A high-performance catalyst that facilitates the decomposition and recycling of plastic waste has been developed domestically.
KAIST announced on the 26th that a joint research team including Professor Min-Ki Choi of the Department of Bio and Chemical Engineering at KAIST and Professor Hye-Young Shin of the Graduate School of Energy Science and Technology at Chungnam National University has elucidated the mechanism of the dechlorination reaction occurring during the decomposition and recycling process of waste plastics, and developed a high-performance catalyst capable of effectively removing chlorine with a trace amount of platinum.
According to the joint research team, more than 400 million tons of plastic are consistently produced worldwide each year, but only about 7% of this is recycled or reused, while over 60% is incinerated or landfilled.
Incinerated or landfilled plastics cause various environmental and economic problems. For the same reasons, the importance of research on the chemical recycling of waste plastics has been steadily emphasized. In fact, research on plastic recycling is actively underway in countries around the world.
In particular, chemical recycling methods using pyrolysis are industrially noteworthy because they can omit the complex and uneconomical waste plastic sorting process.
The oil produced by this method can be converted into ethylene and propylene, which are raw materials for plastics, enabling a circular economy for plastics.
However, waste plastic contains more than 10% polyvinyl chloride (PVC), which leaves about 2000 ppm of chlorine in the pyrolysis oil after pyrolysis.
The remaining chlorine can cause corrosion of reactors and catalyst poisoning in subsequent processes, reducing process efficiency. Therefore, chlorine removal is essential in the decomposition and recycling of waste plastics.
On the other hand, the chlorine removal process has not been deeply studied until recently, and there have been no cases where the reaction mechanism or factors affecting activity have been identified.
The joint research team focused on this situation and elucidated the mechanism of the dechlorination reaction using a catalyst containing a trace amount (0.1 wt%) of platinum supported on gamma alumina.
Based on the elucidated mechanism, when a high-performance catalyst was designed and tested, they confirmed a reaction mechanism in which the bond between carbon and chlorine is broken, and hydrogen activated on platinum is transferred to the surface of gamma alumina to remove chlorine in the form of hydrochloric acid (HCl).
In particular, the joint research team revealed that when the catalyst they directly developed was used in the pyrolysis oil reaction of marine waste plastics containing a large amount (7500 ppm) of chlorine, more than 98% of the chlorine was effectively removed, opening up the possibility of improving efficiency and economic feasibility in the decomposition and recycling of marine waste plastics.
Professor Choi emphasized, “Dechlorination is a very important factor in the process of decomposing and recycling waste plastics, but it is true that it has not been deeply studied until now. This research is the world’s first to elucidate the mechanism of the dechlorination reaction, which will contribute to accelerating the development of high-performance dechlorination catalysts.”
Meanwhile, this research was conducted with the support of the Lotte Chemical Carbon Neutral Research Center and the Mid-Career Researcher Support Project of the National Research Foundation of Korea. The research results, co-first authored by Seokjin, a doctoral student in the Department of Bio and Chemical Engineering at KAIST, and Phan Thi Yen Nhi, a master’s student at the Graduate School of Energy Science and Technology at Chungnam National University, were published online on the 28th of last month in the Journal of the American Chemical Society.
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