CA1062641A

CA1062641A - Process for taking a hydrogenation reactor out of operation

Info

Publication number: CA1062641A
Application number: CA221,839A
Authority: CA
Inventors: Abraham A. Pegels
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1974-04-25
Filing date: 1975-03-11
Publication date: 1979-09-18
Also published as: NO146893C; DK172475A; FR2268859A1; SE7504666L; IT1037563B; GB1508021A; NO751432L; ES436838A1; JPS50154177A; NO146893B; FR2268859B1; DE2517869A1; SE416817B; DE2517869C2; JPS5854854B2; AU8034175A

Abstract

A B S T R A C T
Process for taking out of operation a reactor filled with a catalyst for catalytic hydrogenation by a) reducing (and keeping) the temperature to below 300°C
b) discontinuing the feed supply and replacing the hydrogen by an inert gas c) purging the reactor with the inert gas optionally together with a hydrocarbon oil d) introducing oxygen in the purge gas and increasing the amount thereof to a partial pressure of at least 0.2 kg/cm2 and e) opening the reactor.

Description

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The invention relates to a process for taking out of operation a catalyst-filled reactor for the catalytic hydrogenation of a liquid or gaseous feed, in which -. hydrogenation the feed i5 passed over a catalyst in the presence of added hydrogen. In general, hydrogenations of this type ~lill be carried out at a temperature above ; 300C. In many cases the feed will contain sulphur com-pounds, from which H2S is formed during hydrogenation.
The above-mentioned catalytic hydrogenations often occur in the refining of mineral oil, but are also applied ~ outside that field.
.` An example of the use of liquid feed is the catalytic desulphurization of certain petroleum fractions, such as a distillate fraction or a residual fraction. In this process the feed together with hydrogen is passed through a reactor filled with desulphurization catalyst at a temper- ~
ature at which the reed is not yeb or only slightly con- . -verted by cracking or isomerization. Sulphur compounds ~,; pre~ent in the liquid feed are hydrogenated With the form-: 20 ation of hydrogen sulphide. A desulphurized feed on the one hand and a hydrogen sulphide and unused hydrogen-1~ containing gas on the other are discharged from the re-:~3 actor. The latter gas~ for example~ can be passed to the :3 , Clau~ plant mentioned below.
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', ~06Z641 An example Or the above-mentioned catalytic hydrogen-ation involving a gaseous feed is the catalytic reduction of a Claus of~-gas originat,ing from a Claus plant ~or the preparation of elemental sulphur by reaction o~
sulphur dioxide and hydrogen sulphide. Claus off-gas still contains a percentage of unreacted sulphur compounds which must usually be removed, which may be effected by total reduction of the sulphur compounds with hydrogen to hydrogen sulphide, after ~hich the hydrogen sulphide Drmed is removed from the Claus off-gaR (for example by ; absorption) and i8 recycled to the Claus plant~ Claus plants are not only found on refinerie8 but also in natural gas fields, for processing the hydrogen sulphide removed from the natural gas.
A phenomenon which almost invariably occurs during the catalytic hydrogenation of sulphur compounds is the deposition of carbon on the catalyst. This carbon often originates either from hydrocarbons of the feed (for i~ , . .;
~ example in the desulphurization of petroleum fractions) : ~. . ~ , , or from combustion gases admixed for heating (for 3 example at the reduction of Claus off-gas). In the de- ;~
1 sulphurization of liquid products, for example, tarry products are also deposited on the catalyst.
~i Solid particles, such as scale, silica, me~al salts and iron particles, are usually deposited at the beginning , .~........... ' .

