JP5717393B2 - Butadiene manufacturing process - Google Patents

Description

  The present invention relates to a process for producing 1,3-butadiene (hereinafter referred to as butadiene).

  As a method for producing butadiene, a method of removing butane, butene, acetylenes, high-boiling components and low-boiling components using an extraction solvent for a fraction having 4 carbon atoms obtained by cracking naphtha is currently used. Has been. Butadiene is increasing in demand as a raw material for synthetic rubber, etc., but since the ethylene production method has shifted from naphtha cracking to ethane pyrolysis, the increase in butadiene production from naphtha cracking has not increased. The situation is not expected. On the other hand, methods for producing butadiene from butene are disclosed in JP 2010-90082 and JP 2010-90083. These methods disclose a method in which butene is oxidatively dehydrogenated, then rapidly cooled, moisture is removed, and then butadiene is absorbed and recovered by a solvent. However, the purity of butadiene obtained in these processes is not satisfactory. In order to be sufficient and further purified, a conventional process, a process for purifying butadiene from a naphtha cracked fraction obtained from naphtha cracking, must be used, thus producing butadiene. The problem remains that the process for doing so becomes complicated.

JP 2010-90082 JP 2010-90083

  A simple process from a gas containing butadiene produced by an oxidative dehydrogenation reaction by supplying a molecular oxygen-containing gas to a fluidized bed reactor using n-butene as a raw material, and contacting a catalyst carrying a metal oxide on a support. Provides a method for purifying butadiene.

As a result of intensive studies to solve the above problems, the present inventor has cooled the gas containing butadiene generated by the fluidized bed reaction, and then extracted and distilled using a specific solvent in a simple process. Has been found to be purified, and the present invention has been completed.
That is, the present invention is as follows.

[1] A method for producing butadiene, comprising the following steps (1) to ( 6 ).
Step (1): n-butene was fed to the fluidized bed reactor feed gas and the oxygen-containing gas comprising the steps step of generating a gas containing butadiene by oxidative dehydrogenation reaction is contacted with the catalyst (2): wherein butadiene step step of cooling in quench tower a gas containing (3): the boiling point of the gas containing the cooled butadiene is absorbed in a solvent 100 to 210 ° C., Ru obtain a solution containing butadiene step
Step (4): introducing the solution containing butadiene into a stripping tower and recovering a gas containing butadiene Step ( 5 ): compressing the recovered gas containing butadiene into liquefied butadiene, step removing the liquefied butadiene emissions or et water (6): step of removing the water is removed liquefied butadiene emissions or al high boiling component [2] the raw material gas, after removal of butadiene and isobutene The method according to claim 1, which is a fraction having 4 carbon atoms obtained by further removing butane from the fraction having 4 carbon atoms.

  According to the present invention, purified butadiene can be obtained from a gas containing butadiene produced by oxidative dehydrogenation of n-butene using a fluidized bed reactor.

Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as the present embodiment) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.
Hereinafter, a method necessary for producing butadiene purified from butadiene will be described.

[1] Step of obtaining gas containing butadiene (1) Raw material The raw material contains n-butene. Industrially, n-butene (specifically, 1-butene and / or 2-butene) contained in the fraction having 4 carbon atoms after removal of butadiene and isobutene can be suitably used. The ratio of 1-butene and 2-butene is not particularly limited, and 1-butene can be arbitrarily used in the range of 0 to 100% by weight, and 2-butene can be arbitrarily used in the range of 100 to 0% by weight. Moreover, although 2-butene has a trans body and a cis body, this ratio can also be arbitrarily used in the range of 100 to 0% by weight and 0 to 100% by weight, respectively. This raw material can also contain a small amount of butadiene and isobutene. Butadiene is 5% by weight or less, preferably 3% by weight or less, more preferably 1% by weight or less based on n-butene. Moreover, isobutene is 10 weight% or less with respect to n-butene, Preferably it is 0.1-6 weight%, More preferably, it is 0.5-3 weight%. This raw material may contain n-butane, isobutane, hydrocarbon having 3 or less carbon atoms, hydrocarbon having 5 or more carbon atoms, and the concentration of n-butene is 40% by weight or more, preferably 50% by weight or more. More preferably, 60% by weight or more of raw material is preferably used.

  It is also a preferable method to separate butane from a fraction having 4 carbon atoms by extractive distillation using a solvent before supplying the raw material to the fluidized bed reactor. As a solvent for extractive distillation for separating butane, one having a boiling point of 100 to 210 ° C. can be used. Specific examples of such a solvent include octane, nonane, decane, ethylcyclohexane, octene, nonene, toluene, ethylbenzene, xylene, cumene, vinylcyclohexene, dimethylformamide, dimethylacetamide, furfural, and n-methylpyrrolidone. . Among these, it is preferable to use octane, nonane, decane, ethylcyclohexane, toluene, ethylbenzene, xylene, cumene, dimethylformamide, dimethylacetamide, furfural, and n-methylpyrrolidone. As xylene, m-xylene, o-xylene, or p-xylene can be used alone or as a mixture.

