DE2057412C3 - Process for the regeneration of a hydrocarbon conversion catalyst - Google Patents

Description

The DT-AS 10 44 045 relates to a process for regenerating a hydrocarbon conversion catalyst comprising a platinum group metal on an alumina support by treatment with a mixture of hydrogen chloride and / or hydrogen fluoride and water vapor and oxygen at 250 to 55O ⁰ C, wherein the molar ratio of steam to hydrogen halide above 50 lies. The US-PS 32 30 179 also relates to a process for regenerating voi Platinkataiysatorea step process with oxygen in a three, first being obtained at about 200 bii 37o ^C C with a regeneration gas containing 0.02 to 2 mol percent free oxygen, then at about 4 ° C. to 510 ⁰ C contains a regeneration gas containing 0.05 to 2 mol · percent free oxygen and, finally, be at least 200 ⁰ C is treated with hydrogen. However, both types of catalyst contain as catalytic

ίο active metal just a platinum group stable.

However, the invention relates to a regeneration of hydrocarbon conversion catalysts from a porous support with a platinum component, a germanium component and a halogen component, and with this type of catalysts, the regeneration methods conventionally used to date have proven to be unsuccessful, since the regenerated catalyst always has a much lower activity and a lower halogen content than the fresh catalyst possessed. Try the

ao halogen content after regeneration to the original Adjusting the value also proved unsuccessful. The problems with regenerating this Catalyst types were also even greater if the catalyst also had a sulfur component contains. In these cases, conventional regeneration processes have generally been completely unsuccessful, so that the Catalytic converters remained permanently deactivated.

The object on which the invention is based is now to find a regeneration process for such deactivated hydrocarbon conversion catalysts from a porous support with a platinum group component, a germanium component and a halogen component to restore the original as much as possible Activity, selectivity and stability leads.

The inventive method for the regeneration of a carbon-containing deposits deactivated, stable sulfur-free hydrocarbon conversion catalyst from a porous support with a platinum group component, a germanium component and a halogen component by heating in a gas mixture containing oxygen, steam and hydrogen chloride and subsequent treatment in a hydrogen-containing gas at 300 to 600 ⁰ C for 0.5 to 5 hours is characterized in that the catalyst is first

a) with a sulfur-free gas mixture with 0.2 to 3 mol percent O _a and a molar ratio of H ₂ O: HCl of 20: 1 to 100: 1 heated to 375 to 450 ° C until the carbon-containing deposits are removed, then

b) heated with a sulfur-free gas mixture with 0.2 to 25 mol percent O ₂ and a molar ratio of H ₂ O: HCl of 20: 1 to 100: 1 for 0.5 to 10 hours at 450 to 550 ° C, then

c) flushing the catalyst free of oxygen and then

d) used as a hydrogen-containing gas in a sulfur-free gas mixture of hydrogen, H ₂ O and HCl with a molar ratio of H ₂ O: HCl of 20: 1 to 500: 1.

This process can be derived from a wide variety of hydrocarbon conversion processes Catalysts are regenerated, such as those from hydrocracking processes, isomeri

py dehydrogenation process, hydrogenation process, amounts, expediently about 0.5 to 2 mol percent H ₁ O

^^ Wefelungsverfahren, Cycüsierverfahren, Alky- and correspondingly about 0.005 Ms 0.1 Mc $> percent HCl [»^ experience, polymerizations, cracking process, Hy- contains both in this pretreatment as well as in ^ isGS ^ sierverfahren.RefonnicrverfahreauQdKoHi- the following process steps can of the chlorination of the same. In all of these hydrocarbons as such or in the form of chlorine-containing hot conversion processes, the catalysts are added to compounds which are deactivated under the conditions, which are gradually turned by deposition of carbon-containing materials, so that they are exchanged or replaced, such as chlorine , Alkyl chlorides and carbon tetrachloride have to be regenerated. material.

