DE102004008573A1 - A process for removing carbonaceous residues in a reactor - Google Patents

Abstract

The present invention relates to a process for the removal of carbonaceous residues in a catalyst containing a solid catalyst for the catalytic gas phase oxidation of unsaturated hydrocarbons, wherein the deposited carbonaceous residues continuously with an oxygen-containing gas and water, preferably water vapor,
at a temperature T _reactor in a range of 260 ° C to 500 ° C and
- At a pressure P _reactor in a range of 0.8 to 20 bar
be brought into contact with forming a carbon dioxide or carbon monoxide-containing exhaust gas
and the exhaust gas containing carbon dioxide or carbon monoxide is continuously removed from the reactor. The invention also relates to a device for catalytic gas phase oxidation of unsaturated hydrocarbons.

Description

The The present invention relates to a process for removing carbonaceous material Residues in one a catalyst containing solid catalyst for catalytic Gas phase oxidation of unsaturated Hydrocarbons and a device for catalytic gas phase oxidation unsaturated hydrocarbons.

Unsaturated hydrocarbons can through catalytic gas phase oxidation to form unsaturated carboxylic acids be oxidized. Of particular technical importance in this context the catalytic gas-phase oxidation of propene via acrolein to acrylic acid and the oxidation of isobutene to methacrylic acid.

at the catalytic gas phase oxidation of propene to acrylic acid an acrolein-containing gas formed by the oxidation of propene in the gas phase by means of a molybdenum and bismuth-containing multimetal oxide oxidation catalyst in a first process stage is obtained, in a second process stage also by means of a molybdenum and bismuth-containing multimetal oxide oxidation catalyst in Acrylic acid transferred. at the synthesis of methacrylic acid from isobutene, methacryolein is formed in a first stage of the process, which oxidizes to methacrylic acid in a second stage of the process becomes.

The Oxidation of the unsaturated Hydrocarbons usually take place in special reactors containing a catalytically active fixed bed. For example In the case of the synthesis of acrylic acid from propene, a propene-containing gas mixture transferred to a first reactor, in the propene is catalytically oxidized to acrolein. About one Outlet in first reactor, which is connected to a second reactor passes the now containing acrolein and also amine acid gas mixture in the second reactor in which the acrolein is catalytically oxidized to acrylic acid becomes. The now acrylic acid containing gas mixture then passes through an outlet in the second Reactor in further treatment devices, in which a separation by-products from the gaseous reaction product containing the acrylic acid he follows.

One the problems with the gas phase oxidation described above unsaturated Hydrocarbons is that, especially in the first stage of the process after a long time Operating time of the reactor in addition to the desired oxidation products Considerable amounts of carbonaceous residues are formed on the surfaces of the reactor, in particular in the region of the outlet or in the catalytic deposit active fixed bed.

The Deposits in the outlet of the Lead reactor to an increasing pressure drop in the reactor system, which is disadvantageous affects the reactor power. The deposition of carbonaceous residues in the catalytic active fixed bed impaired detrimental to the reactor performance, since the deposits in the pores clog the catalysts. In addition to the impairment of reactor performance, these lead Deposits also to increased energy consumption, there the gaseous Eduktstrom ever stronger must be compressed to still in sufficient quantity in the reactor to be able to be introduced. It is therefore necessary to use the catalyst after a certain time to renew or the carbonaceous deposits in the catalytic active fixed bed and on the rest surfaces of the catalyst to remove sufficient reactor power maintain.

The removal of the carbonaceous deposits - hereinafter referred to as "coke" - is carried out according to the prior art by adding oxygen to the reactor through which nitrogen flows in such a way that the temperature in the catalyst bed increases to a predetermined range in DE 101 61 665 A1 described.

These However, the procedure requires a lot of time since the when burning the Coke occurring amount of heat per unit time spontaneously can arise. It is therefore a careful and slow metering of airflow / oxygen flow required to be released per unit time heat lead away to be able to and thermally not to overload the material of the reaction tubes.

Of the The present invention was therefore generally based on the object, to overcome the disadvantages resulting from the prior art. Especially the present invention was based on the object, the disadvantage So far, the slow and time-consuming procedure for Overcome Decoken.

