FI81028C - CATALOGS FOER AROMATISERING AV LAETTA KOLVAETEN OCH FOERFARANDE FOER FRAMSTAELLNING AV DENNA. - Google Patents

Description

81 028 1 Catalyst for the aromatization of light hydrocarbons and process for its preparation

Catalysts for aromatization from the Latvian flask and for the preparation of fractions 5

The invention relates to a catalyst for the production of aromatic hydrocarbons from aliphatic hydrocarbons and to a process for their preparation.

Zeolites of the ZSM'5 type are known to be used in processes for the production of aromatic hydrocarbons from aliphatic hydrocarbons.

In these processes, an aliphatic hydrocarbon is passed over the catalyst at an elevated temperature in the gas phase. As such catalysts, various types of zeolites are used in the preparation, which in addition may contain various metal compounds to increase the activity of the catalyst. For example, U.S. Patent 3,756,942 describes a ZSM-5 type catalyst in which sodium ions have been completely or partially replaced by hydrogen ions or ammonium ions. U.S. Patent 4,720,602 describes a zeolite of the ZSM-5 type, either impregnated with zinc-2q salt salt solution or in which the original cations have been completely or partially replaced by zinc ions.

Such catalysts are usually prepared starting from a solution containing water, tetrapropylammonium hydroxide or bromine -25 dia and a source of sodium oxide, alumina and silica. Such a mixture is allowed to react at a temperature and under conditions such that zeolite crystals are formed. The crystals are separated, washed and dried, absorbed with a solution of zinc or gallium salt and dried.

30

However, said zinc-containing zeolite catalysts have certain drawbacks when applied to the aromatization of hydrocarbons. Although their activity as catalysts may be good, the formation of coke during the aromatization reaction may become too high, which shortens the life of the catalyst. In addition, the stability of zinc in the zeolite catalyst may be poor, which also has a detrimental effect on the activity and service life of the catalyst.

The present invention relates to zinc or gallium-containing zeolite catalysts in which the coke formation of the catalyst in the aromatization of hydrocarbons and the stability of zinc or gallium in the zeolite are improved.

5

According to the present invention, it has been found that when the zeolite crystals are reconstituted after the addition of the zinc or gallium salt, a considerable improvement in the properties of the catalyst in propane aromatization is achieved, which results in lower coke-1Q formation and / or better zinc or gallium stability.

Thus, the process of the present invention is directed to a catalyst for producing aromatics from aliphatic hydrocarbons, which comprises a supported ZSM-5 type synthetic crystalline aluminosilicate to which zinc or gallium compounds have been added. The catalyst according to the invention is characterized in that said silicate is modified by carrying out, after the addition of the zinc or gallium compound, the reconstitution of the zeolite crystals by crystallization as well as ion exchange to acid form and calcination.

20

The present invention also relates to a process for preparing a catalyst for producing aromatics from aliphatic hydrocarbons, which catalyst comprises a synthetic aluminosilicate zeolite of the ZSM-5 type to which a zinc or gallium compound has been added. The process according to the invention is characterized in that said zeolite is modified after the addition of a zinc or gallium compound by adding water, tetrapropylarammonium compound and sodium hydroxide and heating the mixture thus obtained at elevated temperature for a sufficient time to dry the zeolite crystals. .

ZSM-5 zeolite can be prepared from solutions containing water, tetrapropylammonium hydroxide as well as sodium oxide, alumina 35 and silica, the resulting mixture typically containing various components in the following proportions: 0H '/ SiO2 0.07-1.0, R 1 N + / (R 2 N + + Na +) 0.2-0.95 (R-propyl), H 2 O / OH * 10-300 and SiO 2 / Al 2 O 3 5-100. The mixture is considered 3 81 028 - | At a temperature of 100-200 ° C long enough for zeolite crystals to form. A suitable time is usually between 6 hours and 60 days. The zeolite crystals formed are separated from the reaction medium by cooling to room temperature, filtering and washing.

5

Various substances can be used as a source of the above-mentioned oxides used in the preparation of ZSM-5 zeolite. Such sources include e.g. aluminosilicate, sodium aluminate, alumina, sodium silicate, silicon hydrosols, silica gels and silicic acid. The oxides required for the formation of the zeolite are obtained by using these starting materials as such or in mixtures with each other. The formation reaction can be carried out either as a batch process or continuously, and the crystal size and crystallization time of the zeolite may vary depending on the composition of the product and the quality of the starting materials in a manner known per se in the art.

