Process for the preparation of dialkyl esters of naphthalenedicarboxylic acids
AssigneeEastman Chemical Company
InventorThomas Michael Pell, Jr.
Life of this patent
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Abstract
Disclosed is a process for the production and purification of dialkyl naphthalenedicarboxylate compounds wherein a crude naphthalenediacarboxylic acid is esterified with an alkanol such as methanol to produce a crude esterification product comprising dialkyl naphthalenedicarboxylate, starting materials and other compounds and the crude esterification product is purified by flash distillation to remove impurities which can cause fouling of conventional distillation equipment. A particularly useful diester is dimethyl 2,6-naphthalenedicarboxylate.
Claims6
Process for the manufacture of a dialkyl ester of a naphthalenedicarboxylic acid (NDC) which comprises the steps of:
- (1) feeding a lower alkanol and a naphthalenedicarboxylic acid (NDA) to an esterification zone which is maintained at a temperature of about 200 to 350° C. to obtain a crude esterification product comprising lower alkanol, water, NDC, monoalkyl ester of naphthalenedicarboxylic acid (MHN), NDA, trialkyl trimellitate (TATM) and catalyst residues;
- (2) removing liquid and vapor streams comprising crude esterification product from the esterification zone;
- (3) reducing the pressure of the liquid and vapor streams of step (2) and feeding the streams to the lower section of a primary flash distillation column to produce (i) an overhead vapor stream rich in the NDC, alkanol and water and (ii) column base underflow stream rich in NDA, MHN and NDC;
- (4) recycling a major portion of the underflow stream of step (3) to the esterification zone;
- (5) feeding a minor portion of the underflow stream of step (3) to a secondary flash vessel to produce a (i) vapor stream comprising NDC, MHN and NDA and (ii) liquid residue stream comprising TATM, catalyst residues, NDC, MHN and NDA;
- (6) feeding the overhead vapor stream from step (3) and the vapor stream from step (5) to the mid-section of a distillation column to obtain (i) an overhead vapor stream rich in alkanol and water and (ii) a column base underflow stream rich in NDC and essentially devoid of alkanol and water;
- wherein all of the heat for the primary flash distillation column and the secondary flash vessel is provided by the heat of the streams fed to the column and vessel.
Process for the manufacture of a dimethyl of 2,6-naphthalenedicarboxylic acid (2,6-NDC) which comprises the steps of:
- (1) feeding methanol and 2,6-naphthalenedicarboxylic acid (2,6-NDA) to an esterification zone which is maintained at a temperature of about 250 to 320° C. and a pressure of about atmospheric to 55 bar gauge to obtain a crude esterification product comprising lower alkanol, water, 2,6-NDC, monomethyl ester of 2,6-naphthalenedicarboxylic acid (2,6-MHN), 2,6-NDA, trimethyl trimellitate (TMTM) and catalyst residues;
- (2) removing liquid and vapor streams comprising crude esterification product from the esterification zone;
- (3) reducing the pressure of the liquid and vapor streams of step (2) and feeding the streams to the lower section of a primary flash distillation column to produce (i) an overhead vapor stream rich in the 2,6-NDC, methanol and water and (ii) column base underflow stream rich in 2,6-NDA, 2,6-MHN and 2,5-NDC;
- (4) recycling a major portion of the underflow stream of step (3) to the esterification zone;
- (5) feeding a minor portion of the underflow stream of step (3) to a secondary flash vessel to produce a (i) vapor stream comprising 2,6-NDC, 2,6-MHN and 2,6-NDA and (ii) liquid residue stream comprising TMTM, catalyst residues, 2,6-NDC, 2,6-MHN and 2,6-NDA;
- (6) feeding the overhead vapor stream from step (3) and the vapor stream from step (5) to the mid-section of a distillation column to obtain (i) an overhead vapor stream rich in methanol and water and (ii) a column base underflow stream rich in 2,6-NDC and essentially devoid of methanol and water;
- wherein all of the heat for the primary flash distillation column and the secondary flash vessel is provided by the heat of the streams fed to the column and vessel.
Dependencies are inferred from the claim text.