DE1077192B - Process for carrying out exothermic catalytic chemical reactions - Google Patents

Description

The invention relates to a process for the continuous implementation of exothermic, catalytic-chemical Reactions with a relatively high heat of reaction and strives to be as complete as possible Compensation of temperature fluctuations during the reaction. With the invention, the temperature the reaction zone can be kept constant over its entire length to such an extent as has been the case up to now was considered impossible.

The method in question for carrying out a reaction under isothermal conditions is particularly advantageous in catalytic reactions. To be particularly effective, most catalysts require that the temperature be kept within certain narrow limits. If the temperature is too low, the reaction rate will be inadequate, and if it is too high, the catalyst may be damaged or destroyed, and undesirable side reactions may also occur. In order to maintain isothermal reaction conditions, it is necessary to dissipate all of the heat of reaction through the walls of the reaction vessel. In the following description, “walls” not only mean the outer walls of the apparatus, but primarily also all cooling walls that are arranged within the reactor itself, e.g. B. built-in cooling pipes. If the heat of reaction occurring in the unit of time is denoted by W and the heat continued in the unit of time as q, the following equation can be set up as the first condition for an isothermal course of the reaction:

W = -q (1)

This condition only guarantees adequate overall cooling, but does not contain any information about the speed with which the heat is carried away at each individual point along the entire length of the reactor. If the reactor consists of pipes or channels through which the reaction components pass, and if the coolant is outside the pipe walls, the following equation applies as the second condition when considering individual small sections of pipe length L according to (1):

dg ~ äL

It must be noted, however, that it is by no means necessary for the practice of the invention it is necessary that the reactor be tubular, but it can have any shape.

Condition (1) only prescribes that the temperature at the exit of the reaction zone be the same Procedure for implementation

exothermic catalytic chemical

Reactions

Applicant:

Dr.-Ing. Herbert PA Grudge,
Mölndal (Sweden)

Representative:

Dr.-Ing. A. ν. Kreisler and Dr.-Ing. K. Schönwald,
Patent attorneys, Cologne I7 Deichmannhaus

Claimed priority:
Sweden from January 21, 1953

Dr.-Ing. Herbert PA Groll, Mölndal (Sweden),
has been named as the inventor

should be the same as at the entrance, but it does not exclude large local deviations from the desired temperature

door during the flow of the reaction components through the pipe. Condition (2), on the other hand, prohibits such deviations and should therefore, if it can be met, just give the ideal reaction conditions.

It is well known that endothermic reactions are easier to regulate than exothermic reactions. The first-mentioned reactions have the significant advantage that they tend to be automatic to stabilize the temperature when the temperature conditions are disturbed. This is based on the fact that the rate of reaction rises and falls with temperature, and thereby the rate automatically and effectively adapts to the heat consumption depending on the heat input. That scored thermal equilibrium is therefore stable in endothermic reactions. For exothermic reactions on the other hand, an inherently unstable thermal equilibrium must be maintained through precise external control will. If the cooling is insufficient, the reaction rate will both increase also the development of heat, so that a "vicious circle" occurs in the temperature and the rate of reaction drive each other higher and higher and you have complete control over the reaction

90Ϊ 759/401

loses all sales. Just the opposite Progression occurs when the cooling rate is too fast, since the reaction does not proceed in this case can.

Regarding the control and regulation difficulties, exothermic reactions can result in the following Classes are divided into:

Class I. Reactions that hardly require temperature control as they have good yields at so high temperatures within such a wide temperature range and using a heat-resistant one Catalyst provide that it is not necessary to cool the reaction zone from the outside. A typical example of reactions in this class is the combustion of ammonia to form nitrogen oxide. The material temperature in this case is controlled by the mixing ratio between Ammonia and air adjusted.