This process is also particularly suitable for such cata- io The pretreatment for stripping out unstable Schwelysatoren, which additionally contain a sulfur rock vnrd expediently at a temperature of about component. In this case, the deactivated 350 to 600 ⁰ C, preferably from about 400 to 550 ° C, fourth catalyst before the above described staged. The pressure is preferably carried out at follow at a substantially sulfur-free water about 1 to 50, wherein treating the best results in hydrogen at a temperature of about 350-15 relauv high pressure and relatively high temperature 600 ⁰ C until the outflowing Gas in the we get. The gas hourly space velocity, sentlichen free from hydrogen sulphide is the loading expressed in parts by volume of the gas per hour and treatment stream H ₁ O preferably contains also per volume part of the catalyst located in this reserved and HCl in a mole ratio of H ₈ O: HCl of treatment usually 100 to 25,000. The range about 20: 1 to 100: 1. ao action can be canceled if the

Some advantages of the process are as follows: The gas stream entering is essentially free of sulphides Treatment gas streams are not high levels of oxygen; H. if less than 10 ppm by volume Substance concentrations required. It does not need to be contained in and preferably less than 1 ppm by volume to be worked by water so th are. The one used in the pretreatment stage that no additional drying apparatus and no as hydrogen can also be returned to the treatment complex drying processes are required. In, if previously the hydrogen sulfide about The reduction can be quite low temperatures by washing with a strongly basic solution, such as be applied. The halogen content of the catalyst of an aqueous solution of an alkali salt or earth gate becomes about the original value again an alkali salt of a weak acid, especially one placed. The catalyst is not made by sulfur 30 solution of sodium hydroxide or sodium carbonate or sulfur oxides deteriorated with a pH of about 7-11.

According to a preferred embodiment, the duration of the pretreatment stage becomes stripping the treatment stage b) in two sub-stages of each labile sulfur is usually about 15 to because 0.5 to 5 hours carried out, ent- 30 or more hours.

neither heated in both sub-stages to 450 to 550 ° C. 35 Instead of this pretreatment, the catalyst can use the gas mixture of the handling in the first sub-stage only stripping of the labile sulfur also with a treatment stage a) and in the second sub-stage an essentially sulfur-free mixture of Water, the amount of oxygen of which increases by a factor of 1.5 to material and hydrocarbon feed material at 8, or the acidic conditions are treated in both substages such that the same amount of the gas mixture of treatment step a) 40 is converted at the same time hydrocarbons and by a factor of 1, 5 to 8 increases and in the first sulfur is stripped. This treatment takes place in the lower stage to 375 to 450 and in the second sub-usually with scrubbing with recycle gas,
stage heated to 450 to 55O ⁰ C. If the deactivated catalyst is not an unstable one

Another preferred embodiment of the sulfur contains, the pretreatment process described can be omitted in the treatment step. However, if such a preliminary stage a) was preceded by a gas mixture with 0.5 to 1.5 mol percent O ₂ treatment with hydrogen to remove the labile and a molar ratio of H ₂ O: HCl of 50: 1 sulfur, after the end of the yield 90: 1 used. Yet another expedient stripping of the remaining hydrogen by purging with an embodiment of the process used in which an inert gas such as nitrogen is removed from the catalyst treatment stage b) a gas mixture with 1 to 5 mol. In doing so, flushing is preferably carried out with a percent O ₂ and a molar ratio of H ₂ O: HCl inert gas _{stream which contains H 2} O and HCl in a molar ratio of 50: 1 to 90: 1 and of about 20: 1 to 100: 1

The regeneration of the hydrocarbon in the subsequent first stage (a) of the actual

