Question

Lab: Hydrolysis of polyethylene terephthalate using KOH

1. Why do we need to keep this reaction well stirred?

2. what is the scope of this reaction?

3. IR and NMR interpretation of dimethyl terephthalate

4. What is the role of 1-pentanol and water in this experiment?

5. Explain Alkaline hydrolysis of PET using KOH (in words).

Answer 1

2. Polyethylene terephthalate (PET) is a thermoplastic saturated polyester and It is largely consumed in textile industries for fabrics, and the packaging industry for soft drink bottles. Wide applications of PET in the packaging industries is mainly due to its high strength, low weight, low permeability to gases (mainly CO2), smooth surface.

To prevent ecological imbalance, the main interest in PET recycling is continuously increasing due to its substantial production in waste stream and its high resistance to the atmospheric and biological agents. Considering the economic aspects, chemical recycling of waste PET is required.

hydrolysis methods of PET are methanolysis, glycolysis, and hydrolysis of which hydrolysis of PET to terephthalic acid (TA) and mono ethylene glycol (MEG) take place.

3.

1-pentanol can be used as a solvent to produce anhydrous OH- to produce tetraphthalic acid .At last to neutralise Potassium salt of tetraphthalic acid we use  Sulfuric acid dissolved in water.

5. The hydrolysis of polyethylene terephthalate(PET) in potassium hydroxide solution can be carried out at high temp. with prolonged period.The products obtained are ethylene glycol and terephthalic potassium salt in the liquid phase. These can be separated by acidification to obtain solid terephthalic acid.