EP2473463A2

EP2473463A2 - Process for producing benzene from methane

Info

Publication number: EP2473463A2
Application number: EP10747846A
Authority: EP
Inventors: Christian Schneider; Martin Karches; Joana Coelho Tsou; Sebastian Ahrens; Dieter Stützer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2009-09-03
Filing date: 2010-08-23
Publication date: 2012-07-11
Also published as: WO2011026744A3; EA201270321A1; EA024439B1; WO2011026744A2; US8796496B2; KR20120082889A; US20120165585A1; JP5535319B2; JP2013503828A; CN102596861B; CN102596861A

Abstract

The present invention relates to a process for the non-oxidative dehydroaromatization of a feed stream containing C1-C4 aliphatics comprising the steps I, feeding the feed stream E into a reaction zone 1, reacting the feed stream E under non-oxidative conditions in the presence of a particulate catalyst to give a product stream P containing aromatic hydrocarbons, and removing the product stream P from the reaction zone 1; II, transferring the catalyst that is reduced in its activity by deposited coke into a reaction zone 2; III, at least partial regeneration of the catalyst with feed of a hydrogen-containing gas stream H in a reaction zone 2, wherein at least some of the deposited coke is converted into methane and a methane-containing gas stream M is formed that is fed at least in part to the reaction zone 1; IV, removing the catalyst from the reaction zone 2 and V, recirculating at least some of the catalyst that is removed to the reaction zone 1, wherein reaction zone 1 and reaction zone 2 are arranged spatially adjacently in the same reactor.

Description

Process for the preparation of benzene from methane Description

The present invention relates to a process for the non-oxidative dehydroaromatization of a CrC ₄ -Aliphaten-containing reactant stream by reacting the E- duktstrom in the presence of a catalyst in a reaction zone 1 to a aromatic hydrocarbon-containing product stream P and regeneration of coke deposited by its activity reduced catalyst with a hydrogen-containing mixture H in a reaction zone 2, removal of the catalyst from the reaction zone 2 and recycling of the catalyst in reactor zone 1.

Aromatic hydrocarbons such as benzene, toluene, ethylbenzene, styrene, xylene and naphthalene are important intermediates in the chemical industry, and their demand is still increasing. As a rule, they are obtained by catalytic reforming from naphtha, which in turn is obtained from petroleum. Recent research shows that world oil reserves are more limited compared to natural gas reserves. Therefore, the production of aromatic hydrocarbons from educts that can be obtained from natural gas is now an economically interesting alternative. The main component of natural gas is usually methane.

A possible reaction route for the production of aromatics from aliphatics is the non-oxidative dehydroaromatization (DHAM). The reaction takes place here under non-oxidative conditions, in particular with the exclusion of oxygen. In the case of DHAM, dehydrogenation and cyclization of the aliphatic compounds to the corresponding aromatics takes place, releasing hydrogen. A major problem for the industrial use of dehydroaromatization under non-oxidative conditions is the coking because it reduces the activity of the catalyst in a relatively short time, resulting in short production cycles and a high regeneration requirement. Frequently, the coking is accompanied by a shortened life of the catalyst. The regeneration of the catalysts is not without problems, since for an economic process on the one hand regularly the output activities must be restored and on the other this must be possible over a large number of cycles.

The coke deposits also have an unfavorable effect on the material balance or the yield, since every molecule of starting material that is converted into coke is no longer available for the desired reaction to aromatics. The hitherto in the state of the tech- The coke selectivities achieved in most cases are more than 20%, based on the reacted aliphatics.

Another difficulty with the technical implementation of the DHAM is the introduction of the required heat of reaction. DHAM is an endothermic reaction that relies on external heat input. If the reaction is heated indirectly, large heat exchanger surfaces are required, which make the process complex in terms of apparatus and economy. In addition, unwanted side reactions take place on the heat exchanger surfaces due to the higher temperatures, for example coking.

WO-A 03/000826 describes a process for the aromatization of methane, in which the methane is reacted in a reaction zone in the presence of an active catalyst, wherein the catalyst is deactivated. A portion of the deactivated catalyst is regenerated in a regeneration zone with a regeneration gas, with the catalyst circulating between the reaction zone and the regeneration zone. As regeneration gases oxygen or air, hydrogen and water vapor can be used. The gases produced during regeneration are no longer used. The heat generated during the regeneration is transferred by the catalyst itself or other heat exchange media into the reaction zone.