Conversion process of deactivated catalyst is regeneration process is used to burn ^{out carbonaceous deposits, usually when about Va D' s 25} weight- 55 deposits are burned out of the catalyst. The regeneration can be used with 0.5 to 1.5 mol percent O ₂ , which is then carried out either in situ in the hydrocarbon conversion molar ratio of H ₂ O: HCl, preferably in a ventilation apparatus or in a separate plant, 50: 1 to 90: 1 lies. The amount of water in this gas can be guided. 60 mixture is preferably about 0.5 to 2 mol- If the deactivated catalyst contains labile sulfur, the remainder consists of an inert gas such as, ie such sulfur, which by stripping nitrogen, helium or carbon dioxide. The pressure that can be removed in this with hydrogen is now carried out first in the process stage with which the above-described pretreatment with hydrogen, the gas mixture is passed through the catalyst, preferably H _a O and HCl in a molar ratio of 65, appropriately about 30 atm Hourly headspace of H ₂ O: HCl from 20: 1 to 100: 1, preferably from about 100 to 25,000.
Contains 50: 1 to 90: 1. It is usually preferred that, at the end of this process step a), the relatively small hydrogen-containing deposits should essentially be removed from the pretreatment stream

5 6

Catalyst must be removed, depending on what to perform. You work in the first one

Amount of these carbonaceous deposits about sub-stage at a relatively low hydrogen

1/2 to 30 hours, usually about 20 to 30 hours, partial pressure of about 0.5 to 2 atm and in the second

requires lower stage with a relatively high hydrogen

A convenient means of PJT finding the termination 5 partial pressure of about 5 to 10 at of pressure and the

The first process stage consists in determining the flow velocity of the gas can be identical

the temperature difference from the inlet to the outlet with that of process stage a),

the reaction chamber containing the catalyst. In many cases it is advisable to

If this temperature difference is less than 5 ° C, the regenerated catalyst at increased tem-

process stage a) can be ended. In the case of drying to temperature, for example by treatment

that in the regeneration process several consecutive times for about 1 hour at 400 ⁰ C with a water

The switched-on catalyst-containing reactor chambers release hydrogen flow before the catalyst is released again

are used, only the temperature difference in is used for hydrocarbon conversion,

the last reactor chamber determined In the catalyst to be regenerated according to the invention

The task of the second process step b) can be performed by the porous carrier, for example

means that in the first process step naturally occurring or synthetically recovered

for remaining trace amounts of carbon-containing silicas, silica gels, clays or silicas

ger deposits and pass the metal grains, which have also been pretreated with acid

components of the catalyst to a high degree of oxidation, such as attapulgus clay, China clay,

to bring stage. ao diatomaceous earth, fuller's earth, kaolin, kieselguhr and

The gas mixture used in this stage contains pumice stone, or it can also be made of ceramic materials,

preferably about 1 to 5 mole percent O _x , and the porcelain, crushed firebricks or bauxite,

The molar ratio of H ₁ O: HCl is preferably from refractory inorganic oxides such as

50: 1 to 90: 1. Apart from the gas composition - alumina, titanium dioxide, zirconium oxide, chromium oxide, zinc

tion, the treatment time and the treatment temperature as oxide, magnesia, thorium oxide, boron oxide, silicic acid

temperature, fall the other reaction conditions of these alumina, silica-magnesia, chromium oxide-alumina,

Process stage into the alumina specified for stage a) boron oxide or silicic acid-zirconium oxide or from

Areas. It is expedient to work in this process- crystalline aluminosilicates, as naturally occurring

level in two sub-levels. Here again there is mendem or synthetically produced mordenite or

two alternatives. 30 faujasite consist. Appropriately, it consists of clay,

Either one deals in the first sub-level especially with γ-, ψ or ^ clay, especially γ- or η-

with the same gas mixture as in the process alumina, the smaller proportions of other heat-resistant

stage a), for 0.5 to 5 hours with an inorganic oxide, such as silica, zirconium oxide or

Temperature of about 450 to 550 ° C and increased in the magnesia can contain.

second sub-stage, the amount of oxygen in the gas- a bulk density of about 0.30 to 0.70 g / cm ³ ,

misrhes by a factor of 1.5 to 8, with the mean pore diameters of about 20 to 300A,

treatment in the second sub-stage again during a pore volume of about 0.10 to 1.0 ml / g and a

