JP2022112005A - Dehydrogenation catalyst, pyrolysis tube for olefin production, and olefin production method - Google Patents

Abstract

To realize a dehydrogenation catalyst having high catalytic activity in pyrolysis reaction of hydrocarbon raw material.SOLUTION: A dehydrogenation catalyst (4) is represented by general formula M11-xM2xOy, where M1 is at least one element selected from a first group consisting of Ce, Sr, Ca, La and Ba, where M2 is at least one element selected from a second group consisting of Co, Fe, Cr and Mn, and where x is from 0.01 to 0.5.SELECTED DRAWING: Figure 2

Description

The present invention relates to dehydrogenation catalysts and the like.

Olefins such as ethylene and propylene are used in industry to produce chemical compositions for a wide variety of applications. Olefins are produced by flowing petroleum-derived hydrocarbons such as ethane and naphtha into cracking tubes, heating them to 700 to 900° C., and thermally decomposing them in the gas phase. The manufacturing method described above requires a large amount of energy to raise the temperature. Therefore, a technique of supporting a dehydrogenation catalyst on the inner surface of the pyrolysis tube is known.

Patent Document 1 discloses that at least one of the group consisting of oxides of group 2B metal elements, oxides of group 3B metal elements, and oxides of group 4B metal elements of the periodic table is used as a catalyst component. A dehydrogenation catalyst is disclosed comprising:

JP 2017-209661 A

However, the dehydrogenation catalyst described in Patent Document 1 may not provide sufficient performance depending on the olefin production conditions, and further development of dehydrogenation catalysts is desired.

One aspect of the present invention has been made in view of the above problems, and an object thereof is to provide a dehydrogenation catalyst having high catalytic performance in the thermal cracking reaction of hydrocarbon feedstocks.

In order to solve the above problems, a dehydrogenation catalyst according to one aspect of the present invention is represented by the general formula M1 _1-x M2 _x O _y , wherein M1 is Ce, Sr, Ca, La, and At least one element selected from the first group consisting of Ba, M2 is at least one element selected from the second group consisting of Co, Fe, Cr, and Mn, and x is , 0.01 to 0.5.

ADVANTAGE OF THE INVENTION According to one aspect of the present invention, it is possible to realize a dehydrogenation catalyst having a high catalytic ability in a thermal cracking reaction of a hydrocarbon feedstock.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing the configuration of a thermal cracking tube for producing olefins according to Embodiment 1 of the present invention; Fig. 3 is an enlarged view of the inner surface of the pyrolysis tube for producing olefin. Fig. 2 is a schematic cross-sectional view showing the configuration of a pyrolysis tube for producing olefins according to Embodiment 2 of the present invention. Fig. 3 is an enlarged view of the inner surface of the pyrolysis tube for producing olefin. 1 is a graph showing the production rate of ethylene when a thermal cracking experiment was conducted using the dehydrogenation catalysts of Examples and Comparative Examples of the present invention. 1 is a graph prepared using data obtained from thermal decomposition experiments using dehydrogenation catalysts of Examples and Comparative Examples of the present invention, in which the horizontal axis represents the conversion of ethane and the vertical axis represents the selectivity of ethylene. It is a graph that 1 is a graph showing the production rate of ethylene when a thermal cracking experiment was conducted using the dehydrogenation catalysts of Examples and Comparative Examples of the present invention. 1 is a graph prepared using data obtained from thermal decomposition experiments using dehydrogenation catalysts of Examples and Comparative Examples of the present invention, in which the horizontal axis represents the conversion of ethane and the vertical axis represents the selectivity of ethylene. It is a graph that

[Embodiment 1]
Hereinafter, the thermal cracking tube 1A for olefin production and the dehydrogenation catalyst 4 in Embodiment 1 of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of an olefin-producing thermal cracking tube 1A according to the present embodiment. FIG. 2 is an enlarged view of the inner surface of the thermal cracking tube 1A for olefin production.

