods are required, allowing for swift data visualisation, automated data treatment and accessible interpretation.

Justification

Methane dry reforming (CH4 + CO2 ↔ 2CO + 2H2), with CH4:CO2=1:1, offers the attractive advantage of obtaining a H2:CO molar product ratio close to unity. For this process, Ni has been widely investigated as a reforming catalyst because of its efficiency, low cost and high availability. To counter catalyst deactivation, Fe can be a suitable promoter to Ni-based catalysts, suppressing carbon accumulation and increasing catalyst activity. In order to identify the iron phase and its role in a novel nickel-iron alloy catalyst for dry reforming, this Ni-Fe combination has been examined using Quick- X-ray absorption spectroscopy (QXAS) at both the Ni and Fe K edge. XAS allows to examine the local environment around Fe and Ni in these bimetallic catalysts, even during treatment or reaction (alloying, decomposition and dry reforming), see figure 1.

As faster measuring techniques are developed and characterization methods are often combined with each other, the result of one measurement can soon encompass several MB of data. This is for instance the case for QXAS measurements, where full XAS spectra are recorded in a matter of seconds, and correlate with simultaneous MS operation. In order to master these amounts of data, new analyses techniques are required. These can consist of data pre-treatment, adequate plotting of visual results and statistical techniques to facilitate interpretation.

Figure 1: XANES spectra of 10wt%Ni-10wt%Fe/MgAl2O4 at (a) Fe-K and (b) Ni-K

edge during H2-TPR.

Program

The tasks proposed for this thesis include:

• Literature research on Ni-Fe catalysts for methane dry reforming • Theoretical background study on (Q)XAS • Data treatment, analysis and interpretation of QXAS spectra. • Combining and interpreting results. Joining a XAS campaign at a synchrotron might be possible.

7110 7112 7114 7116 7118 7120 7122

No

rmal

ized

Abs

orp

tion

[-]

Energy (eV)

7100 7120 7140 7160 7180

No

rmal

ized

Ab

sorp

tio

n [

-]

Energy (eV)

Metallic Fe

FeO

No

rmal

ized

Ab

sorp

tio

n [

-]

(a)

7180 8320 8340 8360 8380 8400

Nor

mal

ized

Abs

orp

tion

[-]

Energy (eV)

(b)

Metallic Ni





Supervisor: Prof. dr. ir. Joris Thybaut, Prof. dr. ir. Dagmar D’hooge Coach: Dr. P. Van Steenberge

Modeling the formation of oxygenates during Fischer-Tropsch synthesis using the method of moments

Aim

The aim of this project is to extend an existing microkinetic model for Fischer-Tropsch synthesis based on the method of moments to account for the formation of oxygenates such as aldehydes, ketones and carboxylic acids.

Justification

Fischer-Tropsch synthesis (FTS) is the polymerization-like catalytic conversion of syngas (H2/CO) into a mixture of long-chain hydrocarbons, referred to in literature as syncrude. This process has been an interesting route to supply fuels to countries without access to fossil crude oil. Due to the nature of the starting material and the applied processing steps, syncrude exhibits excellent properties as it has an almost zero content of sulphur and nitrogen contaminants, in line with the current environmental restrictions for liquid fuels in the European Union and globally. The other key difference between “standard” crude oil and syncrude is the relatively high availability of alkenes (specifically n-1-alkenes) in the latter, alongside with water and oxygenates. Alkenes and oxygenates in syncrude are of great interest to the petrochemical industry, because they play an important role in downstream oligomerization reactions, acting as monomers and radical initiators respectively.

The Laboratory for Chemical Technology (LCT) at Ghent University is currently developing a microkinetic model for the Fischer-Tropsch synthesis. In order to keep the computational cost of the model within reasonable limits, the method of moments, which is a versatile methodology widely applied in polymerization kinetics, is used to reduce the size of the set of equations describing the formation of long chain components. The model reproduces CO conversion and carbon number selectivity on a Co catalyst, where exclusively alkanes and alkenes were observed. However, formation of oxygenates such as aldehydes, ketones and carboxylic acids has not yet been accounted for and is the goal of this project.