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of the cataly~t bed, the sulphides and carbon being present over the entire length in the catalyst bed.
In the regeneration of this catalyst the carbon and the tarry products are burnt off, while sufficient oxygen mixed with a large quantity of steam or nitrogen is invariably supplied to maintain the temperature in the reactor at an acceptable level. Temperatures applied in practi~e often lie between 300C and 500C, since the carbon is not burnt off below this temperature.
` 10 In this regeneration the sulphides are oxidized simultaneously with the carbon and the tar and with a view to the desirability of limited heat generation this oxidation may only proceed very gradually. The regener-ation, therefore, usually takes a very long time, with large reactors up to some days.
In some cases, for example in the desulphurization ~l of residual petroleum fractions, the total quantity of i~ catalyst in the reactor is very large, for example 500 tons. In these cases the quantity of catalyst on which ' 20 no solid particles have been deposited becomes, in an ;l absolute sense, very large compared with the quantity of catalyst on which such deposition has occurred. A draw-back is then that of the total quantity of catalyst the metal sulphides present are oxidized in order to cause the carbon and the tarry products to be burnt off.
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, , ~062~4 When the reactor must be opened for some reac;on or other, it will not be sufricient for the reactor to be cooled and pur~ed with an inert gas~ as would be expected.

It has, in fact, ~een found that when the reactor is 5 purged with low~temperature inert gas ~or a long period o~ tlme and subsequently opened, the catalyst begins to glow in the open air and releases sulphur dioxide in case sulphur compounds have been present in the feed. Under these conditions the catalyst content consequently ha~ a pyrophoric character, and the per~ormance o~ work on or in the reactor is impossible or dangerous.
.i Up to now this problem has been solved by fully regenerating the catalyst Content before opening the re-actor. ThiS solution, howeverJ is expensive and time-consuming and the invention aims at providing other routes.
I For example, it has been found to occur in practice :~:J that the reactor must be opened, while the activity of ` the catalyst has not yet decreased to such an extent ` that the catalyst requires regenerating. Another object of the invention is to provide a process in which this ; regen~ation is not necessary in such cases and the re-actor can nevertheless be opened.
- It has now been found that the pyrophoric character of the catalyst is entirely removed by performing a fully 25 controlled oxidation, in which mea~ures are taken to maintain the temperature continuously below 300C.

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Surprisingly, this "passivation" of the catalyst takes place without the active sulphides, such as cobalt, nickel, molybdenum and/or tungsten sulphide, being oxidized.
The passivation, therefore, takes considerably less time 5 than the regeneration customary hitherto, in which latter treatment these sulphides are in fact oxidized.
It has further been found that also the carbon and the tarry products are hardly if at all oxidized in the passivation. There are distinct indications that the catalyst derives its pyrophoric character from the presence of finely divided iron and/or iron sulphide, which seem to be oxidized at low temperature.
The invention, therefore, relates to a process as stated above, in which:
a) the temperature in the reactor is reduced to below 300C in caqe it was above 300C and kept at a temperature below 300C until the reactor has been , opened;
;~ b) the supply of feed is discontinued and the added j 20 hydrogen is replaced by an inert gas before, after ~ -or during the said reduction in temperature;
c) the reactor is purged with a purge gas consisting of 1 the said inert gas for some time, .~, d) subsequently an oxygen-comprising gas is introduced~

25 ~ into the purge gas in such a quantity that the ~ . .
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` ~062641 initial oxygen content is at most 1% by volume;
e) the oxygen content of the purge gas is increased and the supply of purge gas is continued until no further appreciable heat generation in the re-actor is found to occur;
f) the oxygen partial pressure of the purge gas is brought to at least 0.2 kg~cm2, and g) the reactor is opened.
Because in general the temperature in the reactor during the catalytic ~drogenation i5 above 300C, the temperature in the reactor has to be reduced in most cases to below 300C by cooling.
If the supply of feed is discontinued before the re-duction of the temperature in the reactor, it is possible to,effect the reduction of that temperature by means of the hydrogen supplied or with the purge gas. Especially in those cases where a heavy feed, such as a residual petroleum fraction is used, it is advisable already to discontinue the supply of feed at high temperature, to prevent hardening of the feed in the reactor. -~
In the event of the feed being liquid, it is possible and preferred to change over to another, lighter feed, such as naphtha or gas oil, immediately before putting the reactor out of operation and to reduce the temper-ature in the reactor with this lighter feed. In this ~1 ~
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-8- ~ ~62641 manner any rests oP residual products are removed which may have deposited on the catalyst particles.
The catalyst is cooled more rapidly with a 1iqllid than with a gas.
It is also possible to reduce the temperature in the reactor during or partly during the interruption of the supply of feed, this interruption beihg effected gradually and therefore lasting a longer period of time.
This simultaneous cooling and interruption of the feed occurs, for example, when hydrogen is supplied to the reactor and subsequently the supply of feed is gradually discontinued or when a colder feed i8 supplied than before .
~The supply of feed may also be interrupted after the cooling and the cooling may be at least partly effected with the feed. In this case, o~ course, only a small part of the feed is hydrogenated, 80 that under certain conditions it may be advisable during cooling to use a feed which need not be hydrogenated.
It is preferred to reduce the temperature in the re-', actor with the aid of a hydrocarbon oil in particular with naphtha or gas oil.
The final object is to have a reactor in which the : j , temperature i8 below 300C and which contains neither feed nor hydrogen. The latter is obtained by purging the ~;.

