WO2000051956A1 - Method of preparing alkoxylated compounds with active hydrogen atoms - Google Patents

Abstract

The invention relates to a method of preparing alkoxylated compounds with active hydrogen atoms. According to said method the catalyst is a mixture of possibly modified hydrotalcite and co-catalysts which are selected from the group of hydroxides, oxides and/or alkoxides of alkali and/or alkaline-earth metals, alkaline and/or alkaline-earth salts, tin salts and mixed metal oxides.

Description

"Process for the production of alkoxylated compounds with active hydrogen atoms"

The invention relates to a process for the preparation of alkoxylated compounds with active hydrogen atoms, in which compounds with active hydrogen atoms are reacted with alkylene oxides in the presence of optionally modified hydrotalcite as a catalyst and selected co-catalysts.

An important group of nonionic surfactants is the addition products of alkylene oxides, in particular ethylene oxide and / or propylene oxide, to compounds with active hydrogen, which are usually prepared by means of homogeneous catalysis in the presence of alkali metal hydroxides or alkali metal alcoholates. Products with a broad homolog distribution are obtained by the homogeneously catalyzed process.

Products with a restricted homolog distribution can be obtained if the reaction is carried out in the presence of possibly modified hydrotalcites, for example in accordance with German Offenlegungsschrift DE-A-3833076. The catalyst hydrotalcite is, however, quite expensive due to the complex production process, so that the alkoxylation of the compounds with active hydrogen is associated with considerable costs.

The object of the present invention was therefore to provide a process for the preparation of alkoxylated compounds with active hydrogen atoms, which leads on the one hand to products with a restricted homolog distribution, but on the other hand is associated with lower costs.

Surprisingly, the object of the present invention could be achieved if the hydrotalcite which may have been modified is at least partially replaced by specially selected cocatalysts. The invention includes the finding that such a catalyst mixture also provides products with a restricted homolgen distribution which agrees very well with the homolog distribution of the alkoxylation catalyzed by only hydrotalcite. In addition, the total amount of catalyst can be reduced compared to the prior art. Finally, significantly shorter reaction times for the alkoxylation can be achieved when using the catalyst mixtures according to the invention. In the following, the term “catalytic mixture” is understood to mean a mixture of possibly modified hydrotalcite and the selected cocatalysts.

An object of the present invention therefore relates to a process for the preparation of alkoxylated compounds with active hydrogen atoms by reacting compounds with active hydrogen atoms with alkylene oxides in the presence of optionally modified hydrotalcite as a catalyst, characterized in that cocatalysts selected from the group are used Group formed by hydroxides, oxides and / or alkoxides of alkali and / or alkaline earth metals as well as alkali and / or alkaline earth salts, tin salts and mixed metal oxides.

The following classes of substances are suitable as compounds with active hydrogen atoms:

al) alcohols with 6 to 22 carbon atoms (so-called fatty alcohols), such as Cappa alcohol, caprylic alcohol, capric alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol, petroselinyl alcohol, linolyl alcohol, linolenyl alcohol, ricinolyl alcohol, eraducyl alcohol alcohol, elaeostol alcohol, elaeostol alcohol as they occur, for example, in the hydrogenation of methyl ester fractions of native origin or of aldehydes from Roelen's oxosynthesis. Fatty alcohols with 12 to 18 carbon atoms are preferred, for example technical coconut or tallow fatty alcohol strains.

The so-called Guerbet alcohols, which are produced by alkali-catalyzed condensation of 2 moles of fatty alcohol and which can contain 12 to 36 carbon atoms, are also suitable as a further group of fatty alcohols.

a2) carboxylic acids with 6 to 22 carbon atoms (so-called fatty acids) and hydroxy fatty acids, such as, for example, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, palmoleic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, petroselinic acid, linoleic acid, linolenic acid , Elaeostearic acid, arachic acid, gadoleic acid, behenic acid and erucic acid and their technical mixtures, such as those used in the pressure splitting of natural fats and oils occur. Fatty acids with 12 to 18 carbon atoms, for example technical coconut or tallow fatty acids, are preferred.

a3) alkylphenols, polyglycols, fatty amines, vicinal hydroxy / alkoxy-substituted alkanes, which can be obtained, for example, by ring opening of epoxy compounds with alcohols or carboxylic acids, and secondary alcohols.

