JP4235731B2 - Process for producing molded catalyst for dehydroaromatization reaction of lower hydrocarbon - Google Patents

Description

The present invention provides a catalyst molded body for efficiently producing aromatic compounds mainly composed of benzene and naphthalene, which are basic raw materials for various chemical products, and high-purity hydrogen gas from lower hydrocarbons such as methane. It is about the method.

  Conventionally, attempts have been made to directly convert lower hydrocarbons to high-value-added aromatic hydrocarbons using a catalyst. When the conversion reaction is performed using a hydrocarbon having 2 or more carbon atoms in the lower hydrocarbon as a raw material, Ga-supported H-type ZSM-5 or Zn-supported H-type ZSM-5 may be highly active as a catalyst. [For example, “Catalyst Review Science and Engineering” 34 (3), 179-226 (1992)]. However, when methane is used as a raw material, the activity of these catalysts is low, and there are examples of attempts to improve by loading Pt on GaZSM-5 [for example, “Zeolites: Facts, Figures, Future” 1183-1192 ( 1989)], the activity is not sufficient, and there is a problem that the activity is rapidly reduced by carbon deposition.

  On the other hand, as shown in, for example, JP-A-10-272366 and JP-A-2001-334151, a catalyst in which molybdenum, tungsten, rhenium or the like is supported on a metallosilicate represented by ZSM-5 is a dehydrogenated aromatic of methane. It is known to be effective for the chemical reaction. These catalysts are superior in that they are highly active as compared to the Pt-supported GaZSM-5 and have a long life because of less carbon deposition.

  As a mechanism of the dehydroaromatization reaction of methane in these catalysts, a mechanism that sequentially proceeds on two different active sites has been generally proposed [for example, “Natural Gas Conversion V” 403-410. (1998)]. That is, methane is first activated on a catalytically active metal component such as molybdenum, tungsten, rhenium, and then polymerized and cyclized on the acid sites of ZSM-5. In addition, since the catalytically active metal component is supported in the pores of ZSM-5, the aromatization reaction also occurs mainly in the pores, and as a result, carbon deposition is suppressed by the steric restriction of the pores. This is one of the important features of this catalyst.

  As a method for producing a catalyst in which a catalytically active metal component such as molybdenum, tungsten, or rhenium is supported on a metallosilicate such as ZSM-5, a salt containing these catalytically active metal components is mainly used as a precursor in these aqueous solutions. A so-called impregnation method or ion exchange method in which silicate is impregnated and then post-treatment such as drying / calcination [for example, JP-A-10-272366], or a compound containing the above catalytically active metal component is sublimated or evaporated. Thus, a method of precipitating on a metallosilicate [JP 2002-336704 A] is employed.

  As described above, the prior art methane dehydroaromatization reaction catalysts are limited to combinations of catalytically active metal components and metallosilicates supported by each, but contain metallosilicates. In most cases where a catalyst is used in an actual industrial process, a binder is added for the purpose of obtaining practical strength and wear resistance, and for the purpose of improving the moldability when producing a catalyst molded body. Manufactured.

  The following method is illustrated as an example of the manufacturing method of a practical metallosilicate containing catalyst molding. First, after synthesizing a metallosilicate powder by a hydrothermal synthesis method, a binder and, if necessary, a thickener or a dispersant are added to the metallosilicate, and these raw materials are kneaded in water. Next, after molding by a method such as extrusion molding or tableting, it is dried and fired. When the catalytically active metal component is supported on the metallosilicate, it is carried out by using a method such as an impregnation method on the finished molded body. As the kind of binder, an inorganic compound such as silica, alumina, clay mineral or the like is used alone or in combination, and it is often added in an amount of about 10 to 50% by weight based on the weight of the molded body after molding.

  However, when a catalytically active metal component such as molybdenum, tungsten or rhenium is supported on a metallosilicate catalyst molded body containing a binder, these catalytically active metal components are supported not only on the metallosilicate but also on the binder. become. As described above, the presence of the catalytically active metal component in the pores of the metallosilicate suppresses carbon deposition and the dehydroaromatization reaction proceeds selectively, but the catalytic activity supported on the binder. Since a large amount of carbon is generated without suppressing carbon deposition on the metal component, it is considered that the catalytically active metal component supported on these binders hardly contributes to the dehydroaromatization reaction. . Furthermore, since a large amount of hydrogen is generated at the same time as the generation of carbon, this hydrogen suppresses the progress of the dehydroaromatization reaction and degrades the conversion performance, and the deactivation due to the accumulation of carbon. Problems also arise.

