DE102007059129A1 - Catalyst with increased olefin selectivity for the conversion of oxygenates to olefins - Google Patents

Abstract

The invention relates to the use of a catalyst comprising crystalline aluminosilicates for converting oxygenates to olefins. The catalyst used is subjected to a thermal treatment in the alkaline state prior to use in the reaction of conversion of oxygenates to olefins. The catalyst is characterized by a starting selectivity to olefins of more than 95%.

Description

Field of the invention

The The present invention relates to the use of a catalyst based on aluminosilicates for the conversion of oxygenates to olefins.

State of the art

A typical reaction for the conversion of oxygenates to olefins can be described by the following equation:

For the first step, the equilibrium reaction, a conventional dehydrogenation catalyst, for example γ-alumina, or else a catalyst described in the context of the present invention can be used as a so-called pre-catalyst. In principle, the reaction of the methanol and / or dimethyl ether vapor and steam-containing reaction mixture can take place in a tubular reactor on an indirectly cooled catalyst, as for example in the EP 0 448 000 A1 is described.

in the second step, the reaction reaction to olefins, takes place on the one hand the catalyst described in the context of the present invention Application, on the other hand, other catalysts be used on a zeolite basis. Basically for that suitable catalysts based on crystalline aluminosilicates are known from the prior art.

For the reaction described above are mostly zeolitic catalysts using different methods of change activity, selectivity or runtime behavior the catalysts are known. For this purpose, zeolites or the based catalysts with other catalytically active Materials modified. Known catalytically active materials For example, metals such as Ni, Fe, Cu, Mn. Furthermore, can the zeolites with promoters or stabilizers, eg. B. phosphor, be modified.

Processes for the conversion of oxygenates to olefins based on microporous aluminosilicates or silicoaluminophosphates are described, for example, in US Pat US 4,499,327 or US Pat. No. 6,518,475 disclosed. US 3,894,104 discloses an analogous process for the conversion of methanol to fuel (MTG - "methanol to gasoline").

The effectiveness of such processes depends essentially on two catalyst properties. On the one hand by the hydrothermal stability and thus the catalyst life, on the other hand by the selectivity to olefins, in particular to C ₃ olefins (propylene).

To improve the runtime behavior, either the pore volume of the catalyst can be increased by known methods (unpublished German patent application DE 10 2005 052 0162 ), or a modification of the catalyst with metals are carried out (unpublished German patent application DE 10 2006 037 314 ). To increase the selectivity of the catalyst to C ₃ -olefins, a treatment with water vapor can have a positive effect (steams). However, the method has the disadvantage that while the number of active centers of the catalyst is reduced and in addition an undesirable reduction of the catalyst life occurs.

The Object of the present invention is thus in the provision a catalyst that has increased effectiveness in the conversion of oxygenates to olefins shows.

Brief description of the invention

The The object is achieved by the use of the invention a catalyst comprising aluminosilicates which is a thermal Treatment in the alkaline state was subjected to implementation from oxygenates to olefins, dissolved.

The catalyst obtained by the thermal treatment in the alkaline state is preferred a pore size of 0.5 to 1 nm, with non-shape selective active sites on the crystallite surface are deactivated. In the reaction of oxygenates to olefins, the catalyst is preferably characterized in that it has a selectivity to olefins of more than 95% already at the start of the reaction.

Detailed description the invention

The Aluminosilicate used in the invention is preferred a zeolite or a zeolite-like material, wherein in principle all zeolites known in the art can be used. The preparation of the zeolites may be according to known in the art Methods are done.

zeolites or zeolite powder are usually from so-called. Synthetic Gels in a hydrothermal crystallization produced.

A hydrothermal crystallization of a zeolite is for example in the EP 0 443 539 disclosed. To prepare a synthesis gel for the preparation of a zeolite, it is usually necessary to use scaffold-forming feedstocks (for example silicon, aluminum, boron, gallium or germanium sources), mineralizers (sodium hydroxide, sodium fluoride, sodium sulfate, hydrofluoric acid and the like), a solvent (mostly water) and a so-called structure-directing agent or template.

As structure-directing agent or template inorganic template or organic template can be used. As an inorganic template Na ⁺ ions or K ⁺ ions can be used. For example, tetrapropylammonium bromide (MFI zeolite) is suitable as the organic template.