0.5 to 5 hours and at the same temperature as the surface from 25 to 500, preferably from 100 to

takes place in the first lower level. But above you increase 500 m ² / g · A typical carrier for the invention

already in the first sub-level the oxygen content by ♦ <> measure to be regenerated catalysts is y-alumina in

a factor of 1.5 to 8, preferably about 2, the shape of spherical particles with a relatively small

compared to the gas diameter used in step a), such as about 1.6 mm, a bulk density

mixed, but treated with this gas mixture increased by about 0.5 g / cm ³ , a pore volume of about

Oxygen content / g at a temperature from 375 to 0.4 ml / g and a surface area of about 175.m. ²

45O ⁰ C for 0.5 to 5 hours and then treated \ 5 The germanium component is in the

to be regenerated or regenerated according to the invention in the second sub-stage with the same gas

mixed as in the first sub-stage for 0.5 to 5 hours, catalyst expediently in an oxidation stage

but now at 450 to 550 ° C. half of that of the elemental metal, d. H. in

During the process stage c) that now follows, the oxidation stage is + 2 or + 4 the catalyst with a suitable inert gas with a germanium component of 5 ° as a chemical compound, Oxygen purged where it is not required, such as oxide, sulfide, or halide, or bonded to to dry the plant during this stage, since the carriers are present. The amount of germanium subsequent Reduction stage under moist conditions in the catalyst to be regenerated is carried out. The completion of the process is preferably about 0.01 to 5 percent by weight, Step c) can be carried out by determining the oxygen level, calculated on the basis of the elements and without taking it into account in the purge gas after passing through sighting the carbonaceous deposits that the catalyst can be determined. the best results are achieved with catalyst contents

The following reduction stage d) has the germanium component of about 0.05 to 2 ge

gift, the platinum group component of the catalyst by weight.

to be reduced to the elementary state, while the 60 The platinum group component can in the too active

Germanium component remains in the oxidized state. regenerating catalyst as a compound, such as oxide,

The delayed reduction temperature is sulfide or halide, or as elemental metal

225 to 425 ° C, the preferred molar ratios of. The amount of platinum is preferably

H ₁ O: HCl at 20: 1 to 100: 1, especially at 50: 1 group component of the catalyst about 0.01 to

up to 90: 1. The concentration of H ₂ O in the hand- 65 2 percent by weight of the catalyst, calculated on

processing gas of process stage d) is preferably based on elements and without consideration of carbon

about 0.5 to 2 Mo percent. In many cases it is advisable to remove deposits containing carbon. Particularly good results

This reduction stage d) in two sub-stages was also 0.05 to 1 percent by weight of the

Platinum group component obtained. The preferred germanium dioxide crystals were made into a porcelain platinum group component is platinum itself. boat given and with essentially pure

The halogen component can be fluorine, bromine or hydrogen at about 65O ⁰ C for about 2 hours chlorine and is expediently reduced in the catalyst. The resulting grayish-black solid, at a concentration of about 0.5 to 3.5, preferably 5, was dissolved in chlorinated water. About 0.6 to 1.2 percent by weight of a second aqueous solution was then prepared which contained chloroplarechnet on the basis of elements and not including acid and hydrochloric acid. The removal of carbonaceous deposits. In one of the two solutions were intimately mixed with one another, the merized or hydrocracking catalyst is the halo and, for the impregnation of the γ-alumina particles, usually greater, expediently in the range of 10, so that the finished catalyst is 0.25 to about 10 percent by weight , preferably in percent Ge and 0.37 percent by weight Pt. To range from about 1 to 5 percent by weight. a uniform distribution of both metal components