  From these facts, it is desirable that the expensive catalytically active metal component is selectively supported only on the metallosilicate component.

An object of the present invention is to provide a method for producing a molded catalyst for a dehydroaromatization reaction of a lower hydrocarbon that is highly active and whose activity is prevented from decreasing.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have supported a catalytically active metal component on a metallosilicate, and then the catalytically active metal component moves onto a binder in the subsequent catalyst molded body manufacturing process. It has been found that a highly active catalyst molded body in which a decrease in catalyst performance is prevented can be obtained by producing so as not to cause the present invention, and the present invention has been completed.

That is, according to the present invention, a method for producing a molded catalyst for the dehydroaromatization reaction of lower hydrocarbons shown below is provided.

After impregnating the metallosilicate with an aqueous solution or alcohol solution of a precursor containing molybdenum as a catalytically active metal component, firing the molybdenum oxide on the surface of the metallosilicate and carrying out the carbide treatment, and then mixing with the binder component A method for producing a molded catalyst for a dehydroaromatization reaction of a lower hydrocarbon, characterized by molding.

According to the molded catalyst body produced by the production method of the present invention, since no catalytically active metal component is supported on the binder surface, side reactions on the binder can be effectively controlled. As a result, the hydrocarbon conversion performance equivalent to that of the catalytically active metal component-supported metallosilicate catalyst without adding a binder is exhibited.

  Details of the present invention will be described below.

  There are no particular restrictions on the type of metallosilicate used in the present invention, but among ZSM-5, ZSM-11, MCM-22, and ZRP-1 having the optimum pore diameter for efficient aromatization reaction. It is preferable to select. Further, a combination of the above metallosilicates, or a combination of the above metallosilicate and a metallosilicate other than the above may be used. Examples of the metal component constituting the crystal skeleton of the metallosilicate include aluminum, gallium, and zinc. Moreover, the case where the metallosilicate which consists only of silicons according to a condition is used is also considered. Although it is preferable that the metallosilicate is basically used as a proton type (H type), it is also possible to use one obtained by substituting a part of the proton with another ion.

  The metallosilicate is used in a powder form, and the average particle size thereof is 0.1 to 50 μm, preferably 0.1 to 20 μm.

Further, molybdenum is selected as the catalytically active metal component used in the present invention . A precursor containing a catalytically active metal component is used for supporting the catalytically active metal component on the metallosilicate. Examples of the precursor include nitrates, oxides, chlorides, condensed acid salts and the like.

  As a method for supporting the catalytically active metal component on the metallosilicate, a conventionally known method, for example, a method of impregnating a metallosilicate into an aqueous solution or an alcohol solution of the above-described precursor, or the above-mentioned [JP 2002-336704 A] is described. Examples of the vapor-phase deposition method that can be seen are exemplified, but there is no problem even if it is supported by a method other than these, for example, an incipient wetness method or an ion exchange method similar to the impregnation method. The amount of the catalytically active metal component supported is not particularly limited, but is 0.1 to 50% by weight, preferably 0.1 to 20% by weight, based on the metallosilicate.

  The most important feature of the present invention is that in the production of a practical catalyst molded product for a dehydroaromatization reaction of a lower hydrocarbon comprising a catalytically active metal component, a metallosilicate, and a binder, the catalytically active metal component is previously converted to a metallosilicate. Further, the catalyst active metal component is immobilized on the metallosilicate so as not to move onto the binder in the subsequent catalyst molded body production process.

  As a production method in which the catalytically active metal component supported on the metallosilicate does not move onto the binder in the catalyst molded body production process, there are the following methods.

The precursor of the catalytically active metal component metallosilicate Oa et al was beforehand high temperature firing carrying, further performs mosquito Baido process in a method for subsequently performing mixing operation of a binder in water or an organic solvent. Although gas containing methane is preferably a mosquito Baido treatment agents, it may be used a gas containing other hydrocarbons. By this carbide treatment, the catalytically active metal component is converted into metal carbide . The concentration of Ca Baido treatment agent is 0.1 to 100% by volume, preferably from 1 to 100% by volume.

Incidentally, before hear Baido process are those conventionally known, can be easily performed according to known methods.

