JP2003012570A - Method for producing lower alkene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for industrially advantageously producing a lower alkene at a heightened reaction rate by using a catalyst having excellent catalytic activity in the method for producing the lower alkene by bringing a lower alkane into contact with the catalyst. SOLUTION: A ZSM-5 zeolite is used as a catalyst carrier in the method for producing the lower alkene by dehydrogenating the lower alkane in the presence of the catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a lower alkene such as ethylene from a lower alkane such as ethane.

[0002]

2. Description of the Related Art Lower olefins represented by ethylene are one of the important intermediate products in the petrochemical industry. Industrially, hydrocarbons such as ethane, propane, butane, naphtha and gas oil are used as raw materials and steam. It is also manufactured by thermal decomposition with no catalyst. On the other hand, in recent years, a method for producing ethylene by contacting ethane with a catalyst such as a metal oxide such as chromium has been studied, but in the studies so far, sufficient catalytic activity and reaction rate have not been obtained. (Applied Catalysis A: General 196 (2000)
1-8). Further, generally, in the dehydrogenation reaction, there is also a problem that carbonaceous materials generated by decomposition of the raw materials and the like are generated on the surface of the catalyst, thereby covering active sites and gradually decreasing activity.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The present invention has been made in order to solve these problems. In the method for producing a lower alkene by contacting a lower alkane with a catalyst, the catalyst has further excellent catalytic ability. It is an object of the present invention to provide a method capable of industrially advantageously producing a lower alkene at an increased reaction rate using the above catalyst.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that ZS
We found that M-5 zeolite is effective and completed the present invention. That is, according to the present invention, firstly,
In a method for producing a lower alkene by dehydrogenating a lower alkane in the presence of a catalyst, there is provided a method for producing a lower alkene, which comprises using ZSM-5 zeolite as a catalyst carrier. Secondly, in the first invention, the catalyst contains at least one metal oxide selected from the groups Va, VIa, VIII and IIIa (excluding boron and aluminum) of the periodic table. A method for producing a lower alkene is provided. Third, in the first or second invention, the periodic table Nos. Va, VIa, VIII and IIIa
At least one metal oxide selected from the group (excluding boron and aluminum) is a chromium oxide, a vanadium oxide, or a gallium oxide. Fourthly, in any one of the first to third inventions, the catalyst is Va, VIa, VIII of the periodic table.
And a method of producing a lower alkene, which comprises at least one metal oxide selected from the group IIIa (excluding boron and aluminum) and an alkali metal. Fifthly, there is provided a method for producing a lower alkene according to any one of the first to fourth inventions, wherein dehydrogenation is carried out in the presence of a carbon dioxide-containing gas. Sixth, in the invention according to any one of the first to fifth aspects, there is provided a method for producing a lower alkene, characterized in that the lower alkane is ethane and the lower alkene is ethylene.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, ZS is used as a catalyst carrier.
M-5 zeolite is used. This ZSM-5 zeolite is an aluminosilicate that has an MFI structure if it is shown with a symbol indicating the crystal structure established by the International Zeolite Association (IZA), and is Na _n [Al _n Si _96-n O ₁₉₂ ] .xH ₂ O Expressed as
The theoretically possible value of n is n <27 (Ono, Yashima, "Science and Engineering of Zeolites", Kodansha Scientific, page 7), but it is not particularly limited as long as this condition is satisfied, but preferably SiO ₂ / Al ₂ O ₃ ≧ 25 (n ≦ 1.9) Particularly preferably SiO ₂ / Al ₂ O ₃ ≧ 100 (n ≦ 0.48). Same as ZSM-5
Alumina-free silicalite-1 having an MFI structure and n = 0 in the above formula is also included in the range.

Exchangeable cations when used as carriers
(Corresponding to Na in the above formula) is determined by a method such as ion exchange.
It is desirable to use an alkali metal represented by H or Na. In addition, various methods of dealumination treatment are known to increase the silica / alumina ratio, but extra-framework aluminum generated by this treatment may not be completely removed and may remain on the catalyst surface to some extent. Absent. The particle size is not particularly limited, but is preferably 10 μm to 10
It is 00 μm. Further, in order to facilitate handling of the catalyst and provide mechanical strength, the particulate catalyst may be molded into a pellet shape. In this case, the size and shape of the pellet are not limited. At this time, a molding aid such as a clay-based inorganic compound may be mixed with the catalyst in order to improve the processability into pellets. The surface area of the catalyst is not particularly limited. It is preferably 100 to 500 m ² / g.

In the catalyst according to the present invention, as the active metal supported on the ZSM-5 zeolite as a carrier, all active metals known as a catalyst for dehydrogenating a lower alkane can be used. Examples of such a catalyst include Va, VIa, VII of the periodic table.
Examples thereof include those containing at least one metal oxide selected from the groups I and IIIa (excluding boron and aluminum). Specific examples include vanadium, niobium, tantalum, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, gallium, indium and thallium. These catalysts can be used alone or as a mixture of two or more kinds.

