JPH10503419A - Hydrocarbon shape-selective conversion - Google Patents

Abstract

  (57) [Summary] A method comprising contacting a catalytic molecular sieve, which has been given a selectivity in advance by coagulation with an organic silicon compound by a shape-selective hydrocarbon conversion method such as toluene disproportionation, to a reaction stream under conversion conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION                         Hydrocarbon shape-selective conversion   The present invention relates to the shape-selective conversion of hydrocarbons, such as the selective conversion of aromatic para-substituted compounds. It relates to the production and the like, and in particular, selective disproportionation of toluene. rtionation).   The term shape-selective catalysis refers to unexpected catalyst selection in zeolites. It represents sex. For the principle of shape-selective catalysis, see, for example, N.Y. Che n, W.E. Garwood and F.G. `` Shape Selective Catalysis in Indust by Dwyer rial Applications, Shape Selective Catalysis in Industrial Applications, Volume 36, Marcel Dekker, Inc. (1989). In the zeolite pores For example, paraffin isomerization, olefin skeleton or double bond isomerization, oligomerization And disproportionation, alkylation or transalkylation reactions of aromatic hydrocarbons The hydrogen conversion reaction is governed by constraints on the channel size of the zeolite. Offering If the feed fraction is too large to enter the zeolite pores and react, Selectivity occurs. On the other hand, some of the products leave the zeolite channel If not, product selectivity occurs. The product distribution depends on the reaction transition state. Some reactions do not occur because they are too large to form in olilite pores or cages It can also be changed by the transition state selectivity. Another type of selectivity Is due to configurational diffusion, in which case the size of the molecule is Approach the size of the system. Small changes in molecular or zeolite pore size are large A change in diffusion results in a different distribution of products. This kind of shape Selective catalysis is, for example, the selective disproportionation of toluene to obtain p-xylene Is shown in   Paraxylene is described in Chen et al., "J. Amer. Chem. Sec. 1979, 101, 6873". Can be produced by methylating toluene with methanol as described. And Pines' The Chemistry of Catalytic Hydrocarbon Conversi on (Chemistry of catalytic conversion of hydrocarbons), Academic Publishing / New York, 1981, It can also be produced by disproportionation of toluene, as described on page 72. Wear. In such a method, paraxylene, orthoxylene and metaxylene are mainly used. A mixture containing the components is produced. Depending on the para-selectivity of the catalyst and the reaction conditions, The paraxylene content varies. The yield, i.e. the amount actually converted to xylene The amount of feed is also affected by the catalyst and the reaction conditions.   By the conventionally known methylation reaction of toluene, as shown in the following general formula Numerous by-products are usually supplied.Thermodynamic equilibrium for converting toluene to specified products. Non-MTPX As one of the methods for increasing the para-selectivity of the zeolite catalyst, a “selectivity imparting agent ( se lectivating agent). Conversion of hydrocarbons In the process, various silicon compounds are used to modify the catalyst to improve selectivity. Used. For example, there is the hydrocarbon conversion method of the United States patent. US Patent 4,14 No. 5,315, 4,127,616 and 4,090,981 for processing zeolite Discloses the use of a silicone compound dissolved in an organic solvent. USA Patents 4,465,886 and 4,477,583 disclose the use of silicones for zeolite treatment. The use of aqueous emulsions is mentioned. U.S. Pat. No. 4,927,979 disclose the use of alkoxysilanes supported on gas or organic solvents. It describes the use for ollite processing. Further, U.S. Pat. Nos. 0,215 and 3,698,157 disclose the use of pyridine, ether, etc. for zeolite treatment. Describes the use of silanes dissolved in hydrocarbons. Such denaturing method It is known that the process is carried out after the aggregation of the zeolite.   Some of these catalyst modification methods are described, for example, in U.S. Pat.No. 4,477,583. And No. 4,127,616 show that para-selectivity of over 90% (para-xyl (Selectivity of len)), but the conversion of toluene is not acceptable in the market. As low as 10% possible, the end result is less than 9% para-xylene yield, 10% x 90%. Such methods require significant amounts of ortho-xylene and methanol. High cost due to the separation of para-xylene from other isomers as silene is also produced Is required.   