DE1028556B - Process for the purification of oxo-aldehydes - Google Patents

Description

Process for the purification of oxo-aldehydes In the conversion of olefins with carbon oxide and hydrogen at elevated temperature and pressure is known to contain oxygen in the presence of catalytically active cobalt carbonyl compounds Products, mainly aldehydes. The proportions of cobalt carbonyl compounds dissolved in the reaction product impair the shelf life and insulation of the crude aldehydes and interfere their subsequent hydrogenation to alcohols. It is therefore common to use the cobalt compounds to remove from these crude aldehydes. So it was suggested to reduce them at Carbon oxide partial pressure until the thermal decomposition of the carbonyl compounds below Deposition of cobalt metal or heat it with water or aqueous acids optionally to treat at elevated temperatures and pressures, where filterable Compounds or dissolved salts of cobalt can be obtained. It was also suggested that Bringing the crude aldehydes into contact with oxygen-containing gases in order to reduce the amount contained therein dissolved volatile carbonyl compounds in easily isolable metal compounds convict.

In addition to the cobalt carbonyl compounds formed from any added cobalt compounds, the crude aldehydes contain, in all practically occurring cases, small amounts of carbonyl compounds of other metals dissolved, which are formed by the interaction of the carbon oxide with the materials of the storage tanks, pumps, pipes, etc. Iron carbon in particular often occurs in concentrations of 0.001 to 0.1% Fe (cf. USA Patent 2721136) in the crude aldehydes and must be removed therefrom. When you get the full yield of oxygenated products. wants to obtain, a simple thermal decomposition, as it has been proposed many times for the removal of the cobalt carbonyl compounds, is not sufficient to destroy the considerably more stable iron carbonyl (see US Pat. No. 2604491). Rather, complete disintegration does not occur until the subsequent hydrogenation, the deposits of metallic iron either clogging the preheating or damaging the contact. The carbon dioxide released during the decomposition poisons the hydrogenation contact and reduces its service life, especially if the hydrogen is circulated.

Attempts have therefore already been made to decompose the metal carbonyl compounds to make it more complete by adding steam. Here, too, the disintegration takes place the iron carbonyl is not nearly as smooth as that of the cobalt carbonyl compounds; in addition, the metals are obtained as precipitates, so that filtrations and carriers are necessary. The also proposed treatment with mineral acids requires in the case of iron carbonyl, energetic conditions which easily lead to side reactions (French Patent 667 824); in addition, especially with the aldehydes with 3 to 5 Significant losses of carbon atoms due to their solubility in acids and washing water a. There is another suggestion especially for these reactive aldehydes for the removal of iron carbonyl, namely the treatment with alkalis, because of the Aldolization tendency of these compounds hardly applicable. Also the proposed one Oxidation of the metal carbonyl compounds contained in the crude aldehyde with air, especially in the presence of organic acids, leads, if one does not, to yield losses wants to accept, not to remove the iron carbonyl; the following Distillation produces a yellow-colored aldehyde, which turns into iron hydroxide on storage separates, which easily causes clogging and its removal another Makes distillation or filtration necessary. Even a distillation of the oxidized Crude aldehyde in the presence of steam gives an iron-containing distillate Aldehyde, even if mineral acid is added to the material to be distilled.

Finally, it has already been described that in the case of the accumulation of Carbon oxide and hydrogen on olefins after separation of the organic reaction products used aqueous solution in which the iron is dissolved as sulfate, by adding cobalt carbonate in an amount equivalent to the iron content, and intensive stirring to regenerate while blowing air. This should be solved Iron compounds are precipitated. About the purification of the organic reaction products and specifically about the removal of iron carbonyl therefrom is given in this reference nothing mentioned.

It has now been found that this is in the reaction products of the addition Iron carbonyl dissolved in olefins by carbon monoxide and hydrogen in a simple manner Can be removed when looking at the reaction products by means of salts of trivalent cobalt is oxidized. These cobalt (III) salts can be in dissolved form can be obtained in various ways, e.g. B. by oxidation of cobalt (II) salt solutions with hydrogen peroxide.

