WO2014154509A1 - Passivation of a zeolite catalyst for dehydroaromatization - Google Patents

Abstract

The invention concerns a method of producing a catalyst for dehydroaromatization, characterized in that (a) a catalyst containing a zeolite and at least one catalytically active metal is (b) passivated with a silicon-containing compound; and is (c) then optionally calcined.

Description

 The present invention relates to a process for the preparation of a catalyst for the dehydroaromatization, which is characterized in that a) a catalyst comprising a zeolite and at least one catalytically active metal, b) with a silicon passivated compound is passivated and

c) is then optionally calcined.

Benzene can be prepared from methane or other lower alkanes or alkenes by dehydroaromatization, e.g. in WO 2009/124960 is described. For this, the alkanes are heated at high temperatures, e.g. from 300 to 1000 ° C, reacted at a catalyst. Naturally, special requirements apply to the catalyst at such high temperatures. He must remain active for as long as possible at these high temperatures and ensure the highest possible conversion with the highest possible selectivity. It is easy at these high temperatures for the formation of carbon in the form of coke, which deposits on the catalyst. In particular, acidic sites on the catalyst surface favor the formation of carbon and its deposition.

According to US Pat. No. 6,552,243, catalysts are used for the dehydroaromatization whose surface has been passivated with the aid of a silicon compound to form a silicon layer. The passivation of catalysts, in particular zeolite catalysts with the aid of silicon compounds is also known from WO 2007/080240 and WO 2005/014169. In the passivation process described in WO 2005/014169, the active metals of the catalyst are introduced only after passivation. Also in the examples of

WO 2007/080240, the passivation takes place subsequently; Accordingly, in the description of WO, it is stated that the passivation (process steps b) and c) in WO) first takes place and only then the active metal (process step a) in WO) is added. Thus, it should obviously be avoided that the activity of the metals is impaired by the passivation.

In principle, it is desirable to further reduce the coking and deposition on catalysts in the dehydroaromatization and to further extend the service life of the catalyst with high yield and selectivity. At the same time, the method used for passivation should be simplified. In particular, it appears advantageous, starting from an already passivated catalyst base body subsequently to be able to apply different active metals as needed.

The object of the present invention was therefore a simplified process for the passivation of catalysts and a simplified and improved process for dehydroaromatization using a passivated catalyst. In particular, coke formation and deposition during dehydroaromatization should be reduced. Accordingly, the method defined above was found. Also found was a dehydroaromatization process using such a passivated catalyst. To a)

 The starting material of the process according to process step a) is a catalyst which contains a zeolite and catalytically active metals.

Zeolites are naturally occurring or artificially produced microporous substances having a three-dimensional framework structure of neutral Si04 tetrahedra and negatively charged AlO 4 tetrahedra and optionally further metal / oxygen compounds in the form of tetrahedra. Preference is given to zeolites which consist of more than 80% by weight, more preferably more than 95% by weight, of neutral Si0 ₄ tetrahedra and negatively charged Al0 ₄ tetrahedra.

According to the different composition of the unit cell, a distinction is made between various basic types which are characterized by 3 letters according to an international nomenclature of the international zeolite association, e.g. MFI, EUO, MTT. Preference is given to a zeolite of the structure type MFI.

The MFI type of structure is a 10-ring zeolite, i. the circumference of the pores corresponds to a ring of 10 atoms in total Si, Al and optionally other metal; these 10 atoms are bridged by oxygen.

As zeolites of the structural type MFI are e.g. TS-1 or ZSM-5 known. Most preferably it is ZSM-5.

The pore diameter of the ZSM-5 is generally about 5.5 angstroms uniformly.

The ZSM 5 consists mainly of Si04 tetrahedra and contains only small amounts of negatively charged aluminum tetrahedra. The ratio Si / Al preferably corresponds to a ratio of SiO 2 to Al 2 O 3 of 10: 1 to 200: 1. Cations to the negatively charged aluminum tetrahedra are generally hydrogen (acidic H form) or alkali cations or ammonium cations.

