We develop challenging catalytic reactions for establishing a sustainable society. Our study covers from fundamental science to the application in society. The specific research topics are as follows:

Biomass Conversion

Biomass is the organic, non-fossil material produced by the growth of living things. Biomass can be converted to chemicals essential in our life. After exhausting them as CO₂ after using, photosynthesis regenerates biomass using that CO₂. Therefore, we can achieve a sustainable carbon cycle by utilizing biomass properly.

Utilization of Woody Biomass

Wood and grass are the most abundant biomass, and their annual production amount is assumed to be 200 billion tons. This amount corresponds to an energy larger than that consumed by human beings. So, woody biomass is a fascinating resource, if we can utilize it without affecting nature.

Woody biomass mainly consists of cellulose, hemicellulose, and lignin. They are polymeric compounds that we need to convert into useful small molecules in biomass utilization. Cellulose and lignin are, however, very recalcitrant, and thus their chemical conversion is a challenge.¹⁾

Cellulose is a polymer of glucose, similar to starch. Starch smoothly undergoes depolymerization, whereas cellulose does not.²⁾ The selective conversion of cellulose needs an outstanding catalyst, which we wish to develop.

Meanwhile, lignin is an aromatic polymer that may be a source for producing many aromatic molecules.³⁾ We aim to open this pathway by creating new catalysts that transform the skeleton of lignin into useful structures.

Conversion of Marine Biomass to Organonitrogen Compounds

Shells of crustaceans such as crabs and shrimps contain a large amount of chitin. Nature likely produces 100 billion tons of chitin annually.

We emphasize the structural characteristic of chitin. The structure is similar to that of cellulose, but it consists of N-acetylglucosamine, denoted NAG, units. NAG has acetamido groups instead of hydroxy groups at position 2. Therefore, chitin is a source of organic compounds with naturally-fixed nitrogen.

A recent report indicates that the artificial utilization of nitrogen exceeds the capacity of the Earth in terms of planetary boundaries.⁴⁾ The chemical utilization of chitin may contribute to a nitrogen cycle as a new value of biorefinery.⁵⁾

Chitin is resistant to degradation, but we can selectively depolymerize chitin in a mechanochemical reaction using catalysts and mechanical forces of milling.^6,7) We aim to improve the reaction efficiency and to develop new catalytic reactions to convert NAG to useful organonitrogen compounds.

Chemical Recycling of Waste Plastics

Most of the plastics used are landfilled or dumped into the environment.⁸⁾ A major cause is the high cost of recovery and the low value of plastics as a heat source.

A portion of the wasted plastics go into oceans and degrade into microplastics.⁹⁾ Most plastics remain for a long time, thus accumulating in the environment. Living things take in the microplastics, which might cause various problems.

We relieve this issue by converting waste plastics to value-added chemicals. Many people have reported chemical recycling of plastics, but in most cases, common plastics such as polyethylene and polypropylene produce a mixture of many products in their degradation reactions.¹⁰⁾ Instead, we will produce particular compounds with a high selectivity to maximize the value.

Our process will gain the value of waste plastics, which may decrease the dumping of plastics, leading to a lower environmental load. In addition to developing functional plastics that degrade into harmless compounds in the environment, the selective conversion of plastics should be an important topic.

Research Methodology

We study both heterogeneous and homogeneous catalysis but specialize in the former. We create new catalytic reactions and catalysts and clarify the reaction mechanisms. The mechanistic studies employ physicochemical characterization such as spectroscopy and kinetics predominantly. We also perform quantum calculations of molecular systems by ourselves. Combining various methods unveils the catalytic reactions, a complex system.

References

• W. Deng et al., Catalytic conversion of lignocellulosic biomass into chemicals and fuels, Green Energy Environ., 8, 10-114 (2023).
• A. Shrotri, H. Kobayashi, A. Fukuoka, Cellulose Depolymerization over Heterogeneous Catalysts, Acc. Chem. Res., 51, 761-768 (2018).
• Y. Jing, L. Dong, Y. Guo, X. Liu, Y. Wang, Chemicals from Lignin: A Review of Catalytic Conversion Involving Hydrogen, ChemSusChem, 13, 4181-4198 (2020).
• J. Rockström, M. Klum, P. Miller and J. Lokrantz, Big World Small Planet: Abundance Within Planetary Boundaries, Yale University Press (2015).
• H. Kobayashi, T. Sagawa, A. Fukuoka, Catalytic conversion of chitin as a nitrogen-containing biomass, Chem. Commun., 59, 6301-6313 (2023).
• H. Kobayashi, Y. Suzuki, T. Sagawa, M. Saito, A. Fukuoka, Selective Synthesis of Oligosaccharides by Mechanochemical Hydrolysis of Chitin over a Carbon-Based Catalyst, Angew. Chem. Int. Ed., 62, e202214229 (2023).
• H. Kobayashi, A. Fukuoka, Mechanochemical Hydrolysis of Polysaccharide Biomass: Scope and Mechanistic Insights, ChemPlusChem, e202300554, in press.
• R. Geyer, J. R. Jambeck, K. L. Law, Production, use, and fate of all plastics ever made, Sci. Adv., 3, e170078 (2017).
• A. L. Andrady, Microplastics in the marine environment, Mar. Pollut. Bull., 62, 1596-1605 (2011).
• A. Musa, E. A. Jaseer, S. Barman, N. Garcia, Review on Catalytic Depolymerization of Polyolefin Waste by Hydrogenolysis: State-of-the-Art and Outlook, Energy Fuels, 38, 1676-1691 (2024).