JP7137920B2 - Method for producing butadiene - Google Patents

Description

The present invention relates to a method for producing butadiene.

As a method for industrially producing butadiene, BBP obtained by naphtha cracking (a mixture of mainly hydrocarbons having 3 to 5 carbon atoms) is extracted with a solvent, and butane, butene, acetylenes, high-boiling components and low-boiling components are extracted. A method of selectively removing components and the like is employed.

On the other hand, a mixture containing n-butene is gasified in a vaporizer, nitrogen gas, air, and water are introduced, and the mixed gas is heated to about 150 to 250° C. in a preheater, and then oxidized. Patent Literatures 1 and 2 disclose a method of supplying a dehydrogenation reactor to produce butadiene. US Pat. No. 5,300,004 discloses a method of vaporizing a butene-rich material, superheating it to a temperature of at least 205° C., mixing it with superheated steam and an oxygen-rich gas, and oxidatively dehydrogenating it over a ferrite catalyst to give butadiene. ing. In Patent Document 4, a monoolefin having 4 or more carbon atoms is gasified using a gasifier at room temperature of about 5°C to 35°C, or a monoolefin that is liquid at room temperature of about 5°C to 35°C. A method for producing butadiene by an oxidative dehydrogenation reaction is disclosed.

JP 2010-90082 A JP 2010-90083 A Japanese Patent Publication No. 2015-514092 Japanese Patent No. 5571273

In the methods of Patent Documents 1 to 3, when the raw material gas containing n-butene is heated and supplied (fed) to the reactor, the n-butene supply temperature is too high, and n-butene is contained in the reactor. The temperature of the raw material gas supply unit rises, the combustion reaction proceeds due to excessive reaction, the amount of carbon monoxide and/or carbon dioxide increases, and the yield of butadiene may decrease.

On the other hand, when the method of Patent Document 4 is used, the n-butene supply temperature (feed temperature) is too low, and the n-butene that has once evaporated in the vaporizer condenses in the feed pipe to generate mist. There is fear. If mist is generated, the flow meter installed in the feed pipe may give an erroneous indication, or the mist may rapidly evaporate in the reactor, resulting in a large amount of n-butene supplied to the reactor. fluctuating and causing patchiness in the gas composition within the reactor. For example, at locations where n-butene is excessive, the amount of unreacted n-butene increases and n-butene conversion and butadiene yield decrease. Also, at locations where the amount of n-butene is insufficient, combustion reaction proceeds due to overreaction, the amount of carbon dioxide increases, and the yield of butadiene decreases. Furthermore, when the composition in the reactor becomes uneven, carbon growth tends to be promoted on the catalyst surface, making long-term operation difficult.

The present invention has been made in view of the above problems, and effectively suppresses overreaction due to overheating of n-butene-containing gas or excessive fluctuation in the amount of n-butene supplied due to condensation of n-butene. An object of the present invention is to provide a method capable of stably producing butadiene over a long period of time.

The present inventors have found that in a method for producing butadiene by an oxidative dehydrogenation reaction by supplying an n-butene-containing gas and an oxygen-containing gas to a reactor and contacting them with a catalyst, the n-butene-containing gas supplied to the reactor Controlling the temperature, pressure, and linear velocity of n-butene within a predetermined range effectively prevents overreaction due to overheating of the n-butene-containing gas or excessive fluctuations in the amount of n-butene supplied due to condensation of n-butene. We have found that it can be suppressed, and have completed the present invention.

That is, the present invention is a method for producing butadiene as shown below.
(1)
A method for producing butadiene through an oxidative dehydrogenation reaction by supplying an n-butene-containing gas and an oxygen-containing gas to a reactor and bringing them into contact with a catalyst, comprising:
The temperature of the n-butene-containing gas supplied to the reactor is 5° C. or higher and 150° C. or lower, and
the pressure of the n-butene-containing gas supplied to the reactor is less than the vapor pressure of n-butene at the temperature of the n-butene-containing gas supplied to the reactor; and
A method for producing butadiene, wherein the linear velocity of the n-butene-containing gas supplied to the reactor is 50 cm/sec or more.
(2)
The method for producing butadiene according to (1), wherein the n-butene-containing gas is heated and/or kept warm in a pipe for supplying the n-butene-containing gas to the reactor.
(3)
The method for producing butadiene according to (2), wherein reaction heat is used as a heat source for heating and/or retaining the n-butene-containing gas in the piping.
(4)
comprising a vaporization step of vaporizing the n-butene-containing gas using a vaporizer;
In the vaporization step,
The temperature of the n-butene-containing gas that has passed through the vaporizer is 15° C. or higher and 150° C. or lower, and
The pressure of the n-butene-containing gas that has passed through the vaporizer is less than the vapor pressure at the temperature of the n-butene that has passed through the vaporizer, and
The method for producing butadiene according to any one of (1) to (3), wherein the linear velocity of the n-butene-containing gas that has passed through the vaporizer is 50 cm/sec or more.
(5)
The method for producing butadiene according to (4), wherein the n-butene-containing gas is heated and/or kept warm in the outlet pipe of the vaporizer.
(6)
The method for producing butadiene according to (5), wherein reaction heat is used as a heat source for heating and/or retaining the n-butene-containing gas at the outlet pipe of the vaporizer.
(7)
The method for producing butadiene according to any one of (1) to (6), wherein the reactor is a fluidized bed reactor.

According to the present invention, butadiene can be stably produced over a long period of time by effectively suppressing overreaction due to overheating of the n-butene-containing gas or excessive fluctuations in the supply amount of n-butene due to condensation of n-butene. It is possible to provide a possible method.