Cobalt (III) salts are particularly easily obtained for the process of the present invention by blowing in oxygen-containing gases, e.g. B. air, into the crude reaction products of water gas addition to olefins, if it is ensured that water is present and a hydrogen ion concentration suitable for the rapid conversion of cobalt carbonyl compounds to salts of trivalent cobalt is maintained. The amount of water present is expediently chosen so that the metal compounds formed leave the oxidation zone in dissolved form; it can be 0.1 to 5%, depending on the metal content of the crude aldehyde. The water can either be added immediately before the oxidation or be contained in the crude product of the addition of water gas to olefins in a homogeneous or disperse phase if it was added before the addition or was formed in the addition stage by side reactions; In the latter cases, it may not be necessary to add more water. But you can also add a lot more water and work in a disperse mixture if this is desired for temperature control of the oxidation or with a view to the further processing of the metal salt solutions. The pH of the oxidation zone should be chosen so that the iron and cobalt salts formed remain in solution, but not too low, so that the formation of the trivalent cobalt salts does not occur too slowly. In the latter case there is significant oxidation of the crude aldehyde even before the iron carbonyl is completely destroyed. It is therefore expedient to work at a pH value which is sufficient for the rapid formation of salts of trivalent cobalt from cobalt carbonyl compounds and at which no significant oxidation of the aldehyde occurs, generally at pH values above 3. It is also advisable to use to work at pH values at which no significant aldolization occurs, generally below pH 9. Even more rapid formation of cobalt (III) salts is achieved at pH values of 4 to 6. The optimum hydrogen ion concentration can be set make by buffering the aqueous phase; In the case of some crude aldehydes, the addition of pure water is sufficient if the constituents of the crude product enable suitable pH adjustment. A short preliminary test can be used to determine for any crude aldehyde whether and which buffering is necessary in order to achieve the rapid formation of cobalt (III) salts. The influence of the p11 value on the formation of the cobalt (III) salts required to destroy the iron carbonyl can be seen from the following series of experiments. In each case 800 g of a crude butyraldehyde, which is obtained by oxo synthesis, were intensively stirred with 300 g of buffer solution while 10 l / h of air were passed through. Depending on the pH, the following oxidation times were necessary to convert the cobalt carbonyl compounds into cobalt (III) salts: PH duration of oxidation mean temperature 6.04 25 minutes 21 ° C 5.05 30 minutes 20 ° C 4.07 40 minutes 19 ° C 3.05 80 minutes 19 11 C 1.97 115 minutes 30 ° C At a pH value of 1.97, the formation of cobalt (III) salts was only possible in a comparable time if the temperature was increased. At the same time, however, aldehyde oxidation clearly occurs because of the simultaneously increased residence time. The oxidation of the iron carbonyl is accelerated by increasing the temperature; in general, however, a temperature of 10 to 30 ° C. is practically sufficient, but it is also possible to work at higher or lower temperatures.

In the process of the present invention, cleavage is obtained of carbon monoxide solutions of salts of the metals of the iron group that make them up can be recovered in various ways. A particular advantage of the Process is that the metal compounds, even without the addition of acids, in dissolved form and thus does not require filtration or neutral washing. Another advantage lies in the possibility of removing the aldehydes by distillation completely from the oxidation mixture containing the now non-volatile metal salts to be kept metal-free and water-clear. If mineral acids are added to the material to be distilled too, so you can also get completely colorless distillation residues that are after neutral washing directly as high-boiling solvents, additives to plasticizers and suitable as components of technical emulsions and preparations.

The method can be carried out in various ways. One can work batchwise or continuously in stirred vessels by being in the presence or with the introduction of a calculated amount of air, the crude aldehyde and water or an aqueous solution thoroughly mixed until the formation of its green color recognizable cobalt (III) salts is complete. Then that of iron carbonyl free aldehyde can be distilled off directly or after separation by washing with warm water or adding small amounts of mineral acids from the last portions of dissolved Metal compounds are freed.