This is preferably a zeolite in the H form. The zeolite may also contain small amounts of alkali metal cations in the H form, preferably the content of alkali metal cations is less than 1% by weight, in particular less than 0.1% by weight and particularly preferably less than 0.01% by weight. Synthetic zeolites can be prepared from an aqueous solution containing a Si compound (Si source, eg any silica such as fumed or precipitated Silka, water glass, silica gel, silanes or siloxanes), an aluminum compound (Al source, eg aluminum hydroxide), a so-called template and if appropriate, further additives, in particular for adjusting the pH, are prepared. In principle, it is possible to introduce active metals already in the production of the zeolite from the Si and Al sources.

The template is an organic compound that serves as a placeholder for the pores.

The solution is heated, forming a solid from the constituents. The organic compound (template) is finally removed by calcination (heating to very high temperatures), only now are the pores contained in the solid body freely accessible. Suitable templates are e.g. Allyltripropylammonium hydroxide or tetrapropylammonium hydroxide. The catalyst used according to the invention in step a) preferably contains a binder in addition to the zeolite.

Suitable binders are Si-containing binders, e.g. colloidal silica, polysiloxanes or mixtures thereof.

In a preferred embodiment, the zeolite is first mixed with the binder. In particular, zeolite and binder are mixed in the form of liquid preparations (solutions or dispersions). The proportion of the binder may be e.g. 5 to 200 parts by weight per 100 parts by weight, in particular 10 to 100 parts by weight per 100 parts by weight of zeolite.

After mixing the zeolite with the binder, a shaping step can be carried out; In this case, the mixture is processed according to the methods known in the art to form bodies. In this case, the shaping processes to be mentioned are, for example, spraying of a suspension containing the zeolite or the catalyst mass into powders, tabletting, pressing in the moist or dry state and extrusion. Two or more of these methods can also be combined. Auxiliaries such as pore formers and pasting agents or else other additives known to the person skilled in the art can be used for shaping. Possible pasting agents are those compounds which improve the mixing, kneading and flow properties. In the context of the present invention, these are preferably organic, in particular hydrophilic polymers such as cellulose, cellulose derivatives such as methylcellulose, starch such as potato starch, wallpaper pastes, acrylates, polyacrylates, polymethacrylates, polyvinyl alcohols, polyvinyl pyrrolidone, polyisobutylene, polytetrahydrofuran, polyglycol ethers, fatty acid compounds, wax emulsions , Water or mixtures of two or more of these compounds. In the context of the present invention, pore formers which can be dispersed, suspended or emulsified in water or aqueous solvent mixtures are, for example, polyalkylene oxides, polystyrene, polyacrylates, polymethacrylates, polyolefins, polyamides, polyesters, carbohydrates, cellulose, cellulose derivatives, such as example, methyl cellulose, sugar natural fibers, pulp, graphite or mixtures of two or more of these compounds. Pore formers and / or pasting agents are preferably removed after deformation by at least one suitable drying and / or calcining step from the resultant shaped body.

The resulting shaped articles may be powders having a desired distribution of the powder size or shaped articles having a uniform, defined geometry. Thus, for example, the catalysts may be spherical (hollow or full), cylindrical (hollow or full), ring-, satin-, star-, honeycomb- or tablet-shaped. Furthermore, extrudates may be used, for example, in extruded, trilobium, quatrolob, star or hollow cylindrical form. Furthermore, the catalyst mass to be molded can be extruded, calcined and the extrudates thus obtained broken and processed into chips or powder. The grit can be separated into different sieve fractions. A preferred sieve fraction has the grain size 0.25 to 0.5 mm. In a preferred embodiment, a powder, in particular by spray drying, is produced from the mixture of binder and zeolite.

The catalyst used according to a) contains at least one catalytically active metal. Preferably, the catalyst contains a plurality of catalytically active metals.

The term metals is understood here to mean metals in elemental form but also in the form of metal ions or central atoms of complex compounds. In particular, it is metal ions, which are present as salts. The catalytically active metals may be any metals of the periodic table.

In a preferred embodiment, the catalyst contains one or more active metals selected from Mo, Mn, Cr, Zr, V, Zn, Cu, Ni, Fe, W, Ga, Ge and Co.

The catalyst particularly preferably contains one or more active metals selected from Mo, Ni, Cu, Fe, Zn.