To ensure the atomic ratio of germanium components in the carrier, the

to platinum group component in the to be regenerated carrier particles to the impregnation mixture under con-

the catalyst is expediently added in the range of 15 hours of stirring. The volume of the solution

about 0.1: 1 to 10: 1, especially in the range of about 2 times the volume of the carrier particles. The

1: 1 to 6: 1. The total content of germaniumkom impregnation mixture was about V ₂ hours at about

component and platinum group component is held, calculated 21 ⁰ C in contact with the carrier particles,

net based on elements, expediently at 0.1 to After that, the temperature of the impregnation agent was: -

3.0 percent by weight of the catalyst. ao cal increased to about 107 ⁰ C, and the excess

In addition, the catalyst to be regenerated can be evaporated in about an hour. the

As mentioned, dry particles resulting from sulphidation of sulfur were also subjected to calci-

contain, such as about 0.05 to 0.50 weight percent. nation in air at about 496 ° C for about one

This sulfur component can be subjected to hour in the catalyst. The calcined beads were

by presulfiding, as treated with a mixture 25 with a stream of air, the H ₂ O and HCl in

of hydrogen and a sulfur compound such as a molar ratio of about 40: 1, and these

Hydrogen sulfide or low molecular weight mercap treatment was carried out for about 4 hours

tan, or by injecting sulfur or 524 ° C, to reduce the halogen content of the catalyst particles

sulfur-containing compounds during the coal- to a value of about 0.90. The resulting

Catalyst particles containing hydrogen conversion processes in the catalyst were analyzed, and

have been introduced. With the above regeneration it was found that, on the basis of elements, it was approximately

process, catalysts can be regenerated, 0.375 percent by weight of platinum, about 0.25 percent by weight

which is about 0.01 to 5 percent by weight or more percent germanium and about 0.85 percent by weight

fei contained, with the usual amount of sulfur in the case of chloride,

about 0.05 to 1 percent by weight. 35 The catalyst particles became dry

Preferably after this regeneration process treated prereduction treatment by subjecting them

Delte catalysts contain, on an elemental basis, about 1 hour with an essentially pure water

calculated and without taking into account the flow of carbon containing less than 20 ppm by volume of H ₂ O

ger deposits contained about 0.6 to 1.2 percent by weight, at about 538 ⁰ C, a pressure slightly above

Chlorine, about 0.05 to 1 percent by weight platinum, about 40 atmospheric pressure and a hydrogen flow

0.05 to 2 percent by weight germanium and about 0.05 speed corresponding to an hourly gas

treated up to 1 percent by weight sulfur at an alumina roughness rate of about 720,

carrier. The described rule is particularly suitable. Table I shows the compositions of the fri-

regeneration process for regenerating reforming catalytic converters and the deactivated catalytic converter (on element

analyzers. 45 basis). The catalyst was in one

sulfur-free reforming process used in which

Example measures were taken to exclude sulfur. Consequently, it essentially comprised the

The example demonstrates the regeneration process deactivated state, no labile sulfur, and

according to the invention by contrasting the 50 there was therefore a preceding sulfur stripping step

Results that are not required in an accelerated reform
Renal stability test with the fresh catalyst and
with the regenerated catalyst.

The fresh catalyst was prepared as follows

6: A clay carrier made of spheres of 1.6 mm 55 Composition of the catalysts

Diameter was made in such a way that one

an aluminum hydroxyl chloride sol by dissolving catalyst, weight percent

essentially pure aluminum pellets in a Pt Ge α SC
Produced hydrochloric acid solution, to the resulting

ting sol hexamethylenetetramine added and the 60 fresh 0.375 0.25 0.85 0.1 0

resulting solution by dropping in an oil bath Deactivated 0.375 *) 0.25 *) 0.85 *) <0.1 6.26

to form spherical alumina hydrogel particles. Regenerated 0.375 0.25 1.02 <0, l <0, l

gelled. The resulting hydrogel particles were.) Based on carbon-free catalyst,
aged and washed with an ammoniacal solution, and finally dried and at elevated 65

Temperature calcined, whereby spherical particles The deactivated catalyst was then with a regenerated from y-alumina at a level of about 0.3 weight increments, which is a preferred out percent bound chloride got. represents embodiment of the invention. A collation

The list of conditions and gas flows used in each stage is shown in Table II. In view of the fact that each of these stages has been explained in detail above, here is one

10

such description is not repeated. It should be noted, however, that the gas streams used are free of Sulfur and sulfur compounds were and are used in a single pass.

