DD251746A1 - PROCESS FOR PREPARING AROMATIC HYDROCARBONS - Google Patents

Abstract

The invention relates to a process for the preparation of aromatic hydrocarbons by heterogeneously catalyzed conversion of lower hydrocarbons at elevated temperatures and atmospheric pressure or slightly elevated pressure. The aim is to design a simple and technically applicable process in which the selective conversion of preferably C2 to C5 hydrocarbons to aromatic hydrocarbons, notably benzene, toluene and xylenes, to zeolite-containing multi-component catalysts with very good activity-time behavior and remarkable Regenerationsstabilitaet , According to the invention, this is achieved by using catalysts for the aromatization, in which metals of groups III a and / or III b and optionally VI b of the PSE are exchanged in certain atomic ratios.

Description

Field of application of the invention,

The invention relates to a process for the preparation of aromatic hydrocarbons, in particular of benzene, toluene and xylenes, by catalytic conversion of short-chain hydrocarbons.

Characteristic of the known technical solutions

The increasing processing of high-boiling hydrocarbon fractions and petroleum residues by means of preferably hydro-splitting processes leads, inter alia, to an increased amount of short-chain hydrocarbons whose material use is required. The catalytic aromatization of these lower hydrocarbons can be a promising alternative. So far, the implementation of η-butane to noble metal-containing catalysts has been proposed, but at the high temperatures required for the aromatics a greatly increased methane and carbon formation takes place, which causes a rapid catalyst deactivation (J. Catal. 17 [1970] 323). More recently, amorphous and crystalline aluminosilicates, predominantly after exchange of metal ions, have been proposed as catalysts for the aromatization of short-chain hydrocarbons. Thus, the conversion of propane and butanes to silicates is claimed according to DE-OS 3009495 and DE-OS 3009497, which contain up to 20Ma .-% MetaIlionen. At elevated temperatures and slightly elevated pressure, selectivities of aromatics formation should be possible up to a maximum of 40%. According to US Pat. No. 4,157,356, the aromatization of C _{3 to} C 6 hydrocarbons on metal-containing silicates is proposed, wherein isobutane is formed up to a maximum of 22% by mass of aromatics.

According to their discovery (US Pat. No. 3,702,886) and industrial production, the zeolites of the ZSM-5 type in the H form or after incorporation of metal ions for hydrocarbon conversion are also recommended. No. 3,775,501 discloses the aromatization of C ₃ to C ₆ olefins and paraffins on catalysts of the type H-ZSM-s, Pt-ZSM-5, Au-ZSM-5 and U-ZSM-5 in the presence of Carrier gases are described, however, only aromaticity yields of up to 30 mass% are achieved in paraffin conversion. More commonly claimed is the use of zeolites of the ZSM type which, after impregnation or ion exchange, contain Group III metals of the PSE.

According to US Pat. No. 4,350,835, ZSM types with a modulus> 30 and a constraint index of up to 12, with metal contents up to 5% by mass, are suitable for the aromatization of short-chain paraffins. At a very high temperature of ~ 580 ° C favoring coke formation, with an ethane conversion of 21% only a flavor selectivity of 56% is achieved. With EP-PS 107875 and 107876 also metal-containing zeolites of the ZSM type are proposed, which cause acceptable aromatics yields but with high methane formation and limited catalyst life. In summary, the disadvantages of the previously proposed methods for the catalytic aromatization of short-chain hydrocarbons can be characterized as follows:

Moderate activity and selectivity of the formation of aromatic hydrocarbons,

- insufficient activity-time behavior of the catalysts, due to excessive coke formation,

Insufficient regeneration stability of the catalysts recommended for use,

- Insufficient mechanical stability of the catalysts, so that use in moving bed processes is not possible.

Object of the invention

It is an object of the invention to provide a simple and technically applicable process in which the selective conversion of short-chain hydrocarbons to aromatic hydrocarbons on novel zeolite-containing multi-component catalysts with very good activity-time behavior and remarkable regeneration stability succeeds.