Especially the present invention was based on the object, a method indicate with which it is possible is, in the catalytic oxidation of unsaturated hydrocarbons carbonaceous deposits formed in the gas phase the surfaces the reactor and the catalytically active fixed bed if possible low temperatures and as possible to remove short burn times.

moreover it was an object of the invention to under as possible moderate conditions with as possible little time both during operation of the catalyst increasing over time flow resistance in the reactor as well as the reduced catalyst performance by a appropriate process to increase again or improve.

A Another object of the present invention was to provide a device to provide, with the unsaturated Hydrocarbons can be catalytically oxidized in the gas phase and the one possible gentle removal of carbonaceous deposits on the surfaces the reactor and the catalyst allows.

These Tasks are accomplished by a process for removing carbonaceous matter Residues in one a catalyst containing solid catalyst for catalytic Gas phase oxidation of unsaturated Hydrocarbons and by a device for catalytic Gas phase oxidation of unsaturated hydrocarbons, as each in the independent claims stated, solved. Further refinements and developments are the subject of respectively dependent Claims, each applied individually or combined with each other can.

• – bei einer Temperatur T_Reaktor in einem Bereich von 260°C bis 500°C, bevorzugt in einem Bereich von 300 bis 450°C und darüber hinaus bevorzugt in einem Bereich von 340 bis 380°C,
• – bei einem Druck P_Reaktor in einem Bereich von 0,8 bis 20 bar, bevorzugt in einem Bereich von 0,9 bis 10 bar und darüber hinaus bevorzugt in einem Bereich von 1 bis 5 bar

unter Bildung eines Kohlendioxid oder Kohlenmonoxid enthaltenden Abgases in Kontakt gebracht,
wobei das Kohlendioxid oder Kohlenmonoxid enthaltene Abgas vorzugsweise kontinuierlich aus dem Reaktor entfernt wird.In the inventive process for removing carbonaceous residues in a catalyst containing a solid catalyst for catalytic gas phase oxidation of unsaturated hydrocarbons, the deposited carbonaceous residues are preferably continuously with an oxygen-containing gas and with water, preferably in the form of water vapor,

• At a temperature T _reactor in a range from 260 ° C to 500 ° C, preferably in a range from 300 to 450 ° C and moreover preferably in a range from 340 to 380 ° C,
• - At a pressure P _reactor in a range of 0.8 to 20 bar, preferably in a range of 0.9 to 10 bar and moreover preferably in a range of 1 to 5 bar

contacted to form a carbon dioxide or carbon monoxide-containing exhaust gas,
wherein the exhaust gas containing carbon dioxide or carbon monoxide is preferably continuously removed from the reactor.

The The pressure data given above represent absolute pressure values represents.

In a preferred embodiment the method according to the invention The carbonaceous deposits are pulsed with the water, preferably with the water vapor, brought into contact. Preferably is doing This pulsed contacting of carbonaceous deposits realized with the water that the preferably continuously the oxygen-containing gas introduced into the reactor preferably contains the water in the form of water vapor is added in a pulse-like manner. Pulsed addition of water or water vapor in the context of the present invention means that the water or water vapor is not continuous the oxygen-containing gas is added, but that the addition takes place in time-limited time intervals. Accordingly, the Water vapor concentration in the oxygen-containing gas during the entire decoking process is not constant.

In a preferred embodiment the method according to the invention The water is the oxygen-containing gas in an amount in one area from 0 to 50 vol%, preferably in a range from 1 to 20 vol% and above In addition, it is preferably in a range of 1.5 to 10% by volume on the total volume of oxygen-containing gas added.

It is according to the invention furthermore preferred that the time interval between two pulses in one Range from 5 minutes to 200 hours, more preferably in one Range of 10 to 150 hours and beyond preferably in one Range of 20 to 100 hours. The distance between two pulses is essentially by the total duration of the decoking process limited. As a time interval between two pulses is preferably the time interval between the maximum water addition of the Pulse i and the maximum of the pulse i following pulse i + 1 understood.

The Length of one Pulses are preferably in a range of 1 second to 24 Hours, more preferably within a range of 5 seconds to 10 hours and above more preferably in a range of 10 seconds to 1 hour.