When Scaffolding component is usually needed a silicon source, for example precipitated silica. With regard to the aluminum source, there are no special ones per se Restrictions, so all the usual and the Professional common aluminum sources can be used. For example, activated alumina, γ-alumina, is suitable. Aluminum hydroxide, sodium aluminate, aluminum nitrate, or aluminum sulfate.

According to the invention thus the use of a catalyst based on aluminosilicates, preferably crystalline aluminosilicates, for the reaction of oxygenates to olefins, wherein the catalyst prior to its use in said Reaction reaction of a thermal treatment in the alkaline state has been subjected. The alkaline state results from a previous alkaline treatment of the aluminosilicate in aqueous Medium at pH greater 7, causing the surface of the catalyst is made alkaline. The catalyst therefore becomes before its use in the said reaction reaction of an alkaline Treatment and then subjected to a thermal treatment.

The alkaline treatment of the catalyst can be done directly afterwards to the synthesis of the aluminosilicate. Preferably, this should at a pH of 9 to 14, preferably 10 to 12, in aqueous medium respectively. The alkaline treatment is usually added Temperatures of 20 to 100 ° C, preferably 40 to 80 ° C over a period of 0.1 to 100 hours, preferably 0.5 to 2 hours, carried out. After synthesis and alkaline treatment the aluminosilicate is filtered off and with or without preceding Drying and without prior washing by calcining thermally treated. It can thus also the wet filter cake with adhering Mother liquor can be used.

The Calcination (thermal treatment) usually takes place at temperatures between 250 and 650 ° C, preferably at 300 to 600 ° C, preferably over a period of time from 6-12 hours.

The alkaline treatment can also be carried out on a conventional zeolite (aluminosilicate), which is ground to a powder and in an alkaline aqueous solution, optionally with the addition of SiO ₂ , z. B. 10% SiO ₂ , at a pH greater than 7, preferably 9 to 14, preferably 10 to 12, slurried. The slurry is heated with stirring to 20 to 100 ° C, preferably 40 to 80 ° C, and held for 0.1 to 100 hours, preferably 0.5 to 2 hours, at this temperature, then filtered off and without washing, including the adhering alkaline Compound and optionally adherent SiO ₂ particles at temperatures between 250 and 650 ° C, preferably at 300 to 600 ° C, calcined.

Further Process steps, such as ion exchange and molding processes can will be carried out subsequently and will be discussed below described.

As alkaline solutions, for example, hydroxide solutions of lithium, sodium or potassium hydroxide or other hydroxide solutions known in the art. Combinations of different hydroxide solutions can also be used.

zeolite catalysts for the conversion of oxygenates to olefins, which are known from the prior art Technique, have at the beginning of the reaction reaction one Selectivity to olefins, especially to propylene, from about 90% (propylene to the total C3 fraction), which is after a longer period of several 1000 hours to about 95% increase. However, this is partly due to activity losses and thus sales decline.

Surprisingly performs a thermal treatment of an aluminosilicate in alkaline state to increased olefin selectivity. The selectivity is especially with respect to C2 and C3 olefins pronounced, with a selectivity of more than 95% already at the start of a reaction reaction of oxygenates Olefins is given. In particular, an increase in selectivity to the olefin propylene over the alkane propane observed. The high selectivity already at the start of the reaction leads thus also to a yield gain of about 5% over several 1000 hours. The increase in selectivity is probably without being bound to this theory, to a narrowing of the zeolite pores, which is due to the alkaline thermal treatment, due.

Further is the thermal treatment in the alkaline state the Crystallite surface of the zeolite changed so that non-shape-selective active sites are deactivated. The Deactivation of the active centers occurs at the outer Surface of the zeolite crystals and leads as well to reduce the formation of coke in the intermediate grain volume of the Zeolites in reaction reactions of oxygenates to olefins and thus to an improved runtime behavior of the catalyst. That is, the time until the need for catalyst regeneration by combustion of the generated and the reaction reaction or the Diffusion obstructing coke can be dramatically increased.

