CHEMICAL SCIENCE

The electrojoule pulsed space-time heating method realizes the efficient and continuous conversion of plastics to monomers


On April 19, 2023, Beijing time, the research team of Professor Hu Liangbing of the University of Maryland and the research team of Professor Ju Yiguang of Princeton University published a new study entitled “Depolymerization of plastics by means of electrified spatiotemporal heating” in the journal Nature.

This study reports a reaction strategy based on electrojoule heating, which can selectively pyrolyze multiple types of plastic materials to obtain high value-added monomer raw materials, which provides a new idea for the chemical recycling of waste plastics. In this study, aiming at the problems of poor selectivity of plastic pyrolysis reaction and low yield of high value-added products when the traditional reaction mode is adopted, the reaction temperature can be accurately controlled by combining compilable electrojoule pulse heating technology and multi-layer, porous reactor design, so as to effectively control the reaction path and product selectivity, and realize the conversion of plastics to monomers efficiently and continuously.

The corresponding authors of the paper are Hu Liangbing and Professor Ju Yiguang, and the first authors are Dong Qi, Aditya Dilip Lele, and Zhao Xinpeng.

While synthetic polymer materials (such as plastics, rubber, fabrics, etc.) continue to benefit mankind, the environmental and ecological problems caused by their mass production are also threatening the future of mankind. For waste polymer materials, especially waste plastics, existing recycling methods cannot efficiently treat and reuse them. Traditional methods such as incineration, landfill, secondary thermal processing and other methods not only fail to bring high value-added products, but also cause secondary damage to the environment and ecology. In recent years, thermochemical recovery has gradually become a hot spot in the industry, and many traditional thermochemical reaction paths such as high-temperature cracking, catalytic decomposition, catalytic oxidation, etc. have been proven to be used to prepare high value-added products such as monomers, fuels, lubricants, etc. However, traditional thermochemical treatment methods are still subject to problems such as poor selectivity and low yield of high value-added products. In addition, traditional thermochemical methods are mostly based on combustion and heating methods, which are energy-consuming, inefficient and accompanied by large carbon dioxide emissions, which cannot meet the needs of sustainable and green production. In contrast, the use of clean energy, especially renewable electricity, to recycle and reuse waste plastics can not only alleviate environmental pressure, but also turn waste into treasure, provide important chemical raw materials for chemical production, and achieve the goals of green chemical industry and circular economy. Compared with traditional thermal catalysis, electrochemical conversion has the advantages of high energy efficiency, low carbon emissions, controllable reaction conditions, and good product selectivity.

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In view of this, the research team of Professor Hu Liangbing of the University of Maryland and the research team of Professor Ju Yiguang of Princeton University jointly proposed a spatiotemporal temperature control (STH) method based on electrojoule heating, which can be used for continuous, highly selective and efficient plastic pyrolysis reaction for the preparation of high value-added products such as monomers and fuels. This study is based on the technology proposed by the team in 2022 to compile electrojoule pulse heating for thermochemical conversion of gas-phase reactants (Qi Dong et al., Programmable heating and quenching for efficient thermochemical synthesis, Nature 2022, 605, 470-476), By performing a simple multi-layer design of porous carbon material, that is, coke heating source, a reactor structure that can control the temperature gradient and pulse heating sequence at the same time is constructed. When starting from solid plastic reactants, the design can produce a continuous process of melting, siphoning, gasification and decomposition in a layered porous reactor through electroinduced heating, pyrolysis of plastic polymers into small molecules. Using polypropylene and polyethylene terephthalate as examples, the design can reduce the formation of highly unsaturated products and achieve a monomer yield of about 40%, which is much higher than that of catalyst-containing systems in most similar reactions (more than 25%). It is worth mentioning that this method uses electric energy to pulse heating the system, which not only reduces carbon emissions, but also obtains high energy efficiency by switching high and low temperature in the millisecond time scale. Based on this work, Professor Hu Liangbing, Professor Ju Yiguang and Dr. Dong Qi co-founded the start-up Polymer-X Inc. The company is committed to industrializing this technology for green chemical preparation and material recycling. (Source: Science Network)

Related paper information:https://doi.org/10.1038/s41586-023-05845-8



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