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1062~;41 reactor wi~h an inert gas before, during or after cooling.
The said inert gas may, for example, consist of carbon ; dioxide, and is preferably nitrogen.
After substantially all the hydrocarbon and hydrogen residues have been removed from the reactor, for example less than 1% by volume is present by sufficient purging with inert gas, a small quantity of air or oxygen is ad-mitted into the purge gas. This initial quantity must in any case be so low that less than 1% by volume o~
oxygen is present in the gas and must ~so be sufficiently low to ensure that the temperature in the reactor does not exceed 300C.
The passage through the reactor of the purge gas with the low percentage of oxygen is now continued. A
quantity of oxygen is consumed which is attended by a rise in temperature uhich, as already stated, should always remain limited to a maximum increase to 300C.
The oxygen content of the purge gas is preferably so controlled that the temperature of the purge gas discharged from the reactor remains below 150C. This temperature of the purge gas used is a reliable in-dication of the temperature in the reactor and is easy -~ to determine.
J According to an embodiment of the invention the oxygen-containing purge gas is recycled after it has been . , .

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passed through the reactor, the purge ~as being cooled and the oxygen content being supplemented. It will be clear that this provides a saving compared with the situation in which fresh purge gas is invariably supplied.
When the rise in temperature in the reactor begins to decrease at the oxygen percentage in the purge gas below 1% by volume, the oxygen content of the purge gas is gradually raised in the range above thi~ limit o~ lS
by volume. It is then continuously ensured that the temper-ature in the reactor does not rise above 300C.
Also, during this period in which the oxygen content in the purge gas is higher than 1% by volume, the purge gaæ is preferably recycled and oxygen or air is made up.
The rises in temperature will generally be lower in this period, since the controlled oxidation is in an advanced stage. The consumption of oxygen will also be lower.
In an embodiment o~ the invention the oxygen content of the purge gas is increased at a predetermined rate, a ~!
~ further rise being invariably postponed, however, as long 20~ as the temperature in the reactor exceeds a predetermined value. In this manner the pas~ivation can be performed in a relatively simple manner from the control point of view.
~he oxygen content o~ the recycling purge gas is pre~erably made up to the desired value by the addition .. . .
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of less air ~ccording as the rise in temperature in the reactor is higher. The oxidation is thus fully controlled and the rise in temperature is limited to a relatively constant value, since in the case of an ex-; 5 cessive temperature rise the cause thereof - namely too ~ high an oxygen content - is removed and in the case of ; too low a temperature rise the insufficient oxygen content is raised, An excessive rise in temperature involves the disadvantage of components being oxidi~ed in the reactor which in fact need not be oxidized and too low a rise in temperature means that the controlled oxidation proceeds more slowly than is strictly necessary.
~ According to the invention the oxygen partial pres-`,~ sure is by preference ultimately maintained at at least ! 15 0.2 kg/cm2, in particular at least 0.8 kg/cm2, for some 3 time before the reactor is opened. The reactor i8, prefer-ably, further purged for some time, while no further `
, appreciable heat generation is found to occur. Depending on the circumstances, this may take place at an oxygen ~ ;
~ 20 partial pressure of at least 0.2 kg/cm2 or below. The ;1 latter two measures guarantee optimum safety.
It has been experienced that under certain conditions . . . -:
there is a risk for local burning off of coal, which may lead to an uncontrolled temperature increase in the zone ~ 25 wherein the coal is burned off, and which undesired :~3 ~ ' ,.j -12- ~0 ~ ~ 1 temperature increa~e may spread to other areas of the catalyst. Conditions in which such a phenomenon may occur are, e.g., the presence of large amounts of pyrophoric compounds in the reactor, or cases in which during the catalytic hydrogenatiOn and/or the coding of the reactor not all sites of the catalyst have been wetted by the cooling medium (e.g., naphtha or gas oil) and local dry zones exist. The latter phenomenon may happen in particular in cases in which the catalyst is polluted to an appreciable extent, which results in a poor distribution of the cooling agent over the catalyst.
In order to avoid any danger of uncontrolled temper-ature increase in the reactor, it is preferred that the reactor is purged with a hydrocarbon oil together with the purge gas. The hydrocarbon oil is very suitably ` petroleum-based, and may, e.g., consist of naphtha, or ~ preferably of gas oil. The rate of hydrocarbon oil supply j to the reactor may vary between wide limits. Preferably, the said rate amounts to at least 5% of the designed rate of the supply to the reactor of the feed to be catalytically hydrb~genated~ In particu]ar, the said percentage amounts to at least 10. The rate of circulating gas oil is, prefer-ably, increased to about the design rate during the purge gas circulation.

