CO₂ Reduction to Methanol in the Liquid Phase: A Review

Abstract

Excessive carbon dioxide (CO2) emissions have been subject to extensive attention globally, since an enhanced greenhouse effect (global warming) owing to a high CO2 concentration in the atmosphere could lead to severe climate change. The use of solar energy and other renewable energy to produce low‐cost hydrogen, which is used to reduce CO2 to produce bulk chemicals such as methanol, is a sustainable strategy for reducing carbon dioxide emissions and carbon resources. CO2 conversion into methanol is exothermic, so that low temperature and high pressure are favorable for methanol formation. CO2 is usually captured and recovered in the liquid phase. Herein, the emerging technologies for the hydrogenation of CO2 to methanol in the condensed phase are reviewed. The development of homogeneous and heterogeneous catalysts for this important hydrogenation reaction is summarized. Finally, mechanistic insight on CO2’s conversion into methanol over different catalysts is discussed by taking the available reaction pathways into account.

First Phenol Carboxylation with CO2 on Carbon Nanostructured C@Fe-Al2O3 Hybrids in Aqueous Media under Mild Conditions

“…In this sense, the hybrids wettability properties showed, as their structural formulation, that they could be necessary in order to observe phenol conversion, as can be evidenced by the fact that no reaction was observed under the same reaction conditions with γ-alumina spheres or FeAl spheres. Although values were far from full conversion, it is in the same range of those reported in the most common reaction, converting CO 2 to methanol in heterogeneous catalysis [ 52 , 53 ]. The porous distribution of the samples allowed for the phenol and CO 2 spread in the hybrids to the active sites by diffusion, while the aqueous solution was maintained outside the spheres due to their hydrophobicity properties created by the nanofibers and nanowhiskers-like growth, resulting in a biphasic media.…”

Hydrogenation of CO2 or CO2 Derivatives to Methanol under Molecular Catalysis: A Review

“…Practical methods of CO 2 hydrogenation to methanol were usually based on heterogeneous catalysis, and these reactions were traditionally carried out at high temperatures (200-300 • C) [16][17][18][19][20]. Studies showing homogeneous catalytic CO 2 hydrogenation under relatively mild conditions (<150 • C) are of great significance, and considerable efforts have been made in the last decade to achieve this [21][22][23][24][25][26][27][28].…”

“…Among the homogeneous catalytic reactions of CO 2 hydrogenation to methanol, the major catalytic systems are transition-metal catalysts [21][22][23][24][25][26][27][28][29], frustrated Lewis-pairs (FLPs) [30][31][32][33] or N-heterocyclic carbenes (NHC) [34][35][36], and reductants such as H 2 [22,29], silanes [34,35], or boranes [37,38] are often employed. As a result of its atom efficiency and low cost, molecular hydrogen is used in CO 2 hydrogenation more often.…”

Methanol Assimilation with CO2 Reduction in Butyribacterium methylotrophicum and Development of Genetic Toolkits for Its Engineering

“…The process for converting CH 4 or CO 2 to the liquid C1 compound methanol (MeOH) is easy and cheap. 5,6 The decreasing price of methanol has caused it to become one of the most attractive fermentation substrates for producing value-added metabolites. 7−9 Nevertheless, taking advantage of methanol has challenged industrial microbiologists, and there are active ongoing research efforts to develop methylotrophic strains for the efficient conversion of methanol into fuels and chemicals.…”