Usually zeolites are used in the prior art for the reaction reaction of oxygenates to olefins, which have a SiO ₂ / Al ₂ O ₃ molar ratio of greater than 100. These zeolites are hydrothermally more stable than those having a lower SiO ₂ / Al ₂ O ₃ molar ratio, but have a lower starting activity. However, when zeolites are treated alkaline as described above, even those with a low SiO ₂ / Al ₂ O ₃ molar ratio show good stability, thus increasing the number of possible regeneration cycles. Consequently, zeolites with an SiO ₂ / Al ₂ O ₃ molar ratio below 100 are also suitable for the present invention. A SiO ₂ / Al ₂ O ₃ molar ratio of from 20 to 500, particularly preferably from 40 to 200, is preferred.

The zeolites which can be used for the invention have, for example an average pore diameter of 0.5 to 1 nm, preferably from 0.5 to 0.6 nm, on. The determination of the pore diameter takes place crystallography.

Of the Catalyst suitable for the invention is, for example of primary crystallites with a mean diameter from 0.01 to 10 μm, preferably 0.05 to 5 μm, built up.

The BET surface area of the catalyst usable for the present invention is, for example, 200 to 600 m ² / g, preferably 250 to 400 m ² / g (determined after DIN 66 131 ), and its pore volume (determined by mercury porosimetry) DIN 66 133 ; Parameter specific total pore volume), for example 0.3 to 0.8 cm ³ / g.

The catalyst may further contain a binder. As a rule, "activated" aluminum hydroxides, silicates, aluminosilicates, etc. are used as binders, in which case any binder known to those skilled in the art may be used, in particular silicate materials, alumina, zirconium compounds, titanium oxide, and mixtures thereof, and materials such as For example, cement, clay, kaolin, flux, silica / alumina, preferred binders are also pseudo-boehmite and silicatic binders such as colloidal silica or fumed silica, more preferably the binder is selected from aluminum or silicon based binders, alumina, alumina hydrate, SiO ₂ -, TiO ₂ - WO ₃ -. or ZrO ₂ compounds a suitable binder may also be a sol, for example, a sol of nanoparticles of Al ₂ O ₃ (e.g., Disperal ^® of Sasol), ZrO ₂ (for example, Zr acetate are preferably Mel Chemicals, NYACOL ^® products). Furthermore, cero xid brine (e.g. B. from Nyacol), silicon dioxide sols (z. B. Köstrosol ^®) and titanium dioxide sols (z. B. life of fixed-Chemie). Solen refers to homogeneous clear solutions containing nanoparticles in the size range of about 2-50 nm. The commercially available sols are usually acetate-stabilized sols or ni Step-stabilized brine (nitric acid).

The Properties of the catalyst can be further modified be by adding the catalyst with catalytically active components is occupied, which influence its catalytic properties or which are themselves catalytically active. Suitable for this For example, metals of the subgroups, in which case the precious metals are particularly preferred. Suitable examples are gold, silver, Rhenium, ruthenium, rhodium, palladium, osmium, iridium and platinum as well as their mixtures and alloys. The catalytically active component is generally in a proportion of 0.01 to 40 wt .-%, based on the overall face of the catalyst, contained in the catalyst. If a noble metal is used as the catalytically active component, this is preferably in a proportion of 0.05 to 2 wt .-% in the catalyst contain.

Of the Content of the catalyst of exchangeable cations, in particular Alkali ions, for example, by treatment with suitable Cation sources, such as ammonium ions, metal ions, oxonium ions or their mixtures are influenced, those contained in the zeolite exchangeable ions, especially alkali ions, are exchanged. The catalyst loaded with the corresponding ions can subsequently be washed and dried. The drying becomes, for example at temperatures of 110 to 130 ° C for a duration carried out from 12 to 16 h. To be in exchange for Ammonium ions to convert the catalyst into an acid activated form, the catalyst can be calcined again, for example Temperatures in the range of 460 to 500 ° C for a duration of 6 to 10 h can be applied. Finally the catalyst can still be ground.

The preferred NH ₄ form of the zeolite is obtained from the Na or H form by treatment with dilute ammonium salt solution, preferably NH ₄ NO ₃ or (NH ₄ ) ₂ SO ₄ solution. For example, 10 to 100 g, preferably 20 to 80 g salt per liter of water is used, wherein the zeolite for 1 to 12 hours, preferably 2 to 4 hours in this solution, for example, with stirring, at a temperature of 20 to 100 ° C, preferred 50 to 80 ° C is maintained. The zeolite content in the solution is for example 10 to 30 wt .-%, preferably 15 to 25 wt .-%.

