PROCESS FOR CONVERTING DIMETHYL ETHER OR METHANOL TO HYDROCARBONS LOW IN AROMATIC COMPOUNDS, USING A PALLADIUM-LOADED ZEOLITE CATALYST

Abstract

The present invention provides a method which includes loading a zeolite catalyst in ammonium form with palladium ions, drying and calcining the palladium ion-laden zeolite catalyst to a proton form, fractionating the proton form of the palladium ion-laden zeolite catalyst into a powder, mixing the powder with an inert material, introducing the mixture into a fixed bed reactor, heating the fixed bed reactor to a reaction temperature and passing an inert gas therethrough, reducing the mixture in a hydrogen stream, passing an inert gas through the fixed bed reactor, introducing a reactant gas feed of hydrogen, an inert gas and dimethyl ether or methanol into the fixed bed reactor to form a product gas mixture, condensing the product gas mixture to a product phase liquid, and separating the product phase liquid into an aqueous and into an organic phase which includes the low-aromatics C.sub.5+ hydrocarbons.

Claims

1-16. (canceled)

17. A method for converting dimethyl ether (DME) or methanol into low-aromatics C.sub.5+ hydrocarbons via a catalytic reaction over a palladium-laden zeolite catalyst H-EU-2 in a hydrogen stream, the method comprising: A) loading a EU-2 zeolite catalyst in an ammonium form with palladium ions via a capillary impregnation to obtain a palladium ion-laden zeolite catalyst; B) drying and calcining the palladium ion-laden zeolite catalyst from step A) to form a proton form of the palladium ion-laden zeolite catalyst; C) fractionating the proton form of the palladium ion-laden zeolite catalyst from step B) into a powder having a particle size of 100 to 500 m; D) mixing the powder from step C) with an inert material to obtain a mixture; E) introducing the mixture from step D) into a fixed bed reactor; F) heating the fixed bed reactor from step E) to a reaction temperature of 350 to 450 C. and passing a flow of an inert gas through the fixed bed reactor; G) reducing the mixture containing the proton form of the palladium ion-laden zeolite catalyst in a hydrogen stream in the fixed bed reactor; H) passing a flow of an inert gas through the fixed bed reactor and establishing a reaction pressure of 1 to 50 bar; I) introducing a reactant gas feed into the fixed bed reactor comprising hydrogen, an inert gas and dimethyl ether (DME) or methanol to form a product gas mixture via a catylic reaction; J) condensing the product gas mixture from the fixed bed reactor of step I) to a product phase liquid; and K) separating the product phase liquid at room temperature into an aqueous phase, and into an organic phase which comprises the low-aromatics C.sub.5+ hydrocarbons.

18. The process as recited in claim 17, wherein the palladium ion-laden zeolite catalyst in step A) has a palladium loading having a mass fraction w.sub.palladium, based on a total catalyst mass, of 0.01 to 1%.

19. The process as recited in claim 17, wherein the inert material in step D) is silicon carbide, quartz glass, -aluminum oxide or a technical ceramic.

20. The process as recited in claim 17, wherein the EU-2 zeolite catalyst in step A) has an Si/Al substance ratio r.sub.Si/Al of 50 to 100 mol.Math.mol.sup.1.

21. The process as recited in claim 17, wherein the converting of the dimethyl ether (DME) or the methanol via the catylic reaction in step I) is performed with a volume fraction of the dimethyl ether (DME) or the methanol in the reactant gas feed of .sub.DME or methanol=1 to 10%.

22. The process as recited in claim 17, wherein the converting of the dimethyl ether (DME) or the methanol via the catylic reaction in step I) is performed with a volume fraction of the hydrogen in the reactant gas feed of .sub.hydrogen=1 to 50%.

23. The process as recited in claim 17, wherein the catalytic reaction of the dimethyl ether (DME) or the methanol in step I) is performed at a weight-hourly space velocity of 1 to 10 g.sub.DME or methanol.Math.g.sub.catalyst.sup.1.Math.h.sup.1.

24. The process as recited in claim 17, wherein a product fraction of the low-aromatics C.sub.5+-hydrocarbons is at least 35%.

25. The process as recited in claim 24, wherein a volume fraction of aromatics in the product fraction of the low-aromatics C.sub.5+ hydrocarbons under reaction conditions which allow for an initial dimethyl ether (DME) conversion X.sub.DME of 100% for an time-on-stream from X.sub.DME=100% to X.sub.DME=40% is below 3%.

26. The process as recited in claim 25, wherein under the reaction conditions which allow for the initial dimethyl ether (DME) conversion X.sub.DME of 100%, a volume fraction of branched olefins in the product fraction of the low-aromatics C.sub.5+ hydrocarbons is at least 50% for the time-on-stream from X.sub.DME=100% to X.sub.DME=40%, and a volume ratio of the branched olefins to linear olefins is at least 4.

27. The process as recited in claim 17, further comprising: transferring the product gas mixture from the fixed bed reactor in step I) through a heated pipe conduit to at least one cold trap; and preforming the condensing of the product gas mixture from the fixed bed reactor of step I) in step J) in the at least one cold trap.

28. The process as recited in claim 27, further comprising: during the transferring, diverting at least a substream of the product gas mixture into an online gas chromatograph; continually providing a determination of a dimethyl ether (DME) conversion or a methanol conversion and a composition of the product gas mixture via the online gas chromatograph; and then transferring the substream to the at least one cold trap.