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In order to obtain a complete wetting of the catalyst, it is of advantage to fill the catalyst-containing re-actor completely or substantially completely with a hydrocarbon oil (in particular a gas oil) before oxygen-~ 5 containing purge gas is supplied to the reactor. Very -j suitably, the reactor is filled up with the hydrocarbon ~i oil from below, after the hydrogen has been substantially removed from the reactor. After the hydrocarbon oil has . subsequently been removed from the reactor, circulation o~ purge gas is started. To this purge gas a circulating hydrocarbon oil can be added immediately or after some time. -j It is desirable that the temperature in the reactor should be relatively low before it is opened. This temper-ature is preferably at most 60C. This low temperature may , already have been reached during purging. It is also pos-~1 sible to cool the reactor after purging. It is then ;~ ensured that maximum conversion of iron sulphide, etc., l can take place for as long as possible at a relatively 1 20 high temperature. In the latter case forced cooling is , :J' ' pre~ferred, for example with air, since the reactor - if ~ ;
l left to itself - will cool of r only very slowly.
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`~ The invention can, for example, be applied to a reactor for the cataYytic desulphurization of a liquid ~ ;
hydrocarbon feed. Examples of such desulphurization . . ~ : .
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processes are the desulphurization of light distillate fractions of petroleum and the desulphurization of residual petroleum fractions.
The invention may, however, also be applied to other proces es, for example ~e catalytic reduction to hydrogen sulphide of sulphur compounds in a gaseous feed.
In the latter case the feed may, for example consist of the off-gas of a Claus plant Por the~reparation of elemental sulphur from sulphur compounds-containing gases.
In the above-mentioned types of desulphurization processes the catalyst very suitably consists of cobalt ;;~ sulphide and/or nickel sulphide combined with molybdenum sulphide and/or tungsten sulphide, on a carrier at least the greater part of which consists of silica and/or alumina.
Such catalysts have been found to exhibit pyrophoric properties. It will be understood, however, that any other type of catalyst which exhibits pyrophoric properties can be treated according to the present invention.
The invention provides an improvement of the process ,¦ 20 for the continuous catalytic hydrogenation of one or more I sulphur compounds in a liquid or gaseous feed with the formation of hydrogen sulphide, in which hydrogenation the feed is passed through a catalyst-filled reactor in f the presence o~ added hydrogen at a temperature above , 25 200C. The improvement consists in that by the time a :
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predetermired increase in pressure drop across the re-act~r has occurred as a r~Ult Or contamination of the catalyst layer on the feed end of the reactor, the re-! actor is taken out of operation by the process of one ~ ~
or more of the above embodiments of the invention, the -contaminated catalyst layer is ~ubsequently replenished and the reactor again put into operation. An advantage o~ this method is that the total quantity of catalyst need not - as hitherto - be replenished or regenerated.
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lC Especially in the case of a reactor for the catalytic desulphurization of a residual petroleum fraction the above-mentioned process of the invention has great advantages, since in such a case very large quantities ~ , of catalyst are use~d. In practice a total quantity of catalyst of about 750 m3 per reactor is currently used, in which the steam-air regeneration often involves difficulties owing to the fact that about 0.5-1.0 ton of steam per ton of catalyst per hour is required for regeneration, which often constitutes a very high peak load for the refinery. In this connection an advantage of the process of the invention is that the purge gas ~ `
3 can-be recycled. -Especially in the case of liquid feed the pressure ; drop across a reactor for catalytic hydrogenation o~ten rises owing to the deposition of scale on the first .. :.' .
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catalyst layer. This deposit often contains a high percentage of metals, such as metallic iron or metal salts originating from the apparatus or feed. The de-position of scale, however, does not imply that the catalyst is deactivated. In the desulphurization of liquid feeds the catalyst in a reactor for the desulphur-ization of residual petroleum fractions is, for example, so blocked after about half a year that the upper layer must be replenished, whereas this period is generally much longer for the catalyst for desulphurization of distil-late petroleum fractions~ for example about 3 months to about 2 years. Further, too high a pressure drop re-peatedly occurs before the catalyst has been deactivated.
An advantage ~ the passivation according to the present invention compared with the regeneration of the catalyst as previously effected, is that the catalyst need not be resulphided. In the case of the catalyst con-taining molybdenum a further drawback of the regener-ation is that it occurs at a much higher temperature under oxidative conditions, so that there is a risk of sublimation of molybdenum trioxide. In this connection it should be noted that during the regeneration the burning-off generally takes place at a temperature between 370C and 470C. Further, the above-mentioned ~ 25 embodlment of the invention is also based on the fact :,.. ..

