Periodic Reporting for period 1 - LiquidWallCat (Embedding catalysts in liquid wall flow devices)
Berichtszeitraum: 2023-05-01 bis 2025-04-30
Continuous flow processes for manufacturing fine chemicals, such as active pharmaceutical ingredients and agrochemicals, offer advantages over batch processes due to higher surface-to-volume ratios and precise reaction control, leading to higher yields and less waste; however, their large-scale use is limited by challenges in handling solids, which often clog small flow tubing. Recent work by the Hermans group and the startup Qfluidics introduced quadrupolar magnetic fields to trap ferrofluids—magnetic nanoparticle suspensions—along flow channel walls, creating deformable liquid tubes that prevent clogging and enable reactions with solids. To expand this technology, particularly by incorporating catalysis without introducing solid surfaces that risk clogging, the liquidwallcat project aimed to attach catalytic moieties directly to magnetic nanoparticles, focusing on creating a stable, catalytically active ferrofluid by using smaller nanoparticles and combining surfactants with catalysts for functionalization.
Initial attempts to coat iron oxide nanoparticles (IONPs) from coprecipitation with a monolayer of APTES showed inconsistent surface coverage despite IR confirmation of silica formation, prompting a switch to thermal decomposition of iron oleate for more uniform, \~7 nm spherical IONPs. After stripping the oleate layer with nitrosonium tetrafluoroborate and stabilizing the particles with citrate, a seeded sol-gel method was used to coat them with silica under basic conditions using TEOS, followed by quenching with an imidazole-containing silane to provide aqueous solubility and functionalization potential. Despite testing various reaction conditions, some particles consistently fused together rather than forming discrete core–shell structures, though stable ferrofluids were ultimately obtained at low pH, with magnetic fields successfully manipulating the entire liquid phase—an important step toward catalytic ferrofluid development, even though further functionalization and catalytic testing were not completed.
In this project, I designed and synthesized novel core-shell magnetic nanoparticles forming an aqueous ferrofluid that remains well-dispersed and can be displaced as a whole under a magnetic field. While catalyst functionalization was not achieved, the acidic imidazolium ferrofluid could already enable acid-catalyzed reactions in liquid tubes, and the imidazole groups provide anchoring sites for future functionalization with catalysts or other functionalities, such as for separation or decontamination applications.