EMBODIMENT OF THE INVENTION Hereinafter, the form (henceforth "this embodiment") for implementing this invention is demonstrated in detail. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[Method for producing butadiene]
The method for producing butadiene of the present embodiment is a method for producing butadiene by supplying an n-butene-containing gas and an oxygen-containing gas to a reactor, bringing them into contact with a catalyst, and subjecting them to an oxidative dehydrogenation reaction. The temperature of the n-butene-containing gas is 5 ° C. or higher and 150 ° C. or lower, and the pressure of the n-butene-containing gas supplied to the reactor is the vapor pressure of n-butene at the temperature of the n-butene-containing gas (hereinafter also simply referred to as “vapor pressure”), and the linear velocity of the n-butene-containing gas supplied to the reactor is 50 cm/sec or more. The production method of the present embodiment is provided with a configuration for controlling the temperature, pressure, and linear velocity of the n-butene-containing gas supplied to the reactor within the above ranges, so that the n-butene-containing gas is overheated and overreacted. , or excessive fluctuations in the amount of n-butene supplied due to condensation of n-butene can be effectively suppressed. As a result, for example, using a vaporizer, the process of vaporizing the n-butene-containing gas (vaporization process) can be easily managed, and n-butene can be stably supplied to the reactor over a long period of time. As a result, for example, it is possible to suppress the occurrence of unevenness in the gas composition within the reactor, thereby suppressing the deterioration of the reaction state and the decrease in the yield of butadiene. If the deterioration of the reaction state is suppressed, fluctuations in the gas composition and amount of produced gas at the reactor outlet will also be reduced, and it is expected that the subsequent process of purifying the produced gas to increase the purity of butadiene (refining process) can be performed stably. be As a result, it is expected that fluctuations in the composition of butadiene discharged as a product can be effectively suppressed. In addition, the production method of the present embodiment has the above configuration, so that overheating of the n-butene-containing gas and overreaction in the reactor due to excessive supply can be effectively suppressed, and excessive fluctuations in the reaction temperature can be suppressed. can be effectively suppressed. Thereby, the oxidative dehydrogenation reaction can be performed under suitable reaction conditions. Therefore, it is expected that the sequential reaction of butadiene can be easily controlled, and the yield of butadiene is stabilized over a long period of time. Furthermore, by stabilizing the reaction temperature and the amount of n-butene supplied, for example, thermal damage to the catalyst due to hot spots (partial high temperature parts) and reduction deterioration of the catalyst due to reducing atmosphere can be effectively suppressed. can. Therefore, it is expected that the life of the catalyst will be extended.

Furthermore, in the butadiene production apparatus used in the production method of the present embodiment, for example, a piping for supplying (feeding) the n-butene-containing gas to the reactor may be provided with heating means and/or heat insulating means. and/or the temperature of the n-butene-containing gas supplied to the reactor is adjusted to 5° C. or higher and 150° C. or lower by the heat insulating means, and the pressure of the n-butene-containing gas supplied to the reactor is adjusted to the reactor. It is a production apparatus that can be adjusted below the vapor pressure at the temperature of the n-butene-containing gas. Note that the manufacturing apparatus does not necessarily need to be provided with a heating means and/or a heat retaining means.

The temperature of the n-butene-containing gas supplied to the reactor is 5°C or higher and 150°C or lower, preferably 20°C or higher and 120°C or lower, more preferably 50°C or higher and 90°C or lower. When the temperature is within the above range, the vapor pressure of the n-butene-containing gas is increased while controlling overreaction due to overheating of the n-butene-containing gas, thereby making it difficult for the n-butene-containing gas to condense. be able to. The "temperature of the n-butene-containing gas supplied to the reactor" refers to the temperature of the n-butene-containing gas in the pipe that supplies the n-butene-containing gas to the reactor.

The pressure of the n-butene-containing gas supplied to the reactor is less than the vapor pressure of n-butene at the temperature of the n-butene-containing gas supplied to the reactor (for example, the reaction pressure or more and less than the vapor pressure), and steam It is preferably 0.1 MPa lower than the pressure, and more preferably 0.3 MPa lower than the vapor pressure. By keeping the pressure within the above range, it is possible to suppress condensation due to a local temperature drop within the piping. "The pressure of the n-butene-containing gas supplied to the reactor" refers to the pressure of the n-butene-containing gas in the piping that supplies the n-butene-containing gas to the reactor. Vapor pressure can be estimated based on Antoine's equation.

The linear velocity of the n-butene-containing gas supplied to the reactor is 50 cm/sec or more, preferably 75 cm/sec or more, more preferably 100 cm/sec or more. When the linear velocity is within the above range, it is possible to suppress condensation due to temperature drop in the piping. "Linear velocity of the n-butene-containing gas supplied to the reactor" refers to the linear velocity of the n-butene-containing gas in the piping that supplies the n-butene-containing gas to the reactor.

In the production method of the present embodiment, in order to adjust the temperature and pressure of the n-butene-containing gas supplied to the reactor within the above ranges, n- It is preferred to heat and/or keep the butene-containing gas warm. In this case, as a heat source for heating the n-butene-containing gas in the pipe, for example, steam or hot water trace is used, or as a heat source for keeping the n-butene-containing gas in the pipe warm, for example, a known It is conceivable to use a heat insulating material, but from the viewpoint of energy efficiency, it is preferable to use reaction heat as a heat source for heating and heat retention.