Program:

• Survey the literature on the formation of oxygenates such as aldehydes, ketones and carboxylic acids. • Select elementary reaction steps describing oxygenate formation and implement them in the existing LCT

code, accounting for the method of moments. • Simulate relevant industrial conditions using chemical process simulators such as CHEMKIN and

FORTRAN. • Validate the extended model against data reported in the literature. • Identifying the most relevant reaction steps for the oxygenate formation by performing a sensitivity analysis

and reaction path analysis. • Extending the method of moments approach to related catalytic reactions.





Supervisor: Prof. dr. Marie-Françoise Reyniers, Prof. dr. ir. Maarten Sabbe

Coach: Maarten Sabbe

Computational investigation of penultimate effects in RAFT polymerization

Aim

A computational study will be performed to investigate the influence of penultimate effects on the addition-fragmentation equilibrium step in reversible addition-fragmentation chain transfer (RAFT) polymerization, an indispensable next step in the accurate modelling of the synthesis of specialty copolymer architectures.

Justification

Controlled Radical Polymerization (CRP) techniques have shown much potential to produce well-defined polymers with a broad range of applications; including high performance coatings, adhesives, drug delivery systems, etc. Among these CRP techniques, RAFT polymerization has been put forward as a very promising CRP technique, due to its strong resemblance to free radical polymerization and its high monomer flexibility, making it a universal polymerization technique, additionally interesting due to the absence of a toxic catalyst. The principle of RAFT polymerization is presented in the figure below:

By modeling RAFT polymerization reactions starting from a first principles approach, fundamental insight is gained in the complex interplay of the stereoelectronic effects between the reacting molecules. These effects might extend well beyond the nearest neighbors and have a detrimental influence on the thermodynamic and kinetic parameters of the reaction. Correlations between the reactivity and the structural aspects of different RAFT agents and monomers will not only deepen our understanding of the reaction mechanism, but also allow us to predict the outcome of that reaction in terms of e.g., molecular weight, monomer sequence, stereo regularity… Moreover, this will aid us in rationally designing optimal reactants, reaction conditions, chain transfer agents (CTA), etc.

Program

• Literature survey on RAFT copolymerization with a focus on mechanistic aspects on currently used combinations of monomers and RAFT agent.

• Computational investigation with state-of-the-art ab initio methods on the addition-fragmentation reactions for interesting RAFT copolymerization systems.

• Kinetic modeling using the ab initio determined parameters to i) optimize the conditions in specific RAFT copolymerization reactions and ii) explore new combinations of monomers with specific RAFT agents.

Figure 1: The addition-fragmentation reaction in RAFT polymerization.

Z

SSP

m

Pn

Pm+

Z

CSS

Pm

Pn

Z

SSP

n +kadd

kaddkβ

kβ

Figure 2: Transition state ofa RAFT CTA and styrene.





Supervisors: prof. dr. ir. Kevin M. Van Geem, prof dr. ir. Geraldine Heynderickx

Coach: ir. Stijn Vangaever

High emissivity coatings in steam cracking furnaces

Aim

The aim of this thesis is to investigate the influence of coating the furnace walls on the energy efficiency of steam cracking furnaces. Based on experimental results, the wavelength dependency of the furnace wall emissivity will be taken into account when modelling the radiative heat transfer in a steam cracking furnace.

Justification

Steam cracking is one of the most important petrochemical processes in which hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing ethylene, propylene and butadiene. Steam cracking is the most energy-consuming process in the chemical industry and globally uses approximately 8 % of the sector’s total primary energy. Improving the energy efficiency has an immediate pay-back because energy costs account for approximately 70 % of production costs in typical ethane- or naphtha-based olefin plants. A more recent research topic is related to the radiant section of a steam cracking furnace, where the major part of heat transfer occurs by radiation. The radiation is emitted by the refractory walls towards the process radiant coils. Application of high emissivity coatings on the external surface of the refractory walls could improve the energy consumption in several ways. Less firing is required to reach the same process temperatures in the radiant coils and high emissivity coatings are observed to suppress the formation of reactor tube hot spots which act as a precursor for coke formation. A comprehensive study on high emissivity coatings will lead to a better understanding of the effect of high emissivity coatings on radiative heat transfer in steam cracking furnaces.

Program

• Literature survey on steam cracking furnaces in general and in more detail on the application of high emissivity coatings.

• A model will be developed, simulating the radiative heat transfer in a simplified furnace.

