Microwaves in the Catalytic Valorisation of Biomass Derivatives

The application of microwave irradiation in the transformation of biomass has been receiving particular interest in recent years due to the use of polar media in such processes and it is now well-known that for biomass conversion, and particularly for lignocellulose hydrolysis, microwave irradiation can dramatically increase reaction rates with no negative consequences on product selectivity. However, it is only in the last ten years that the utilisation of microwaves has been coupled with catalysis aiming towards valorising biomass components or their derivatives via a range of reactions where high selectivity is required in addition to enhanced conversions. The reduced reaction times and superior yields are particularly attractive as they might facilitate the transition towards flow reactors and intensified production. As a consequence, several reports now describe the catalytic transformation of biomass derivatives via hydrogenation, oxidation, dehydration, esterification and transesterification using microwaves. Clearly, this technology has a huge potential for biomass conversion towards chemicals and fuels and will be an important tool within the biorefinery toolkit. The aim of this chapter is to give the reader an overview of the exciting scientific work carried out to date where microwave reactors and catalysis are combined in the transformation of biomass and its derivatives to higher value molecules and products.

Hydroxylation of Benzene via C-H Activation Using Bimetallic CuAg@g-C3N4

Bimetallic CuAg@g-C₃N₄ catalyst system has been designed and synthesized by impregnating copper and silver nanoparticles over the graphitic carbon nitride surface. Its application has been demonstrated in the hydroxylation of benzene under visible light.

Microwave-assisted FLP-catalyzed hydrogenations

Microwave-irradiation accelerates FLP-catalyzed hydrogenations.

Nanocatalysis in Flow

Nanocatalysis in flow is catalysis by metallic nanoparticles (NPs; 1-50 nm) performed in microstructured reactors. These catalytic processes make use of the enhanced catalytic activity and selectivity of NPs and fulfill the requirements of green chemistry. Anchoring catalytically active metal NPs within a microfluidic reactor enhances the reagent/catalyst interaction, while avoiding diffusion limitations experienced in classical approaches. Different strategies for supporting NPs are reviewed herein, namely, packed-bed reactors, monolithic flow-through reactors, wall catalysts, and a selection of novel approaches (NPs embedded on nanotubes, nanowires, catalytic membranes, and magnetic NPs). Through a number of catalytic reactions, such as hydrogenations, oxidations, and cross-coupling reactions, the advantages and possible drawbacks of each approach are illustrated.

Heterogeneous catalysis for the direct synthesis of chemicals by borrowing hydrogen methodology

This review summarizes the recent examples of hydrogen transfer-type reactions using supported transition metal catalysts with special emphasis on the one-pot synthesis of chemicals by borrowing hydrogen methodology.

Synthesis of a yolk/shell Fe3O4@poly(ionic liquid)s-derived nitrogen doped graphitic porous carbon materials and its application as support for nickel catalysts

The synthesis of yolk/shell spheres including a movable magnetic core, a poly(ionic liquid)s-derived porous carbon shell, and nickel nanoparticles confined within the porous shell is reported.

A ruthenium-grafted triazine functionalized mesoporous polymer: a highly efficient and multifunctional catalyst for transfer hydrogenation and the Suzuki–Miyaura cross-coupling reactions

A new ruthenium grafted mesoporous organic polymer has been synthesized and it showed excellent catalytic activity in transfer hydrogenation and C–C cross-coupling reactions.