  The raw material is, for example, a residual component obtained by extracting butadiene from a C4 fraction by-produced by naphtha pyrolysis, a C4 fraction by-produced by fluid catalytic cracking (FCC) of a heavy oil fraction, or by-product by catalytic conversion reaction of ethylene or ethanol. Can be obtained by separating isobutene from T4, MTBE, ETBE and dimerization reaction into a compound having 8 carbon atoms. Further, n-butene obtained by dehydrogenation reaction or oxidative dehydrogenation reaction of n-butane, n-butene by-produced in the catalytic conversion reaction of ethylene obtained by ethane pyrolysis or ethanol dehydration reaction, etc. are used. be able to. As this ethanol, biomass-derived ethanol can also be used as a suitable raw material.

  The concentration of n-butene in the raw material mixed gas supplied to the fluidized bed reactor is preferably at least 2% by volume from the viewpoint of butadiene productivity, and preferably 30% by volume or less from the viewpoint of suppressing the load on the catalyst. More preferably, it is 3-25 volume%, More preferably, it is 5-20 volume%. When the concentration of n-butene is high, precipitation of reaction products and coke on the catalyst increases, and the catalyst life tends to be shortened due to deterioration of the catalyst. Further, when the concentration of n-butene is low, the production amount of butadiene is small and there is no practical advantage.

The raw material mixed gas may contain paraffin, water, steam, hydrogen, nitrogen, carbon dioxide, carbon monoxide and the like. Examples of paraffin include methane, ethane, propane, butane, pentane, hexane, heptane, octane and nonane. Furthermore, after separating the target product butadiene from the reaction product, at least a part of the recovered unreacted butene can be recycled to the fluidized bed reactor.
One of the preferable methods is to contain water in the raw material mixed gas at 30 volume% or less, preferably 20 volume% or less, more preferably 10 volume% or less.

(2) Reactor The production of butadiene by the oxidative dehydrogenation reaction of n-butene is performed by a fluidized bed reaction method.
The fluidized bed reactor has a gas disperser, an interpolator, and a cyclone as its main constituent elements in the reactor, and has a structure in which the catalyst is brought into contact with the raw material gas while flowing. A fluidized bed reactor described in a fluidized bed handbook (published by Baifukan Co., Ltd., 1999) can be used, but a bubble fluidized bed reactor is particularly suitable. The heat generated from the reaction heat can be removed using a cooling pipe installed in the reactor.
Cooling tubes are placed in the rich and lean layers in the reactor and are operated to achieve the desired temperature.

(3) Reaction conditions n-butene and oxygen are subjected to the reaction. Usually, air is used as the oxygen source, but a gas in which oxygen concentration is increased by mixing oxygen with air, or air and nitrogen, helium, reaction gas, butadiene, n-butene, n-butane, isobutane, etc. A gas in which the oxygen concentration is reduced by mixing the gas after separation of the hydrocarbon compound, a gas with an increased oxygen concentration produced by a separation method using an oxygen separation membrane or the like, or an oxygen concentration is lowered Gas or the like can also be used. The molar ratio of oxygen to n-butene is preferably 0.5 to 1.5 (air / n-butene ratio is 2.5 to 7.5), more preferably 0.6 to 1.3 (air / N-butene ratio is in the range of 3.0 to 6.5).

  The method for introducing n-butene and oxygen is not limited as long as the gas used for the reaction has the above ratio. A gas containing n-butene and a gas containing air, an oxygen-enhanced gas or a gas having a reduced oxygen concentration may be mixed and introduced into the reactor filled with the catalyst, or introduced independently. Also good. Although the gas used for the reaction can be heated to a predetermined reaction temperature after being introduced into the reactor, it is usually preheated and introduced into the reactor for continuous and efficient reaction.

  The temperature of the dense layer of the fluidized bed reactor is 320 to 400 ° C., and the temperature of the dilute layer is controlled at −50 to + 20 ° C. with respect to the temperature of the dense layer. By setting the dense layer temperature to 320 ° C. or more, the dense layer temperature can be easily maintained, the monoolefin conversion can be maintained, and the operation can be continued stably. Combustion decomposition of the conjugated diolefin produced | generated by making dense layer temperature 400 degrees C or less can be suppressed. The preferred temperature of the dense bed of the fluidized bed reactor is 330-390 ° C, more preferably 340-380 ° C. Since the reaction for producing butadiene is an exothermic reaction, the reaction heat is removed by the cooling pipe, or the heat is supplied and supplied by the heating device so that the temperature of the concentrated layer and the diluted layer of the fluidized bed reactor is within the above range. Control by residual heat of raw material gas.