Most preferably, the catalyst contains Mo and additionally one or more metals. In a most preferred embodiment, the

Catalyst Mo and additionally one or more metals selected from Fe, Cu, Ni, Zn.

Preferably, the catalyst prepared according to all process steps a) to c) 1 to 20 wt.%, Particularly preferably 3 to 20 wt.% Of active metals, based on the total weight of the catalyst. In a particularly preferred embodiment, the catalyst prepared according to all process steps a) to c) contains 1 to 15 wt.% Molybdenum (Mo), in particular 3 to 12 wt.% Mo and 0 to 10 wt.%, Preferably 0.5 to 5 % By weight of other active metals, for example those mentioned above, preferably Fe, Cu, Ni, Zn.

It is an essential feature of the invention that the catalyst already contains active metals prior to passivation in process step b).

In a particular embodiment, more than 80% by weight, in particular more than 90% by weight, particularly preferably more than 98% by weight and in particular 100% by weight, of the active metals which the catalyst produced by the process according to the invention contains in total, before Passivation in the catalyst or applied.

The active metals can be applied wet-chemically or dry-chemically to the zeolite or the powder of zeolite and binder.

Wet-chemically, the active metal can be applied in the form of aqueous, organic or organic-aqueous solutions of its salts or complexes by impregnating the zeolite with the appropriate solution. The solvent may also be supercritical CO 2. The impregnation can be carried out by the incipient wetness method, in which the porous volume of the zeolite is filled up with approximately the same volume of impregnating solution and, optionally after maturation, the support is dried. You can also work with an excess of solution, the volume of this solution is greater than the porous volume of the zeolite. In this case, the zeolite is mixed with the impregnating solution and stirred for a sufficient time. Furthermore, it is possible to spray the zeolite with a solution of the salt of the active metal. There are also other, known in the art production methods such as precipitation of the active metal on the zeolite, spraying a solution containing a compound of the active metal, sol impregnation, etc. possible. In the case of molybdenum, particularly suitable compounds (NH 4) 6Mo7024, ammonium heptamolybdate (NH 4) 2Mo 2 O 7, MoO 2, MoO 3, H 2 MoO 4, Na 2 MoO 4, Mo oxalates with Mo in various oxidation states,

 (NH3) 3Mo (CO) 3 and Mo (CO) 6. After the application of the active metal, the catalyst is dried at about 80 to 130 ° C usually for 4 to 20 hours in vacuo or in air.

The elements Mn, Cr, Zr, V, Zn, Cu, Ni, Fe, W, Ga, Ge and Co are preferably applied wet-chemically to the zeolite. The metal salts used here are preferably the nitrates, such as copper nitrate, nickel nitrate, iron nitrate and cobalt nitrate, but other salts known to the person skilled in the art for wet-chemical application can also be used. These include the halides, in particular chloride, acetate, alkaline carbonates, formate, tartrate, acetate, complexes with ligands such as acetylacetonate, amino alcohols, EDTA, carboxylates such as oxalate and citrate and Hydroxycarbonsäuresalze.

In one embodiment, the solution which applies the active metal or metals to the zeolite contains at least one complexing agent. Preferably, the Complexing agents selected from the group acetylacetonate, amino alcohols, EDTA, carboxylates such as oxalate and citrate and hydroxycarboxylic acid salts. Particular preference is given to using EDTA. Dry chemical, the active metal can be applied, for example, at higher temperatures from the gas phase by deposition on the zeolite. In the case of molybdenum, for example, gaseous Mo (CO) 6 is suitable for this purpose.

To b) and c)

The catalyst according to a) is passivated in process step b) with a silicon-containing compound.

The catalytic reaction takes place at the acidic sites in the pores of the catalyst. The acidic centers outside the pores, i. on the freely accessible surface of the catalyst, promote undesirable coke formation on the surface of the catalyst. These acidic sites can be passivated by reaction with a silicon compound and formation of a polymeric silicon layer, generally a silicon dioxide layer. Suitable silicon compounds are, in particular, those which are formed by polycondensation or polyaddition, e.g. at elevated temperature in polymeric silicon compounds, especially those having a basic structure of silica, can be converted.