The oxidation of iron carbonyl is particularly simple and inexpensive in a continuous process. One can enter a reaction zone advantageously a pipe equipped with distribution devices from one side, z. B. in a vertical packed column, from below air and crude aldehyde flow in and at the same or a different point, in the selected example z. B. from above, add the aqueous phase, that is, an aqueous solution or water. A zone of KObalt (III) salrL formation quickly forms, which is located on the green color easily recognizable and by controlling the feed of the reactants must be kept at the desired height. You can use the two 'liquid components too lead together in countercurrent to the air or all reactants in cocurrent let react.

Instead of filling bodies, other distribution devices can also be used will. The use of vibrating columns is also possible and has a special design easy if you arrange the oscillating plates in a fixed position and the liquid phase pulsating.

In general, the iron carbonyl contents of the crude aldehyde vary around a mean. Safe oxidation is then expediently achieved by that the metered air is just enough, a small part of the aldehyde, about 0.2 up to 0.5 per cent., to be oxidized. The minimum residence time can be determined very quickly by leaving a sample of the reaction product from the oxidation zone distilled; no iron or carbonyl must pass over.

For the course of the reaction it is assumed that the iron carbonyl is absent of cobalt (III) salts is oxidized more slowly than the aldehyde, so that its complete destruction is only possible with simultaneous losses of aldehyde is. If, on the other hand, cobalt (III) salts are present, they either oxidize the iron carbonyl directly, or they mediate the oxidizing effect of the air, preferably on the iron carbonyl compounds. These compounds dissolved in the crude aldehyde are therefore quickly converted into non-volatile, soluble iron salts converted without noticeable losses of aldehyde.

The following are those when working according to the known working methods Results obtained compared with those according to the present invention.

Known work: A. This example shows the resistance of iron carbonyl to heating with mineral acids and is proven by the following tests: a) 800 g of a crude product with 75.60 /, propionaldehyde and 0.120 /, cobalt obtained by adding carbon oxide and hydrogen to ethylene (dissolved as cobalt carbonyl compounds) were heated with 200 g of 0.1 N sulfuric acid under nitrogen. The aldehyde fraction passing over at 48 ° C. was deep yellow in color. It was found to be free of cobalt, but contained iron in a concentration of 0.008 per cent. When standing for a day, a large part of the iron had settled on the ground in the form of hydroxide; the supernatant aldehyde was still slightly yellow in color.

ß) For comparison, a similar experiment was repeated with a crude product obtained by adding carbon oxide and hydrogen to propylene. 500 g of this product with 0.31 % cobalt (dissolved as cobalt carbonyl compounds) and 0.120 / () iron (dissolved as iron carbonyl) were heated with 100 g of 0.1 n-sulfuric acid. A distillate of 374 g was obtained via a packed column with a filling height of 80 cm, which distillate passed to 95 ° C .; a distillation head was expediently used which separated the condensate into an aqueous and an organic phase and, when the organic phase was removed, allowed the aqueous to be returned to the column. The first parts were deep ocher, the last light yellow. The fillings in the lowest zone were covered with a cobalt coating, and a cobalt level had formed on the bulb wall. No cobalt was detectable in the distillate, but 0.02 g of iron was found dissolved in it as carbonyl and a further 0.01 g as hydroxide.

B. The resistance of iron carbonyl to oxidation is determined by the following experiments clearly: a) 400 g of one by adding carbon oxide and hydrogen cobalt- and iron-containing crude aldehyde obtained on diisobutylene were mixed with 100 g of 0.1N sulfuric acid intensively mixed in a stirred flask. At the same time, 101 / h of air were introduced. After 20 minutes, the air flow was turned off and the crude product, which took place the originally brown color had now turned a light pink color Using the distillation head indicated under A, ß distilled off. Thereby went the first 200 g as a yellow colored liquid, which gradually emerges when standing Farewell to iron hydroxide. The same result was shown in an experiment in which instead of sulfuric acid an addition of acetic acid was present during the oxidation.

