Modulation of metal nanocatalysts for enhanced selectivity of chemoselective reduction and addition hydrogenation

Abstract

Selective hydrogenation plays an important role in modern industry. It is an important way to produce bulk and fine chemical products and intermediates. Among them, selective reduction hydrogenation and selective addition hydrogenation are two important types. Metal catalysts are the first to be applied to selective hydrogenation. They have a long history, a wide variety, high activity, and a wide range of applications. They are a class of efficient and practical catalysts. However, since the nature of the metal, hydrogen activation, and the properties of the groups that can be hydrogenated are complicated the interaction between each group that can be hydrogenated and the activated hydrogen is diverse. Consequently, one-component metal catalysts usually offer a low selectivity of the target product. Therefore, it needs to modulate the metal with modifiers and thus the selectivity can be enhanced. Over the years, many achievements have been made in metal-catalyzed selective hydrogenation and many modulation methods have been developed. This paper focuses on selective reduction hydrogenation and selective addition hydrogenation catalyzed by metal nanocatalysts. By summarizing the rules, we gain insight into the essential mechanisms by which various modulation methods have improved selectivity. By doing so, we hope to provide a reference for future research. It hopes that the catalysts will be designed more accurately in the future and catalysts with high selectivity, high activity, and high stability will be obtained. In this paper, the modulation methods are divided into three categories: the electronic effect, the geometric effect, and the steric effect. The electronic effect is that modifiers modify the electronic and catalytic properties of the catalyst. According to the degree and scope of the effect of promoters, the electronic effect can be divided into modifiers modulating the electronic properties of metals, modifiers absorbing the aim group to be hydrogenated, and modifiers participating in the hydrogenation reactions. The steric effect is that the steric hindrance is created by modifiers. In terms of the geometric effect, the geometry of the metal catalyst is adjusted and thus the catalytic performance is adjusted through geometric factors. It includes the size effect, the morphology effect, and intermetallics. Finally, the modulation methods are commented and the future prospect is proposed.