JPH0659406B2 - Method for producing platinum group metal-supported zeolite catalyst - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a platinum group metal-supported zeolite catalyst useful for isomerizing aromatic hydrocarbons. More specifically, it relates to a method for producing a platinum group metal-supported zeolite catalyst for isomerizing aromatic hydrocarbons containing 8 carbon atoms and containing ethylbenzene.

2. Description of the Related Art Catalytic performance in xylene isomerization is important not only for the ability to bring the p-xylene concentration close to an equilibrium state while suppressing xylene loss due to side reactions, but also for ethylbenzene. Since conventional silica-alumina catalysts have a poor reaction product with respect to ethylbenzene, an ethylbenzene removal tower was installed for the purpose of preventing concentration in the isomerization system, but at that time, a considerable amount of xylene was lost to the outside of the system. Was there. In order to eliminate such xylene loss and improve the efficiency of the entire isomerization process, a unique solid acid catalyst represented by ZSM-5 zeolite has been proposed, which disproportionates the coexisting ethylbenzene as well as the isomerization reaction between xylenes. It is now possible to construct an efficient isomerization circulation system that does not require an ethylbenzene removal column by converting into easily separable benzene and diethylbenzene. The xylene disproportionation reaction, which is a side reaction, was suppressed shape-selectively and the xylene loss was reduced, but there was a limit to the control of the selectivity because the reactions all exhibited the same acid function. Mobil high-temperature isomerization method enables more selective isomerization reaction with a binary catalyst that combines the hydrodealkylation function of ethylbenzene at the noble metal active site and the high-temperature isomerization ability of low-acid ZSM-5 zeolite. Therefore, the xylene loss can be further reduced and the industrially useful benzene yield can be increased.

Low acidification of ZSM-5 zeolite is 1) SiO during hydrothermal synthesis
₂ / A ₂ O ₃ > 500 (molar ratio) for crystallization (JP-A-54-24834), 2) SiO ₂ / A
_After carrying Pt on the basis of ZSM-5 of ₂ O ₃ > 12 (molar ratio), steam treatment (JP-A-56-158150).
No. 56-43219, No. 57-1453.
9 and 57-150624).

For example, in JP-A-56-158150,
Preferred manufacturing procedure of _{Pt · ZSM-5 / A 2} O 3 composite catalyst is noted.

<Conventional method> <Method according to JP-A-56-158150> Problems to be Solved by the Invention The ZSM-5 zeolite and the like are useful as xylene isomerization catalysts, but in addition to the ethylbenzene dealkylation activity (precious metal active site) and xylene isomerization activity (acidic site), both active sites Therefore, the control of side reactions (xylene dealkalization, benzene ring hydrogenation, xylene disproportionation) is still insufficient, and suppressing xylene loss and hydrogen consumption are industrially serious problems.

Means for Solving the Problems In view of the above-mentioned technical problems, as a result of intensive studies on a isomerization method using a platinum group metal-containing zeolite catalyst for a C ₈ aromatic mixture composed of ethylbenzene and xylene, a platinum group metal component was obtained. Is carried out in the presence of hydrogen under a temperature condition of 300 to 450 ° C. in the gas phase, by using a catalyst prepared by carrying out a steam treatment before carrying out calcination in the air after carrying out ion exchange. The inventors have found that the chemical dealkylation function and the xylene isomerization ability are selectively expressed, and the hydrogen consumption can be suppressed together with the loss of xylene, and the present invention has been completed.

That is, the present invention is characterized in that, when preparing a zeolite catalyst carrying a platinum group metal component, after the step of carrying the platinum group metal component by ion exchange, a steam treatment is carried out before the step of firing in air. The present invention provides a method for producing a platinum group metal-supported zeolite catalyst for isomerizing aromatic hydrocarbons having 8 carbon atoms.

Low acidification of zeolite by steam treatment is a conventionally known technique, for example, "Journal of Katalysis", vol. 6, pages 278 to 287 (1966) and "Applied catalysis", vol. 13, p. 27. ~ Page 38 (1984).

Zeolite catalyst for platinum group metal-containing xylene isomerization (mainly
With respect to ZSM-5), it is generally practiced from a patent that steam treatment is performed to reduce the acidity in the final step of the prepared catalyst.

The binderless type TSZ catalyst proposed earlier (Japanese Patent Application Laid-Open No. 61-61160)
-69738 and JP-A-61-74647), steam treatment has been carried out in the final step. As a result of detailed examination of the catalyst preparation step, after carrying out ion exchange loading of the platinum group metal component, calcination in air was carried out. Prior to this, it was revealed that the catalyst consisting of steam treatment selectively exhibits the hydrodealkylation function and the xylene isomerization ability of ethylbenzene and can suppress the hydrogen consumption as well as the loss of xylene.

