Magnetic nanoparticulate catalysts in flow processes

Abstract

Homogeneous catalysts are highly efficient but their separation and recovery from the products can be problematic. Conversely, heterogeneous systems can suffer from lower catalytic activities, generally due to limited mass transport of reactants to the solid surface of the catalyst. The separation of (nano)catalyst is a difficult chemical process and the heavy metals contamination in the product is undesirable and must be limited to ppm. Approach to overcome these drawbacks is described in this work. Iron oxide magnetic nanoparticles were evaluated as a support for different catalysts as an example of semi-homogenous catalytic systems and these were described in the first part of this work. A range of catalysts supported onto magnetic nanoparticles was utilized in different catalytic reactions, including: hydrogenation, oxidation, epoxidation. A variety of coatings, including alumina, carbon, and silica were used in order to establish the way of protecting nanoparticles from aggregation. Silica was chosen to be the best protecting material. The second part of this thesis covers the investigations carried out to design and construct a capillary reactor with magnetically entrapped and manipulated nanoparticle catalysts for continuous hydrogenation and Suzuki C-C coupling reaction. For both reactions, high conversion was achieved, and no noticeable loss of catalyst was observed. Other potentially highly valuable new technology for performing chemical synthesis was described in this thesis, which includes hydrogenation of nitrobenzene, dimethyl itaconate and tandem Knoevenagel condensation - hydrogenation process in a microreactor, with a thin layer of nanocatalysts entrapped and moved by the external magnetic field. The possibility of trapping and moving nanocatalyst without any separation devices inside the reactor opens new avenues in the area of catalytic flow chemistry. The preparation of multi-modal imaging agents using magnetic nanoparticles was also studied. Silica coated magnetic nanoparticles were modified with quantum dots, showing possibility of preparation of fluorescent probe. MNPs were also radiolabeled using copper-64, which suggest potential of this material as multimodal imaging agent. Initial in vitro experiments suggested that the nanoparticles have potential to enter cells and to act as MRI/PET imaging agents.

Date of Award	1 Sept 2011
Original language	English
Awarding Institution	University of Bath
Supervisor	Pawel Plucinski (Supervisor) & Alexei Lapkin (Supervisor)