ß) A similar experiment was carried out with a crude butyraldehyde, derj 0.086 "/, cobalt and 0.0085% iron dissolved in the form of carbonyl compounds contained. 1000 g of this product were mixed with 300 g of 0.1 n-sulfuric acid while being passed through of 101 / h air stirred intensively for 35 minutes at 23 ° C. During this time no cobalt (III) salts recognizable by their green color were formed; the originally brown color lightened and turned pink. The product separated immediately and smoothly into a colorless aldehyde layer and a clear pink-colored acid layer. The latter contained 745 mg cobalt and 8 mg iron, that is to say 88 per cent of the cobalt and 9.4% of the iron passed into the aqueous phase in the form of cations. Of the Aldehyde was then with the addition of 300 g of 0.1 n-sulfuric acid with steam distilled, 972.5 g of cloudy yellow distillate passing over at 96.5 ° C. Of the Acid remained in the flask 262 g, they contained 68 mg Co and 25 mg Fe, i.e. H. another 8 or 30% of the metals dissolved as cations. From cobalt were accordingly 96 per cent. Of iron, but only 40 per cent. By a combination of oxidation in its absence recovered from cobalt (III) salts and steam distillation in the presence of mineral acid. The distillate was free of cobalt but contained 44 mg of iron, i.e. H. 52 ° / o of the original existing iron, which gets into the distillate as undestroyed iron carbonyl was.

C. The results obtained when working in the absence of compounds of the trivalent cobalt result from the following experiment: Into a vertical, Glass tube filled with Raschig rings of 2 m height and 1 l of free contents were from below 2 kg of crude aldehyde per hour, obtained from the addition of water to ethylene was, as well as 81 air introduced. At the same time, 500 g of 0.1 per hour from above n-sulfuric acid applied to the packing layer. The aqueous layer was pulled off at the lower end of the tube. The aldehyde was at the top of the tube taken together with the air and separated from this in a separator. from the separator was placed in the middle of a distillation column 2 m high, whose bladder was charged with 210.1 N sulfuric acid. The withdrawn at the top of the column Propionalhedyd was deep yellow in color and contained 0.0025% iron as carbonyl solved, since no cobalt (III) salts in the specified conditions Had formed an oxidation zone.

Working according to the invention: Example 1 As soon as when continuing of the experiment described under C, the supply of sulfuric acid was reduced by half and was otherwise worked under otherwise identical conditions, jumped through the change in the hydrogen ion concentration the formation of cobalt (III) salts at. The brown liquid previously in the tube took on the typical of these salts green color, and the propionaldehyde withdrawn at the top of the column was immediately completely colorless and metal-free. The same effect was achieved by increasing it the amount of air. On the other hand, if you reduce or increase the air supply so much the acid supply so far that the formation of the cobalt (III) salts did not occur because at the low pH value the residence time for oxidation was not sufficient, so it occurred immediately yellow colored iron-containing aldehyde again at the top of the distillation column on. This transition, which could be repeated in both directions, shows the influence of the hydrogen ion concentration on the formation of the cobalt (III) salts and their importance for the oxidative destruction of iron carbonyl in particular obvious way.