• The model will have to be extended in order to more accurately account for the spectral dependency of emissivity based on typical emissivity profiles found in scientific literature.

• The absorptivity of the flue gas will have to be accounted for, different grey and non-grey models will have to be compared.





Supervisor: Prof. dr.ir. Mark Saeys Coach: ir. Saashwath Swaminathan Tharakaraman

Kinetic modelling of oxidative coupling of methane

Aim Oxidative coupling of methane (OCM) is a promising route to convert methane to more valuable chemicals. The aim of thesis is to carry out experiments on OCM in a fixed bed reactor for different catalysts and to select and develop simplified kinetic models for OCM to be used in advanced reactor models.

Justification Methane is the principal constituent of natural gas, with proven reserves estimated to be around 187 trillion m3 [1]. Today only about 10% of produced natural gas produced is used as industrial feedstock by the chemical industry. Ethylene is a key building block for the chemical industry, and is today mostly produced from crude oil via energy intensive steam cracking. Oxidative coupling of methane presents an attractive alternative route to produce ethylene from methane, reducing the dependence on the crude oil. In the OCM reaction, CH4 reacts with O2 at high temperatures forming ethane, ethylene, CO, CO2 and H2O. Currently, the use of OCM is limited by low ethylene yields. In theory the yield of ethylene can be greater than 90%. The use of oxygen as an oxidant leads to over oxidation and the formation of CO and CO2, reducing yields. The OCM reaction network comprises of both homogeneous gas phase and heterogeneous catalytic reactions. Controlling the balance between these sets of reactions to enhance ethylene yields by a combination of catalyst and reactor selection is the objective of this project. In other to guide the design of such reactors and to select the optimal catalyst and reaction conditions, accurate but compact kinetic models are required, applicable over a wide range of reaction conditions. In this project, we use a state-of-the-art isothermal reactor setup to obtain isothermal kinetic data for a number of industrial catalysts, and develop kinetic models to guide reactor design and catalyst selection.

Program • Literature survey on kinetic models for OCM. • Acquisition of kinetic data in a isothermal fixed-bed reactor for different catalysts. • Develop compact kinetic models to describe the kinetic data. • Benchmarking the performance of compact kinetic models against a comprehensive microkinetic

model developed at the LCT.

1. BP, BP Statistical Review of world Energy (June 2015). 2015.


Laboratory for Chemical Technology • Technologiepark 914, B-9052 Gent • www.lct.ugent.be

Secretariat : T +32 9 331 17 57 • F +32 9 331 17 59 • [email protected]

Supervisor: Dr. Vladimir V. Galvita

Coach: Ir. Stavros-Alexandros Theofanidis

Microkinetics for methane dry reforming over Fe-Ni-(M)/MgAl2O4

Aim

The goal of this master thesis is to investigate the mechanism of methane dry reforming reaction over a Fe-

Ni-(M=Pd, Rh and Pt)/MgAl2O4 catalyst.

Justification Methane dry reforming (DRM) has been a subject of several studies. The H2/CO ratio from DRM is more favorable for Fischer-Tropsch and methanol synthesis than the ratio obtained from classical steam reforming. Moreover, DRM has the lowest operating cost among these processes and offers the additional advantage of

converting CO2 into valuable chemicals. Fe-Ni catalysts recently prepared via incipient wetness impregnation method demonstrate improved performance in DRM and motivate systematic research into the origin of their catalytic properties. It has been reported that the process of dry reforming over Fe-Ni could be described by the Mars van Krevelen mechanism where CO2 oxidizes Fe to FeOx, and CH4 is activated on Ni sites to form H2 and surface carbon. The latter was re-oxidized by lattice oxygen from FeOx producing CO. However, the detailed mechanism of methane dry reforming awaits clarification. Resolving mechanistic details of this behavior will improve our understanding of DRM reaction on supported Fe-Ni-(M) catalysts and may lead to better catalyst designs. The questions raised will be addressed by modelling the experimental data obtained from Temporal Analysis of Products (TAP) reactor. The latter is recognized as an important experimental method for heterogeneous catalytic reaction studies. A TAP pulse response experiment consists of injecting a very small amount of gas, typically nanomoles per pulse, into a tubular fixed bed reactor that is kept under vacuum. The time-dependent exit flow rate of each gas is detected by a mass spectrometer. The high time resolution of the TAP technique allows detection of short-( millisecond time scale) and/or long-lived (>1s) reaction intermediates, which helps to formulate the mechanism of reaction. Microkinetic modeling of transient phenomena enables obtaining valuable rate coefficients for the elementary steps that often cannot be determined from steady state experiments. A microkinetic model will attempt to connect the available surface physicochemical property of the catalyst, the reaction network and the experimental data.