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that the catalyst activity has been found not to be in-creased appreciably by the burning-off of the carbon, ~-~
provided it is present in the usuai percentages, the latter again being present again rather rapidly after the reactor has again been put into operation, without affecting the activity in a high degree. For this reason the burning-off of carbon is there~ore not strictly neces-sary for regeneration. 1 ` The above-mentioned improvement of the process ~or `
; 10 continuous catalytic hydrogenation is preferably carried out in such a way that while the reactor is taken out of ., ,~ , :
operation the C02 content in the purge gas leaving the reactor is controlled during the period when oxygen is .
present in the purge gas supplied to the reactor and this ;
quantity of oxygen is reduced, or brought to zero, as long as the quantity of C02 exceeds a predetermined ~i value. As soon as the C02 ccntent becomes too high, this ~ fact in itself is already an indication of too much carbon ! being burnt off. It is preferably ensured that the C02 i 20 content remains below 0.04% by volume.
The invention will now be illustrated with reference ;~
to the following Examples.
, EXAMPLE I
` The appertaining figure is a diagrammatic represent-ation of the course of the oxygen content of the purge gas used in the passivation in this example.

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'". ~ ~ ~ ' '' . ,, ~ ~ 6~1 In a semi-commercial plant for the catalytic de-sulphurization of residual petroleum fractions, l470 tons of residual petroleum fracti~S were desulphurized. The plant consisted o~ a catalyst-filled desulphuriæation reactor. The catalyst comprised 3.2% by weight of Co ald 9.2% by weight of Mo on a carrier mainly consisting of alumina, which had previously been sulphided. The reactor contained the catalyst as a fixed bed, the residual fraction to be treated was supplied at the top of the reactor and discharged at the bottom, in parallel flow with hydrogen.
Immediately before the passivation according to the invention, 3.2% by weight of Co and 9.2% by weight of Mo were present on the catalyst. At the top ~ the reactor the catalyst contained lO.2~ by weight of V; 4.4% by weight of Ni; 0.7% by weight of Na and 0.40% by weight of Fe. At the bottom Or the reactor the catalyst con-tained 0.8% by weight of V; 0.3% by weight of Ni; 0.2%
by weight of Na and 0.04% by weight of Fe.
The reactor was now passivated, in which the reed of the residual ~raction was first changed into gas oil with the continuous supply of a hydrogen-rich gas mixture.
~ ~he reactor was cooled over a period of io hours. During .!, this cooling period the ~all in temperature was con-tinuously less than 40C/hour. The temperature of the gas , !

