JPS6241582B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for separating aliphatic aldehyde isomer mixtures. It has been known that zeolite has a specific three-dimensional network structure, and that when the crystal water in the cavities or pores surrounded by this is dehydrated, cavities with a uniform pore size can be created without destroying the crystal lattice. ing. It is also known that this cavity has a pore diameter of several angstroms, which corresponds to a certain molecular size, and exhibits a molecular sieve effect that selectively captures and adsorbs small molecules with a specific effective diameter or less. Method of separating n-paraffin and isoparaffin using the molecular sieve effect of zeolite, method of separating n-olefin and isoolefin, n-
Methods for separating alcohol and iso, sec- or tert-alcohol, and methods for separating water in organic compounds are well known, such as separation of propane and propylene using zeolite, separation of n-paraffin and isoparaffin, and various It is also applied industrially to dehydration of organic compounds. However, there have been no reports on the adsorption selectivity of zeolites for compounds having bulky and highly reactive functional groups such as aldehydes. The reasons for this are that the adsorption selectivity of aldehyde isomers by zeolite was not expected due to the high bulk of the aldehyde functional group, and that zeolite has strong solid acid-base properties that allow it to react with aldol condensation, Canitzaro reaction, etc. Zeolites were thought to be unsuitable for treating aldehydes, which tend to undergo various ionic reactions, and furthermore, since aldehydes are easily converted to carboxylic acids by air oxidation, there were concerns that zeolites would deteriorate due to exposure to acids. Examples include being hot. The present inventor investigated a method for adsorbing and separating isomer mixtures of compounds with bulky functional groups such as aliphatic aldehydes and aliphatic carboxylic acid esters using zeolite, and found that in aliphatic carboxylic acid esters, the isomer mixture is However, for aliphatic aldehydes, clear adsorption selectivity between isomers was observed when zeolite with a pore size of 4 to 7 Å was used as an adsorbent, and this is a cause for concern. The present invention was achieved based on the discovery that the increase in boiling point due to various ionic reactions is relatively small and can be suppressed to an almost negligible level by appropriately selecting conditions. The present invention will be explained in detail below. The subject of the present invention is isomeric mixtures of aliphatic aldehydes, in addition to isomeric mixtures of aldehydes with the same number of carbon atoms, such as, for example, mixtures of n-butyraldehyde and isobutyraldehyde.
n-butyraldehyde, isobutyraldehyde,
Mixtures containing isomers of aldehydes having different numbers of carbon atoms, such as a mixture of n-valeraldehyde and isovaleraldehyde, can also be isolated by combining them with distillation. In particular, the present invention is preferably applied to purifying a branched aliphatic aldehyde containing a small amount of linear aliphatic aldehyde. The adsorbent used in the method of the present invention is a cage-type zeolite having an effective pore size of 4 to 7 Å, including naturally occurring zeolites such as chiabazite, mordenite, Molecular Sieve 4A, Linde trademark, Molecule - Contains synthetic zeolites known as Sieve 5A and Molecular Sieve AW-500. These zeolites usually have ions of alkali metals or alkaline earth metals such as sodium, potassium, and calcium, and can be ion-exchanged with other metal ions or hydrogen ions; Because of the strong solid acid strength of hydrogen-type zeolites, aldehydes with high ionic reactivity cause chemical reactions, so it is recommended to use zeolites with relatively low acid strength that have been ion-exchanged with alkali metals or alkaline earth metals. preferable. The present invention uses conventional adsorption separation methods such as catalytic hyperadsorption, fixed bed adsorption, moving bed adsorption, and fluidized bed adsorption to separate isomer mixtures of aliphatic aldehydes into effective pore sizes of 4 to 7 Å. This is carried out by contacting the zeolite with zeolite. When carrying out the contact treatment, if the treatment temperature is too low, the adsorption rate will be low, and if it is too high, various ionic reactions of aldehydes will become significant, so a treatment temperature of 0 to 60° C. is usually selected and the treatment is carried out in a liquid phase. In addition, in order to prevent the aldehyde from being oxidized by oxygen, the aldehyde is contacted with the aldehyde under its own vapor pressure under an atmosphere of a gas inert to the aldehyde such as nitrogen or carbon dioxide, under normal pressure or slightly pressurized state, or after reduced pressure. Processing is performed. Through the above treatment, the linear aliphatic aldehyde is selectively adsorbed onto the zeolite, and a purified branched aliphatic aldehyde can be obtained. The linear aliphatic aldehyde adsorbed on zeolite can be desorbed with a solvent such as water or n-paraffin, and easily recovered by distillation.
In addition, zeolite can also be recovered and regenerated by operations such as reduced pressure treatment and heat treatment. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Examples 1 to 4, Comparative Examples 1 to 3 Table 1 below

Use the various zeolites listed in [Table]. Powder products are used as is, molded products are pulverized and then sieved to 42 to 100 mesh or 20 to 42 mesh, and heated at 320℃ in a nitrogen stream.
After dehydration by heating, the mixture was accurately weighed and placed in a 20 ml blood collection container equipped with a silicone rubber septum, and after vacuum degassing, a predetermined amount of isobutyraldehyde containing a trace amount of n-butyraldehyde was added. After this was left standing in a constant temperature bath (27°C or 5°C) for 40 hours, the concentration of n-butyraldehyde was measured by gas chromatography using benzene as an internal standard. Table 2 shows the usage amount of various zeolites, treatment temperature, isobutyraldehyde treatment amount, and n-butyraldehyde concentration before and after isobutyraldehyde treatment.
It is written in

[Table] Example 5 An experiment was conducted in the same manner as in Examples 1 and 4 using a mixture of 3% n-butyraldehyde and 97% isobutyraldehyde as the aldehyde isomer mixture, and after standing for 24 hours. The concentration of n-butyraldehyde was analyzed, and the equilibrium adsorption amount of n-butyraldehyde on naturally produced mordenite (SM-30Na) and synthetic zeolite (Molecular Sieve 5A) was measured. Continue to adjust the temperature of the constant temperature bath.
When the temperature was raised to 40℃ and left for 10 hours, n-
Although the concentration of butyraldehyde decreased slightly, high-boiling substances mainly consisting of dimers and trimers produced by condensation of butyraldehyde were detected.
The results are shown in Table-3.

【table】

Claims (1)

[Claims] 1 A mixture of aliphatic aldehyde isomers at 4 to 7 Å
The isomer mixture of aliphatic aldehydes is characterized in that the linear aliphatic aldehyde is selectively adsorbed onto the zeolite by contacting it with a zeolite having an effective pore size of . A method of separating into group aldehydes.