Process for recovering and reusing depolymerization catalyst
The present disclosure relates to the recovery of an alkoxide catalyst used in a process depolymerizing a polyester to form a diacid or diester and a diol. The present disclosure also relates to the recovery of an alkoxide catalyst used in a process depolymerizing polyethylene terephthalate to form dimethyl terephthalate and mono ethylene glycol.
1. A process for depolymerizing a polyester, wherein the process comprises admixing the polyester with a mixture comprising an alkoxide; wherein the alkoxide is recovered from an alkoxide containing mother liquor using a process comprising:
(i) an adsorption cycle;
(ii) a wash cycle; and
(iii) a desorption cycle.
2. The process of claim 1 , wherein the polyester is polyethylene terephthalate (PET).
3. The process of claim 1 , wherein the adsorption cycle comprises contacting the alkoxide containing mother liquor with an adsorbent, thereby adsorbing the alkoxide.
4. The process of claim 3 , wherein the wash cycle comprises washing the adsorbent with a wash solvent, thereby eliminating ester salts, pigments, and/or dyes adsorbed during the adsorption cycle.
5. The process of claim 3 , wherein the desorption cycle comprises washing the adsorbent with a desorption solvent, thereby obtaining a mixture comprising the alkoxide and the desorption solvent.
6. The process of claim 5 , wherein the washing is performed until at least about 30% of the alkoxide is desorbed from the adsorbent.
7. The process of claim 1 , wherein the polyester comprises polyethylene terephthalate (PET) and the depolymerizing forms a terephthalate, and mono ethylene glycol (MEG).
8. The process of claim 1 , wherein the alkoxide is sodium methoxide, sodium glycoxide, potassium ethoxide, aluminum tri-n-propoxide, tetrabutylammonium methoxide, or any combinations thereof.
9. The process of claim 1 , wherein the alkoxide is sodium methoxide.
10. The process of claim 1 , wherein the alkoxide is sodium glycoxide.
11. A system for recovering an alkoxide from an alkoxide containing mother liquor, the system comprising:
(i) an alkoxide containing mother liquor;
(ii) an adsorbent;
(iii) a wash solvent; and
(iv) a desorption solvent.
12. The system of claim 11 , wherein the alkoxide containing mother liquor further comprises a diol.
13. The system of claim 11 , wherein the alkoxide containing mother liquor further comprises mono ethylene glycol (MEG).
14. The system of claim 11 , wherein the adsorbent is silica gel, a silicate derivative, Al 2 O 3 , polymeric alumina, zeolites, activated carbon, polysulfones, polysulfates, polycarboxylates, or any combinations thereof.
15. The system of claim 11 , wherein the wash solvent is a protic solvent.
16. The system of claim 11 , wherein the wash solvent is an alcoholic solvent.
17. The system of claim 11 , wherein the wash solvent is methanol.
18. The system of claim 11 , wherein the desorption solvent is a protic solvent.
19. The system of claim 11 , wherein the desorption solvent is an alcoholic solvent.
20. The system of claim 11 , wherein the desorption solvent is methanol.
21. The system of claim 11 , wherein the wash solvent is an aprotic solvent.
22. The system of claim 11 , wherein the desorption solvent is an aprotic solvent.