The number of pulses in the process according to the invention is dependent on the duration with which the carbonaceous deposits are brought into contact with the oxygen-containing gas under the abovementioned conditions. In a preferred embodiment of the process according to the invention, the carbonaceous deposits are submerged with the oxygen-containing gas for a period in the range of 2 to 200 hours, more preferably in a range of 10 to 150 hours and more preferably in a range of 15 to 100 hours brought into contact with the abovementioned reaction conditions. Accordingly, the number of pulses, depending on the pulse length and distance of the pulses is preferably in a range of 1 to 100, particularly preferably 2 to 50 and is furthermore preferably 2 to 10.

The Control of pulsatile addition of water, especially regulation the amount of water added per pulse, the duration of the pulses as well of the time interval between the individual pulses can be above the Professional known valve systems are accomplished, for example computer-aided can be controlled.

It is still according to the invention preferred that both the amount of water added per pulse and the pulse length as well as the distance between two pulses in the course of the procedure, depending on the progress of the burning off of the carbonaceous residues, varies become.

The Water becomes preferred with the carbonaceous deposits in the form of steam brought into contact. This is done by bringing it into contact the carbonaceous deposits with the water by adding water the oxygen-containing gas is added, the water is the oxygen-containing gas, preferably in the form of steam. Furthermore The water can already enter the oxygen-containing gas before it enters of the gas is added to the reactor in the form of steam or else be supplied separately from the oxygen-containing gas to the reactor via a separate feed.

It is furthermore preferred according to the invention for the oxygen in the process according to the invention to be present in an amount in the range of 0.001 to 1 kg O ₂ / (h × 1 _catalyst bed volume), preferably from 0.01 to 0.5 kg O ₂ / (on average). h · 1 _{catalyst bed volume} ) and particularly preferably from 0.1 to 0.2 kg O ₂ / (h x 1 _{catalyst bed volume} ) is used. It is further preferred that at the beginning of Decokings first small amounts of oxygen are added and the amount of oxygen is increased in the course of the decoking process.

When oxygen-containing gas is preferably pure oxygen, air, oxygen enriched air or nitrogen enriched air Air is used, with air and nitrogen-enriched air especially are preferred. The air can in addition to the already existing gases (mainly oxygen, nitrogen and carbon dioxide) as well as other than nitrogen as inert gas Inert gases, such as carbon dioxide, are added. nitrogen and optionally further inert gases are preferably the air added in such an amount that the oxygen concentration in the oxygen-containing gas in a range of 5 to 20 vol%, preferably in a range of 7.5 to 17.5 vol%, and more preferably in one range from 10 to 15% by volume.

It is still according to the invention prefers that during contacting the carbonaceous residues with the oxygen-containing gas continuously the amount of carbon dioxide or carbon monoxide, preferably carbon dioxide and carbon monoxide Carbon monoxide, in the exhaust gas and the temperature of the solid catalyst be determined to the progress of the burning, the influence further water pulses on the burning process and the thermal Loading of the catalyst by the exothermic oxidation of the carbonaceous Monitor deposits to be able to.

The Determination of the amount of carbon dioxide or the amount of carbon monoxide takes place for example by gas chromatography or by IR spectroscopy, wherein a portion of the exhaust stream at defined intervals or but continuously a measuring device, which is a gas chromatograph or an IR spectrometer comprises, is supplied. In addition to the determination of the carbon dioxide or carbon monoxide concentration by gas chromatography or IR spectroscopy other measuring devices, such as specific gas sensors for determining the carbon dioxide or the carbon monoxide concentration can be used.

