DE975502C - Process for the production of propionaldehyde - Google Patents

Description

ISSUED DECEMBER 14, 1961

B 28601 IVb / 12 ο

The addition of carbon monoxide and carbon dioxide, which has become known under the name of "oxo synthesis" Hydrogen (synthesis gas) to olefins under the influence of cobalt catalysts at elevated temperature and under increased pressure, different starting materials take place with quite different processes Ease. It is known that the reaction with the implementation of the ethylene with great Speed and high calorific rate. Accordingly, one has for this reaction recommended to take special precautionary measures, e.g. B. working in inert organic solvents or in an aqueous medium. Subject of German patent specification 891 842 is among other things a process for the production of propionaldehyde by oxo reaction of ethylene, in which vaporous cobalt compounds, in particular cobalt carbonyl and hydrogen carbonyl, used as a catalyst and the ethylene initially with the catalyst-containing synthesis gas below the reaction temperature, preferably at 60 to 100 °, mixed and the obtained Bring the mixture to the reaction temperature, preferably 110 to 180 °. But even with this procedure local overheating can occur, which leads to secondary, the yield of monomeric

109 744/11

Propionaldehyde-damaging side reactions lead ,, like ζ. B. the aldolization of the aldehyde and a decomposition of the ethylene with soot deposition. The method also has the disadvantage that part of the high pressure chamber is used for the mixing and heating of the gases must become.

It has now been found that these difficulties occurring in the oxo reaction of ethylene can be avoided avoids in a particularly simple way if you use the ethylene or the catalyst Synthesis gas or both to almost synthesis temperature, but at least 100 °, preheated and to a synthesis gas containing at least three times the theoretically required amount Intensive gas mixture, especially by means of a mixing nozzle, mixes and at high speed passes through the reaction zone and when the end gases after separation of the propionaldehyde returned to the reaction zone. This mode of operation has the advantage that the process is easy with Can perform much greater security, since the temperature is precisely maintained and carbon deposition and constipation can be avoided.

Already in the process of German patent specification 891 842 it was possible to use the synthesis gas in more than the theoretically required amount. In the present procedure, this is a necessary prerequisite for the perfect success of the reaction. The synthesis gas is used in at least twice the excess. The yield of propionaldehyde is, however, even better if you use even higher, z. B. 10 to 2-fold excess applies. The upper limit is only determined by economic considerations. The synthesis gas is expediently circulated and thus used for temperature control and only as much fresh gas with vaporous catalyst is added as corresponds to the consumption of carbon oxide and hydrogen. In order to be able to carry out continuous operation with circulating gas that is as uniform as possible, the ratio of CO: H _{2 is kept} at about 1: 1, although in principle the reaction can also be carried out if one of the constituents of the circulating gas is in excess.

The method is expediently carried out in empty high-pressure vessels, in particular pipes, which can be arranged individually or in bundles horizontally, vertically or at an angle. In order to be able to maintain the optimum conditions in the reaction zone, the tubes are expediently surrounded by a heating or cooling jacket through which steam or suitable liquid can circulate. The flow rate is preferably chosen so that the residence time of the ethylene in the reaction zone is less than 1 hour, expediently 2 to 15 minutes. In order to mix the gases fed into the reaction as intensively as possible, an effective mixing nozzle is preferably used. Such is shown schematically in the figure in section, for example. At A , one of the gases enters the centrally drilled pipe, which it leaves at high speed at B and where it enters the mixing space. At C the other gas enters the outer annulus which it leaves at D. To improve the mixing effect, inclined surfaces or grooves can be provided in the annular space so that a swirl is imparted to the gas.

The vaporous catalyst is expediently fed to the fresh gas in such a way that this or a partial stream thereof is continuously mixed with cobalt or with cobalt carbonyls brings together transferable cobalt compounds at elevated temperature and pressure. This can be done, for example, according to the method of French patent specification 996 378 or British Patent 690,149 or also by passing through "the solution of a cobalt salt done in a high-boiling inert solvent. The amount of the syngas introduced cobalt can be kept small; in general, 0.05 to ο, ι% Co are sufficient, based on the ethylene to be converted.

- The temperature of the incoming gases in the reaction zone is between 100 and I6O °, suitably from 20 to 40 ⁰ below the optimum temperature of the reaction; if this z. If, for example, 190 to 210 °, the temperature of the gases is suitably about 160 °. You can preheat all of the gases to be added to this temperature, or some of the gases can be correspondingly higher.

example

In an empty, vertical high-pressure pipe with a length of 5 m and a diameter of 120 mm and which is provided with a steam jacket, the following amounts of gas per hour are passed through a gas mixing nozzle inserted in the upper fifth: 1. 3.4 Nm ³ ethylene; 2. 4.5 Nm ^{3 of} a mixture of 50% CO and 5θ ^Ό / ο H ₂ , which was previously charged in the usual way with about ι g Co / m ³ in the form of cobalt carbonyl hydride (fresh gas); 3. about 50 Nm ^{3 of} a mixture of about 60% CO, 30% H ₂ and 10% C ₂ hydrocarbons (cycle gas).

All three gases are introduced into the nozzle under a pressure of 250 atmospheres after they have been preheated to 160 °, namely gases 1 and 3 in the outer annulus, and gas 2 in the central bore of the nozzle. The high-pressure pipe is heated from the outside with steam at 180 °. Due to the heat of reaction released, the internal temperature rises to 190 to 20 ° up to the middle of the tube. The exiting at the lower tube end in a reaction mixture passes at 15 ⁰ cooled precipitator, where the primary product formed separates liquid. About 50 Nm ^{3 of} unused gas are passed through a reflux condenser in order to liquefy the uncondensed aldehyde residues. B. a mole pump, pumped back _{into the pipe>: after they wiedex on}

i6o ° were warmed up. The rest is not unimplemented The gas and the liquid product are expanded. There are 8.9 kg of liquid per hour Product obtained that is 90 percent by volume monomeric! Propionaldehyde consists. About 10% of the imported ethylene are hydrogenated to ethane, about 5 to 6% are not converted.

Claims (1)

PATENT CLAIM: Process for the production of propionaldehyde by reacting ethylene with carbon oxide and hydrogen at elevated pressure and elevated temperature in the gas phase in the presence of cobalt carbonyl compounds as a catalyst with preheating and intensive mixing of the reactants, passing them through the reaction zone, separating the aldehyde formed and recycling the end gases , characterized in that the reactants are preheated to at least 100 °, an at least three-fold excess of the theoretically required amount of synthesis gas is used and the reactants are carried out through the reaction zone at high speed. Considered publications:
German Patent Nos. 888843, 891842; U.S. Patent No. 2327066. 1 sheet of drawings