As shown in FIGS. 1 and 2, the olefin-producing pyrolysis tube 1A has an alumina film 3 formed on the inner surfaces of a tubular base material 2 and a plate-like body (insert material) 5 . The base material 2 and the plate-like body 5 are made of a heat-resistant metal material. The alumina coating 3 is a metal oxide coating containing Al ₂ O ₃ . A dehydrogenation catalyst 4 is carried on the surface of the alumina film 3 . In addition, in this application, a metal oxide film containing Al ₂ O ₃ is called an “alumina film”. With the above configuration, the pyrolysis tube 1A for producing olefins can improve the yield of olefins from hydrocarbon feedstocks such as ethane and naphtha by adding dehydrogenation catalytic reaction to the pyrolysis reaction. . Below, the base material 2, the plate-like body 5, the alumina coating 3, and the dehydrogenation catalyst 4 in the thermal cracking tube 1A for olefin production are explained in detail.

(base material 2 and plate-like body 5)
The base material 2 in this embodiment is a casting made of a heat-resistant metal material with an alumina film 3 formed on the surface of the base material 2 . The plate-like body 5 in this embodiment is provided inside the base material 2 and is a casting made of a heat-resistant metal material or a stainless steel plate with an alumina film 3 formed on the surface of the plate-like body 5 . In this embodiment, the thermal cracking tube 1A for olefin production includes the plate-like body 5, but the plate-like body 5 is not an essential member, and the plate-like body 5 may be omitted. The base material 2 and the plate-like body 5 may be, for example, a casting of a conventionally known heat-resistant metal material, and a heat-resistant material containing at least chromium (Cr), nickel (Ni), and aluminum (Al). It is preferably a casting made of metal material.

In this embodiment, the alumina coating 3 is formed on the inner surface of the base material 2 and the surface of the plate-like body 5, but the alumina coating 3 may be formed only on the inner surface of the base material 2, or the plate The alumina coating 3 may be formed only on the surface of the shaped body 5 . Further, in the present embodiment, the dehydrogenation catalyst 4 is supported on the inner surface of the base material 2 and the surface of the plate-like body 5, but the dehydrogenation catalyst 4 is supported only on the inner surface of the base material 2. Alternatively, the dehydrogenation catalyst 4 may be supported only on the surface of the plate-like body 5 .

At least a part of the inner surface of the base material 2 and/or the surface of the plate-like body 5 preferably constitutes concave portions and/or convex portions. As a result, the heat transfer efficiency can be improved, and the fluid inside the tubular base material 2 can be uniformly heated.

(Alumina coating 3)
The alumina coating 3 is highly dense and acts as a barrier to prevent oxygen, carbon, and nitrogen from entering the base material 2 and the plate-like body 5 from the outside. In a general pyrolysis tube for olefin production, a metal oxide film is not formed on the inner surface of the base material 2 and the surface of the plate-like body 5 . Therefore, the catalytic action of nickel (Ni), iron (Fe), cobalt (Co), and the like, which are constituent elements of the surfaces of the base material 2 and the plate-like body 5, causes excessive decomposition of the hydrocarbon raw material during thermal decomposition. 2 and the surface of the plate-like body 5 coke is produced. When the coke generated on the inner surface of the base material 2 and the surface of the plate-like body 5 accumulates, the heat transfer resistance increases, and in order to maintain the reaction temperature in the olefin pyrolysis tube, the outer surface of the pyrolysis tube for olefin production There was a problem that the temperature of the In addition, when cork accumulates on the inner surface of the base material 2 and the surface of the plate-like body 5, the cross-sectional area of the flow path through which the gas passes becomes small, resulting in an increase in pressure loss. For these reasons, typical olefin production pyrolysis tubes have required frequent decoking of the deposited coke.

On the other hand, in the olefin-producing pyrolysis tube 1A of the present embodiment, the alumina film 3 is formed on the inner surface of the base material 2 and the surface of the plate-like body 5, so that the inner surface of the base material 2 and the plate The formation of coke on the surface of the shaped body 5 can be suppressed. As a result, the frequency of decoding can be reduced.