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The gas oil feed was now discontinued and the re-actor was purged with a hydrogen-rich gas over a period of about 6 hours. The hydrogen was subsequently replaced by nitrogen and the reactor was purged with nitrogen . "
until the hydrogen concentration was below 1% by volume.
The nitrogen pressure was raised to 6 kg/cm2 and the ;
nitrogen was recycled by meanS Of a Compressor.
Subsequently air was injected into the recycling nitrogen. The oxygen content of the purge gas supplied -~ to the reactor was continuously recorded and is shown in the Figure. In this Figure the time "t" has been ¦ 15 plotted in hours on the horizontal axiS and the oxygen percentage in % by volume on the vertical axis. As is shown, the injection of oxygen was performed dis-~ continuously. The duration of the injections, how~ver, ?
increased continuously.
The Table shows, for the same period of time as in the Figure, the process pressure (superatmospheric pressure), the duration of the air injections and the ~l C2 percentage in the purge gas leaving the reactor.
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Time in ¦ Superatmospheric Duration of C02 percent-minutes pressure in kg/cm2 air injection age in vol.%
in minutes _ 0 3.4 1 _ 3.4 3 ~
3.8 2 0.018 4.9 5 _ 120 5.4 5 o.ols 150 6.o 5 0.020 180 5~9 lo 0.025 225 5.8 12 . 0,020 285 5.5 15 0.020 330 4.7 40 0.020 450 o. 8 full air 0.030 circulation 510 _ end of pas- 0.040 sivation . . :~
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2.5 and 4 hours after the beginning of the purging. It is noted that the C02 content increases by the injection . . . .
of air into the purge gas owing to the C02 present in ;~
this air.
The temperature of the purge gas wa~ continuously - 15C at the moment it left the reactor. The passivation process ac~ording to the present Example has, therefore, been carried out very cautiously.
After purging for 7.5 hours by means of oxygen-con-taining nitrogen with increasing oxygen content, the ; passivation process was completed with forced-air circulation ~rough the reactor for 30 minutes, after which the reaotor was opened. The catalyst then had no more pyrophoric properties.
Analysis of the catalyst subsequently revealed that, dependent on the place of origin in the reactor, about 7-15% by weight of carbon and about 7-8% by weight of j sulphur w~epresent.
EXAMPLE II
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l 20 In the semi-commercial plant described in Example I
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-' 106,000 tons of residual petroleum fractions were de-sulphurized. The catalyst was polluted to an appreciable-~ extent, and contained much pyrophoric material.
i The reactor was cooled to 40C, the hydrogen was ....
replaced by nitrogen and the pressure of nitrogen increased . .

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to 6 kg/cm2, oxygen was supplied to the purge gas and the oxygen content of the purge gas was gradually in-creased as described in Example I.
The temperature wa~ measured at 3everal sites in the reactor and the C02 content of the off-gas was measured periodically. A~ter about 20 hours (at an oxygen con-centration in the purge ga~ of about 18% by volume) the amount of C02 in the off-gas increased drastically (from 0.0~ to 0.3% by volume) and in the end part of the re-actor a rapid temperature increase was ~asured (~rom the original 40-50C to 100C). Subsequently, the re-actor was opened and the catalyst was discharged. The , catalyst originating from the end part of the catalyst ,, was hot and gas oil vapour and S02 were emerged therefrom.
;l 15 Although the catalyst was not pyrophoric, it will be clear that the risk exists that at further temperature ~ increase uncontrolled burning-off of coal may occur.
; This risk i~ avoided when taking the reactor out of ~, operation according to Example III.
,,!, 20 EXAMPLE III
A catalyst which had been used for the catalytic de- ~
sulphurization of about the same amount of residual ;~ -, petroleum fract~ns as described in Example II, was cooled ', and the amount of hydrogen in the reactor was reduced to lg by volume with the aid of nitrogen as a pur~e gas ,! :