In the "journal OF Kiyatarishisu" Vol. 89 520, pages ～526 (1984), after Pt (NH _{3) 4} ²⁺ ion exchange into ZSM-5 zeolite, by firing in the air, Pt is highly dispersed However, the steam treatment before calcination in the air in the present invention not only serves to lower the acidity of the zeolite, but also suppresses the high dispersion of Pt to the contrary, so that a suitable Pt is obtained. It has been shown to be extremely effective in maintaining the particle size and maintaining the ethylbenzene dealkylation activity and the xylene isomerization activity in good balance,
It cannot be achieved by the preparation method that has been prepared so far for the purpose of making Pt highly dispersed.

The inventors of the present invention have studied these mechanisms in detail, and the effect of the step of steam treatment is simply carried out after carrying the platinum group metal component, after carrying the platinum group metal component, and then baked and steamed, The amount of acid and the amount of CO adsorbed (per supported metal) were measured by steaming after supporting a platinum group metal component and then calcining. That is, the effect of the present invention cannot be fully theoreticalized by this alone, but the amount of acid is greatly reduced by steam treatment, the effect is almost the same and the disproportionation reaction of xylene is suppressed, and xylene loss is It is considered that this corresponds to the decrease in reaction results. On the other hand, it has been found that the amount of CO adsorbed per supported metal decreases in the order of, but particularly by the method of the present invention. The CO adsorption capacity is considered to correspond to the dispersity of the supported metal, and is thought to be related to the nuclear hydrogenation and nuclear decomposition of aromatic nuclei. It is considered that the loss of hydrocarbons, especially xylene can be suppressed to a low level, and the isomerization reaction can be performed with a small hydrogen consumption amount.

Zeolites that can be used in the present invention, that is, parent zeolites, are ZSM-5, ZSM-11, ZSM-12, Z whose main cavity inlet is a 10-membered oxygen ring developed by Mobile Oil Company.
SM-23, ZSM-35, ZSM-4, ZSM-10, ZSM-20, etc. in which the main cavity inlet is a 12-membered acid ring, TSZ crystalline aluminosilicate, and binderless TSZ zeolite Binderless type TSZ zeolite is particularly preferable. The method for preparing these parent zeolites is described in detail in the following US Patent (US) Specification, British Patent (GB) Specification or Patent Publication.

ZSM-5 (US Pat. No. 3,702,886), ZSM-11 (US Pat. No. 3,709,979), ZSM-12 (US Pat. No. 3,832,449), ZSM-23 (US Pat. 076,842), ZSM-35 (US Pat. No. 4,016,245), ZSM-4 (UK Patent 1,297,256), ZSM-10.
(US Pat. No. 3,692,470), ZSM-20 (US Pat. No. 3,972,982), TSZ crystalline aluminosilicate (JP-A-58-45111), binderless type.
TSZ zeolite (Japanese Patent Laid-Open No. 59-162952) Further, as a method for preparing a catalyst useful in the present invention by supporting a platinum group metal on the parent zeolite, for example, the method described in the section of "Prior Art", That is, the steps 1 to 8 of the post impregnation method, the steps 1 to 7 of the co-crystallization method, the steps 1 to 8 of the complex impregnation method, or the steps 1 to 8 of the zeolite impregnation method are adopted. be able to. Here,
The solution used for supporting the platinum group metal is a platinum ammine complex ion solution (Pt (NH ₃ ) ₄ ^2+, etc.), palladium complex ion solution (Pd (NH ₃ ) ^2+, etc.) Ni (NO ₃ ) ₂ aqueous solution. And so on.

The catalyst useful in the present invention can be obtained by subjecting the above-mentioned treatment liquid to steam treatment and finally calcining in air. The conditions of steam treatment are 400 ° C. to 700 ° C. for 1 to 24 hours, preferably 500 ° C. to 600 ° C. for 10 to 20 hours. At this time, the water vapor may be diluted with an inert gas such as nitrogen gas.

Conversion Conditions The conversion conditions are 250 ° C. to 500 ° C., preferably 300 ° C.
450 ° C, atmospheric pressure to 60 kg / cm ² G, preferably 5 to 30 k
g / cm ² G, liquid hourly space velocity (LHSV) 0.5 to 50 (hour ^-1 ),
Preferably, it is 2 to 20 (hour ^-1 ), and the hydrogen / feedstock hydrocarbon molar ratio is 0.1 to 10, preferably 0.5 to 5.

