Turning glycerol into gold: a new process makes biodiesel more profitable
An electrooxidation process efficiently converts glycerol, a byproduct of biodiesel production, into high-value three-carbon compounds
Tokyo Institute of Technology
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The developed glycerol electrocatalysis enables the valorization of glycerol towards primary or secondary alcohols.
view moreCredit: Tokyo Institute of Technology
Biodiesel, a green alternative to conventional diesel, has been shown to reduce carbon dioxide emissions by up to 74%. Biodiesel is produced through transesterification, converting triglycerides into biodiesel and producing glycerol as a low-value byproduct. Since glycerol makes up about 10% of the output, efforts have focused on boosting its value. One method involves electrochemical oxidation, turning glycerol into high-value three-carbon compounds like dihydroxyacetone (DHA) and glyceraldehyde (GLYD), though past approaches often yielded unstable or low-value products under strong alkaline conditions.
In a study published in the Journal of Catalysis on 15 August 2024 researchers led by Associate Professor Tomohiro Hayashi from Tokyo Institute of Technology (Tokyo Tech) and Professor Chia-Ying Chiang from National Taiwan University of Science and Technology, Taiwan, have developed a highly selective and efficient glycerol electrooxidation (GEOR) process that can lead to the production of valuable 3-carbon (3C) products.
“Establishing an electrochemical route for a highly selective and efficient glycerol electrooxidation process to desirable 3C products is essential for biodiesel production,” says Hayashi and Chiang.
Selective oxidation of glycerol is challenging due to its structure. Glycerol has three –OH groups: two on primary carbon atoms and one on a secondary carbon atom. This arrangement creates steric hindrance, making it hard for reactants to target specific –OH groups for oxidation. In alkaline conditions, the –OH groups also cause unwanted side reactions that break carbon-carbon bonds, resulting in two-carbon or one-carbon compounds instead of the desired three-carbon products.
To address this, the researchers conducted GEOR using sodium borate and bicarbonate buffer as a mild alkaline electrolyte and a nickel-oxide (NiOx) catalyst. The sodium borate helps protect certain –OH group, improving the selectivity of the reaction, while the NiOx catalyst enhances the efficiency of the electrooxidation process. Sodium borate forms coordination complexes with glycerol’s primary and secondary alcohol groups to form GLYD and DHA respectively. However, the final product depends on the ratio of borate to glycerol. To understand how different concentrations of glycerol and borate affect the electrooxidation process, a fixed concentration of 0.1 M borate buffer was reacted with varying concentrations of glycerol (0.01, 1, 2.0 M) and a fixed concentration of 0.1 M glycerol with varying concentrations of borate buffer (0.01, 0.05, 0.10, and 0.15 M). while maintaining a pH of 9.2.
Higher borate concentrations were found to increase the selectivity for 3C products, particularly DHA, with the highest selectivity of up to 80% observed at a borate concentration of 0.15 M. This improvement is attributed to the increased buffer capacity provided by the borate solution, which helps maintain a stable pH during the reaction and stabilizes the borate-glycerol complex for further oxidation into 3C compounds. Conversely, increasing the glycerol concentration reduced both the yield and selectivity of 3C products. At a glycerol concentration of 1 M, GLYD was the main product, with a selectivity of 51%.
The difference in the type of 3C product was found to be related to the formation of different glycerol-borate complexes. Using Raman spectroscopy, the researchers found higher borate concentrations favor six-membered ring complexes, promoting secondary –OH oxidation and DHA production. Conversely, higher glycerol concentrations favor five-membered ring complexes, leading to primary –OH oxidation and GLYD formation.
"Five-membered ring complexes were more likely to form in the electrolyte with a borate-to-glycerol ratio of 0.1, whereas six-membered ring complexes became more prominent in the electrolyte with a borate-to-glycerol ratio of 1.5," says Hayashi and Chiang.
These findings present a promising strategy for transforming glycerol into valuable products, boosting the sustainability and profitability of biodiesel production.