Program

Transient experiments of methane dry reforming over Ni-, Fe-Ni and Fe-Ni-Pd catalysts supported on

MgAl2O4

Development of a detailed mechanism for methane dry reforming.

Development of microkinetic model using TAPFIT software.

Analysis of the dependency of the catalytic behavior on the catalyst descriptors providing information about the optimum catalyst composition and fraction of the active component exposed.

Department of Chemical Engineering and Technical Chemistry

Laboratory for Chemical Technology


CH4+CO2

CO2

CO

Fe FeOx CH4

H2

O

CO

NiFe

NiFeNi

Fe3O4

reduction oxidation

Ni

FeOx

Fe

Ni-Fe alloy

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3x10-6

Mo

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4th

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MASTER THESIS PROPOSAL


Supervisors: Prof. Dr. Ir. Geraldine J. Heynderickx, Dr. Maria del Mar Torregrosa Galindo

Coach: Dr. Maria del Mar Torregrosa Galindo

Experimental investigation of particle segregation in a Gas Solid Vortex Unit (GSVU) Aim The goal of this project is to investigate experimentally different aspects of particle segregation within the rotating bed of a GSVU. Different loads of polymer particles of diverse size and density will be introduced in the GSVU, and images of the particles will be acquired, processed and analyzed. Aspects such as stratification and velocity distribution within the solids bed are to be evaluated. Justification The Gas Solid Vortex Reactor is a novel chemical reactor technology, where a bed of solid particles is set into rotating motion in the cylindrical chamber of the reactor by tangentially injected gas. A cold-flow set-up is available at the LCT and studies on the gas-solid flow patterns developed in the GSVR are in progress. A Particle Image Velocimetry technique (PIV) is used for solids velocity measurements in the GSVR. The solids velocities are calculated by recording and subsequently cross-correlating successive images of the bed recorded in short, known time intervals. The capabilities of the GSVR in terms of particle segregation are still to be evaluated. The idea is to introduce loads of particles with different sizes and/or density ratios, and to evaluate through Digital Image Analysis (DIA) the effectivity of the segregation. For proper analysis of the images, a new code will be developed (using Matlab) for the DIA of the images. PIV processing software will be used to determine velocity distributions.

Program □ Literature review related to particle segregation characterization. □ Preparation of mixes of solids of different size and density ratios. □ Acquisition of series of PIV images for various solids mixtures inside the GSVR. □ Development of an image processing code for analyzing the images and stablishing the effectivity of the

segregation. □ Presentation of the results in summarizing tables and graphical illustrations, preparation of the thesis,

and of the final presentation.



v1

v2





Supervisors: Prof. dr. ir. Kevin M. Van Geem

Coach: ir. Ruben Van de Vijver

Genesys: automatic generation of kinetic models

Aim

The aim of this master thesis is to develop ab initio kinetic models for the pyrolysis of molecules derived from biomass via newly calculated group additive values.

Justification

Accurate chemical kinetic models are extremely powerful and valuable. Many significant public policy and business decisions are and have been made on the basis of predictions using detailed kinetic models. However, for most technologically important systems constructing a reliable and sizable kinetic model remains to be very difficult and time consuming. Recent advancements in chemistry and informatics have enabled a new kinetic modelling approach of tracking each molecule and intermediate throughout the reaction process using fundamental kinetics information. Several tools have been developed to automatically build large kinetic models. Such models contain typically thousands of reactions involving hundreds of intermediates with only a small fraction of the reaction rate coefficients known experimentally. Moreover, it is usually impossible to measure the concentrations of all the kinetically significant chemical species. Therefore, estimation methods are necessary to assign rate coefficients to reactions and thermodynamic properties to species. These estimation methods rely on highly accurate data for a limited set of molecules and reactions. The calculation of this accurate data has been automated in Genesys, a recently developed kinetic model generator program

The increasing global energy demand and the limited reserves of fossil fuels, alongside the environmental issues accompanying combustion of the latter, have led to an important shift to renewable resources. These resources, mainly originating from biomass, entail a wide variety of hetero-atomic species, which have a different chemical behaviour compared to hydrocarbon molecules. This behaviour is yet to be understood, and many research projects focus on the developing of kinetic models for the pyrolysis and combustion of biomass derived fuels. The lack of data and the poor predictions of many estimation methods are one of the main bottlenecks in unravelling the underlying chemistry. High level ab initio calculations are important in addressing the current data gap and can be used to improve the accuracy of common estimation methods such as group additivity.