EFFECTS OF THE INVENTION By using the catalyst produced by the method of the present invention, the isomerization of C ₈ aromatic hydrocarbons can be carried out efficiently.
That is, para-xylene can be advantageously obtained by a xylene isomerization reaction that achieves a high conversion rate of ethylbenzene while keeping xylene loss at a low level and consumes less hydrogen.

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Preparation of catalyst Preparation example 1: Preparation of crystalline aluminosilicate (TSZ) powder 25.0 g of aluminum sulfate 18-hydrate was dissolved in 162.3 g of water, and 16.5 g of concentrated sulfuric acid (95% by weight) was added to the solution to form aluminum sulfate. A solution was prepared (solution A). Aside from this
A mixed solution of 118.3 g of water and 234.0 g of Japanese Industrial Standard No. 3 water glass (9.32% by weight of Na ₂ O, 28.9% by weight of SiO ₂ : hereinafter abbreviated as No. 3 water glass) was prepared (solution B). 71.8g
A solution was prepared by dissolving sodium chloride in (4) in water (463.4 g) (C solution). An aqueous reaction mixture was prepared by simultaneously adding and mixing solution A and solution B to solution C while stirring. The composition of this reaction mixture is expressed as the molar ratio of oxides to 2.1 Na ₂ O.
· _A Atsuta with _{2 O 3 · 30.0 SiO 2 ·} 133.4 H 2 O.

The obtained aqueous reaction mixture was poured into a SUS autoclave, the temperature was raised, and the autoclave was heated and maintained at 180 ° C. for 40 hours. The crystallized solid product was filtered off, washed with water and dried at 110 ° C. When a sample of the solid product was subjected to chemical analysis, a chemical composition of Na ₂ O; 3.13% by weight, A ₂ O ₃ ; 5.03% by weight, SiO ₂ ; 83.6% by weight, H ₂ O; 8.2% by weight was obtained. It was This was expressed in terms of oxide molar ratio as follows.

1.02 Na ₂ O · A ₂ O ₃ · 28.2SiO ₂ · 12.5 H ₂ O This product was confirmed by X-ray analysis to be a TSZ crystalline aluminosilicate.

Preparation Example 2: Binderless crystalline aluminosilicate (TSZ)
Preparation of TSZ powder (50 g) produced by the method of Preparation Example 1 and 380 g of silica-alumina wet gel (water content 86.8% by weight) were kneaded with a kneader until the water content became moldable, and the mixture was extruded with an extruder. Molded into an outer diameter of approximately 1.5 mm pellet.

The silica-alumina wet gel used here is aluminum sulfate 25.0 g, 95% by weight sulfuric acid 13.0 g, pure water 162.3 g.
The aluminum sulfate aqueous solution of No. 3, 234.0 g of No. 3 water glass, and 118.3 g of pure water were added to 463.4 g of pure water to prepare a solution, which was then filtered.

After drying the pellets at about 110 ° C. for 5 hours, a part of the pellets was collected and subjected to chemical analysis to find that SiO ₂ was 85.3% by weight and A ₂
O ₃ was 4.98 wt%, Na ₂ O was 7.05 wt%, and the ignition loss at 900 ° C. was 2.65 wt%.

This is further baked at 600 ° C. for about 3 hours and 70 g of it is collected and combined with 60.5 g of sodium chloride and 867 g of pure water to obtain SU.
It was put into an S autoclave and crystallized at 180 ° C. for 4 hours. After cooling, the pellets were taken out from the autoclave, washed, dried and subjected to powder X-ray diffraction analysis.
It was confirmed to be TSZ crystalline aluminosilicate.

Also, from the electron micrograph, most of the crystalline material,
It was revealed that the silica-alumina wet gel became TSZ crystalline aluminosilicate.

Preparation Example 3: Preparation of ZSM-5 zeolite 14.3 g of aluminum sulfate was dissolved in 390 g of pure water, and further 8.7 g of concentrated sulfuric acid (95% by weight), 51.4 g of tetrapropylammonium bromide (TPABr) and 39.0 g.
Sodium chloride was added to prepare an aluminum sulfate solution. This aluminum sulfate solution was added with 77.0 g of water and 156.
Mix with 0 g of No. 3 water glass mixed solution with stirring,
An aqueous reaction mixture was obtained having a composition of 4.5 (TPA) ₂ O.4.0Na ₂ O.A ₂ O ₃ / 35.0SiO ₂ .1477H ₂ O expressed in terms of oxide molar ratio. The aqueous reaction mixture was poured into a SUS autoclave to raise the temperature, and was heated and maintained at 160 ° C. for 20 hours under self-pressure. The crystallized solid product was filtered off, washed with water and dried at 110 ° C.
When a sample of this solid product was subjected to chemical analysis, (TP
A) ₂ O; 11.8% by weight, Na ₂ O; 1.80% by weight, A ₂ O ₃ ; 4.
A chemical composition of 62% by weight, SiO ₂ ; 75.4% by weight, H ₂ O; 6.36% by weight was obtained. This was expressed in terms of oxide molar ratio as follows.