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as described in Example II, The reactor was evacuated, and gas oil was pumped into the reactor from below until the total catalyst content of the reactor was completely submerged. Subsequently, the gas oil wa~
removed ~rom the reactor, and nitrogen was supplied to a presQure of 6 kg/ cm2 . The nitrogen was circulated ~- ~nd simultaneously an amount of gas oil (10% of the . amount for which the installation was designed) was - circulated. Then 1% by ~olume of oxygen was added to the purge ~as. After one hour the circulation of nitrogen + oxygen was stopped and circulation of air at 6 kg/cm2 .,.~
was commenced. The gas oil circulation was gradualIy increased to about the design rate. After three hours of air and gas oil circulation, during which time no trace of temperature increase or undesired oxidation of coal had been experienced, the reactor was opened.
The catalyst proved to be not pyrophoric.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for taking out of operation a catalyst-filled reactor for the catalytic hydrogenation of a liquid or gaseous feed, in which hydrogenation the feed is passed over the catalyst in the presence of added hydrogen, characterized in that:
(a) the temperature in the reactor is reduced to below 300°C
in case it was above 300°C and kept at a temperature below 300& until the reactor has been opened;
(b) the supply of feed is discontinued and the added hydrogen is replaced by an inert gas before, after or during the said reduction in temperature;
(c) the reactor is purged with a purge gas consisting of the said inert gas for some time;
(d) subsequently an oxygen-comprising gas is introduced into the purge gas in such a quantity that the initial oxygen content is at most 1% by volume;
(e) the oxygen content of the purge gas is increased and the supply of purge gas is continued until no further appreciable heat genera-tion in the reactor is found to occur, (f) the oxygen partial pressure of the purge gas is brought to at least 0.2 kg/cm2, and (g) the reactor is opened.

2. A process as claimed in claim 1 characterized in that the temperature in the reactor is reduced with the aid of a hydrocarbon oil.

3. A process as claimed in claim 2 characterized in that the hydrocarbon oil is naphtha or gas oil.

4. A process as claimed in claim 1 characterized in that the inert gas consists of nitrogen.

5. A process as claimed in claim 1 characterized in that the oxygen content of the purge gas is so controlled that the temperature of the purge gas discharged from the reactor remains below 150°C.

6. A process as claimed in claim 1 characterized in that the oxygen-containing purge gas is recycled after it has been passed through the reactor, the purge gas being cooled and the oxygen content being supplemented.

7. A process as claimed in claim 1 characterized in that the oxygen partial pressure of the purge gas is ultimately maintained at at least 0.8 kg/cm2 for some time before the reactor is opened.

8. A process according to claim 1 characterized in that the reactor is purged with a hydrocarbon oil together with the purge gas.

9. A process according to claim 8 characterized in that the hydrocarbon oil consists of a gas oil.

10. A process according to claim 8 characterized in that the rate of hydrocarbon oil supply to the reactor amounts to 5% to 25% w of the designed rate of the supply to the reactor of feed to be catalytic-ally hydrogenated.

11. A process according to claim 10 characterized in that the said percentage amounts to at least 10.

12. A process as claimed in claim 1 characterized in that the catalyst-containing reactor is filled completely or substantially completely with a hydrocarbon oil before an oxygen-containing purge gas is supplied to the reactor.

13. A process as claimed in claim 11 characterized in that the said hydrocarbon oil is a gas oil.

14. A process as claimed in claim 1 characterized in that the CO2 content of the purge gas leaving the reactor is controlled during the period when oxygen is present in the purge gas supplied to the reactor and this quantity of oxygen is reduced, or brought to zero, as long as the quantity of CO2 exceeds a predetermined value.

15. A process as claimed in claim 14 characterized in that it is ensured that the CO2 content remains below 0.04% by volume.

16. A process as claimed in claim 1 characterized in that the temperature in the reactor is at most 60°C before it is opened.

17. A process as claimed in claim 1 characterized in that a reactor for the catalytic desulphurization of a liquid hydrocarbon feed is used.

18. A process as claimed in claim 1 characterized in that a reactor for the catalytic reduction to hydrogen sulphide of sulphur compounds in a gaseous feed is used.

19. A process as claimed in claim 18 characterized in that the feed consists of the off-gas of a Claus plant for the preparation of elemental sulphur from sulphur compounds containing gases.

20. A process as claimed in claim 17, 18 or 19 characterized in that the catalyst consists of cobalt sulphide and/or nickel sulphide combined with molybdenum sulphide and/or tungsten sulphide on a carrier, at least the greater part of which consists of silica and/or alumina.