DE2049162A1 - Process for the preparation of alkoxy and acyloxy acetaldehydes - Google Patents

Description

Badische Anilin- & Soda-Fabrik AG 2049162

Our symbols: O.Z. 27 065 Hee / Fe 6700 Ludwigshafen, October 6, 1970

Process for the preparation of alkoxy and aoyloxyacetaldehyde p

Alkoxy and acyloxyacetaldehydes can be catalytically ^ Produce dehydration from the corresponding alcohols. According to this from the USA patents 2,000 6O4, 2 I70 and 2 286 034 "known production method, however, even with good conversions, mostly only very moderate yields obtain.

It has now been found that alkoxy and Acyloxyacetaldehyde can produce greatly advantageous by catalytic dehydrogenation of the corresponding alkoxy and Acyloxyäthanole at a higher temperature when the dehydrogenation is carried out at temperatures of 150 to 350 ⁰ C in the presence of basic nitrogen compounds.

As starting materials, for example, the alkoxy and acyloxyethanols of the formula RO-GH ₂ -CH ₂ -OH, in which R is an alkyl radical with 1 to 6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl , Isobutyl or pentyl radical or an acyl radical, such as a formyl, acetyl, propionyl or butyryl radical. The following compounds may be mentioned in detail, for example:

Ethylene glycol monomethyl ether, ethyl ether, propyl ether, isopropyl ether, butyl ether and ethylene glycol monoformate, acetate, propionate, butyrate and isobutyrate. These alcohols are easily accessible by reacting ethylene oxide with the corresponding alcohols or carboxylic acids.

Suitable dehydrogenation catalysts are, for example, metals and alloys of the subgroup elements, such as Zinc, cadmium, platinum, palladium, chromium, manganese, iron, nickel, cobalt, alloys of zinc with iron or silver,

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but preferably copper, silver and brass. Particularly gate results are achieved when using catalysts which, in addition to the metals mentioned, also contain basic metal oxides such as manganese oxide, zinc oxide, cadmium oxide and, in particular, magnesium oxide. Additions of acidic oxides, such as silicon dioxide, aluminum oxide, chromium oxide and iron oxide, are not recommended, since they can give rise to undesired cleavage and side reactions. The mixing ratio between the metals and metal oxides mentioned in the catalyst mass can vary within wide limits. It is part of the range from 5 to 95 to 45 to 55 percent by weight. The catalyst is suitably used in the form of tablets, preferably 4 to 5 mm diameter or W in the form of powder.

According to the process of the invention, the dehydration made in the presence of basic nitrogen compounds. Such compounds include ammonia or organic, such as aliphatic or aromatic nitrogen compounds, of which, for example, allylamines with alkyl radicals, which contain 1 to 8 carbon atoms, such as methylamine, Ethylamine, dimethylamine, trimethylamine or aniline should be mentioned. There are also weakly basic nitrogen compounds, such as urotropine or azomethine into consideration, z. B. those azomethines, which consist of the amines mentioned and Carbonyl compounds, in particular the aldehydes expected as process products, are formed. Preferred are ammonia, urotropine and alkylamines with alkyl groups, containing 1 to 8 carbon atoms.

The amount of nitrogen compound to be used depends on its basicity and the properties of the one to be dehydrated Alcohols. In general, the basic nitrogen compounds are used in proportions of 0.1 to 5 percent by weight, preferably from 0.5 to 1 percent by weight, based on the starting material.

The inventive method is carried out, for example, by the alcohol to be dehydrated in the

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Passes vapor phase over a catalyst bed. The preferred temperature range is between 200 and 300 ⁰ O.

The residence times at the contact are generally 0.06 to 60 seconds, preferably 0.2 to 1 second.

In many cases it has proven to be useful with the addition of inert gases such as carbon dioxide, stick__ substance, argon or volatile hydrocarbons at atmospheric pressure or under reduced pressure, e.g. B. 10 to 500 torr, preferably 20 to 200 torr. In most cases it is advantageous to supply water up to a content of 20 to 90% by volume of water vapor in the reaction space. It can also occur in the presence of oxygen or of oxygen-containing substances in the reaction chamber, if the appropriate precautionary measure get noticed. The conditions are expediently adapted to the sensitivity of the substance to be dehydrated. Dwell time The contact and the reaction temperature are coordinated so that no decomposition of the product entry. The optimal conditions can be determined from case to case by means of a preliminary experiment. Very good results bring about dehydrogenations in a catalyst fluidized bed.