• – Es wird als sauerstoffhaltiges Gas ein Gemisch aus Stickstoff und Sauerstoff eingesetzt, wobei das relative Mengenverhältlnis dieser beiden Gase konstant, die eingesetzte Gasmenge jedoch im Verlaufe des Verfahrens erhöht wird. Da auf diese Weise zu Beginn des Decoking-Prozesses zunächst wenig, dann jedoch zunehmend mehr Sauerstoff eingesetzt wird, kann ein unkontrolliertes Abbrennen verhindert werden. Außerdem führt die steigende Gesamtgasmenge, insbesondere auch die steigende Sauerstoffmenge, zu einem verbesserten Abbrennen von Ablagerungen in Rohrleitungen, die besonders stark von Ablagerungen befallen sind.
• – Es wird als sauerstoffhaltiges Gas ein Gemisch aus Stickstoff und Sauerstoff eingesetzt, wobei die Gesamtgasmenge konstant, jedoch der Sauerstoffanteil kontinuierlich erhöht wird (und der Stickstoffanteil dementsprechend erniedrigt wird). Auch auf diese Weise kann ein unkontrollierter Abbrand zu Beginn des Verfahrens verhindert werden. Der steigende Sauerstoffanteil im Gasgemisch ermöglicht zudem bei fortgeschrittenem Abbrennvorgang ein Abbrennen von Ablagerungen auch in besonders verstopften Rohrleitungen.
• – Es wird als sauerstoffhaltiges Gas ein Gemisch aus Stickstoff und Sauerstoff eingesetzt, wobei die Gesamtgasmenge durch Erhöhung des Sauerstoffanteils im Verlauf des Decoking-Verfahrens erhöht wird. Auch in dieser besonderen Ausführungsform des erfindungsgemäßen Verfahrens wird durch den Einsatz geringerer Sauerstoffmengen zu Beginn des Verfahrens die Gefahr eines unkontrollierten Abbrennens verhindert.

In shell and tube reactors in which the oxygen-containing gas is passed through the catalyst-filled pipes, problems in burning the carbonaceous deposits in the reactor and in the pipes may be that the individual Reaktionsroher are provided differently with carbonaceous deposits, so that the Pressure drop over strongly clogged reaction tubes, the pressure drop of weak or hardly clogged reaction tubes is significantly larger. The differences in the extent of deposits in the individual reaction tubes require inconsistent strong burning of the deposits. Highly clogged reaction tubes are hardly traversed by the oxygen-containing gas and thus hardly freed from the carbonaceous deposits. Furthermore, when burning off the carbonaceous deposits by bringing into contact with oxygen-containing gas at elevated pressure and elevated temperature to note that not too large amounts of oxygen are used especially at the beginning of the exothermic burning process, otherwise the risk of uncontrolled burnup and associated, no longer tolerable thermal load of the reactor. In order to largely avoid inconsistent and also uncontrolled burning, the following specific embodiments of the method according to the invention can be used:

• - It is used as the oxygen-containing gas, a mixture of nitrogen and oxygen, wherein the relative proportions of these two gases constant, but the amount of gas used is increased in the course of the process. Since in this way at the beginning of the decoking process initially little, but then increasingly more oxygen is used, uncontrolled burning can be prevented. In addition, the increasing total amount of gas, especially the increasing amount of oxygen, leads to an improved burning of deposits in pipelines, which are particularly affected by deposits.
• - It is used as an oxygen-containing gas, a mixture of nitrogen and oxygen, the total amount of gas is constant, but the oxygen content is increased continuously (and the nitrogen content is lowered accordingly). In this way, uncontrolled burnup at the beginning of the process can be prevented. The increasing proportion of oxygen in the gas mixture also makes it possible to burn off deposits in particularly clogged pipelines in the case of an advanced combustion process.
• - It is used as the oxygen-containing gas, a mixture of nitrogen and oxygen, wherein the total amount of gas is increased by increasing the oxygen content in the course of the decoking process. Also in this particular embodiment of the method according to the invention the risk of uncontrolled burning is prevented by the use of lower amounts of oxygen at the beginning of the process.

In those of the three aforementioned particular embodiments of the method according to the invention, in which the total amount of gas is increased in the course of the process, it is very particularly preferred that the amount of the oxygen-containing Gas at least twice, preferably at least ten times and above addition, at least twenty times that at the beginning of Decoking method used gas volume, increased, the maximum possible amount of gas essentially by the capacity of the compressor, with the the oxygen-containing gas is blown through the reactor is limited. The increase The amount of oxygen-containing gas can be continuous or discontinuous respectively. Also, the timing of increasing the amount of oxygenated Gas is variable.

Of the preferably pulse-like addition of the water, preferably the water vapor, to the oxygen-containing gas can at any time during the Decoking process done. In a preferred embodiment the method according to the invention the decoking takes place first, preferably for a period of at least 1 hour, more preferably at least 10 Hours, about it more preferably at least 20 hours, and more preferably at least 40 hours, the period preferably being in a range of 1 hour to 100 hours, more preferably 10 hours to 50 Hours, in the absence of water or water vapor. During the above period can be a patchy and also uncontrolled burning by the measures mentioned above be avoided. Only after expiry of the aforementioned period is, preferably in the pulse-like manner described above, For the first time, water or steam was added to the oxygen-containing gas.