The alumina coating 3 of the present invention is formed by a surface treatment step and a first heat treatment step. The surface treatment step is a step of applying a surface treatment to target portions of the base material 2 and plate-like body 5 that come into contact with a high-temperature atmosphere during use of the product, and adjusting the surface roughness of the portions. The surface treatment of the base material 2 and the plate-like body 5 can be exemplified by polishing treatment. The surface treatment can be carried out so that the surface roughness (Ra) of the target portion is 0.05 to 2.5 μm. More desirably, the surface roughness (Ra) is 0.5-2.0 μm. At this time, by adjusting the surface roughness by surface treatment, residual stress and strain in the heat affected zone can be removed at the same time.

The first heat treatment step is a step of heat-treating the base material 2 and the plate-like body 5 after the surface treatment step in an oxidizing atmosphere. The oxidizing atmosphere is an oxidizing gas containing 20% by volume or more of oxygen, or an oxidizing environment mixed with steam or _CO2 . The heat treatment is performed at a temperature of 900° C. or higher, preferably 1000° C. or higher, and the heating time is 1 hour or longer.

By sequentially performing the surface treatment step and the first heat treatment step on the base material 2 and the plate-like body 5 as described above, the alumina coating 3 is stably formed on the inner surface of the base material 2 and the surface of the plate-like body 5. It is possible to manufacture thermal cracking tubes for olefin production.

The thickness of the alumina coating 3 formed on the inner surface of the base material 2 and the surface of the plate-like body 5 is preferably 0.5 μm or more and 6 μm or less in order to effectively exhibit the barrier function. . If the thickness of the alumina coating 3 is less than 0.5 μm, the carburization resistance may deteriorate. If the thickness of the alumina coating 3 exceeds 6 μm, the alumina coating 3 may easily peel off due to the difference in thermal expansion coefficient between the base material 2 and plate-like body 5 and the coating. From the above, it is more preferable to set the thickness of the alumina coating 3 to 0.5 μm or more and 2.5 μm or less.

A chromium oxide scale may be partially formed on the alumina coating 3 . The reason is that the chromium oxide scale formed near the surface of the base material 2 and the plate-like body 5 is pushed up to the surface of the product by Al ₂ O ₃ . This _{chromium oxide} scale should be as small as possible.

(Dehydrogenation catalyst 4)
The dehydrogenation catalyst 4 is a dehydrogenation catalyst used for olefin production. The dehydrogenation catalyst 4 is used to improve the yield of olefins in the thermal cracking reaction (specifically, the reaction of thermally cracking hydrocarbon feedstocks such as naphtha and ethane into olefins) using the olefin production pyrolysis tube 1A. and is supported on the surface of the alumina film 3 .

The dehydrogenation catalyst 4 contains at least one element selected from the first group consisting of Ce, Sr, Ca, La, and Ba (hereinafter also referred to as the first group element), Co, Fe, Cr , and at least one element selected from the second group consisting of Mn (hereinafter also referred to as a second group element). In the dehydrogenation catalyst 4, the total molar ratio of the group 2 elements is 0 when the total molar ratio of the group 1 elements and the total molar ratio of the group 2 elements is 1. 0.01 to 0.5. By having this configuration, the dehydrogenation catalyst 4 can easily take oxygen in and out of the structure. As a result, the dehydrogenation reaction of the hydrocarbon feedstock can be promoted, and thus the catalyst has a high catalytic ability in the dehydrogenation reaction.

The dehydrogenation catalyst 4 can also be expressed as follows. That is, the dehydrogenation catalyst 4 is represented by the general formula M1 _1-x M2 _x O _y , and M1 is at least one selected from the first group consisting of Ce, Sr, Ca, La, and Ba. M2 is at least one element selected from the second group consisting of Co, Fe, Cr and Mn, and x is 0.01 to 0.5. The lower limit of x is preferably 0.1. Also, the upper limit of x is preferably 0.4, more preferably 0.2. The value of y is a value determined by the first group element and the second group element.