15

The addition of zinc or gallium metals to ZSM-5 zeolites can be carried out by techniques known per se, e.g. ion exchange or impregnation with saline solutions containing zinc or gallium. Thus, if the cations of the aluminosilicate have been exchanged for zinc cations, the zinc is present in the zeolite as zinc ions. On the other hand, if zinc has been added by an impregnation technique using a zinc compound, for example zinc nitrate, at least some of the zeolite cations will be exchanged with zinc ions. Regardless of the technique by which the addition of zinc or gallium is performed, the appropriate total amount of zinc in the catalyst composition, as well as gallium, in the catalyst may range from 0.1 to 10% by weight, preferably from 0.5 to 2% by weight.

According to the invention, the addition of a zinc or gallium compound can be carried out by impregnating a zinc or gallium salt solution into either a ZSM-5 type zeolite in acid-2Q form or a non-calcined ZSM-5 type zeolite containing a tetrapropylammonium compound as an organic base.

Modification of the zeolite crystals can be performed by adding water, a tetrapropylammonium compound and sodium hydroxide and heating the mixture at an elevated temperature for a time sufficient to reconstitute the zeolite crystals. A suitable temperature is selected between 100 and 4,81028,200 ° C and a time between 15 and 50 hours. The above-mentioned calcination, acidification and drying and calcination at temperatures above 500 ° C can then be carried out, if desired, to form the final active catalyst.

5

The zinc or gallium-containing zeolite is activated for the propane aromatization reaction by heating the zeolite at a temperature above 500 ° C and then converting the zeolite to an acid form by ion exchange with ammonium salt solution, e.g. ammonium-1N nitrate solution at about 80 ° C .

The zeolite catalyst according to the invention can be combined or dispersed in a porous matrix material before use in a manner known per se. Commonly used matrix materials include e.g.

inorganic oxides such as alumina and silica, which are characterized by good pore properties, abrasion resistance and stability. The amount of support is preferably 25-50% by weight of the amount of catalyst.

2q The modified ZSM-5 zeolite catalyst of the invention is suitable as a catalyst for reactions in which aliphatic hydrocarbons are converted to aromatic hydrocarbons. A particularly suitable catalyst according to the invention is suitable for a process in which propane is contacted in the presence of said catalyst under suitable reaction conditions to convert propane to aromatics. Such reactions typically take place at 400-700 ° C and a relatively low pressure, for example 1-10 bar with a WHSV of 0.1-5 h ". After the reaction, the products are removed, the desired aromatics are distilled off and the remaining starting material is recycled. reaction.

30

The catalyst according to the invention and its use in the aromatization of propane are illustrated by the following examples.

Example 1 ZSM-5 zeolite is synthesized using 187.2 g of tetra-propylammonium bromide, 275 ml of 1-N NaOH, 4.6 g of MaAlO 2> 172 g of a pack of 35 5 81 028 l of loid silica solution (Ludox HS-40) and 1030 g of water as starting materials. The starting materials were stirred in an autoclave and crystallization was performed with stirring at 160 ° C for 7 days. The product was filtered off and dried at 115 ° C and taken up in Ζη (ΝΟβ) 2.4Η2θ: η aqueous solution. The amount of zinc in the impregnation solution was calculated by using 1.15 g of zinc salt dissolved in 7 ml of water per 10 g of zeolite. The product was then dried at 115 ° C.

The zinc salt-impregnated zeolite catalyst containing tetrapro-py0 methylammonium bromide was modified in an autoclave by adding 15 g of TPABr, 1.25 g of NaOH and 150 g of water per 10 g of zeolite. The temperature was 165 ° C and the reaction time was 16 h. After drying (115 ° C), the product was calcined at 540 ° C for 4 hours. The ion exchange was then performed with 3-N aqueous ammonium nitrate solution at 80 ° C 3 times.

-jg The solution was used at 15 ml / g zeolite. After ion exchange, drying and calcination were performed for 4 hours at 540 ° C. A catalyst was prepared from zeolite and silica Ludox AS-40 so that the SiO 2 support content of the finished catalyst was 35% by weight and the particle size was 0.15-0.35 mm.

20

Example 2

The catalyst was prepared as in Example 1, but 1.95 g of zinc salt was used per 10 g of zeolite.

25

Example 3

The catalyst was prepared as in Example 1, but 0.55 g of 032 (804) 3 was used per 10 g of zeolite.

30

Example 4

The zeolite was prepared as in Example 1, but after the first crystallization, drying was performed at 115 ° C and calcination at 35,540 ° C for 4 hours. The zeolite was acidified by ion exchange 3 times with ammonium nitrate solution as in Example 1. After drying and calcination (540 ° C, 4 h), impregnation with zinc nitrate solution was performed using 1.35 g of zinc nitrate per 10 g of zeolite and 8 ml of water. The product was calcined at 540 ° C for 2 hours.

g The zinc-containing acid zeolite was reprocessed in an autoclave, deionized and a catalyst was prepared as in Example 1.