Typical separation steps include expensive fractional crystallization steps and other xylene isomers Consists of adsorption and separation of para-xylene from Always recirculated. Equilibrium mixture containing recycled xylene isomers and para-xylene A xylene isomerizer is required for further conversion to.   Those skilled in the art understand that the cost of this separation step is proportional to the degree of separation required. ing. Therefore, while maintaining the conversion level acceptable in the market, By increasing the selectivity, significant cost savings can be achieved.   Therefore, while maintaining the conversion level of toluene that is accepted in the market, It is highly desirable to provide a highly selective method for producing para-xylene New Furthermore, efficient and economical methods for imparting selectivity to the catalysts used have been developed. It is highly desirable to supply.   That is, the present invention comprises a crystalline molecular sieve and an organosilicon compound. The mixture obtained is agglomerated, and the resulting agglomerate is calcined to impart selectivity in advance. Crystalline molecular with a constraint index of 1 to 12 The present invention provides a catalyst characterized by comprising a sieve.   The present invention also relates to the use of shape-selective hydrocarbon conversion, such as para-selective disproportionation of toluene. In a method, there is provided a mixture comprising a crystalline molecular sieve and an organosilicon compound. Agglomerated products, and baking the obtained agglomerated products to give a Hydrocarbon catalysts consisting of crystalline molecular sieves with a strain index of 1 to 12 Providing a method characterized by contacting with a feedstock .   The molecular sieve used in the method of the present invention includes a mesoporous zeolite. You. Constraint index of such mesoporous zeolite ) Is 1 to 12. U.S. Pat.No.4,016,218 Is described in detail. Specified value of constraint index of mesoporous zeolite Molecular sieves conforming to US Pat. No. 3,702,886, No. 29,949, 3,709,979, 3,832,449, 4,556,447, 4,076,842, 4,016, Nos. 245, 4,397,827, 4,650,655, 3,308,069, Reissue No. 28,341 and European Patent ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 described in No. 127,399 , ZSM-48, ZSM-50, MCM-22 and zeolite beta. These zeolites Manufactured by changing the ratio of silica and alumina within the range of 12: 1 or more Is done. Preferred molecular sieves include ZSM-5, ZSM-11, ZSM-12, and ZSM-3. Five And MCM-22. Particularly preferred is ZMS-5.   In the catalyst of the present invention, the ratio of silica and alumina is preferably less than 100, more preferably Preferably from 20 to 80, the alpha value is preferably greater than 100, for example from 150 2000. Alpha value is an index of catalytic cracking activity of a catalyst compared to a standard catalyst. Yes, relative rate constant (normal hexane conversion rate per unit time and unit catalyst volume) Degree). For the alpha value, set the alpha value to 1 (speed constant: 0.016 seconds)^-1) It is based on the activity of the amorphous silica-alumina decomposition catalyst. Alpha testing See U.S. Pat. No. 3,354,078 and "The Journal of Catalysis, Vol. 4, 522-52. 9 (August 1965), Volume 6 278 (1966) and Volume 61 395 (1980) " Have been   In the synthesis of zeolites, the reaction mixture generally contains oxides of silicon, Optionally, a template agent and an aluminum source, usually an organic nitrogen-containing compound. Manufactured with a lukari aqueous medium.   Silicon oxide can be obtained from known sources such as silicates, silica hydrosols, From precipitated silica hydrosols, eg precipitated silicas such as "Hi-Sil", silica gel, silica Can be supplied. Aluminum oxide can be found in other reactants, e.g., a silica source. Supplied purely only.   Of course, each zeolite product obtained by crystallization of the reaction mixture will have a different However, examples of organic nitrogen-containing cation sources include primary, secondary, or tertiary amines, And quaternary ammonium compounds. As quaternary ammonium compounds, tet Lamethylammonium, tetraethylammonium, tetrapropylammonium , Tetrabutylammonium, diethylammonium, triethylammonium Dibenzylammonium, dibenzyldimethylammonium, dibenzyldiamine Ethyl ammonium, benzyl trimethyl ammonium or chlorine salts But not limited to these. Examples of amines useful herein include trimethyl alcohol Min, triethylamine, tripropylamine, ethylenediamine, propanedi Amine, butanediamine, pentanediamine, hexanediamine, methylamine , Ethylamine, propylamine, butylamine, dimethylamine, diethyl Amine, dipropylamine, benzylamine, aniline, pyridine, piperidine And pyrrolidine, but are not limited thereto.   