Among these, oxidation of chromium, gallium, and vanadium is taken into consideration from the viewpoints of manifestation of catalytic ability, specifically, persistence of catalytic activity, high reaction rate, easy catalyst preparation, low raw material cost, and the like. The thing is used preferably. The oxidation state of the above-mentioned metal oxide is not particularly limited, and it is 2 in chromium.
It may be in a wide oxidation state such as valence to 6 valence, gallium to 2 valence to 3 valence, and vanadium to 2 valence to 5 valence. The crystal structure is not particularly limited, and may be amorphous.

Further, the components contained in the catalyst used in the present invention are not necessarily limited to the above metal oxides, and other catalyst components, such as products, may be appropriately added for the purpose of enhancing the selectivity of the products of the catalyst. It is desirable to mix or add an alkali metal component such as sodium nitrate for enhancing the selectivity and a component such as a clay inorganic compound for enhancing the mechanical strength of the catalyst particles.

The catalyst according to the present invention contains the above metal oxide in ZSM-
5 Obtained by supporting on a zeolite catalyst carrier. Examples of the method for supporting the catalyst include conventionally known methods such as an impregnation method, an ion exchange method, and a precipitation method. The supporting method is not limited to the above examples. The ratio of metal oxide to the catalyst carrier (supporting ratio) is not particularly limited, but is 0.1.
The weight range is preferably from 30 to 30% by weight, particularly preferably from 2 to 10% by weight. If the loading rate is too low, the desired catalytic activity cannot be obtained, and if the loading rate is too high,
There arise problems such as an increase in raw material cost of the metal oxide, progress of undesired side reactions, and difficulty in obtaining a preferable effect of the carrier.

In order to prepare the ZSM-5 zeolite-supported metal oxide catalyst of the present invention, the precursor such as chromium nitrate is supported on ZSM-5 zeolite and then heated and calcined,
The precursor such as chromium nitrate may be made in an oxide state. The atmosphere at the time of heating and firing includes, but is not limited to, air and oxygen. The firing temperature is not particularly limited, but a desirable temperature is 500 to 800 ° C. The heating time is not particularly limited, but is preferably 10 minutes to 10 minutes.
It's time. The crystal structure of the metal oxide supported on ZSM-5 zeolite with the obtained catalyst is not particularly limited. It may have a specific crystal structure as a complex oxide or may be amorphous.

Further, this catalyst can be regenerated by heating it in air or oxygen after the activity is lowered. The heating temperature during regeneration is preferably 300 ° C or higher, more preferably 500 to 800 ° C, and the heating time is not particularly limited, but is preferably 10 minutes to 10 hours.

The reaction raw material to be dehydrogenated used in the present invention is a lower alkane such as ethane, propane and butane, and ethane is particularly preferably used.

The dehydrogenation reaction of the lower alkane of the present invention is preferably carried out in the presence of a carbon dioxide-containing gas. The carbon dioxide-containing gas may be carbon dioxide gas alone or may be mixed with another coexisting gas.

The coexisting gas is air, nitrogen, carbon dioxide, an inert gas such as helium / argon, oxygen, carbon monoxide, water vapor, or a gas selected from at least one of combustion exhaust gas from a thermal power plant and the like. Can be mentioned. Particularly preferred are inert gas and nitrogen, but are not limited thereto, and are not limited to the above examples.

It is more desirable that the carbon dioxide-containing gas used in the present invention does not contain environmental pollutants such as NOx and SOx, but the treatment for removing these pollutants is not always necessary. The amount of carbon dioxide-containing gas used is 0.1 to 100 mol, preferably 1 to 20 mol, per 1 mol of lower alkane.

In the present invention, the reaction temperature is not particularly limited, but it is in the range of 300 to 800 ° C., preferably 450 to 800 ° C.
650 ° C. If the reaction temperature is too high, the selectivity to the target product will decrease and carbon will be significantly deposited on the catalyst. If it is too low, a sufficient conversion cannot be obtained.

The dehydrogenation reaction (contact reaction) of the present invention can be carried out in any system such as a fixed bed or a fluidized bed. The particle size and shape of the catalyst can be arbitrarily selected according to the type of reactor. The reaction pressure may be any of increased pressure, normal pressure and reduced pressure, but a range of 0.5 to 5 atm (absolute pressure) is particularly preferable. If the reaction pressure is less than 0.5 atm, the operating cost of the device for maintaining the reduced pressure will be large, and if it exceeds 5 atm, the theoretically calculated equilibrium yield will decrease and it will be difficult to obtain the desired yield. . As described above, when the activity of the catalyst of the present invention decreases after a certain period of use, the activity of the catalyst of the present invention can be recovered by recalcining in air.

