Continuous Hydrothermal Synthesis of Nanomaterials: From Laboratory to Pilot Plant

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Summary: A novel laboratory scale continuous hydrothermal flow synthesis (CHFS) system has been developed for the controlled synthesis of inorganic nano-materials (particles <100nm) with potential commercial applications from sunscreens and battery materials to fuel cell components and photocatalysts. The CHFS system has many advantages; it is a green technology (using supercritical water as the reagent), which utilises inexpensive precursors (metal nitrate salts) and can controllably produce high quality, technologically important functional nano-materials in an efficient single step (or fewer steps than conventionally). This project seeks to move the existing laboratory scale CHFS system (developed over the past few years at QMUL) towards a x10 pilot scale-up (nano-powder production of up to 500g per 12h depending on variables). The proposed research will initially compare the ability to control particle characteristics of the CHFS system at the laboratory scale over a large range of process variables (flow rates, temperatures, pressures, etc), building full operational envelopes that will describe reactor variables versus particle properties for each material. In particular, we will utilise on-line measurement of dynamic laser light scattering particle sizing, and at-line analytical methods. This data will help develop univariate and multivariate understanding of the temporal operational spaces and interactions between process variables and product quality. On-line sensing and chemometrics incorporated with combined computational fluid dynamics modelling of hydrodynamics/mixing and population balance modelling of particle size evolution via nano-precipitation will be used to study alternative nozzles designs and other potential bottleneck factors. This will lead to a generic strategy for scaling up and controlled manufacture of nanomaterials with consistent, reproducible and predictable quality. The scale up quantities of nano-powders from the pilot plant will allow industrial partners to perform prototyping or comprehensive commercial evaluation of nano-powders in a range of applications which they have hitherto not been able to conduct due to lack of sufficient high quality material. Importantly, the know-how acquired on the project and the proposed feasibility studies will reduce the risk and commercial barriers for industry that might consider building a larger industrial scale CHFS plant in the future.