Preference is given to non-polymeric silicon compounds having a molecular weight of less than 5000 g / mol, in particular less than 1000 g / mol and particularly preferably less

500 g / mol.

Preferably, the silicon compounds have at least one molecular diameter greater than the diameter of the pores of the zeolites used. In the case of the preferred zeolite ZSM-5, therefore, the silicon-containing compounds have at least a diameter greater than 5.5 angstroms.

Silanes, siloxanes or silazanes may be mentioned in particular as suitable silicon compounds.

Silanes are silane (SihU) and its derivatives, ie compounds in which at least one hydrogen is replaced by another substituent. Preference is given to silanes in which one to four H atoms are substituted by organic groups, halogens or hydroxyl groups. Suitable organic groups are, for example, alkyl groups, aryl groups, alkoxy groups or aroxy groups. At least two of the organic groups are preferably those which condense an Si-O-Si basic structure with elimination of water to form a polymeric compound. Particular preference is given to silanes having 2 to 4 alkoxy groups, these are preferably around C 1 -C 10 -alkoxy groups or C 1 -C 4 -alkoxy groups. Specifically, mention may be made of tetraalkoxysilanes such as tetramethoxysilane or tetraethoxysilane.

Siloxanes are compounds containing two oxygen atoms linked by oxygen atoms. The two Si atoms are substituted by H atoms or organic groups. The above statements on the silanes apply correspondingly to the organic groups. Preferably, the siloxanes contain at least two organic groups which undergo a condensation reaction; in particular, these are alkoxy groups listed above. Silazanes are compounds having two Si atoms of the basic structure connected via a nitrogen group

(R-) ₃ Si-NH-Si (-R) ₃

Preferably, the radicals R are organic groups; Alkyl groups or alkoxy groups. Suitable silazanes are e.g. Hexaalkylsilazanes, e.g. Hexa-C1-C10-alkylsilazanes. Mention may be made of hexamethylsilazane by way of example:

(CH ₃ -) ₃ Si-NH-Si (-CH ₃ ) ₃ .

The catalyst is first contacted with the silicon compound. The catalyst may e.g. with the liquid silicon compound or a liquid preparation of the silicon compound, e.g. a solution in a suitable solvent (impregnation). To ensure a good distribution of the silicon compound on the surface, e.g. liquid preparations, or solutions containing 0.01 to 10 wt.%, Preferably 0.1 to 5 wt.% Of the silicon compound.

In the case of silazanes, such as hexamethylsilazane, e.g. Solutions of silazanes in organic solvents, preferably polar solvents such as tetrahydrofuran suitable.

The silicon compound may also be applied to the catalyst in gaseous form. For this purpose, the silicon compound can be heated to temperatures above its boiling point and brought into contact with the catalyst.

 Preferably, the silicon compound is mixed with other gases, e.g. Inert gas such as nitrogen or noble gas or the gaseous starting materials of the later reaction, e.g. Methane or natural gas, brought into contact with the catalyst.

In a particularly preferred embodiment, this other gas may be contacted with the silicon compound at temperatures below the boiling point of the silicon compound and take up the silicon compound to saturation.

The gas mixtures preferably contain 0.01 to 10% by volume, in particular 0.1 to 2% by volume, of the silicon compound.

By diluting the silicon compound in the gas phase with another gas, a good distribution of the silicon compound on the surface can be ensured. The catalyst can be present as a fixed bed or fluidized bed in the treatment with the gaseous silicon compound in a suitable apparatus, for example also the reactor used for a later dehydroaromatization. In a preferred embodiment of the present invention, the catalyst is present as a fluidized bed.

The catalyst treated with the silicon compound is then optionally dried to remove solvent. Such drying may be necessary when impregnating the catalyst with a liquid silicon compound or a liquid preparation of the silicon compound. The drying may e.g. in a separate process step prior to further reacting the silicon compound to a polymeric silicon layer at temperatures of from 20 to 150 ° C and optionally under reduced pressure, e.g. done under vacuum.

The reaction of the silicon compound to form a polymeric silicon layer is preferably carried out at elevated temperature.

