Synthesis of nanomaterials for applications in heterogeneous catalysis
Loading...
Files
Full Text E-thesis
Date
2022-12-20
Authors
Casey, Éadaoin
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
The purpose of this thesis was to synthesise nanomaterials with a variety of chemical and physical properties to find the optimum design of heterogeneous catalysts for a variety of applications in heterogeneous catalysis. The aim for chapter 3 was to synthesise support free Pd NPs which are stabilised by a range of small organic ligands and polymers for the application in the pharmaceutical synthesis. It was vital to identify the correct capping ligand to stabilise the NP to find the optimal catalyst for the reductive amination reaction. A range of material characterisation methods were used to evaluate the impact of ligands and the role of steric and electronic effects on the selectivity behaviour of the Pd NPs when they were stabilised by different capping ligands which helped identify the best catalytic system. PVP stabilised Pd NPs was found to be the best performing catalyst displaying the best overall yield of the desired product. XPS and FTIR revealed that the presence of PVP ligands at the NP surface gives rise to combination of steric and electronic effects and it was shown that electron donation from the PVP carbonyl group to the Pd NP occurred.
Chapter 4 focused on plasmonic photocatalysis which allows harvesting of visible light as an abundant and renewable energy source to drive a myriad of chemical reactions. The novelty of this work is that it combines a two- dimensional (2D) metal catalyst and plasmonic photocatalysis which has not been reported in literature. The high proportion of exposed surface atoms and large surface area of ultrathin 2D nanosheets results in high atom efficiency. Light-harvesting catalysts allow lower reaction temperatures and enhanced reaction rates, enabling more energy efficient and greener routes to chemical synthesis. The chapter developed a new synthesis method for 2D alloyed PdAu nanosheets using long chain surfactants to template the growth. Tuning the surface chemistry was critical to controlling the two-dimensional growth and maintaining high catalytic activity. The catalysts display outstanding activity for visible-light driven room-temperature Suzuki cross coupling reactions, greatly outperforming commercial Pd catalysts.
The need for the development of efficient catalysts for the chemical recycling of PET to tackle the global issue of plastic waste was the motivation of Chapter 5. Designing the optimum heterogenous catalyst was the main aim of this work with particular focus on immobilisation of metal ion and nanoparticle based catalysts. Surface modification of a catalyst support with organic linkers is a suitable strategy to immobilise transition metal ions onto a SiO2 support material. The nature of the organic ligand being connected to the ion influences the steric and electronic effects which influences the catalytic behaviour. The NP catalysts were found to be superior than the ion immobilsed catalysts in the degradation of PET to its monomer BHET, due to synergistic effects between the NP and the organic ligand.
The aim for chapter 6 was to find the optimum metal free heterogeneous catalyst anchored on SiO2 support. This work was inspired by the findings in chapter 5. Three guanidine catalyst with a range of nitrogen environments were synthesised as potential metal free catalysts for the degradation of PET and PLA. The catalysts were evaluated under conventional, and microwave assisted heating methods to find the best method for converting these plastics to their monomers with high yields. The catalysts were evaluated using material characterisation methods such as XPS, TEM and FTIR. It was discovered that the best performing catalyst had the most nitrogen environments eluding that the nitrogen availability was an important feature for the catalyst activity for both PET and PLA degradation. Microwave assisted heating methods outperformed the conventional heating methods yielding high conversions with less energy and time being required.
Description
Keywords
Nanomaterials , Catalysts , Sustainable chemistry , Photocatalysis , Heterogeneous catalysis
Citation
Casey, É. 2022. Synthesis of nanomaterials for applications in heterogeneous catalysis. PhD Thesis, University College Cork.