US-A 2007/0249879 relates to a process for the conversion of methane into higher hydrocarbons including aromatics. The reactor used consists of at least two series-connected reaction zones. The particulate catalyst is passed from the first to the second reaction zone, the methane-containing stream in the reverse direction from the second to the first reaction zone. In all reaction zones, a conversion of methane to product takes place. Parts of the catalyst can be removed for regeneration and recycled after regeneration. The regeneration takes place by means of an oxygen-containing gas. The catalyst is optionally subsequently activated with a hydrogen-containing gas. To introduce heat into the reaction system, a portion of the catalyst may be withdrawn and heated in a separate heating zone with combustion gases derived from an additional source of fuel. The heated catalyst is then returned to the reaction zone.

US-A 2007/0249880 discloses a process for reacting methane to aromatic hydrocarbons in the presence of a catalyst, wherein the reaction zone is operated with an inverse temperature profile. Again, the catalyst can be regenerated after removal or at temperatures above the Reacti- be heated onstemperatur by means of combustion gases and then recycled in each case in the reaction zones.

In the processes known from the prior art, the catalyst particles are exposed to strong mechanical stresses as a result of the many transport processes required between reaction zone, regeneration zone and heating zone, which lead to a shortening of the service life of the catalysts. Furthermore, the recycling, i. a conversion into the desired product of the resulting in the regeneration of the catalyst exhaust gases in the case of oxidative regeneration not at all or connected with regeneration with hydrogen with a certain technical effort.

In addition to the processes known in the prior art, there is a need for further, improved processes for the preparation of aromatics from CrC ₄ -aliphatic compounds which have a high yield of aromatic hydrocarbons with respect to the CrC ₄ -aliphatic used and in which the catalyst has lower mechanical properties Is exposed to stress.

This object is achieved by a method for the non-oxidative dehydroaromatization of a CrC ₄ -Aliphaten-containing reactant stream E, comprising the steps

I. feeding the feed stream E into a reaction zone 1, reacting the stream E under non-oxidative conditions in the presence of a particulate catalyst to an aromatic hydrocarbon-containing

Product stream P and carrying out the product stream P from the reaction zone 1,

II. Conversion of the deposited by coke in its activity reduced catalyst in a reaction zone 2,

III. at least partially regenerating the catalyst with the supply of a hydrogen-containing gas stream H in a reaction zone 2, wherein at least part of the deposited coke is converted into methane and a methane-containing gas stream M is formed, which is at least partially fed to the reaction zone 1,

IV. Carrying out at least a portion of the catalyst from the reaction zone 2 and V. returning at least a portion of the catalyst carried out in the reaction zone 1, wherein reaction zone 1 and reaction zone 2 are arranged spatially adjacent to each other in the same reactor. Regeneration of the deactivated catalyst with hydrogen produces methane from the coke deposits in an exothermic reaction. This is according to the invention at least partially fed to the reaction zone 1 and is thus available again as starting material. This leads to an increase in the total yield of aromatics based on the amount of CrC ₄ -Aliphaten used.

Due to the spatially adjacent arrangement of the reaction zone 1, in which the DHAM is carried out, and the regeneration zone (reaction zone 2), transport paths are saved and the mechanical stress is reduced by the transport for the catalyst particles. The heat generated in the regeneration of the catalyst is transferred directly by the recycling of at least a portion of the catalyst and the gas stream M in the reaction zone 1. As a result, a portion of the heat of reaction required for the aromatization is generated in the system itself, which is a technically particularly easy way to supply energy. Overall, the inventive zoning of the reactor or reaction bed in at least one aromatization zone (reaction zone 1) and adjoining a regeneration zone (reaction zone 2) allows better utilization of the material and heat flows at lower mechanical stress of the catalyst used. Non-oxidative according to the present invention means with respect to the DHAM, that the concentration of oxidizing agents such as oxygen or nitrogen oxides in the reactant stream E below 5 wt .-%, preferably below 1 wt .-%, more preferably below 0.1 % By weight. Most preferably, the mixture is free of oxygen. Also particularly preferred is a concentration of oxidizing agents in the mixture E which is equal to or less than the concentration of oxidizing agents in the source from which the CrC ₄ aliphates originate.

In terms of regeneration, non-oxidative in the context of the present invention means that the coke deposits originating from the DHAM on the catalyst for its regeneration are not converted into CO and / or CO ₂ by means of oxidizing agents such as air or oxygen. In particular, the concentration of oxidizing agents in the mixture H to be used for the regeneration in step III is below 5% by weight, preferably below 1% by weight, particularly preferably below 0.1% by weight.