29. The process as recited in claim 17, further comprising: converting the powder from step C) into extrudates or pellets prior to mixing the powder from step C) with the inert material to obtain the mixture in step D).

30. The process as recited in claim 17, wherein the mixing of the powder from step C) with the inert material to obtain the mixture in step D is performed with a volume ratio of the proton form of the palladium ion-laden zeolite catalyst to the inert material of 0.1 to 0.2;

31. The process as recited in claim 17, wherein the condensing of the product gas mixture from the fixed bed reactor of step I) and the separating the product phase liquid at room temperature into the aqueous phase and the organic phase which comprises the low-aromatics C.sub.5+ hydrocarbons of step J), comprises: a) transferring the product gas mixture from the fixed bed reactor of step I) through a heated pipeline to at least one cold trap; b) cooling the product gas mixture in the at least one cold trap with liquid nitrogen, wherein a product fraction containing the low-aromatics C.sub.5+ hydrocarbons is frozen to afford a solid product fraction; c) collecting the solid product fraction in a collection vessel of the at least one cold trap; d) thawing the solid product fraction collected in the collection vessel to provide a liquid product fraction and then withdrawing the liquid product fraction from the collection vessel of the at least one cold trap of step c) and separating the aqueous phase from the organic phase; and e) analyzing the organic phase from step d) in an external gas chromatograph.

32. A method of using the process as recited in claim 17 for producing low-aromatics C.sub.5+ hydrocarbons, the method comprising: providing the low-aromatics C.sub.5+ hydrocarbons via the method as recited in claim 17; and using the low-aromatics C.sub.5+ hydrocarbons as a starting material for a subsequent production of a synthetic fuel.

33. The method as recited in claim 32, where in the synthetic fuel is liquefied petroleum gas, gasoline, kerosene or diesel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

[0036] FIG. 1 shows a flow diagram of a reactor plant;

[0037] FIG. 2 shows the schematic construction of the fixed bed reactor 7 from FIG. 1;

[0038] FIG. 3 shows the DME conversion capacity of the catalyst prepared according to Example 1 as a function of DME conversion;

[0039] FIG. 4 shows the product selectivity for hydrocarbons of different chain lengths of the catalyst prepared according to Example 1 as a function of DME conversion;

[0040] FIG. 5 shows the composition of the liquid organic product phase in the chain length range C.sub.5-C.sub.11 of a catalyst prepared according to Example 1;

[0041] FIG. 6 shows the DME conversion capacity of the catalyst prepared according to Example 2 as a function of DME conversion;

[0042] FIG. 7 shows the product selectivity for hydrocarbons of different chain lengths of the catalyst prepared according to Example 2 as a function of DME conversion; and

[0043] FIG. 8 shows the composition of the liquid organic product phase in the chain length range C.sub.5-C.sub.11 of a catalyst prepared according to Example 2.

DETAILED DESCRIPTION

[0044] The present invention provides a palladium-laden zeolite catalyst H-EU-2 having a *MRE framework structure and a process for converting DME or methanol into low-aromatics hydrocarbons in a hydrogen stream using this catalyst.

[0045] The present invention further provides a use of the aforementioned process for producing low-aromatic hydrocarbons as starting materials for a subsequent production of synthetic fuels, for example, liquefied petroleum gas, gasoline, kerosene or diesel.

[0046] The process according to the present invention comprises the following steps which is, for example, performed in the specified sequence: [0047] A) loading an EU-2 zeolite catalyst in ammonium form with palladium ions by capillary impregnation; [0048] B) drying and calcining the palladium ion-laden zeolite catalyst from step A) to form the proton form of the zeolite catalyst; [0049] C) fractionating the zeolite catalyst from step B) into a catalyst powder (i.e., including granulate) having a particle size of 100 to 500 m, for example, between 200 and 300 m; [0050] D) mixing the zeolite catalyst, for example, the recited catalyst powder, from step C) with an inert material, for example, in a volume ratio of catalyst to inert material of 0.1-0.2; [0051] E) introducing the mixture from step D) into a fixed bed reactor; [0052] F) heating the fixed bed reactor from step E) to a reaction temperature between 350 C. and 450 C., for example, between 380 C. and 400 C., and passing a flow of inert gas through the fixed bed reactor; [0053] G) reducing the palladium ion-laden zeolite catalyst in a hydrogen stream in the fixed bed reactor; [0054] H) passing a flow of an inert gas through the fixed bed reactor and establishing the reaction pressure of 1-50 bar; [0055] I) introducing a reactant gas feed into the fixed bed reactor comprising hydrogen, an inert gas and DME and/or methanol, to form a product gas mixture by catalytic reaction; [0056] J) condensing the product gas mixture from the fixed bed reactor of step I); and [0057] K) separating the product phase liquid at room temperature into an aqueous phase and an organic phase containing C.sub.5+ hydrocarbons.