Of the Catalyst can be used in powder form. Preferably the catalyst for increasing the mechanical stability and processed for better handling but to moldings. For this purpose, the zeolite according to the invention, as above carried out, for example, with or without the addition of binders are pressed to corresponding moldings. The shape However, it can also be done by other methods, for example by extruding. In this case, the powder obtained after addition of a Binder, for example Pseudoboehmit, to moldings shaped. Possible geometries arise depending on the type of used tool. For example, by the Shaping process Hollow cylinder with honeycomb structure be formed. The shaped bodies can subsequently be dried, for example at temperatures of 100 to 130 ° C. Optionally, the shaped bodies can still be calcined in general, temperatures ranging from 400 to 600 ° C can be used.

The Shaping has the advantage that when using the catalyst, For example, in a fixed bed or tubular reactor, the pressure loss compared to catalyst powder reduces the pressure loss which usually results in an increase in yield is possible.

The use according to the invention is directed to the reaction of oxygenates, in particular of alcohols and ethers, to form olefins. As oxygenate, for example, lower (C ₁ -C ₆ ) alcohols, such as. As methanol, ethanol, propanol or butanol, lower (C ₁ -C ₆ ) aldehydes, such as. As formaldehyde, acetaldehyde or propanal, and ethers, such as. For example, dimethyl ether, diethyl ether, methyl tert-butyl ether, tert-amyl methyl ether, ethyl tert-butyl ether or diisopropyl ether, and mixtures thereof may be used. As olefins according to the invention, in particular lower (C ₂ -C ₆ ) olefins are obtained, for example ethylene, propylene, butene, pentene and mixtures thereof. Preferably, the product obtained is propylene.

The Catalytic production of olefins from oxygenates is preferred by reacting a mixture of oxygenate vapor and / or the vapor by splitting off at least one molecule of water from at least two molecules of oxygenate product and water vapor and optionally additionally supplied Water vapor in a tubular reactor on an indirectly cooled Catalyst. Preferably, in the synthesis reactions with oxygenates as educts and water vapor a water / oxygenate molar ratio from 0.5 to 10 before.

In the case of methanol as an oxygenate is generated by cleavage of a molecule of water from two molecules of methanol, first dimethyl ether, which then using the in the context of present invention to olefins, for example, ethylene (C2 =) or propylene (C3 =), is converted.

embodiments

Example 1: Preparation of a modified zeolites

According to the EP 0 406 474 For example, a zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of 40 and an average primary crystallite size of 2 μm was prepared. The resulting synthesis mixture (pH about 11), comprising zeolite, unreacted SiO ₂ , sodium hydroxide and salts, was filtered off and calcined without any washing at 550 ° C. for 12 hours in a low bed (about 5 cm bed height). The resulting zeolite was then slurried in a solution of NH ₄ NO ₃ in demineralised water and stirred until the residual sodium level was below 200 ppm. Subsequently, the zeolite was filtered off and further processed as described below.

Example 2: Production of molded pieces

The zeolite from Example 1 was for 15 min in a kneader with commercial alumina (alternatively alumina hydrate) as a binder with the addition of demineralized water and an SiO ₂ compound between 10 and 90 wt .-% (alternatively TiO ₂ or ZrO) mixed and to processed a plastic mass. The mass was then extruded into moldings (extrudates, granules and dripping balls).

The Moldings were air-dried at 120 ° C during Dried for 16 h and then calcined in air.

Subsequently, the moldings were in a flow reactor under the conditions: temperature 450 ° C Methanol Feed 1 kg / kg of catalyst per hour Water Feed 2 kg / kg of catalyst per hour

The measured propylene selectivity (propylene selectivity = Proportion of propylene / total C3 fraction) was 98%.

Comparative Example 1

One as prepared under Example 1 to 2 catalyst, but without Calcination of the zeolite powder with adherent mother liquor supplied a propylene selectivity of 91% after 100 hours.

Example 3:

A prepared with tetrapropylene bromide as an organic template zeolite (MFI) also with a SiO ₂ / Al ₂ O ₃ ratio of 40 and a crystallite size of 0.1 microns was filtered, dried and calcined for template burn-out at 500 ° C for 12 h. Thereafter, the zeolite was slurried in water (20 wt .-% solids), the pH of the suspension with sodium hydroxide solution to 11, and the suspension was stirred at 50 ° C for 2 hours. The mixture was then filtered and alkaline calcined without further washing, as in Examples 1 and 2, and after ion exchange to reduce the Na ₂ O content to values below 200 ppm (compare the ion exchange with filtration and renewed slurrying in NH ₄ NO ₃ several times necessary) further processed to a catalyst. The propylene selectivity after 100 hours was 96%.

