A new membrane with the scalability of a polymer and the precision of zeolite molecular sieves may help make the production of a key fundamental chemical less expensive and more energy-efficient.
Paraxylene is a key component of hundreds of other chemicals, including polyethylene terephthalate (PET) and polyester. But it takes heavy lifting to separate it from its isomers, orthoxylene and metaxylene. This trio must either be separated by crystallization, taking advantage of the slightly different freezing points of the three molecules, or by adsorption. But crystallization is extremely energy-hungry, says Ryan Lively, a chemical engineer at the Georgia Institute of Technology. And adsorption requires incredibly complex and expensive machinery, plus an additional distillation step that also requires energy. Each year, Lively says, the separation of paraxylenes and similar molecules consumes enough energy to power 40 million homes...
In new research funded by ExxonMobil, Lively and his colleagues have tested a low-energy alternative: membrane separation.
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