[0058] In an embodiment, the present invention provides a process mode which in particular relates to the aforementioned condensing of the product gas mixture according to step J) and the separating of the product phase liquid at room temperature into an aqueous phase and an organic phase containing the C.sub.5+ hydrocarbons according to step K). It then contains further substeps selected from the following which, in the case of a combination, can, for example, be performed in the specified sequence: [0059] a) transferring the product gas mixture from the fixed bed reactor of step I) through a heated pipeline to at least one cold trap; [0060] b) cooling the product gas mixture in the at least one cold trap with liquid nitrogen, wherein a product fraction containing low-aromatics C.sub.5+ hydrocarbons is frozen to afford a solid product fraction; [0061] c) collecting the solid product fraction in a collection vessel of the cold trap; [0062] d) thawing the solid product fraction to afford a liquid product fraction and subsequently withdrawing the liquid product fraction from the collection vessel of the cold trap of step (c) and separating the aqueous from the organic product phase; and [0063] e) analyzing the organic product phase from step d) in an external gas chromatograph.

[0064] In a first step A) of the process according to the present invention, a zeolite catalyst EU-2 in the ammonium form is loaded with palladium ions. The palladium ions are applied by capillary impregnation (incipient wetness impregnation), wherein a low palladium content having a mass fraction w.sub.Palladium of 0.01-1%, based on the total catalyst mass, is established. In an embodiment, the mass fraction w.sub.palladium=0.35%.

[0065] In the process according to the present invention, capillary impregnation (incipient wetness impregnation) is to be understood as meaning that an aqueous solution of a palladium salt, as a precursor of hydrogenation-active palladium(0), is applied to the zeolite catalyst EU-2 which has a pore volume identical to the volume of the solution added. The solution is drawn into the pores by capillary action.

[0066] In the process according to the present invention, the zeolite catalyst has an Si/Al amount of substance ratio r.sub.Si/Al of, for example, 50-100 mol.Math.mol.sup.1. The amount of substance ratio r.sub.ij is defined as the value of the quotient of the amount of substance n.sub.i of the one mixture component i under consideration and the amount of substance n.sub.j of the other mixture component j under consideration (standard DIN 1310: composition of mixed phases).

[0067] The catalyst is dried and calcined in a next step B) to expel the volatile constituents in the solution and to deposit the palladium salt on the catalyst surface. This converts the EU-2 catalyst from the ammonium form into the proton form H-EU-2 by liberation of NH.sub.3.

[0068] In a further step C), the zeolite catalyst is fractionated to a particle size of 100 to 500 m, for example, to a particle size of 224 to 300 m.

[0069] In an embodiment, the fractionated zeolite catalyst from step C) can, for example, be converted into extrudates, pellets or other shaped bodies in the course of a catalyst shaping (S. Devyatkov et al., Chimica OggiChemistry Today 2015, 33, 6, 57-64; R. Bingre et al., Catalysts 2018, 8, 163). This can, for example, be effected before the mixing in step D). Compared to a catalyst powder, extrudates, pellets or other shaped articles, especially in an industrial production process, are easier to handle and meter and are substantially more stable. The mixing of the zeolite catalyst with an inert material in step D) is then carried out not with the catalyst powder, but rather with the preformed catalyst.

[0070] In the following step D) of the process according to the present invention, the zeolite catalyst from step C) is mixed with an inert material, wherein the volume ratio of catalyst to inert material is 0.1-0.2. The volume ratio .sub.ij is defined as the value of the quotient of the volume Vi of the one mixture component i under consideration and the volume V.sub.j of the other mixture component j under consideration (standard DIN 1310: composition of mixed phases).

[0071] Suitable inert materials in the process according to the present invention can, for example, include silicon carbide, quartz glass (sand or pearls), -alumina or other technical ceramics.

[0072] The process according to the present invention can, for example, employ silicon carbide having a particle size of 10 to 500 m, for example, having a particle size of 100 to 180 m.

[0073] In step E) of the process according to the present invention, the mixture from step D) is introduced into a fixed bed reactor and forms the reaction zone in the fixed bed reactor (see FIG. 2). In an embodiment, this reaction zone can, for example, be flanked by an inflow zone and an outflow zone which is composed of the aforementioned inert material. In the process according to the present invention, the inert material is used for catalyst stabilization. Since the conversion of DME or methanol into low-aromatics hydrocarbons in the process according to the present invention is an exothermic reaction, the inert material provides a virtually isothermal temperature profile in the reaction zone. The process according to the present invention can, for example, employ silicon carbide as inert material in the inlet zone and the outlet zone.

[0074] In step F) of the process according to the present invention, the fixed bed reactor is heated to the reaction temperature and a flow of inert gas is passed therethrough. The reaction temperature in the process according to the present invention is 350-450 C., for example, 380-400 C.

[0075] In the process according to the present invention, it has been found that a reaction temperature of at least 380 C. is advantageous for formation of longer-chain hydrocarbons at high reactant conversion.

[0076] The employed inert gas can, for example, be N.sub.2, He or Ar. The inert gas can, for example, be N.sub.2 (see FIG. 1).

[0077] In step G) of the process according to the present invention, the palladium ion-laden zeolite catalyst is reduced in a hydrogen stream in the fixed bed reactor, thus producing a zeolite catalyst containing hydrogenation-active palladium(0).

[0078] In step H) of the process according to the present invention, a flow of inert gas is again passed through the fixed bed reactor while simultaneously establishing the reaction pressure. The inert gas can, for example, be selected from N.sub.2, He or Ar. In an embodiment, the inert gas is N.sub.2. The reaction pressure in the process according to the present invention is 1-50 bar, for example, 1-30 bar. It has been found in the process according to the present invention that a reaction pressure of 20-30 bar provides for particularly high reaction conversions (see FIG. 6).