Table II

Compilation of the regeneration process

step Stioma confluence
Mole percent Temperature, ⁰ C hourly
Gas compartment
speed Pressure, atm. Time, hours Mole ratio
HjO / HCl a) 0.01% HCl, 0.71% H ₈ O,
1.0% O, and N ₈ 400 750 1.3 22nd 72.1 bj) 0.01% HCl, 0.71% H ₂ O,
1.0% O ₂ and N ₈ 500 750 1.3 1 72.1 0.01% HCl, 0.71% H ₂ O,
2.0% O ₈ and N ₈ 500 750 1.3 2 72.1 c) N ₈ 375 750 1.3 1 0 d) 0.002% HCl ₁ 0.82% H _a O, 370 750 1.3 2.5 400: 1

The regenerated catalyst was subjected to the reforming stability test like the fresh catalyst. The stability test was carried out in a laboratory facility with a reactor that had a fixed catalyst layer contained, a hydrogen separation device, a dryer with a sodium large surface, a butane removal column and other conventional equipment such as pumps, compressors, Heating and cooling equipment carried out.

The flow diagram used in this system is as follows:

1. The feed material and hydrogen are mixed, heated to transition temperature and introduced into the reactor.

2. A part stream is withdrawn from the reactor, cooled to about 13 ⁰ C and separating led to the hydrogen, wherein a hydrogen-rich gas is separated from a liquid hydrocarbon phase.

3. The hydrogen-rich gas phase is withdrawn and part of it is blown out of the system, in order to have a pressure control, another part is passed through the dryer with sodium large surface, compressed again and finally returned to the reactor.

4. The liquid phase from the separation device is fed to the butane removal column, in which the light Entfraktioren is taken off at the top and a C ₆ + reformate is obtained at the bottom.

The properties of the feedstock used in the accelerated stability test are in Table III compiled.

Table III

Analysis of Severe Kuwait Naptha

Specific weight at

15.6 ° C / 15.6 ° C 0.7374

Initial boiling point, ⁰ C 84

10% boiling point, ⁰ C 96

50% boiling point, ⁰ C 124

90% boiling point, ⁰ C 161

Final boiling point, ⁰ C 182

Sulfur, ppm by weight 0.5

Nitrogen, weight ppm 0.1

Aromatics, percent by volume 8

Paraffins, percent by volume 71

Naphthenes, percent by volume 21

Water, ppm 5.9

Octane number, F-I clear 40.0

The reforming stability test consisted of six periods of 23 hours each with a 12-hour start-up period followed by a 12-hour test period. the

Conditions used in these tests were as follows: a pressure of 7.8 at, a molar ratio of hydrogen to hydrocarbon of 9: 1, an hourly Liquid space velocity of 1.5 and a temperature continuously adjusted to

that clear to the C ₅ received an octane number of 102 FI + reformate.

The results of these comparative tests are given in Table IV, viz

1. as temperatures that were required during each period to reach the target octane number, 2. as excess recycle gas (RFG) obtained from the hydrogen separation device

was, namely in parts by volume of gas at 15 ° C and 1 atmosphere per part by volume of liquid charge at 15 ⁰ C,

3. as the top gas of the butane removal column (KG) in parts by volume per part by volume,

4. as the ratio of butane remover gas to total gas,

5. as the C ₅ + yield calculated on the volume percent of the feed, and

6. as the amount of CH ₄ in parts by volume per part by volume.