In the production method of the present embodiment, as raw materials, a gas containing n-butene (1-butene, 2-butene, isobutene) (n-butene-containing gas) and an oxygen-containing gas (eg, air and oxygen) are used. used, and nitrogen may also be used. These gases do not necessarily have to be of high purity, may contain any mixtures, and may be of industrial grade. Examples of the n-butene-containing gas include n-butene obtained by the dimerization reaction of ethylene, a residual component (raffinate-1) obtained by extracting 1,3-butadiene from the _C4 fraction produced as a by-product of naphtha pyrolysis, and isobutylene. Extracted residual component (raffinate-2), butene fraction obtained by dehydrogenation or oxidative dehydrogenation of n-butane, and ethane pyrolysis, secondary by catalytic conversion reaction of ethylene obtained by dehydration reaction of biomass ethanol The resulting _C4 cut can be used. Biomass ethanol is ethanol obtained from plant resources, and specific examples include ethanol obtained by fermentation of sugarcane, corn, etc., and ethanol obtained from woody resources such as waste wood, thinned wood, rice straw, and agricultural crops.

The n-butene-containing gas may or may not contain paraffin, water (water vapor), hydrogen, nitrogen, carbon dioxide, and carbon monoxide in addition to n-butene. Paraffins include methane, ethane, propane, butane, pentane, hexane, heptane, octane, and nonane. Further, after separating the target product butadiene from the reaction product, at least part of the unreacted n-butene may be recycled to the reactor.

The concentration of n-butene supplied to the reactor is preferably 2% by volume or more with respect to the total amount of gas supplied (100% by volume) from the viewpoint of further improving the productivity of butadiene. From the viewpoint of further suppressing the load of , it is preferably 30% by volume or less. From the same point of view, the concentration of n-butene is more preferably 3% by volume or more and 25% by volume or less, and further preferably 4% by volume or more and 20% by volume or less.

In the production method of the present embodiment, in order to more effectively suppress overreaction due to overheating of the n-butene-containing gas or excessive fluctuations in the amount of n-butene supplied due to condensation of n-butene, the vaporizer preferably includes a vaporization step of vaporizing the n-butene-containing gas using . Vaporizers include known vaporizers commonly used to vaporize n-butene-containing gases.

In the vaporization step, the temperature of the n-butene-containing gas that has passed through the vaporizer is preferably 15° C. or higher and 150° C. or lower, more preferably 20° C. or higher and 120° C. or lower, and 50° C. or higher and 90° C. or lower. It is even more preferable to have When the temperature is within the above range, the vapor pressure of the n-butene-containing gas is increased while controlling overreaction due to overheating of the n-butene-containing gas, thereby making it difficult for n-butene to condense. can. "The temperature of the n-butene-containing gas that has passed through the vaporizer" refers to the temperature of the n-butene-containing gas in the outlet pipe of the vaporizer.

In the vaporization step, the pressure of the n-butene-containing gas that has passed through the vaporizer is less than the vapor pressure of n-butene at the temperature of the n-butene-containing gas that has passed through the vaporizer (for example, the reaction pressure or more and the vapor pressure is less than). , preferably 0.1 MPa lower than the vapor pressure, more preferably 0.3 MPa lower than the vapor pressure. By keeping the pressure within the above range, it is possible to suppress condensation due to a local temperature drop within the piping. Incidentally, "the pressure of the n-butene-containing gas that has passed through the vaporizer" refers to the pressure of the n-butene-containing gas in the outlet pipe of the vaporizer.

In the vaporization step, the linear velocity of the n-butene-containing gas that has passed through the vaporizer is 50 cm/sec or more, preferably 75 cm/sec or more, and more preferably 100 cm/sec or more. When the linear velocity is within the above range, it is possible to suppress condensation due to temperature drop in the piping. It refers to the linear velocity of the n-butene-containing gas in the outlet pipe of the vaporizer.

In the vaporization step, in order to adjust the temperature and pressure of the n-butene-containing gas that has passed through the vaporizer within the above ranges, the n-butene-containing gas may be heated and/or kept warm at the outlet pipe of the vaporizer. preferable. In this case, as a heat source for heating the n-butene-containing gas in the pipe, for example, steam or hot water trace is used, or as a heat source for keeping the n-butene-containing gas in the pipe warm, for example, a known It is conceivable to use a heat insulating material, but from the viewpoint of energy efficiency, it is preferable to use reaction heat as a heat source for heating and heat retention.

In the production method of the present embodiment, the reaction system used for the oxidative dehydrogenation reaction includes a fixed bed reaction system and a fluidized bed reaction system, preferably a fluidized bed reaction system, and the reactor is a fluidized bed reactor. Preferably. The fixed bed reaction system has the advantage that the gas flow is close to that of an extrusion flow, and the reaction yield can be increased, and is widely used industrially. However, the production method using a fixed bed reactor has lower heat transfer than the production method using a fluidized bed reactor, and is not sufficient for exothermic reactions and endothermic reactions that require heat removal and heating. The fluidized bed reaction system is characterized by vigorous fluidization of catalyst particles within the reactor. Due to these characteristics, the heat transfer is high, and there is an advantage that the temperature inside the reactor can be kept almost uniform even during a reaction accompanied by a large amount of heat generation or endotherm, and excessive progress of the reaction can be suppressed. In addition, since the local accumulation of energy is suppressed, it is possible to react the material gas within the explosion range, and there is also the advantage that the concentration of the material can be increased and the productivity can be improved. Therefore, the fluidized bed reaction system is more suitable for the oxidative dehydrogenation reaction of hydrocarbons accompanied by intense heat generation, such as the production of butadiene from butene.