  The catalytically active metal component-supported metallosilicate subjected to these treatments is kneaded and mixed with a binder in water or an organic solvent. As the binder component, conventionally known ones such as clay mineral, silica, alumina, silica / alumina, titania, zirconia and combinations thereof are preferably used. The binder is used in the form of powder, and the average particle size thereof is 0.1 to 300 μm, preferably 0.1 to 100 μm. The amount of the binder used is preferably in the range of 10 to 50% by weight in the catalyst molded body, but those exceeding this range can also be produced. Moreover, you may add a thickener or a dispersing agent as needed. The obtained mixture is molded and dried by a conventional method. The drying process must be avoided because the catalytically active metal component migrates to the binder when it is dried at a temperature higher than 500 ° C. in the presence of oxygen. The drying step is performed at 80 to 500 ° C., preferably 130 to 450 ° C. under a condition where the oxygen concentration is 20% by volume or less, preferably substantially 0%.

  The molded catalyst according to the present invention produced by such a method can be used for the dehydroaromatization reaction of lower hydrocarbons. In this case, the lower hydrocarbon has 1 to 4 carbon atoms, particularly 1 to 3 carbon atoms.

  In the catalyst molded body, the shape can be various shapes such as a granular shape, a pellet shape, a column shape, and a cylindrical shape.

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The catalytic reactions in the following examples, comparative examples, and reference examples were carried out in a fixed bed flow reactor using a quartz glass reaction tube (inner diameter 8 mm). The product was analyzed by gas chromatography. In addition, the benzene production | generation rate used for evaluation of a catalyst was shown with the amount of substances (nmol-C * sec < ^-1 >) converted into the carbon number of the benzene produced | generated per second.
Example 1
Procedure 1 (Preparation of MoO ₃ supported H-type ZSM-5): Powdered NH ₄ type ZSM-5 (Zeolyst, CBV3324, SiO ₂ / Al ₂ O ₃ ratio = 30, specific surface area = 400 m ² / g) Baking in the air at 500 ° C. for 24 hours gave H-type ZSM-5. Next, 0.380 g of ammonium paramolybdate was dissolved in 150 ml of ion-exchanged water in an eggplant-shaped flask, and 10.0 g of the above H-type ZSM-5 powder was added. The eggplant-shaped flask was attached to a rotary evaporator and evaporated to dryness while rotating and stirring to obtain the ammonium paramolybdate-supporting H-type ZSM-5. Further, this ammonium paramolybdate-supported H-type ZSM-5 was calcined in air at 500 ° C. for 6 hours, and 3 wt% MoO ₃ -supported H-type ZSM-5 (hereinafter abbreviated as 3% MoO ₃ / HZSM-5). Obtained.

Procedure 2 (Mo fixation on H-type ZSM-5): 3% MoO ₃ / HZSM-5 prepared in Procedure 1 was calcined in a methane stream at 650 ° C. for 30 minutes and then at 700 ° C. for 10 minutes and supported. Carbide treatment of MoO ₃ was performed. By this operation, 3% Mo ₂ C-supported H-type ZSM-5 (hereinafter abbreviated as 3% Mo ₂ C / HZSM-5) was obtained.

Procedure 3 (mixing of Mo ₂ C / HZSM-5 and binder): After mixing 3% Mo ₂ C / HZSM-5 prepared up to Procedure 2 and SiO ₂ well in ion-exchanged water at a weight ratio of 1: 1. Evaporate to dryness. Thereafter, granulation molding was performed to obtain a 3% Mo ₂ C / HZSM-5 + SiO ₂ binder catalyst molded body.

Using 300 mg of the 3% Mo ₂ C / HZSM-5 + SiO ₂ binder catalyst molding, methane dehydroaromatization reaction was performed at 700 ° C. The change with time in the benzene production rate is shown in FIG.
Comparative Example 1
After performing the operation of the procedure 1 in Example 1, the operation of the procedure 3 was performed using 3% MoO ₃ / HZSM-5 without performing the operation of the procedure 2, and a 3% MoO ₃ / HZSM-5 + SiO ₂ binder was used. A molded catalyst was obtained.

Using 300 mg of the 3% MoO ₃ / HZSM-5 + SiO ₂ binder catalyst molding, methane dehydrogenation aromatization reaction was carried out at 700 ° C. The change with time in the benzene production rate at that time is shown in FIG.
Reference example 1
The 3% MoO ₃ / HZSM-5 obtained in Procedure 1 of Example 1 was granulated to obtain a 3% MoO ₃ / HZSM-5 catalyst molded body containing no binder component.

