DE929249C - Process for stabilizing aldehydes - Google Patents

Description

Process for stabilizing aldehydes The invention relates to to a method for stabilizing aldehydes having more than one carbon atom in the molecule, especially to retard oxidation, peroxidation, polymerisation, Resin formation and the like

For example, if liquid aldehydes are left in contact with air they oxidize to the corresponding acids.

This oxidation can occur regardless of the nature of the material Container in which the aldehyde is located, and it can even through it be accelerated.

The acid that develops in an aldehyde can increase during storage Difficulties result, and they can also be used in many processes involving the aldehydes can be used, have a detrimental effect, for example in the production of synthetic resins or hydrogenation to alcohols.

It has already been suggested (U.S. Patent No. 2 223 41 1), to use a condensation product as an oxidation retarder for mineral oils, made by reacting formaldehyde with an N-substituted arylamine became.

It has now been found that N-substituted anilines, which additionally may be substituted in the ring, the substituents in each case being alkyl groups are a noticeable delay in response to the specified undesired Reactions possess the aldehydes to be stabilized when they are in small amounts can be added.

Although the mentioned known condensation products of formaldehyde and N-substituted arylamines under acidic, alkaline or neutral conditions, preferably at elevated temperature, but also, for example, at room temperature, can be obtained by the reaction spreads over several Allow days to extend, it has been found that the N-substituted anilines according to FIG Invention experience essentially no reaction with higher aldehydes and accordingly no increase in the acid value of such aldehydes occurs, which small amounts of N-substituted anilines, even after standing for 14 days Room temperature.

This was determined by the following experiments: I. A solution of 10 g of isopropylaniline in -100 g of nonaldehyde was used at room temperature for 14 days - left to stand, whereupon about 200 com petroleum ether (boiling point, 40 to 60 °) was added and the solution was saturated with hydrochloric acid gas. It became hydrochloric acid N-isolpropylaniline failed. This was filtered off, washed with petroleum ether and dried (melting point I75 ° and mixed melting point I80.5 °); Weight I2.4: g. The recovery of hydrochloric acid N-isopropylaniline was 100%. It was removed from this amount 3 g to the Carry out acid value determination.

2. In a similar experiment with 10 g of N-methylaniline in 100 g of nonaldehyde were, after this mixture was left to stand for 14 days, I I, 8 g of hydrochloric acid N-methylaniline obtained (melting point 1220 and mixed melting point 1230). The recovery of hydrochloric acid N-methylaniline was 91%, of which 3 g was the mixture for determining the acid value were branched off.

A small additional amount is understood to mean such amounts that at most a few percent by weight, preferably from 0.001 to 1 percent by weight. For example, about 0.1 to 0.5 is used to stabilize an aldehyde Weight percent of the substituted aniline, based on the treated aldehyde.

Regarding the aldehydes to which the invention is particularly applicable, include the liquid aliphatic aldehydes, such as acetaldehyde and higher aldehydes, for example iso- and n-butyr, aldehydes, such as those obtained, for example, by reaction of an olefin with carbon oxide, and hydrogen in the presence of a catalyst will. Nonylaldehyde is understood to mean the different ones. Isomers and their mixtures, which, for example, by reacting diisobutene, a mixture of 2,4,4-trimethylpentene- (I) and - (2), with carbon dioxide and hydrogen and which are obtained essential Contain quantities of 3,5,5-trimethylhexyl aldehyde.

It has been found that of the mentioned substituted anilines the propyl and butyl substituted their effectiveness over longer periods of aging retained to a particularly satisfactory degree.

The invention is illustrated in the following examples.

In Example 1, 15 cc of nonyl aldehyde was in the absence of air and exposed in the presence of 1/3000 mole of the retarder.

In Example 2, 30 ccm of nonylaldehyde in the air in the presence of 1/3000 mole of the retarder is exposed. - The oxidation was formed by measuring the Nonylic acid in equivalents of potassium hydroxide in milligrams per gram of liquid.

In the table below, p is the approximate weight percent of the retarder employed. Example 1 Example 2 Acid value acid value Milligrams milligrams KOH KOH per gram per gram 96 I68 96 264 p hour Hour p hour Hour Aniline ...... 0.25 89 I75 0, I3 55 224 N-methyl aniline ...... 0.3 6 II 0, I4 8 I07 N-ethyl aniline ...... 0.3 6 9 0, I6 7 I63 Nn propyl aniline ...... | 0.4 | 7 | 6 | 0, I8 | 5 | I3 N-isopropyl aniline ...... | 0.4 | 3 | 5 | 0, I8 | I | I0 Nn-butyl aniline ...... | 0.4 | 5 | I0 | 0.2 | 3 | I8 N-isobutyl aniline ...... 0.4 10 12 0.2 2 13 N-sec-butyl aniline ...... | 0.4 | 6 | II | 0.2 | 4 | I7 N-tert-butyl aniline ... | 0.4 | 4 | 5 | 0.2 | 2 | 22nd Nn-butyl p-toludine. . o4 0.4 3 6 0.2 2 12 Pure nonyl aldehyde .... | | 230 | 320

Claims (2)

PATENT CLAIMS: I. Process for stabilizing aldehydes with more than one carbon atom in the molecule, characterized in that one acts as a stabilizer at most - a few percent, in particular 0.01 to IO / o, and preferably 0.1 to 0.5 0/0, one or more N-alkyl-substituted anilines, which are also in the ring may be substituted by alkyl groups is used. 2. The method according to claim I, characterized in that one propyl- and / or butyl-substituted aniline, advantageously N-n-butyl-p -toluidine, used. References: French Patent No. 857 720; UNITED STATES. Patent Nos. 2,163,639, 22234II; M. M a r d e r, »Motor Fuels«, Vol. 1 (Berlin 1942), 499.