Generally, in the fluidized bed reaction system, if the amount of n-butene supplied to the reactor is disturbed, the flow state of n-butene and the catalyst deteriorates, and the yield may decrease. In addition, when spots of n-butene occur in the reactor, there is a risk of temperature rise (also referred to as hot spots) due to partial overreaction and generation of a reducing atmosphere. In partial overreaction, the produced butadiene is consumed by successive reactions, causing a decrease in yield. Further, when the catalyst is exposed to a reducing atmosphere, there is a risk that the catalyst will be deteriorated by reduction, resulting in a decrease in catalytic activity. On the other hand, in the production method of the embodiment of the present application, for example, the temperature, pressure, and linear velocity of the n-butene-containing gas supplied to the reactor are controlled within the above ranges, so that the n-butene-containing An effect of suppressing a decrease in yield of butadiene due to overheating of gas is obtained. In addition, due to the above configuration, for example, the deterioration of the flow state in the reactor due to the condensation of n-butene, the generation of hot spots due to the generation of n-butene spots in the reactor, and the generation of a reducing atmosphere can be suppressed, and as a result, it is possible to avoid a decrease in butadiene yield and deterioration of the catalyst. These effects are achieved by controlling the temperature, pressure, and linear velocity of the n-butene-containing gas in the outlet pipe of the vaporizer within the above ranges in the vaporization process, Heating and/or keeping the n-butene-containing gas in the outlet pipe of the vaporizer and the n-butene in the vaporizer more reliable.

In the production method of the present embodiment, the reaction temperature is preferably 300° C. or higher and 450° C. or lower, more preferably 320° C. or higher and 420° C. or lower, and even more preferably 340° C. or higher and 400° C. or lower. A reaction temperature of 300° C. or higher tends to further improve the conversion of n-butene. On the other hand, when the reaction temperature is 450° C. or lower, it tends to be possible to more effectively prevent combustion decomposition of the produced butadiene. Since the production reaction of butadiene is an exothermic reaction, it is preferable to remove the heat so as to obtain a suitable reaction temperature. The heat of reaction generated can be removed, for example, using a cooling pipe inserted in the reactor. The reaction temperature can be adjusted within the above range by removing reaction heat through a cooling pipe or supplying heat through a heating device.

In the production method of the present embodiment, the reaction pressure may be in the range of slightly reduced pressure to 0.8 MPa. The contact time between the n-butene-containing gas, the oxygen-containing gas, and the catalyst supplied to the reactor cannot be determined unambiguously, but with respect to the total amount of gas supplied and the amount of catalyst in the reactor, 1 to 20 (sec) ·g/cc), preferably in the range of 2 to 10 (sec·g/cc), butadiene tends to be more suitably produced.

In this embodiment, the produced butadiene-containing gas flows out from the reactor outlet. The oxygen concentration in the gas at the reactor outlet is preferably 0% by volume or more and 3.0% by volume or less, more preferably 0.1% by volume or more and 2.5% by volume or less, and still more preferably 0.2% by volume. It is vol% or more and 2.0 vol% or less. The oxygen concentration in the gas at the reactor outlet is determined by the amount of oxygen supply source gas supplied to the reactor, for example, the amount of air supplied to the reactor, the reaction temperature, the pressure in the reactor, the amount of catalyst, and the reaction It can be adjusted by changing the total amount of feed gas supplied to the vessel. By setting the oxygen concentration in the gas at the outlet of the reactor to 3.0% by volume or less, combustion decomposition of the produced butadiene can be more effectively suppressed, and butadiene can be obtained in a much better yield. tend to be able.

In the production method of this embodiment, the gas discharged from the reactor outlet can be purified by a known technique. For example, see methods described in JP-B-45-17407, JP-B-60126235, JP-B-3-48891, PETROTECH, Vol. 2, No. 4 (pp. 59-65, 1978), etc. can do.

The catalyst used in the production method of the present embodiment includes, for example, an oxide catalyst containing molybdenum and producing butadiene by contact with n-butene. Among these, an oxide containing molybdenum is used. Catalysts supported on supports are preferred.

The catalyst in which the oxide is supported on the carrier in the present embodiment preferably contains the carrier and Mo, Bi and Fe. The composition of Mo, Bi and Fe is preferably adjusted to form a purposeful oxide, in which lattice oxygen allows the oxidative dehydrogenation of n-butene to butadiene. Although it is speculated that this speculation does not limit the invention in any way. In general, oxygen vacancies are generated in the oxide when lattice oxygen in the catalyst is consumed in the oxidative dehydrogenation reaction. As a result, as the reaction progresses, the reduction of the oxide proceeds, and the catalytic activity is deactivated. Therefore, in order to maintain good catalytic activity, it is preferable that the oxide that has undergone reduction be quickly reoxidized. The above oxides containing Mo, Bi, and Fe have reactivity with respect to the oxidative dehydrogenation reaction of n-butene to butadiene, and in addition, molecular oxygen in the gas phase is dissociated and adsorbed into the oxide and consumed. Although it is presumed that it is also excellent in the reoxidation action of regenerating lattice oxygen, the present invention is not limited by this presumption.