Within the group of compounds with active hydrogen atoms, the alcohols or carboxylic acids with 6 to 22 carbon atoms are preferred.

In the process according to the invention, optionally modified hydrotalcites in combination with specially selected cocatalysts are used as alkoxylation catalysts.

The modified hydrotalcites used are calcined or hydrophobized hydrotalcites, as are known, for example, from German patent applications DE-Al 38 43 713 and DE-Al 40 10 606 (Henkel). The calcined hydrotalcites are particularly preferred.

Suitable co-catalysts are compounds from the group formed by hydroxides, oxides and / or alkoxides of alkali and / or alkaline earth metals and of alkali and / or alkaline earth metal salts, tin salts and mixed metal oxides.

Particularly suitable hydroxides of alkali and / or alkaline earth hydroxides are lithium hydroxide and / or magnesium hydroxide.

Within the group of oxides of alkali and / or alkaline earth oxides, the oxides of magnesium are preferred.

Preferred alkoxides of the alkali and / or alkaline earth metals are those which are derived from short-chain alcohols, for example from those having 1 to 8 carbon atoms and in particular from methanol, ethanol and / or 2-ethylhexanol. The magnesium and / or barium compounds are particularly preferred. Within the group of alkali and / or alkaline earth salts, the magnesium and barium salts, for example the carbonates such as magnesium carbonate, or the acetates, for example magnesium acetate, are of particular importance.

Mixed metal oxides are oxide compounds that contain at least two different metals. One of the metals is preferably magnesium. The other metal can be aluminum, gallium, zircon, indium, thallium, cobalt, scandium, lanthanum and / or manganese. Magnesium / aluminum mixed oxides are particularly preferred. The surface of the mixed oxides can be modified with one or more of the co-catalysts already mentioned, in particular with the hydroxides and / or alkoxides of the alkali and / or alkaline earth metals.

Magnesium oxide is particularly preferred as co-catalyst.

The optionally modified hydrotalcites can be present in amounts of from 0.01 to 5, preferably from 0.05 to 0.5 and in particular from 0.05 to 0.2% by weight, based on the starting compounds (compounds with active hydrogen atoms and alkylene oxide). - be used.

The cocatalysts can be used in amounts of 0.01 to 5, preferably in amounts of 0.05 to 0.5 and in particular in amounts of 0.1 to 0.3% by weight, based on the starting compounds.

Because of the synergistic effect in the activity as a catalyst between possibly modified hydrotalcite and the cocatalysts, it is even possible in the sense of the present invention to reduce the total amount of catalyst compared to the known prior art. For example, about 0.5 to 1% by weight of optionally modified hydrotalcite is usually used for the alkoxylation of compounds with active hydrogens. According to a particularly preferred embodiment of the present invention, even with a total content of catalysts including cocatalysts below 0.5% by weight, preferably between 0.1 and 0.4 and in particular between 0.2 and 0.3% by weight, very good results can be achieved in relation to the starting compounds.

The ratio between possibly modified hydrotalcite as catalyst and co-catalysts can vary within wide ranges, preferably the weight ratio is between 5: 1 to 1: 5, in particular between 3: 1 and 1: 3 and particularly preferably between 2: 1 and 1 : 2. The reaction of the compounds with active hydrogen atoms with the alkylene oxides can be carried out in a manner known per se at temperatures from 120 to 200, preferably 150 to 180 ° C. and pressures of 1 to 5 bar. The amount of alkylene oxide to be added is not critical and can be, for example, 1 to 100, preferably 2 to 50 and in particular 2 to 20 moles of alkylene oxide per mole of active hydrogen in the compound.

As alkylene oxides, ethylene, propylene and / or butylene oxide can be used, preferably ethylene oxide.

After the actual alkoxylation, at least equimolar amounts of acids - based on the catalyst mixture (hydrotalcite and cocatalyst) - can be added in the process according to the invention in order to decompose the catalyst mixture as completely as possible.

Both inorganic and organic acids can be added as acids. Mineral acids such as sulfuric acid, hydrochloric acid and / or phosphoric acid are particularly suitable as inorganic acids. Organic acids include both the so-called fatty acids with 6 to 22 carbon atoms and lower carboxylic acids with 1 to 4 carbon atoms (only the carbon atoms of the hydrocarbon structure are counted, not the carbon atoms of the carboxyl groups), which may have been additionally modified with hydroxyl groups can, used. The lower carboxylic acids such as lactic acid, acetic acid and / or citric acid are preferred as acids.