Class II. Reactions due to their nature and due to the nature of the catalyst used must be carried out within a temperature range in which the chemical equilibrium no complete conversion allowed in a single pass through the reactor, which is why a large part of the reaction components leaves the reactor in an unchanged state and in circulation must be returned. If here the reaction temperature is due to inadequate conduction As the heat rises, the equilibrium becomes even less favorable and thus prevents progress the reaction, unless a lower temperature is set again by cooling. This self-regulating effect is extremely beneficial and contributes significantly to the To facilitate the implementation of the reaction, as in this way one never loses control over the course of the reaction.

A typical example of a reaction belonging to this class is the synthesis of ammonia, in which the cycle principle described above is applied. Another reaction from this class is that Water gas reaction, the so-called carbon oxide conversion, which is applied to carbon dioxide and to obtain hydrogen from carbon monoxide and water vapor. In this case, the recirculation can are not used, and in practice several catalyst layers are used instead with intermediate cooling to keep the carbon dioxide content of the reaction gases as effective as possible to belittle. The one from each pass or from each layer in the reactions described above yields obtained and the capacity of the apparatus are completely dependent on the effectiveness, with which the heat is conducted away.

Class III. Reactions that are carried out with particularly temperature-sensitive catalysts and / or tend to turn into undesirable side reactions. This type of response is quite common within organic chemistry. Typical examples of this are given in the Order of increasing difficulty in mastering the reaction are hydrogenation, oxo process, the syntheses of methanol and isobutanol, partial hydrogenations, selective oxidations, the Fischer-Tropsch synthesis, the oxidation of naphthalene to phthalic anhydride and the oxidation of ethylene to ethylene oxide. The control of the last three reactions mentioned is usually considered to be so difficult that this has so far only been satisfactory through special measures, such as the use of thermostatic, rapidly stirred and cooled salt baths, cooling arrangements with boiling Cooling liquids, internal cooling or carrying out the reaction under strong dilution with gas, the is circulated, could be realized.

The invention can be used with particularly great advantage in all reactions of classes II and III will. According to the invention you can at

ίο the cooling speed using suitable equipment set so that it exactly meets the conditions of equations (1) and (2) above, without having to take particularly expensive special measures, such as a cooling arrangement with boiling cooling liquids and the like. In fact, the latter method is far from being as effective as it is generally speaking looks at. If you only keep the temperature of a cooling liquid thermostatically constant holds, this is no guarantee that the reaction temperature itself will be high above the temperature of the coolant also increases, especially at those points where the reaction rate is greatest.

The rate of the reaction depends on the concentration of the reaction components in the reaction zone and on the rate constant k, which is generally a function of the temperature, on the order of the reaction and on the activity of the catalyst. The order of the reaction depends on the reaction mechanism, which in many cases has not been fully elucidated, especially when the reaction is carried out on solid catalyst substances. However, as is known, the speed can be determined by measurement, whereby the reaction order can also be determined. Experience has shown that most catalytic reactions are of the first or second order. If the mechanism is complicated and the speed of a plurality of simultaneously occurring elementary processes is determined, the measurement result can indicate a so-called mixed order between, for example, zero and first order or between first and second order. On the basis of these values found through measurements and / or calculations, one can also determine the magnitude of the conversion rate during each point in time of the contact time in order to derive the function for the rate with which heat is generated at the individual points in the reactor with satisfactory accuracy. With others

Words: The values for - ^ = - can be used as a function

dL

of L can be expressed by means of an equation or a curve.
Fig. 1 shows the similar for all reactions

d W
Curve of the dependence of the value -j- on L. The

best results in cooling are obtained.