The course and the end of the removal of the carbonaceous residues can be determined according to the invention by determining the concentration of carbon dioxide or carbon monoxide in the exhaust gas. The process according to the invention is preferably ended when the carbon dioxide concentration in the exhaust gas differs from the ambient air carbon dioxide concentration by not more than 20%, more preferably not more than 10% and more preferably not more than 5%, the difference in (Δ _CO2 )% is determined according to the following equation: Δ CO2 [%] = {100 × (C CO2, exhaust / C CO2, air )} - 100%

Since, for example, as a result of a pulse-like addition of water or an increase in the amount of oxygen or the total amount of gas, the concentration of carbon dioxide in the exhaust gas can still increase, at least in the short term, even after reaching an apparent limit, the skilled person will determine the end of the Abrennvorgangs example, that he after an influence on the system, for example, by increasing the amount of gas, by increasing the temperature or by supplying water vapor observed the increase in carbon dioxide in the exhaust gas. If no significant increase in the CO ₂ concentration occurs after such an action, which makes economic continuation of the burning-off process sensible, the decoking process can be terminated. A complete removal of all carbonaceous deposits in the reactor is not imperative from an economic point of view and often does not make sense.

The method of removing the carbonaceous residues according to the invention is preferably terminated by stopping the flow of the oxygen-containing gas into the reactor, reducing the temperature of the reactor to a temperature below 300 ° C., preferably below 250 ° C., or both Measures (Preventing the flow of oxygen-containing gas and lowering the reactor temp temperature).

The inventive method for removing carbonaceous residues in a solid catalyst containing reactor for the catalytic gas phase oxidation of unsaturated hydrocarbons is preferably used to carbonaceous residues of the Reactor of the first stage in the oxidation of propene too acrylic acid to remove. In this first stage of the process mainly acrolein is produced, which is oxidized to acrylic acid in the second stage of the process.

at the reactor containing a solid catalyst is in this case preferably a tube bundle heat exchanger (tubular reactor), as described for example in DE-A-3042 468, on whose The disclosure is hereby incorporated by reference and incorporated by reference the revelation applies. A shell and tube heat exchanger comprises one or more reaction tubes, preferably of carbon steel or corrosion resistant Steel, which is a coolant such as a molten salt, to be flowed around, to regulate the temperatures inside the reaction tubes. The coolant is usually by an external heat exchanger in the Circulated.

Of the or the reaction tubes in turn comprise a reaction region with a multioxide catalyst fixed bed and a cooling area, preferably a cooling area with an inert fixed bed of α-alumina, Alundum, mullite, carborundum, stainless steel and ceramics, where is the cooling area in gas flow direction connects to the reaction area. The cooling area can also be in one spatially encompass the reaction area and the cooling area Be located reactor element. It is also conceivable that the cooling area and the reaction area in separate but gas-conducting with each other associated reactor elements are located. The reactions of the Reaction area and the cooling area can in the oxidation of propene to acrolein each independently regulated become. Furthermore, the shell-and-tube heat exchanger comprises at least one inlet, over a gas stream are fed to the one or more reaction tubes can, as well as an outlet, over the gases after flowing through the reaction tubes the jacket-tube heat exchanger being able to leave. If the reactor in the normal acrylic acid synthesis operation, so is a Inlet a gas containing oxygen, water, nitrogen and propylene introduced into the reaction tubes and an acrolein via an outlet containing gases from the shell-tube heat exchanger removed the first reaction stage and in the reactor of the second Guided reaction stage. If, on the other hand, the shell-and-tube heat exchanger is in the burn-off mode according to the invention, so will over an inlet, the oxygen-containing gas introduced into the reaction tubes and over an outlet containing the carbon dioxide and carbon monoxide exhaust gas from the shell-and-tube heat exchanger removed the first reaction stage, the exhaust gases via a Derived from the reactor become.