Explanation of the essence of the invention

The object is achieved by a process for the preparation of aromatic hydrocarbons from short-chain hydrocarbons on fixed or moving, extruded or spherical catalysts at elevated temperatures, normal pressure or slightly elevated pressure and optionally in the presence of hydrogen and / or inert gases, by a catalyst according to the invention is used, the zeolite of the ZSM-5 type with a module greater than. 20, metals and / or metal compounds of groups III a and / or III b alone or in combination with metals and / or metal compounds of group VIb of PSE in a total concentration up to 15Ma .-%, based on the weight of the zeolite, and silica and / or alumina and / or clays in an amount of 1 to 90% by mass, based on the total weight of the catalyst.

An essential feature of the invention is that the preferred representatives of the group purple lanthanum, group III b gallium and group Vl b chromium in an amount ranging from 0.001 to 5.0 Ma .-% per metal and based on the amount of zeolite for use to be brought. Surprisingly, it has now been found that by the combined use of these metals synergistic effects in terms of increasing the aromatization activity and selectivity and the regeneration stability occurred. In this case, the combinations lanthanum / chromium and gallium / chromium, in each case in the atomic ratio of 100: 1 to 1: 1 have been used, proven in a special way, in addition to the advantages already shown, the excellent activity-time stability of the catalysts thus prepared a particular advantage is. A feature essential to the invention is the use of a zeolite of the ZSM-5 type with a modulus in the range of 20 to 100. The already characterized as essential for the full development of the catalytic activity and selectivity metals can both by impregnation with aqueous metal salt solutions and preferably by Ion exchange are introduced into the zeolite.

Another characteristic according to the invention consists in the deformation of the metal-exchanged zeolites with silica sol and / or alumina and / or clay minerals, which in particular causes the mechanical stability required for industrial use.

According to the invention, the catalysts in the aromatization of paraffins and olefins and mixtures of their full activity and selectivity in the temperature range of 380 to 580 ⁰ C, a load of 0.3 to 5.0 kg of raw material per kg of catalyst and hour and a pressure of 0.01 to 1.0 MPa, optionally with the addition of hydrogen and / or inert gases. It is essential for the purposes of the invention that all components contained in the catalyst contribute effectively to the desired aromatization.

Another important advantage of the method characterized according to the invention is the easy-to-carry out and effective regeneration of the activity-reduced catalysts by coke formation. It is surprising that the catalysts claimed according to the invention have a virtually unchanged aromatization activity and selectivity even after a large number of regeneration cycles.

embodiments example 1

The zeolites of the ZSM-5 type used below are prepared according to DD-WP 205674 by reacting sodium silicic acid sol, sodium aluminate, sodium hydroxide solution and water with the addition of seed crystals. Thus, a ZSM-5 type zeolite having the following properties can be obtained:

Molar ratio of SiO ₂ : Al ₂ O ₃ = 25 (Module) water vapor adsorption = 5.2% at 20 ⁰ C and 0.08 kPa Benzenadsorption = 7.2% at 2O ⁰ C and 2.4 kPa

500 g of the present in the Na form zeolites are converted by treatment with 510.5 η hydrochloric acid at 2O ⁰ C with stirring and over a period of 8 hours in the Η-form.

After filtration, washing and drying, the powdered zeolite is converted in the mixing granulator by spraying 300 ml of 15% silica sol solution into granules with a diameter of 1 to 3 mm. The granular, 10Ma .-% free silica catalyst containing is dried for 6 hours at 120 ⁰ C and 4 hours in the air stream at 48O ⁰ C activated.

Example 2

30 g of the catalyst according to Example 1 are placed in a quartz glass reactor, as described in Chem. Techn. 34 (7) (1982) 367, heated to 500 ⁰ C over a period of 2 hours in a nitrogen stream, for 1 hour at this Leave temperature and then set the desired test temperature. The determination of the gaseous and liquid reaction product is carried out by gas chromatographic analysis. Table 1 below contains the results obtained in the reaction of short-chain paraffins on this H-ZSM-5-containing catalyst.

After completion of the respective reaction period is heated to 400 to 450 ⁰ C in a stream of nitrogen and initiated by metering of oxygen, the regeneration by combustion of the carbonaceous deposits, wherein a temperature of 550 ⁰ C is not exceeded. The amount of carbon is determined by absorption of the carbon dioxide formed in sodium hydroxide solution and subsequent dimensional analysis.