, if one, like m this tigur, for-rf- and -j —- the same

DO fitjL CL L,

has large values with opposite signs, so that the temperature deviations are either completely avoided or at least can be reduced to a minimum. The reaction temperature is increased to this way kept constant at the optimal value. The cooling method that works best the intensity gradient required with regard to the function of the reaction rate adapts, consists in the fact that the cooling is carried out with a coolant that in cocurrent

5 6

and parallel to the direction of flow of the re-dissipated amount of heat at every point equal to zero,

action mix is conducted. d. That is, there is no unbalanced residual heat left

For example, for an ideal gas reaction one or the other direction can be left which the

Second order for the reaction temperature at every point to deviate from the target value

,. ,, "Τ- dW. 5 could.

heat emitted from the action room - an _{Under suitable structural} conditions,

Complicated equation can be determined, which is known- which enable the application of the invention, can always be an exponential function and in which equation (2) simply fulfills the concentration of the reaction as a variable, that the rate of flow of the in a participant α and b, the nature of the catalyst, which is separated from the path of the reaction mixture, and the temperature-dependent speed of the co-current flowing coolant and the constant k and the quantities of the gas speed that determine the reaction time at its inlet temperature (the two variables) ν and which are controlled at the same time in such a way that the dimensions of the reactor are included. In practice, if the reaction temperature is predefined, the conditions are usually so complicated that the equation does not calculate theoretically 15 setpoints along the flow path of the reaction, but rather a mixture of the respective change in the cooling effect, at most with semi-empirical methods of the effect at one end of the pipe by varying one variable possibility can be approximated. Other variables can also appear in it, followed by a variation of the other variables. One being, this second variation being the disorder- the. . . . , _T _ ... dW _rr η j 20 cooling effect at the other end of the reaction tube characteristic curve for - ^ - shows curve 1 which runs in the opposite direction

Fig. 1. In order to achieve sufficient regulation according to the P f ~

It is now quite obvious that curves 1 and 2 of FIG. 1 must therefore be brought about

Change even only one of the variables, for example the parallel direct flow of the coolant in such a way α or b or k, can be carried out by fluctuations in the catalytic converter in such a way that the flow

activity, which, as is well known, usually counteracts the trace speed of the coolant and its tempe-

is very sensitive to impurities, the temperature on entry into the cooler of the reactor is very

,. , _T _ ... dW. ,, rr λ η ■ quickly, effectively and independently of each other within

run the curve for - ^ unexpectedly and intermittently _{] mlb of the areas for the} temperature and the currents

can change. 30 ming speed, the one in question

The invention is now based on the following detection reaction are required, can be regulated
lungs: In order to be able to achieve this, it is particularly

1. Also the easier to calculate equation for moderate to circulate the coolant, e.g. B. the one in direct current with the reacting means of a pump, a blower or an injector, Gases flowing coolant at each point 35 and further the coolant through a cooling arrangement The amount of heat taken is an exponential with sufficient capacity to conduct the im function in which the heat transfer coefficient, the circulated coolant even at the highest specific heat of the coolant, the required flow velocity dimension of the cooling duct and finally the volume rate to cool the lowest required temperature, speed and the temperature difference between the re- 40 At the same time, a bypass line is created for the action temperature and the inlet temperature of the warmed coolant is provided, which is so inertia-free Coolant as a parameter. In this as desired by means of a valve or a throttle function however, the first three of said flap can be controlled. Preferably will Sizes due to the structural design of the air or cooling water directly as a coolant on the device and the choice of coolant determined. 45 turned. In this case it may be unnecessary to use the

2. Surprisingly, it has now been shown that it recirculates coolant and cools it solely by varying the rate of flow and one can be content with only one and the inlet temperature of the coolant, ie circuit line for the cooling heated in the reactor through the last two mentioned Sizes that are to be provided for the water or the heated air in order with ■ c> sjtj ^ uzcxi-ikfs da „. . -, .. as required speed and effectiveness, the ExjWiSirtal function - may be important, _{temperature of the} coolant entering the system

it is possible to regulate the reaction temperature in the reaction occurs by means of the throttle described above.

keep space at a constant value. Actualize.