In the production method of the present embodiment, the catalyst in which the oxide containing Mo, Bi and Fe is supported on the carrier is effective for the secondary decomposition of the product butadiene, especially when used for the production of butadiene by the fluidized bed method. It tends to be possible to suppress and obtain butadiene in high yield. Although the details are unknown, it is speculated that secondary decomposition of butadiene on the catalyst is suppressed because the acidity of the catalyst is suitable. Since the adsorption capacity of the active sites is small, it is presumed that the produced butadiene quickly desorbs from the catalyst before being decomposed at the reaction active sites, but the present invention is not limited by these presumptions.

In the present embodiment, the composition ratio of Mo, Bi, and Fe is such that the atomic ratio p of Bi and the atomic ratio q of Fe with respect to the atomic ratio of Mo of 12 are 0.2 from the viewpoint of facilitating the formation of purposeful oxides. It is preferably in the range of 1≤p≤5 and 0.5≤q≤8.

The oxide contained in the oxide catalyst has the following empirical formula:
_{Mo12BipFeqAaBbCcDdEeOx _ _ _ _ _ _ _ _}
(In the above empirical formula, A represents at least one element selected from the group consisting of nickel and cobalt, B represents at least one alkali metal element, C represents magnesium, calcium, strontium, barium, Represents at least one element selected from the group consisting of zinc and manganese, D represents at least one rare earth element, E represents at least one element selected from the group consisting of chromium, indium and gallium, O represents oxygen, p, q, a, b, c, d, e, and x represent the atomic ratios of bismuth, iron, A, B, C, D, E and oxygen to molybdenum-12 atoms, respectively; 0.1 ≤ p ≤ 5, 0.5 ≤ q ≤ 8, 0 ≤ a ≤ 10, 0.02 ≤ b ≤ 2, 0 ≤ c ≤ 5, 0 ≤ d ≤ 5, 0 ≤ e ≤ 5; x is the number of oxygen atoms required to satisfy the valence requirements of the other elements present.

As used herein, the term "empirical formula" refers to a composition consisting of the atomic ratios of metals contained in the formula and oxygen required according to the sum of the atomic ratios and oxidation numbers. Since it is practically impossible to specify the number of oxygen atoms in oxides containing metals that can have various oxidation numbers, the number of oxygen atoms is formally represented by "x". For example, when preparing a slurry containing a Mo compound, a Bi compound and an Fe compound and drying and/or firing it to obtain an oxide, the atomic ratio of the metal contained in the slurry and the metal in the resulting oxide It may be considered that the atomic ratio is substantially the same. Therefore, the empirical formula of the resulting oxide is obtained by adding Ox to the charged composition formula of the slurry. In this specification, a formula representing intentionally controlled components and their ratios, such as the composition of the charged slurry described above, is referred to as a "composition formula". In the case of the above example, the empirical formula excluding Ox is referred to as the "composition formula".

In the above empirical formula, the roles of the optional components represented by A, B, C, D and E are not limited, but in the field of oxide catalysts containing Mo, Bi and Fe as essential components, the following are generally used: It is guessed. That is, it is speculated that A and E improve the activity of the catalyst, B and C stabilize the structure of suitable oxides containing Mo, Bi and Fe, and D reoxidizes the oxides. be. When p, q, a, b, c, d and e in the above empirical formula are within the preferred ranges, these effects tend to be enhanced. It should be noted that the present invention is not limited in any way by these assumptions.

In the above empirical formula, more preferable compositions are 0.2≤p≤3.0, 0.7≤q≤5.0, 1.0≤a≤9.0, 0.05≤b≤1.0. , 1.0 ≤ c ≤ 4.0, 0.1 ≤ d ≤ 3.0, 0 ≤ e ≤ 4.0. is cerium, lanthanum, praseodymium, neodymium, or yttrium, and 0.3 ≤ p ≤ 2.0, 1.0 ≤ q ≤ 3.0, 2.0 ≤ a ≤ 8.0, 0.1 ≤ b ≤0.5, 1.5≤c≤3.5, 0.2≤d≤2.0, 0≤e≤3.0. When the oxide has the above composition, the yield of butadiene tends to be high.

In this embodiment, the oxide is preferably supported on a carrier. Supporting an oxide on a carrier tends to impart suitable physical properties such as particle shape/size/distribution and mechanical strength. In the fluidized bed system, the fluidity can be improved by supporting the oxide on the carrier. The carrier can be effectively used in an amount of preferably 30 to 70% by mass, more preferably 40 to 60% by mass, based on the total of the carrier and oxide. Supported catalysts containing oxides containing Mo, Bi and Fe can be produced by known methods. For example, a manufacturing method including a first step of preparing a raw material slurry, a second step of drying the raw material slurry, and a third step of firing the dried product obtained in the second step. can be adopted. The carrier is not particularly limited, but preferably one or more selected from the group consisting of silica, alumina, titania and zirconia, with silica being particularly preferred. Silica is an inactive carrier compared to other carriers, and by using silica as a carrier, there is a tendency to be able to exhibit a good binding action with the catalyst without reducing the activity and selectivity of the catalyst for butadiene. be.

A method for producing the catalyst will be described. Note that this method is one of typical catalyst production methods, and the present invention is not limited by the method described below.

In the first step, catalyst raw materials are mixed to prepare a raw material slurry. Molybdenum, bismuth, iron, nickel, cobalt, alkali metal elements, magnesium, calcium, strontium, barium, zinc, manganese, rare earth elements, chromium, indium, and gallium can be supplied from soluble in water or nitric acid. Ammonium salts, nitrates, hydrochlorides, sulfates, organic acid salts and the like can be mentioned. As described above, oxides such as silica, alumina, titania, and zirconia can be used as the oxide carrier. Silica is used as a suitable carrier, and silica sol is preferred as the silica source in that case. The raw material slurry is prepared, for example, by adding an ammonium salt of molybdenum dissolved in water to silica sol, and then adding nitrates of bismuth, rare earth elements, iron, nickel, magnesium, zinc, manganese, and alkali elements to water. Alternatively, it can be carried out by adding a solution dissolved in an aqueous nitric acid solution. In that case, the order of addition described above can be changed.

