DE1018396B - Process for converting gaseous or vaporous substances - Google Patents

Description

Process for converting gaseous or vaporous substances It is known that in the reaction of gaseous or vaporous substances in the gas phase or in the liquid Medium the conversion rate and thus the space-time yield all the higher is, the more concentrated the starting materials are used. This concentration are, however, in the impoverishment of substances under the reaction conditions Can decompose with strong heat generation, limits are set. Do you want to do it in In the interest of a high conversion rate, nevertheless use high concentrations, one must use equipment that can also handle strong, sudden increases in pressure, e.g. B. tenfold to be able to endure. The cost of a procedure will be through the use of such expensive printing equipment is understandably extraordinary high.

It has only been found that one can even with high space-time yields avoid the risk of decomposition and therefore with much less expensive Apparatus can work if one takes the reaction in the presence of a liquid medium It is carried out in such a way that the substances after they have been reduced to below the explosion limits diluted with gaseous or vaporous, non-decomposable substances, in one Absorber at a temperature below the reaction temperature in the introduces liquid medium in such an amount that its concentration in the solution below the ignition limit, preferably in the vicinity thereof, and that the solution is then reacted in a reaction vessel at such a high pressure that no or only insignificant amounts of the dissolved gases at the reaction temperature or vapors escape.

In this mode of operation, it is possible at appropriately high pressures Achieve a high concentration of the same decomposition substances without the risk of explosion exists and therefore requires expensive apparatus that can withstand even strong increases in pressure are.

It is already known from the literature, e.g. B. in the Cyclooctatetraen synthesis after the stairs, to safely process the acetylene with nitrogen dilute and introduce pre-compressed gaseous into the reaction chamber. The solvent is then pumped in against the pressure prevailing in the reaction vessel. The acetylene concentration is in this way of working, i. H. with direct gassing of the reaction space, however significantly lower than in the method according to the invention.

As non-decomposable substances to be admixed, such serve that deal with the decomposable substances, e.g. B. acetylene and its homologues, Ethylene, propylene or chlorine dioxide to implement.

The process, which is both continuous and dis carried out continuously can be used with particular advantage in such a way that one of the exiting the absorber, completely or partially freed from the reaction products Gases are relaxed to such a pressure that they are exposed to fresh starting material can add a pressure at which the decomposable raw material also in pure or in a highly concentrated form can no longer disintegrate detonatively. The enriched The mixture is then compressed again to the operating pressure and fed into the reaction chamber introduced.

For the implementation of the procedure it has to be with certain reactions proved to be advantageous, the gas space of the absorber with that of the reaction space to combine so that the liquid contents of these two apparatuses are under the same Pressure is on.

An embodiment of the invention is closer to the illustrations explained. The tubular, heatable or coolable reaction space A (Fig. 1) is through the narrow tube Z is connected to a standing vessel D above it. Small quantities of gases that are possibly released from the liquid in the vessel4 can become do not collect in this, but escape into the container D.

The liquid in which the reaction takes place flows out of the bottom Vessel A with the temperature t1 and is fed via the cooler O into the absorber B, in which they rise home with the circulating gas mixture at the lower temperature t2 is recharged according to consumption. The gas separates in the over B arranged separator C from the Liquid flowing through the preheater AT flows back to reaction vessel A, where it assumes the reaction temperature again. The circulating gas flowing out of C is fed to separator D via line E and from there via line F to the relaxation device G, where the pressure p1 is lowered to P2, and to the mixing vessel H. After the supply of the dem Consumption of corresponding amounts of decomposable gas, which by the compressor W is compressed to the pressure p2, via line C the mixture enters the compressor K and is compressed to the pre-pressure that corresponds to the pressure loss in the absorber and Piping system is higher than the actual working pressure p1 of the system. A Device 1 is used to measure the content of decomposable gas in the gas circuit flow. It can be connected to an alarm device or the bypass valve J of the compressor Press W to prevent impermissibly high concentrations from occurring in the gas system to prevent.

If necessary, a fraction can be passed through the line S provided with a valve of the cycle gas are continuously removed in order to enrich the gaseous reaction products to avoid in the plant. Via the line S, the resulting Loss of inert gas replaced. If necessary, the fresh gas can already be supplied with a certain content of non-decomposable gases and condensed through the pipe U are fed. It is also possible to remove the foreign products from the exhaust gas removed at S to remove in a known manner and the remaining gases to the system, for example at a point with low drudces or via the compressor U again.