Another useful method for executing both variables, the shape and the inclination of the method according to the invention, consists in following the curve for the heat dissipated at each point - that both the regulation of the temperature of the da ._ ,. .__ ". ,,. Coolant as well as the regulation of the flow rate ^ (Fig. 1, curve 2) the previously discussed speed of the coolant with the help of automatic

-r--, .. dW . .., _. ,. control bodies. Whose

Curve for - ^ to be applied with sufficient accuracy _{6o pulse generator be} installed _at the following locations:

fit and thereby the disturbances that are in the

Curve 1 of the figure appear through corresponding A. Within the area for the maximum temperature change the curve 2 intercept. This is ratur in the flow of the reaction mixture through the the curve 2 always as a mirror image of the curve 1 is maintained on the reactor, very close to the inlet of the cooling, so that in this simple way 65 means in the cooler of the reactor. At this at any point and at any time in equation (1), a suitable temperature control

Sr, iiu -d j ^dW dq i / ■■ 1, · 1 · arrangement provided, which is transferred to an instrument

established demand - ^ = - ^ actually automatically f- with _Hcher ^ ^ _{ang joined ISTJ we} i _che s

The temperature of the coolant in the radiator can be met with sufficient accuracy

can. This regulates the sum of the occurring and 70 of the reactor entering.

B. In or near the outlet line for the reacted gas mixture from the catalyst zone. At At this point a similar device is attached, the impulse of which is transmitted to an automatic control instrument acts that regulates the flow rate of the coolant to the cooler of the reactor.

At the beginning of the life of the catalytic converter, the regulating instrument at A must preferably be set to maintain the maximum temperature that can be endured by the catalytic converter without it being able to be damaged by overheating. The regulator instrument at B is set to a temperature which is slightly higher than the lower temperature limit for achieving a satisfactory conversion. In certain cases, especially towards the end of the useful life of the catalyst used, it can be useful to set this instrument to a point close to the upper permitted limit.

During the later stages of the life of the catalyst, the set temperature at said point A can be increased or decreased and / or the control point can be moved further into the reactor. It is impossible to be definite as to which of the measures mentioned are the most appropriate in order to obtain the best results, since this depends to a large extent on the nature of the reaction, the type of catalyst used and the reason for the gradual deterioration of the catalyst. This can e.g. B. due to poisoning and / or sintering or other changes to the active surface of the catalyst. The optimal working conditions are therefore best to be determined empirically, but within the specified limits.

During the life of the catalytic converter, the coolant can also continue to enter the Relocate the reactor in order to avoid excessive cooling of such places of the catalyst, the activity of which has suffered.

Such protection against undesired cooling can also be achieved by that a protection arrangement, e.g. B. an insulating shield, gradually or periodically further between the flowing coolant and the parts of the catalytic converter that are to be protected is inserted. You can also heat the catalyst very close to the entry of the reaction components, so that the reaction is not chilled to death. A particularly convenient way of practicing the invention is that one with not cooled or at least not cooled to a significant extent catalyst filled initial zone is provided. This procedure is particularly useful in those cases in which in view of the risk of decomposition it is undesirable or impossible to heat the reaction mixture up to the desired reaction temperature in advance. In the initial zone the reaction components react on the catalyst more slowly than at the usual reaction temperature. The heat of reaction heats the reaction mixture to the optimal temperature. The cooling must start immediately at the point where the correct reaction temperature has been reached. One can use organs to regulate the length of the induction zone provide e.g. B. shields that can be moved, and the like., As in the preceding is described.

Another convenient way of carrying out the invention is that the reaction mixture and / or one or more of its components can be used as a coolant.

For example, in the synthesis of ammonia, a mixture of nitrogen and hydrogen can be used or even just the nitrogen in such a way through the cooler of the reactor with that for the synthesis necessary pressure let pass that the rate of flow and the temperature of the cooling gas independently of one another and regardless of the amount of the reaction mixture caused by the catalyst flows, to be regulated.

