DE1242223B - Process for removing n-pentanol- (1) from the reaction mixtures obtained in the oxidation of cyclohexane with oxygen-containing gases - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

EUCHES

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07c

C07C 49/30

German class: -13U> - 25

Number: 1 242 223

File number: Z 11331IV b / 12 ο

Filing date: February 12, 1965

Open date: June 15, 1967

In the oxidation of cyclohexane with oxygen-containing gases at temperatures above 140 ⁰ C, in addition to the desired oxidation products, such as cyclohexanone and cyclohexanol, and the less desired but still usable by-products, such as adipic acid, cyclohexyl formate, cyclohexyl acetate and other cyclohexyl esters, also various by-products, which can no longer be used for the actual objective of obtaining 1,6-difunctional end products or intermediate products leading to them. Such by-products are above all formic acid, acetic acid, valeric acid, caproic acid, e-oxycaproic acid or-caprolactone, cyclohexenylcyclohexanone, lower primary alcohols, especially n-pentanol- (l). While most of the listed, unusable by-products are removed in the known work-up by alkali treatment, the alcohols remain, of which in particular n-pentanol- (l) depending on the oxidation conditions in amounts of 0.3 to 1.5 percent by weight, based on the obtained cyclohexanone and cyclohexanol, can occur in the organic phase.

A subsequent separation of the n-pentanol- (l) by distillation turns out to be extremely difficult, since it can only be carried out successfully under normal pressure or slightly reduced pressure. For the sensitive cyclohexanone, this means quite a thermal load. Separation by distillation at pressures below 100 Torr is not possible because of the anomalous shape of the vapor pressure curve of n-pentanol- (l). At 40 to 50 ⁰ C the vapor pressure curves of n-pentanol- (I) and cyclohexanone intersect.

It has now been found that distillation and the associated thermal damage can be achieved of the cyclohexanone can be avoided if the separation of the contained in the reaction mixture straight-chain primary alcohols with the help of zeolitic molecular sieves. Here the effectiveness of zeolitic molecular sieves depends on the temperature and surprisingly also on the cyclohexane content of the reaction mixture.

The invention accordingly provides a process for removing n-pentanol- (l) from the reaction mixtures obtained in the oxidation of cyclohexane with oxygen-containing gases, which is characterized in that the organic phase of the reaction mixture, which has been separated off from the aqueous phase and deacidified, is converted into Presence of at least 10 ° / ₀ cyclohexane at temperatures from 30 to 150 ⁰ C Process for the removal of n-pentanol- (l)
from those in the oxidation of cyclohexane with
gases containing oxygen
Reaction mixtures

Applicant:

Vickers-Zimmer Public Company
Planning and construction of industrial plants,
Frankfurt / M., Borsigallee 1-7

Named as inventor:
Hansdieter Hofmann, Dörnigheim

treated with zeolitic molecular sieves with an average pore size of 4 to 13 Å.

The molecular sieves used can be of various origins and compositions. Preferred the commercially available modified synthetic zeolites with an average pore size of 5 to 8 Å. The molecular sieves can be used in any form, such as powder, granules or rods, take place. Adsorption can take place in the liquid phase with suspended moles or moles arranged in a fixed bed * Kularsieben or can be made in the gas phase. The ones with n-pentanol- (l) and others too molecular sieves loaded with straight-chain impurities can be regenerated in a known manner reuse. The process according to the invention is preferably carried out continuously.

The effectiveness of the selective adsorption depends, in addition to the temperature, above all on the cyclohexane content of the reaction mixture. This latter phenomenon, the influence of the cyclohexane content on the rate of adsorption of n-pentanol- (I), the consideration of which is essential for a successful implementation of the process, could by no means be foreseen. In the presence of larger amounts of cyclohexanes, the selectivity for adsorption of the n-pentonal (I) from the cyclohexane, cyclohexanone and cyclohexanol mixtures increases considerably. Advantageous concentrations for the cyclohexane are from 10 to 95 ° / o, preferably 50 to 80 ° / _0, the reaction mixture.

The inventive method for the removal of n-pentanol- (l) from mixtures, which in the cyclohexane oxidation with air can occur both in the sump phase, as in the fixed bed, in the trickle phase, as well as in the gas phase.

709 590/345

For the economy of the process also speaks that one with n-pentanol (l) and other straight-chain contaminants loaded molecular sieves can regenerate in a known manner.

The following examples characterize the process according to the invention:

example 1

200 g of a l ° / ^s oig solution of n-pentanol (l) in cyclohexane were placed in a round bottom flask with 40 g of a zeolitic molecular sieve at 5O ⁰ C for 50 minutes with frequent swirling treated. The gas chromatographic analysis subsequently carried out showed that the n-pentanol- (l) had been completely adsorbed.

Example 2

A solution containing 184 parts of cyclohexane, 8 parts of cyclohexanol, 6 parts of cyclohexanone, 0.5 part of n-pentanol- (l), 1.8 parts of monocarboxylic acids, calculated as acetic acid, were used as in Example 1 Treated 40 parts of a zeolitic molecular sieve. n-Pentanol- (l) could with the gas chromatographic Analysis can no longer be detected.

Example 3

The separated from the acidic reaction water and then treated with dilute sodium hydroxide reaction product of the Cyclohexanoxydation with air at temperatures above 14O ⁰ C had the following distillation after the partial removal of unreacted cyclohexane composition:

54 ° / o cyclohexane,

14.1% cyclohexanone,

27.0 ° / ₀ cyclohexanol,

0.55 ° / ₀ n-pentanol- (l),

4.30% by-products, such as low-boiling points
Shares, cyclohexyl esters and higher molecular weight products.

At a rate of 5 parts by volume per minute, 250 parts by volume of this mixture were at a temperature of 82 ° C several times over 90 volume *! parts of zeolitic molecular sieve rods, which are arranged in a fixed bed, passed.

The gas chromatographic analysis subsequently carried out showed that the n-pentanol (l) content had dropped to 0.06 percent by weight and the by-products that were not identified by 0.25 percent by weight had decreased.

Another attempt was made of the same

ίο reaction mixture removed the cyclohexane by distillation to a residual content of 8.1% and subjected the remaining mixture to the analogous treatment with molecular sieves of type 5 A. The previously determined n-pentanol (l) content fell in this case of 1.11% ^{only au} f 0.43%, that is, there were despite adequate capacity under comparable conditions only 61.2 ° / ₀ of the n-Pentanols- (l) Removed compared to 89.1% with higher cyclohexane content.

Claims (3)

Patent claims: 1. Process for the removal of pentanol (l) from the in the oxidation of cyclohexane with * 5 oxygen-containing gases resulting reaction mixtures, characterized by that the separated from the aqueous phase and deacidified organic phase of the reaction mixture in the presence of at least 10% Cyclohexane at temperatures of 30 to 150 ° C with zeolitic molecular sieves of a medium one Treated pore size of 4 to 13, in particular 5 to 8 Å. 2. The method according to claim 1, characterized in that one works at a temperature of 50 ^0C . 3. The method according to claim 1, characterized by that the reaction mixture has a cyclohexane content of 50 to 80 percent by weight. Considered publications:
German interpretative document No. 1 114 810.