The circulation of the liquid can, as Fig. 1 shows, after Mammoth principle. because the gas permeated column in absorber B is specifically lighter than the content of the reaction space A. The difference in height between the mirror S1 the bubble-free liquid in the separator C and the level L in the vessel D. circulation through the system.

A regulation is through the valve X of the bypass line R between the return pipe P and the lower end of the absorber B possible. When the resistances of the cooler 0 and the von-poorer S are large, the (dashed line) can be used to overcome them pumps Q or T or both can be arranged together. Using with two pumps it is practically impossible to have exactly the same delivery rate to be kept large, so that in the course of time the standing heights in the vessels C and would change D in an inadmissible manner. To avoid this, you can, for example either via a small additional preheater, to compensate for an outflow from C. lead to a small partial flow of the liquid or the delivery rate of one of the pumps Control from the level of vessel D with a level regulator.

To generate the cycle, it is also possible to use the liquid to suck in through the cooler O with a jet pump that uses the cycle gas as the working medium is operated. In Fig. 2 this mode of operation is shown in a section from Paragraph 1 shown. The injector Y works particularly well when the cycle gas is under higher pressure, so that due to its density a considerable pulse transmission to the liquid to be pumped is possible.

In order to reduce the consumption of heating and coolant, in known Way in the A heat exchanger can be switched on. the Heat of reaction is generated by cooling the reaction vessel (not shown) from the outside or by built-in snakes and the like in a known manner. If the temperature increase experienced by the liquid in the reaction chamber is within the allowable range for chemical reasons, so the heat dissipation with the cooler 0 can be done alone.

The discharge of the liquid containing the reaction products takes place at VL. At V2 there is fresh liquid, possibly catalysts and reactants are included.

In the absorber B, the liquid is loaded to a greater or lesser extent all gases in the mixture.

The higher the individual partial pressures, the greater the respective quantities and the corresponding solubility coefficients are and the lower the absorber temperature t2 lies. At the reaction temperature tl, which the circulating liquid after Assuming flowing through the preheater N would be the total pressure of all dissolved gases higher than the total pressure of the cycle gas in the separators connected to one another via E. C and D; it must therefore escape in the preheater A 'so much of the dissolved gases that an equilibrium is established. If the solubility of the inert gases is low, however the quantities that emerge are small in relation to those that remain in solution.

In the device shown in Fig. 1 for performing the In the process, the most difficultly soluble gas escapes in the form of small bubbles, which enter the head of the reaction chamber, ascend over the narrow tube E and unite at the mirror with the cycle gas under pressure P1.

Even if the partial pressure of the decomposable gases is in the bubbles should exceed the permissible limit, exists because of their small size Experience has shown that there is no risk of decomposition, as detonation waves are formed is only possible with a certain size of the gas-filled space. At her Combination with the cycle gas takes place immediately with a view to a safe Work required thinning. The liquid content of the separator above the The reaction space is in exchange with the cycle gas via its mirror and is therefore have a lower content of reactive gases. You keep your temperature t3 above the reaction temperature t2, it does not take part in the liquid cycle, because of its lower density, no convection phenomena can occur.

This is achieved by using a correspondingly narrow connecting line Z between 4 and D still supported. However, one can also be installed behind the preheater Arrange a special gas separator (not shown) that is connected to the gas space of the Separator D is connected and also flows through the cycle gas above the mirror is, and if necessary, the liquid a little before entering the reaction chamber subcool. This way of working is appropriate if you have one in the reaction chamber Want to allow temperature rise along the liquid path and thereby a gas excretion should be avoided.

A suitable choice of the absorber temperature can always be achieved that in the liquid in the reaction space the content of decomposable gases is close to Limit concentration is, so the highest possible space-time yields can be achieved. An exit the decomposable gases from the reaction space is through a corresponding setting of the freely selectable cycle gas pressure and suitable Cooling can be avoided to avoid excess temperatures.

The relaxation of the cycle gas can be done by throttling. But about the energy required for recompression to the actual working pressure to reduce the expansion in a known manner by a working machine make that mechanically when using a piston machine, when using a Turhine is expediently electrically coupled to the compressor.

The advantages of the method described are illustrated by examples explained for the implementation of reactions with acetylene, nitrogen as stable gas is added.

In Fig. 3 is the limit concentration c in Volumellatlteile of acetylene in acetylene-nitrogen mixtures as a function of total pressure p (measured in kg / cm2), which indicates the value at which with considerable initial energies no more disintegration can be initiated. The limiting partial pressure Pr results from Fig. 3 by multiplying the limit concentration c by the mixture pressure p.

