The Catalytic Reduction of Carboxylic Acid Derivatives and CO₂ by Metal Nanoparticles on Lewis‐Acidic Supports

Abstract

The development of heterogeneous catalysts for green chemical synthesis is currently a growing area in catalysis and sustainable chemistry. Especially the use of renewable carbon resources such as carbon dioxide (CO2) and biomass‐derived compounds (e. g. carboxylic acids, esters, and amides) represent highly attractive research targets. As these substances reside in a high oxidation state, efficient reduction processes are required in order to convert these substrates into useful and value‐added chemicals. Moreover, in the interest of mass production, these substrates should be reduced by molecular H2 and a heterogeneous catalyst. In this context, our group has developed advanced catalysts and established design guidelines for catalysts that promote the reductive transformations of carboxylic acid derivatives and CO2. Our studies show that cooperative catalysis between Lewis‐acidic sites on the catalyst support and supported metal nanoparticles are crucial for the success of these challenging hydrogenations. In this review, we summarize the results of our recent studies on the direct synthesis of value‐added chemicals from CO2 and carboxylic acid derivatives using supported transition‐metal catalysts, and we propose a design concept for heterogeneous catalysts that promote these processes.

Mechanistic study of the selective hydrogenation of carboxylic acid derivatives over supported rhenium catalysts

“…Hydrogenation reactions of carboxylic acids, esters, and amides are receiving increased attention because of their use in a variety of applications in the pharmaceutical and fine-chemical industry, as well as for upgrading bio-based chemical feedstocks. [1][2][3][4][5] Although significant progress has been made in recent years, the development of catalysts that promote these processes remains a formidable task. The difficulties are predominantly a consequence of the fact that carboxylic acid derivatives are kinetically unreactive and thermodynamically stable as a result of the low electrophilicity of the carbonyl carbons.…”

Selective Hydrogenation of Methyl Palmitate to Cetyl Alcohol via Ternary Synergistic Catalysis of Ni, Oxygen Vacancies, and Lewis Acid Sites under Mild Reaction Conditions

“…Various metal oxides, namely, VO x , WO x , GaO x , ReO x , SnO x , and NbO x , were screened as Ni/TiO 2 modifiers to obtain efficient catalysts for the hydrogenation of methyl palmitate to cetyl alcohol. According to prior studies, − the combination of group 5–7 metals with group 8–10 metals is beneficial to promoting the selective hydrogenation process owing to their unique synergistic effect in the hydrogenation reactions. Therefore, here, we focused on group 5–7 metal oxides as additives.…”

CO2 reduction into formic acid under hydrothermal conditions: A mini review

“…Considering that biomass stores solar energy and contains various reductive groups such as hydroxyl, aldehyde, amino, it can be used as an ideal reductant to reduce CO 2 theoretically 58‐60 . We found that a large amount of hydrogen is generated from both glycerol gasification and water splitting during hydrothermal glycerol conversion to lactic acid 48,49 .…”

“…Considering that biomass stores solar energy and contains various reductive groups such as hydroxyl, aldehyde, amino, it can be used as an ideal reductant to reduce CO 2 theoretically. [58][59][60] We found that a large amount of hydrogen is generated from both glycerol gasification and water splitting during hydrothermal glycerol conversion to lactic acid. 48,49 These results further indicate that biomass is reductive under hydrothermal conditions, and the hydrogen could be produced from both biomass and water decomposition for efficient in situ hydrothermal reduction of CO 2 .…”