Program

• Determining of group additive values from ab initio calculations using Genesys for reaction families where data is lacking.

• Building kinetic models for the pyrolysis of biomass derived species and validating them to experimental data.

• Assessing the importance of the newly calculated data and analyzing the kinetic models via sensitivity analyses and rate of production calculations.





Supervisor(s): Prof. dr. ir. Kevin M. Van Geem

Coach: Ir. Laurien Vandewalle

Computational Fluid Dynamic simulation of heterogeneous catalytic reactors

Aim

The purpose of this master thesis is to couple CFD simulations with detailed kinetic modelling in heterogeneous catalysis. This will allow to evaluate the performance of fixed bed reactors for the oxidative coupling of methane.

Justification

Many innovative, catalytic technologies have been developed in the past decade as a response to the world’s rapidly growing demand for a more efficient and sustainable exploitation of energy and material resources. New catalysts and improved processes are needed to guarantee the industrial competitiveness of novel technologies.

The understanding and optimizing of heterogeneous catalytic reactors requires a detailed knowledge of the heterogeneous surface reactions and the interaction of the active surface with the surrounding reactive flow. Consequently, the heterogeneous surface reactions must be analysed together with potential homogeneous gas-phase reactions, mass transport in the gas-phase, as well as heat transport between the gas-phase and solid structures. In this respect, Computational Fluid Dynamics (CFD) can offer a lot more insights than the simplified 1D reactor models that are mostly used for the description of fixed bed reactors. The CFD simulations can also be used as a validation tool for more sophisticated 1D and 2D reactor models that include for example axial and radial backmixing.

Program

• Literature survey on the operator-splitting technique and other computational tools that can be used couple computational fluid dynamics with microkinetic modelling in a more efficient way.

• Getting acquainted with the opensource CFD package OpenFOAM and the catalyticFOAM code.

• 3D CFD simulation of the oxidative coupling of methane in different fixed bed configurations and comparison with the results obtained with 1D and 2D reactor models. The 1D and 2D simulations will be performed in either Chemkin or Cantera.

Figure 1 - CFD modelling of a fixed bed reactor geometry.





Supervisor(s): Dr. ir. Paul Van Steenberge, Prof. dr. ir. Dagmar D’hooge

Coach: ir. Paul Van Steenberge

Modeling of non-isothermal controlled radical polymerization reactors

Aim

In this master thesis, an available modeling platform for the simulation of isothermal nitroxide mediated polymerization (NMP) will be extended toward the simulation of several industrial reactor types (e.g. tubular and continuous stirred tank reactor) with focus on the effect of non-isothermicity. Special attention will be given to reactor design, optimization and control of these reactor configurations.

Justification

Controlled radical polymerization (CRP), e.g. NMP (Figure 1Figure 1), has received a lot of attention during the past decades. These polymerization techniques allow the synthesis of well-tailored next-generation specialty copolymer architectures due to a better control over molecular parameters, such as chain length, functionality and topology. Numerous publications have been attributed to understanding the kinetics behind these complex polymerization systems at lab-scale under mostly isothermal conditions. However, less attention has been given to the reactor design, simulation, optimization and control of these CRPs under industrial conditions, which involve intensive heat transfer and stirrer work. The study of CRPs in reactors and their non-isothermal operation is an important requirement for CRP processes to find their way into large scale commercial products. Challenges encountered in industrial CSTRs encompass multiplicity of steady states (extinction and ignition) due to high activation energies, low reactor inlet temperatures, and possibly near-adiabatic operation. Challenges encountered in industrial batch and tubular reactors encompass hot spots (ignition) due to parametric sensitivity.

Program

1) Literature survey on CRPs on the (isothermal) lab-scale and on the (non-isothermal) industrial scale, with a focus on non-isothermicity.

