Research Results

World's First Successful Direct Synthesis of Plastics from Atmospheric Carbon Dioxide

This research presentation was introduced in the following media.

• July 28, 2021 Japan Metal Daily, Nikkan Sangyo Shimbun, TeleTou BIZ
• July 29, 2021 The Nikkan Kogyo Shimbun
• July 30, 2021 ＠DIME
• August 4, 2021 The Chemical Daily
• September 7, 2021 Nikkei Business Daily
• September 25, 2021 Monthly Scientific Journals "Newton" November issue
• November 23, 2021 The Mainichi Newspapers

Summary

 Associate Professor Masazumi Tamura (Center for Artificial Photosynthesis, Osaka City University), Professor Keiichi Tomishige (Department of Applied Chemistry, Graduate School of Engineering, Tohoku University), and Kenji Nakao (Section Chief, Advanced Technology Research Laboratory of Japan Steel Corporation) succeeded in developing the world's first catalytic process for the direct synthesis of aliphatic polycarbonate diols from atmospheric carbon dioxide and diols^*1 without the use of dehydrating agents, and announced in the journal "Green Chemistry" that aliphatic polycarbonate diols can be synthesized with high yields and high selectivity by combining cerium oxide catalysts.

 Polycarbonate diols are important intermediates in the synthesis of polyurethanes, such as plastics, and are currently synthesized using phosgene^*2 and carbon monoxide as raw materials, but since these raw materials are toxic, there is a need to develop technologies to replace them from the perspective of green chemistry^*3. The method of synthesizing polycarbonate diols by using carbon dioxide as an alternative raw material and reacting with diols has attracted attention as a green reaction system that uses only water as a by-product, but it was necessary to use high-pressure carbon dioxide and dehydrating agents to obtain high yields. The method found in this study overcomes these problems, and by blowing carbon dioxide at normal pressure into the diol using a cerium oxide catalyst, it is possible to remove the generated water from the reaction system, and we have succeeded in obtaining the desired polycarbonate diol with a high selectivity and high yield.

 The results of this research were published online in Green Chemistry (IF=10.18) on Monday, July 26, 2021.

研究者からのコメント

Reducing carbon dioxide is a global issue, and chemical fixation of carbon dioxide is considered to be one of the effective methods. In this research, we have succeeded in developing a new solid catalytic process that can directly convert atmospheric carbon dioxide into polymers. In the presence of a cerium oxide catalyst, carbon dioxide reacts with diols to obtain polycarbonate diols, which are useful as chemicals and raw materials for chemicals without the use of dehydrating agents. In the future, we will brush up the catalyst and process for practical use.

1. Background

 Climate change and natural disasters caused by global warming are becoming more prominent, and there is a global demand to reduce carbon dioxide, which is one of the major greenhouse gases (Paris Agreement, reduction targets and action plans). The method of converting carbon dioxide into a useful chemical product by considering it as a C1 chemical raw material^*4 has been attracting attention in recent years, and is expected to contribute to carbon dioxide fixation. However, carbon dioxide is a very stable molecule, and a high-performance catalysts and its process design are key to its activation. As a carbon dioxide conversion technology, there is a non-reducing method that converts the oxidation number of carbon atoms of carbon dioxide without changing it, and if alcohol and diol can react well with carbon dioxide, it will be possible to synthesize organic carbonates^*5 and aliphatic polycarbonates, which are useful chemicals. These carbonate compounds are synthesized primarily using toxic chemical feedstocks such as phosgene and carbon monoxide, and there is a strong need to develop technologies to replace these processes. For the long-term fixation of carbon dioxide, the method of converting it to polymers is considered to be advantageous. However, the synthesis of polycarbonate from carbon dioxide and diol has the problem that the reaction hardly proceeds as it is, and the target polycarbonate can hardly be obtained unless the by-product water is removed (<1%). As an example of direct polymerization from carbon dioxide and diols, a catalytic reaction system using nitrile as an organic dehydrating agent and cerium oxide as a catalyst has been reported, but it requires high-pressure carbon dioxide and the recovery and regeneration of dehydrants is an issue. In addition, a catalytic process that does not use a dehydrating agent has been desired because of the reaction between nitrile, which is a dehydrating agent, and the raw material diol and the resulting product, and the resulting contamination of by-products.

2. Research Topics

 In the synthesis of polycarbonate diols from carbon dioxide and diols, water is a by-product, and water removal is essential to improve yields. As a water removal method that does not use a dehydrating agent, we focused on the difference in boiling point between the product and diol and water, and predicted that the desired carbonate synthesis would proceed by blowing carbon dioxide at normal pressure and evaporating and removing the water. As a result, it was clarified that cerium oxide catalysts alone showed high activity among various metal oxide catalysts, and we succeeded in developing a very simple catalytic reaction system that does not use a dehydrating agent and does not require high-pressure carbon dioxide.

3. Expected effects

 This technology provides a new catalytic process that can chemically convert carbon dioxide at normal pressure without the use of additives. In addition, this technology is considered to be applicable to substrates with a boiling point sufficiently higher than the boiling point of water, and it can also be applied to the synthesis of organic carbonate, carbamate^*6, urea, etc., which are useful as additives for lithium-ion batteries and as raw materials for polymer synthesis. By establishing various chemical synthesis routes from carbon dioxide, it is expected to become a catalytic process that contributes to the chemical fixation of carbon dioxide.

4. Future Developments

 We plan to further research and development while studying processes including improvement and scale-up of solid catalysts for practical use.

5. Research Projects

 The results of this research were obtained through the implementation of the NEDO Leading Research Program/Mitoh Challenge 2050, a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

 Osaka City University and Tohoku University have been conducting research and development on solid catalysts for carbon dioxide conversion, and have found that cerium-based metal oxide catalysts are effective in activating carbon dioxide. In this project, we developed a solid catalyst system that can synthesize polymers from carbon dioxide without using dehydrating agents, which require recovery and reuse, with the aim of reacting carbon dioxide at normal pressure emitted from blast furnaces and other facilities as raw materials.

 In March of this year, Japan Steel Corporation announced its "Japan Steel Carbon Neutral Vision 2050 ~ Challenge to Zero Carbon Steel" as a unique initiative to address climate change issues, and has positioned the realization of carbon neutrality by 2050 as the most important management issue. The results of this research demonstrate that it is possible to separate and capture carbon dioxide emitted from steel mills and convert them into useful substances such as low-energy functional chemicals, and we believe that it is significant that it can contribute to carbon dioxide fixation and carbon dioxide reduction.

Terminology

*1: Diol

A general term for compounds in which two hydroxyl groups (OH groups) are attached to two different carbons

*2: Phosgene

Also known as carbonyl chloride. Because it is highly reactive, it is used as a variety of raw materials, but it is also very toxic, and it is severely irritating to the eyes and suffocating toxicity to the human body.

*3: Green Chemistry

A general term for concepts that seek to reduce the burden on the human body and the environment in the design, synthesis, application, and disposal of chemical and other compounds, as well as technologies for this purpose.

*4: C1 chemical raw materials

Raw materials for chemical products such as carbon dioxide, carbon monoxide, and methane that contain one carbon atom.

*5: Carbonate

A compound having a -O-CO-O- structure is generally referred to as a carbonate compound or a carbonate ester.

*6: Carbamate

＞A general term for carbamic acid ester compounds with the structure of N-CO-O-. It is also called carbamate.

Publication Information

All Press Release (PDF:1069KB)

Article source: Osaka City University website