EXAMPLE 2 1000 g of the crude butyraldehyde mentioned under B, β were stirred intensively for 35 minutes at 23 ° C. with 300 g of 5% Na HC 03 solution while 10 1 / h of air were passed through. After 5 minutes the formation of cobalt (III) salts was recognizable by a rapidly increasing green color. After 25 minutes, the coloration caused by the cobalt (III) salts remained constant. In the deep green water layer 760 mg cobalt and 48 mg iron were found. Thus 89% of the cobalt and 56% of the iron had passed into the aqueous phase in the form of cations. 911 g of the aldehyde were then fractionated with the addition of 302 g of 0.1 n-sulfuric acid using the distillation attachment indicated under A,, B, with 863 g of completely clear, colorless distillate passing over at 96 ° C. The acid layer remaining in the flask contained 90 mg Co and 38 mg Fe, ie a further 11 and 45% of the metals, respectively. Under the conditions described under B, but in the presence of cobalt (III) salts, the cobalt and iron were therefore completely recovered as cations. The distillate was completely free of cobalt and iron. Example 3 In an experiment carried out according to Example 1 with a tube with 21 free capacity, 2 kg per hour of crude butyraldehyde obtained by the addition of water gas to propylene were treated with 20 l / h of air, but from above, instead of 0.1 N sulfuric acid, distilled water given on the packing layer. “The aqueous layer was withdrawn at the lower end of the pipe 'I' ° '". The aldehyde was removed together with the Lu' @ '#, Eint '; Abandoned distillation column or was fed to a washing tower with 60 ° C warm water to remove the last fractions of' metal salts. Shortly above the entrance :, place of the aldehyde, a green zone began to form, and the upper half of the tube showed the equal to @ Hi ,, moderate green color of the cobalt (III) salts formed: At the lower end of the pipe, a dividing line between aldehyde and "water" was kept at a constant level by regulating the water drainage with the crude aldehyde used, a medium suitable for the rapid formation of cobalt (III) saltseg ,, Destruction of the iron carbonyl , 'is sufficient. On consecutive days, ratios of the crude (a) and air-treated aldehyde (b) were determined as follows # °% aldehyde °% ° acid zo 2 ° 1 / h ljh loh (as butyraldehyde) (as butyric acid) n @ d @ aldehyde H20 air ", a 53.7 1.4 1.4014 0.858 6 1.6 50 b 53.1 2.2 1.4024 0.861 a 59.0 0.5 1.4010 0.840 6 1.6 50 b 58.6 1.4 1.4014 0.845 a 67.5 0.4 1.3964 0.835 6 1.5 15 b 67.1 0.8 1.3969 0.840 a 66.9 0.1 1.3989 0.832 6 1.5 15 b 66.5 0.5 1.3989 0.839 The aldehyde treated with air was completely free of volatile metal carbonyl compounds and gave a water-white product on distillation.

Example 4 A circulatory apparatus consisting of two vertically next to each other standing empty glass tubes of 3 m length connected to one another at the top and bottom and 7 cm or 3 cm clear width is filled with crude propionaldehyde, which 0.1% cobalt and 0.04% iron in the form of carbonyl compounds and of at the time of manufacture still contains 1.1% dissolved water. At the bottom of the further The pipe is blown through a frit 301 / h of air, whereupon a cycle is established of the product. After the light yellow product due to the formation of cobalt (III) salts has turned deep black green at a p $ of 6.2, there will be a continuous influx of Every hour 121 crude product passed into the lower end of the wide pipe. A corresponding Amount of carbonyl-free product is passed through an overflow at the top of the narrow tube withdrawn and fed to a distillation column, the bubble with 2N sulfuric acid is loaded. At the top of the column, a water-lighter one becomes more free from traces of metal Propionaldehyde withdrawn. If the air is replaced by nitrogen, it stays that way The crude product gets its light yellow color, and the propionaldehyde soon distills yellow Colored to brown over and proves to be ferrous.

Claims (6)

PATENT CLAIMS: 1. Process for the purification of oxo-aldehydes by Removal of iron carbonyl, characterized in that the iron carbonyl oxidized by salts of trivalent cobalt. 2. The method according to claim 1, characterized in that the oxidation by means of salts of: trivalent cobalt and oxygen-containing gases. 3. The method according to claims 1 and 2, characterized characterized in that the salts of trivalent cobalt by oxidation of Cobalt compounds that are contained in dissolved form in the products of the oxo synthesis, generated. 4. Process according to Claims 1 to 3, characterized in that the Oxidation in the presence of water and a concentration of hydrogen ions. " those for the rapid formation of salts de§'l; ' trivalent cobalt from cobalt carbonyl compounds; ,, ' is sufficient without at the same time an essentialei, 1,;,; Aldehyde oxidation takes place. 5. Process according to Claims 1 to 4, characterized in that one is carried out continuously the product of the oxo synthesis and an oxygen-containing one in a reaction zone Gas and an aqueous solution necessary to adjust the hydrogen ion concentration :. or water continuously introduces and from this' ,,: reaction zone directly metal carbonyl-free aldehyde continuously withdraws. 6. The method according to claims 1 to 5, characterized in that the reaction zone has a ver; ''. , dividing facilities equipped pipe is. Considered publications German patent specification No. 918 566.