DD253611A1 - PREPARATION OF LOW OLEFINS FROM METHANOL AND / OR DIMETHYL ETHER - Google Patents

Abstract

The invention is suitable for the preparation of lower olefins by reacting methanol and / or dimethyl ether in a heterogeneous catalytic process. According to the invention, the starting material is reacted on a catalyst containing the Mn 2 substantially as a mixture of the hydroxides of aluminum and manganese on a mechanically activated zeolite whose molar ratio SiO 2: Al 2 O 3100 to 600.

Description

dinnm normalized intensity intensity 1.161 ± 0.025 weak strongly 1,138 ± 0.025 medium strong strongly 1,116 ± 0.025 very strong strongly 1.023 ± 0.025 medium strong medium 1.001 ± 0.02 strongly weak 0.993 ± 0.02 strongly medium 0.971 ± 0.02 medium strong medium 0.386 ± 0.005 very strong strongly 0.382 ± 0.005 ' very strong strongly 0.376 ± 0.005 medium strong weak 0.372 ± 0.005 medium strong weak 0.201 ± 0.003 weak weak 0.199 ± 0.003 weak medium and its IR absorption spectrum follower strongly Absorption / cm ¹ 448 ± 3 545 ± 3 555 ± 3 (shoulder) 580 ± 3 (shoulder) 625 ± 3 785 ± 3 (shoulder) 795 ± 3 · 1070 ± 30 (wide) 1 225 ± 4 1 625 ± 5 2 845 ± 5 2915 ± 5 3 445 ± 7 3 670 ± 7

respectively.

3. The method according to claim 1 and 2, characterized in that Pentasilzeolithe bedenderen molar ratio of SiO ₂ : Al ₂ O _{3 is} 200 to 500. -

4. The method according to claim 1 to 3, characterized in that catalysts are used, which have been alkalized after their deformation by treatment with calcium hydroxide-containing solutions at pH> 9.

5. The method according to claim 1 to 4, characterized in that catalysts are used, which after the alkalization and a 2 to 4 hours of annealing in air at 800 K in 10% aqueous suspension has a pH> 8.5.

Field of application of the invention

The invention is suitable for the preparation of lower olefins by reacting methanol and / or dimethyl ether in a heterogeneous catalytic process.

Characteristic of the known state of the art

For the preparation of lower olefins from methanol and / or dimethyl ether, catalysts based on pentasil zeolites of various modifications have been proposed. The main disadvantage of the reaction, namely the insufficient selectivity, is being tried in various ways to counteract. Procedural z. B. such conditions that minimize the residence time of the zeolite, such as the dilution of the raw material with, for example, steam (DE-PS 2827385) or the leadership of the reaction in the partial sales area (EP 60103). Also proposed are reaction selections with electron donors (EP 75203) or aldehydes (US Pat. No. 4,374,295). In such cases, considerable additional costs arise due to the low specific resource burden or the additional effort for the selectivators. For this reason, methods have been proposed which have a selectivation of the catalyst to the content, such. As the application of Mn ²⁺ -exchanged zeolites (DE-PS 2755229) or the use of pentasil zeolites with high molar ratio of SiO ₂ : Al ₂ O ₃ (module) (DE-PS 2935863). However, the relatively short service lives of the catalysts and the olefin selectivity which varies greatly with the length of the operating period continue to be disadvantageous. The use of alkaline-exchanged zeolites resulted in a fundamental improvement in the selectivity-time behavior with already high initial selectivity for olefins; the achievable service lives are nevertheless still too low for technical purposes, and the strong pressure dependence of the selectivity considerably degrades the result of the industrial application.

Object of the invention

The aim of the invention is a process for the preparation of lower olefins from methanol and / or dimethyl ether, which enables high olefin yields and long process run times under industrially useful pressure ratios.

Explanation of the essence of the invention

It was therefore the task of developing a method which allows methanol and / or dimethyl ether at elevated process pressure with high selectivity already before the beginning of the reaction to convert to lower olefins, wherein the catalyst has a relatively low deactivation rate.