According to the invention, the reactant stream E contains at least one aliphatic having 1 to 4 carbon atoms. These aliphatics include, for example, methane, ethane, propane, n-butane, i-butane, ethene, propene, 1- and 2-butene, isobutene. In one embodiment of the invention, the reactant stream E comprises at least 50 mol%, preferably at least 60 mol%, particularly preferably at least 70 mol%, even more preferably at least 80 mol%, in particular at least 90 mol%, of C 1 -C ₄ -aliphatics. Among the aliphatics, the saturated alkanes are particularly preferably used. Educt stream E then preferably contains at least 50 mol%, preferably at least 60 mol%, particularly preferably at least 70 mol%, even more preferably at least 80 mol%, in particular at least 90 mol% of alkanes having 1 to 4 carbon atoms.

Among the alkanes, methane and ethane are preferred, especially methane. According to this embodiment of the present invention, the reactant stream E preferably contains at least 50 mol%, preferably at least 60 mol%, particularly preferably at least 70 mol%, very preferably at least 80 mol%, in particular at least 90 mol%, of methane.

Preference is given to using natural gas as source of the CrC ₄ -aliphatic. The typical composition of natural gas is as follows: 75 to 99 mol% methane, 0.01 to 15 mol% ethane, 0.01 to 10 mol% propane, up to 6 mol% butane, up to 30 mol% % Carbon dioxide, up to 30 mol% hydrogen sulphide, up to 15 mol% nitrogen and up to 5 mol% helium. The natural gas can be purified and enriched prior to use in the process according to the invention by methods known to those skilled in the art. Purification includes, for example, the removal of any hydrogen sulfide or carbon dioxide present in the natural gas and further compounds which are undesirable in the subsequent process.

The Ci-C ₄ -aliphatates contained in the reactant stream E can also originate from other sources, for example, be incurred in petroleum refining. The CrC ₄ aliphatics may also have been produced regeneratively (eg biogas) or synthetically (eg Fischer-Tropsch synthesis).

If biogas is used as the CrC ₄ -aliphatic source, the feedstock stream E may additionally contain ammonia, traces of lower alcohols and further admixtures typical of biogas.

In a further embodiment of the process according to the invention, it is possible to use LPG (liquid petroleum gas) as feed stream E. According to a further embodiment of the process according to the invention, it is possible to use LNG (Liquefied Natural Gas) as starting material stream E.

In addition, hydrogen, steam, carbon monoxide, carbon dioxide, nitrogen and one or more noble gases can be admixed with the reactant stream E. The educt stream E preferably contains hydrogen, preferably 0.1 to 10% by volume of hydrogen, particularly preferably 0.1 to 5% by volume of hydrogen. In step I of the process according to the invention, the reactant stream E is fed to a reaction zone 1. In the reaction zone 1, the reaction of the reactant stream E takes place under non-oxidative conditions in the presence of a particulate catalyst to a product stream P containing aromatic hydrocarbons. This reaction is a dehydroaromatization, ie the CrC ₄ -aliphatic compounds contained in the reactant stream E react under dehydrogenation and cyclization to give the corresponding aromatics, hydrogen being liberated. According to the invention, the DHAM is carried out in the presence of suitable catalysts. In general, all catalysts which catalyze the DHAM can be used in step I of the process according to the invention. Those skilled in such catalysts as well as methods for their preparation are known. Typically, the DHAM catalysts contain a porous support and at least one metal deposited thereon. As the carrier, a crystalline or amorphous inorganic compound is usually used.

According to the invention, the catalyst preferably contains at least one metallosilicate as carrier. It is preferred to use aluminum silicates as the carrier. Very particularly preferred zeolites are used according to the invention as the carrier. According to the invention, the zeolite contained in the catalysts has a structure which is selected from the structure types pentasil and MWW and is particularly preferably selected from the structure types MFI, MEL, mixed structures of MFI and MEL and MWW. Very particular preference is given to using a zeolite of the ZSM-5 or MCM-22 type. The designations of the structure types of the zeolites correspond to the statements in WM Meier, DH Olson and Ch. Baerlocher, "Atlas of Zeolite Structure Types", Elsevier, 3rd edition, Amsterdam 2001. The synthesis of the zeolites is known to the person skilled in the art and can, for example starting from alkali aluminate, alkali metal silicate and α-morphological Si0 ₂ under hydrothermal conditions, whereby the type of channel systems formed in the zeolite can be controlled by means of organic template molecules, temperature and other experimental parameters.

The zeolites may contain other elements such as Ga, B, Fe or In besides AI.

