PET Recycling. Nicholas Robusto Maggie Ifarraguerri Nathaniel Lawton Isabel Hefner

Transcription

1 PET Recycling Nicholas Robusto Maggie Ifarraguerri Nathaniel Lawton Isabel Hefner

2 OBJECTIVES Hydrolyze a sample of Polyethylene Terephthalate (PET) obtained from used soda bottles, and synthesize a dimer from the hydrolysis products. Utilize common laboratory techniques Introduction to PXRD Understand the role of PET Synthesis in industrial recycling processes

3 Polyethylene Terephthalate What is PET PET is an odorless, insoluble, nontoxic, thermoplastic polymer resin that can easily be synthesized and recycled Used in food and beverage storage, like water bottles Makes up 30% of recycled plastic in our households

4 PET Synthesis Monomer units of PET are synthesized to form a polymer chain via condensation polymerization refers to the removal of a molecule each time two monomers polymerize Structure

5 Industrial Process of PET Recycling Process: 1. Collection Consumer placing it in recycling bin City transporting it to recycling facility 2. Sorting: Separating the other types of plastic from the PET Separating the other types of plastic from the PET (usually done manually)

6 Industrial Process of PET Recycling 3. Chipping Chipping into small pieces allows the reaction to happen faster 4. Cleaning: Removes dirt, bits of metal etc. Removal of dirt, bits of metal etc. Washing with water for the dirt and food residue Water bath for the PET and other bits to separate 5. Reaction: Degradation of the polymer back into a monomer. Degradation of the polymer back into a monomer. Main focus of this lab is the reaction step

7 Uses Recycled PET Recycled PET can be used for almost all the same applications except food containers Examples of what recycled PET is used for: Clothes, carpet, packaging, flooring, shoes, furniture, film. 1,717,900,000 lbs recycled in 2012 in the USA (30% of the PET used in 2012). It is possible to have nearly 100% yield from PET recycling. First recycled in 1977

8 Week 1: Overall Reaction of Depolymerization Reaction Objective: Depolymerize the PET polymer into monomer form 1) KOH (2M ), 1-pentanol, Δ, Reflux (2 hours) PET 2) H 2 O, HCl (2M ) Terephthalic Acid

9 Depolymerization Reaction Depolymerize PET shavings into monomer form in two steps: Hydrolysis Addition of KOH Cleaves the O-R bonds of the polymer chain Formation of negatively charged organic salt, terephthalate Protonation Addition of HCl Forms hydrogen bonds with the negatively charged Oxygen Formation of terephthalic acid

10 Week 1: Depolymerization Procedure and Observations Hydrolysis 40 ml of 2M pentanolic KOH and 5.0 g PET shavings heated to reflux for 2 hours in a 100 ml round bottom flask Shortly into reflux, a thick white suspension formed in the flask. Later in reflux, the solution took on an opaque yellow color, with the cloudy white suspension. White solid suspension was terephthalate salt.

11 Week 1: Depolymerization Procedure and Observations Separation of Terephthalic Salt After refluxing, the solution was cooled for about 15 minutes at room temperature. Water was added to dissolve the terephthalate salt. Dissolving the white solid turned the solution into a viscous golden-yellow liquid.

12 Week 1: Depolymerization Procedure and Observations The solution was then gravity filtered in a Buchner funnel. The filtrate was placed in a separatory funnel, and the lower aqueous layer was set aside. The remaining pentanolic layer in the funnel was washed with water and the bottom aqueous layers were combined. The upper pentanolic layer was discarded.

13 Depolymerization After washing the aqueous layer and discarding the pentanolic layer, 5 ml of 2M HCl was added to the aqueous layer filtrate. As the solution was stirred, a white dense solid began to precipitate. The solid was vacuum-filtered out, and placed in a clean flask to dry until the next week s experiment After allowing the product to dry for a week, the melting point was taken. It was over 400ᵒ, which corresponds with the melting point of terephthalic acid.

14 Week 1: Depolymerization Results PXRD Uses X-Ray at many different angles to identify the product Each compound has a unique signature Verified that our week 2 product was the protonated monomer as desired

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16 PXRD Results The peaks for Terephthalic acid, Triclinic phase 1: 17.4 (83) 25.2 (46) 28.2 (100) 39.9 (10) Peaks for our product: Our peaks were very close to the peaks of triclinic phase 1, determined that we had made the correct form of our product terephthalic acid.

17 Week 2: Synthesis of Diethyl Terephthalate Reaction Objective: Synthesize the final diester product Deprotonation Tetramethyl ammonium hydroxide pentahydrate acted as a base, breaking the O-H bonds and deprotonating the product back to terephthalate, suspended in acetonitrile Acetylation Addition of ethyl iodide broke the I-R bonds and acetylated the negatively charged Oxygen of terephthalate with an ethyl chain Final product was diethyl terephthalate 1) Acetonitrile, Tetramethyl Ammonium Hydroxide, Δ, Reflux Terephthalic Acid 2) Ethyl Iodide, (Δ, Reflux 90 min) Diethyl Terephthalate

18 Week 2: Synthesis of Diethyl Terephthalate Procedure Deprotonation 1 gram of product was combined with 25 ml of acetonitrile and 2.5 grams of tetramethyl ammonium hydroxide pentahydrate, and placed in a 100 ml round-bottom flask with a magnetic stir bar. A Claisen adapter and water condenser were attached, and the solution was heated to reflux.

19 Week 2: Synthesis of Diethyl Terephthalate Procedure Acetylation The solution was left to reflux for 90 minutes Shortly into the reflux, the solution turned very thick, foamy-looking, and white with a yellow tint. Ethyl iodide was added, and a white precipitate condensed on the inside of the flask.

20 Week 2: Synthesis of Diethyl Terephthalate Procedure Isolation Once cooled, dicholoromethane was added to the solution Thick white precipitate thickened on the inside of the flask. Solution was gravity filtered to remove undissolved solids The filtrate was a watery liquid with a slightly cloudy suspension.

21 Week 2: Synthesis of Diethyl Terephthalate Procedure Filtrate was placed in a rotary evaporator Solvent was evaporated off Product was stored in an open beaker for a week and left to dry

22 Week 2: Synthesis of Diethyl Terephthalate Results Final product was a clumped, white grainy solid Melting Point taken to be C (Literature: 44.0 C), confirming identity of final product as diethyl terephthalate

23 Conclusion Diethyl terephthalate is the beginning monomer required for the formation of the polymer, PET Our experiment was a small-scale version of the industrial process for recycling PET. We depolymerized PET and got the monomer form that could be repolymerized into new PET. In the industrial process, this recycled monomer could be used to make new PET-based products. Industrial Recycling Process Why it is an effective process: Close to 100% product yield Can be done with a high quantity of PET

24 Sources CRC Handbook of Chemistry and Physics. 92nd edition ed. (2013, April 1). Boca Raton, FL: Taylor and Francis Group, LLC. Retrieved from CRC Handbook of Chemistry and Physics. 92nd edition ed.; CRC Press: Boca Raton, FL. Material Safety Data Sheet. (2014, March 31). Retrieved from ScienceLab: ScienceLab.com Recyclers, T. A. o. P. P., NAPCOR. Report on Postconsumer PET Container Recycling Activity 2012.