In the dehydrogenation catalyst 4, it is preferable that the element selected from the first group is Ce and the element selected from the second group is Co. By having this configuration, the catalytic ability in the dehydrogenation reaction is further improved. In the case of this structure, the molar ratio of Co is preferably 0.1 to 0.4 when the sum of the molar ratio of Ce and the molar ratio of Co is 1. In this case, the dehydrogenation catalyst 4 can be represented as Ce _1-x Co _x O ₂ (where x is 0.1-0.4).

<Method for producing dehydrogenation catalyst 4>
The method for producing the dehydrogenation catalyst 4 is not particularly limited, but it can be produced by, for example, a citric acid complex polymerization method, a solid phase method, or the like. A method for producing the dehydrogenation catalyst 4 using the citric acid complex polymerization method and the solid phase method will be described below.

(Citrate complex polymerization method)
The citric acid complex polymerization method includes a mixing/stirring step, a drying step, a preliminary baking step, and a final baking step.

In the mixing and stirring step, a mixed solution is obtained by mixing a salt (for example, nitrate, acetate, etc.) containing elements constituting the dehydrogenation catalyst 4, citric acid monohydrate, ethylene glycol, and distilled water. . The salt is weighed to give the desired molar ratio of Group 1 and Group 2 elements. Citric acid monohydrate is preferably added in an amount of 3 to 4 times the total molar amount of the group 1 elements and group 2 elements contained in the salt. Ethylene glycol is preferably added in an amount of 3 to 4 times the total molar amount of the first group element and the second group element contained in the salt. Distilled water is preferably added in an amount of 1200 to 1600 times the total molar amount of the group 1 elements and group 2 elements contained in the salt. The mixture is preferably stirred at 60-70° C. for 10-17 hours.

In the drying step, the mixed liquid is dried to obtain powder. For example, drying may be performed by heating while stirring on a hot plate.

In the calcination step, the powder is calcined to obtain a calcined body. The calcination step is preferably performed in the air or in oxygen, with a calcination temperature of 400 to 450° C. and a holding time of 2 to 3 hours. The calcination temperature and holding time may be appropriately adjusted within the above ranges depending on the amount of the catalyst to be prepared.

In the final firing step, the pre-fired body is fully fired to obtain an oxide. The calcination step is preferably carried out in the air or in oxygen, with a calcination temperature of 850 to 900° C. and a holding time of 8 to 12 hours. The calcination temperature and holding time may be appropriately adjusted within the above ranges depending on the amount of catalyst to be prepared.

(Solid phase method)
The solid phase method includes grinding and mixing steps, drying steps, and calcination steps.

In the pulverizing and mixing step, a compound (for example, an oxide or a carbonate compound) containing elements constituting the dehydrogenation catalyst 4 is mixed, and the mixture is pulverized and mixed to obtain pulverized and mixed powder. The compound is mixed so that the first group element and the second group element are in the desired molar ratio. For example, pulverization and mixing may be performed using a wet bead mill.

In the drying step, the pulverized and mixed powder is dried to obtain a dry body. In the firing step, the dried body is fired to obtain an oxide. The firing process is preferably carried out in air or in oxygen at a firing temperature of 500 to 1300° C. and a holding time of 1 to 10 hours. The calcination temperature and holding time may be appropriately adjusted within the above ranges depending on the amount of catalyst to be prepared.

<Method of Supporting Dehydrogenation Catalyst 4>
Next, a method for supporting the dehydrogenation catalyst 4 on the alumina coating 3 will be described. A method for supporting the dehydrogenation catalyst 4 on the alumina coating 3 includes a coating step and a second heat treatment step. The coating step and the second heat treatment step will be described in detail below.