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About Tokyo Institute of Technology
Tokyo Tech stands at the forefront of research and higher education as the leading university for science and technology in Japan. Tokyo Tech researchers excel in fields ranging from materials science to biology, computer science, and physics. Founded in 1881, Tokyo Tech hosts over 10,000 undergraduate and graduate students per year, who develop into scientific leaders and some of the most sought-after engineers in industry. Embodying the Japanese philosophy of “monotsukuri,” meaning “technical ingenuity and innovation,” the Tokyo Tech community strives to contribute to society through high-impact research.
https://www.titech.ac.jp/english/
Institute of Science Tokyo (Science Tokyo) will be established on October 1, 2024, following the merger between Tokyo Medical and Dental University (TMDU) and Tokyo Institute of Technology (Tokyo Tech), with the mission of “Advancing science and human wellbeing to create value for and with society.”
Journal
Journal of Catalysis
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Tuning selectivity toward three-carbon product of glycerol electrooxidation in borate buffer through manipulating borate/glycerol molar ratio
Novel green chemistry: A safe, low-cost, and eco-friendly conversion process for the synthesis of sulfonyl fluorides, a world first!
A research group including researchers from Osaka University has developed a method to safely and cost-effectively convert thiols and disulfides, which are easily accessible raw materials, into sulfonyl fluorides
Osaka University
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A new, safe and low-cost synthetic reaction process for sulfonyl fluorides
view moreCredit: Shinobu Takizawa
Osaka, Japan – For the first time in the world, thiols and disulfides were converted into sulfonyl fluorides using SHC5® and KF, expanding "click chemistry" with high efficiency and low environmental impact. This green process, yielding only NaCl and KCl as byproducts, is expected to become the preferred method in chemical and industrial synthesis.
The concept of "click chemistry” is known for its high chemical selectivity, high yield, and rapid connection of molecules. Since its inception, click chemistry has demonstrated broad utility across various fields, including synthesis, materials science, chemical biology, and pharmaceutical development, garnering immense popularity.
However, sulfonyl fluoride is a key compound in the sulfur-fluorine exchange (SuFEx) click reaction, which links molecules together, and its synthesis initially required the use of SO2F2 gas or KHF2, both of which are highly toxic and difficult to handle. To achieve the safe and environmentally-friendly synthesis of sulfonyl fluoride, synthetic chemists have explored various chemical reaction processes.
In this study, it was developed for the first time in the world that sulfonyl fluoride can be efficiently synthesized by reacting the easily-handled and highly-reactive SHC5® and KF (potassium fluoride) with thiols or disulfides. This is a green synthetic process that produces only non-toxic sodium and potassium salts as by-products, resulting in minimal environmental impact.
This chemical reaction enabled the environmentally-friendly and tailor-made synthesis of a broad scope of sulfonyl fluorides containing aromatic, aliphatic, and heterocyclic groups.
The synthetic protocol is very simple, enabling the low-cost, scalable, and safe production of sulfonyl fluorides. This new method is expected to become the first choice for sulfonyl fluoride synthesis in both the chemical and industrial sectors.
"Developing new organic synthetic protocols to create useful compounds, such as pharmaceuticals, is a highly important research theme, particularly from the perspective of the Sustainable Development Goals (SDGs)," says corresponding authors of the study Masayuki Kirihara, Shinobu Takizawa, and Mohamed S. H. Salem. "Furthermore, developing reaction processes that consider the environmental impact of by-products is becoming increasingly important. We will continue to disseminate research from Japan that focuses on the green synthesis of useful compounds with ripple effects across various fields."
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The article, “Green and Efficient Protocols for the Synthesis of Sulfonyl Fluorides Using Potassium Fluoride as the Sole Fluorine Source,” was published in ACS Sustainable Chemistry & Engineering at DOI: https://doi.org/10.1021/acssuschemeng.4c03951
About Osaka University
Osaka University was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, Osaka University is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Website: https://resou.osaka-u.ac.jp/en
About Shizuoka Institute of Science & Technology
Shizuoka Institute of Science and Technology (SIST) was established on April 4, 1991 in Fukuroi city, Shizuoka prefecture in Japan. The university has an enrolment of approximately 1500 students in two faculties: the Faculty of Science and Technology and the Faculty of Informatics.
Website: https://www.sist.ac.jp/en.html
Journal
ACS Sustainable Chemistry & Engineering
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Green and Efficient Protocols for the Synthesis of Sulfonyl Fluorides Using Potassium Fluoride as the Sole Fluorine Source
An image expressing the value of the study: Liquid representing water resources with an organic synthesis reaction in a flask, emphasizing environmental sustainability.
Credit
Reprinted with permission from ACS Sustainable Chem. Eng. 2024, 12, 32, 12135–12142. Copyright 2024 American Chemical Society.
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