Synthetic resins or natural rubbers -- part of the class 520 ser – Redox catalyst
Reexamination Certificate
2000-08-24
2001-11-13
Padmanabhan, Sreeni (Department: 1621)
Synthetic resins or natural rubbers -- part of the class 520 ser
Redox catalyst
C568S867000
Reexamination Certificate
active
06316571
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the preparation of alkylene glycols by reacting an alkylene oxide with water in the presence of a catalytic composition.
BACKGROUND OF THE INVENTION
Alkylene glycols, in particular monoalkylene glycols, are of established commercial interest. For example, monoalkylene glycols are being used in anti-freeze compositions, as solvents and as base materials in the production of polyalkyene terephthalates e.g. for fibres or bottles.
The production of alkylene glycols by liquid phase hydrolysis of alkylene oxide is known. The hydrolysis is performed without a catalyst by adding a large excess of water, e.g. 20 to 25 moles of water per mole of alkylene oxide, or it is performed with a smaller excess of water in a catalytic system. The reaction is considered to be a nucleophilic substitution reaction, whereby opening of the alkylene oxide ring occurs, water acting as the nucleophile. Because the primarily formed monoalkylene glycol also acts as a nucleophile, as a rule a mixture of monoalkylene glycol, dialkylene glycol and higher alkylene glycols is formed. In order to increase the selectivity to monoalkylene glycol, it is necessary to suppress the secondary reaction between the primary product and the alkylene oxide, which competes with the hydrolysis of the alkylene oxide.
One effective means for suppressing the secondary reaction is to increase the relative amount of water present in the reaction mixture. Although this measure improves the selectivity towards the production of the monoalkylene glycol, it creates a problem in that large amounts of water have to be removed for recovering the product.
Considerable efforts have been made to find an alternative for increasing the reaction selectivity without having to use a large excess of water. Usually these efforts have focused on the selection of more active hydrolysis catalysts and various catalysts have been disclosed.
Both acid and alkaline hydrolysis catalysts have been investigated, whereby it would appear that the use of acid catalysts enhances the reaction rate without significantly affecting the selectivity, whereas by using alkaline catalysts generally lower selectivities with respect to the monoalkylene glycol are obtained.
Certain anions, e.g. bicarbonate (hydrogen carbonate), bisulphite (hydrogen sulphite), formate and molybdate, are known to exhibit good catalytic activity in terms of alkylene oxide conversion and selectivity towards monoalkylene glycol. However when the salts of these anions are used as the catalyst in a homogeneous system, work-up of the reaction product by distillation will pose a problem because the salts are poorly soluble in the glycol and tend to make it semi-solid. Quaternary ammonium salts remain soluble in the glycol reaction product.
High conversions, good selectivity and a low water/alkylene oxide ratio can be obtained with the process, disclosed in EP-A 0 156 449 and EP-A 0 160 330 (both of Union Carbide). According to these documents the hydrolysis of alkylene oxides is carried out in the presence of a selectivity-enhancing metalate anion-containing material, preferably a solid having electropositive complexing sites having affinity for the metalate anions. The said solid is preferably an anion exchange resin, in particular a styrene-divinyl benzene copolymer. The electropositive complexing sites are in particular quaternary ammonium, protonated tertiary amine or quaternary phosphonium. The metalate anions are specified as molybdate, tungstate, metavanadate, hydrogen pyrovanadate and pyrovanadate anions. A complication of this process is that the alkylene glycol-containing product stream also comprises a substantial amount of metalate anions, displaced from the electropositive complexing sites of the solid metalate anion containing material. In order to reduce the amount of metalate anions in the alkylene glycol product stream, this stream is contacted with a solid having electropositive complexing sites associated with anions which are replaceable by the said metalate anions.
In WO 95/20559, there is disclosed a process for the preparation of alkylene glycols wherein an alkylene oxide is reacted with water in the presence of a catalyst composition comprising a solid material having one or more electropositive sites, which are coordinated with one or more anions other than metalate or halogen anions, e.g. bicarbonate, bisulphite and carboxylate, with the proviso that when the solid material is an anionic exchange resin of the quaternary ammonium type and the anion is bicarbonate the process is performed in the substantial absence of carbon dioxide. According to this document, the presence of carbon dioxide in the feed is detrimental to the catalytic effect of bicarbonate-exchanged resins of the quaternary ammonium type.
A drawback shared by the conventional anionic exchange resins is their limited tolerance to heat. In practising the process of alkylene oxide hydrolysis according to WO 95/20559 with catalyst compositions based on conventional organic quaternary ammonium ion exchangers it has been found, that under severe alkylene oxide hydrolysis reaction conditions (high temperature and/or long service) the catalytic activity (selectivity and/or conversion) of the conventional resin-based catalysts tends to deteriorate. Moreover, under these reaction conditions these catalysts were found to undergo swelling.
In EP-A 226 799 there is disclosed a method for preparing ethylene glycol or propylene glycol by hydration of the respective oxide, in the presence of a dual composition catalyst consisting of a monobasic or polybasic carboxylic acid and a metal or ammonium salt of such a carboxylic acid.
SUMMARY OF THE INVENTION
The present invention relates to a process for the preparation of alkylene glycols by reacting an alkylene oxide with water in the presence of a catalytic composition including a polycarboxylic acid derivative, having in its chain molecule one or more carboxyl groups and one or more carboxylate groups, the individual carboxyl and/or carboxylate groups being separated from each other in the chain molecule by a separating group consisting of at least one atom.
Preferably the number of carboxylic groups in the molecule is at least equal to the number of carboxylate groups.
In a preferred embodiment of the present invention, the polycarboxylic acid derivative as defined above is immobilised on a solid support. Solid catalysts including such immobilised polycarboxylic acid derivatives are novel.
DETAILED DESCRIPTION OF THE INVENTION
The carboxylate groups may be metal salts such as alkali metal and earth alkali metal salts or ammonium salts. Preferably the carboxylates are alkali metal salts, most preferably sodium salts.
The separating group may comprise several atoms, which then may be arranged in a linear or branched chain or in a ring. Preferably the separating group consists of a single carbon atom.
Examples of dicarboxylic acid derivatives according to the invention are the monosodium salts of malonic acid, succinic acid, adipic acid, tartaric acid, maleic acid, terephthalic acid, malic acid, suberic acid, phthalic acid, isophthalic acid, quinolinic acid (2,3 pyridine dicarboxylic acid), isochinchomeronic acid (2,5 pyridine dicarboxylic acid), dipicolinic acid (2,6 pyridine dicarboxylic acid), chinchomeronic acid (3,4 pyridine dicarboxylic acid), dinicotinic acid (3,5 pyridine dicarboxylic acid), cyclohexene-1,2-dicarboxylic acid (3,4,5,6-tetrahydrophtalic acid) and isomers, cyclohexane-1,2-dicarboxylic acid (hexahydrophthalic acid) and isomers, cyclohexane-1,1-dicarboxylic acid, thiophene-2,5-dicarboxylic acid, chelidonic acid (4-oxo-4H-pyran-2,6-dicarboxylic acid), thiophene-3,4-dicarboxylic acid, etc.
Examples of uricarboxylic acid derivatives according to the invention are the monosodium salts of citric acid, trimellitic acid (1,2,4-benzenetricarboxylic acid), and trimesic acid (1,3,5-benzenetricarboxylic acid).
Examples of tetracarboxylic acid derivatives according to the invention are the monosodium
Davis Brian J.
Padmanabhan Sreeni
Shell Oil Company
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