It has been well-received in the catalysis community that the understanding of reaction mechanism and kinetics can benefit the catalytic production of chemicals and fuels by reducing waste and achieving high atomic efficiency. For example, anhydrofructofuranose, one of the key intermediates during acid-catalyzed dehydration of fructose to produce 5-hydroxymethylfurfural, was identified recently. This intermediate equilibrates with the desired and undesired products, preventing the reaction from reaching a quantitative yield. However, it is extremely challenging to understand complex reaction networks, which involve the interplay of reactants, intermediates, and the desired and by-products. Exploring reaction networks is complicated because it involves identifying reaction species, deconvoluting individual reaction paths, and understanding the reversibility and rates of interconversions. On top of the complex reaction mixture, another big challenge is that some intermediates are extremely unstable and cannot be quantified by traditional sampling techniques. To address these challenges, we employ<i> operando</i> magic angle spinning NMR spectroscopy (MAS-NMR) and construct the reaction network of a multistep reaction. With the profound understanding of the reaction network, we are able to direct the reaction to produce either one of the two possible products selectively. This work demonstrates the benefit of understanding complicated reaction networks to catalysis in terms of on-demand tuning the final reaction products.

Elucidation of reaction network for a tandem reaction to achieve selectivity control

ACS Spring 2022

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