As the alkali metal or alkaline earth metal oxide source, for example, sodium hydroxide , Lithium hydroxide, calcium hydroxide, magnesium hydroxide, cesium hydroxide And potassium hydroxide, halides (eg chloride, bromide), sulfates, nitrates Acid salts, acetates, silicates, aluminate phosphates and carboxylate salts. After crystallization of the zeolite, removal of organic cations usually involves calcination or other known methods. Method is generally used to remove alkali metals or alkaline earth metals. Intermediate ion exchange and calcining ammonium to produce hydrogen Method is often used.   Zeolite crystals used in commercial processes improve strength and wear resistance after crystallization In order to do so, it is usually made into an aggregate. Various methods are available for agglomeration of zeolite crystals. A method is used. These methods include pelletization by extrusion or beads. , Spray-drying to form flowable microspheres, hot pressing of zeolite crystals And agglomeration by heat.   In the present invention, the silicon-modified zeolite molecular sieve is a zeolite The crystals are mixed with an organosilicon compound and optionally a binding material, and the resulting mixture is coagulated. And then calcining the agglomerates. Firing in an atmosphere containing oxygen At a temperature above 300 ° C. at a rate of 0.2 ° C./min to 5 ° C./min. By raising the temperature to a temperature below the temperature that adversely affects the crystallinity of zeolite. And successfully performed. Usually, the temperature is below 600 ° C. The firing temperature is preferably It ranges from about 350 ° C to 550 ° C. Aggregates are usually kept at the firing temperature for 1 to 24 hours. Retained You.   The zeolite crystals are added to the mixture as-synthesized, and after aggregation of the crystals, Organic template and alkali metal or alkaline earth metal remaining in the site structure May be removed from the crystallization reaction mixture by a known method. Organosilicon compounds are aqueous, for example, emulsions that can be stabilized with surfactants. As a solution or as an aerosol to the mixture. Useful surface activity Examples of the surfactant include polyoxyethylene-octylphenol ether. You.   As the organic silicon compound, for example, alkyl silane, aryl (aryl) sila Alkyaryl silanes, alkoxysilanes, aryls Oxysilane, oxyethylene silane, alkylaryloxysilane, siloxa Such as silanes such as olefins and alkyl, aryl and / or glycol groups. And siloxanes. Alkyl is intended to have 1 to 12 carbon atoms, Is intended to have 6 to 10 carbon atoms. Examples of organic silicon compounds The following silicone compounds are also included, which are also used to provide trim selectivity. You. Preferred are siloxanes such as phenylmethylpolysiloxane.   Molecular sieves suitable for the hydrocarbon shape-selective conversion method of the present invention are porous. Aggregate or support with a support or binder such as a porous inorganic oxide support or clay binder Is extruded. Silica is preferred as the binder, but other binder materials Examples of commonly used inorganic oxide gels or gelatinous precipitates Lumina, zirconia, magnesia, thoria, titania, boria or any of these But not limited to mixtures. It is suitable as a clay material These include bentonite and porous diatomaceous earth. Catalyst and binder The ratio of the crystalline molecular sieve to the total composition of the support is 30 to 90% by weight, Preferably it is 50-80% by weight of the composition. The composition can be extrudates, beads, pellets (Tablets) or fluid microspheres.Shape selective conversion   Molecular sieves that have been selectively agglomerated by the present invention are typically carbonized. Cracking reactions, including dewaxing of hydrogen feeds, isomerization of alkyl aromatics, Production of gasoline, distillate, lubricating oil or chemicals by ligomerization, generation of aromatic hydrocarbons Transalkylation, conversion of oxygenates to hydrocarbons, rearrangement of oxygenates, Shape-selective conversion of hydrocarbons, such as the conversion of light paraffins and olefins to aromatics It is useful as a catalyst in   Generally, the conditions for catalytic conversion of a catalyst composed of a modified zeolite are 100 to 760 ° C, Pressure 10 to 20,000 kPa (0.1 to 200 bar), weight per unit time Space velocity (weight hourly space velocity: WHSV) 0.08 hours^-1From 2000 hours^-1 The ratio of hydrogen to organic compounds such as hydrocarbon compounds is from 0 to 100 And the like.   