Possible solutions for hard-to-recycle plastics



Plastics difficult to recycle – Image source: https://phys.org/news/2021-04-solutions-hard-to-recycle-plastics.html

In the United States, less than 9% of plastic waste is recycled. Instead, over 75% of plastic waste ends up in landfills and up to 16% is burned, a process that releases toxic gases into the atmosphere.

Researchers at the Center for Plastics Innovation (CPI) at the University of Delaware have developed a direct method to convert single-use plastic waste (plastic bags, yogurt pots, plastic bottles and caps, packaging, etc. ) in ready-to-use molecules for jet fuels, diesel and lubricants.

The work, reported in an article by Scientists progress on Wednesday April 21, focuses on using a new catalyst and a unique process to quickly break down these most difficult to recycle plastics, known as polyolefins. Polyolefins make up 60-70% of all plastics manufactured today.

The process developed by UD requires about 50% less energy than other technologies, and it does not involve the addition of carbon dioxide to the atmosphere, saving emissions compared to other commonly used techniques. This can be done in just a few hours at a low temperature, around 250â°C, slightly above the oven temperature that you could use for roasting vegetables or baking puff pastry at home.

It’s important to note that the UD team’s method can process a variety of plastics, even when mixed together, an advantage considering how recyclables are handled.

Creation of ready-to-use molecules

The UD research team used a chemical process called hydrocracking to break down plastic solids into smaller carbon molecules, then added hydrogen molecules to each end to stabilize the material to be used.

Catalytic cracking is nothing new. Refineries have used it for years to convert heavy crude oil into gasoline.

The research team’s method, however, does more than just break down the plastic. It also converts the material into branched molecules which allow them to be more directly translated into a final product.

The catalyst itself is actually a hybrid material, a combination of zeolites and mixed metal oxides.

Zeolites are known to have properties that make them effective in creating branched molecules. Zeolites are found in elements such as water purification or softening systems and household detergents, where they neutralize minerals like calcium and magnesium, making hard water softer and improving the process of cleaning. laundry.

Mixed metal oxides, on the other hand, are known for their ability to break down large molecules in just the right amount without overdoing it. The antacid in your medicine cabinet, for example, is a metal oxide used to break down or neutralize the acid that causes your stomach upset.

Alone, these two catalysts function poorly. Together, the suit works magic, melts plastics and leaves no plastic behind.

Sustainable solutions, circular economy

Reducing plastic waste by chemically converting it into fuels can play an important role in driving a circular economy, where materials are recycled into something new at the end of their useful life, instead of being thrown away. . The recycled components can be used to do the same thing again or, in the case of fuels, be recycled into higher value products, creating economic and environmental gains.

The next steps in IPC research include exploring what other plastics the team’s method can process and what products it can make. For starters, the team hopes to expand collaborations with colleagues on campus and at the Center for Plastics Innovation to explore other ways to make valuable products by eliminating waste.

As this circular economy takes hold, the world will need to make less original plastics as we will reuse materials made today in the future.

Another goal is to develop methods to improve the recycling process itself.

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