Usually, the DHAM catalyst contains at least one metal. Usually, the metal is selected from Groups 3 to 12 of the Periodic Table of the Elements (IUPAC). According to the invention, the DHAM catalyst preferably contains at least one element selected from the transition metals of the main groups 6 to 11. The DHAM catalyst particularly preferably contains Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au. In particular, the DHAM catalyst contains at least one element selected from Mo, W, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu. Most preferably, the DHAM catalyst contains at least one element selected from Mo, W and Re. Also preferably according to the invention the DHAM catalyst contains at least one metal as active component and at least one further metal as doping. The active component is selected according to the invention from Mo, W, Re, Ru, Os, Rh, Ir, Pd, Pt. The doping is selected according to the invention from the group Cr, Mn, Fe, Co, Ni, Cu, V, Zn, Zr and Ga, preferably from the group Fe, Co, Ni, Cu. According to the invention, the DHAM catalyst may contain more than one metal as active component and more than one metal as doping. These are each selected from the metals specified for the active component and the doping.

According to the invention, the at least one metal is applied wet-chemically or dry-chemically to the carrier by the methods known to those skilled in the art.

According to the invention, the catalyst contains 0.1 to 20 wt .-%, preferably 0.2 to 15 wt .-%, particularly preferably 0.5 to 10 wt .-%, each based on the total weight of the catalyst of the at least one metal.

According to the invention, the catalyst may contain at least one metal from the group of the active component in combination with at least one metal selected from the group of the doping. In this case, the concentration of the active component is 0.1 to 20 wt .-%, preferably 0.2 to 15 wt .-%, particularly preferably 0.5 to 10 wt .-%, each based on the total weight of the catalyst ,

The doping in this case in the catalyst according to the invention in a concentration of at least 0.1 wt .-%, preferably at least 0.2 wt .-%, most preferably at least 0.5 wt .-%, based on the total weight of the catalyst.

According to another preferred embodiment of the present invention, the catalyst is mixed with a binder. Suitable binders are the customary binders known to the person skilled in the art, such as aluminum oxide and / or Si-containing binders. Particularly preferred are Si-containing binders; In particular, tetraalkoxysilanes, polysiloxanes and colloidal Si0 ₂ sols are suitable. If the catalyst according to the invention contains a binder, this is present in a concentration of from 5 to 80% by weight, based on the total weight of the catalyst, preferably from 10 to 50% by weight, particularly preferably from 10 to 30% by weight. ,

According to the invention, after the addition of the binder, a shaping step is carried out, in which the catalyst composition is processed into shaped bodies according to the processes known to the person skilled in the art. Forming procedures include, for example, spray a suspension containing the carrier or the catalyst mass, spray drying, tabletting, pressing in the wet or dry state and to name 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.

Pore formers and / or pasting agents are preferably removed after deformation from the resulting shaped body by at least one suitable drying and / or calcination step. The conditions required for this can be selected analogously to the parameters described above for calcination and are known to the person skilled in the art.

The geometry of the catalysts obtainable according to the invention can be, for example, spherical (hollow or full), cylindrical (hollow or full), ring, saddle, star, honeycomb or tablet shape. Furthermore, extrudates are for example in strand, Trilob, Quatrolob, star or hollow cylindrical shape in question. Furthermore, the catalyst mass to be molded can be extruded, calcined and the extrudates thus obtained broken and processed into a split or powder. The split can be separated into different sieve fractions. According to a preferred embodiment of the invention, the catalyst is used as spray-dried particles, preferably spray powder. These are preferably round particles. The catalyst particles preferably have a size of 20 to 100 microns.

Preferably, catalyst geometries are used, as they are known from the FCC method (filling catalytic cracking).

It may be advantageous to activate the catalyst used for the dehydroaromatization of CrC ₄ -aliphates before the actual reaction. This activation can be carried out with a C 1 -C ₄ alkane, such as, for example, ethane, propane, butane or a mixture thereof, preferably butane. The activation is carried out at a temperature of 250 to 850 ° C, preferably at 350 to 650 ° C, and a pressure of 0.5 to 5 bar, preferably at 0.5 to 2 bar performed. The GHSV (Gas Hourly Space Velocity) is usually ^{1 "} , preferably 500 to 2,000 hours ^{" 1} at 100 to 4,000 hours.

