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PET Recycling

Lab presentation on experiment

Lindsay Hamilton

on 21 April 2010

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Transcript of PET Recycling

PET Recycling By:
Julia Cookson
Lindsay Hamilton
Shannon Karinshak
Lindsey McKissick
After Part 1 Group A Group B Characteristics:
White powdery solid

Mass of Solid:
3.953 g

Melting Point:
> 275°C

White powdery solid

Mass of Solid:
4.21 g

Melting Point:
> 275°C

Background >Poly-ethylene terephthalate (PET) is a common polymer.

>PET is a synthetic fiber used in some engineering fibers along with its more popular use, plastic bottles or containers that have the recycling number one symbol. Other uses can include space blankets, tape, sailcloth, carpet fibers, and insulation. This recycling number can be found on the bottom of the bottle inside the recycle triangle.

>Examples are soda bottles and ketchup bottles. The natural appearance of PET can be anywhere from clear to white depending on the processes that occur during polymerization, which is the esterification reaction. Introduction >>To recycle a polymer, it must first be cut up into small pieces and then depolymerized into its monomer form.

>>This can be achieved by hydrolysis, that is, a molecule of water is added to break a bond. In our reaction, this was done in two steps.

>>The addition of KOH in the first step created an organic monomer salt, and the addition of HCl precipitated the organic monomer by adding the final hydrogen.

>>The end product of step one was terephthalic acid.

>>In the second step, acetonitrile was the solvent and tetramethyl ammonium hydroxide pentahydrate was added as a catalyst.

>>Ethyl iodide was then added in order to acetylate the terephthalic acid and turn it into the final product, diethyl terephthalate >>In practicality, chemical PET recycling is only cost-efficient when preformed in high quantities, more than 50,000 tons per year.

>>Just like in the lab experiment, the bottles must first be “flaked” or “peletted” before recycling can begin.

>>The same depolymerization process that occurs in the lab must be done on a large scale under high pressure and under supercritical conditions. Overall Reactions Part 1

Part 2 Machanism Part 1 Mechanism Part 2 Thoeretical Yield 5.00g PET x (1 mol of PET/ ? g of PET)

Very difficult to determine the molecular weight of a polymer Percent Yield Group A

(3.953g/4.138g) x 100 =95.53%

4.138g is the value of product from step one that was obtained from the literature
Group B

(4.291g/ 4.138g) x 100 =103.70%


>Not completely dry Predicted Product from Week 1 It was decided that the solid was most likely terephthalic acid

Terephthalic Acid:
>has a melting point of 400°C
>Is a white, powdery solid
>White solid in yellow liquid
>Separated solid from liquid using vacuum filtration

Melting Point:
After Part 2 Group A Group B Characteristics:
>White solid in yellow liquid
>Separated liquid from solid using vacuum filtration

Melting Point:
41.0-43.0°C Predicted Product from Week 2 It was decided that the solid was most likely diethyl terephthalate

Diethyl Terephthalate:
>has a melting point of 44°C
>Is a white, powdery solid
Reactant vs. Product Polyethylene Terephthalate

Diethyl Terephthalate Summary >Polyethylene Terephthalate was recycled into its monomer form, diethyl terephthalate

>A polymerization reaction will change the diethyl terephthalate to PET Our opinion on Recylcling Now >Long, slow process
>Many steps
>A large amount of PET yields a small amount of diethyl terephthalate
>Large quantities of other reagents and solvents are needed for success
>Recycling is great!
>You should first reuse the bottles and then put them in the appropriate recycling receptacle
Week One >Bottle pieces from no. 1 plastic were combined in a round-bottom flask with pentanolic KOH and refluxed for two hours

>About 40 minutes into the reflux Group A’s solution was smooth and resembled eggnog; group B had a thick, congealing solution

>After refluxing, we removed the clear bottom aqueous layer and added HCl, which turned the solution white and thick again
Week Two Week One (Continued) >After vacuum filtration we were left with a white solid that was dry and crumbly. Its identity was terephthalic acid

>Group A yielded 3.953 g of product; Group B yielded 4.291 g

>Melting point for both groups was >275°C. At this temperature the Buchi machine shut off!

>After later investigation, we found that the melting point for terephthalic acid is 400°C
Week Two (continued) >We added 1 g of our product, terephthalic acid with acetonitrile and tetramethyl ammonium hydroxide pentahydrate and refluxed for 90 minutes

>After a cloudy suspension formed, we added ethyl ioddide dropwise until 1.0 mL was reached; shortly after, white crystals formed on the sides of the round-bottom flask

>As the reflux continued, the stir bar began to mix the suspension into the solvent until almost all of the suspension was being swirled around the flask

>After the reflux, dichloromethane was added and the mixture was filtered to remove all the undissolved solvents
The next step was evaporating off the solvent using the rotary evaporator.
>Both experiments yielded a yellow liquid with a white precipitate that was suction filtered to get the white solid alone

>The white solid was the desired product diethyl terephthalate

One of the groups had the correct melting point for diethyl terephthalate (42-45°C) and one did not. Can you guess which group was which?
Group B >Group B had the characteristic melting point of diethyl terephthalate, where group A’s melting point was >50°C

>Both groups were surprised by these results, seeing as how it seemed group B goofed on step 1 and group A had a seemingly perfect product.

>What could have gone wrong? Reflux Apparatus Rotary Evaporator Sources John Vanderson, TA, CLC, 11:00 am, Tuesday, April 6, 2010


Chem 2546 Organic Chemistry Lab Manual

Kaufman, D.; Wright, G.; Kroemer, R.; Engel, J. “New” Compounds from Old Plastics: Recycling PET Plastics via Depolymerization J. Chem. Educ. 1999, 76, 1525-1526. And...

Eveline Van der Aa...

The greatest Ochem TA ever!!
Questions? Introduction (Continued)
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