When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
Energy demands are continuously rising, and currently, society remains dependent on fossil fuels as the primary energy source. The overconsumption of fossil fuels offers many drawbacks, such as greenhouse gas emissions. Therefore, the search for more sustainable and renewable energy, such as biodiesel, has garnered significant interest. Commercially, biodiesel is produced using a homogeneous strong base catalyst (e.g. NaOH) through the transesterification of vegetable oils. While efficient, this process presents several limitations, such as the inability to recover and reuse the catalyst and costly purification.
Carbon-based nanomaterials have already been reported as efficient heterogeneous catalysts for biodiesel production. However, despite their promising results, these materials usually require high temperature and pressure to drive the reaction, increasing the energy requirements and making large-scale use unfeasible. Carbon dots (CDs) and polymeric carbon nitride-based structures (PCNs) have emerged as promising candidates to overcome these limitations. CDs and PCNs are well-known for their low-cost synthesis and interesting optical properties, yet their role in driving chemically-catalyzed reactions remains relatively unexplored.
Herein, we present the synthesis, characterization, and investigation of amine-passivated CDs and PCNs as heterogeneous catalysts for the transesterification of canola oil to biodiesel. The transesterification reaction parameters were optimized, achieving >96% biodiesel conversion for all systems. In addition, the catalysts were reused for at least five reaction cycles and demonstrated the system's ability to maintain high catalyst performance over several reaction cycles. Lastly, we investigate the effects of modifying the catalyst's surface groups and morphology and postulate a plausible governing mechanism for the transesterification of canola oil to biodiesel.