US5473102A
Expired / Lapsed
US
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Process for recovery of aromatic acid and dihydric alcohol from waste polyester resins
Assignee: BP Corp North America Inc
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Filing: 1994-10-05
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Granted: 1995-12-05
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Expires: 2014-10-05
Abstract
Abstract Processes are disclosed for recovery and purification of dibasic aromatic acids from waste polyester film, fiber, bottles, manufacturing residues, and other manufactured articles. The processes comprises: depolymerization of polyester resin in a molten polyester resin containing solvent with superheated stem, and vaporization of the aromatic carboxylic acid and other volatile products of hydrolysis to obtain a vaporized mixture containing aromatic acid, dihydric alcohol, other volatile products of hydrolysis, and water. This vapor mixture is, advantageously, substantially free of less volatile and non-volatile impurities including metals, and many colored and color causing compounds, which are, typically, found in post-consumer polyester resins. Crude acid is, optionally, purified by hydrogenated in an aqueous solution at elevated temperatures and pressures in the presence of hydrogen and an insoluble metal-containing catalyst, which is thereupon separated from the aqueous solution, and purified dibasic aromatic acid recovered by crystallization and mechanical separation from the aqueous solution. Purified terephthalic acid has, typically, a L*-value in a rage of from about 95 to about 100, an a*-value in a rage of from about -1 to about +1, and a b*-value in a range of from about 0.5 to about 2.
Inventors
- 👤 Floyd Johnson
- 👤 David L. Sikkenga
- 👤 Kalpana Danawala
- 👤 Bruce I. Rosen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:14
CPC Classifications
C; C07; C07C; C07C51/00; C07C51/09
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
96 words
A process for preparation of aromatic acid vapors and dihydric alcohol vapors from polyester resins comprising repeating units of dibasic aromatic acid residue and repeating units of dihydric alcohol residue linked by ester bonds, which process comprises: treating the polyester resins with excess superheated stem in a pool containing molten resins, and continuously removing therefrom a mixture of vapors containing aromatic acid, dihydric alcohol, other volatile products of hydrolysis of the ester bonds, and water in an mount of at least about 2 moles of water per mole of aromatic acid in the mixture of vapors.
Claim 2
Dependent Claim
96 words
A process for preparation of aromatic acid vapors and dihydric alcohol vapors from polyester resins comprising repeating units of dibasic aromatic acid residue and repeating units of dihydric alcohol residue linked by ester bonds, which process comprises: treating the polyester resins with excess superheated stem in a pool containing molten resins, and continuously removing therefrom a mixture of vapors containing aromatic acid, dihydric alcohol, other volatile products of hydrolysis of the ester bonds, and water in an mount of at least about 2 moles of water per mole of aromatic acid in the mixture of vapors.
Claim 3
Dependent Claim
29 words
The process according to claim 1 wherein the dibasic aromatic acid is at least one member of the group consisting of isophthalic acid, terephthalic acid, and 2,6-naphthalene dicarboxylic acid.
Claim 4
Dependent Claim
30 words
The process according to claim 1 wherein polyethylene terephthalate resins are treated with excess superheated stem at temperatures in a rage of from about 250° C. to about 450° C.
Claim 5
Dependent Claim
30 words
The process according to claim 1 wherein poly( ethylene-2,6-naphthalate) resins are treated with excess superheated stem at temperatures in a range of from about 250° C. to about 450° C.
Claim 6
Dependent Claim
163 words
A process for recovering dibasic aromatic acid and dihydric alcohol from polyester resin comprising repeating units of dibasic aromatic acid residue and repeating units of dihydric alcohol residue linked by ester bonds which process comprises: depolymerizing polyester resin in a molten polyester resin containing solvent under conditions suitable for hydrolysis of ester bonds to form a reaction mixture containing aromatic acid, dihydric alcohol, impurities and other components of the resin; vaporizing from the reaction mixture the aromatic carboxylic acid, dihydric alcohol, and other volatile products of hydrolysis with excess superheated stem to obtain a continuous effluent of depolymerization comprising aromatic acid, dihydric alcohol, and other volatile products of hydrolysis, and water in an amount of at least about 2 moles of water per mole of aromatic acid in the mixture of vapors; and separating from the effluent of depolymerization a solid product of crude dibasic aromatic acid substantially free of dihydric alcohol, but containing organic impurities, to form a residue containing dihydric alcohol.
Claim 7
Dependent Claim
163 words
A process for recovering dibasic aromatic acid and dihydric alcohol from polyester resin comprising repeating units of dibasic aromatic acid residue and repeating units of dihydric alcohol residue linked by ester bonds which process comprises: depolymerizing polyester resin in a molten polyester resin containing solvent under conditions suitable for hydrolysis of ester bonds to form a reaction mixture containing aromatic acid, dihydric alcohol, impurities and other components of the resin; vaporizing from the reaction mixture the aromatic carboxylic acid, dihydric alcohol, and other volatile products of hydrolysis with excess superheated stem to obtain a continuous effluent of depolymerization comprising aromatic acid, dihydric alcohol, and other volatile products of hydrolysis, and water in an amount of at least about 2 moles of water per mole of aromatic acid in the mixture of vapors; and separating from the effluent of depolymerization a solid product of crude dibasic aromatic acid substantially free of dihydric alcohol, but containing organic impurities, to form a residue containing dihydric alcohol.
