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CEBC Discovery May Reduce Environmental Impact of Polyesters

Monday, May 25, 2009

CEBC researchers are developing technologies to minimize carbon dioxide release during the production of ingredients needed to make polyester.

Grocery stores are full of plastic containers of water, juice, peanut butter, aspirin and more.  Turn the bottles upside down, and you’ll find many branded with triangles and the word PETE.  The triangles mean the bottle can be recycled.  But who’s PETE?

PETE stands for polyethylene terephthalate – the key ingredient in making the bottle.  Most people call it polyester.  It’s a plastic made of a very long chain of identical chemical links. 

 

Polyesters Are a Megaton Business

Polyesters go into more than plastic bottles.  Remember the leisure suits of the ‘70s?  Many of today’s clothes, though not as groovy, are also made from polyester.  So are bed sheets, curtains, tarps, tents, films (like Mylar) and more.

It takes a lot of polyester to make these products.  Think tons – megatons.  And making those megatons requires a key ingredient called terephthalic acid – TPA for short. 

In 2006, around 60 billion pounds of TPA were made worldwide.  That’s the same weight as 82 Empire State buildings!  

To make TPA, you dissolve a chemical made from petroleum (para-xylene) in acetic acid (also known as vinegar).  Add air, metal catalysts and a little bromide.  Turn up the heat.  Presto: TPA is formed. 

But there are problems with this process.  Impurities crop up.  And it gets so hot that some of the chemicals in the mix burn.  This adds about 3 million tons of carbon dioxide a year to the atmosphere–equivalent to what half a million cars release each year.

Cleaning Up PETE’s Footprint

Researchers at the Center for Environmentally Beneficial Catalysis want to shrink the environmental impact of producing megatons of TPA.  They are developing a new inherently safe spray process technology. This unique method mixes the chemicals with oxygen to better control the reaction. 

The CEBC technique has the potential to minimize impurities, which require energy to remove, and to prevent acetic acid burning, which generates wasteful carbon dioxide. If it works, that would reduce carbon dioxide emissions.  Early studies indicate that the CEBC method produces 30 percent less carbon dioxide than the traditional method.  Researchers are working to improve on that number. 

CEBC industry partners want to commercialize this method for making TPA.  Bala Subramaniam, CEBC Director, says, “This new technology may also be applied to several other similar processes.  It is one example of how to get all of the carbon into the product without losing any as carbon dioxide.” 

Right now, for example, reducing the carbon footprint for the megaton chemical ethylene oxide is on CEBC’s radar.

But, what happens to the megatons of non-degradable polyester plastics produced every year? You can help.  As a consumer, you can reduce, reuse and recycle your old pal PETE.    

Then RE-peat – all your life.



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