In the synthesis of phthalic anhydride by oxidation of naphthalene with air is preferred Air is used directly to cool the reaction tubes in which the catalyst is located. Man can also place the catalyst between the pipes and let the air flow through cooling pipes, which run with the same gaps and parallel to the direction of flow of the reaction gases. Around to bring about a better distribution of the cooling gas and a better heat transfer, the cooling tubes can be provided with rods inside, the struts or spiral ribs own. The linear velocity and the flow resistance of the Gas increases and thereby the even distribution of the gas on all pipes and the heat transfer relieved. The cooling tubes or the cooling space around the catalyst tubes can also be used for the same purpose fill around with random packing. These can preferably be made of a material with high thermal conductivity exist and z. B. balls or pieces of metal, such as aluminum. The last one mentioned Method is particularly useful in those cases in which a particularly high heat transfer coefficient is desirable.

So that the coolant flows parallel to the direction of flow of the reaction mixture, one can according to the invention, preferably arrange guide rails and manifolds parallel to the direction of flow, in order to prevent disturbances from thermal convection in this way. If you have a fixed bed of catalyst and a fast flowing reaction mixture is used, this is usually left pasiseren through the catalyst bed in descending direction in order to avoid an undesired swirling of the To prevent catalyst, which would be easily destroyed by mechanical means.

When the coolant descends the space between the catalyst tubes happens what is necessary in this special case, the heat convection could change the direction of flow disturbing influence and thereby give rise to undesired eddy currents. In this case it is it is particularly useful to use directional organs and the like. For this purpose can one also roughly in the manner indicated above solid packing in the mentioned space arrange. The filling increases the flow resistance, which makes it more uniform Distribution of the current achieved over the entire cross section of the cooler.

Appropriate organs can also be provided to prevent the accumulation of gases or vapors in the cooler when using a downward flow of liquid coolant. The cooler of the reactor can for example be built according to the principle of communicating vessels. if

The flow resistance in the cooler requires a high differential pressure, valves can be used to escape of the gas can be provided at the upper end of the cooler. The valves can be automatic by means of float valves or the like. Finally, one can also use devices for exploitation the heat of reaction. If the,! Heat is not completely ^ action mixture can be added to the desired reaction temperature, it is possible that the to use otherwise used heat to heat waste heat boilers, economizers, etc.

The method according to the invention can not be used on fixed catalysts limited, but the invention can also be applied to so-called fixed fluidized bed catalysts be, d. H. then if only an insignificant amount of the catalyst from the gas at his Exit from the reactor is taken. In this case, it is particularly advantageous that the reaction mixture in the reactor and the coolant in the cooler are directed parallel to each other upwards flow, since the temperature gradient of the coolant in the height direction no risk of disturbance for brings the steady flow of coolant through undesired heat convection with it.

In FIGS., 2 and 3, two exemplary embodiments of systems for carrying out exothermic Reactions shown by the method according to the invention.

In the system according to FIG. 2, the reaction passage 1 is designed as an elongated channel surrounded by a cooling jacket. The reaction mixture is fed through line 2 to a heat exchanger 3, in which it is heated by heat exchange with the reacted mixture flowing out of the reaction passage. From the heat exchanger 3, the reaction mixture is passed through a line 4 to the inlet 5 of the reaction mixture into the reaction passage. The first section 6 of the reaction passage 1 forms the initial zone for the reaction and is expediently adjustable, as will be described below. The reacted mixture leaves the reaction passage at 7 in order to be fed to the heat exchanger 3 and the extraction line 9 via the line 8.

The coolant circuit through the cooling jacket 10 is brought about by means of a coolant pump 11, from the pressure side of which a line 12 leads to a control valve 13 for the amount of coolant. The control valve 13 is connected to the coolant inlet 15 in the cooling jacket by means of a line 14. from the coolant extraction 16 at the other end of the cooling jacket is the coolant via a line 17 passed to a heat exchanger 18 in which the heat of reaction absorbed by the coolant can be exploited in any suitable way, for example as an exhaust gas boiler is trained. The coolant is led from the heat exchanger 18 to a discharge line 19; it is however, it is also possible to recirculate the coolant to the coolant pump 11, in which If it is fed to the suction side of the pump 11 via a return line 20. If that Coolant does not circulate but goes away through the discharge line 19, new coolant is drawn from the supply line 21 is supplied to the suction side of the pump 11.