In the case of the oxidation of propene to acrolein, any catalyst which converts propene to acrolein in a high yield in a vapor-phase oxidation can be used as the catalyst. Particularly preferred is a multioxide catalyst based on molybdenum and bismuth, more preferably on molybdenum, bismuth and cobalt or on their oxides. Examples of such catalysts are described in DE-A-30 42 468 and DE 699 03 698 T2 the disclosure of which is part of the disclosure of the present invention.

• (β1) einen Reaktor umfassend einen Feststoffkatalysator beinhaltende Reaktionszone, gegebenenfalls eine Kühlzone sowie ein Temperaturregulationselement,
• (β2) mindestens einen Einlass für ein sauerstoffhaltiges Gas, der gasleitend mit dem Inneren der Reaktionszone verbunden ist,
• (β3) mindestens einen Auslass für ein Abgas beinhaltend Kohlendioxid oder Kohlenmonoxid, welcher gasleitend mit der Reaktionszone und/oder der Kühlzone verbunden ist, sowie
• (β4) eine Zuleitung für die Zugabe von Wasser, die fluidleitend oder gasleitend mit dem Einlass, mit der Reaktionszone oder mit der Kühlzone verbunden ist.

The invention further relates to a device for the catalytic gas phase oxidation of unsaturated hydrocarbons comprising as device units

• (β1) a reactor comprising a reaction zone containing a solid catalyst, optionally a cooling zone and a temperature regulation element,
• (β2) at least one inlet for an oxygen-containing gas which is gas-conductively connected to the interior of the reaction zone,
• (β3) at least one outlet for an exhaust gas comprising carbon dioxide or carbon monoxide which is gas-conductively connected to the reaction zone and / or the cooling zone, as well as
• (β4) a feed line for the addition of water which is fluid-conducting or gas-conducting to the inlet, to the reaction zone or to the cooling zone.

In a particular embodiment of the device according to the invention is the supply line for the encore of water (β4) with a control element (β5) provided the impulsive addition of water over this Supply line allows.

The The invention also relates to a process for removing carbonaceous material Residues in one Solid catalyst containing reactor for catalytic gas phase oxidation unsaturated hydrocarbons, in which the device described above is used.

Furthermore, the present invention relates to the use of water, in particular the use of water vapor, very particularly preferably the use of water vapor in the form of pulses, for the removal of carbonaceous residues in a reactor, in particular in an egg nen solid catalyst-containing reactor for the catalytic gas phase oxidation of unsaturated hydrocarbons.

The Invention will now be described with reference to a drawing and a nonlimiting Example closer explained.

It shows the 1 a device according to the invention for carrying out the method according to the invention.

A preferred apparatus for the oxidation of unsaturated hydrocarbons ( 1 ) comprises a reactor ( 2 ) as well as a temperature regulation element ( 7 ). Via an inlet ( 11 ), over which during normal reactor operation a gas mixture comprising oxygen, nitrogen, water vapor and the unsaturated hydrocarbon is blown into the reactor, the oxygen-containing gas can be injected in the inventive method for removing carbonaceous deposits. The reactor comprises a reaction zone ( 3 ) containing a solid catalyst ( 4 ) having. In the gas flow direction to the reaction zone ( 3 ) followed by a cooling zone ( 5 ), which is an inert fixed bed ( 6 ) having. The temperature regulation element ( 7 ) comprises a temperature regulation fluid ( 8th ), such as a molten salt, which is supplied via the supply line ( 9 ) and the derivative ( 10 ) continuously through the temperature regulation element ( 7 ) to be led. Via an outlet ( 12 ), over which the oxidized hydrocarbon-containing gas mixture is led out in normal reactor operation, in the inventive method for removing the carbonaceous residues, the carbon dioxide or carbon monoxide-containing exhaust gas from the reactor ( 1 ) away. In at least part of this exhaust gas can be used for the continuous determination of the concentration of carbon dioxide or carbon monoxide in the exhaust gas of a measuring device ( 13 ). Via the supply line ( 14 ) with a control element ( 15 ) is pulsed water vapor into the inlet ( 11 ) brought in. It is also possible according to the invention to introduce the water directly into the reaction zone ( 3 ) to blow in a pulsating manner.