The catalyst of the present invention is obtained by transalkylating or disproportionating toluene to para-xylene. Specifically intended for the production of The following is a typical example of the selective conversion.Disproportionation of toluene   Reaction conditions for toluene disproportionation considered herein include 350 ° C to 5 ° C. A temperature of 40 ° C., preferably exceeding 400 ° C., and a pressure of 100 kPa to 34,500 kPa (0 to 5000 kPa) psig) preferably 790 kPa to 7000 kPa (100 to 1000 psig), water for hydrocarbons Elemental molar ratio of 0.1 to 20, preferably 2 to 4, weight hourly space velocity (WHSV) is 0.1 hour^-1From 20 hours^-1Preferably 2 hours^-1From 4 hours^-1The conditions are Can be The feedstock of toluene preferably contains 50% to 100% toluene, but about 8%. Feedstocks containing 0% or more toluene are more preferred. Adversely affect the invention Unless otherwise, benzene, xylene, trimethylbenzene in toluene feed And other compounds may be present. Toluene feed enters the reaction zone It may be dried appropriately by a method that minimizes the amount of water. Torue charged during this process There are a number of known methods suitable for drying the skin, including suitable drying agents such as silica gel, Percolation with activated alumina, molecular sieves, other suitable substances, etc. Alternatively, use of a liquid filling dryer may be mentioned. Typically, alkyl groups are placed at all positions by single-pass conversion of the toluene stream. Dimethylbenzene, that is, ortho-xylene, meta-xylene, para-xylene And a product logistics containing In addition, these xylenes become unnecessary due to the following reactions: It is known to proceed to a reaction that produces ethylbenzene (EB).   Previously, if isomerization was allowed, all C in a single pass₈P-xylene for product A purity of less than 90% was acceptable. Due to the formation of ethylbenzene, this effect The rate decreases somewhat.   However, according to the present invention, the ortho isomer and meta High conversion rates were provided to reduce isomer formation. Product logistics obtained thereby Contains more than 90% pure para-xylene. For example, ortho-xylene isomer Can be reduced to about 0.5% or less of the total xylene content, and the meta-xylene isomer It can be reduced to less than about 5% of the silene content. Further, for example, molecular When treating the reaction system accurately, such as by depositing platinum on a sieve, C for the presence of tylbenzene₈It can be reduced to less than about 0.3% of the product.   As described in detail herein, the present invention provides for at least 90%, preferably at least 95%, Above, most preferably with about 99% or more para-xylene purity, %, Preferably at a conversion of about 20-25% or more.   Compared to previously disclosed methods, the method of the present invention is commercially acceptable. Higher paraxylene purity can be achieved at lower conversions. Therefore, unnecessary Costs previously required to separate by-products could be significantly reduced Become. In the prior art toluene disproportionation method, these costs are required to obtain these efficiencies. There is usually a need for bulky second and third processing steps. Preferably, the toluene disproportionation process of the present invention is preliminarily prepared outside the catalyst during catalyst agglomeration. Intra-catalyst selectivity step for zeolite catalysts in addition to providing selectivity Consists of Referred to herein as "trim selectivation" The imparted selectivity within the catalyst is determined to be the desired p-xylene selectivity, for example, 90% or 9%. Under reaction conditions, toluene, a selectivity-imparting agent, and hydrogen are used until a selectivity of 5% is obtained. At the same time with the catalyst. The supply of the agent is stopped. The trim selectivity enhancer is preferably a silicon-containing compound. And more preferably a silicone-containing compound represented by the following general formula. Where R₁Is hydrogen, fluorine, hydroxy, alkyl, aryl, alkyl aryl Or fluoroalkyl. Hydrocarbon substituents usually have 1 to 10 carbon atoms and are Preferable is a methyl or ethyl group. R_TwoIs R₁Selected from the same group as Represents the above integer, usually in the range of 3 to 100. Silicone compounds used The molecular weight of the product is