Comparative Example 2:

One Catalyst was analogous to Example 3, but without calcination of the zeolite powder with adhering mother liquor. The Propylene selectivity after 100 hours was 90%.

Example 4:

The zeolite of Example 1 became an ion by a method known in the art exchanged. For this purpose, the zeolite was suspended in a solution of NH ₄ NO ₃ in demineralized water and stirred for 2 h. The solid was separated by filtration and the filter cake was washed four times with demineralised water. Subsequently, the washed filter cake was reslurried in a fresh solution of NH ₄ NO ₃ in demineralised water and stirred for 2 h. The solid was again separated by filtration and washed with demineralized water until the conductivity of the wash water had dropped below 100 μS / cm. The filter cake was then dried at 120 ° C for 14 h in air and then calcined in air. Subsequently, the catalyst was slurried in a sodium hydroxide solution at pH 11 at 100 ° C and the slurry was filtered after one hour without washing and then calcined as in Examples 1 and 2 and made into a catalyst. The propylene selectivity after 100 hours was 97%.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0448000 A1 [0003]
• US 4499327 [0006]
• US 6518475 [0006]
• US 3894104 [0006]
• - DE 1020050520162 [0008]
• - DE 102006037314 [0008]
• - EP 0443539 [0014]
• EP 0406474 [0039]

Cited non-patent literature

• - DIN 66 131 [0029]
• - DIN 66 133 [0029]

Claims (19)

Use of a catalyst comprising aluminosilicates, subjected to a thermal treatment in the alkaline state to convert oxygenates to olefins. Use according to claim 1, characterized that the catalyst before the thermal treatment of an alkaline Treatment at a pH of 9 to 14 and a temperature of 20 to 100 ° C over a period of 0.1 to 100 Is subjected to hours. Use according to claim 1 or 2, characterized that the thermal treatment of the catalyst by calcination at 250 to 650 ° C takes place. Use according to one of claims 1 to 3, characterized in that the catalyst is aluminosilicate, preferably crystalline aluminosilicate exists. Use according to one of claims 1 to 4, characterized in that the thermal treatment at a Filter humidified aluminosilicate is made. Use according to one of claims 1 to 5, characterized in that the catalyst has a starting selectivity to olefins of more than 95%. Use according to one of claims 1 to 6, characterized in that the olefin is a C2 or C3 olefin is. Use according to one of claims 1 to 7, characterized in that the catalyst has a pore size from 0.5 to 1 nm and that does not form-selective active sites are deactivated on the crystallite surface. Use according to one of claims 1 to 8, characterized in that the catalyst has a SiO ₂ / Al ₂ O ₃ molar ratio of 20 to 500. Use according to one of claims 1 to 9, characterized in that the catalyst has a Primärkristallitgröße from 0.01 to 10 microns. Use according to one of claims 1 to 10, characterized in that the aluminosilicate is a zeolite. Use according to one of claims 1 to 11, wherein the catalyst further contains a binder. Use according to claim 12, wherein the binder is selected from silicate materials, alumina, zirconium compounds, titanium oxide, and mixtures thereof, cement, clay, kaolin, flux, silica / alumina, pseudoboehmite, silicate binders or colloidal silica, sols of nanoparticles of Al ₂ O. ₃ , ZrO ₂ , ceria sols, silica sols or titania sols. Use according to one of claims 1 to 13, characterized in that the aluminosilicate ion exchange is subjected. Use according to one of claims 1 to 14, characterized in that the aluminosilicate a molding process is subjected. Use according to claim 15, characterized that the molding process is an extrusion. Use according to one of claims 1 to 16, characterized in that the oxygenate methanol and / or Dimethyl ether and the olefin is propylene and / or ethylene. Process for converting oxygenates to olefins, characterized in that for the reaction a catalyst according to any one of claims 1 to 17 is used. A method according to claim 18, characterized in that the oxygenate methanol and / or dime methyl ether and the olefin is propylene and / or ethylene.