Claim 8
Dependent Claim
29 words
The process according to claim 5 wherein the dibasic aromatic acid is at least one member of the group consisting of isophthalic acid, terephthalic acid, and 2,6-naphthalene dicarboxylic acid.
Claim 9
Dependent Claim
43 words
The process according to claim 5 wherein the process further comprises: fractionating at least a portion of a residue resulting from the separation of aromatic acid from the effluent of depolymerization to obtain a dihydric alcohol product substantially free of lower boiling compounds.
Claim 10
Dependent Claim
37 words
The process according to claim 5 wherein both the depolymerization of polyester resin and the vaporization of the aromatic carboxylic acid and other volatile products of hydrolysis, are carried out together in one or more reaction zones.
Claim 11
Dependent Claim
38 words
The process according to claim 8 wherein polyethylene terephthalate resins are treated with excess superheated stem at temperatures in a range of from about 250° C. to about 450° C. and pressures sufficient to maintain a molten phase.
Claim 12
Dependent Claim
37 words
The process according to claim 8 wherein poly(ethylene-2,6-naphthalate) resins are treated with excess superheated stem at temperatures in a rage of from about 250° C. to about 450° C. and pressures sufficient to maintain a molten phase.
Claim 13
Dependent Claim
84 words
The process according to claim 8 wherein the process further comprises: fractionating at least a portion of a residue resulting from the separation of aromatic acid from the effluent of depolymerization to obtain a dihydric alcohol product fraction substantially free of lower boiling compounds and a fraction containing lower boiling compounds; and wherein the depolymerization of polyester resin is carried out in the presence of at least a portion of the fraction containing lower boiling compounds in one or more of the reaction zones.
Claim 14
Dependent Claim
74 words
The process according to claim 5 wherein the process further comprises: reduction of at least a portion of the organic impurities in the crude dibasic aromatic acid in an aqueous solution at elevated temperatures and pressures and in the presence of hydrogen and at least one insoluble Group VIII noble metal-containing catalyst; separating the solid noble metal-containing catalyst from the aqueous solution; and crystallizing and separating purified dibasic aromatic acid from the aqueous solution.
Claim 15
Dependent Claim
58 words
The process according to claim 12 wherein the dibasic aromatic acid is terephthalic acid, the noble metal is at least one member of the group consisting of palladium and rhodium, and the purified dibasic aromatic acid has a total metals content of less than 100 ppm and contains less than 1000 ppm total of 4-carboxybenzaldehyde and toluic acid.
Claim 16
Dependent Claim
188 words
A process for recovering terephthalic acid from polyethylene terephthalate resin comprising repeating units of terephthalic acid residue and repeating units of ethylene glycol residue linked by ester bonds which process comprises: depolymerizing polyethylene terephthalate resin with excess superheated stem in a pool containing molten resins under conditions suitable for hydrolysis of ester bonds to form a reaction mixture containing terephthalic acid, ethylene glycol, impurities and other components of the resins; vaporizing from the reaction mixture the terephthalic acid, ethylene glycol, and other volatile products of hydrolysis with excess superheated stem to obtain a continuous effluent of depolymerization comprising terephthalic acid, ethylene glycol, other volatile products of hydrolysis, and water in an mount of at least about 2 moles of water per mole of terephthalic acid in the effluent of depolymerization; separating from the effluent of depolymerization a, solid product of crude terephthalic acid substantially free of ethylene glycol, but containing organic impurities, to form an aqueous residue containing ethylene glycol; and fractionating at least a portion of the aqueous residue to obtain dehydrated ethylene glycol substantially free of lower boiling compounds, and a fraction containing lower boiling compounds.
Claim 17
Dependent Claim
188 words
A process for recovering terephthalic acid from polyethylene terephthalate resin comprising repeating units of terephthalic acid residue and repeating units of ethylene glycol residue linked by ester bonds which process comprises: depolymerizing polyethylene terephthalate resin with excess superheated stem in a pool containing molten resins under conditions suitable for hydrolysis of ester bonds to form a reaction mixture containing terephthalic acid, ethylene glycol, impurities and other components of the resins; vaporizing from the reaction mixture the terephthalic acid, ethylene glycol, and other volatile products of hydrolysis with excess superheated stem to obtain a continuous effluent of depolymerization comprising terephthalic acid, ethylene glycol, other volatile products of hydrolysis, and water in an mount of at least about 2 moles of water per mole of terephthalic acid in the effluent of depolymerization; separating from the effluent of depolymerization a, solid product of crude terephthalic acid substantially free of ethylene glycol, but containing organic impurities, to form an aqueous residue containing ethylene glycol; and fractionating at least a portion of the aqueous residue to obtain dehydrated ethylene glycol substantially free of lower boiling compounds, and a fraction containing lower boiling compounds.
