Investigating and exploiting surface cooperativity in multifunctional solid catalysts for carbohydrates reactions

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Multifunctional heterogeneous catalysts, particularly acid and base catalysts, play a key role in the development of sustainable routes for the production of valuable chemicals from non-edible carbohydrate-enriched biomass, which is considered a promising alternative to the diminishing fossil resources. However, the characteristics of carbohydrates and the complexity of their reactions create challenges to the development of efficient catalysts. The exploitation of cooperation between different surface components of multifunctional materials, similar to that encountered in enzymes, is a suitable strategy for preparing improved heterogeneous catalysts. Nevertheless, detailed studies on the role of different surface components of solid catalysts in the reactions of carbohydrates, which could lead to the identification and subsequent exploitation of cooperations, are scarce. The work proposed in this project is the study of surface cooperativity on the activity and selectivity of multifunctional catalysts on the conversion of glucose into 5-hydroxymethylfurfural (HMF). HMF is an important intermediate in the synthesis of polymers, fine chemicals, fuels, etc., and can be produced by dehydration of glucose with very low yields, or through the isomerization of glucose to fructose in tandem with the dehydration of fructose to HMF. The latter transformation is difficult to accomplish and requires a multifunctional solid comprising Brønsted acid sites (dehydration) together with Lewis acid or Brønsted basic sites (isomerization). The proposed work comprises three main tasks. Task 1 is the preparation of multifunctional catalysts consisting of metal oxides and metal oxides functionalized with organic groups. The solids will contain components with potential for promoting the catalytic reactions investigated here and/or potential for cooperative catalysis, such as tin, titanium and tungsten oxides, and sulfonic acid, carboxylic acid, hydroxyl, thiol and amine functionalities. Task 2 is the chemical and physical characterization of the multifunctional solids, with special focus on the surface properties, by using a wide variety of techniques, and will include detailed FT-IR and UV-vis-NIR studies. Task 3 is the evaluation of the catalytic performance of the prepared catalysts on the isomerization reaction of glucose to fructose, dehydration of fructose into HMF or tandem isomerization-dehydration transformation. Materials will be synthesized and modified for specific catalytic experiments aimed at assessing the role of each surface component of the solids and for the identification of catalytic cooperativity. The ultimate objective of the work is the development efficient catalysts for the reactions investigated here, and for other transformations involving carbohydrates.