Catalytic function and its efficiency play a significant role in industrial reactions, and consistent reforms are made in the methodology to enhance the large-scale synthesis of drugs, polymers, and other desired products. Available catalysts can be homogeneous, which means that they possess the same phase as the reactants and products, making them difficult to separate from the reaction mixture. On the other hand, heterogeneous catalysts are a preferred choice for such reactions because of their ease of separation and reusability.
The past decade has seen the emergence of porous heterogeneous catalysts, which not just leave scope for reusability but also increase the density of catalytic sites. To further increase the efficiency of porous heterogeneous catalysts by multifold, Ritesh Haldar's group at TIFR Hyderabad came up with a new methodology.
They integrated a porous heterogeneous thin film in a cross-flow microfluidic setup. What a thin film ensures is that the catalyst remains immobilized on a solid substrate. In this setup, the inlet allows for the reactants to interact with the catalytic thin films and push the product back through the outlet. If one cycle results in 25% conversion of reactants to products, the setup will facilitate multiple of such cycles for increased conversion and, thus, increased efficiency of the reaction. A control over the diffusion rates of the reactants is achieved, making the process much faster than the already existing standards.
The group has also developed a novel approach to evaluate the effectiveness of a cross-flow microfluidic system combined with a porous heterogeneous catalyst thin film. In their study, they conducted a base-catalyzed Knoevenagel condensation reaction, achieving a remarkable turnover frequency (TOF) of over 4000 h⁻¹. TOF measures how efficiently the catalyst produces a product relative to the amount of catalyst used over time. The observed increase in TOF is attributed to enhanced reactant diffusion rates and the effective immobilization of the catalyst. This study also sheds light on the relationship between turnover frequency and diffusion rates of the reactant into pores.
The invention, however, is limited to catalyst thin films and liquid-phase organic reactions at the moment. Looking forward, the research team plans to expand their work to include gas-phase reactions and large-scale chemical reactions using their innovative cross-flow microfluidic technology. This next phase will broaden the scope of their findings and open new avenues for organic reaction applications.
Content written by: Suvendu Panda, Srushti Chipde
