Claims
- 1. A process for purifying ethylene glycol recovered from scrap polyester by contacting the recovered liquid ethylene glycol with, in either order,
- a) a first adsorbent that has a high affinity for polar contaminants, and
- b) a second adsorbent that has a high affinity for non-polar contaminants.
- 2. A process of claim 1, wherein the first adsorbent is activated alumina.
- 3. A process of claim 1, wherein the second adsorbent is activated carbon.
- 4. A process of claim 1, wherein the ethylene glycol is contacted first with the first adsorbent and then with the second adsorbent.
- 5. A process of claim 1, wherein the ethylene glycol is contacted first with the second adsorbent and then with the first adsorbent.
- 6. A process of claim 1, wherein the ethylene glycol is contacted with the first adsorbent and the second adsorbent at the same time.
- 7. A process of claim 1, wherein the first and second adsorbents are present in a ratio of 1:1 to 1:10 parts by weight.
- 8. A process for recovering and purifying liquid ethylene glycol from polyester resins using apparatus that comprises:
- a dissolver for receiving polyester,
- a reactor for depolymerizing polyester into monomer components, and
- a rectifier for separating monomer components;
- the process comprising
- a) adding polyester to the dissolver and combining it with melt from the reactor to reduce the chain length of the polyester,
- b) transferring reduced chain length polyester from the dissolver to the reactor,
- c) passing super-heated methanol through the reactor to depolymerize polyester into its constituent monomers,
- d) transferring depolymerization products from the reactor to the rectifier;
- e) separating the depolymerization products in the rectifier into a vapor phase containing monomer components and a liquid phase containing higher molecular weight materials;
- f) recovering ethylene glycol exiting the rectifier,
- g) purifying the ethylene glycol recovered in step f) by distillation, and
- h) further purifying the ethylene glycol purified in step g) by contacting it with, in either order,
- i) a first adsorbent that has a high affinity for polar contaminants, and
- ii) a second adsorbent that has a high affinity for non-polar contaminants.
- 9. A process of claim 8, wherein the first adsorbent is activated alumina and the second adsorbent is activated carbon.
- 10. A process of claim 9, wherein the first and second adsorbents are present in a ratio of 1:1 to 1:10 parts by weight.
CROSS REFERENCE TO RELATED APPLICATION
Reference is made to and priority claimed from U.S. Provisional application Ser. No. US 60/001,631, filed 28 Jul. 1995, entitled PURIFICATION OF ETHYLENE GLYCOL RECOVERED FROM POLYESTER RESINS.
US Referenced Citations (10)