DE933337C - Process for the production of alcohols - Google Patents

Description

Process for the preparation of aliphatic aldehydes with 3 to 5 Carbon atoms It is known by reacting olefins with carbon dioxide and Hydrogen (synthesis gas) in the presence of cobalt or cobalt compounds at increased Temperature and pressure to produce aldehydes. With this usually as "Oxosynthesis" processes, one already has aqueous cobalt salt solutions, to which acids or buffer substances were optionally added, as catalysts used. For example, one has olefins with synthesis gas in a countercurrent process using an aqueous circulating liquid containing the cobalt salt implemented the corresponding aldehydes.

The usual methods for the technical implementation of the oxo synthesis using aqueous cobalt salt solutions to obtain aliphatic Aldehydes from olefins with 2 to 4 carbon atoms had the disadvantage that the conversion is relatively low and the yield because of the formation of higher molecular weight By-products was impaired.

It has now been found that by reacting olefins with 2 up to 4 carbon atoms with carbon oxide and hydrogen in the presence of aqueous Cobalt salt solutions excellent yields of monomeric aliphatic aldehydes with 3 to 5 carbon atoms obtained if the reaction is continuously homogeneous Performs swamp phase. Here, the aqueous cobalt salt solution together with the gases to be converted or

Liquid gases from bottom to top through the reaction vessel, expedient an empty vertical high pressure pipe. The reaction conditions (amount the contact liquid, temperature and pressure) are chosen so that with them the catalyst solution is homogeneously dissolved in the reaction mixture.

At the reaction temperatures essentially suitable for the reaction from 150 to 200 ° and the preferred pressure range above about 200 at, preferably between 300 and 700 at, you are at the selected or setting Ratio between aqueous and oily phase above the critical solution temperature the aqueous phase in the oily phase. Accordingly, under these implementation conditions a homogeneous mixture flows through the reaction vessel.

To work up the reaction mixture, this is done from the reaction vessel exiting product initially cooled, e.g. B. to 20 °. After cooling down, you relax preferably at normal pressure and then passes at temperatures above 50 °, expediently between 80 and 2000 and possibly under pressure, the liquid product, if necessary with additional water, from bottom to top through a vertical one Vessel. In doing so, it is avoided that carbon monoxide has an additional effect on the reaction product allow; however, it is possible to use other gases, e.g. B. hydrogen, nitrogen or Carbon dioxide, to pass through the solution to facilitate expulsion of the carbon dioxide. With a sufficient residence time, which depends in detail on the reaction temperature used directs and is generally between 10 and 60 minutes, the reaction product Completely. freed from the dissolved cobalt compounds that the Cooling the treated mixture forms two layers, the non-aqueous one from the practically cobalt-free aldehyde or aldehyde mixture and the aqueous from one immediately reusable catalyst solution. Low losses to iEZobalt can be compensated by adding appropriate amounts of cobalt salt.

The salts of cobalt are preferably used as the catalyst with low molecular weight fatty acids, especially cobalt acetate or propionate. That However, the process can also be carried out with other soluble salts of cobalt. It is also possible to acidify or buffer the cobalt salt solution,. although compared to the use of the simple cobalt salt solutions, this is not worth mentioning Brings advantages.

To find the most favorable reaction temperature for the exothermic reaction To be able to comply, you can the reaction vessel in the usual way from the outside, for example through pressurized water circulation cooling or through evaporation of a suitable coolant, cool. The application of the sump phase process is particularly effective here favorable because the heat transfer from the reaction liquid via the wall of the Pressure vessel. the coolant is very effective. But you can also use the cooling make by circulating part of the reaction product and cools down according to the expected heat generation. Also a combination Both measures are possible, as is the use of a gas cycle.

It is already known to carry out the oxo synthesis in continuous Operation to lead the reactants in cocurrent through the reaction vessel. Here, however, olefins have been used as starting materials which have more than 4 carbon atoms contain, so not like the starting materials to be used according to the invention below normal conditions are gaseous. This was also the case with this direct current method Use of aqueous cobalt salt solutions as a catalyst is not intended, but cobalt compounds were soluble in organic medium. used. In contrast According to the present invention, the easy-to-use aqueous cobalt salt solutions used, with the help of which it is possible to use the direct current method in homogeneous sump phase from lower. Olefin hydrocarbons in good yield the corresponding saturated aldehydes 1 carbon atom richer.