As a rule, the acids are added as aqueous solutions, preferably as 10 to 90% by weight solutions.

According to the invention, the acids are used at least in equimolar amounts, based on hydrotalcite, preferably in molar amounts, in relation to the amount of catalyst, from 1: 1 to 10: 1, in particular from 1: 1 to 4: 1.

It has proven to be advantageous in the context of the invention if the acids are added at temperatures above the melting point of the alkoxylated compounds, preferably at temperatures between 70 and 95 ° C. In practice, this is best done carried out that after the alkoxylation, the reaction mixture obtained in this

Holds temperatures and admits the acid. The addition of acid ensures that the catalyst mixture decomposes. The decomposition products prove to be water-soluble and do not lead to clouding or sedimentation of the alkoxylated compounds.

If desired, the catalyst can of course be worked up in the usual way, for example by means of filtration, instead of the acid treatment.

The alkoxylated compounds obtained by the processes according to the invention have a narrow homolog distribution and can be used without problems as a nonionic surfactant for the production of washing, rinsing and cleaning agents.

example 1

638.3 g (corresponding to 3.3 mol) of a C12 / 14 fatty alcohol mixture (approximately 70% by weight of C12 alcohol and approximately 30% by weight of C14 alcohol) were mixed with 1.0 g (corresponding to 0.1% by weight). % based on starting compounds) calcined hydrotalcite and 2.0 g magnesium oxide (corresponding to 0.2% by weight - based on starting compounds) in a pressure vessel. The container was evacuated at 100 ° C for 30 minutes and then vented with nitrogen. At max. 180 ° C and max. 5 bar pressure, 361.7 g (corresponding to 8.2 mol) of ethylene oxide were added in portions. The reaction time was 70 minutes. After the alkoxylation had ended, the reaction was continued at 120 ° C. for one hour and the apparatus was evacuated again at 120 ° C. for 30 minutes.

An ethoxylated C 12/14 fatty alcohol with a hydroxyl number of 179 was obtained.

Comparative Example 1

The alkoxylation is carried out analogously to Example 1, but with 5.0 g (corresponding to 0.5% by weight, based on the starting compounds) of hydrotalcite as a catalyst. The reaction time was 120 minutes. The product had a hydroxyl number of 182. The homolog distributions of the two products are comparable.

The examples show that comparable products require higher amounts of catalyst if only hydrotalcite is used (comparative example). Low amounts of catalyst are sufficient in the process according to the invention. In addition, the reaction time is shorter in the method according to the invention.

Claims

claims 1. A process for the preparation of alkoxylated compounds with active hydrogen atoms by reacting compounds with active hydrogen atoms with alkylene oxides in the presence of optionally modified hydrotalcite as a catalyst, characterized in that co-catalysts are used which are selected from the group formed by Hydroxides, oxides and / or alkoxides of alkali and / or alkaline earth metals and of alkali and / or alkaline earth metal salts, tin salts and mixed metal oxides. 2. The method according to claim 1, characterized in that alcohols or carboxylic acids having 6 to 22 carbon atoms are used as compounds with active hydrogen. 3. The method according to any one of claims 1 to 2, characterized in that lithium hydroxide and / or magnesium hydroxide are used as co-catalysts. 4. The method according to any one of claims 1 to 2, characterized in that magnesium oxide is used as cocatalyst. 5. The method according to any one of claims 1 to 2, characterized in that alkoxides of alcohols having up to 8 carbon atoms, in particular of magnesium and / or barium, are used as co-catalysts. 6. The method according to any one of claims 1 to 2, characterized in that mixed metal oxides with magnesium are used as co-catalysts. 7. The method according to any one of claims 1 to 6, characterized in that the optionally modified hydrotalcites in amounts of 0.05 to 0.5 wt.% - Based on the starting compounds - are used. 8. The method according to any one of claims 1 to 7, characterized in that the cocatalysts are used in amounts of 0.05 to 0.5% by weight, based on the starting compounds. . Process according to one of claims 1 to 8, characterized in that modified hydrotalcite and cocatalysts with a total content of less than 0.5% by weight, based on the starting compounds, are used. 10. The method according to any one of claims 1 to 9, characterized in that, after the alkoxylation, the catalysts are decomposed by adding acids.