Example 3

Binder-free powdered zeolite according to Example 1 is introduced with stirring into an aqueous 0.1 η gallium-l chloride solution and left at 25 ⁰ C with stirring for 8 hours. It is then washed free of chloride and dried at 120 ⁰ C for 4 hours. The zeolite containing 0.85% by weight of gallium is shaped in accordance with Example 1 in the mixing granulator by spraying on silica sol solution. The gallium content in the finished catalyst containing 90% by mass of zeolite and 10% by mass of SiO ₂ is 0.77% by mass. 30 g of the thus prepared catalyst are incorporated into the quartz glass reactor and treated according to Example 2. The results obtained in the conversion of short-chain paraffins are summarized in Table 1.

Example 4

Galliumhaitiger binder-free zeolite according to Example 3 is added to an aqueous 0.1 η chromium-lll-nitrate solution and left at 6O ⁰ C with stirring for 10 hours. It is then washed thoroughly and dried at 120 ⁰ C for 4 hours. The zeolite containing 0.85% by weight of gallium and 0.04% by weight of chromium is shaped in accordance with Example 1 in the mixing granulator by spraying on silica sol solution. The finished catalyst consisting of 90 mass% zeolite and 10 mass% SiO ₂ contains 0.77 mass% gallium and 0.035 mass% chromium. The preparation and performance of the catalytic tests are carried out according to Example 2. Table 2 contains the results obtained in the paraffin conversion. The values of Table 3 characterize the activity-time behavior of the catalyst. The results in Table 4 reflect the regeneration stability. Table 5 contains the results obtained in the reaction of paraffin / olefin blends. The mass ratio paraffin: olefin was 10: 1.

Example 5

Binder-free zeolite according to Example 1 is added with stirring in an aqueous 0.1 η lanthanum-lll-chloride solution and left at 25 ⁰ C with stirring for 8 hours. It is then washed thoroughly and dried at 120 ° C for 4 hours. The lanthanum-containing zeolite is then added to an aqueous 0.1 η chromium-lll-nitrate solution and left at 60 ⁰ C with stirring for 10 hours. It is then washed thoroughly and dried at 120 ⁰ C for 4 hours.

The 1.2Ma .-% lanthanum and 0.04Ma .-% chromium-containing zeolite is shaped according to Example 1 in the mixing granulator by spraying silica sol solution. The finished catalyst consisting of 90 mass% zeolite and 10 mass% SiO ₂ contains 1.08 mass% lanthanum and 0.035 mass% chromium. The catalytic tests are carried out according to Example 2. Table 6 reflects the results obtained in the conversion of short-chain hydrocarbons.

Table 1 535 propane 500 n-butane 500 500 isobutane 500 feedstock A B A B 500 B Reaction temperature in ° C A type of catalytic converter 12.9 23.5 21.8 36.1 45.8 Yield in% by weight 86.6 75.7 77.5 63.0 25.3 53.2 liquid product 0.5 0.8 0.7 0.9 74.1 1.0 Gaseous product 1.0 2.7 1.0 3.4 0.6 4.8 carbon 21.7 16.9 13.7 15.0 1.4 17.0 hydrogen 4.4 1.5 2.3 1.6 16.1 • 0.8 methane 18.4 13.8 17.3 18.3 2.7 16.0 ethene 4.5 1.3 • 2.4 1.2 11.8 0.8 Ethan 33.6 38.4 36.2 21.5 3.4 12.8 propene 1.0 0.2 0.9 0.1 32.8 0.1 propane 2.0 0.9 3.7 1.9 1.1 0.9 butenes 12.5 23.0 20.9 35.5 4.8 45.1 Butane 4.6 6.4 5.4 10.1 24.4 12.0 Σ aromatics 5.3 8.9 8.6 14.6 6.6 18.8 benzene 0.2 0.3 0.4 0.4 10.1 0.4 toluene 0.4 0.8 0.9 1.3 0.5 1.7 ethylbenzene 0.9 2.0 2.1 3.0 1.0 3.8 p-Xylene 0.4 0.7. 1.0 1.3 2.3 1.8 m-xylene 0.2 0.6 0.6 • 0.6 1.1 0.8 o-xylene 0.7 3.3 1.9 4.2 0.7 5.8 ICG aromatics 2.1 > Cg-aromatics