Table IV

Comparison of the fresh and regenerated catalyst in the accelerated reforming stability test

fresh
regenerated Period no.
1 2 523
521 3 526
525 4th 530
527 5 532
531 6th 534
534 1.) Temperature ⁰ C fresh
regenerated 517
519 1700
1775 1790
1796 1788
1794 1767
1772 1773
1792 2.) RFG fresh
regenerated 1733
1788 65
65 66
62 63
70 68
63 68
63 3.) KG fresh
regenerated 60
35 0.037
0.035 0.036
0.033 0.034
0.038 0.037
0.034 0.037
0.034 4.) KG fresh
regenerated 0.033
0.019 77.0
78.8 77.2
77.7 77.6
76.6 76.4
78 _s 0 77.0
77.0 Total gas fresh
regenerated 77.6
78.5 75
67 78
67 77
70 83
65 81
70 5.) C ₆ + 77
74 6.) CH ₄

The temperature required to obtain a given octane number under constant conditions and with the same feedstock is a a good measure of the activity of the catalyst, therefore it can be seen from table V that the regenerated Catalyst required a temperature to achieve octane number about the same as that corresponding fresh catalyst, indicating that the regenerated catalyst is as active as the fresh Was a catalyst.

The C ₆ + yield at the same octane number is an indication of the catalyst selectivity for reforming processes, and when comparing the C _s + yield in Table IV for the fresh catalyst with that for the regenerated catalyst it can be seen that the regenerated catalyst has a selectivity which is equivalent to that of the fresh catalyst. With regard to stability, the rate of change in temperature which is required to obtain a certain octane number and a certain C ₅ yield over time is usually used as a measure. From Table IV it can be seen that the stability for the fresh catalyst and the regenerated catalyst are comparable.

Claims (4)

Patent claims: 1. A process for the regeneration of a hydrocarbon conversion catalyst, deactivated by carbonaceous deposits and free of labile sulfur, from a porous support with a platinum group component, a germanium component and a halogen component by heating in a gas mixture containing oxygen, steam and hydrogen chloride and subsequent treatment in a hydrogen-containing gas bc: 100 to 600 ⁰ C for 0.5 to 5 hours, characterized in that the catalyst is first ^{a) heated to 375 to 450 °} C. with a sulfur-free gas mixture with 0.2 to 3 mol percent O ₂ and a molar ratio of H ₂ O: HCl of 20: 1 to 100: 1 until the carbon-containing deposits are removed, then b) heated with a tail I-free gas mixture with 0.2 to 25 mol percent O ₂ and a molar ratio of H ₂ O: HCl of 20: 1 to 100: 1 for 0.5 to 10 hours at 450 to 550 ° C, then c) flushing the catalyst free of oxygen and then d) a sulfur-free gas mixture of hydrogen, H ₂ O and HCl with a molar ratio of H ₂ O: HCl of 20: 1 to 500: 1 is used as the hydrogen-containing gas. 2. The method according to claim 1, characterized in that the treatment step b) into two sub-stages of 0.5 performs to 5 hours while heating either in two sub-stages 450 to 55O ⁰ C, in the Eisten sub-stage, the gas mixture of the Treatment stage a) is used and the amount of oxygen in the second sub-stage increases by a factor of 1.5 to 8 or the amount of oxygen in the gas mixture of treatment stage a) increases by a factor of 1.5 to 8 in both sub-stages and to 375 in the first sub-stage heated to 450 and in the second sub-stage to 450 to 550 ° C. 3. The method according to claim 1 and 2, characterized in that a gas mixture with 0.5 to 1.5 mol percent O ₂ and a molar ratio of H ₂ O: HCl of 50: 1 to 90: 1 is used in treatment step a) . 4. The method according to claim 1 to 3, characterized in that a gas mixture with 1 to 5 mol percent O ₂ and a molar ratio of H ₂ O: HCl of 50: 1 to 90: 1 is used in treatment step b).