Example 5 10

The catalyst was prepared as in Example 4, but 2.25 g of zinc nitrate per 10 g of zeolite was used for impregnation.

Example 6 15

A zinc catalyst prepared by impregnation of zeolite was prepared as a reference catalyst. The acid zeolite was prepared as in Example 4. Absorption was performed with a Zn (NOj) 2 solution using 1.85 g of Ζη (Νθ3) 2 · 4Η2θ and 10 ml of water. After drying, sample 2q was calcined for 2 h at 540 ° C. The catalyst was prepared from zeolite with a SiO 2 * support content of 35%.

Example 7 The catalysts in Examples 1-6 were tested for aromatization of propane in a microreactor using 5 g of catalyst. The experiments were performed at atmospheric pressure, 550 ° C and WHSV for 1 h. Comparison of the catalysts was performed at a catalyst age of 35-40 g / g. The total age of the catalysts at the end of the period was 40-45 g / g.

30

After the run, the carbon content of the catalysts was determined. The zinc content was analyzed both before the run and after the run and regeneration. Regeneration took place in an oven by raising the temperature at a rate of 40 ° C / h to 480 ° C, where it was kept for 4 hours.

The temperature was then raised at a rate of 100 ° C / h to 540 ° C and maintained for a further 2 hours. The results are shown in the table below.

Il 7 81 028 1 Table Sample Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 6 g Zeolite: Al, p-% 1.8 1.7 2.0 2.1 2.0 1, 9

Catalyst:

Zn, p-% fresh 0.8 1.5 1) 1.2 2.3 1.5 10 Zn> P *% reS · 0.7 1.4 1.2 2.1 1.2 C, p- % 0.8 0.9 0.6 2.5 2.6 1.5 (Cat. Age g / g) 40.0 39.0 44.0 39.0 41.0 42.0

Conversion, wt% 62.3 64.3 44.9 77.4 72.6 57.2 15 Aromatics, wt% 34.9 31.9 24.7 38.3 32.8 28.1

Product distribution, wt% - CH4 + C2H6 35.2 40.0 28.3 44.7 46.0 37.3 - C2-C5 alkenes 7.8 9.0 14.3 5.3 7.8 12, 5 20 'C4h10 + c5h12 ° -8 1.2 2.4 0.4 0.9 2-2 - Aromatics 56.0 49.6 55.0 49.5 45.2 49.2

Arom. j accumulation, wt% - Benzene 38.3 36.0 36.4 39.1 39.0 38.0 25 - Toluene 39.4 35.0 37.7 36.7 36.9 37.7 - Cg- aromatics 15.0 15.7 16.7 14.2 15.8 17.5 - C9 + aromatics 7.4 13.5 9.2 10.1 8.4 6.8 T 550 ° C, WhSV 1 h ' 1, age about 40 g / g 30 1) Ga content about 1 wt% 35

Claims (6)

1 Patent claim A catalyst for producing aromatics from aliphatic hydrocarbons, which catalyst comprises a synthetic crystalline aluminum silicate of ZSM type pk a carrier in which silicate or zinc or gallium compound, characterized in that said silicate is formed by the addition of the zinc or gallium compound results in a reshaping of the zeolite crystals as well as an ion exchange in acid form and calcination. Catalyst according to claim 1, characterized in that the amount of zinc or gallium addition is 0.5-2% by weight of the catalyst amount and the amount of support is 25-50% by weight of the catalyst. A process for preparing a catalyst for producing aromatics from aliphatic hydrocarbons, comprising a ZSM-type synthetic aluminum silicate in which zinc or gallium compound is added, characterized in that for said zeolite after the addition of zinc. or gallium compound 20 performs a modification by the addition of water, tetrapropylammonium compound and sodium hydroxide and by heating the thus-obtained mixture at elevated temperature for a sufficiently long time to reshape the zeolite crystals, following conventional drying, ion exchange and calcining operations. for the zeolite. 4. A process according to claim 3, characterized in that the zeolite is converted to acid after the zinc or gallium addition and reshaping of the crystals. 30 Process according to Claim 3 or 4, characterized in that the amount of zinc or gallium compound added is 0.5-2% by weight of the catalyst and that the amount of carrier is 25-50% by weight of the catalyst. 35 6. A process according to claims 3-5, characterized in that the zinc or gallium compound is added by impregnation II of the zeolite with a saline solution containing zinc or gallium compound and the impregnation is carried out either in a zeolite of zsm-5. acid form or a ZSM-type non-calcined zeolite containing an tetrapropylammonium compound as an organic base. 5 10 15 20 25 30 35