Verdedigde doctoraten

Combined computational-experimental study on plasma and plasma catalysis for N2 fixation - Hamid Ahmadi Eshtehardi (25/04/2024)

Hamid Ahmadi Eshtehardi

Abstract

Despite the recent increasing interest in plasma technology for nitrogen fixation purposes, industrialization of this technology faces several challenges, including challenges of plasma catalysis for selective production of chemicals, the high energy cost of plasma-based nitrogen fixation compared to current industrial processes, and the design and development of scaled-up and energy-efficient plasma reactors for industrial purposes. In the framework of this thesis, we have tried to tackle these challenges and add to the state-of-the-art in plasma-based nitrogen fixation using a combination of experimental and modelling work.

• 25/04/2024
• 10.00 uur
• Locatie: Campus Drie Eiken, R.R4
• ​Online Doctoraatsverdediging
• Promotoren: Annemie Bogaerts & Marie-Paule Delplancke
• Departement Chemie

Abstract

Despite the recent increasing interest in plasma technology for nitrogen fixation purposes, industrialization of this technology faces several challenges, including challenges of plasma catalysis for selective production of chemicals, the high energy cost of plasma-based nitrogen fixation compared to current industrial processes, and the design and development of scaled-up and energy-efficient plasma reactors for industrial purposes. In the framework of this thesis, we have tried to tackle these challenges and add to the state-of-the-art in plasma-based nitrogen fixation using a combination of experimental and modelling work.

Fardokht Rezayi

• 22/02/2024
• 4 p.m.
• Venue: Campus Drie Eiken, O.01
• ​Online PhD defence​
• Incoming Joint PhD Cardiff University - Universiteit Antwerpen
• Supervisors: Sabine Van Doorslaer & Damien Murphy
• Department of Chemistry

Abstract

Cu(II) coordination chemistry is of significant importance due to copper's widespread applications, particularly in chemical catalysis. This thesis explores the molecular structure, electronic properties, and variable coordination geometry of trigonal bipyramidal complexes of Cu(II) with tripodal ligands, more specifically different tripodal tetraamines. While square planar and square pyramidal Cu(II) complexes are commonly studied, less attention is given to trigonal bipyramidal Cu(II) centres. A variety of Electron Paramagnetic Resonance (EPR) techniques is used as a unique analytical tool to probe Cu(II) complex chemistry.

While the counter ions had only a negligible effect on coordination through outer sphere interactions, the effect of the type of tetraamine, pH and their concentration was significant, revealing subtle and strong variations in the coordination chemistry upon change of these conditions and thus emphasizing the importance of understanding the solution-based structures when aiming for specific applications.

The performance of different trigonal bipyramidal Cu(II)-tetraamine complexes for the selective oxidation of glycerol was further explored. The interest in glycerol oxidation is growing, since glycerol is a valuable bio-renewable compound formed during biomass conversion. Through a combination of different techniques, the catalytic behaviour could be fit to the faith of the Cu(II) complex during reaction. Attempts were made to heterogenise the Cu(II) complexes into Y zeolites in order to allow easy removal of the catalyst from the reaction mixture after glycerol oxidation. Though the correlation between Cu(II)-complex encapsulation, Si:Al ratio, and proton count in the zeolitic structure was identified, the heterogeneous material proved unsuitable for glycerol oxidation. Nevertheless, it holds promise for exploring alternative catalytic reactions.

Tong Zhang

• 26/01/2024
• 3 p.m.
• Venue: Campus Groenenborger, V.008
• Supervisors: Shoubhik Das & Bert Maes
• Department of Chemistry

Abstract

Due to the climate change, pollutions, energy shortage and other interrelated global crises, there is always an increasing demand for the development of environmentally friendly processes in the chemical industries. In the last two decades, the field of photochemistry has emerged as a potent methodology across diverse domains, enabling the synthesis of numerous intricate compounds through environmentally sustainable means. This thesis elucidates four distinct methodologies concerning the generation of valuable products across diverse domains through the utilization of photoredox and photochemical reactions. The thesis is divided into five chapters:

• Chapter 1: An overview and introductory exposition of the fundamental principles and concepts pertaining to photochemistry are provided.

• Chapter 2: We have enhanced the generation of hydrogen peroxide by introducing an aryl amino group in polymeric carbon nitrides via visible light-mediated photocatalysis. In addition to increasing the efficiency of photocatalytic system, the description of the whole reactive scenario for the polymeric carbon nitrides has been depicted by combining diverse characteristic methods and theoretical calculations. Futhermore, the possible active catalytic sites are identified with the aid of 15N and 19F solid state NMR without using any expensive labeling reagent.

• Chapter 3: We have developed a unique methodology for the generation of α-amino radicals under the irradiation of visible light under a metal-free condition. This strategy is induced by π–π stacking and ion-pairing interactions and facilitated the synthesis of functionalized amines through three-component coupling reactions.

• Chapter 4: We have designed an efficient method for the red light-mediated sulfonyltrifluoromethylation of olefins which provide remarkable regioselectivity. This reaction system has been thoughtfully designed, and excellent substrate compatibility and functional group tolerance exhibits the industrial potential, thus validating the significance of this strategy.

• Chapter 5: We have developed a metal-free photocatalytic system for the transformation of biomass into formic acid. Compared to previous strategies, our method can work efficiently at room temperature and atmospheric pressure. Notably, real biomass and even daily-life-based-materials such as waste papers and oak cork stoppers of wine bottles are also smoothly converted to formic acid.