The object was achieved in that according to the invention methanol and / or dimethyl ether is reacted together with an accompanying gas to a catalyst which contains the Mn ²⁺ substantially as a mixture of the hydroxides of aluminum and manganese precipitated on a mechanically activated zeolite whose molar ratio SiO ₂ : Al ₂ O ₃ = 100 to 600 carries. Advantageously, zeolites are used whose X-ray diffraction pattern has the following reflexes

dinnm norm. intensity 1.161 ± 0.025 weak 1,138 ± 0.025 medium strong 1,116 ± 0.025 very strong 1.023 ± 0.025 medium strong 1.001 ± 0.02 strongly 1.001 ± 0.02 strongly 0.993 ± 0.02 strongly 0.971 ± 0.02 medium strong 0.386 ± 0.005 very strong 0.382 ± 0.005 very strong 0.376 ± 0.005 medium strong 0.372 ± 0.005 medium strong 0.201 ± 0.003 weak 0.199 ± 0.003 weak and desser IR absorptive following spectrum Absorption / crrT ¹ intensity 448 ± 3 strongly 545 + 3 strongly 555 ± 3 (shoulder) strongly 580 ± 3 (shoulder) medium strong 625 ± 3 weak 785 ± 3 (shoulder) medium 795 ± 3 medium 1070 ± 30 (wide) strongly 1225 + 4 strongly 1 625 ± 5 weak 2 845 ± 5 weak 2915 ± 5 weak 3 445 ± 7 medium 3 670 ± 7 strongly respectively.

In a particularly favorable embodiment of the process, the zeolite should have a molar ratio SiO ₂ : Al ₂ O ₃ of 200 to 500.

It is furthermore advantageous if the shaped catalyst is alkalized with Ca (OH) ₂ -containing solutions at pH values> 9, wherein once again clear advantages of the process are observed when the alkalized catalysts after annealing in air at ca. 800 K for 2 to 4h, in 10% aqueous suspension have a pH of s 8.5. Surprisingly, it has been found that a common precipitation of Mn ²⁺ and Al ³⁺ hydroxides on the zeolite can achieve significantly better yields of lower olefins, in particular at the beginning of the process period, than with the commonly used Mn ²⁺ impurities on zeolite or catalyst , wherein the effect according to the invention is particularly pronounced with zeolite with modules> 100. It was equally surprising that vibratory milling of the zeolite can significantly extend the process period when it occurs with a residence time of about 5 to 15 minutes prior to mixing the zeolite with the binder, although electron microscopy and X-ray analysis show no reduction in zeolite crystals.

Both effects are particularly noticeable in zeolites which have the characteristic X-ray diffraction pattern according to the invention, wherein a subsequent alkalization of the finished catalyst with calcium hydride solutions further reduces the accumulation of undesired liquid hydrocarbons in this process.

embodiment

Step Example! 1 (catalyst A, comparative method)

Using a 28% silica sol, a 2.5 molar triethyl (2) hydroxyethylammoniumcarbonatlösung and a 2 η sodium hydroxide, in the previously required amount of alumina hydrate had been dissolved, a zeolite synthesis mixture is prepared in which the ratio Si: N: Na Al = 7.9: 1: 1.5: 0.043.

This synthesis mixture is crystallized in autoclave under autogenous pressure for 80 h at 433 K.

The zeolite obtained after aspiration, washing and drying shows a modulus of 348 (chemically determined) and shows the characteristic X-ray diffraction pattern according to the invention.

The synthetic zeolite is further processed into the catalyst in a known manner-by using eLnew on the preparation

organic compound is annealed at about 850K for 4 to 5 hours, then ion exchanged using a 1 η NH ₄ NO 3 solution, and then, with the addition of 30% Al 2 O 3 (calculated and based on anhydrous material) in the form of a precipitate, shaped into extrudates containing a have a round cross section with a diameter of about 2 mm. The calcined extrudates are impregnated with a Mn (NO3> 2 solution so that 3Ma% Mn is applied to the anhydrous zeolite, and the catalyst is completed after drying and recomination for about 2 hours at 720-770K ,

Example 2 (Catalyst B, process according to the invention)

The dried synthesis zeolite from Example 1 is first ground in a vibration mill for 5 to 15 minutes and then stirred into a solution containing Mn (NO ₃ ) ₂ and Al (NO ₃ > 3 in such an amount that based on the anhydrous zeolite, 3Ma .-% Mn and 10Ma .-% Al2O3 result, wherein the solid-liquid ratio is 1: 3 to 1: 5. The suspension is heated to 340 to 360K with stirring and at this temperature with aqueous ammonia solution to a pH Value of 7 to 8, wherein a mixture of the hydroxides of Mn and Al is precipitated on the zeolite.