0.67 (TPA) ₂ O ・ 0.64Na ₂ O ・ A ₂ O ₃・ 27.7SiO ₂・ 7.8H ₂ O This product was calcined at 540 ° C. for about 3 hours and then subjected to X-ray analysis, using ZSM-5 zeolite. I confirmed that there is.

Preparation Example 4: Preparation of Catalysts A, B and C Using a 5% ammonium chloride (NH ₄ C) solution to ion-exchange the sodium ions of the TSZ crystalline aluminosilicate obtained in Preparation Example 1 at 80 ° C. The ion exchange operation was performed for 1.5 hours. This operation was repeated 4 times to prepare ammonium (NH ₄ ) type TSZ crystalline aluminosilicate powder.

The above NH ₄ type TSZ crystalline aluminosilicate powder was collected, immersed in an aqueous solution containing platinum ammine complex ion (for example, Pt (NH ₃ ) ₄ ²⁺ ) at room temperature, and then the solid was separated by filtration, A platinum (Pt) -ammonium (NH ₄ ) type TSZ crystalline aluminosilicate powder was prepared by washing with water. This Pt-NH ₄ type TSZ was mixed with a separately prepared alumina binder at a ratio of 7: 3 (weight ratio after firing), water was added and kneaded, and then an extruder was used to form a pellet with an outer diameter of about 1.5 mm. Molded. This was dried and then baked at 600 ° C for 3 hours to obtain platinum (Pt) -hydrogen (H).
A catalyst containing a type of TSZ crystalline aluminosilicate was prepared (hereinafter referred to as catalyst A). When the platinum content of the catalyst A was analyzed, it was 0.81% by weight.

The catalyst A was further subjected to 550 at atmospheric pressure using 100% steam.
Catalyst B was prepared by treating at 16 ° C. for 16 hours.

Prior to calcination at 600 ° C. for 3 hours in the preparation of catalyst A, 100% water vapor was preliminarily used under atmospheric pressure at 550.
Catalyst C was prepared by treating at C for 16 hours.

Preparation Example 5: Preparation of Catalysts D, E and Catalyst F 60 g of the sodium type binderless TSZ crystalline aluminosilicate pellet obtained in Preparation Example 2 was used in an amount of 15% by weight of ammonium chloride solution of 5% by weight per 1 g of TSZ pellet. A total of 4 times of ion exchange treatment was carried out at 80 ° C. (each treatment time was 1.5 hours). Next, the ion exchange product was washed with water and dried at 110 ° C.
Binderless TSZ crystalline aluminosilicate pellets of the (NH ₄ ) type were prepared. As a result of chemical analysis, it contained 0.01% by weight or less of Na ₂ O. The SiO ₂ / A ₂ O ₃ molar ratio was 28.9.

Further, 10 g of the above NH ₄ type binderless TSZ was sampled and immersed in an aqueous solution containing a platinum ammine complex ion (eg Pt (NH ₃ ) ₄ ²⁺ ) at about 70 ° C. for about 20 hours, and then solid (pellet). Separated, washed with water, dried at 110 ° C and then 600 ° C
Binderless containing platinum after firing for 3 hours
TSZ crystalline aluminosilicate powder was prepared (hereinafter referred to as catalyst D). Catalyst D was further prepared by using 100% steam under atmospheric pressure,
Catalyst E was prepared by treating at 0 ° C. for 16 hours.

Before calcination for 3 hours at 600 ° C. in the preparation of catalyst D, 100% steam was used under atmospheric pressure beforehand.
Catalyst F was prepared by treating at 0 ° C. for 16 hours.