Claim 18
Dependent Claim
38 words
The process according to claim 14 wherein the depolymerization of polyester resin is carried out in the presence of at least a portion of the fraction containing lower boiling compounds in one or more of the reaction zones.
Claim 19
Dependent Claim
87 words
The process according to claim 14 wherein the process further comprises: reducing at least a portion of the organic impurities in the crude terephthalic acid in an aqueous solution at elevated temperatures and pressures and in the presence of hydrogen and an insoluble catalyst containing a palladium component on a carbon support; separating the insoluble catalyst from the aqueous solution; and crystallizing and separating purified terephthalic acid from the aqueous solution while maintaining the temperature in a rage of from about 50° C. to about 150° C.
Claim 20
Dependent Claim
50 words
The process according to claim 16 wherein the resulting purified terephthalic acid has a L*-value in a range of from about 95 to about 100, an a*-value in a rage of from about -1 to about +1, and a b*-value in a rage of from about 0.5 to about 2.
Claim 21
Dependent Claim
227 words
A process for recovering 2,6-naphthalene dicarboxylic acid from poly(ethylene-2,6-naphthalate) resin comprising repeating units of 2,6-naphthalene dicarboxylic acid residue and repeating units of ethylene glycol residue linked by ester bonds which process comprises: depolymerizing from poly(ethylene-2,6-naphthalate) resin with excess superheated steam in a pool containing molten resins under conditions suitable for hydrolysis of ester bonds to form a reaction mixture containing g 2,6-naphthalene dicarboxylic acid, ethylene glycol, impurities and other components of the resins; vaporizing from the reaction mixture the 2,6-naphthalene dicarboxylic acid, ethylene glycol, and other volatile products of hydrolysis with excess superheated steam to obtain a continuous effluent of depolymerization comprising 2,6-naphthalene dicarboxylic acid, ethylene glycol, other volatile products of hydrolysis, and water in an amount of at least about 2 moles of water per mole of 2,6-naphthalene dicarboxylic acid in the effluent of depolymerization; separating from the effluent of depolymerization a solid product of crude 2,6-naphthalene dicarboxylic acid substantially free of ethylene glycol, but containing organic impurities, to form an aqueous residue containing ethylene glycol; and fractionating at least a portion of the aqueous residue to obtain dehydrated ethylene glycol substantially free of lower boiling compounds, and a fraction containing lower boiling compounds: wherein the depolymerization of poly(ethylene-2,6-naphthalate) resin is carried out in the presence of at least a portion of the fraction containing lower boiling compounds in one or more of the reaction zones.
Claim 22
Dependent Claim
227 words
A process for recovering 2,6-naphthalene dicarboxylic acid from poly(ethylene-2,6-naphthalate) resin comprising repeating units of 2,6-naphthalene dicarboxylic acid residue and repeating units of ethylene glycol residue linked by ester bonds which process comprises: depolymerizing from poly(ethylene-2,6-naphthalate) resin with excess superheated steam in a pool containing molten resins under conditions suitable for hydrolysis of ester bonds to form a reaction mixture containing g 2,6-naphthalene dicarboxylic acid, ethylene glycol, impurities and other components of the resins; vaporizing from the reaction mixture the 2,6-naphthalene dicarboxylic acid, ethylene glycol, and other volatile products of hydrolysis with excess superheated steam to obtain a continuous effluent of depolymerization comprising 2,6-naphthalene dicarboxylic acid, ethylene glycol, other volatile products of hydrolysis, and water in an amount of at least about 2 moles of water per mole of 2,6-naphthalene dicarboxylic acid in the effluent of depolymerization; separating from the effluent of depolymerization a solid product of crude 2,6-naphthalene dicarboxylic acid substantially free of ethylene glycol, but containing organic impurities, to form an aqueous residue containing ethylene glycol; and fractionating at least a portion of the aqueous residue to obtain dehydrated ethylene glycol substantially free of lower boiling compounds, and a fraction containing lower boiling compounds: wherein the depolymerization of poly(ethylene-2,6-naphthalate) resin is carried out in the presence of at least a portion of the fraction containing lower boiling compounds in one or more of the reaction zones.
Claim 23
Dependent Claim
87 words
The process according to claim 18 wherein the process further comprises: reducing at least a portion of the organic impurities in the crude 2,6-naphthalene dicarboxylic acid in an aqueous solution at elevated temperatures and pressures and in the presence of hydrogen and at least one insoluble Group VIII noble metal-containing catalyst; separating the insoluble catalyst from the aqueous solution; and crystallizing and separating purified 2,6-naphthalene dicarboxylic acid from the aqueous solution while maintaining the temperature in a range of from about 50° C. to about 250° C.
Claim 24
Dependent Claim
54 words
The process according to claim 18 wherein the purified 2,6-naphthalene dicarboxylic acid has an optical density in a range from about 0 to about 5, an ash content of less 200 ppm, while maintaining the aqueous solution during the reduction at temperatures in a range of from about 100° C. to about 250° C.
References Cited (Backward Citations)
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