For example, it has been found experimentally that the corresponding Limit concentration in the liquid at the reaction temperature is 100 Nccm / ccm and accordingly the reaction carried out safely at a content of 90 Nccm / ccm can be. If the; -sorption coefficient were a = 1.0 at the reaction temperature ccm / at ccm and if Henry's law were valid, then it would have to be with the usual Operation of the acetylene partial pressure 90 at, d. H. the working pressure of the mixture according to Fig. 3 at least 500 to 600 at, to the desired, maximum permissible To achieve concentration without exceeding the limit pressure in the gas phase will. Because you can get the acetylene for reasons the safety in pure form at the most with a pressure of 20 at the cycle gas can supply, this would have to relax continuously from 500 to 600 at to 20 at and again can be compressed to 500 to 600 at.

In the method according to the invention, a total pressure of 100 is sufficient At least noticeable amounts of acetylene can escape in the reaction space to prevent from the liquid loaded at lower temperature and that in the absorber to achieve the required saturation. The relaxation and recompression after the supply of fresh acetylene only needs a pressure ratio of 1: 5 instead 1:30 in the case described above. Since according to Fig. 3 an acetylene partial pressure of 25 at is allowed, to a concentration of 90 Nccm / ccm in the liquid To achieve the absorber temperature chosen so low that the Absorptiouskoefflzient 3.6ccm / ccm at. The system itself only needs an operating pressure of 100 and not 600 at to be measured, so that a considerable cost saving results.

To avoid excessive formation of bubbles in the preheater and for Compliance with the desired or permissible concentrations, it is useful to automatic Control organs to keep gas pressure, A mixture ratio, temperatures constant etc. to use.

The process can, for example, to reactions of acetylene and its homologues using application of nitrogen as a diluent or for Reaction of acetylene with carbon oxide, the latter at the same time as a diluent is used.

Example 81.4 1 of a circulated mixture of methanol and methyl vinyl ether, which contains 20 <> / o potassium hydroxide as a catalyst, are in an absorber of 5 1 content at 300 with an acetylene-nitrogen mixture that is 7.5 percent by volume Contains acetylene, saturated and in a cylindrical reaction space of 10 1 at Implemented in 1800. The solution is cooled to 300 and returned to the absorber.

In addition to resins, 6.33 kg of methyl vinyl ether are removed. The remaining methanol is replaced by fresh supplemented, returned to the absorber. The space-time yield is 15.2 kg / l and Day.

By saturation at low temperature (300), at which the solubility coefficient 3.0 / at compared to only 0.25 / at at reaction temperature (1800), the Space-time yield compared to the procedure with direct gassing with 500 / oigem Acetylene-nitrogen mixture at 20 at three times the value.

Because of the low acetylene content in the cycle gas it saves energy its main amount returned without relaxation and the amount required for the synthesis Amount of fresh gas added to a partial flow of the circulating gas expanded to 20 at, which is then compressed again to 200 at.

If one reacts in the same way ethanol or butanol with acetylene, in this way, similar increases in space-time yields are achieved compared with the low-pressure process.

PATENT APPLICATION 1. Process for the conversion of gaseous or vaporous Substances that can decompose exothermically under the reaction conditions in the presence of a liquid medium under pressure and when diluted with gaseous, not decomposable substances, characterized in that the substances after one them to below the explosion limits with the gaseous or vaporous, non-decomposable ones Has diluted substances in an absorber at a temperature below the reaction temperature temperature in the liquid medium in such an amount that its Concentration in the solution below the flammability limit, preferably close to it, lies, and that the solution is then in a reaction vessel at such a high Pressure is implemented that no or only insignificant at the reaction temperature Quantities of the dissolved gases or vapors escape.

Claims (1)

2. The method according to claim 1, characterized in that as admixing, Non-decomposable substances serve those with which the decomposable ones react should. 3. The method according to claim 1 and 2, characterized in that the The gas mixture passed through the absorber is expanded to such a pressure that of the to maintain the reaction process in pure or concentrated Form freshly fed substance no longer is detonatively decomposable, and that the gas mixture enriched with it is restored to the original pressure is compressed and returned to the absorber. 4. The method according to claim 1 to 3, characterized in that the The reaction space and the absorber are connected to one another on the gas side so that their liquid content is under the same pressure. Publications considered: Walter Reppe: »New developments in the field of the chemistry of acetylene and carbon monoxide "(1949), pp. 11 and 12.