The reaction to the polymeric silicon layer may be e.g. at temperatures of 100 to 800 ° C, in particular 200 to 700 ° C, particularly preferably 300 to 700 ° C take place (calcination). The temperature is usually increased slowly over a longer period and maintained the maximum temperature reached over a longer period of time. It may be e.g. Total trading for a period of 2 to 20 hours.

The finally obtained, surface-passivated catalyst preferably has a content of 0.001 to 5% by weight, particularly preferably 0.01 to 1% by weight of the Si-containing compound or of the reaction product obtained therefrom after a final calcination. The above quantity is related only to the Si atom of the silicon-containing compound, because the content of the silicon introduced by the silicon compound does not change even in the further reaction of this silicon compound.

For use of the catalyst

The catalyst obtained by the above production method is preferably used as a catalyst for dehydroaromatization. In particular, the catalyst is used for the dehydroaromatization of alkanes and alkenes.

It is preferably the dehydroaromatization of a C1 -C4 aliphatic educt stream to benzene and optionally higher aromatics. The C1-C4 aliphatic compounds may be, for example, methane, ethane, propane, n-butane, i-butane, ethene, propene, 1- and 2-butene or isobutene. In particular, the dehydroaromatization is a process for the preparation of benzene from methane or mixtures of aliphatics consisting of more than 70% by weight, more preferably more than 90% by weight, based on the total amount of aliphatic, of methane , In particular, natural gas can be used as the methane or mixture of aliphatics.

In addition, gaseous compounds which do not dehydroaromatize, e.g. Hydrogen, water, carbon monoxide, carbon dioxide, nitrogen or noble gases. Inert gases such as nitrogen or noble gases are used to reduce the partial pressure. Other gases, such as carbon monoxide or carbon dioxide, may reduce coke formation.

Preferably, it is a dehydroaromatization under non-oxidative conditions. For this purpose, the concentration of oxidizing agents such as oxygen or nitrogen oxides in the educt stream should preferably be below 5% by weight, preferably below 1% by weight, more preferably below 0.1% by weight. Most preferably, the mixture is free of oxygen and nitrogen oxides.

The catalyst may optionally be activated in advance. Activation is generally carried out at lower temperatures than those of the later reaction and a defined temperature / time curve to complete as completely as possible chemical reactions in or on the catalyst. By such activation, if necessary, the activity of the catalyst can be increased. Preferably, the catalyst is contacted for activation with a gas of appropriate temperature. A previous activation may e.g. with a C1 -C4 alkane, e.g. Methane, ethane, propane, butane or a mixture thereof, preferably methane, take place. The activation can be carried out at a temperature of 250 to 650 ° C, preferably at 350 to 550 ° C, and a pressure of 0.5 to 100 bar, preferably at 1 to 50 bar, in particular 1 to 10 bar. Usually, the GHSV (Gas Hourly Space Velocity) at activation is 100 to 4000 h-1, preferably 500 to 2000 h-1.

The catalyst can also be activated with a gas stream containing H2; the H2 gas stream may additionally contain inert gases such as N2, He, Ne and Ar.

Preferably, activation takes place with a C 1 -C 4 -alkane, if appropriate in a mixture with hydrogen. Particularly preferably, the activation is carried out with methane, optionally in admixture with hydrogen. The dehydroaromatization of C1-C4-aliphatic in the presence of the catalysts described above at temperatures of 400 to 1000 ° C, preferably from 500 to 900 ° C, more preferably from 600 to 800 ° C, in particular from 650 to 800 ° C, at a pressure of 0.5 to 100 bar, preferably at 1 to 50 bar, more preferably at 1 to 30 bar, in particular 1 to 10 bar. The supply of the reactant stream into the reactor can be carried out, for example, with a GHSV (gas hourly space velocity) of 100 to 10,000 h-1, preferably 200 to 3000 h-1. The catalysts can be regenerated with decreasing activity by customary methods known to those skilled in the art. Particularly suitable is the regeneration of the catalysts with hydrogen.

 For this purpose, the reaction can be stopped and the catalyst can be regenerated with hydrogen. The reaction cycle and the regeneration cycle can alternate, and the reactant stream and hydrogen can be passed alternately over the catalyst.

 Advantageously, hydrogen can be added to the reactant stream so that regeneration takes place simultaneously with the reaction. In particular, the educt stream in the regeneration phase may contain more than 10% by volume, in particular more than 30% by volume and more preferably more than 50% by volume of hydrogen.

