JP3094180B2 - Process for producing isobutylene by oxidative dehydrogenation of isobutane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing isobutylene by oxidatively dehydrogenating isobutane. For more information,
The present invention relates to a method for producing isobutylene by subjecting isobutane to gas phase catalytic oxidative dehydrogenation with molecular oxygen in the presence of a specific catalyst.

[0002]

2. Description of the Related Art Oxidative dehydrogenation is a method for producing an industrially useful unsaturated hydrocarbon from a corresponding saturated hydrocarbon. The following examples are known as attempts to produce unsaturated hydrocarbons by oxidatively dehydrogenating saturated hydrocarbons having 3 and 4 carbon atoms.

[0003] Chemtech. (197)
3) March pp. 186-189) report an example in which propane, n-butane, and isobutane were subjected to an oxidative dehydrogenation reaction in the presence of a catalyst in which potassium chloride, lithium chloride, and manganese chloride were supported on aluminum oxide. ing.

[0004] EP 189,282 relates to the oxidative dehydrogenation of ethane, propane and isobutane in the presence of a catalyst comprising an oxide of tin and phosphorus, but the examples in the specification refer to ethane to ethylene. Only a reaction example for producing is reported.

US Pat. No. 4,751,342 discloses an example of producing corresponding unsaturated hydrocarbons by oxidative dehydrogenation of propane and n-butane in the presence of a catalyst comprising oxides of nickel, tin and phosphorus. Have been reported.

German Patent No. 2,124,438 discloses that isobutane is oxidized and dehydrogenated in the presence of a metal oxide catalyst supported on alumina, hydrogen iodide, to give a conversion of isobutane of 28% and a selectivity of 85.
It is said that isobutylene was obtained in%. However, it has a disadvantage that hydrogen iodide must coexist.

In Japanese Patent Application Laid-Open No. 3-218327, oxidative dehydrogenation of propane and isobutane is carried out using a catalyst containing tin or an oxide of indium and phosphorus as a main component. However, if ammonia does not coexist in the feed gas, there is a disadvantage that the selectivity of propylene and isobutylene is low. A reaction using only isobutane and oxygen gave a conversion of 14% and an isobutylene selectivity of 32%.

[0008] As described above, there has been no report on a catalyst system capable of obtaining a high selectivity in the oxidative dehydrogenation of propane, n-butane, and isobutane. In particular, in the case of oxidative dehydrogenation of isobutane without using halogen or ammonium, no example has been reported in which the selectivity of isobutane exceeds 50%.

[0009]

An object of the present invention is to provide a method for obtaining isobutylene with high selectivity by oxidative dehydrogenation of isobutane in the presence of a catalyst having a specific composition.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on catalysts to solve the above-mentioned problems, and as a result, have found that a catalyst comprising an oxide of phosphorus and an oxide of a specific metal exhibits high selectivity. Heading, the present invention has been completed.

That is, the present invention relates to a method for producing isobutylene by oxidatively dehydrogenating isobutane with molecular oxygen in the gas phase, comprising the steps of: preparing an oxide of phosphorus and lithium, scandium, titanium, gallium, strontium, yttrium, zirconium, antimony. , Cesium, lantern,
A process for producing isobutylene, characterized by using a catalyst comprising an oxide of at least one element selected from the group consisting of cerium, samarium, europium, ytterbium, hafnium, lead and bismuth.

The catalyst used in the present invention comprises phosphoric acid or phosphate and a metal compound (metal chloride, metal nitrate, metal sulfate, organometallic compound, metal oxide, ammonium salt of metal oxide, metal oxide). Oxalate) can be prepared.

Further, the catalyst used in the present invention is composed of at least two or more components, and may be in the form of a compound as a so-called composite oxide, but at least one component is an oxide of another component. It may be in the form of being carried on. Although this is a method commonly used in the art, this catalyst may be used while being supported on a carrier such as silica, alumina, silicon carbide, or silicon nitride.

The raw material gases used in the production method of the present invention are mainly isobutane and oxygen, but can be diluted with an inert gas or the like. Examples of such a gas include nitrogen, helium, argon, carbon dioxide, water vapor, and light alkanes such as methane, ethane, propane, and butane.