Load: 1.0g / g h

A: H-ZSM-5 type according to Example 1 and 2 B: Ga-ZSM-5 type according to Example 3

Table 2 feedstock propane reaction temperature 500 in ⁰ C Yield in% by weight liquid product 25.0 Gaseous product 74.3 carbon 0.7 hydrogen 2.8 methane 16.1 ethene 1.6 Ethan 13.3 propene 1.4 propane 38.0 butenes 0.2 Butane 0.9 X aromatics   24.5 benzene 7.3 toluene 9.6 ethylbenzene 0.3 p-Xylene 0.8 m-xylene 2.1 o-xylene 0.8 Σ Cg aromatics 0.5 > C ₉ aromatics 3.1

n-butane 500

37.1

62.0

0.9

3.5

14.6

1.6

17.9

1.2

21.4

0.1

1.7

36.6

10.8

15.1

0.4

1.4

3.1

1.3

0.7

3.8

Isobutane 500

46.5

52.6

0.9

5.1

16.6

1.4

12.7

1.0

14.7

0.1

1.0

46.0

12.5

19.2

0.4

1.8

4.0

1.8

0.7

5.6

Load: 1.0 g / g · h Catalyst: Ga / Cr-ZSM-5 type according to Example 4

Trial time in hours 1. Yield in% by weight liquid product 46.6 Gaseous product 52.7 carbon 0.7 hydrogen 5.2 methane 16.6 ethene 1.4 Ethan 12.7 propene 1.0 propane 14.7 butenes 0.1 Butane   1.0 ! aromatics 46.0 benzene 12.5 toluene 19.2 ethylbenzene 0.4 p-Xylene 1.8 m-xylene 4.0 o-xylene 1.8 Σ Cg aromatics 0.7. > Cg aromatics 5.6

Table 3: conversion of isobutane at 500 ⁰ C and 1.0 g / g · h

3. 6.

48.2 49.9

51.2 49.6

0.6 0.5

5.0 4.8 15.7 14.8

1.4 1.4

12,4 11,9

1.1 1.2

14.4 14.2 0.2 0.2

1.0 1.1 47.7 49.5 13.2 13.8

20.2 20.9 0.4 0.4 1.9 2.1

4.2 4.5 1.8 1.9 0.7 0.7

5.3 5.2

Catalyst: Ga / Cr-ZSM-5 type according to Example 4

Table 4: isobutane at 500 ⁰ C and 1.0 g / g · h

15. 33.

45.5 44.9 53.7 54.4

0.8 0.7

5.1 5.2 16.4 16.1

1.4 1.3

12.3 12.0 0.9 0.9

16.4 17.5 0.1 0.1 1.1 1.3

45.0 44.4

12.2 12.0

18.7 18.5

0.4 0.4

1.8 1.8

4.0 3.9

1,7 '1,7

0.7 0.7

5.5 5.4

Catalyst: Ga / CR-ZSM-5 type according to Example 4

Number of reaction 1. regeneration cycles Yield in% by weight liquid product 46.3 Gaseous product 52.8 carbon 0.9 hydrogen 5.1 methane 16.7 ethene 1.4 Ethan 12.8 Propene · 1.0 propane 14.7 butenes 0.1 Butane 1.0 Σ aromatics 45.8 benzene 12.4 toluene 19.1 ethylbenzene 0.4 p-Xylene 1.8 m-xylene 4.0 o-xylene 1.8 Σ C ₉ aromatics 0.7 > Cg aromatics 5.6

Table 5 feedstock Propane-propene mixture Isobutane-isobutene mixture Reaction temperature in ⁰ C 502 497 Load in g / g · h 1.0 1.0 Yield in% by weight liquid product 28.4 50.1 Gaseous product 70.7 48.9 carbon 0.9 1.0 hydrogen 2.9 4.8 methane 15.9 15.8 ethene 1.3 0.9 Ethan 12.5 12.4 propene 0.9 0.8 propane 36.1 13.1 butenes 0.1 0.1 Butane 1.0 1.0 Σ aromatics 27.9 49.6 benzene 8.0 12.8 toluene 10.3 20,6 t> ethylbenzene 0.3 0.4 p-Xylene 1.1 2.0 m-xylene 2.4 4.4 o-xylene 1.1 1.9 XCG-aromatics 0.7 0.9 > Co-aromatics 4.0 5.9