However, it is also possible to carry out an activation in that the feedstock stream E contains the CrC ₄ -alkane, or a mixture thereof, per se, or the CrC ₄ -alkane, or a mixture thereof, is added to the educt stream E. The activation is carried out at a temperature of 250 to 650 ° C, preferably at 350 to 550 ° C, and a pressure of 0.5 to 5 bar, preferably at 0.5 to 2 bar performed. In a further embodiment, it is also possible to add hydrogen in addition to the C ₁ -C 4 alkane. According to a preferred embodiment of the present invention, the catalyst is activated with a H ₂ -containing gas stream which may additionally contain inert gases such as N ₂ , He, Ne and Ar.

According to the invention, the dehydroaromatization of CrC ₄ -Aliphaten in the presence of a catalyst at temperatures of 400 to 1000 ° C, preferably from 500 to 900 ° C, more preferably from 600 to 800 ° C, in particular from 700 to 800 ° C, at a pressure from 0.5 to 100 bar, preferably at 1 to 30 bar, more preferably at 1 to 10 bar, in particular 1 to 5 bar carried out. According to the present invention, the reaction is carried out at a GHSV (gas hourly space velocity, volume flow starting material / volume of the catalyst bed) of from 10 to 10 000 h ^-1 , preferably from 20 to 3000 h ^-1 .

The CrC ₄ -Aliphaten be implemented in step I according to the invention with the release of H ₂ to aromatics. The product stream P therefore contains at least one aromatic hydrocarbon selected from the group of benzene, toluene, ethylbenzene, styrene, xylene and naphthalene. Most preferably, it contains benzene and toluene. Furthermore, the product stream containing unreacted CrC ₄ -Aliphaten hydrogen and the inert gases contained in the reactant stream E such as N ₂ , He, Ne, Ar, the reactant stream E added substances such as H ₂ and already present in E impurities.

According to the invention, the catalyst used for the DHAM in step I is regenerated regularly with the hydrogen contained in the gas stream H in step III. At least part of the deposited coke is converted into methane. The regeneration according to stage III in reaction zone 2 is at temperatures of 600 ° C to 1000 ° C and more preferably from 700 ° C to 900 ° C and pressures of 1 bar to 30 bar, preferably from 1 bar to 15 bar and more preferably from 1 to 10 bar performed. The result is a methane-containing gas stream M, which in addition to the resulting methane further formed in the regeneration compounds, unreacted hydrogen and already in mixture H contained substances.

According to a preferred embodiment of the present invention, the temperature of the catalyst is at the entrance to the reaction zone 1 above the temperature at the entrance to the reaction zone 2. Preferably, the inlet temperature in the reaction zone 1 is at least 50 ° C, preferably at least 75 ° C, more preferably min - at least 100 ° C above the inlet temperature in the reaction zone. 2 According to the invention, at least part of the methane produced in the regeneration is fed to the reaction zone 1. Particularly preferred are at least 50%, particularly preferably at least 80%, very particularly preferably at least 90% of the gas stream M and in particular the entire gas stream M from the reaction zone 2 is fed to the reaction zone 1. In a preferred embodiment of the invention, the amount of hydrogen fed to the reaction zone 2 and the geometric dimension of the reaction zone 2 are matched to the catalyst to be regenerated in such a way that the gas stream M entering the reaction zone 1 is at most 10% by volume. preferably contains no more than 5% by volume and very particularly no more hydrogen, ie that the supplied hydrogen was consumed as far as possible and preferably completely during the regeneration in step III. This has an unfavorable effect on the reaction equilibrium of the DHAM in the reaction zone 1.

According to the invention, the conversion of the catalyst in step II from the reaction zone 1 into the reaction zone 2 and the transfer of at least a portion of the gas stream M in step III from the reaction zone 2 into the reaction zone 1 directly, i. without diversion, in the area in which the two reaction zones are spatially adjacent. The mean flow direction of the gas stream M is according to the invention in opposite directions to the mean flow direction of the particulate catalyst.

According to a preferred embodiment of the present invention, the reaction zone 2 is arranged below the reaction zone 1. The reactant stream E is in this case preferably fed to the lower part of the reaction zone 1, more preferably to the lower third and very particularly preferably to the lowermost quarter of the reaction zone 1. The product stream P formed in the DHAM is carried out from the upper part of the reaction zone 1, preferably from the upper third and particularly preferably from the uppermost fourth of the reaction zone 1 from the reaction zone 1. The hydrogen-containing gas stream H is supplied in step III in the arrangement of the reaction zone 2 below the reaction zone 1 to the lower part, preferably the lower third and more preferably the lowest quarter of the reaction zone 2.