(a) Coating Step The coating step is a step of coating the surface of the alumina coating 3 formed by the surface treatment step and the first heat treatment step with slurry containing the dehydrogenation catalyst 4 produced in advance.

(b) Second Heat Treatment Step The second heat treatment step is a step of heat-treating the base material 2 and the plate-like body 5 with the alumina coating 3 coated with the slurry in the coating step.

The heat treatment in the second heat treatment step is performed in air or in an acidic atmosphere. The heat treatment temperature in the second heat treatment step is in the range of 500-900° C., and the heat treatment time is 1-6 hours.

The dehydrogenation catalyst 4 can be supported on the alumina coating 3 by performing the second heat treatment step under the above heat treatment conditions.

The dehydrogenation catalyst 4 can be carried on the alumina coating 3 at an appropriate concentration (amount) by adjusting the concentration of the slurry applied in the coating step.

Thus, in the olefin-producing pyrolysis tube 1A of the present embodiment, the alumina film 3 is formed on the inner surface of the tubular base material 2 and the surface of the plate-like body 5 made of a heat-resistant metal material. A dehydrogenation catalyst 4 is carried on the surface of the film 3 .

According to the above structure, the alumina film 3 is formed on the inner surface of the base material 2 and the surface of the plate-like body 5 in the thermal cracking tube 1A for olefin production of the present invention. Therefore, it is possible to suppress the formation of coke on the surface of the alumina coating 3 (the base material 2 and the plate-like body 5). A dehydrogenation catalyst 4 is carried on the surface of this alumina film 3 . As a result, when the dehydrogenation catalyst 4 acts as a dehydrogenation catalyst in thermal cracking using the olefin-producing pyrolysis tube 1A, ethylene can be produced, for example, from ethane by a dehydrogenation reaction. As a result, it has become possible to improve the yield of olefins from hydrocarbon feedstocks such as ethane and naphtha by thermal cracking.

Further, in the present embodiment, the coating step and the second heat treatment step are performed on the alumina coating 3 formed on the inner surface of the base material 2 and the surface of the plate-like body 5 by the surface treatment step and the first heat treatment step. , the dehydrogenation catalyst 4 was carried on the alumina film 3, but the thermal cracking tube for olefin production of the present invention is not limited to this. For example, after performing the surface treatment process, the coating process and the heat treatment process may be performed. In this case, in the heat treatment step, the alumina coating 3 is formed on the inner surface of the base material 2 and the surface of the plate-like body 5 , and the dehydrogenation catalyst 4 is supported on the alumina coating 3 . As a result, the alumina coating 3 can be formed on the inner surface of the base material 2 and the surface of the plate-like body 5 and the dehydrogenation catalyst 4 can be supported on the alumina coating 3 by performing the heat treatment process only once.

Further, in the present embodiment, the dehydrogenation catalyst 4 is supported on the inner surface of the base material 2 and the surface of the alumina coating 3 formed on the surface of the plate-like body 5. 1 A of thermal cracking tubes for olefin manufacture are not restricted to this. That is, the pyrolysis tube for olefin production of the present invention has a barrier function and can support the dehydrogenation catalyst 4, and has a metal oxide film different from Al ₂ O ₃ (e.g., Cr ₂ O ₃ , MnCr ₂ O ₄ etc.), the dehydrogenation catalyst 4 may be supported on the surface.

A method for producing an olefin according to one aspect of the present invention is a method for producing an olefin using the thermal cracking tube 1A for producing an olefin described above. Examples of olefins include ethylene and propylene. Examples of hydrocarbon raw materials include ethane and naphtha. Olefins are produced by flowing a hydrocarbon feedstock into the olefin production pyrolysis tube 1A, heating it to 700 to 900° C., and thermally decomposing it in the gas phase.

[Embodiment 2]
Other embodiments of the invention are described below. For convenience of description, members having the same functions as those of the members described in the above embodiments are denoted by the same reference numerals, and description thereof will not be repeated.