[0079] In step I) of the process according to the present invention, a reactant gas feed is introduced into the fixed bed reactor. The reactant gas feed includes hydrogen, an inert gas and DME or methanol. In an embodiment, the volume fraction in the reactant gas feed .sub.DME or methanol is 1-10%, for example, 5%. The volume fraction of hydrogen in the reactant gas feed .sub.hydrogen in the process according to the present invention is 1-50%, for example, 10-30%. The volume fraction .sub.i is defined as the value of the quotient of the volume V.sub.i of a mixture component i under consideration and the total volume V.sub.0 before the mixing operation. The latter is the sum of the starting volumes of all mixture components (including i) of the mixture (Standard DIN 1310: composition of mixed phases).

[0080] In the process according to the present invention, it has been found that, in the reactant gas feed, a volume ratio .sub.H2/DME or methanol of hydrogen to DME or methanol of 4 results in particularly high reaction conversions and relatively high long-term stability of the catalyst (see FIG. 6).

[0081] In the process according to the present invention, the reaction of DME or methanol is carried out at a weight hourly space velocity (WHSV) of 0.1-20 g.sub.DME or methanol.Math.g.sub.catalyst.sup.1.Math.h.sup.1, for example, at a WHSV of 1-5 g.sub.DME or methanol.Math.g.sub.catalyst.sup.1.Math.h.sup.1.

[0082] After the forming of the product gas mixture in step I) and before the condensing in step J), the product gas mixture can, for example, be transferred from the fixed bed reactor through a heated pipe conduit to at least one cold trap in which the condensation is carried out. In the course of this transferring, at least a substream of the product gas mixture (for example, diverted from the heated pipe conduit) can, for example, be diverted into an online gas chromatograph for continuous determination of the DME or methanol conversion and the composition of the product gas mixture and subsequently passed to the cold trap (either directly or via a return to the heated pipe conduit).

[0083] In step J) of the process according to the present invention, the product gas mixture formed in the aforementioned step I) is condensed. In step K), the product phase liquid at room temperature is then separated into an aqueous phase and an organic phase containing C.sub.5+ hydrocarbons.

[0084] This can, for example, comprise a transferring of the product gas mixture from the fixed bed reactor to the condensation, for example, into at least one cold trap through a heated pipe conduit to the at least one cold trap. The transferring can, for example, comprise diverting the product gas mixture, for example, at least a substream of the product gas mixture, through an online gas chromatograph. During this optional complete or at least partial diverting of the product gas stream, the online (i.e., real-time) gas chromatograph continuously monitors the DME or methanol conversion and the composition of the product gas mixture.

[0085] The product gas mixture can, for example, also be cooled with liquid nitrogen in at least one cold trap after the optional online gas chromatography analysis. The product fraction containing low-aromatics C.sub.5+ hydrocarbons can, for example, be frozen and collected in a collection vessel of the cold trap. In a process embodiment, the frozen product fraction can then, for example, be thawed and withdrawn from the collection vessel of the cold trap as a liquid product and the organic product phase separated from the aqueous phase in a phase separator. In an embodiment, the organic product phase can then, for example, be analyzed in an external gas chromatograph, for example, according to the specifications of the standards EN ISO 22854 or ASTM D6839 (see FIG. 1).

[0086] The process according to the present invention has the following advantages:

[0087] The organic product mixture (gasoline) in the chain length range C.sub.5-C.sub.11 is gasoline-like and features a comparatively low aromatics content .sub.aromatics of not more than about 3%. Analyses of the paraffins and olefins thus obtained indicate a comparatively high degree of molecular branching. This indicates a good fuel compatibility of the organic product phase (compare Tables 1 and 2).

[0088] In addition to optimizing the product spectrum, the process according to the present invention exhibits a high catalyst activity, high conversions, high space-time yields, and a huge increase in catalyst stability and lifetime. The palladium-laden H-EU-2 catalyst exhibits a high long-term stability even at high temperatures. The long-term stability makes it possible to achieve high conversions and high selectivities over periods of several days to several weeks (compare FIGS. 3 and 6).

[0089] In the process according to the present invention, the loading of the zeolite with palladium leads to a very high stability of the catalyst to sintering, thus also allowing for selection of relatively high reaction temperatures of around 400 C. This results in high catalyst activity and high DME/methanol conversion. The addition of hydrogen not only favorably influences the product spectrum in the process according to the present invention, but also increases the long-term stability of the catalyst system compared to the prior art.

[0090] These effects are surprising since the one-dimensional pore system of the zeolite EU-2 should promote rapid catalyst deactivation in the DTG/MTG reaction due to the blocking of the pore channels by large molecules, for example, methylated aromatics. Although the product mixture contains small amounts of methylated aromatics and higher hydrocarbons, rapid catalyst deactivation is not observed in the process according to the present invention. The use of the hydrogenation catalyst Pd(0) in conjunction with hydrogen should furthermore suppress the formation of longer hydrocarbon chains in the process according to the present invention and increase the formation of low molecular weight hydrocarbons, for example, methane, ethylene or ethane. These are undesirable byproducts of the DTG/MTG reaction and are formed only to a subordinate degree according to the present invention.