The catalyst which is optionally heated outside the reaction zone 2 is very particularly preferred when the reaction zone 2 is arranged below the reaction zone 1 in step V, preferably in the upper part of the reaction zone 1, preferably in the upper third and more preferably in the uppermost fourth of the reaction zone 1 the catalyst is returned from above into the reaction zone 1. In the dehydroaromatization of CrC ₄ -Aliphaten according to step I as well as in the regeneration of the deactivated by coke deposits catalyst with hydrogen according to step III, the catalysts may be present as a fluidized bed, moving bed or fluidized bed in the appropriate, suitable reactor types.

Preferably according to the present invention, the catalyst is present in the reaction zone 1, in the reaction zone 2 or in both reaction zones as a fluidized bed. Preferably, according to the present invention, the operating parameters, reactor design, and reactor dimensions are selected so that substantially no gas backmixing occurs between the reaction zone 1 and reaction zone 2 to prevent entry of CrC ₄ aliphates from reaction zone 1, if possible. Since methane is formed in the reductive regeneration of the catalyst, an entry of CrC ₄ -aliphatics, in particular of methane, has a negative effect on the reaction equilibrium of the regeneration.

The reaction zone 2 is particularly preferably operated as a fluidized bed, with essentially no internal mixing occurring. The internal mixing should be prevented as much as possible in order to avoid or at least reduce backmixing of the methane-containing gas stream M into the reaction zone 2 and thus to ensure as pure as possible a hydrogen atmosphere in the reaction zone 2. In particular, a methane-lean gas phase in the reaction zone 2 leads to a higher conversion of methane in the reaction zone 1, as shown in the example. In addition, a more uniform residence time profile of the catalyst particles to be regenerated is achieved by reducing the internal mixing.

The conditions for the operation of the catalyst bed with the lowest possible internal mixing are known in the art. Hints for the selection of parameters / operating conditions can be found, for example, in D. Kumii, O. Levenspiel "Fluidization Engineering" Second Edition, Boston, Chapter 9, pages 211 to 215 and Chapter 10, pages 237 to 243.

Another way to reduce the internal mixing in the reaction zone, the installation or the arrangement of devices that hinder the internal mixing. These devices may be, for example, perforated plates, structured packings, baffles and other internals known to the person skilled in the art. According to a preferred embodiment, at least one such device is arranged in the reaction zone 2. The extent of internal mixing can be determined, for example, from the vertical dispersion coefficients. Preferably, less than 10 mol% of Ci-C ₄ -aliphat, in particular methane, based on the stream H by backmixing of the reaction zone 1 in the reaction zone 2 registered. The transition region between reaction zone 1 and 2 is preferably at most 25%, more preferably at most 10%, and most preferably at most 5% of the length of the reaction zone 1. The length of the reaction zone 1 means the expansion of the reactor in the flow direction of the stream E. According to the invention, the reaction zone 1 is preferably separated from the reaction zone 2 by at least one device which is permeable to the reaction gases and the catalyst particles and which is arranged in the transition region between the reaction zones 1 and 2. These devices may be perforated plates, baffles, structured packings and further devices known to the person skilled in the art and suitable for this purpose, as described, for example, in the Handbook of Fluidization and Fluid Particle Systems, New York, 2003, Editor W. Yang. Chapter 7, pages 134 to 195 described. By these means, the backmixing of the catalyst particles and the reaction gases between these two zones can be influenced. In the context of the invention, reaction gases are the entirety of the gas streams involved in reaction zones 1 and 2, that is to say the gas streams E, H, P and M.

The reaction zone 1 is operated according to the invention preferably as a bubbling or turbulent fluidized bed, usually at Leerrohrgasgeschwindigkeiten of 10 to 80 cm / s.

Preferably, according to the invention, the catalyst, on the one hand, and the various gas streams E, H and M, on the other hand, are conducted in countercurrent flow. If the reaction zone 2 according to the preferred embodiment described above is arranged below the reaction zone 1, this means that the catalyst flows on average from top to bottom and the gas streams E, H, M and P have an average flow direction from bottom to top.

Three reactor forms which are particularly suitable for carrying out the process according to the invention are shown in FIG. The reactor shape (a) is cylindrical in the region of the reaction zone 1 and also in the region of the reaction zone 2, which is arranged below the reaction zone 1, likewise cylindrical in shape with the same diameter as in the region for the reaction zone 1. The reactor with the reactor shape (b) is cylindrical in the region of the reaction zone 1 and likewise cylindrical in the region for the reaction zone 2, but with a smaller diameter than in the region for the reaction zone 1, and has a conically shaped transition part. The reactor shape (c) also has a cylindrical shape formed region for the reaction zone 1 and is completely conically shaped in the region of the reaction zone 2 arranged below it. The route of the catalyst through the reactor is characterized by "K." According to the invention, more than one reaction zone 1 and more than one reaction zone 2 can be present, only at least one reaction zone 1 and at least one reaction zone 2 must be present, which each adjoin one another spatially.