As reactors for carrying out the dehydroaromatization, e.g. Tubular or tubular reactors suitable. The catalyst prepared according to the invention can be present in these reactors as a fixed bed or fluidized bed. With the catalyst prepared by the process according to the invention, the dehydroaromatization of C1 to C4 aliphates, in particular of methane, can be carried out with high yields and selectivities. In particular, high yields and selectivities of benzene are achieved. The deposition of coke on the catalyst is significantly reduced by the passivation; As a result, the life is increased and the time intervals between necessary regeneration of the catalyst significantly extended.

The application of active metal prior to passivation provides process advantages, e.g. For example, the active catalyst can be passivated directly in the dehydroaromatization reactor, thus saving a previous, separate dehydroaromatization process step.

Examples Preparation of a catalyst of zeolite and binder

As the zeolite, ZSM-5 in the H-form (H-ZSM-5) was used. In order to remove residual alkali cations, an ammonium exchange (exchange of residual alkali cations for ammonium cations and expulsion of ammonium as ammonia).

For this purpose, 19 kg of H-ZSM-5 were added to a solution of 19 kg of ammonium nitrate in 170 liters of water and stirred at 80 ° C for 2 hours. After cooling, the suspension was filtered in a filter press and washed with water. The process was repeated once more and the filter cake finally dried overnight at 120 ° C. The obtained H-ZSM-5 was milled in the form of a 50% aqueous suspension in an agitating mill until the D50 value of the particle size distribution was <3 μm, that is to say that more than 50% by weight of the zeolite particles had a diameter < 3 μηη had.

To the aqueous suspension of the ground zeolite was added polymethoxysiloxane and colloidal SiO 2 as a binder. The mixture was stirred at 60 ° C for 4 h.

The aqueous mixture of H-ZSM-5 and binder was spray dried in a sputter dryer (Niro) using nitrogen as a sputtering gas.

The spray-dried catalyst particles were then further dried overnight at 120 ° C and then calcined in air at 500 ° C for 4 hours. The catalyst obtained contained 78% by weight of H-ZSM-5, the remainder being SiO 2 formed from the binder.

The catalyst thus prepared was used in the Example and Comparative Example described below.

Example:

 Loading with active metals and subsequent passivation

Loading with active metals:

Solution 1:

 35.62 g Ammoniumheptamolybdat tetrahydrate were placed in a beaker and dissolved in a total of 300 ml of deionized water.

Solution 2:

16.00 g of nickel (II) nitrate hexahydrate were placed in a beaker and dissolved in a total of 300 ml of deionized water.

300 g of the spray-dried catalyst prepared above were impregnated with solution 1 until all the solution was taken up by the catalyst; the impregnated catalyst was dried at 120 ° C for 16 h.

 Subsequently, the catalyst was also soaked with solution 2 until the whole solution was taken up; the impregnated catalyst was again dried at 120 ° C. for 16 h) and then calcined (at 3 ° C. to 500 ° C. and after reaching 500 ° C. for 4 hours).

The catalyst thus treated contained 6.0% molybdenum and 1% nickel. passivation:

 200g of this catalyst was charged to a fluidized bed reactor.

30 standard liters / h of N 2 were passed at room temperature (about 20 ° C) over a filled with hexamethylsilazane template and so saturated with hexamethylsilazane.

The resulting gas mixture was introduced into the heated to about 100 ° C fluidized bed reactor; the gas flow formed a stable fluidized bed.

 After one hour, the treatment of the fluidized bed with the gas flow was stopped and removed the catalyst from the reactor. The catalyst treated in this way was again dried at 120 ° C. for 16 hours and calcined (at 3 ° C. to 500 ° C. and after reaching 500 ° C. for 4 hours).

Comparative Example:

 Passivation and subsequent loading with active metals

passivation:

 200 g of the above-prepared, spray-dried catalyst were passivated as described in the example with hexamethylsilazane in a fluidized bed reactor, then dried and calcined.

Loading with active metals:

Solution 1:

 17.81 g Ammoniumheptamolybdat tetrahydrate were placed in a beaker and dissolved in a total of 150 ml of deionized water.

