"New" Compounds from Old Plastics: Recycling PET Plastics via Depolymerization. An Activity for the Undergraduate Organic Lab

Don Kaufman , Geoff Wright , Ryan Kroemer and Josh Engel
Department of Chemistry, University of Nebraska at Kearney, Kearney, NE 68849
J. Chem. Educ., 1999, 76 (11), p 1525
DOI: 10.1021/ed076p1525
Publication Date (Web): November 1, 1999
History, Education, and Documentation

Abstract

This paper describes work done to develop a meaningful undergraduate organic lab activity that illustrates chemistry of the real world while utilizing reactions typically included in the organic lecture and lab. We show how a common plastic can be converted into several compounds using ester hydrolysis and SN2 reactions.

Contributing to the critical shortage of landfill space faced by many communities is the large quantity of plastic refuse. Thus, there is a real need to recycle plastic products. One way to recycle plastics such as polyethyleneterephthalate (PET), the polyester from which numerous consumer products such as 2-liter soda bottles are made, is to depolymerize them and then to use the resulting monomers to produce new products. PET is industrially depolymerized via an acid-catalyzed transesterification reaction conducted under conditions of high temperature and pressure that are not feasible in the undergraduate lab. Despite literature reports that PET is remarkably resistant to hydrolysis, we found that PET can be readily hydrolyzed by refluxing with potassium hydroxide or potassium tert-butoxide in amyl alcohol to give terephthalic acid in high yield. It is then possible to readily synthesize terephthalate diesters via SN2 reactions of ammonium terephthalate salts with alkyl halides. Fischer esterification can also be used to prepare the diesters, but yields are significantly lower.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Organic Chemistry

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Consumer Chemistry
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  • Received: August 03, 2009

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