  The reaction pressure is preferably 0.01 to 0.4 MPa / G, more preferably 0.02 to 0.3 MPa / G, and still more preferably 0.03 to 0.2 MPa / G. The contact time between the raw material mixed gas and the catalyst is preferably 0.5 to 20 g · sec / cc, more preferably 1 to 10 g · sec / cc.

  The produced butadiene-containing gas flows out from the reactor outlet. By maintaining the oxygen concentration in the reactor outlet gas at 0.05 to 1.5% by volume, the reduction of the catalyst and the decomposition of the target product in the reactor can be effectively prevented, and the target product can be produced stably. it can. Since the oxygen concentration in the outlet gas of the reactor affects the decomposition of the target product and the secondary reaction in the reactor, it is a preferable aspect to maintain it at 1.5% by volume or less. The oxygen concentration in the reactor outlet gas is the amount of raw material gas n-butene supplied to the reactor, the amount of gas serving as the oxygen supply source, the reaction temperature, the pressure in the reactor, the amount of catalyst, and the supply to the reactor. It can be adjusted by changing the total gas amount. Preferably, it is controlled by controlling the amount of gas, for example, air, which is an oxygen supply source supplied to the reactor.

  The oxygen concentration in the reactor outlet gas can be measured by gas chromatography equipped with a thermal conductivity detector (TCD).

(4) Catalyst (4-1) Structure From the viewpoint of obtaining butadiene with a relatively high yield by a fluidized bed reaction, the catalyst having an oxide supported on a carrier preferably contains a carrier and Mo, Bi and Fe. The compositions of Mo, Bi and Fe are adjusted so as to form a desired oxide, and it is considered that oxidative dehydrogenation of butadiene from n-butene is performed by lattice oxygen in the oxide. In general, when lattice oxygen in the catalyst is consumed in the oxidative dehydrogenation reaction, oxygen vacancies are generated in the oxide. As the reaction proceeds, the reduction of the oxide also proceeds and the catalytic activity is deactivated. Therefore, in order to maintain the catalytic activity, it is necessary to quickly reoxidize the reduced oxide. Oxides containing Mo, Bi and Fe, in addition to the reactivity of n-butene to oxidative dehydrogenation of butadiene, dissociate and adsorb oxygen in the gas phase into the oxide and regenerate the consumed lattice oxygen. It is thought that it is also excellent in the reoxidation action. Therefore, even when the reaction is performed over a long period of time, it is considered that the reoxidation action of lattice oxygen is maintained, and the catalyst can be stably produced from n-butene without deactivation.

  Use of a catalyst carrying an oxide containing Mo, Bi, and Fe on a support for the production of butadiene by a fluidized bed system is advantageous in suppressing the generation of oxygenated compounds by combustion decomposition of the product butadiene and secondary reactions. Thus, butadiene can be obtained with a high yield. Although details are unknown, the reasons are as follows: (1) Because the acidity of the catalyst is suitable, the combustion decomposition and secondary reaction of butadiene on the catalyst are low. (2) The ability to adsorb reaction active sites on the produced butadiene Since butadiene is small, it can be considered that after butadiene is formed, it is quickly desorbed before being decomposed or reacted at the reaction active site.

  These composition ratios for making Mo, Bi and Fe easy to form a suitable oxide are as follows: Bi atomic ratio p to Mo atomic ratio 12 and Fe atomic ratio q are 0.1 ≦ p ≦ 5, It is considered that 0.5 ≦ q ≦ 8.

When the oxide contains a metal other than Mo, Bi and Fe, the empirical formula:
_{Mo 12 Bi p Fe q A a} B b C c D d E e O x
Wherein A is at least one element selected from nickel and cobalt, B is at least one element selected from alkali metal elements, and C is at least one selected from magnesium, calcium, strontium, barium, zinc and manganese. A seed element, D is at least one rare earth element, E is at least one element selected from chromium, indium and gallium, O is oxygen, p, q, a, b, c, d, e, and x represents the atomic ratio of bismuth, iron, A, B, C, D, E and oxygen to 12 atoms of molybdenum, 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, and x is the number of oxygen atoms necessary to satisfy the valence requirements of other elements present .)
It is preferable to be represented by In this specification, the “empirical formula” represents a composition composed of an atomic ratio of metals included in the formula and oxygen required in accordance with the total atomic ratio and oxidation number. In an oxide containing a metal that can take various oxidation numbers, it is practically impossible to specify the number of oxygen atoms, so the number of oxygen is formally expressed by “x”. For example, when a slurry containing Mo compound, Bi compound and Fe compound is prepared and dried and / or calcined to obtain an oxide, the atomic ratio of the metal contained in the slurry and the metal in the resulting oxide Since it may be considered that the atomic ratio is substantially the same, an empirical formula of the resulting oxide is obtained by adding O _x to the slurry composition formula. In the present specification, a formula that expresses a component that is intentionally controlled and its ratio, such as the charged composition of the slurry, is referred to as a “composition formula”. Therefore, in the case of the above example, O _x is excluded from the empirical formula. This is the “composition formula”.