In the second step, the raw material slurry obtained in the first step is dried to obtain a dried product. Drying methods include ordinary spray dryers, slurry dryers, drum dryers, ordinary box-type dryers, tunnel-type kilns, and the like.

In the third step, the desired catalyst is obtained by calcining the dried product obtained in the second step. The firing process can be performed using a firing furnace such as a rotary furnace, a tunnel furnace, or a muffle furnace.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited by the examples described below.

In Examples and Comparative Examples, n-butene conversion, butadiene selectivity and yield used to express reaction results are defined by the following equations.
n-butene conversion rate (%)
= (number of moles of reacted n-butene) / (number of moles of supplied n-butene) x 100
Butadiene selectivity (%)
= (number of moles of butadiene produced)/(number of moles of reacted n-butene) x 100
Butadiene yield (%)
= (Number of moles of butadiene produced)/(Number of moles of n-butene supplied) x 100

Contact time is defined by the following equation.
Contact time (sec.g/cc)
=W/F×273.15/(273.15+T)×(P×1000+101.325)/101.325
(Wherein, W represents the catalyst filling amount (g), F represents the total supply gas flow rate (cc/sec, converted to NTP), T represents the reaction temperature (°C), and P represents the reaction pressure ( MPa).)

Analysis of the gas at the reactor outlet was performed by gas chromatography (GC-2010 (Shimadzu Corporation product) directly connected to the reactor, analysis column: HP-AL/S (Agilent J & W product), carrier gas: helium, column temperature: gas After injection, the temperature was maintained at 100°C for 8 minutes, then the temperature was raised at 10°C/min to 195°C, and then held at 195°C for 40 minutes. ) Set temperature: 250°C).

(Production example of catalyst)
_The metal oxide represented _by the _{empirical formula Mo12Bi0.60Fe1.8Ni5.0K0.09Rb0.05Mg2.0Ce0.75Ox is 50} % by _mass of the catalyst supported on silica with respect to the entire catalyst (100% _by mass). , prepared as follows.

5.9 kg of bismuth nitrate [Bi( _NO3 ) _3.5H2O ], 6.6 kg of cerium nitrate [Ce _{( NO3} ) _3.6H2O ] _, 14.7 kg of iron nitrate [Fe( _NO3 ) _3.9H2O ], 29.3 kg of nickel nitrate [Ni _{( NO3} ) _2.6H2O ], 10.4 kg of magnesium nitrate [Mg _{( NO3} ) _{2.6H 2 O} ], 0.18 kg of potassium nitrate [KNO ₃ ] and 0.15 kg of rubidium nitrate [RbNO ₃ ] were dissolved. This was added to 183.5 kg of silica sol containing 30% by mass of SiO ₂ , and finally 42.7 kg of ammonium paramolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O] was dissolved in 86.1 kg of water. was added to obtain a raw material mixture. The raw material mixture thus obtained was sent to a parallel flow spray dryer and dried at an inlet temperature of about 250° C. and an outlet temperature of about 140° C. to obtain a powder. Atomization of the raw material preparation liquid was carried out using an atomization device equipped with a plate-shaped rotor installed in the center of the upper part of the dryer. The obtained powder was pre-calcined in an electric rotary furnace at about 350° C. for 1 hour in an air atmosphere. A catalyst was obtained by calcining the pre-calcined powder at 590° C. for 2 hours in an air atmosphere. The required amount of catalyst was produced by repeating this catalyst preparation. The average particle size of the produced catalyst was 50.5 μm. The average particle size of the catalyst was measured using a laser diffraction/three-stage particle size distribution analyzer "LA-300" manufactured by Horiba, Ltd.

(Example 1)
The n-butene-containing gas was gasified through a vaporizer (vaporization step). At this time, the n-butene-containing gas in the outlet pipe of the vaporizer was heated with hot water and kept warm with a heat insulating material.

1200 g of the catalyst obtained in the above production example was placed in a SUS304 fluidized bed reactor (hereinafter also simply referred to as "reactor") having a tube diameter of 3 inches and a height of 950 mm. The reactor was then fed with a gas consisting of the n-butene-containing gas vaporized by the vaporization step, air, and nitrogen. Before supplying the n-butene-containing gas to the reactor, the n-butene-containing gas is warmed using hot water in the piping for supplying the n-butene-containing gas to the reactor, and a heat insulating material is used. kept warm. At this time, the molar ratio composition of the feed gas was n-butene-containing gas/air/nitrogen = 1.0/3.9/7.4, and the n-butene concentration in the feed gas was 8% by volume. , the flow rate F of the supplied gas was 920 NL/hr in terms of NTP. Next, an oxidative dehydrogenation reaction was performed at a reaction temperature T of 360° C. and a reaction pressure P of 0.05 MPaG to obtain a generated gas. At this time, the contact time between the catalyst and the supplied gas was 3.0 (g·sec/cc). The molar ratio composition of the _C4 components of the n-butene-containing gas is 1-butene:2-trans-butene:2-cis-butene:isobutene:n-butane:isobutane:butadiene=92.0:0.2. : 0.1:0.1:7.1:0.2:0.3. In this embodiment, the _C4 component corresponds to "n-butene-containing gas".