According to the invention, the catalyst can be used undiluted or mixed with inert material. The inert material may be any material which is inert at the reaction conditions prevailing in the reaction zones, i. not reacted. As an inert material, the undoped catalyst used for the catalyst is particularly suitable, but also inert zeolites, alumina, silica, etc. The particle size of the inert material is in the range of the size of the catalyst particles. Preferably, the catalyst is used mixed with inert material. According to the invention, the inert material serves as a cost-effective heat transfer medium in order to introduce heat energy into the reaction zone 1. Particularly advantageous is the mixing of the catalyst with cheaper inert material when the reaction zone 2 is arranged below the reaction zone 1, since the height of the reactor or of the reactor bed is increased by mixing with inert material. This leads to a larger pressure drop along the fluidized bed. This raises at the lower end of the reactor bed, i. in the reaction zone 2, the highest pressure. A higher pressure has a positive effect on the regeneration. For regeneration of the deactivated by Koksablagerungen catalyst from step I according to the invention this is regularly regenerated in the reaction zone 2 with hydrogen. For this purpose, the catalyst is transferred from the reaction zone 1 into the reaction zone 2 and regenerated there by means of the hydrogen-containing gas stream H. The regenerated catalyst is then recycled back to the reaction zone 1.

The heat produced in the regeneration of the catalyst in step III in the reaction zone 2 is supplied to the reaction zone 1 to at least partially contribute to the energy required in step I for the DHAM. The heat is supplied by transferring at least part of the regenerated catalyst from the reaction zone 2 into the reaction zone 1. The regenerated catalyst serves as a heat carrier. At least one further part of the heat produced in the regeneration of the catalyst in step III in the reaction zone 2 is fed directly through the gas stream M to the reaction zone 1.

According to a further preferred embodiment of the present invention, the supply of a portion of that in the reaction zone 1 in step I of the present Indirectly required energy, for example, by a heat exchanger bundle in reaction zone. 1

According to a further preferred embodiment of the present invention, a portion of the energy required in reaction zone 1 in step I of the present process is supplied by at least a portion of the catalyst carried out with the optionally present inert material after step IV and before step V to a temperature above the Temperature is heated in the reaction zone 1. The method then according to the invention comprises the steps

Feeding the reactant stream E into a reaction zone 1, reacting the reactant stream E under non-oxidative conditions in the presence of a particulate catalyst to an aromatic hydrocarbon-containing product stream P and passing the product stream P out of the reaction zone 1, converting the coke deposited in its activity reduced catalyst in a reaction zone 2,

at least partially regenerating the catalyst by supplying a hydrogen-containing gas stream H in a reaction zone 2, wherein at least a portion of the deposited coke is converted to methane and a methane-containing gas stream M is formed which is at least partially supplied to the reaction zone 1,

Carrying out the catalyst from the reaction zone 2,

Heating at least a portion of the catalyst and

Recycling at least a portion of the heated catalyst to the reaction zone 1, with reaction zone 1 and reaction zone 2 spatially adjacent to one another in the same reactor. At least one part, preferably the entire catalyst carried out in step IVa, if appropriate with the added inert material, is heated outside the reaction zones 1 and 2 to a temperature of at least 50.degree. C., preferably at least 75.degree. C. and particularly preferably at least 100.degree is above the temperature in the reaction zone 1. At least a portion, preferably the entire heated catalyst is recycled to the reaction zone 1. The heating of the catalyst carried out can be direct or indirect. Preferably, the catalyst carried out is heated directly, for example by combustion gases are passed through the catalyst. In a preferred embodiment of the method according to the invention, an inert gas is heated, for example with combustion gases, which then heats the catalyst in direct contact. The heating of the catalyst Sators and optionally the inert material is preferably carried out in a so-called riser known to the expert.