The source of oxygen used in the production method of the present invention is not particularly limited, but usually, pure oxygen, oxygen-enriched air, air or the like is used. There is no limitation on the molar ratio of isobutane to oxygen in the reaction raw material gas. However, if the molar ratio of oxygen is too small, the reaction is rate-controlled by the supply of oxygen, and the reaction rate is low, resulting in poor productivity per unit catalyst. Conversely, as the oxygen molar ratio increases, the amount of by-products other than isobutylene increases and the selectivity decreases. Further, there is a case where the fuel enters the combustion range and poses a safety problem. Therefore, it is preferable that the molar ratio of isobutane to oxygen in the reaction raw material gas be 1: 0.05 to 1.

Although the isobutane concentration in the reaction raw material gas used in the production method of the present invention is not limited, if the isobutane concentration is too low, the reaction rate is slow, and the productivity per unit catalyst is deteriorated. The isobutane concentration in the reaction raw material gas is 10
It is preferably 95 vol%.

The reaction temperature varies depending on the isobutane concentration, the molar ratio in the raw material gas, and the contact time.
700 ° C, preferably in the range of 250 ° C to 600 ° C. The reaction pressure is generally between 1 and 50 bar, preferably between 1 and 50 bar.
In the range of 3 bar.

The present invention can be practiced in any of fixed beds, moving beds, fluidized beds and the like. When the reaction is carried out in a fluidized bed, the reaction is carried out by oxidatively dehydrogenating isobutane using only oxygen in the catalyst using a raw material gas that does not contain oxygen, and then reoxidizing the catalyst with an oxygen-containing gas in a separate reactor. It can also take the form.

The product of this reaction is mainly isobutylene, but also produces some propylene and methane. There is little complete oxidation to carbon oxide, and some oxygen-containing compounds such as methacrolein are also formed.

[0020]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 8.65 g of cerium nitrate hexahydrate (manufactured by Wako Pure Chemical Industries) was added to and dissolved in 300 ml of ion-exchanged water, and 2.65 g of pyrophosphoric acid (manufactured by Wako Pure Chemical Industries) was ion-exchanged. Water 50
The solution dissolved in ml was stirred and mixed. 25
% Ammonia water was added until a pH of 7 formed a precipitate. After filtering this precipitate, 500 m of ion-exchanged water was used.
and dried at 120 ° C. and further in a nitrogen stream.
A catalyst fired at 500 ° C. for 4 hours and formed into a 10 to 24 mesh was used as a catalyst.

A catalyst prepared by diluting 3.0 g of this catalyst with 23.0 g of silicon carbide was filled into a glass reaction tube having an inner diameter of 15 mm, and the temperature was kept at 500 ° C., and the molar ratio of isobutane / oxygen / nitrogen was 75/5/20. 60ml / min
Supplied with When the reaction product gas was analyzed, the conversion of isobutane was 6.4%, the conversion of oxygen was 100%, the selectivity of isobutylene was 75.9%, the selectivity of propylene was 8.3%, and the selectivity of methacrolein was selected. The rate was 0.5%.

Example 2 The same operation as in Example 1 was carried out except that the reaction temperature was changed from 500 ° C. to 450 ° C., the conversion of isobutane was 4.5%, the conversion of oxygen was 100%, and the selection of isobutylene was carried out. The selectivity was 75.4%, the selectivity for propylene was 5.7%, and the selectivity for methacrolein was 1.1%.

Examples 3 to 7 In the catalyst preparation method shown in Example 1, a cerium nitrate hexahydrate was replaced by a nitrate or a hydrate of a nitrate of an element shown in Table 1, and the atomic ratio of metal: phosphorus was changed to metal. If is bivalent 1:
A catalyst was prepared in the same manner as in Example 1 by using an amount such that the ratio becomes 1: 3 in the case of monovalent or trivalent, and the same operation as in Example 1 was performed. Obtained.

[0025]

[Table 1]

Example 8 21.3 g of lanthanum acetate 1.5 hydrate (manufactured by Hanui Tesque)
Was added to and dissolved in 150 ml of ion-exchanged water heated to 50 ° C. 8.5 g of pyrophosphoric acid dissolved in 50 ml of ion-exchanged water was added thereto to form a white precipitate, which was then evaporated to dryness by a rotary evaporator and calcined at 500 ° C. for 4 hours in a nitrogen stream to obtain a precipitate. What was formed into ２４24 mesh was used as a catalyst. Example 1 using this catalyst
When the same operation as described above was performed, the conversion of isobutane was 4.
The conversion of oxygen was 93%, the selectivity of isobutylene was 59.2%, the selectivity of propylene was 19.0%, and the selectivity of methacrolein was 2.3%.