In the vaporization step, the temperature of the n-butene-containing gas in the outlet pipe of the vaporizer (the temperature of the n-butene-containing gas that passed through the vaporizer) was 57.9°C, and the n-butene in the outlet pipe of the vaporizer was The pressure of the contained gas (the pressure of the n-butene containing gas that passed through the vaporizer) was 0.27 MPa. In addition, the temperature of the n-butene-containing gas in the pipe supplying the n-butene-containing gas to the reactor (the temperature of the n-butene-containing gas supplied to the reactor) was 57.9°C. The pressure of the n-butene-containing gas in the pipe supplying the contained gas to the reactor (the pressure of the n-butene-containing gas supplied to the reactor) was 0.25 MPa. Based on these values, the linear velocity of the n-butene-containing gas in the outlet pipe of the vaporizer (the linear velocity of the n-butene-containing gas that has passed through the vaporizer) is calculated to be 50.2 cm/sec, and the n-butene The linear velocity of the n-butene-containing gas in the pipe supplying the contained gas to the reactor (the linear velocity of the n-butene-containing gas supplied to the reactor) was calculated to be 53.1 cm/sec. The vapor pressure of the n-butene-containing gas at 57.9° C. was estimated to be 0.62 MPa based on Antoine's equation.

Gas analysis at the reactor outlet was performed using a gas chromatograph directly connected to the reactor. The reaction results after 10 hours from the start of the reaction were that the n-butene conversion rate was 99.3%, the butadiene selectivity was 82.1%, and the butadiene yield was 81.5%. The oxygen concentration in the gas at the vessel outlet was 1.1% by volume.

(Comparative example 1)
In the vaporization step, the n-butene-containing gas in the outlet piping of the vaporizer was not heated, and the piping for supplying the n-butene-containing gas to the reactor before supplying the n-butene-containing gas to the reactor. The reaction was carried out in the same manner as in Example 1, except that the n-butene-containing gas was not heated. At this time, the temperature of the n-butene-containing gas in the outlet pipe of the vaporizer was 58.2° C., and the pressure of the n-butene-containing gas in the outlet pipe of the vaporizer was 0.22 MPa. Further, the temperature of the n-butene-containing gas in the pipe supplying the n-butene-containing gas to the reactor was 38.2° C., and the n-butene-containing gas in the pipe supplying the n-butene-containing gas to the reactor was The gas pressure was 0.20 MPa. Based on these values, the linear velocity of the n-butene-containing gas in the outlet pipe of the vaporizer is calculated to be 45.3 cm/sec, and the n-butene-containing gas in the pipe supplying the n-butene-containing gas to the reactor is The calculated linear velocity of the gas was 42.6 cm/sec. The vapor pressures of n-butene at 58.2° C. and 38.2° C. were estimated to be 0.62 MPa and 0.33 MPa, respectively, based on Antoine's equation.

The reaction results after 10 hours from the start of the reaction were that the conversion of n-butene was 89.5%, the selectivity of butadiene was 86.4%, and the yield of butadiene was 77.3%. The oxygen concentration in the gas at the outlet of the reactor was 0.37% by volume, confirming a decrease in the yield of butadiene.

(Example 2)
In the vaporization step, the n-butene-containing gas in the outlet piping of the vaporizer was not heated, and the piping for supplying the n-butene-containing gas to the reactor before supplying the n-butene-containing gas to the reactor. Within, the n-butene-containing gas was not heated, the gas amounts of the n-butene-containing gas and the oxygen-containing gas supplied to the reactor were adjusted, and the n-butene content in the outlet pipe of the vaporizer Same as Example 1, except that the linear velocity of the gas was 54.4 cm/sec and the linear velocity of the n-butene-containing gas in the pipe supplying the n-butene-containing gas to the reactor was 50.4 cm/sec. reacted to

The reaction results after 10 hours from the start of the reaction were that the n-butene conversion rate was 94.1%, the butadiene selectivity was 85.9%, and the butadiene yield was 80.9%. The oxygen concentration in the gas at the vessel outlet was 0.58% by volume. Although the butadiene conversion and yield are lower than the butadiene conversion of 99.3% and butadiene yield of 81.5% in Example 1, the butadiene conversion of 89.5% and 81.5% in Comparative Example 1 An improvement from the butadiene yield of 77.3% was seen.

(Example 3)
The gas amounts of the n-butene-containing gas and the oxygen-containing gas supplied to the reactor are adjusted, the linear velocity of the n-butene-containing gas in the outlet pipe of the vaporizer is 118.4 cm / sec, and the n-butene-containing gas is A reaction was carried out in the same manner as in Example 1, except that the linear velocity of the n-butene-containing gas in the pipe supplying the gas to the reactor was set at 126.5 cm/sec.

The reaction results after 10 hours from the start of the reaction were that the conversion of n-butene was 96.5%, the selectivity of butadiene was 86.0%, and the yield of butadiene was 83.0%. The oxygen concentration in the gas at the outlet of the vessel was 1.0% by volume, confirming a good yield of butadiene.