Using 150 mg of the 3% MoO ₃ / HZSM-5 catalyst molded body, methane dehydroaromatization reaction was carried out at 700 ° C. The change over time in the benzene production rate is shown in FIG.
Example 2
Procedure 1 (Method for preparing MoO ₃ supported H-type ZSM-5): Supported powdery NH ₄ type ZSM-5 (Zeolyst, CBV3324, SiO ₂ / Al ₂ O ₃ ratio = 30, specific surface area = 400 m ² / g ) Was calcined in air at 500 ° C. for 24 hours to obtain H-type ZSM-5. Next, 1.213 g of ammonium paramolybdate was dissolved in 150 ml of ion-exchanged water in an eggplant-shaped flask, and 10.0 g of the above H-type ZSM-5 powder was added. The eggplant-shaped flask was attached to a rotary evaporator and evaporated to dryness while rotating and stirring to obtain the ammonium paramolybdate-supporting H-type ZSM-5. Further, this ammonium paramolybdate-supported H-type ZSM-5 was calcined in air at 500 ° C. for 6 hours, and 9 wt% MoO ₃ -supported H-type ZSM-5 (hereinafter abbreviated as 9% MoO ₃ / HZSM-5). Obtained.

Procedure 2 (Mo fixation on H-type ZSM-5): 9% MoO ₃ / HZSM-5 prepared in Procedure 1 was calcined in a methane stream at 650 ° C. for 30 minutes and then at 700 ° C. for 10 minutes and supported. Carbide treatment of MoO ₃ was performed. By this operation, 9% Mo ₂ C-supported H-type ZSM-5 (hereinafter abbreviated as 9% Mo ₂ C / HZSM-5) was obtained.

Procedure 3 (mixing of Mo ₂ C / H type ZSM-5 and binder): 9% Mo ₂ C / HZSM-5 and γ-Al ₂ O ₃ prepared in Procedure 2 were ionized at a weight ratio of 1: 1. After mixing well in exchanged water, it was evaporated to dryness. Thereafter, granulation molding was performed to obtain a 9% Mo ₂ C / HZSM-5 + γ-Al ₂ O ₃ binder catalyst molded body.

Using 300 mg of the 9% Mo ₂ C / HZSM-5 + γ-Al ₂ O ₃ binder catalyst molding, methane dehydroaromatization reaction was performed at 700 ° C. FIG. 2 (Δ) shows the change with time in the benzene production rate.
Comparative Example 2
After performing the operation of the procedure 1 in Example 2, the operation of the procedure 3 was performed using 9% MoO ₃ / HZSM-5 without performing the operation of the procedure 2, and 9% MoO ₃ / HZSM-5 + γ-Al _{A 2} O ₃ binder catalyst molding was obtained.

Using 300 mg of the 9% MoO ₃ / HZSM-5 + γ-Al ₂ O ₃ binder catalyst molded body, a dehydroaromatization reaction of methane was carried out at 700 ° C. The change with time of the benzene production rate at that time is shown in FIG.
Reference example 2
The 9% Mo ₂ C / HZSM-5 obtained in the procedure 2 of Example 2 was granulated to obtain a 9% Mo ₂ C / HZSM-5 catalyst molded body containing no binder component.

Using 150 mg of the 9% Mo ₂ C / HZSM-5 molded catalyst, methane dehydroaromatization reaction was performed at 700 ° C. The change over time in the benzene production rate at that time is shown in FIG.

  According to the method of the present invention, since it is possible to prevent the active metal component from being supported on the binder, the dehydration of lower hydrocarbons can be efficiently performed while minimizing the amount of expensive active metal component used. It is possible to produce a molded catalyst body for an aromatization reaction.

Dehydration of methane using the 3 wt% Mo-supported HZSM-5 + SiO ₂ binder catalyst molded body produced by the method of Example 1 and Comparative Example 1 and the 3 wt% Mo-supported HZSM-5 catalyst molded body produced by the method of Reference Example 1 The time-dependent change of the benzene production | generation rate at the time of performing an aromatization reaction is shown. 9% by weight Mo-supported HZSM-5 + γ-Al ₂ O ₃ binder catalyst molded body produced by the method of Example 2 and Comparative Example 2, and 9% by weight Mo-supported HZSM-5 catalyst molded body produced by the method of Reference Example 2 Shows the change over time in the rate of benzene formation during the dehydroaromatization of methane.

Claims (1)

After impregnating the metallosilicate with an aqueous solution or alcohol solution of a precursor containing molybdenum as a catalytically active metal component, firing the molybdenum oxide on the surface of the metallosilicate and carrying out the carbide treatment, and then mixing with the binder component A method for producing a molded catalyst for a dehydroaromatization reaction of a lower hydrocarbon, characterized by molding.

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