DE1123311B - Device for the production of aldehydes, ketones or acids corresponding to the aldehydes - Google Patents

Description

Device for the production of aldehydes, ketones or the aldehydes Corresponding acids It is known to use ethylene in the catalytic process with silver-containing Catalysts to ethylene oxide, with other oxidation catalysts at higher temperatures to mixtures of formaldehyde, acetaldehyde, formic acid, acetic acid and others To oxidize products. Here it failed to use acetaldehyde or acetic acid obtainable in technically useful yields. Also on precious metal catalysts As our own experiments have shown, only low yields were obtained under such conditions obtained in acetaldehyde, and formaldehyde usually predominates in terms of quantity far.

It is also known that compounds of palladium, platinum, silver or form copper complexes with ethylene. During the decomposition of the potassium-platinum complex the formation of acetaldehyde was observed. Other unsaturated compounds can have a beneficial effect on complex formation. However, these are stoichiometric Reactions in which the precious metal is obtained as such.

It has also already been described, aldehydes from olefins with 2 to 4 carbon atoms produce by reacting the olefins with oxygen-containing gases, e.g. B. air, at high temperatures, e.g. B. 480 to 590 'C, with the addition of nitrogen oxides in quantities 0.1 to 0.2 () / () bypasses heated bodies. For example, the Gas mixtures through narrow quartz tubes, over glowing dark red spirals made of chrome-nickel wire or through porcelain tubes filled with quartz glass or silica gel. In this reaction there is always a considerable breakdown of the olefin into shorter-chain ones Aldehydes instead. For example, in addition to acetaldehyde, ethylene is converted into large quantities Formaldehyde and from propylene and butylene only formaldehyde and acetaldehyde educated.

Palladium chloride dissolved in water has also already been described to reduce by means of ethylene to palladium metal, with the formation of acetaldehyde was observed. It has also already been described that propylene is fast and complete reduction of palladium chloride dissolved in water to palladium causes even when the propylene is mixed with nitrogen or air. Also the reduction of palladium chloride by isobutylene under the same conditions is already known, where - as well as the action of ethylene and propylene - no carbon dioxide has been developed.

According to the patent application F 23 432 IV b / 12 o (German Auslegeschrift 1 118 183) can produce aldehydes, ketones or acids corresponding to the aldehydes by mixing olefins with oxygen or elemental oxygen-containing Gases in a neutral to acidic medium in the liquid phase and in the presence of water and noble metal salts which complex with the olefins and in which the noble metals are still at least two few under the reaction conditions, and inorganic or organic redox systems.

When carrying out this reaction occur when working in liquid Phase sometimes difficulties in that formed copper (1) chloride or other connections fail and cause blockages that cause unpleasant malfunctions cause. In addition, these precipitated salts no longer stand for the reaction available, so that there is a more or less rapid drop in the yield comes.

It has now been found that such an oxidation can be achieved in a liquid Phase can run particularly advantageously in a device in which the metering device for the reaction gases and optionally for the addition of the hydrohalic acid or acid salts or organic substances that under the reaction conditions are hydrohalic acid split off, is controlled by a pH meter so that by regulating the olefin-oxygen = ratio and optionally also the addition of the acids or the aforementioned compounds pH value of 0.8 to 3 is maintained. If the pH drops, you have it in the Hand, by increasing the dosage of oxygen or decreasing the dosage of Olefin or to bring the reaction back into the optimal pH range by means of both measures. If the pH value rises, the opposite measures can be taken to restore the optimal one Set the pH range. One can use this method of controlling the reaction as well an addition of anion-donating compounds, e.g. B. of hydrohalic acid, or of organic compounds which, under test conditions, form hydrogen halide split off acid, or combine acidic salts. It is particularly beneficial at the beginning of the reaction, for example with hydrochloric acid, to a certain pH set and only during the ongoing reaction this by appropriate olefin-oxygen metering to control.

The pH measurements are best made with one of the commercially available devices carried out. You can either make continuous measurements with electrodes, which are built into the reactor, or discontinuous measurements by samples are taken at certain time intervals and their pH value is determined.

A special technical embodiment of the method consists in an automatic coupling of the pH meter with the dosing device for Olefin and oxygen. Once the pH value has been optimally adjusted, the reaction is controlled automatically.