(Comparative example 2)
In Example 1, after the pressure of the n-butene-containing gas supplied to the reactor was made equal to or higher than the vapor pressure at the temperature of the n-butene-containing gas, the n-butene-containing gas and the oxygen-containing gas were supplied to the reactor. The amount of gas was adjusted, and the reaction was attempted under conditions equivalent to the linear velocity in Example 1. However, after adjusting the temperature of the n-butene-containing gas in the pipe supplying the n-butene-containing gas to the reactor to 57.9°C, the pressure of the n-butene-containing gas supplied to the reactor was adjusted to that temperature. When the vapor pressure of n-butene is 0.62 MPa, it is difficult to control the flow rate of n-butene in the outlet pipe of the vaporizer in the vaporization step and the flow rate of the n-butene-containing gas supplied to the reactor. As a result, the reaction temperature and the oxygen concentration in the outlet gas of the reactor fluctuated wildly, making it impossible to continue the reaction. One of these factors is presumed to be the condensation of the n-butene supplied to the reactor, but the present invention is not limited by this presumption.

(Comparative Example 3)
In Example 1, after the temperature of the n-butene-containing gas supplied to the reactor was set to 0 ° C., the gas amounts of the n-butene-containing gas and the oxygen-containing gas supplied to the reactor were adjusted. An attempt was made to carry out the reaction under conditions equivalent to the linear velocity of 1. However, in the step of lowering the temperature of the n-butene-containing gas supplied to the reactor, the pressure of the n-butene-containing gas supplied to the reactor becomes equal to or higher than the vapor pressure of n-butene at that temperature, and the vaporization process Disturbance of the pressure of the n-butene-containing gas in the outlet pipe of the vaporizer and the pressure of n-butene in the pipe supplying the n-butene-containing gas to the reactor, and the flow rate of n-butene supplied to the reactor disturbance was confirmed. One of these factors is presumed to be the condensation of the n-butene supplied to the reactor, but this presumption does not limit the present invention. For this reason, the pressure of the n-butene-containing gas in the outlet pipe of the vaporizer in the vaporization step and the pressure of the n-butene-containing gas in the pipe supplying the n-butene-containing gas to the reactor are less than the vapor pressure at that temperature. However, when the temperature of the n-butene-containing gas supplied to the reactor reaches around 0 ° C., the pressure of the n-butene-containing gas in the outlet pipe of the vaporizer in the vaporization step and the n-butene content The pressure of the n-butene-containing gas in the piping that supplies the gas to the reactor is disturbed, making it difficult to control the flow rate of the n-butene-containing gas supplied to the reactor, and as a result, the reaction temperature and the outlet gas of the reactor Since the oxygen concentration inside fluctuated, it became impossible to continue the reaction. One of these factors is assumed to be the condensation of impurities (water, etc.) contained in the gas supplied to the reactor, in addition to the n-butene-containing gas supplied to the reactor, on the surface of the piping, etc. However, the present invention is not limited by this speculation. The vapor pressure of n-butene at 0° C. was estimated to be 0.03 MPa based on Antoine's equation.

Claims (7)

A method for producing butadiene through an oxidative dehydrogenation reaction by supplying an n-butene-containing gas and an oxygen-containing gas to a reactor and bringing them into contact with a catalyst, comprising:
The temperature of the n-butene-containing gas supplied to the reactor is 5° C. or higher and 150° C. or lower, and
the pressure of the n-butene-containing gas supplied to the reactor is less than the vapor pressure of n-butene at the temperature of the n-butene-containing gas supplied to the reactor; and
The linear velocity of the n-butene-containing gas supplied to the reactor is 50 cm/sec or more ,
The catalyst has the following empirical formula:
Mo12BipFeqAaBbCcDdEeOx _{_} _ _{_} _ _{_} _ _{_} _ _{_} _ _{_} _ _{_} _ _{_} _ _{_}
(In the above empirical formula, A represents at least one element selected from the group consisting of nickel and cobalt, B represents at least one alkali metal element, C represents magnesium, calcium, strontium, barium, Represents at least one element selected from the group consisting of zinc and manganese, D represents at least one rare earth element, E represents at least one element selected from the group consisting of chromium, indium and gallium, O represents oxygen, p, q, a, b, c, d, e, and x represent the atomic ratios of bismuth, iron, A, B, C, D, E and oxygen to molybdenum-12 atoms, respectively; 0.1 ≤ p ≤ 5, 0.5 ≤ q ≤ 8, 0 ≤ a ≤ 10, 0.02 ≤ b ≤ 2, 0 ≤ c ≤ 5, 0 ≤ d ≤ 5, 0 ≤ e ≤ 5; x is the number of oxygen atoms required to satisfy the valence requirements of the other elements present.
A method for producing butadiene. The n-butene-containing gas is heated and/or kept warm in a pipe that supplies the n-butene-containing gas to the reactor;
The method for producing butadiene according to claim 1. Using reaction heat as a heat source for heating and/or keeping the n-butene-containing gas in the piping,
The method for producing butadiene according to claim 2. comprising a vaporization step of vaporizing the n-butene-containing gas using a vaporizer;
In the vaporization step,
The temperature of the n-butene-containing gas that has passed through the vaporizer is 15° C. or higher and 150° C. or lower, and
The pressure of the n-butene-containing gas that has passed through the vaporizer is less than the vapor pressure at the temperature of the n-butene that has passed through the vaporizer, and
The linear velocity of the n-butene-containing gas that has passed through the vaporizer is 50 cm/sec or more.
The method for producing butadiene according to any one of claims 1 to 3. Warming and/or keeping the n-butene-containing gas at the outlet pipe of the vaporizer;
The method for producing butadiene according to claim 4. Using reaction heat as a heat source for heating and/or keeping the n-butene-containing gas at the outlet pipe of the vaporizer,
The method for producing butadiene according to claim 5. wherein said reactor is a fluidized bed reactor;
The method for producing butadiene according to any one of claims 1 to 6.