It is true that lower olefins are already used in a discontinuous manner subjected to the oxo reaction in the presence of aqueous cobalt salt solutions, here but only a little propionaldehyde and a larger amount from ethylene, for example obtained unsaturated aldehydes. It is therefore surprising that from the same Starting materials using the same catalyst solutions are completely different and the very desirable result, the formation of much propionaldehyde and little unsaturation Aldehyde, is achieved when according to the invention in cocurrent in a homogeneous bottom phase is working.

Example I The implementation is in a vertical blank High pressure pipe with a clear width of 30 mm, a length of 2 m and an empty volume of I, S 1 executed. The pipe is surrounded by a jacket in which water under pressure enters Circulation is maintained in order to keep the temperature in the reaction vessel at 170 °. By at a total pressure of 350 at, the tube becomes 2.50 / 0 from bottom to top aqueous cobalt acetate solution is pumped (70 ccm hourly).

At the same time, 1.7 Ncbm of a gas mixture is pressed from below every hour a, which is made up of about 2301, propylene, 37% carbon oxide, 3701, hydrogen and 30%, inert gas- exists At the upper end of the tube, the reaction product, which is homogeneous in the heat, is drawn and leads it through a cooler into a pressure separator, from which at 200 hourly 0.3 Ncbm exhaust gas can be relaxed. The liquid reaction mixture emerges from the pressure separator deducted; one receives about 1 kg of one per hour. raw, about -0.050 /, cobalt-containing Butyraldehyde mixture and about 42 cm aqueous solution. From the aldehyde-water mixture is about 1 1 hourly without separation from bottom to top at 1500 through a pipe pumped from 1 1 capacity, cooled to 20 ° and the resulting two phases separated from each other.

The non-aqueous phase consists of the almost colorless butyraldehyde mixture; it has the following key figures: cobalt content: not detectable acid number: 6 saponification number: 25 Hydroxyl number: o Carbonyl number: 700, corresponding to a butyraldehyde content of 900/0.

The aqueous phase consists of a cobalt acetate solution. she can after replenishing the water absorbed by the aldehyde in the first stage of the Procedure to be returned.

Example 2 The apparatus described in Example 1 is used in 185 "and 600 at pressure from bottom to top a 2.5% aqueous cobalt acetate solution pumped (65 cc per hour). At the same time, I, 7 Ncbm are pressed every hour from below a gas mixture consisting of 240in ethylene, 360in carbon oxide, 3701, hydrogen and 30/0 inerts. At the upper end, the reaction product is withdrawn and passed it via a cooler into a pressure separator, from which 0.3 Ncbm per hour at 20 ° Exhaust gas can be relaxed. In this case, this becomes homogeneous from the pressure separator Remaining liquid reaction mixture drawn off; one receives about 0.23 kg per hour of a crude propionaldehyde discharge containing about 0.030% of cobalt and about 70% of water contains. With further addition of about ion / water, the discharge is carried out with a Dwell of approximately 1 hour pumped through a 150 "tube 200 cooled and the resulting two phases separated from each other. The non-watery one Phase consists of the almost colorless crude propionaldehyde; it has the following key figures: Cobalt content: not detectable Acid number: 9.4 Saponification number: 39 Hydroxyl number: o Carbonyl number: 830, corresponding to a propionaldehyde content of 860 / o.

The aqueous phase consists of a cobalt acetate solution. she can be returned to the first stage of the process.

Claims (3)

PATENT CLAIMS: I. Process for the preparation of aliphatic aldehydes having 3 to 5 carbon atoms by reacting olefins having 2 to 4 carbon atoms at elevated temperature and under elevated pressure with carbon dioxide and hydrogen in the presence of aqueous cobalt salt solutions, characterized in that the Implementation carried out continuously in a homogeneous sump phase. 2. The method according to claim I, characterized in that the Reaction mixture cools, relaxed and without the addition of carbon monoxide, if necessary with further addition of water, to at least 50 °, preferably 80 to 200 °, heated. 3. The method according to claim 2, characterized in that one of the mixture subjected to the heat treatment and then cooled, the aqueous phase separated and recycled to the first stage of the process.