Depolymerizing polyethylene to propylene (IMAGE)
Caption
UC Berkeley chemists have developed a new process, called isomerizing ethenolysis, to degrade polyethylene plastics, such as the milk bottle shown in the background, to propylene — the building block for another plastic, polypropylene. In the graphic, polyethylene chains (long web-like strands represented at the molecular level by the ball-and-stick figures) are first split by a metal catalyst (green balls) in the presence of ethylene (upper left) in a reaction known as “olefin metathesis.” A molecule of propene is released as the result of this process. The shorter polymer chain which results (right) has a carbon-carbon double bond at the end. A different catalyst (blue ball) initiates a round of “olefin isomerization,” where the double bond on the end of the polymer chain is shifted inward by one carbon atom. The isomerized polymer chain is then ready to undergo more cycles of metathesis and isomerization until all of it has been transformed into propylene.
Credit
Brandon Bloomer, UC Berkeley
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