FIG. 3 is a schematic cross-sectional view showing the structure of the thermal cracking tube 1B for olefin production in this embodiment. FIG. 4 is an enlarged view of the inner surface of the thermal cracking tube 1B for olefin production.

In the olefin-producing pyrolysis tube 1A according to Embodiment 1, an alumina film 3 as a metal oxide film containing Al ₂ O ₃ is formed on the inner surface of the base material 2 and the surface of the plate-like body 5. A dehydrogenation catalyst 4 was supported on the surface of the film 3 . On the other hand, in the thermal cracking tube 1B for olefin production in this embodiment, as shown in FIGS. It differs from the thermal cracking tube 1A for olefin production in that a direct dehydrogenation catalyst 4 is supported.

In the olefin production pyrolysis tube 1B, slurry containing a pre-manufactured dehydrogenation catalyst 4 is applied to the inner surface of the base material 2 and the surface of the plate-like body 5, and heat-treated under appropriate conditions such as air or nitrogen atmosphere. The dehydrogenation catalyst 4 can be produced by carrying the dehydrogenation catalyst 4 on the inner surface of the base material 2 and on the surface of the plate-like body 5 .

As described above, the dehydrogenation catalyst 4 is supported on the inner surface of the base material 2 and the surface of the plate-like body 5 in the thermal cracking tube 1B for olefin production. As a result, when the dehydrogenation catalyst 4 acts as a dehydrogenation catalyst in thermal cracking using the olefin-producing pyrolysis tube 1B, ethylene can be produced, for example, from ethane by a dehydrogenation reaction. As a result, it has become possible to improve the yield of olefins from hydrocarbon feedstocks such as ethane and naphtha by thermal cracking.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

The dehydrogenation catalysts of Examples 1 to 8 as examples of the dehydrogenation catalyst of the present invention and the dehydrogenation catalyst of Comparative Example 1 as a comparative example will be described below. First, the method for producing the dehydrogenation catalysts of Examples 1 to 8 and Comparative Example 1 will be described below.

(Example 1)
The dehydrogenation catalyst of Example 1 was produced by a citric acid complex polymerization method. Specifically, first, cerium nitrate hexahydrate (Ce(NO ₃ ) ₃ .6H ₂ O) and chromium nitrate (Cr(NO ₃ ) ₃ ) were mixed with Ce:Cr=0.9:0.1 molar A solute was obtained by weighing so as to obtain a ratio. Three times the molar amount of citric acid monohydrate and ethylene glycol with respect to the total molar amount of Ce and Cr in the solute was dissolved in distilled water with a molar amount of 1500 times with respect to the total molar amount, and sufficiently Stirred (hereinafter referred to as solvent). The solute was mixed with the solvent and heated and stirred at 70° C. overnight. After that, it was heated and dried on a pot plate while being stirred to obtain a powder. The powder was calcined at 400° C. for 2 hours, and further calcined at 850° C. for 10 hours to obtain Ce _0.9 Cr 0.9 as the dehydrogenation catalyst of Example 1 _{. 1} O ₂ was made.

(Example 2)
Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) and manganese nitrate hexahydrate (Mn(NO ₃ ) _{2.6H 2 O} ) were mixed with Ce:Mn=0.9:0.1. Ce _0.9 Mn _0.1 O ₂ as a dehydrogenation catalyst of Example 2 was produced in the same manner as in Example 1, except that the solutes were weighed so as to have a molar ratio.

(Example 3)
Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) and iron nitrate (Fe(NO ₃ ) ₃ ) were weighed so that the molar ratio of Ce:Fe = 0.9:0.1. Ce _0.9 Fe _0.1 O ₂ as a dehydrogenation catalyst of Example 3 was prepared in the same manner as in Example 1, except that the solute was used as a solute.

(Example 4)
Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) and cobalt nitrate (Co(NO ₃ ) ₂ ) were weighed so that the molar ratio of Ce:Co = 0.9:0.1. Ce _0.9 Co _0.1 O ₂ as a dehydrogenation catalyst of Example 4 was prepared in the same manner as in Example 1 except that the solute was used as a solute.