[0019]

【Example】

Example 1 1.23 g of chromium nitrate was dissolved in deionized water, and 4.75 g of H--
ZSM-5 (silica / alumina ratio = 1900) was dispersed, sufficiently stirred, and dried under reduced pressure to obtain a precursor. This precursor was calcined in air at 750 ° C. for 5 hours. As a result, chromium oxide
A chromium / H-ZSM-5 catalyst containing 5% by weight of Cr ₂ O ₃ was prepared. 0.3 g of the obtained catalyst was filled in a quartz reaction tube having an inner diameter of 11 mm. After heating up to 650 ° C. under the flow of carbon dioxide, ethane was supplied in addition to carbon dioxide. The mixing ratio is 10% by volume of ethane and 90% by volume of carbon dioxide. The flow rate of the mixed gas was 100 ml / min. The outlet gas passing through the reaction tube was analyzed by an online gas chromatograph. The results are shown in Table 1. Further, the weight of carbon deposited on the catalyst surface after the reaction was measured. Thermogravimetric analyzer
(TA Instruments, TGA2950) was used to measure the weight loss due to carbon combustion by heating and raising the temperature under air flow. As a result, a 0.6% weight reduction was confirmed with respect to the catalyst weight, so the amount of carbon deposition was defined. In this example, no carbon was visually confirmed after the completion of the reaction for 6 hours. From the above, it can be seen that the amount of carbon deposited in this reaction is very small.

Example 2 In Example 1, sodium nitrate was used as a second component in addition to chromium nitrate, and the amount of sodium was 20 mol.
An amount of 1% was added, and a catalyst was prepared in the same manner as in Example 1 and the reaction product was analyzed. The results are shown in Table 1. This result shows that the addition of an alkali metal typified by sodium can improve the selectivity of ethylene without significantly lowering the yield.

Comparative Example 1 In Example 1, H-ZSM-5 (silica / alumina ratio = 1900)
Instead of HY, a catalyst was prepared in the same manner as in Example 1 using HY (silica / alumina ratio = 4.8), and the reaction product was analyzed. The results are shown in Table 1. From the comparison between this result and Examples 1 and 2, it is found that H-ZSM-5 is excellent as the zeolite of the carrier.

Comparative Example 2 Reference (Applied Catalysis A: General 196 (2000) 1-8)
The reaction results (values read from the tables and graphs described in the literature) using silica (silicon oxide) supporting chromium oxide reported in (1) as a catalyst are shown. The ethylene yield is high, but this is because the flow rate of the raw material gas is smaller than that in Example 1 (ethane / carbon dioxide / nitrogen = 6/24/30 ml / min) and the contact time between the raw material gas and the catalyst is long. Comparing the ethylene production rate per unit catalyst weight, it can be confirmed that Examples 1 and 2 are significantly excellent.

[0024]

[Table 1]

[0025]

INDUSTRIAL APPLICABILITY According to the present invention, when a lower alkane is dehydrogenated to produce a lower alkene, a stable catalytic activity retention rate is exhibited, and the decomposition carbonaceous material after the reaction is extremely small in ZSM-5. By using the zeolite-supported catalyst, the lower alkene can be industrially advantageously produced at an increased reaction rate.

Continued front page    (72) Inventor Kazuhisa Murata             1-1-1 Higashi 1-1-1 Tsukuba City, Ibaraki Prefecture             Inside the Tsukuba Center, National Institute of Advanced Industrial Science and Technology F-term (reference) 4H006 AA02 AC12 BA09 BA14 BA30                       BA55 BA60 BB61 DA12                 4H039 CA21 CC10

Claims (6)

[Claims] 1. A method for producing a lower alkene by dehydrogenating a lower alkane in the presence of a catalyst, wherein ZSM-5 zeolite is used as a catalyst carrier. 2. The catalyst is Va, VIa, VIII and I of the periodic table.
The method for producing a lower alkene according to claim 1, which comprises at least one metal oxide selected from the group IIa (excluding boron and aluminum). 3. At least one metal oxide selected from the groups Va, VIa, VIII and IIIa (excluding boron and aluminum) of the Periodic Table is chromium oxide, vanadium oxide or gallium oxide. The method for producing a lower alkene according to claim 1 or 2, wherein 4. The catalyst is Va, VIa, VIII and I of the periodic table.
The method for producing a lower alkene according to any one of claims 1 to 3, which comprises an alkali metal and at least one metal oxide selected from the group IIa (excluding boron and aluminum). 5. The method for producing a lower alkene according to claim 1, wherein dehydrogenation is performed in the presence of a carbon dioxide-containing gas. 6. The lower alkane is ethane and the lower alkene is ethylene.
Any of the methods for producing a lower alkene.