Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-08-22
2001-11-13
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S424000, C562S467000, C562S468000, C562S425000
Reexamination Certificate
active
06316665
ABSTRACT:
FIELD OF INVENTION
This invention relates to the production of valuable diacids, such as terephthalic acid and 2,6-naphthalene dicarboxylic acid, by a novel reaction, the conversion of a phenolic compound, such as phenol or naphthol, to terephthalic acid or naphthalene dicarboxylic acid, respectively, by the action of high temperature and base. This invention provides a novel non-oxidative route from a low cost raw material to very valuable products that are of exceptionally high purity.
BACKGROUND OF THE INVENTION
It is well known in the art that aromatic carboxylic acids, as the potassium salts, can be isomerized or disproportionated via the Henkel reaction to form aromatic para substituted diacids. In this way, phthalic acid salts or benzoic salts, for example, can be made into terephthalic acid salts (TPA salts) and naphthoic acid salts or other isomers of naphthalene dicarboxylic acid (NDA) may be made into 2,6-naphthalene dicarboxylic acid (2,6-NDA). These compounds are often used as monomers for the preparation of polymeric materials. 2,6-naphthalene dicarboxylic acid (2,6-NDA) is a particularly useful aromatic carboxylic acid, because it can be reacted with ethylene glycol to prepare poly(ethylene-2,6-naphthalate), PEN.
The reaction of phenol with base to form salicylic acid at ca. 150-200° C. with a Na
+
counter ion by the addition of CO
2
, or parahydroxy benzoic acid at high temperature(225-300° C. with K
+
counter ion) is known in the literature, but it has never been observed that terephthalic acid (TPA) could be produced by either reaction. Neither has anything been found in the art to suggest that phenols could be useful to the Henkel reaction.
There is nothing found in the art to suggest that terephthalic acid could be produced directly from phenol, or that naphthalene dicarboxylic acid could be produced directly from naphthol. It would be of great value in the art if reactions such as this were possible, because phenol and naphthol are quite inexpensive as raw materials. Phenol can be prepared extremely inexpensively, at about one-third the cost of benzoic acid. Likewise, naphthol is readily available from naphthalene, for example by sulfonation or sulfation followed by hydrolysis, without the use of the oxidation reactions needed to form naphthalene dicarboxylic acid or naphthoic acid from hydrocarbons.
In addition, it would be very advantageous if a reaction to produce valuable diacids could be carried out without an oxidation step. A process that does not require oxidation could obviate the necessity of air separation plants, thus lessening the required scale for economic feasibility. It would be very desirable if there were a safe, oxidation-free route from common precursors, such as phenolic compounds, to desired diacid monomers for polyesters.
In the present invention, we have discovered a novel reaction comprising the conversion of phenolic compounds to diacids by the action of high temperature and base. Since the diacid products are of exceptionally high quality, the process is therefore a convenient way to make a high value product from a low cost raw material by a non-oxidative route.
SUMMARY
In accordance with the foregoing the present invention comprises an oxidation free process for converting a hydroxy substituted aromatic, or salt thereof, to an aromatic diacid which comprises reacting said hydroxy substituted aromatic with excess base in the presence of carbon dioxide at disproportionation/isomerization reaction conditions.
In a preferred embodiment, for example, an alkali metal salt of phenol is heated with excess potassium carbonate base in the presence of a disproportionation catalyst at a temperature in the range of 400-500° C. and a carbon dioxide pressure of 100 to 500 psig for 1-3 hours.
DETAILED DESCRIPTION OF THE INVENTION
The process of the present invention comprises heating an aromatic hydroxy compound, preferably a phenolic compound or an alkaline metal or alkaline earth metal salt of a phenolic compound, with excess base, such as, for example, potassium carbonate, or Group IB or IIB salts, in the presence of at least an atmosphere of carbon dioxide at temperatures above about 350° C., and optionally in the presence of a metal catalyst. Other basic salts, such as, for example an oxalate, may further increase the rate of reaction, but may also add to the cost, and are not critical.
Instead of an oxidative process, this process involves the direct addition of carbon dioxide to the aromatic groups. Thus, almost one-half the weight of the product comes from carbon dioxide (at 0.5 cpp) while about one-half the weight comes from the hydroxy substituted aromatic, for example, phenol, at 15-25 cpp. Therefore, the present invention represents a low raw material cost, non-oxidative route to exceptionally high purity terephthalic acid.
The basic process is applicable to a broad range of aromatics since the reaction site involves the hydroxyl group bonded to a benzene ring. The rest of the hydroxy aromatic can be anything as long as it does not contain other substituents which would interfere with the course of the reaction, for example, by reacting with the carbon dioxide. The aryl portion of the molecule may be a mono-, di- or tri-nuclear radical, or for that matter, can contain even more aryl groups. The aryl portion of the hydroxy aromatic may also be fused to other cyclic systems including heterocyclic systems, such as those containing cyclo oxygen, nitrogen and sulfur rings. For example, the hydroxy aromatic can be any of the isomeric hydroxysubstituted derivatives of benzene, naphthalene, anthracene, phenanthrene, indene, isoindene, benzofuran, isobenzofuran, indole, 1,2-benzopyran, quinoline, isoquinoline, acenaphthene, fluorene, dibenzopyrrole, xanthene, thianthrene, naphthacene, chrysene, pyrene, triphenylene, and the like, wherein the hydroxyl group is bonded to a nuclear carbon atom.
The process is also applicable to aryl hydroxy compounds having more than one hydroxyl radical bonded to a nuclear aromatic carbon atom. For example, the process can be applied to such polyhydroxy aromatics such as hydroquinones, resorcinols, catechols, 1,3-dihydroxy naphthalenes, pyrogallols, phloroglucinols, and the like.
Substituents other than hydroxyl groups may be present in the aromatic compounds as long as they do not interfere with the course of the reaction. That is to say, the other substituents should be relatively inert to carbon dioxide and should not act to poison the catalyst. For example, any of the previously-listed aromatics may be substituted in a variety of positions with alkyl radicals, aralkyl radicals, cycloalkyl radicals, and the like.
The reaction proceeds very satisfactorily when the hydroxy aromatic is phenol or naphthol. It is advantageous to use the hydroxy-containing aromatics in the form of an alkali metal salt. Preferably the potassium salts or the sodium salts are used. The rubidium and cesium salts, may be used, but generally are not for reasons of economy. It is also possible to use mixtures of salts of two different metals. Reaction materials that form the above-mentioned salts may also be used.
Suitable bases include carbonates, oxalates, hydroxides, formates, peroxides, oxides, and related materials. Preferred bases are alkali metal carbonates and bicarbonates. The alkali metal can be selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, but is preferably potassium. Bases which can be used to provide the excess include, but are not limited to, K
2
CO
3
, KHCO
3
, Rb
2
CO
3
, RbHCO
3
, Cs
2
CO
3
, CsHCO
3
, and other strongly basic carbonates or bicarbonates. We have found it advantageous to use potassium carbonate or potassium bicarbonate. Potassium hydroxide will work, but for the purposes of the present invention, carbonates and bicarbonates are preferred.
An excess of base is an important element of the present invention. An excess of base to hydroxy substituted aromatic in the range of 0.01 to 10.00 is within the inventive concept. The benefits of the excess base
Brownscombe Thomas Fairchild
Mysore Narayana
Pfrehm Susan Secor
Vaporciyan Garo
Geist Gary
Muller Kim
Reyes Hector M
Shell Oil Company
LandOfFree
Process for producing diacids by carboxylation of phenolic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing diacids by carboxylation of phenolic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing diacids by carboxylation of phenolic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2588699