(Example 5)
Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) and nickel nitrate hexahydrate (Ni(NO ₃ ) _{2.6H 2 O} ) were mixed with Ce:Ni=0.9:0.1. Ce _0.9 Ni _0.1 O ₂ as a dehydrogenation catalyst of Example 5 was produced in the same manner as in Example 1, except that the solutes were weighed so as to have a molar ratio.

(Example 6)
Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) and cobalt nitrate (Co(NO ₃ ) ₂ ) Weighed so that the molar ratio of Ce:Fe = 0.8:0.2 Ce _0.8 Co _0.2 O ₂ as a dehydrogenation catalyst of Example 6 was prepared in the same manner as in Example 1 except that the solute was used.

(Example 7)
Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) and cobalt nitrate (Co(NO ₃ ) ₂ ) Weighed so that the molar ratio of Ce:Fe = 0.7:0.3 Ce _0.7 Co _0.3 O ₂ as a dehydrogenation catalyst of Example 7 was produced in the same manner as in Example 1 except that the solute was used.

(Example 8)
Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) and cobalt nitrate (Co(NO ₃ ) ₂ ) Weighed so that the molar ratio of Ce:Fe = 0.6:0.4 Ce _0.6 Co _0.4 O ₂ as a dehydrogenation catalyst of Example 8 was prepared in the same manner as in Example 1 except that the solute was used.

(Comparative example 1)
A dehydrogenation catalyst of Comparative Example 1 was produced by a citric acid complex polymerization method. Cerium nitrate hexahydrate (Ce(NO ₃ ) _{3.6H 2} O) is used as a solute, and citric acid monohydrate and ethylene glycol are added in a molar amount three times the total molar amount of Ce in the solute. It was dissolved in 1500-fold molar amount of distilled water with respect to the total molar amount and sufficiently stirred (hereinafter referred to as a solvent). The solute was mixed with the solvent and heated and stirred at 70° C. overnight. After that, it was heated and dried on a pot plate with stirring to obtain a powder. The powder was calcined at 400° C. for 2 hours, and further calcined at 850° C. for 10 hours to produce CeO ₂ .

<Ethane pyrolysis experiment>
Next, ethane pyrolysis experiments performed using the dehydrogenation catalysts of Examples 1 to 5 and Comparative Example 1 will be described. In the ethane pyrolysis experiment, first, a mixture of 100 mg of dehydrogenation catalyst and 392 mg of inert solid SiC was filled in a quartz tube (inner diameter: 4 mm, length: 180 mm) to a height of 30 mm. Next, the quartz tube was inserted into the tubular furnace, and the temperature inside the tubular furnace was raised to 600°C. Next, a raw material gas adjusted to a volume ratio of ethane (C ₂ H ₆ ):water vapor (H ₂ O):nitrogen (N ₂ )=1.0:1.4:5.6 was supplied at 118 mL/min. was supplied to the quartz tube at a flow rate of , and the thermal decomposition reaction of ethane was performed. Hydrogen (H ₂ ) and nitrogen (N ₂ ) out of the gases flowing out from the quartz tube were analyzed with a TCG gas chromatograph (Shimadzu, GC-8A). Among the gases flowing out of the quartz tube, ethane (C ₂ H ₆ ), ethylene (C ₂ H ₄ ), carbon monoxide (CO), and methane (CH ₄ ) were detected using an FID gas chromatograph (Shimadzu) equipped with a methanizer. , GC-8A). From these analysis results, the production rate of ethylene (C ₂ H ₄ ), the conversion rate of ethane (C ₃ H ₆ ), and the selectivity of ethylene (C ₂ H ₄ ) were calculated.

