MultiphasIc Nanoreactors for Heterogeneous Catalysis via smart Engineering of Tailored Dispersions – MICHELANGELO

Gas-liquid-solid (G/L/S) multiphasic reactors are extensively used in the chemical industry for both depollution and synthesis. Three typical examples of G/L/S reactions are the catalytic hydrodesulfurization of naphtha, the catalytic oxidation of liquid hydrocarbons with either air or oxygen, and the catalytic wet air oxidation of pollutants for water remediation. Conventional G/L/S reactors comprise packed beds (e.g., trickle beds, bubble columns), stirred tank and bubble column slurry reactors and fluidized beds. These technologies usually suffer from resilient mass/heat transfer limitations due to their low G/L and L/S specific interface areas, especially when dealing with fast reactions such as hydrogenations. In practice, co-solvents, surfactants and G/L phase-transfer catalysts (e.g., molten salts) can be employed to promote the G/L contact and distribute the catalyst between the phases, affecting unavoidably the economy and eco-efficiency of the process. Alternatively, continuous flow microreactors and catalytic membrane contactors have been considered for increasing the G/L interface area. Nonetheless, these systems require complex equipment and still do not guarantee an efficient L/S contact at the catalyst surface – for a major improvement on current systems in terms of cost efficiency and energy savings, G/L/S reactors operating at the nanoscale are required.

The key challenge of this project is to devise a global solution to the low G/L/S contact in multiphasic reactors via a refined engineering of the G/L/S interface at the nanoscale. To this aim, we propose the design of robust particle-stabilized G/L dispersions (i.e. micro/nanobubbles and liquid marbles) as highly efficient G/L/S nanoreactors for conducting catalytic reactions at mild conditions. To meet this aim, 5 objectives will need to be fulfilled:

1. Preparation of NPs with defined sizes, shapes, hydrophilic-lipophilic balance (HLB) and including catalytic functions;

2. Generation of particle-stabilized foams, bubbles and liquid marbles affording highly active and selective reactions at the G/L/S interface and NP recycling after each catalytic cycle.

3. Imaging of reaction/diffusion profiles and NP adsorption/desorption dynamics at the G/L inter-face using external stimuli when necessary (hyperthermia, light, radiofrequency, ultrasound);

4. Rationalization of the interplay between the NP assembly at the G/L interface and the catalytic properties along the reaction by marrying simulations with well-designed experiments; and

5. Reengineering of G/L/S multiphasic reactors using particle-stabilized nanoreactors to achieve a high catalytic performance at milder operation conditions compared to conventional reactors while keeping a high degree of stability and flexibility at reduced layouts.

These unprecedented systems will be used as a platform for reengineering established multiphasic reactors (slurry tanks, bubble columns, spray columns). Unlike conventional reactors, G/L/S nanoreactors are expected to offer enhanced catalytic properties via a refined engineering of the triphasic contact at the nanoscale. Moreover, such reactors will benefit from unique nanoscopic properties of confined G/L interfaces, conditioning the reactivity and the local G/L repartition near the catalytic sites.

This project will deliver a novel and innovative strategy for enhancing mass/ heat transfer in G/L/S reactors, affording high efficiency at milder and safer conditions. This will make G/L/S nanoreactors attractive for a broad range of industrial reactions. Through innovation on both amphiphilic catalysts and process intensification, MICHELANGELO is expected to result in a radical step change towards a higher efficiency and competitiveness in the process industry.