[0091] The process according to the present invention may be used to produce synthetic fuels, for example, liquefied petroleum gas, gasoline, kerosene or diesel. Applications as solvents and in the production of chemicals are likewise possible.

[0092] The present invention is more particularly elucidated with reference to the following figures, working examples and descriptions. All specified features and combinations thereof are thereby not limited only to these figures and working examples and their embodiments. On the contrary, these are to be regarded as combinable as representatives of further embodiments which are possible but not explicitly specified as working examples.

[0093] FIG. 1 shows a flow diagram of a reactor plant. The reactor plant comprises the feeding regions of reactant and inert gases 1-5, whose flows are adjusted using appropriate mass flow controllers 6. Arranged downstream thereof is the fixed bed reactor 7 which is coupled to a pressure control valve 8. Arranged downstream thereof are apparatuses for product workup composed substantially of at least one cold trap 10 which cools the product gas mixture with liquid nitrogen. Analysis of the product mixtures is effected using an online gas chromatograph 9 which is operated using a substream continuously withdrawn from the product stream. Further elements include a flowmeter 12 and an apparatus for discharging gaseous components (offgas 11).

[0094] FIG. 2 shows the schematic construction of the fixed bed reactor 7 from FIG. 1 comprising an inlet 13 for the reactant gas feed and an outlet 14 for the reaction products. The catalyst powder was fractionated to a particle size dp in the range from 224 to 300 m. The samples were subsequently mixed with inert silicon carbide (SiC, particle size in the range from 100 to 180 m) (0.333 g of catalyst in SiC in a volume ratio catalyst/SiC=0.1) to prevent a temperature elevation in the catalyst bed as a result of the exothermic DTG reaction and to provide a virtually isothermal temperature profile in the reaction zone (Taxial<2 K). The catalyst/SiC mixture formed the reaction zone 16 in a fixed bed reactor made of stainless steel (internal diameter di=12 mm). The reaction zone 16 was flanked by an inlet zone and an outlet zone 17 composed of inert SiC, which were secured in the reaction tube by inert glass wool 18. The reactor was heated using three heating blocks. Two thermocouples were installed in each heating block to control and monitor the temperature. The axial temperature profile in the reaction zone 16 was further recordable via a thermocouple in the tube reactor movable within a guide sleeve 15.

[0095] FIG. 3 shows the DME conversion capacity of the catalyst prepared according to Example 1 as a function of DME conversion.

[0096] FIG. 4 shows the product selectivity for hydrocarbons of different chain lengths of the catalyst prepared according to Example 1 as a function of DME conversion.

[0097] FIG. 5 shows the composition of the liquid organic product phase in the chain length range C.sub.5-C.sub.11 of a catalyst prepared according to Example 1. Sampling was carried out from commencement of the experiment until reduction of the conversion to X.sub.DME=40%. Analysis was carried out according to the specifications of the standards EN ISO 22854 or ASTM D6839.

[0098] FIG. 6 shows the DME conversion capacity of the catalyst prepared according to Example 2 as a function of DME conversion.

[0099] FIG. 7 shows the product selectivity for hydrocarbons of different chain lengths of the catalyst prepared according to Example 2 as a function of DME conversion.

[0100] FIG. 8 shows the composition of the liquid organic product phase in the chain length range C.sub.5-C.sub.11 of a catalyst prepared according to Example 2. Sampling was carried out from commencement of the experiment until reduction of the conversion to X.sub.DME=40%. Analysis was carried out according to the specifications of the standards EN ISO 22854 or ASTM D6839.

EXAMPLES

Example 1

Catalyst Preparation Reference Material

[0101] Zeolite EU-2 of structure type *MRE was used as the starting material for the investigations. The EU-2 powder having an Si/Al ratio of r.sub.Si/Al=78 mol.Math.mol.sup.1 and a specific surface area of 256 m.sup.2.Math.g.sup.1 was provided in the ammonium form (NH.sub.4 form) and was initially freed of potential impurities by an ion exchange process (3 ion exchanges in a 1M NH.sub.4NO.sub.3 washing solution at 75 C. for 2 h in each case). The powder was then dried overnight in a vacuum drying cabinet at 80 C. and 10 mbar. The dry powder was then heated to a temperature of 550 C. in a calcining furnace at a heating rate of 2 K.Math.min.sup.1 and calcined for 6 h at this temperature. The NH.sub.4 form of the zeolite powder was converted into the proton form (H form, H zeolite). The zeolite catalyst H-EU-2 is used as a reference material to demonstrate the advantages of a metal-laden catalyst in a process for converting DME or methanol into low-aromatics hydrocarbons in a hydrogen stream using this catalyst.

Example 2

Catalyst Preparation of Metal-Laden Zeolite

[0102] To produce metal-laden zeolite catalysts, zeolite EU-2 of structure type *MRE having the same material properties as in Example 1 was used. After 3 ion exchanges (1M NH.sub.4NO.sub.3 washing solution at 75 C. for 2 h in each case), the powder in the ammonium form was dried overnight in a vacuum drying cabinet at 80 C. and 10 mbar. Loading with palladium was then carried out by incipient witness impregnation. The EU-2 powder was impregnated dropwise with a solution of Pd(NO.sub.3).sub.2(NH.sub.3).sub.4xH.sub.2O in deionized water. The resulting paste was then dried overnight in a drying oven at 40 C. The dry powder was then heated to a temperature of 550 C. in a calcining furnace at a heating rate of 2 K.Math.min.sup.1 and calcined for 6 h at this temperature. The NH.sub.4 form of the zeolite was converted into the proton form (H form, H zeolite).