Solution 2:

 8.0 g of nickel (II) nitrate hexahydrate were placed in a beaker and dissolved in a total of 150 ml of deionized water.

 150 g of the catalyst already passivated with hexamethylsilazane were impregnated with solution 1 until all the solution had been taken up by the catalyst; the impregnated catalyst was dried at 120 ° C for 16 h.

 Subsequently, the catalyst was also soaked with solution 2 until the whole solution was taken up; the impregnated catalyst was again dried at 120 ° C. for 16 h) and then calcined (3 hours at 500 ° C. and 4 hours at 500 ° C.).

The catalyst thus treated contained 5.9% molybdenum and 0.95% nickel.

Non-oxidative dehydroaromatization of methane

The experiments were carried out with 100 g of the catalyst from the example and alternatively from the comparative example in a fluidized bed reactor. Initially, a methane stream was passed through the reactor at a flow rate of 100 standard liters (NL) / h, during which the temperature was slowly increased to the reaction temperature (700 ° C.) (during which the catalyst is activated, the Mo oxide that is contained is converted to molybdenum) carbidisiert). The flow rate was calculated for normal pressure and normal temperature.

The reaction was then carried out with a mixture of CH4 / He (90:10) at a flux of 20 NL / h. The temperature in the reactor was 700 ° C and the pressure 2.5 bar. One reaction cycle lasted 10 h. After each reaction cycle, the catalysts were regenerated by introducing hydrogen at 4 bar and 750 ° C for 5 hours (regeneration cycle).

Each series included approximately 10 reaction cycles and 10 regeneration cycles.

For each reaction cycle, after a start-up time of a few hours, a constant conversion was achieved and the following values were determined by taking samples:

Total conversion of methane to carbon compounds in wt.%

 the proportion of benzene in the carbon compounds formed in wt.% The proportion of coke in the resulting carbon compounds in wt.%

The values were identical for all reaction cycles of a test series and are summarized in the following table:

Series of experiments with catalyst series of experiments with catalase from the example tor of the comparative example

 % By weight of converted methane 7.5 7.5

 Proportion of benzene 85% 85%

 Proportion of coke <5 <5

Claims

Patent claims Process for producing a catalyst for dehydroaromatization, characterized in that a) a catalyst which contains a zeolite and at least one catalytically active metal, b) is passivated with a silicon-containing compound and c) then optionally calcined. Method according to claim 1, characterized in that it is a zeolite of the MFI structure type. 3. Method according to claim 1 or 2, characterized in that the zeolite is ZSM-5. 4. Process according to one of claims 1 to 3, characterized in that the catalyst additionally contains a binder. 5. The method according to any one of claims 1 to 4, characterized in that the catalyst contains one or more active metals selected from Mo, Mn, Cr, Zr, V, Zn, Cu, Ni, Fe, W, Ga, Ge and Co . 6. The method according to any one of claims 1 to 5, characterized in that the catalyst obtained contains 1 to 20% by weight of active metals and more than 80% by weight of the active metals were introduced into the catalyst before passivation. 7. The method according to any one of claims 1 to 5, characterized in that the silicon-containing compound is silanes, siloxanes or silazanes. 8. The method according to any one of claims 1 to 7, characterized in that the silicon-containing compound is a hexaalkylsilazane. 9. The method according to any one of claims 1 to 8, characterized in that the silicon-containing compound is applied by impregnation. 10. The method according to any one of claims 1 to 9, characterized in that the silicon-containing compound is applied to the catalyst in a fluidized bed. 1 1. The method according to any one of claims 1 to 10, characterized in that the catalyst obtained contains 0.001 to 5% by weight of Si of the silicon-containing compound or the reaction product obtained therefrom after a final calcination. Use of the catalyst obtained according to one of claims 1 to 1 1 as a catalyst for the dehydroaromatization of alkanes, alkenes or mixtures thereof. Process for the production of benzene from methane or mixtures which consist of more than 70% by weight of methane, characterized in that the catalyst is produced according to a process of claims 1 to 1 1 and then used for the production of benzene from methane or Mixtures of aliphatics containing more than 70% by weight of methane is used.