ADVANCED MATERIALS & PROCESSES | NOVEMBER/DECEMBER 2023 13 SUSTAINABILITY BRIEF CATALYTIC RECYCLING PROCESS FOR MIXED PLASTICS Nearly 90% of the mixed consumer plastics thrown away or placed in recycle bins end up buried in landfills or incinerated at commercial facilities that generate greenhouse gases and airborne toxins. To address the issue, scientists at the DOE’s Oak Ridge National Laboratory in Tennessee used carefully planned chemical design, neutron scattering, and high-performance computing to help develop a new catalytic recycling process. The new method offers a promising strategy for combating plastic waste, such as bottles, packaging, foams, and carpets. When scientists compared it to using individual catalysts for each type of plastic, the new multipurpose catalyst would generate up to 95% fewer greenhouse gases, require up to 94% less energy input, and result in up to a 96% reduction in fossil fuel consumption. The new organocatalyst has proven to deconstruct multiple polymers—such as polycarbonates, polyurethanes, polyethylene terephthalates, and polyamides—in around two hours. Until now, no single catalyst has been shown to be effective on all four of these polymers. The process provides many environmental advantages by replacing harsh chemicals for deconstructing polymers, as well as offering good selectivity, thermal stability, nonvolatility, and low flammability. Its effectiveness against multiple polymers also makes it useful for deconstructing the increasing amounts of multicomponent plastics, such as composites and multilayer packaging. Small-angle neutron scattering at ORNL’s Spallation Neutron Source was used to help confirm the formation of deconstructed monomers from the waste plastics. Also, the organocatalyst deconstructs the plastics at different temperatures, which facilitates sequentially recovering the individual monomers separately and in reusable form. ornl.gov. UPCYCLING POLYESTERS A team of researchers from Tokyo Metropolitan University developed a virtually waste-free method of converting polyesters into versatile building blocks that can be converted into a wide range of valuable chemical compounds. The team used a cheap solvent called morpholine and a small amount of a titanium-based catalyst to turn polyesters into morpholine amides. Not only can they be converted into intermediate compounds for making more polyester, but they can also be easily reacted to make ketones, aldehydes, and amines—all vital families of chemicals that are used to make a vast array of other, more valuable compounds. The new process does not require expensive reagents or harsh conditions and is essentially free of chemical waste. The yield is very high, and any unreacted solvent can be easily collected. They also found that only a small amount of catalyst was required to drive the reaction at a sensible speed, while all that is needed to separate the product is simple filtration. The main reaction proceeds at normal pressure, meaning that no special reaction vessels or devices are required. This makes the reaction easily scalable, even in the lab. The team demonstrated this by taking 50 g of PET material taken from an actual PET beverage bottle and reacting it with morpholine, getting more than 70 g of morpholine amide—a yield of 90%. www.tmu.ac.jp/english. Iron and steel production contributes roughly 7% to total global carbon emissions, with 74.5% of all steel made in coal-powered plants. Retrofitting these plants five years earlier than scheduled could reduce emissions by up to 70 gigatons by 2050, equivalent to two years of net global carbon emissions. The study was compiled by an international team led by University College London. www.ucl.ac.uk. ORNL’s organocatalyst deconstructs mixed plastics e iciently and quickly. Courtesy of Jill Hemman/ORNL, U.S. Dept. of Energy. A newly developed chemical process can upcycle polyesters to morpholine amides. Courtesy of Tokyo Metropolitan University.
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