usually in the range of 80 to 20,000, preferably in the range of 150 to 10,000. In the enclosure. Representative silicone compounds include dimethyl silicone and diethyl Silicone, phenylmethyl silicone, methyl hydrogen silicone, ethyl hydrogen Silicone, phenyl hydrogen silicone, methyl ethyl silicone, phenyl ethyl Silicone, diphenyl silicone, methyl trifluoropropyl silicone , Ethyl trifluoropropyl silicone, polydimethyl silicone, tetrac Lorophenylmethyl silicone, tetrachlorophenylethyl silicone, tet Lachlorophenyl hydrogen silicone, tetrachlorophenylphenyl silicone, Examples thereof include methyl vinyl silicone and ethyl vinyl silicone. silicone The compound need not be linear, for example, hexamethylcyclotrisiloxane, Kutamethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane and It may be cyclic such as octaphenylcyclotetrasiloxane. these Can be used in the same manner as the silicone having other functional groups. Wear. Other silicon-containing compounds such as silane, siloxane, etc. are also available .   P-xylene rim selectivity imparting agent and silicon added during zeolite agglomeration The dynamic diameter of the preselectivity-imparting compound is chosen to avoid reducing the internal activity of the catalyst. It is more preferable that the diameter is larger than the zeolite pore diameter.   The reaction conditions for the trim selectivity providing step are as follows: temperature 350 ° C to 540 ° C, pressure 100 34500 kPa (from atmospheric pressure to 5000 psig). The feed rate to the reaction system is about 0. Performed from 1 WHSV to 20 WHSV. The supply of hydrogen is based on the molar ratio of hydrogen to hydrocarbon. Is performed at about 0.1 to 20. The trim selectivity supply is preferably toluene 0.1% to 50% of the amount of tritium, and depending on the rate of Preferably lasts from 50 to 300 hours, most preferably less than 170 hours I do.   Although not wishing to be bound by theory, it is believed that the effects of the present invention increase catalyst bends. By making the acid sites on the outer surface of the catalyst substantially less accessible to the reactants It is thought that it can be obtained. Acid sites on the outer surface of the catalyst leave the catalyst pores Para-xylene isomerized back to an equilibrium level with the other two isomers, It is believed that this reduces the amount of para-xylene in xylene to about 24%. Catalytic By reducing the accessibility of these acid sites to para-xylene exiting the pores And a relatively high level of para-xylene is maintained. Para exiting the pores of the catalyst By reducing the accessibility of these acid sites to xylene, It is possible to maintain the ren at relatively high levels. Imparting the trim selectivity of the present invention The agent blocks these acid sites by chemically modifying them. Or otherwise keep it away from para-xylene.   To reduce the amount of unwanted by-products, especially ethylbenzene, additional catalyst Denature. In known techniques, the reactant effluent from a standard toluene disproportionation is Contains approximately 0.5% ethylbenzene by-product. When distilling the reaction product, C₈ The amount of ethylbenzene in the cut often increases to 3-4%. Polymer grade This amount of ethylbenzene is not acceptable for p-xylene. I mean , C₈If the product ethylbenzene is not removed, the final p-xylene product The reason for this is that the quality of the resulting fiber is deteriorated. In other words, ethylbenze Must be kept at a low level. C₈Regulation of ethylbenzene in products The rating is determined by the industry to be less than 0.3%. Ethylbenzene isomerized or extra Can be substantially removed by the distillation method. Zen removal is not practical in the present invention. Because the para more than 90% The xylene stream containing xylene is isomerized simultaneously into equilibrium xylene, This is because the amount of paraxylene in the silen stream is reduced to about 24%. Another super fractionation It is publicly acknowledged that the method of removing ethylbenzene by Is knowledge.   To avoid the need for downstream ethylbenzene removal, The catalyst has a hydrogenation-dehydrogenation function such as adding a metal compound such as platinum. Advantageously reduced by addition. The preferred metal is platinum, but Radium, nickel, copper, cobalt, molybdenum, rhodium, ruthenium, silver, Uses metals such as gold, mercury, osmium, iron, zinc, cadmium, and mixtures thereof it can. The metal is added by cation exchange, the amount of which is about 0.01-2%, About 0.5%. The metal enters the pores of the catalyst so that it remains in the next firing step. Must be able to For example, in the case of platinum-modified catalyst, The catalyst is converted to the ammonium form by addition to a solution of ammonium. Next obtained touch The medium is tetraamine platinum (II) nitrate or tetraamine platinum (II) chloride water Contact with solution. The resulting metal compound can advantageously enter the pores of the catalyst . Next, the catalyst is filtered, washed with water and calcined at a temperature of about 250 ° C to 500 ° C.   