Homogeneous Catalysis for Sustainable Energy: Hydrogen and Methanol Economies, Fuels from Biomass, and Related Topics

Abstract

As the world pledges to significantly cut carbon emissions, the demand for sustainable and clean energy has now become more important than ever. This includes both production and storage of energy carriers, a majority of which involve catalytic reactions. This article reviews recent developments of homogeneous catalysts in emerging applications of sustainable energy. The most important focus has been on hydrogen storage as several efficient homogeneous catalysts have been reported recently for (de)hydrogenative transformations promising to the hydrogen economy. Another direction that has been extensively covered in this review is that of the methanol economy. Homogeneous catalysts investigated for the production of methanol from CO 2 , CO, and HCOOH have been discussed in detail. Moreover, catalytic processes for the production of conventional fuels (higher alkanes such as diesel, wax) from biomass or lower alkanes have also been discussed. A section has also been dedicated to the production of ethylene glycol from CO and H 2 using homogeneous catalysts. Well-defined transition metal complexes, in particular, pincer complexes, have been discussed in more detail due to their high activity and well-studied mechanisms.

Ammonia Borane, NH3BH3: A Threshold Photoelectron–Photoion Coincidence Study of a Potential Hydrogen‐Storage Material

“…Various methods have been developed that range from liquification, via adsorption onto metals or (metal) organic‐frameworks, [1] to chemical conversion that stores hydrogen by incorporating it into a different compound. Although the accessibility of H 2 is better with liquification or adsorption techniques, [2] the highest (volumetric) density is achieved by chemically converting it into hydrogen carrier molecules like ammonia, [3] methanol, [4] or ammonia borane (AB) [5] . In particular, AB has attracted attention, and its potential in different applications has been described in several reviews [6]…”

Recent developments on the transformation of CO2utilising ligand cooperation and related strategies

“…A substantial paradigm shift in approach towards green, sustainable and renewable technologies is required. [3][4][5] Currently, CO 2 is used on a large scale for the synthesis of urea, salicylic acid and polycarbonates by the chemical industry. In addition, CO 2 is utilised in oil recovery, the beverage industry, low temperature storage applications and for fire extinguishers.…”

A Review on CO2‐Based Polyureas and Polyurea Hybrids

“… [3] MeOH can be obtained via the direct hydrogenation of CO 2. [57] The optimized reaction conditions in a closed system with ruthenium‐Macho catalyst are: 130 °C, 24 h, molar ratio MeOH/amine of 4, 2 mol% KO t Bu, THF or toluene as the solvent. KO t Bu could facilitate the dehydrogenation of MeOH by promoting the C−H cleavage or by scavenging impurities.…”