2) Extending the current LCT deterministic modeling framework with an enthalpy balance and reactor equation for several reactor configurations.

3) Studying the NMP carried out in CSTRs focusing on the effect of multiplicity of steady states on the polymer properties.

4) Studying the NMP carried out in tubular reactors focusing on the effect of parametric sensitivity on the polymer properties.

5) Identifying stability and runaway criteria for CRP reactor design for the production of polymer products with a controlled microstructure.

Figure 1: Principle of nitroxide mediated polymerization (NMP).





Supervisor(s): Kevin Van Geem, Hans-Heinrich Carstensen and Ruben Van de Vijver

Coach: Florence Vermeire

Pyrolysis of cyclic and oxygenated compounds: a combined modelling and experimental study

Aim

The aim of this master thesis is to understand the chemistry of the pyrolysis of cyclic and oxygenated compounds through kinetic modelling and experimental work.

Justification

Reactive delignification of lignocellulosic biomass produces a pulp of cellulose and hemicellulose that together with lignin oil can successfully be converted into a mixture of liquid alkanes and naphthenes containing small amounts of oxygenates. Before the pyrolysis of this mixture can be modelled, the thermal decomposition of the cyclic structures and oxygenates needs to be investigated. The combined usage of experimentally acquired data and a kinetic model developed by means of automatic network generation tools allows to understand the chemistry during pyrolysis of model compounds.

Genesys is a recently developed automatic network generation code integrated with existing open-source chemo-informatics libraries. Today’s main challenge of automatic network generation is the scarcity of both thermodynamic data and reaction rate coefficients. In case databases are lacking for the considered components and reactions, data will be determined with the use of on-the-fly quantum chemistry calculations.

Program

• Literature survey regarding the experimental and modelling studies for the pyrolysis of oxygenated and cyclic compounds.

• Pyrolysis experiments of model compounds on the bench scale set-up. Data collection under a broad set of experimental conditions in diluted and undiluted atmospheres.

• Automatic generation of a detailed kinetic model for pyrolysis of these compounds by extending the currently available kinetic model with Genesys. The missing thermodynamic data and reaction rate coefficients will be determined with ab initio techniques implemented in Genesys.

• Validation of the developed microkinetic model with the use of the experimentally acquired data.





Supervisor(s) : Prof. Dr. Ir. Kevin M. Van Geem

Coach : Ir. Alexander J. Vervust

Automatic generation of microkinetic models for pol ycyclic aromatic hydrocarbon formation during pyrolysis of hydrocarb ons

Aim

The aim of this thesis is to extend the databases of the automatic network generation software Gensys to be able to generate microkinetic models which are able to describe the formation of polycyclic aromatic hydrocarbons during the pyrolysis of hydrocarbons. A microkinetic model will be generated and validated with experimental data.

Justification

Polycyclic aromatic hydrocarbons (PAHs) are a group of more than 100 chemicals that can be produced from various sources, such as the incomplete combustion of heating fuels, oil refining processes and the combustion of diesel fuels. Many PAHs are known to be carcinogenic or mutagenic and important precursors to soot, which has been linked to human morbidity and global warming.

A detailed microkinetic model, which is able to describe the chemical kinetics of PAH formation over a wide range of process conditions and feedstocks, is an invaluable tool for evaluating the performance of new and existing technologies in reducing the amount of PAHs. Because such models may contain up to thousands of reactions and species, constructing them by hand can be tedious and error-prone. The starting point of network generation is that a limited number of chemical reaction families can be used to understand and describe the gas phase reactions occurring on the molecular scale. This makes it possible to generate all possible reactions that a given chemical species can undergo in the gas phase. Apart from the reaction network, accurate values for the thermodynamic and kinetic parameters are required to allow reactor simulation. If no experimental or theoretical values for these parameters are available, estimation methods are used. It is evident that an extensive database of thermodynamic and kinetic parameters, and values for parameter estimation methods is indispensable.

Program

- Literature survey on thermodynamic and kinetic parameters of aromatic species and reactions involving aromatic species respectively for use in automatic network generation.

- Extending the Genesys database with group additive values based on the literature survey and data available from ab initio calculations.

- Perform pyrolysis experiments.

- Automatic kinetic model generation and validation with experimental data.

Figure 1 –Illustration of the formation of soot particles

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