From the line 17, which starts from the coolant outlet 16 in the cooling jacket 10, there is a line 22, seen in the direction of flow, branched off in front of the heat exchanger 18. In the branch line a regulating valve 23 is used for regulating the coolant temperature. In the embodiment According to FIG. 2, this regulating valve consists of a throttle arrangement which, if too high Temperature is closed. The regulating valve 23 is on the drain side via a line 24 with the Suction side of the coolant pump 11 connected. Using the regulating valve, one of the Temperature-dependent admixture of warm coolant to that supplied to the suction side of the pump 11 causes fresh or cooled in the heat exchanger 18 coolant.

The automatic regulation according to the present invention comprises a pulse thermometer 25, the is arranged immediately behind the induction zone of the reaction passage 1. The length of the through heat insulating Shielding of the reaction passage from the initial zone 6 formed by the cooling jacket is adjustable with the aid of a heat protection 26 which can be displaced in the longitudinal direction of the reaction passage. This can either only have a heat-insulating effect or it can also be provided with compensation heating be.

The pulse thermometer 25 is also slidable in the longitudinal direction of the reaction passage to easily brought into the correct position in relation to the end of the initial zone in every position of the thermal protection to be able to. The pulses from the pulse thermometer 25 are transmitted via a line 28 to a pulse relay 29 supplied, which in turn, via a connection 30, the regulating valve 23 for the coolant temperature controls. This results in an automatic adaptation of the amount supplied to the coolant pump 11 Mixture of warm with fresh or cooled coolant depending on the temperature at the Measuring point 25 comes about.

A pulse thermometer 27 is also located near the exit end of the reaction passage. the Pulses of the pulse thermometer 27 act via a line 31 on a pulse relay 32, which via a Connection 33 controls the regulating valve 13 for the amount of coolant. This brings about the invention intended regulation of the amount of coolant depending on the temperature of the reaction mixture at the outlet end of the reaction passage comes about automatically by opening the regulating valve 13 further when the temperature is too high and when it is closed is closed lower more and thus increases the amount of coolant supplied to the coolant outlet or is reduced.

Fig. 3 shows a system for carrying out exothermic reactions of the type in which a plurality of cooling passages 10a is inserted into a relatively large reaction passage 1 α. The conditions for the heat flow at each point of the reaction passage to the next cooling tube the same as if the reaction passage were divided into as many partial passages 1α as there are spaces between the cooling passages. The flow path of the reaction mixture in this embodiment is only through the inlet 5 a and the outlet 7 a indicated, but can of course also in this case a heat exchanger accordingly the heat exchanger 3 according to FIG. 2 for preheating the reaction mixture.

In this exemplary embodiment, the coolant is completely circulated, with the coolant pump lic · immediately after the coolant emerges

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16 α is arranged from the coolant space 10 α. the Coolant pump 11a pumps the coolant through line 17a to heat exchanger 18a, in which the coolant through a secondary coolant, e.g. B. air or cooling water is cooled down. This Secondary coolant flows from line 34 through regulating valve 23 a via line 35 to the heat exchanger 18 a and leaves this through the outlet 36. By varying the amount of secondary coolant with the regulating valve 23 α is also the temperature of the circuit coolant in the Heat exchanger 18 a regulated. The circulation coolant cooled to the desired temperature leaves the heat exchanger 18 α through line 12 a. Its amount is controlled by means of the regulating valve 13 α regulates that the desired amount through line 14 a to the displaceable distributor head 38 can be recirculated, in which the pipes 39 surrounded by the insulation 26 α are installed. In The coolant flows through these tubes through the coolant inlets 15 α to the coolant passages 10 α. In These coolant passages have rods 37 to increase the linear velocity of the coolant and prevent heat convection.