Problems similar to those with the presence of copper salts can also arise occur in the presence of other redox systems. The device according to the invention leaves - so in general when converting the starting materials, the catalysts and use under the conditions that are the subject of patent application F 23432 IV b / 12 o are. For example, redox systems come into question, the salts of metals contain, which under the applied reaction conditions in several stages of oxidation can occur, e.g. B. Salts of Cu, Hg, Fe, Ce, V, Sb, Pb, Mn, Cr, Ti, Os. as Noble metal salts that form addition compounds or complexes with the olefins, come z. B. salts of palladium or platinum in question.

The oxygen can optionally be used in a mixture with inert gases will. Instead of olefins, olefin-containing gas mixtures in which z. B. saturated hydrocarbons are included.

The reaction can be supported by adding active oxidants, such as ozone, peroxide compounds, especially hydrogen peroxide, oxygen compounds of nitrogen, free halogen, halogen-oxygen compounds, compounds of higher valence levels of metals such as Mn, Ce, Cr, Se, Pb, Os. By such Additions of active oxidants will reduce the amount necessary for the reaction higher oxidation level of the precious metal facilitated. One can use these active oxidants also generate only during the reaction. If necessary, oxidation catalysts can also be used are fed. Before or during the reaction, it may be useful to add compounds which deliver anions under the reaction conditions used, to add, for. B. inorganic acids or salts, halogens, halogen-oxygen compounds or else organic, preferably saturated, low molecular weight aliphatic halogen compounds. This can counteract any depletion of anions and increase the service life of the catalytic converter. It is preferred when using noble metal halides add small amounts of halogen or halogen compounds.

The present process can be carried out, for example, at temperatures from 50 to 100 ° C, but optionally also at higher or lower temperatures carry out. In individual cases, the presence of salts, such as sodium or potassium chloride, have a beneficial effect. Furthermore, one can also with increased or decreased Pressure work. You can also support the course of the reaction by the fact that the concentration of the olefin in the reaction space is increased. This can be, for example can be achieved by increasing the pressure and / or by using solvents for the olefin. So you can use higher concentrations of olefin binding Metal salts, for example of copper or mercury compounds, or of organic, preferably the olefin concentration in the water-miscible solvents Increase reaction solution significantly. If necessary, you can also circulate the gases to lead. As a result of the presence of oxygen, in addition to aldehydes, the corresponding Carboxylic acids are formed in small quantities. If necessary, further oxidation can also be used the aldehydes, especially the acetaldehyde, to the carboxylic acids using the known oxidation experience associated with the present reaction and so the aldehyde stage can be skipped completely or partially.

The main olefin that comes into question is ethylene, that of acetaldehyde is implemented. Propylene delivers under the same conditions as ethylene Acetaldehyde provides acetone and propionaldehyde. From pt-butylene one obtains predominantly methyl ethyl ketone and also butyraldehyde.

In the case of the higher olefins, the reaction continues to proceed in an analogous manner Way. As a result of the relatively mild reaction conditions, almost only those arise Due to the structure to be expected oxidation products without isomerizations or Molecular splits are particularly prominent.

Of course, other unsaturated compounds can also be used, provided they are reactive under the given conditions, like diolefins, in the same way Way to be implemented. The reaction conditions may have to match those used Compounds and their physical properties are adapted. Even the higher ones Boiling points of the reaction products can, if appropriate, change accordingly make the procedural conditions necessary. Example In a reactor there are 500 ccm of a catalyst solution containing 50 e copper chloride with 2 mol of water of crystallization, Contains 0.5 g of palladium chloride and 2.5 ccm of concentrated hydrochloric acid and then one Has a pH of 1.25. A mixture of about 81 ethylene and about 41 oxygen will be made introduced into the reaction solution at a temperature of 80.degree. In the reactor are a high-resistance, high-temperature-resistant glass electrode and a calomel electrode built in and connected to a measuring device. By regulating the amount of ethylene or oxygen the pH will drop to 0.8 1.8 set, and you get so a trouble-free run with a yield of over 50% acetaldehyde, based on used ethylene.

Claims (1)

PATENT CLAIM: Device for the production of aldehydes, ketones or acids corresponding to the aldehydes by reacting olefins with oxygen or gases containing elemental oxygen by means of noble metal salts which form complexes with the olefins and in which the noble metals are still at least divalent under the reaction conditions, in an acidic medium in the presence of water and redox systems in the liquid phase, characterized in that the metering device for the reaction gases and optionally also for the addition of hydrohalic acid or acidic salts or organic substances which split off hydrohalic acid under reaction conditions is controlled by a pH meter that by regulating the olefin / oxygen ratio and optionally also the addition of the acids or the aforementioned compounds, a pii value of 0.8 to 3 is maintained.