Example 3

Conversion of DME

[0103] The catalyst powder was fractionated to a particle size d.sub.p in the range from 224 to 300 m. The samples were subsequently diluted with inert silicon carbide (SiC, particle size in the range from 100 to 180 m) in a mixing ratio of .sub.catalyst/SiC=0.1 to prevent a temperature elevation in the catalyst bed as a result of the exothermic DTG reaction and to provide a virtually isothermal temperature profile in the reaction zone (T.sub.axial<2 K). The catalyst/SiC mixture formed the reaction zone 16 in a fixed bed reactor made of stainless steel (internal diameter d.sub.i=12 mm). The reaction zone 16 was flanked by an inlet zone and an outlet zone 17 composed of inert SiC, which were secured in the reaction tube by inert glass wool 18. The construction of the fixed bed reactor is schematically illustrated in FIG. 2. The reactor was heated by a heating jacket composed of three aluminum blocks, each comprising four tight-fitting heating cartridges. During the heating process, the reactor with a flow of 80 ml.sub.n.Math.min.sup.1 of N.sub.2 was passed through the reactor.

[0104] The heating blocks were thermally insulated by a vermiculite jacket. This minimized external heat loss and provided a uniform heat distribution in the reactor coupled with good reliability. Two thermocouples were installed in each heating block to control and monitor the temperature. The axial temperature profile in the reaction zone 16 was further recordable via a thermocouple in the tube reactor movable within a guide sleeve 15. Heating of the fixed bed reactor to reaction temperature (400 C.) was followed by reduction of the sample in the case of the metal-laden zeolite catalyst (Pd/H-EU-2). A flow of 80 ml.sub.n.Math.min.sup.1 of H.sub.2 was passed through the reactor for 5 h. This step was omitted in the case of the reference sample without metal loading (H-EU-2).

[0105] Following the reduction, a flow of 80 ml.sub.n.Math.min.sup.1 of N.sub.2 was passed through the reactor while the reaction pressure was adjusted via a manual supply pressure control valve (1.5-30 bar). The reaction investigation of the metal-laden zeolite catalyst (Pd/H-EU-2) was then carried out by passing a reactant gas feed consisting of .sub.DME=5% and also N.sub.2 and H.sub.2 in varying proportions into the reactor. The reactant gas stream was selected so that the experiments were performed at a WHSV of 1.5 g.sub.DME.Math.g.sub.catalyst.sup.1.Math.h.sup.1 unless otherwise stated.

[0106] For analysis, the reaction products were passed through a pipe conduit heated to 180 C. to an online gas chromatograph (for example, Agilent 7890B) fitted with an FID (flame ionization detector) for determining hydrocarbons/oxygenates and a TCD (thermal conductivity detector) for determining permanent gases/water. Assignment of the peaks of hydrocarbons in the range C.sub.1-C.sub.4, the oxygenates methanol and DME and the permanent gases H.sub.2, N.sub.2, CO.sub.2 and CO was undertaken with the aid of calibration gases from Air Liquide. The further peaks of the FID spectrum were combined into the group C.sub.5+ in the online analysis. The DME conversion X.sub.DME of the samples was calculated via the ratio of the reacted DME amount (difference between inflowing DME stream N.sub.DME,in and the outflowing DME stream N.sub.DME,out) to the DME inflow stream according to equation (I):

[00001]$\begin{array}{cc}{X}_{DME}=\frac{{\stackrel{.}{N}}_{\mathrm{DME},\mathrm{in}}-{\stackrel{.}{N}}_{\mathrm{DME},\mathrm{out}}}{{\stackrel{.}{N}}_{\mathrm{DME},\mathrm{in}}}.Math.100\%& \left(I\right)\end{array}$

[0107] The conversion capacity of a catalyst describes the cumulatively converted mass of a reactant based on the mass of the catalyst m.sub.cat as a function of the time-on-stream (TOS). Plotting the conversion capacity above the conversion allows for comparability of the deactivation behavior in long-term measurements performed with different WHSV values. The conversion capacity is derived according to equation (II) from the product of the WHSV and the integral area under a corresponding conversion-TOS curve:

[00002]$\begin{array}{cc}\mathrm{conversion}\mathrm{capacity}=\frac{m_{\mathrm{DME}}}{m_{\mathrm{cat}}}=\mathrm{WHSV}.Math.{}_0^{TOS}{X}_{DME}\mathrm{dTOS}& \left(\mathrm{II}\right)\end{array}$

[0108] The selectivities S of the products i formed from DME (S.sub.i,DME) was formed by integration of the areas of the respective GC-FID signals I.sub.i relative to the total GC-FID area I.sub.total minus the DME signal I.sub.DME and the methanol signal I.sub.methanol. Methanol is in equilibrium with DME via the dehydration/hydration reaction and is considered a reactant of the MTG reaction which is analogous to the DTG reaction. The selectivities for the carbon-containing (by) products CO and CO.sub.2 were also subtracted from the quotient of the signal intensities. These were not captured by the GC-FID signal, but were determinable from the GC-TCD spectrum according to equation (III) using a multi-point calibration with calibration gases from Air Liquide:

[00003]$\begin{array}{cc}{S}_{i,\mathrm{DME}}=\frac{v_i}{v_{\mathrm{DME}}}.Math.\frac{{\stackrel{.}{N}}_{i,\mathrm{out}}}{{\stackrel{.}{N}}_{\mathrm{DME},\mathrm{in}}-{\stackrel{.}{N}}_{\mathrm{DME},\mathrm{out}}}.Math.100\%& \left(\mathrm{III}\right)\end{array}$

[0109] The selectivity S.sub.i,DME for the hydrocarbon products was thus determined according to equation (IV):

[00004]$\begin{array}{cc}{S}_{i,\mathrm{DME}}=\frac{I_i}{I_{\mathrm{total}}-I_{\mathrm{DME}}-I_{\mathrm{Methanol}}}.Math.\left(100\%-S_{\mathrm{CO},\mathrm{DME}}-S_{\mathrm{CO}2,\mathrm{DME}}\right)& \left(\mathrm{IV}\right)\end{array}$

[0110] For more precise determination of the products in the chain length range C.sub.5+, a cold trap for condensation/freezing of these components was arranged downstream of the online gas chromatograph. The liquid organic condensate in the cooling trap was analyzed after the end of the experiment in an M4 reformulyzer (from PAC). A flow diagram of the experimental apparatus for reaction investigation of the conversion of DME over metal-laden H-EU-2 catalysts is shown in FIG. 1.

Example 4

[0111] In Example 4, the catalytic performance of an H-EU-2 catalyst produced by the preparation method specified in Example 1 was tested. The reaction described in this example was performed at 400 C., 20 bar of reaction pressure, and a WHSV of 1.5 g.sub.DME.Math.g.sub.catalyst.sup.1.Math.h.sup.1 at a constant volume fraction .sub.DME=5% in N.sub.2. The DME conversion capacity of the catalyst is plotted above the DME conversion X.sub.DME in FIG. 3. The conversion capacity of the H-EU-2 catalyst is used as a reference for classifying the advantages in terms of activity and long-term stability of a metal-laden catalyst in a process for converting DME or methanol into low-aromatics hydrocarbons in a hydrogen stream which uses the catalyst.

Example 5

[0112] In Example 5, the product selectivity of an H-EU-2 zeolite catalyst produced according to Example 1 in a reaction at 400 C., 20 bar of reaction pressure and a WHSV of 1.5 g.sub.DME.Math.g.sub.catalyst.sup.1.Math.h.sup.1 at a constant volume fraction .sub.DME=5% in N.sub.2 was determined. FIG. 4 shows the selectivity in terms of the chain length of the resulting hydrocarbons (C.sub.1, C.sub.2, C.sub.3, C.sub.4 and C.sub.5+) above the DME conversion X.sub.DME as determined with the online gas chromatograph. Hydrocarbons in the C.sub.5+ chain length range were the desired product components. The proportion of the product fraction C.sub.5+ was in the range from 45-85% over the total experimental duration.

Example 6

[0113] In Example 6, the composition of the liquid product phase from the catalytic conversion of DME over an H-EU-2 catalyst prepared according to Example 1 was determined. The experimental procedure was carried out as described in Example 3 at a temperature of 400 C., a WHSV of 1.5 g.sub.DME.Math.g.sub.catalyst.sup.1.Math.h.sup.1 at a reaction pressure of 20 bar, and a constant volume fraction .sub.DME=5% in N.sub.2. The sample for analysis of the liquid organic product phase (C.sub.5-C.sub.11) was generated in the time window from reaction commencement until a decrease in DME conversion to X.sub.DME=40%. The analysis was carried out according to the specifications of the standards EN ISO 22854 and ASTM D6839 and the volume fractions of the products are shown graphically in FIG. 5 as a function of carbon number and listed numerically in Table 1. A high olefin content was found for all chain lengths, wherein branched isomers predominate markedly. Paraffins and aromatics were present only in small amounts. The volume fraction of the aromatics was below 2%.

Example 7

[0114] In Example 7, the catalytic performance of a Pd/H-EU-2 catalyst produced by the preparation method specified in Example 2 was tested. The reaction described in this example was performed at 400 C., 20 bar of reaction pressure and a WHSV of 1.5 g.sub.DME.Math.g.sub.catalyst.sup.1.Math.h.sup.1 at constant volume fractions .sub.DME=5%, .sub.H2=20% and .sub.N2=75%. The DME conversion capacity of the catalyst Pd/H-EU-2 is plotted above the DME conversion X.sub.DME in FIG. 6. In a process for converting DME or methanol into low-aromatics hydrocarbons in a hydrogen stream, the conversion capacity of the catalyst Pd/H-EU-2 is increased more than five-fold compared to the reference system in Example 4. This implies a markedly elevated activity and stability of the catalyst.