To complete the reaction, stirring is continued for 1 to 2 h at this temperature and then the solid is separated from the mother liquor, washed with salt-free water and optionally after drying with about 20Ma .-%, based on the zeolite and calculated as anhydrous material to Precipitated boehmite mixed, plasticized and shaped as in Example 1 to cylindrical extruded granules, dried and calcined.

Example 3 (Catalyst C, process according to the invention)

The catalyst B obtained in Example 2 is treated with a liquid-solid ratio of about 2: 1 with a 0.5 molar Ca (NO ₃ ) ₂ solution, the pH of which was previously adjusted to 9 by the addition of Ca (OH) ₂ was set and held at this value, wherein the solution flows around the catalyst moldings at about 340K for 2 h or flows through. Thereafter, the solution is separated, the catalyst washed with an amount of salt-free water, as corresponds to its bulk volume, then dried and calcined at about 770K for 2 h in air.

The ground catalyst shows in aqueous suspension with 10Ma .-% solids a pH of 8.5.

Example 4 (catalyst D, comparative method)

A silicon-rich zeolite of the type LZ40 with a molar ratio of SiO ₂ : Al ₂ O ₃ = 57 is exchanged in a manner known per se with Mn ²⁺ ions by incubating for 2 h at about 365 K with an aqueous Mn (NO ₃ 2) solution with stirring, which contains 0.5 mol / l Mn (NO ₃ J ₂ , the ratio solid: liquid being about 1: 5. After the ion exchange has ended, the zeolite is separated off from the mother liquor, washed salt-free The ion-exchanged zeolite is plasticized in a mass ratio of 70:30 (based on the anhydrous material) with a precipitation boehmite together with the addition of salt-free water, optionally with the addition of a plasticizer, such as polyvinyl alcohol, and extrudates with a screw extruder Diameters of about 2 mm are deformed, the moldings are dried at about 390K and solidified by air for about 5 hours at about 800K in air.

The catalyst moldings are then treated with a 0.5 molar Ca (NO ₃ ) 2 solution which is brought to pH 9.5 by addition of Ca (OH) ₂ and held for 2 hours at about 350 ° C a liquid: solids ratio of about 2 to be flowed around. The treated briquettes are separated and washed with a volume of salt-free water equal to the catalyst volume. After re-drying at 390K with subsequent annealing for 2h at about 800K in air, a 10% aqueous slurry of the milled catalyst shows a pH of 9.1.

-4- Üb3 ΟΤΙ

Example 5 (catalyst E, process according to the invention)

The same zeolite as in Example 4 is treated as in Example 2, except that the short-term vibration milling takes place only after precipitation of the Mn-Al hydroxide mixture onto the zeolite but before mixing with the precipitating boehmite acting as binder.

The calcined catalyst moldings are alkalized as shown in Example 4, with the finished catalyst having a pH of 9.3 as a 10% suspension.

Example 6

The catalysts A to E were catalytically tested under the following conditions

Pressure: 1.0MPa - Accompanying gas: water vapor

Load: 1.0g / g-h methane water: 1: 1 g / g

The methanol was first reacted in a prereactor to γ-ΑΙ ₂ Ο ₃ at 620 K largely to dimethyl ether and water and then passed the resulting gas mixture under the catalyst. The operating period is completed when the conversion of methanol to hydrocarbons has dropped to 95%

 Table 1 compares the catalytic results:

Table 1

Catalyst A B C D E

Operating period in h 256

Temperature in K 620 620

C _{2 to} C ₄ olefins in mass% 25 32

Liquid hydrocarbons 51 42 substancesin% by mass

The results are always at the beginning and end of a period of operation.

As Table 1 shows, the inventive method results in significantly extended periods of operation and this at

markedly improved olefin selectivities.

388 468 168 336 620 620 660 690 620 620 655 670 31 38 43 46 33 34 38 40 44 35 38 36 46 43 , 39 37

Claims (2)

1. Production of lower olefins from methanol and / or dimethyl ether of manganese-containing catalysts of pentasil zeolite type with Al ₂ O ₃ as a binder, at elevated temperature and a process pressure of 0.5 to 1.5 MPa, characterized in that the starting material on a catalyst is reacted, which contains the Mn ²⁺ substantially as a mixture of the hydroxides of aluminum and manganese on a mechanically activated zeolite whose molar ratio SiO ₂ : Al ₂ O ₃ = 100 to 600. 2. The method according to claim 1, characterized in that zeolites of the pentasil type are used, the X-ray diffraction pattern of the following reflexes