Process for purification of recovered glycol from chemical recycling of waste polyester
A process for purifying polyester-grade ethylene glycol from crude ethylene glycol containing at least a first component and a second component that have a boiling point below that of ethylene glycol that includes (a) providing a stream of crude ethylene glycol by depolymerizing polyethylene terephthalate in a chemical recycling process; (b) introducing the crude ethylene glycol stream into a first distillation column for distilling the first component and removing the first component from the process; (c) withdrawing a first stream from the lower portion of the first distillation column and feeding the first stream into a second distillation column for distilling the second component and removing the second component from the process; (d) withdrawing a second stream from the lower portion of the second distillation column and feeding the second stream into a third distillation column; and (e) recovering polyester-grade ethylene glycol from the third distillation column.
1 . A process for purifying polyester-grade ethylene glycol from crude ethylene glycol containing at least a first component and a second component that have a boiling point below that of ethylene glycol, comprising:
(a) providing a stream of crude ethylene glycol by depolymerizing polyethylene terephthalate in a chemical recycling process;
(b) introducing the crude ethylene glycol stream into a first distillation column for distilling the first component and removing the first component from the process, wherein a portion of a tail stream from the first distillation column is introduced into a first reboiler to provide heat energy to vaporize a portion of the tail stream for reintroduction into the first distillation column;
(c) withdrawing a first stream from a bottom of the first distillation column and feeding the first stream into a second distillation column for distilling the second component and removing the second component from the process, wherein a portion of a tail stream from the second distillation column is introduced into a second reboiler to provide heat energy to vaporize a portion of the tail stream for reintroduction into the second distillation column;
(d) withdrawing a second stream from a bottom of the second distillation column and feeding the second stream into a third distillation column, wherein a portion of a tail stream from the third distillation column is introduced into a third reboiler to provide heat energy to vaporize a portion of the tail stream for reintroduction into the third distillation column; and
(e) recovering polyester-grade ethylene glycol from top of the third distillation column, wherein the purity of the polyester-grade ethylene glycol is at least 99.9%.
2 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein the first component is methanol.
3 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein the second component is water.
4 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 2 , wherein the purity of the methanol is 99.9%.
5 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein the polyester-grade ethylene glycol contains less than 0.01 wt % chain terminators.
6 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein the first distillation column, second distillation column, and third distillation column each comprise a partial condenser.
7 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein the first distillation column operates at a temperature of less than 56° C. at a pressure of 110 mm Hg.
8 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein the second distillation column operates at a temperature range of greater than 56° C. to 196° C., and a pressure of 110 mm Hg.
9 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein the third distillation column operates at a temperature range of greater or equal to 197° C. to less than 202° C., and a pressure of 110 mm Hg.
10 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 1 , wherein no catalysts or other additional components are introduced into the process of steps (b) through (d).
11 . A process for purifying polyester-grade ethylene glycol from crude ethylene glycol, comprising:
(a) providing crude ethylene glycol from a process for the depolymerization of polyethylene terephthalate (PET) to form a terephthalate, comprising:
(i) admixing the polyethylene terephthalate (PET) with a first solvent that is methanol to yield a first mixture;
(ii) adding a glycoxide to the first mixture;
(iii) adding a second solvent that is methanol;
(iv) admixing; and
(v) evaporating or distilling crude ethylene glycol from the terephthalate;
(b) introducing the crude ethylene glycol stream into a first distillation column for distilling a first component and removing the first component from the process, wherein a portion of a tail stream from the first distillation column is introduced into a first reboiler to provide heat energy to vaporize a portion of the tail stream for reintroduction into the first distillation column;
(c) withdrawing a first stream from a bottom of the first distillation column and feeding the first stream into a second distillation column for distilling a second component and removing the second component from the process, wherein a portion of a tail stream from the second distillation column is introduced into a second reboiler to provide heat energy to vaporize a portion of the tail stream for reintroduction into the second distillation column;
(d) withdrawing a second stream from a bottom of the second distillation column and feeding the second stream into a third distillation column, wherein a portion of a tail stream from the third distillation column is introduced into a third reboiler to provide heat energy to vaporize a portion of the tail stream for reintroduction into the third distillation column; and
(e) recovering polyester-grade ethylene glycol from top of the third distillation column, wherein the purity of the polyester-grade ethylene glycol is at least 99.9%.
12 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 11 , wherein the crude ethylene glycol contains one or more of the following methanol, ethylene glycol, water, diethylene glycol, CHDM, BHET, BHEI, Methyl 4-formylbenzoate, pigments and dyes, 2-Methoxyethanol, 2-Butoxyethanol, and 2-(2-Methoxyethoxy)-Ethanol.
13 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 11 , wherein the first component is methanol.
14 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 11 , wherein the second component is water.
15 . The process for purifying polyester-grade ethylene glycol from crude ethylene glycol according to claim 11 , wherein no catalysts or additional components are introduced into the process of steps (b) through (d).