Example 8

[0115] In Example 8, the product selectivity of the Pd/H-EU-2 catalyst produced according to Example 2 in a reaction at 400 C., 20 bar of reaction pressure, and a WHSV of 1.5 g.sub.DME.Math.g.sub.catalyst.sup.1.Math.h.sup.1 at constant volume fractions .sub.DME=5%, .sub.H2=20% and .sub.N2=75% was determined. FIG. 7 shows the selectivity in terms of the chain length of the resulting hydrocarbons (C.sub.1, C.sub.2, C.sub.3, C.sub.4 and C.sub.5+) above the DME conversion X.sub.DME as determined with the online gas chromatograph. Hydrocarbons in the C.sub.5+ chain length range were the desired product components. The proportion of the product fraction C.sub.5+ was in the range from 35-80% over the total experimental duration. The excellent selectivity for the C.sub.5+ product group of the reference sample from Example 5 is reduced only slightly by the particular embodiment of a Pd/H-EU-2 catalyst in a process for reacting DME or methanol to low-aromatic hydrocarbons in a hydrogen stream.

Example 9

[0116] In Example 9, the composition of the liquid product phase from the catalytic conversion of DME over a Pd/H-EU-2 catalyst prepared according to Example 2 was determined. The experimental procedure was carried out as described in Example 3 at a temperature of 400 C., a WHSV of 1.5 g.sub.DME.Math.g.sub.catalyst.sup.1.Math.h.sup.1 at a reaction pressure of 20 bar, and constant volume fractions .sub.DME=5%, .sub.H2=20% and .sub.N2=75%. The analysis was carried out according to the specifications of the standards EN ISO 22854 and ASTM D6839 and the volume fractions of the products are shown graphically in FIG. 8 as a function of carbon number and listed numerically in Table 2. Analogous to the reference sample from Example 6, a high olefin content was found for all chain lengths. Branched isomers likewise predominate markedly. In a process for converting DME or methanol into low-aromatics hydrocarbons in a hydrogen stream, the paraffin fraction is slightly elevated in the embodiment of a Pd/H-EU-2 catalyst compared to the reference from Example 6. The volume fraction of the aromatics is in turn low and is below 3%.

[0117] Table 1 shows the numerical values of the gas chromatographic analysis of the liquid organic product phase (C.sub.5-C.sub.11) which was generated in the time window from reaction commencement (initial DME conversion X.sub.DME of 100%) until a decrease in DME conversion to X.sub.DME=40% (production of the catalyst according to Example 1). The analysis was performed according to the standards EN ISO 22854 and ASTM D6839 and showed a very low volume fraction of aromatics in the sample of 1.1% and a very high volume fraction of olefins of more than 90%. The volume ratio of branched olefins to linear olefins was high and amounted to 4.2.

[0118] Table 2 shows the numerical values of the gas chromatographic analysis of the liquid organic product phase (C.sub.5-C.sub.11) which was generated in the time window from reaction commencement (initial DME conversion X.sub.DME of 100%) until a decrease in DME conversion to X.sub.DME=40% (production of the catalyst according to Example 2). The analysis was carried according to the standards EN ISO 22854 and ASTM D6839 and showed a very low volume fraction of aromatics of 2.6% and a high volume fraction of olefins of 77%. The volume ratio of branched olefins to linear olefins was high and amounted to 4.1.

TABLE-US-00001 TABLE 1 Carbon Total n-paraffins i-paraffins Naphthenes n-olefins i-olefins Cyclic Aromatics number (%) (%) (%) (%) (%) (%) olefins (%) (%) 5 24.2 0.3 0.6 0.2 6.0 17.1 6 25.2 0.3 0.6 0.9 4.1 18.6 0.7 7 18.9 0.2 0.5 1.0 1.7 12.5 2.7 0.2 8 14.6 0.1 0.3 0.8 0.7 8.3 4.0 0.3 9 9.6 0.2 0.6 0.3 5.4 2.6 0.5 10 4.9 0.3 0.9 2.8 0.8 0.1 11 2.7 0.4 1.9 0.4 Total 100 1.3 2.2 3.8 15.6 65.1 10.9 1.1

TABLE-US-00002 TABLE 2 Carbon Total n-paraffins i-paraffins Naphthenes n-olefins i-olefins Cyclic Aromatics number (%) (%) (%) (%) (%) (%) olefins (%) (%) 5 31.5 2.2 2.5 0.4 7.0 19.2 0.2 6 26.2 1.9 2.3 1.7 3.5 15.5 1.2 0.1 7 17.0 0.9 1.5 1.5 1.1 8.2 3.3 0.3 8 11.9 0.5 0.9 1.1 0.4 4.4 4.0 0.7 9 7.5 0.2 0.5 0.7 0.1 2.6 2.5 0.9 10 4.0 0.1 0.4 0.4 0.1 1.9 0.6 0.6 11 1.8 0.5 0.1 0.7 0.5 0.4 Total 100 6.3 8.3 5.8 12.9 52.3 11.8 2.6

LIST OF REFERENCE NUMERALS

[0119] 1 DME/N.sub.2 or Methanol/N.sub.2 reactant gas mixture [0120] 2 Hydrogen [0121] 3 N.sub.2 inert gas [0122] 4 He inert gas [0123] 5 Ar inert gas [0124] 6 Mass flow controllers [0125] 7 Fixed bed reactor [0126] 8 Pressure control valve [0127] 9 Online gas chromatograph [0128] 10 Cold trap [0129] 11 Offgas [0130] 12 Flowmeter [0131] 13 Inlet [0132] 14 Outlet [0133] 15 Guide sleeve for axial thermocouple [0134] 16 Reaction zone with catalyst and SiC [0135] 17 Inlet or outlet zone [0136] 18 Glass wool