The automatic regulation for the valves 23 α and 13 α is in principle the same as in FIG. 2, ie the displaceable pulse thermometer 25 a arranged near the entry zone of the reaction chamber is located behind the induction zone 6 a. The induction zone hardly exists in FIG. 3, since the displaceable arrangement, which comprises the distributor head 38, the thermometer 25 α, the pipe 39 surrounded by the thermal protection 26 α, the coolant inlet 15 α and the rods 37, is as high as possible Position are drawn. If a longer induction zone is desired, the whole arrangement is shifted downwards. The heat-protected reaction zone can be considerably lengthened during the operating period in that the arrangement is additionally shifted downwards to the same extent as the inactive uppermost catalyst zone gradually grows due to poisoning or the like.

The pulse thermometer 25 α acts via the line 28 α on a pulse relay 29 α, which in turn controls the regulating valve 23 a for the coolant temperature via the connection 30 α, while the pulse thermometer 27a located near the exit point of the reaction chamber acts on a pulse relay via a line 31 α 32 α acts, which in turn via the connection 33 σ the regulating valve 13 a. controls for the amount of coolant.

From the two embodiments it should be apparent that the automatic regulation according to the Invention exercised regardless of the design of the cooling system in different systems can be..

It should be particularly emphasized that with reactions that are particularly difficult to control or with those in which the position of chemical equilibrium does not exist. quantitative turnover allows that Reaction mixture can be wholly or partially recycled, possibly after removal of the desired product. Also dilution by inert gas or steam and others in technology known means for reducing the intensity of the heat generation on the catalyst can simultaneously with and regardless of the application of the invention described above.

example

According to the previous process, 150 kg of naphthalene per hour were oxidized with 30 to 35 kg of air per kg of naphthalene at reaction temperatures between 360 and 450 ° C. to produce phthalic acid. The heat of reaction to be removed was 540000 kcal per hour. The oxidation was carried out in three thousand square tubes which were cm long and had a cross section of mm ² . The tubes were filled with catalyst at a height of cm, so that the catalyst space in the individual tube was 300 cm ³ , a total of 9001. It was cooled at 370 ° C. with 111 boiling mercury. The life of the catalyst was 9 months; the yield 90 to 95% of the naphthalene used.

According to the invention, the same starting materials are implemented in ninety tubes 8 m long and 40 mm in diameter (1250 mm ² cross section). Air is used as the coolant. According to the ongoing tests, the life of the catalyst is more than 18 months, and the yield of pure phthalic acid is 95 to 100% of the naphthalene used.

Claims (3)

Claims. 1. Process for carrying out exothermic, catalytic reactions in flowing gas or Liquid phase with dissipation of the heat of reaction through indirect heat exchange with a coolant, the temperature and quantity of which are regulated independently of one another, thereby characterized in that for the most complete possible compensation of temperature fluctuations during the reaction both the inlet temperature and that in the unit of time .by the cooling arrangement in a circuit separate from the path of the reaction mixture, the amount of coolant flowing in cocurrent (the two Variables) are controlled at the same time in such a way that for compliance with. predetermined reaction temperature setpoints along the flow path of the reaction mixture, the respective change in the cooling effect at one end of the pipe followed by a variation of the other variable by variation of one variable, this second variation being the disturbance of the cooling effect is opposite at the other end of the reaction tube. 2. The method according to claim 1, characterized in that the inlet temperature of the coolant depending on the reaction temperature in the vicinity of the entry of the reacting Substances in the reaction zone and the amount of coolant depending on the reaction temperature in the vicinity of the exit of the reacting Substances from the reaction zone are preferably regulated automatically. Considered publications:
German Patent Nos. 564 042, 853 441, 241; Swiss Patent No. 145 140; Uli mann, encyclopedia of technical chemistry, 3rd edition, Vol. 1, 1951, p. 267. 1 sheet of drawings © 909 759/401 3. 60