Preparation Example 6: Preparation of Catalysts G, H and Catalyst I The ZSM-5 zeolite powder obtained in Preparation Example 3 was prepared as Preparation Example 4
After performing ammonium ion exchange in the same manner as in the preparation of the catalyst A described in 1., platinum ammine complex ions (for example, Pt (N
H ₃ ) ₄ ²⁺ ) and treated with platinum (Pt) -ammonium (NH ₄ ) type Z
SM-5 powder was prepared. After molding using an alumina binder, drying and firing are performed to obtain platinum (Pt) -hydrogen (H) ZSM-
A catalyst containing 5 was prepared. (Hereinafter, this is referred to as catalyst G.) Catalyst G is further subjected to 550 by using 100% steam under atmospheric pressure.
Catalyst H was prepared by treatment at 16 ° C. for 16 hours.

Before calcination at 600 ° C. for 3 hours in the preparation of catalyst G, catalyst I was prepared in advance by treating with 100% steam at 550 ° C. for 16 hours under atmospheric pressure.

Preparation Example 7: Preparation of Catalysts J and K The binderless TSZ crystalline aluminosilicate pellet obtained in Preparation Example 2 was subjected to ammonium ion exchange in the same manner as in Preparation of Catalyst D, and then 1N Ni (NO ₃ ). _{The two} solutions were treated at 80 ° C. for 1 hour, washed with water and dried. 6
Binderless TSZ crystalline aluminosilicate catalyst containing 0.85% by weight of Ni was obtained by treating with 100% steam under atmospheric pressure for 16 hours at 550 ° C. before firing at 00 ° C. for 3 hours. Was obtained (below,
This is called catalyst J).

Further, a binderless TSZ crystalline aluminosilicate containing palladium was prepared in the same manner as the catalyst J except that an aqueous solution containing a palladium (Pd) complex ion (for example, Pd (NH ₃ ) ²⁺ ) was used. A catalyst was obtained (hereinafter referred to as catalyst K).

Isomerization reaction test (Examples 1 to 6, Comparative Examples 1 to 6) The catalysts A, B, C, D, E, F, G, H, I, and
For J and K, an isomerization reaction test was conducted using a fixed bed flow reactor. For Examples 1 to 3 and Comparative Examples 1 to 6, the feeds were 0.7 wt% toluene, 16.5 wt% ethylbenzene, 9.3 wt% p-xylene, 59.8 wt% m-xylene, and 13.7 wt% o-xylene.
Further, in Examples 4 to 6, toluene 0.7% by weight, ethylbenzene 13.4% by weight, p-xylene 10.9% by weight, m
A feed of 61.7% by weight of xylene and 13.3% by weight of o-xylene was used.

The test reaction conditions are a temperature of 300 to 400 ° C. and a pressure of 17 kg / cm ^2.
G, WHSV 10W / H / W, ratio of hydrogen to raw material liquid (H ₂ / C ₈ ) 1.8
It was mol / mol. The conditions and reaction results of each test are first
Shown in the table. The WHSV was calculated based on the zeolite content.

Moreover, the catalyst performance is calculated and evaluated by the following formula, and the results are shown in Table-1.
And Table-2.

H ₂ consumption (SCF / B) is the amount of feedstock and produced oil (liquid and gas)
It was calculated from the hydrogen balance in the composition analysis of.

[ _P X] _F , [ _P X] _P and [ _P X] _E are p-xylene concentrations in the feed oil, the produced oil and the xylene 3 isomer at equilibrium.

[X] _F and [X] _P are xylene concentrations in the feedstock oil and the produced oil.

[EB] _F and [EB] _P are ethylbenzene concentrations in the feed oil and the produced oil.

Comparison of acid amount and CO adsorption amount For catalysts D, E and F, the acid amount and CO adsorption amount were measured. The results are shown below.

The following methods were used to measure the acid amount and CO adsorption amount.

(1) Method for measuring acid amount It was measured by the temperature programmed desorption method (TPD method) of pyridine. Regarding the TPD method, magazine "Catalyst" Vol. 21, 79 (1979)
In detail. The amount of pyridine desorbed when the temperature was raised at a constant rate was detected by gas chromatography, and the amount of acid was determined from the amount of desorbed pyridine as a whole.

(2) CO adsorption amount Measured by the pulse method. After reducing the Pt-supported zeolite sample with hydrogen, inject a fixed amount of CO at room temperature,
The unadsorbed CO was detected by GC, and the CO adsorption amount was measured from the difference with the injected CO amount.

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Claims (1)

[Claims] 1. A method for producing a zeolite catalyst carrying a platinum group metal component, which comprises performing steam treatment after the step of carrying the platinum group metal component by ion exchange and before the step of firing in air. A method for producing a platinum group metal-supported zeolite catalyst for isomerization of aromatic hydrocarbons having 8 carbon atoms.