A new device uses microwave flow reactions to convert biomass into useful sugars

A simple diagram of the chemical processes within the device developed by the research team. In their system, a solution of the disaccharide cellobiose (left) is passed through a sulfonated carbon catalyst (center), an acid catalyst that helps break down the sugar. This catalyst is then heated using microwaves to increase catalytic activity. This efficiently converts cellobiose to glucose (right). Provided by: Kyushu University/Tsubaki Laboratory
Researchers at Kyushu University have developed a device that combines a catalyst and microwave flow reaction to efficiently convert complex polysaccharides into simple monosaccharides. The device utilizes a continuous flow hydrolysis process in which cellobiose, a disaccharide made from two glucose molecules, is passed through a sulfonated carbon catalyst that is heated using microwaves. A subsequent chemical reaction breaks down cellobiose into glucose. Their results are published in the journal ACS Sustainable Chemistry & Engineering.
Converting biomass into useful resources has been a topic of scientific research for decades. Biomass polysaccharides, long-chain complex sugars that are ubiquitous in nature, can be converted into monosaccharides that can be used in food, medicine, and chemicals, and are therefore considered to be one of the most promising materials for efficient conversion. . Synthesis.
Hydrolysis is one of the more efficient chemical reactions that convert long-chain sugars into monosaccharides, usually using acids as catalysts. Although most acid catalysts are in gas or liquid form, solid acid catalysts (as the term suggests, they are solid acids) are known to be easier to recycle and have attracted the attention of researchers. .
However, solid acid catalysts require high temperatures to react efficiently. To overcome this, Associate Professor Shuntaro Tsubaki and his colleagues at Kyushu University’s Faculty of Agriculture studied applying microwave flow reactions to heat solid catalysts during the reaction process.
“Microwaves create a localized high-temperature reaction field on a solid catalyst, making it possible to increase catalytic activity while keeping the entire reaction system at a low temperature,” Tsubaki explains. “Furthermore, the substrate can be continuously flowed into the reaction vessel where microwaves are applied to the catalyst, resulting in higher yields of the desired product.”


Photo of microwave flow reactor with Pyrex glass tube and Efield. Credit: ACS Sustainable Chemistry and Engineering (2024). DOI: 10.1021/acssuschemeng.4c07690
The device the researchers developed used a solid acid catalyst made of sulfonated carbon. Cellobiose, a disaccharide, was used as a model sugar substrate to test the system. In their device, a solution of cellobiose is passed through a sulfonated carbon catalyst that is heated to up to 100-140°C using microwaves. The catalyst then breaks down cellobiose by hydrolysis, producing the monosaccharide glucose.
One of the keys to system efficiency is the ability to separate the microwave electric and magnetic fields.
“Microwaves produce both electric and magnetic fields. Electric fields heat bipolar substances such as water, which heats food. Magnetic fields, on the other hand, induce heating of conductive substances such as metals and carbon. ” Tsubaki.
“In our device, we were able to increase the catalytic activity by separating the two fields and using the electric field to heat the cellobiose solution and the magnetic field to simultaneously heat the catalyst.”
Microwave-accelerated catalytic reactions have applications in a variety of chemical reactions, including organic synthesis, plastic recycling, and biomass conversion. The research team hopes that as renewable energy sources continue to proliferate, electrically powered chemical production like theirs will help propel the industry towards a greener future.
“We hope that our system will help develop more sustainable chemical syntheses. We also hope that our system will help in the development of more sustainable chemical synthesis. “We would like to explore the usefulness of this methodology,” concludes Tsubaki. .
Further information: Shuntaro Tsubaki et al. Efficient cellobiose hydrolysis over sulfonated carbon catalysts in spatially separated microwave electric and magnetic flow reactors, ACS Sustainable Chemistry & Engineering (2024). DOI: 10.1021/acssuschemeng.4c07690
Provided by Kyushu University
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