EXAMPLE:

REMOVAL OF CARBON CONTAINING RESIDUES (= DECO KING).

preparation of decoing

In a tube bundle heat exchanger according to 1 containing a fresh, based on molybdenum and bismuth metal oxide catalyst, a gas mixture containing propylene, water vapor and air at a salt bath temperature of about 300 ° C and a reactor pressure of 1 kg / cm ² G is blown. Under the above conditions, the reactor was operated for a period of several days with the reactor temperature always ranging between 305 and 320 ° C. After a pressure loss of about 209 mbar had been recorded within the reactor and the yield had dropped to 86%, the decoking process according to the invention was carried out.

To the Propengasstrom has been turned off, was an exhaust gas discharge over the the exhaust gas containing carbon dioxide and carbon monoxide from the reactor can be led out, mounted.

Then, via the inlet ( 11 ) Air at a pressure of 1 bar is injected in an amount of about 0.5 kg / (h · 1 _{catalyst bed volume).} About the exhaust gas discharge, the air (together with the formed during decoking carbon dioxide and carbon monoxide) from the reactor.

The reactor temperature is now raised by raising the salt bath temperature in steps of about 5 ° C per hour to a temperature in a range of 350 to 360 ° C. About two hours after the temperature reached a value of about 350 to 360 ° C, water vapor was added via a separate steam supply for a period of two hours in such an amount that during this two-hour period, the water vapor concentration in the air about 17 vol. % amounted to. Subsequently, the steam supply was turned off and still air (without added steam) at a pressure of 1 bar and in an amount of about 0.5 kg / (h x 1 _{catalyst bed} volume) at a temperature in a range of 350 to 360 ° C. passed through the reactor until the determined by gas chromatography carbon dioxide concentration in the exhaust gas for a period of at least one hour equal to the value of the carbon dioxide concentration in the ambient air.

To Termination of the decoking process was the relative pressure loss only 197 mbar while the yield had risen to 87.86 percent.

Claims (10)

A process for removing carbonaceous residues in a solid catalyst-containing reactor for catalytic gas phase oxidation of unsaturated hydrocarbons wherein the deposited carbonaceous residues are continuously contacted with an oxygen-containing gas and with water, preferably with water vapor - At a temperature T _reactor in a range of 260 ° C to 500 ° C and - be brought in a pressure P _reactor in a range of 0.8 to 20 bar to form a carbon dioxide or carbon monoxide-containing exhaust gas, and the carbon dioxide or carbon monoxide contained exhaust gas is continuously removed from the reactor. Method according to claim 1, wherein the deposited, carbonaceous residues pulsed be brought into contact with the water vapor. A process according to any one of the preceding claims, wherein the oxygen is used in an amount ranging from 0.01 to 1 kg O ₂ / (h x 1 _{catalyst bed} volume). The method of claim 3, wherein the time interval between two pulses in a range of 5 minutes to 200 hours lies. A method according to claim 3 or 4, wherein each one Pulse a length in a range of 1 second to 24 hours. Method according to one of the preceding claims, wherein in a part of the process, the amount of carbon dioxide in the exhaust gas Variation of the amount of steam is regulated. Method according to one of the preceding claims, wherein the amount of oxygen-containing gas by at least 20%, based on the amount of oxygen-containing gas at first contact the carbonaceous residues among the in claim 1 said reaction conditions with the carbonaceous Residues in Contact has been brought, increased becomes. Device for the catalytic gas phase oxidation of unsaturated hydrocarbons comprising as device units (β1) a reactor ( 1 ) comprising a solid catalyst ( 4 ) containing reaction zone ( 3 ), optionally a cooling zone ( 5 ) as well as a temperature regulation element ( 7 ), (β2) at least one inlet ( 11 ) for an oxygen-containing gas which is gas-conducting with the interior of the reaction zone ( 3 ), (β3) at least one outlet ( 12 for an exhaust gas comprising carbon dioxide or carbon monoxide which is gas-conducting with the reaction zone ( 3 ) and / or the cooling zone ( 5 ) and (β4) a feed line for the addition of water ( 14 ), the fluid-conducting or gas-conducting with the inlet ( 11 ), with the reaction zone ( 3 ) or with the cooling zone ( 5 ) connected is. Apparatus according to claim 8, wherein the supply line ( 14 ) for the addition of water (β4) with a control element ( 15 ), which allows the impulsive addition of water through this supply line. Method according to one of claims 1 to 7, wherein a device is used according to claim 8 or 9.