Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2002-11-14
2004-12-07
Hopkins, Robert A (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S670000, C210S673000, C210S674000
Reexamination Certificate
active
06827858
ABSTRACT:
The present invention relates to a process for separating alkali metal ions from alkoxylates containing alkali metal ions, alkali metal-free alkoxylates and a process for the preparation of alkali metal-free alkoxylates.
Alkoxylates, in particular polyalkylene oxides and adducts of alkylene oxides with alcohols and/or alkylphenols, are usually prepared under alkali metal hydroxide catalysis. Depending on the intended use, it is frequently necessary to remove the catalyst as completely as possible from the adduct. This is the case, for example, with alkoxylates which are used as fuel additives or carrier oils in fuel additive packets or formulations. Such alkoxylates for carrier oils are in general adducts of propylene oxide and/or butylene oxide with alcohols and/or alkylphenols of more than 6 carbon atoms, which are prepared by catalysis using potassium hydroxide. In order to ensure substantially residue-free combustibility of the carrier oils, the catalyst must be separated off. In the conventional processes, this is done by neutralization and precipitation as acidic potassium phosphate and subsequent filtration. After the synthesis of the alkoxylates, also referred to here generally as polyethers, it is therefore necessary to neutralize the potassium alcoholate contained in the product with dilute phosphoric acid (stoichiometric amounts of phosphoric acid dissolved in about 10%, based on the reactor content, of water) and to distill off the water for crystallization of the acidic potassium phosphate. The reactor content must then be filtered, for example through a batchwise sheet filter, which is manually loaded and scraped off. Further required steps are the separation and separate packing of product-moist salt and impregnated filter sheets, their transport and incineration; the cleaning of the reactors before the subsequent batch, also in the case of a batch procedure, in order to remove remaining phosphate residues which neutralize marked amounts of catalyst and can thus delay or even suppress initiation of the oxyalkylation reaction; the drying of the reactors for the subsequent batch. It is clear that the removal of the catalyst is expensive. Moreover, the carrier oils thus obtained still contain small amounts of potassium and also phosphorus, so that residue-free combustion of the carrier oils is not possible.
It is an object of the present invention to provide alkoxylates which are substantially free of catalyst impurities from the preparation.
It is a further object of the present invention to provide a process for the preparation of alkoxylates which are substantially free of catalyst impurities from the preparation.
It is a further object of the present invention to provide a process for separating the catalyst from alkoxylates, which permits substantial removal of the catalyst from the product and preferably avoids contamination of the product with phosphate.
We have found that this object is achieved by the novel process for the separation of alkali metal ions from alkoxylates containing alkali metal ions (in particular potassium and sodium ions), which comprises the following steps:
a) dilution of the alkali metal-containing alkoxylate with an inert solvent,
b) treatment of the alkali metal-containing solution of the alkoxylate with a cation exchanger for exchanging alkali metal ions for hydrogen ions in order to obtain a substantially alkali metal-free solution of the alkoxylate, and
c) removal of the solvent from the substantially alkali metal-free solution of the alkoxylate in order to obtain a substantially alkali metal-free and substantially solvent-free alkoxylate.
In the novel process for the preparation of alkoxylates, the alkoxylates are initially prepared in a conventional manner, and the catalyst is then removed by the novel process for separating off alkali metal.
The term alkali metal-free or substantially alkali metal-free means that less than 5, preferably less than 1, ppm of alkali metal ions are present. The alkali metal-containing alkoxylate to be purified generally contains from 5 000 to 100, in particular from 2 000 to 1 000, ppm of alkali metal ions.
The term substantially solvent-free means that the alkoxylate contains <1 000, preferably <500, ppm of solvent.
The term alkoxylate includes pure substances as well as mixtures which are obtained using different alkylene oxides and/or different alcohols.
The term alkoxylate includes polyalkylene oxides (polyethers) and alcohol- and/or alkylphenol-initiated polyethers. The polyether or the polyether moiety of the alcohol- and/or alkylphenol-initiated polyethers is generally composed of at least one C
2
-C
6
-alkylene oxide, in particular ethylene oxide, propylene oxide, n-butylene oxide, 2,3-butylene oxide and/or isobutylene oxide. In general, at least one C
1
-C
50
-alkanol, preferably C
2
-C
20
-alkanol, particularly preferably C
6
-C
14
-alkanol, in particular 2-ethylhexanol, nonanol, isononanol, tridecanol, isotridecanol, etc., is used as the alcohol. The alkylphenol used is in general a C
1
-C
50
-alkylphenol, particularly preferably a C
6
-C
14
-alkylphenol, preferably a C
6
-C
14
-alkylphenol, in particular nonylphenol, octylphenol or dodecylphenol, or a di-C
1
-C
50
-alkylphenol.
Alkanol-initiated polyethers having from about 10 to 35, preferably from about 15 to 30, alkylene oxide units are preferred.
The preparation of alkoxylates is known per se. Polyether syntheses are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. 21, 1992, 579-589, and the publications stated therein. The preparation of alcohol- or alkylphenol-initiated polyethers is described, for example, in Ullmann's Enzyklopädie der technischen Chemie, 4th Edition, Volume 22, 491-492 and Volume 19, 31-33.
The catalyst-containing crude alkoxylate product is initially diluted with an inert solvent for removal of the catalyst. Solvents used are in general an aliphatic or cyclic ether, such as tert-butyl methyl ether, tetrahydrofuran or dioxane, a hydrocarbon, such as pentane, hexane, toluene or xylene, a ketone, such as acetone or methyl ethyl ketone, and preferably an alcohol, in particular a C
1
-C
4
-alkanol, such as ethanol, isopropanol, n-butanol, isobutanol and preferably methanol. For removal of the alkali metal catalyst, the dilute solution is treated with a cation exchanger, for example is passed through an exchanger bed, in particular in the form of a column, or is stirred with the cation exchanger. Particularly suitable cation exchangers are strongly acidic, macroporous resins, for example those based on crosslinked polystyrenes having sulfonic esters as functional groups.
The amount of cation exchanger required for removal of the catalyst is dependent on the catalyst content of the product to be treated and on the capacity of the ion exchanger used.
The solvent is then removed again, for example by distilling off. The removal is preferably effected in two steps. In a first step, the main amount of the solvent is removed, preferably by distilling off, an alkoxylate solution depleted of solvent and the solvent being obtained. In the first step, preferably at least 80% and up to 95% of the solvent are removed. In a second step, the remaining amount of the solvent is removed, preferably by stripping the depleted solution of the alkoxylate with inert gas in a column, in order to obtain a substantially alkali metal-free and substantially solvent-free alkoxylate and alcohol.
After a specific operating time, the cation exchanger needs to be regenerated. The regeneration is preferably integrated in the overall process, i.e. alkoxylate solution still contained in the cation exchanger is recovered before the regeneration and is recycled to stage c) or a) of the catalyst separation process. Any residues of the alkoxylate solution which still adhere to the cation exchanger are removed by washing with the inert solvent. The wash solvent is likewise recycled to stage a) of the catalyst separation process.
The regeneration of the cation exchanger preferably comprises the f
Bader Joachim
Bechtolsheimer Hans-Heinrich
Brucker Armin
Dockner Toni
Iffland Gabriele
BASF - Aktiengesellschaft
Hopkins Robert A
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