The effluent is separated and distilled to obtain the desired product, para-xylene and other by-products. Remove objects.   According to the process of the present invention, toluene is used to produce high levels of aromatic concentrates such as total C₈To the product In contrast, it is converted to about 99% para-xylene. In a representative method of the present invention, Suitable toluene conversions are from 90% to 99% para-xylene purity and from 20% to 25% by weight. %.   The following examples illustrate the invention, but do not limit the invention. Absent.                                   Example 1   1.01g of 50% sodium hydroxide solution in 15.57g of distilled water in 150cc capacity beaker And 2.20 g of dimethylsiloxane modified with oxyethylene groups to be water-soluble at 38 ° C Recon was added. To the solution was added 10.85 g of as-synthesized ZSM-5 and 5.85 g of non-hydrated The mixture of crystalline silica was added with stirring. Use a manual extruder to produce the dry paste And extruded to obtain a well-formed 1.6 mm (1/16 inch) extrudate. 2 at 120 ° C Drying for an hour yielded 12.91 g of product.                                   Example 2   To 15.58 g of distilled water in a 150 cc beaker, add 1.03 g of 50% sodium hydroxide solution And 4.06 g of phenylmethylpolysiloxane and 0.79 g of isooctylphenoxy A mixture of polyethoxyethanol surfactant was added to produce an emulsion. The emulsion 10.85 g of as-synthesized ZSM-5 and 5.85 g of hydrated amorphous silica (HiSil, PPG Ind ustries, Inc.) was added with stirring. Manual extrusion of the resulting dry paste The mixture was extruded using a machine to obtain a well-formed 1.6 mm (1/16 inch) extrudate. 120 Drying at 2 ° C. for 2 hours gave 13.49 g of product.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI C10G 35/095 9279-4H C10G 35/095 (72) Inventor Degunan, Thomas Francis, Jr. United States, 08057 New Jersey, Moorestown, Paddock Pass 736 (72) Inventor Lord Wald, Paul Garhard, Jr. 08553 New Jersey, Rocky Hill, Merritt Lane 4 (72) Inventor Shihabi, David Said United States, 08534 New Jersey, Pennington, Herberton Woodsville Road, R1, Box 334 A

Claims (1)

[Claims]   1. Agglomerate a mixture containing crystalline molecular sieves and organosilicon compounds And the resulting aggregates are fired to give a constrain A catalyst comprising a crystalline molecular sieve having an int index of 1 to 12.   2. Organic silicon compound is silicone, silane, alkoxysilane, siloxa 2. The catalyst according to claim 1, wherein the catalyst is selected from the group consisting of polysiloxanes and polysiloxanes.   3. The composition according to claim 1, further comprising a hydrogenation or dehydrogenation metal. Is the catalyst according to 2.   4. Crystalline molecular sieves with a constraint index of 1 to 12 Forming a mixture containing the recon compound in a weight ratio of 1:10 to 100: 1, To give selectivity to the catalyst molecular sieve in advance Law.   5. In addition, toluene and powder are added to the catalytic molecular sieve to which selectivity has been given in advance. The mixture containing the second silicon source, which is a xylene selectivity imparting agent, is Denatured twice with contact for at least one hour under the reaction conditions for conversion to 5. The process according to claim 4, wherein the catalyst is obtained.   6. Agglomerate a mixture containing crystalline molecular sieve and organosilicon compound And then calcining the obtained aggregates to give a constrain Catalysts comprising crystalline molecular sieves with an int index of 1 to 12 converted to hydrocarbons The method of shape-selective conversion of hydrocarbons in contact.   7. Shape-selective conversion of hydrocarbons is due to the selective disproportionation of toluene to para-xylene. The method of claim 5, wherein the method comprises:   8. Temperature 350 ° C to 540 ° C, Pressure 100 kPa to 34500 kPa (From atmospheric pressure to 5000 psig ), Disproportionation with WHSV of 0.1 to 20 and molar ratio of hydrogen to hydrocarbon of 0.1 to 20 7. The method of claim 6, wherein the method is performed.