DE698970C - Process for the production of carboxylic acids by catalytic oxidation of ketones - Google Patents

Description

Process for the production of carboxylic acids by catalytic oxidation of ketones It is known that ketones are oxidized to acids by means of oxygen or oxygen-containing gases in - liquid phase oxidation catalysts, such as manganese, Cobalt, copper and iron, too. These metals are in the form of their oxides or carbonates or bound to acetic acid or other organic compounds, z. B. as Acetylaoetonat.e applied.

. It has now been found that the oxidation of the ketones proceeds particularly advantageously if the metals which act as oxidation catalysts are used in the form of their nitrates. This achieves faster implementation and thus better space-time yields. In addition, one can work at milder temperatures, which further reduces the in itself only slight degradation to carbonic acid. While, for example, from methyl ethyl ketone with the catalysts used up to now, when certain working conditions are used, about -a5 g of acids per square cm of the vessel transverse line are formed, under otherwise identical conditions, acid formation, volu 40 and more, is achieved with the nitrate catalysts g per day and qcm. In the case of other ketones, the use of: aitrate-containing oxidation catalytic converter gives similar, in some cases even better, results. Suitable ones are, for example, manganese, cobalt, copper, iron nitrate and mixtures of these nitrates near or with indifferent substances. Either ready-to-use nitrates or other compounds of the metals in question can be used, or they can be used together with saltpeteric acid. - For example, you can - the to 'oxidative ketone catalysts: - -the kind mentioned how Mangain-, cobalt, Eisenacetat- or carbonate, and-concentrated Saipet, ersäure @ zusetz, en. The oxidation of the ketones is carried out partially continuously, with the converted ketone being continuously replaced by fish ketone and the ketone ketone which is most favorable for oxygen absorption is adhered to. The reaction mixture, which has already largely been converted into acids, is removed continuously or from time to time from the reaction vessel. Continuous addition or repeated addition of catalyst ensures that the most favorable amount of catalyst is present in each case. .

Example i '"In: a cylindrical, provided with a reflux condenser Reaction vessel with a height of 40 cm and a clear width of 1 cm is first added 25 g of glacial acetic acid, in which i g manganonitrate, i g copper nitrate and i g iron nitrate are dissolved, and 4009 methyl ethyl ketone. During the heating that now takes place, this is done by a hot water jacket a flow of oxygen is started from below through a glass filter plate of 251 per hour to pass through the reaction mixture. The flow of oxygen will guided in the circuit and the consumed oxygen replenished.

At 6o to 65 ° C, oxygen uptake begins. The temperature is kept at 65 to 70 ° C. by passing a cooling liquid through the jacket. The oxygen uptake is 13 to 171 per hour. As soon as it begins to subside, 3009 methyl ethyl ketone and 2 g of the above-mentioned nitrate mixture are slowly added. Now: as the oxygen uptake decreases, take about 2/5 to 1/2 of the liquid content from the reaction vessel just above the glass filter plate and add fresh ketone and corresponding amounts of catalyst at the top. The cycle gas is renewed from time to time, as carbon monoxide and carbon dioxide and, if nitrogen-containing gas is used, nitrogen in it gradually accumulate too much.

The low-boiling components of the reaction product, which mainly consist of unchanged methyl ethyl acetone in addition to some acetaldehyde and formaldehyde and small amounts of diacetyl, are expediently returned to the oxidation process. When using 750.9 methyl ethyl ketone, 626 g of the ketone are converted daily into Io42 g of a mixture consisting of 8% acetic acid, 10% propionic acid, 60% formic acid and 3% water. -BBiSpi e1 2 Acetone is oxidized in the manner described in Example i at 68 to 75 ° C., manganese nitrate (initial amount 4 g) being used in place of the catalyst mentioned there. The formation of carbon dioxide is usually a bit stronger here than with. the oxidation of methyl ethyl ketone, while the oxygen uptake per hour is somewhat lower.

The yield of S.äuzen, based on converted. Acetone, is 91 % of theory. The oxyd4, ionsg: emis, ch freed from excess acetone consists of about 60% acetic acid, 30% formic acid, 5010 formaldehyde and -5% wa4er. The formaldehyde, which is obtained in the form of # -paraformaldehyde, can be obtained as such or fed back to the oxidation together with the acetone flow and converted into formic acid.

Example 3 A mixture of 300 g of glacial acetic acid, 3009 of cyclohexanone and 2 g of manganese nitrate is treated with air in the manner described in Example 1. To distribute the oxygen, it is better to use a bulbous, expanded glass tube instead of the glass filter plate, which is provided with many small openings about 1 mm in size. This avoids interference from adipic acid which crystallizes out. This glass nozzle is expediently located somewhat above the bottom of the vessel, so that a space remains below it in which the adipic acid which crystallizes out can settle.

The reaction temperature is expediently kept at 6o bis by cooling 70 ° C. However, once initiated, the reaction can also be used lower temperatures, e.g. B. 25 to 3o ° C, perform. The addition of glacial acetic acid It enables the oxidation to drive up to higher adipic acid concentrations. It also ensures that the adipic acid is obtained in a pure form.

The glacial acetic acid. is, after the crystallization and separation of the adipic acid from the reaction mixture removed from the reaction mixture, returned to the reaction vessel together with unreacted ketone. With a consumption of 20 to 23 liters of oxygen, about 44 g of cyclohexanone are oxidized to 65 g of adipic acid every hour. The yield of adipic acid is 95 to 970/0 of theory, calculated on the converted cyelohexanane.

Claims (1)

PATLNTANSPRUCII: Process for the production of carboxylic acids by catalytic oxidation of ketones with oxygen or oxygen-containing gases in the liquid phase, characterized in that the oxidation catalysts active metals in the form of their nitrates.