Catalyst: Ga / Cr-ZSM-5 type according to Example 4

Table 6

feedstock propane n-Bu Reaction temperature in ⁰ C Yield in% by weight liquid product 24.7 • 36.7 Gaseous product 74.5 62.4 carbon 0.8 0.9 hydrogen 2.8 3.5 methane 16.3 14.8 ethene 1.5 1.5 Ethan 13.4 18.2 propene 1.3 1.2 propane 38.1 21.2 butenes 0.1 0.2 Butane 1.0 1.8 Σ aromatics 24.2 36.2 benzene 7.1 10.6 toluene 9.5 14.9 ethylbenzene 0.3 0.4 p-Xylene 0.8 1.3 m-xylene 2.0 3.0 o-xylene 0.8 1.3 Σ Cg aromatics 0.5 0.7 > Cg aromatics 3.2 4.0

isobutane

45.8

53.2 1.0 5.0

16.9 0.8

15.9 0.8 12.7

<0.1 1.0 45.2

12.1

18.7 0.4 1.7 4.0 1.8 0.7 5.8

Load: 1.0g / g h

Catalyst: La / Cr-ZSM-5 type according to Example 5

Claims (11)

1. A process for the preparation of aromatic hydrocarbons from short-chain hydrocarbons on fixed or moving, extruded or spherical catalysts at elevated temperatures, normal pressure or slightly elevated pressure and optionally in the presence of hydrogen and / or inert gases, characterized in that a catalyst is used, zeolites of the ZSM-5 type with a modulus greater than 20, metals and / or metal compounds of groups III a and / or III b and optionally IVb of the PSE in a total concentration up to 15 mass%, based on the weight of the zeolite , and silica and / or alumina and / or clays in an amount of 1 to 90% by mass, based on the total weight of the catalyst. 2. The method according to item 1, characterized in that as a representative of the group purple lanthanum in an amount of 0.01 to 5.0 wt .-%, based on the amount of zeolite, is used. 3. The method according to item 1 and 2, characterized in that as a representative of group III b gallium in an amount of 0.01 to 5.0 mass%, based on the amount of zeolite is used. 4. The method according to item 1 to 3, characterized in that is used as a representative of the group VIb chromium in an amount of 0.001 to 5.0 Ma .-%, based on the amount of zeolite. 5. The method according to item 1 to 4, characterized in that lanthanum and chromium in an atomic ratio of 100: 1 to 1: 1 are used. 6. The method according to item 1 to 5, characterized in that gallium and chromium are used in an atomic ratio of 100: 1 to 1: 1. 7. The method according to item 1 to 6, characterized in that a zeolite of ZSM-5 type is used with a modulus of 20 to 100. 8. The method according to item 1 to 7, characterized in that the proportion of the metal-containing zeolite in the total amount of catalyst between 10 and 99Ma .-% and the respective difference is compensated by alumina and / or silica and / or clays. 9. The method according to item 1 to 8, characterized in that the conversion of the short-chain hydrocarbons at temperatures of 380 to 580 ⁰ C, a load of 0.3 to 5.0 kg of raw material per kg of catalyst and hour and a pressure of 0.01 to 1.0MPa is performed. 10. The method according to item 1 to 9, characterized in that the conversion of the short-chain hydrocarbons in the presence of hydrogen and / or inert gases at a molar ratio of hydrocarbon to gas between 1: 1 and 100: 1 takes place. 11. The method according to item 1 to 10, characterized in that the regeneration of the catalysts used for the conversion of short-chain hydrocarbons by burning off the carbonaceous deposits with a nitrogen / oxygen mixture is such that temperatures of 55O ⁰ C are not exceeded and the catalyst after completion Burn for at least 1 hour in the air stream at 550 ⁰ C is left.