FIG. 5 is a graph showing the production rate of ethylene when a thermal cracking experiment was conducted using the dehydrogenation catalysts of Examples 1 to 5 and Comparative Example 1. FIG. FIG. 6 is a graph prepared using data obtained from thermal decomposition experiments using the dehydrogenation catalysts of Examples 1 to 4 and Comparative Example 1. The horizontal axis represents the conversion rate of ethane, and the selection of ethylene. It is a graph which has a rate as a vertical axis. 5 and 6 show pyrolysis experiments using a dehydrogenation catalyst represented by Ce _0.9 M _0.1 O ₂ (M is a group 2 element) and the dehydrogenation catalyst of Comparative Example 1. It is a graph created using the data obtained by.

As shown in FIG. 5, when the dehydrogenation catalysts of Examples 1 to 5 containing Ce and a second group element were used, the dehydrogenation catalyst of Comparative Example 1 containing no second group element was used. The production rate of ethylene was higher than in the case of In particular, the production rate of ethylene was the highest when the dehydrogenation catalyst of Example 4 containing Co was used.

As shown in FIG. 6, when the dehydrogenation catalysts of Examples 1 to 5 containing Ce and the second group element were used, the dehydrogenation catalyst of Comparative Example 1 containing no second group element was used. The conversion of ethane was higher than in the case of In addition, when the dehydrogenation catalysts of Examples 2 to 4 containing Mn, Fe or Co as the second group element were used, the selectivity of ethylene was higher than when the dehydrogenation catalyst of Comparative Example 1 was used. was high.

FIG. 7 is a graph showing the production rate of ethylene when a thermal cracking experiment was conducted using the dehydrogenation catalysts of Examples 4, 6 to 8 and Comparative Example 1. FIG. FIG. 8 is a graph prepared using data obtained from thermal decomposition experiments using the dehydrogenation catalysts of Examples 4, 6 to 8 and Comparative Example 1, in which the horizontal axis represents the conversion rate of ethane and the is a graph with the vertical axis representing the selectivity of 7 and 8 are prepared using data obtained by conducting thermal decomposition experiments using the dehydrogenation catalyst represented by Ce _1-x Co _x O ₂ and the dehydrogenation catalyst of Comparative Example 1. is a graph.

As shown in FIG. 7, when the dehydrogenation catalysts of Examples 4 and 6 to 8 containing Ce and Co were used, compared with the case of using the dehydrogenation catalyst CeO ₂ of Comparative Example 1, ethylene production rate was high. In particular, the rate of ethylene production was highest when the dehydrogenation catalyst of Example 6, Ce _0.8 Co _0.2 O ₂ , was used.

As shown in FIG. 8, when the dehydrogenation catalysts of Examples 4 and 6 to 8 containing Ce and Co were used, compared with the case of using the dehydrogenation catalyst CeO ₂ of Comparative Example 1, Both ethane conversion and ethylene selectivity were high. In particular, when the dehydrogenation catalyst Ce _0.8 Co _0.2 O ₂ of Example 6 was used, the conversion of ethane and the selectivity of ethylene were the highest.

1A, 1B Pyrolysis tube for olefin production 2 Base material 3 Alumina film (metal oxide film)
4 dehydrogenation catalyst 5 plate

Claims (5)

represented by the general formula M1 _1-x M2 _x O _y ,
M1 is at least one element selected from the first group consisting of Ce, Sr, Ca, La, and Ba,
M2 is at least one element selected from the second group consisting of Co, Fe, Cr, and Mn,
The dehydrogenation catalyst, wherein x is from 0.01 to 0.5. The element selected from the first group is Ce,
2. A dehydrogenation catalyst according to claim 1, wherein the element selected from the second group is Co. 3. The dehydrogenation catalyst according to claim 2, wherein x is 0.1 to 0.4. The dehydrogenation catalyst according to any one of claims 1 to 3 is supported on the inner surface of a tubular base material made of a heat-resistant metal material and/or on the surface of a plate-shaped body made of a heat-resistant metal material. Pyrolysis tubes for olefin production. A method for producing olefins, comprising producing olefins using the thermal cracking tube for producing olefins according to claim 4 .

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