Examples 9 to 12 In the catalyst preparation method shown in Example 8, lanthanum acetate was used.
Instead of pentahydrate, acetate or hydrate of acetate of an element shown in Table 2 is used. When the metal: phosphorus atomic ratio is 2: 1 when the metal is monovalent, it is 1: 1 when the metal is phosphorus. A catalyst was prepared in the same manner as in Example 8 using an amount of 3: 3 in the case of trivalent, and the same operation as in Example 1 was carried out.
Was obtained.

[0028]

[Table 2]

Example 14 38.0 g of titanium tetrachloride was added to 300 ml of ion-exchanged water.
(Manufactured by Wako Pure Chemical Industries) was gradually added and dissolved. 38.3 g of pyrophosphoric acid (manufactured by Wako Pure Chemical Industries) dissolved in 100 ml of ion-exchanged water was added to the solution to precipitate a precipitate. After neutralization with 25% aqueous ammonia, the precipitate was filtered, washed with 1000 ml of ion-exchanged water, dried at 120 ° C., and calcined at 500 ° C. for 4 hours in a nitrogen stream to obtain a precipitate.
What was molded into 0 to 24 mesh was used as a catalyst. When the same operation as in Example 1 was performed using this catalyst, the conversion of isobutane was 2.9%, the conversion of oxygen was 100%, the selectivity of isobutylene was 59.2%, and the selectivity of propylene was 6. 8% and methacrolein selectivity was 0.1%.

Examples 15 to 17 In the catalyst preparation method shown in Example 14, instead of titanium tetrachloride, chlorides or hydrates of the elements shown in Table 3 were used. 2: 3 for trivalent,
Example 1
A catalyst was prepared in the same manner as in Example 4, and the same operation as in Example 1 was performed. The results in Table 3 were obtained.

[0031]

[Table 3]

Example 18 Zirconium oxychloride octahydrate (manufactured by Wako Pure Chemical Industries) 1
Sodium diphosphate decahydrate (manufactured by Wako Pure Chemical Industries) was added to a solution prepared by dissolving 77.2 g in 1 liter of ion-exchanged water.
When a solution prepared by dissolving 113.8 g in 450 ml of ion-exchanged water at 50 ° C. was added, a white precipitate was formed. After the precipitate was filtered, the precipitate was washed with 2 liters of ion-exchanged water.
The catalyst was dried at 0 ° C., baked at 500 ° C. for 4 hours in a nitrogen stream, and shaped into a 10 to 24 mesh. When the same operation as in Example 1 was performed using this catalyst, the conversion of isobutane was 3.5%, and the conversion of oxygen was 9%.
The selectivity for isobutylene was 54.8%, the selectivity for propylene was 3.9%, and the selectivity for methacrolein was 0%.

Example 19 Lithium phosphate pentahydrate (manufactured by Katayama Chemical Co., Ltd.) was calcined in air at 500 ° C. for 4 hours, and then tableted to form a tablet.
What was formed into a mesh was used as a catalyst. When the same operation as in Example 1 was performed using this catalyst, the conversion of isobutane was 2.4%, the conversion of oxygen was 83%, the selectivity of isobutylene was 57.2%, and the selectivity of propylene was 7. 1%,
The selectivity for methacrolein was 2.7%.

Continued on the front page (72) Inventor Kensen Okusako 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Industries, Ltd. (72) Inventor Naoki Miura 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical (72) Inventor Koichi Nagai 5-1 Sokai-cho, Niihama-shi, Ehime Prefecture Sumitomo Chemical Industries, Ltd. (56) References JP-A-3-218327 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C07C 5/48 B01J 27/16 B01J 27/18 C07C 11/09 C07B 61/00 300 CA (STN) REGISTRY (STN)

Claims (4)

(57) [Claims] A method for producing isobutylene by oxidatively dehydrogenating isobutane with molecular oxygen in the gas phase,
Oxides of phosphorus and lithium, scandium, titanium, gallium, strontium, yttrium, zirconium,
A method for producing isobutylene, comprising using a catalyst comprising an oxide of at least one element selected from the group consisting of antimony, cesium, lanthanum, cerium, samarium, europium, ytterbium, hafnium, lead and bismuth. 2. The reaction temperature of oxidative dehydrogenation is 200 to 600.
The method for producing isobutylene according to claim 1, wherein the temperature is ° C. 3. The method according to claim 1, wherein the molar ratio of isobutane to oxygen in the mixed gas is 1: 0.05 to 1. 4. An isobutane concentration in the mixed gas of 10 to 10.
The method for producing isobutylene according to claim 1, wherein the content is 95 vol%.