The Design of Efficient Bifunctional Catalysts for the Successful Application of Tandem Catalysis in One-Pot Processes

Abstract

The general concept behind bifunctional heterogeneous catalysis is that on the surface of the catalytic material there are two distinct types of active sites that work cooperatively, or in tandem, to perform a surface-catalyzed reaction or several consecutive reactions. The most general classification of bifunctional catalysts can be based on the fact that: (1) the two sites participate in the same chemical step (simultaneous interaction), for example through interaction of different parts of an adsorbed reactant molecule with the catalyst as in a concerted reaction or (2) the active sites take part in different types of elementary steps as part of an overall reaction path (successive interaction). These bifunctional catalysts are employed worldwide for the production of many valuable products, since fine chemicals to biofuels thank to the successful design of the catalyst surface.This work particularly explains the steps involved in the design and evaluation of a bifunctional catalyst to be used in the production of a valuable product starting from a convenient raw material involving different consecutive catalytic reactions. Moreover, the benefits of performing these consecutive chemical steps in a one-pot process based on tandem catalysis are also explained, providing also a relatively simple guide for categorize these processes. Then, the most widely employed approaches for the design and evaluation of bifunctional catalysts are thoroughly explained, comparing these strategies and analyzing their advantages and disadvantages. Finally, the example of the production of pentyl valerate (a biofuel compatible with diesel) from biomass-derived gamma-valerolactone is presented, where these diverse approaches have been applied for the design of efficient bifunctional catalytic materials.