In spite of the regeneration of the catalyst which normally takes place during each passage of the catalyst through the reaction zones 1 and 2, from time to time it may be expedient to regenerate the catalyst outside the reaction zone 2. For this purpose, the catalyst is reductively and / or oxidatively regenerated after the reaction from the reaction zone 2 in step V and before being recycled to reaction zone 1, and optionally activated. This additional regeneration step is carried out at most after each second pass, preferably at most after every tenth and particularly preferably at most after every 50th pass of the catalyst. Reductive regeneration means that the regeneration takes place in a reductive atmosphere, especially in a hydrogen atmosphere. The oxidative regeneration is carried out under oxidizing conditions, ie in the presence of oxidizing agents, in particular in the presence of an oxygen-containing gas such as air. In oxidative regeneration, the carbon deposited on the catalyst is converted to CO and C0 ₂ . The oxidative regeneration is usually followed by a reactivation step, as described above for the activation of the freshly prepared catalyst.

Examples

Influence of the methane content in the hydrogen used for catalyst generation

example 1

In a fixed bed in each case two reaction cycles of the aromatization of methane with a duration of 10 h at 700 ° C and ambient pressure were driven. Between the two reaction cycles, the catalyst was regenerated for 5 h at 750 ° C bar (abs). a) regeneration with pure hydrogen

b) regeneration with a mixture of 90 vol .-% hydrogen and 10 vol .-% methane

The methane conversions (based on the methane used in the reaction cycles) are lower when regenerated with the methane and hydrogen-containing gas stream, as shown in Table 1. Table 1

Backmixing the methane towards the regeneration zone (reaction zone) will negatively impact regeneration efficiency.

Claims

claims

1 . A process for the non-oxidative dehydroaromatization of a precursor stream E containing CrC ₄ -aliphates comprising the steps

I. feeding the feed stream E into a reaction zone 1, reacting the stream E under non-oxidative conditions in the presence of a particulate catalyst to a product stream P containing aromatic hydrocarbons and carrying out the product stream P from the reaction zone 1,

III. at least partially regenerating the catalyst by supplying a hydrogen-containing gas stream H in a reaction zone 2, wherein at least a portion of the deposited coke is converted to methane and a methane-containing gas stream M is formed which is at least partially supplied to the reaction zone 1,

IV. Running the catalyst from the reaction zone 2 and

V. returning at least a portion of the catalyst carried out in the

Reaction zone 1, wherein reaction zone 1 and reaction zone 2 are arranged spatially adjacent to each other in the same reactor.

2. The method according to claim 1, characterized in that after step IV and before step V at least a portion of the catalyst carried out is heated.

3. The method according to claim 1 or 2, characterized in that between the reaction zone 1 and the reaction zone 2 substantially no gas back-mixing occurs.

4. The method according to any one of claims 1 to 3, characterized in that the reaction zone 1 is separated from the reaction zone 2 by at least one device permeable to the catalyst particles and reaction gases, arranged in the transition region from reaction zone 1 to reaction zone 2 device.

5. The method according to any one of claims 1 to 4, characterized in that the reaction zone 2 is operated as a fluidized bed, wherein substantially no internal mixing occurs.

Method according to one of claims 1 to 5, characterized in that in the reaction zone 2 at least one device is arranged, which impedes the internal mixing of the catalyst particles when operating in the fluidized bed.

Method according to one of claims 1 to 6, characterized in that the reaction zone 1 is operated as a fluidized bed with internal mixing.

Method according to one of claims 1 to 7, characterized in that the gas stream M when entering the reaction zone 1 contains at most 10 vol .-% hydrogen.

9. The method according to any one of claims 1 to 8, characterized in that the reaction zone 2 is arranged below the reaction zone 1.

10. The method according to claim 9, characterized in that the catalyst is fed in step V to the upper part of the reaction zone 1.

1 1. A method according to claim 9 or 10, characterized in that in step III, the gas stream H is supplied to the lower part of the reaction zone 2.

12. The method according to any one of claims 9 to 1 1, characterized in that the reactant stream E is supplied to the lower part of the reaction zone 1 in step I.

13. The method according to any one of claims 1 to 12, characterized in that the method is carried out in a reactor which is cylindrical in the region of the reaction zone 1 and in the region of the reaction zone 2, which is arranged below the reaction zone 1, cylindrical with the same Diameter as in the reaction zone 1 (reactor shape (a)), cylindrical with a smaller diameter and conically shaped transition part (reactor shape (b)) or completely conically shaped (reactor shape (c)) is formed.

14. The method according to any one of claims 1 to 13, characterized in that the catalyst is used mixed with inert material.

15. The method according to any one of claims 1 to 14, characterized in that the catalyst is regenerated after removal in step IV and before the return in step V oxidative and / or reductive and possibly reactivated, this being at most after every second pass of Catalyst through the two reaction zones 1 and 2 is performed.