If a strongly basic nitrogen compound, such as trimethylamine, added, it is advisable to neutralize the reaction product immediately. When adding weakly basic nitrogen compounds, like aniline, this measure is not required.

The process can be either discontinuous or continuous be performed. The desired end products are isolated from the reaction mixture after known and customary methods.

The subject of the invention enriches the technology with the new possibility of alkoxy and acyloxyacetaldehydes after one

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with good conversions, very good yields and largely avoiding side reactions to produce processes.

This beneficial result is surprising. As disclosed in U.S. Patents 2,000,604, 2,170,854, and 2 286 034 it had to be assumed that additions of acidic oxides such as silicon dioxide, aluminum oxide, chromium oxide and iron oxide, are particularly favorable to the dehydration contact mass. It could therefore not be expected that significantly better results are obtained with the addition of basic substances,

The process products are valuable intermediate products, e.g. for the production of thermoplastic resins, DL-Serine and Aldotetroses.

The parts named in the following examples are, insofar as not otherwise noted, parts by weight; Parts of the room behave to them as liters to kilograms.

example 1

300 parts of ethylene glycol monomethyl ether (boiling point _{6 ()} : 125 ⁰ O), in which 3 parts of NH 3 are dissolved, are passed into a quartz tube at a pressure of 120 torr over 500 parts of a heated ^{to 260 0 O over a period of 6 hours} Contacts made of 25 1 » copper on zinc oxide. The ether evaporates and 293 parts of the reaction product are then collected in the built-on condensation section. The analysis results in a conversion of 55%, a yield of 73 $> methoxyacetaldehyde (Kp ^ _60: 92 ⁰ C; Pp of the 2.4-dinitrophenylhydrazone: 125 ⁰ O.).

Example 2

A mixture of 150 parts of ethylene glycol monoethyl ether (Κργ ₆₀ : ΐ35 ⁰ O), 150 parts of water and 3 parts of urotropine is obtained according to Example 1 within 5 hours at 100 Torr over a ^{contact heated to 280 0} O from 25 <t>

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Copper passed onto zinc oxide, the 295 parts of reaction product obtained in the condensation section show, at a conversion of $ 62> a yield of $ 78> ethoxyacetaldehyde (boiling point ₇₆₀ : 106 ⁰ G, BP of the 2,4-dinitrophenylhydrazone: 117 ⁰ O).

Example 3

200 parts Ä'thylenglykolmonoacetat (Kp ~ g _O: 189 ° ^{σ) "10} ° ^parts water and 2 parts of hexamethylenetetramine are evaporated at 100 Torr over 5 hours together over a heated at 300 ⁰ O contact from 25 i» copper on magnesium oxide. The investigation of the obtained in the condensation section 298 parts of the reaction product give a yield of 78 # acetoxyacetaldehyde (Kp ₁ -Qi75 ⁰ O, Pp of the 2.4-dinitrophenylhydrazone. 152 ⁰ C) at a conversion of 72 i>.

Example 4

Similarly as in the previous examples, a mixture of 150 parts of ethylene glycol monomethyl ether, 1.5 parts of a 40 ^ aqueous methylamine solution and 150 parts of water in 5 hours at 50 torr above 500 parts of a heated at 300 ⁰ O contact of Figure 10 i> copper on Magnesium oxide led. Examination of the recovered 292 parts of Umsetzungsprpduktes results in a turnover of 66 i "to a yield of 88 i" methoxyacetaldehyde.

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Claims (3)

2ÖA9162 O.Z. 27 05 claims 1. A process for the preparation of alkoxy and Acyloxyacet- ^ aldehydes by Tcatalytische dehydrogenation of the correspond to the alkoxy and acyloxyethanols at elevated temperature, characterized in that the dehydrogenation is carried out at temperatures of 150 to 350 ⁰ O in the presence of basic nitrogen compounds. 2. The method according to claim 1, characterized in that mab dehydrated at 200 to 300 ⁰ C. 3. The method according to claim 1, characterized in that the basic nitrogen compounds ammonia, uro- "tropine or alkylamines with alkyl groups ranging from 1 to 8 Containing carbon atoms. Badische Anilin- * Soda-Fabrik AG 209816/1738