Although the role of the components represented by A, B, C, D and E is not limited, it is generally estimated as follows in the field of oxide catalysts having Mo, Bi and Fe as essential components. That is, A and E improve the activity of the catalyst, B and C stabilize the structure of the desired oxide containing Mo, Bi and Fe, and D is considered to have the effect of reoxidation of the oxide. ing. If p, q, a, b, c, d, and e are in the preferred ranges, it can be expected that these effects are even higher.
In the above composition formula, more preferable compositions are 0.1 ≦ p ≦ 0.5, 1.5 ≦ q ≦ 3.5, 1.7 ≦ a ≦ 9, 0.02 ≦ b ≦ 1, 0.5. ≦ c ≦ 4.5, 0.02 ≦ d ≦ 0.5, 0 ≦ e ≦ 4.5, and more preferable composition is that B is rubidium, potassium or cesium, C is magnesium, and D is cerium. 0.15 ≦ p ≦ 0.4, 1.7 ≦ q ≦ 3, 2 ≦ a ≦ 8, 0.03 ≦ b ≦ 0.5, 1 ≦ c ≦ 3.5, 0.05 ≦ d ≦ 0 .3, 0 ≦ e ≦ 3.5. When A is nickel, B is rubidium, potassium or cesium, C is magnesium, and D is cerium, the conjugated diolefin yield is higher and its combustion decomposition is well suppressed, and the catalyst is resistant to reduction degradation. There is a tendency to be able to give.

  The carrier can be effectively used in the range of 30 to 70% by weight, preferably 40 to 60% by weight, based on the total of the carrier and the oxide. A supported catalyst containing an oxide containing Mo, Bi and Fe is obtained by a known method, for example, a first step of preparing a raw slurry, a second step of spray drying the raw slurry, and a second step. The obtained dried product can be obtained by a method including a third step. The carrier is preferably silica, alumina, titania or zirconia, and a more preferred carrier is silica. Silica is an inert carrier compared to other carriers, and has a good binding action with the catalyst without reducing the activity and selectivity of the catalyst with respect to the target product. In addition, by supporting the oxide on the support, physical properties suitable for fluidized bed reaction such as particle shape / size / distribution, fluidity, and mechanical strength can be imparted.

(4-2) Catalyst Preparation Method From the first step of preparing the raw material slurry, the second step of spray drying the raw material slurry, and the third step of firing the dried product obtained in the second step A preferred embodiment of the catalyst production method will be described taking a catalyst containing Mo, Bi and Fe as an example.

  In the first step, a catalyst raw material is prepared to obtain a raw material slurry, but molybdenum, bismuth, iron, nickel, cobalt, alkali metal elements, magnesium, calcium, strontium, barium, zinc, manganese, rare earth elements, chromium, indium Examples of the element source of each element of gallium include ammonium salts, nitrates, hydrochlorides, sulfates, and organic acid salts that are soluble in water or nitric acid. In particular, ammonium salts are preferable as the molybdenum source, and nitrates are preferable as the element sources of bismuth, iron, nickel, alkali elements, magnesium, zinc, manganese, rare earth elements, and each element. As described above, oxides such as silica, alumina, titania and zirconia can be used as the oxide carrier, but silica is preferably used as the carrier and silica sol is preferable as the silica source. With respect to the impurities of the silica sol, a silica sol containing 0.04 atom or less of aluminum per 100 atoms of silicon is preferably used, and more preferably a silica sol containing 0.02 atom or less of aluminum per 100 atoms of silicon is used. The raw slurry is prepared by adding ammonium salt of molybdenum dissolved in water to silica sol, and then adding nitrates of each element of bismuth, rare earth elements, iron, nickel, magnesium, zinc, manganese and alkali elements to water or nitric acid. This can be done by adding a solution dissolved in an aqueous solution. In this way, a raw slurry can be prepared. At that time, the order of the addition can be changed.

  In the second step, the raw material slurry obtained in the first step is spray-dried to obtain spherical particles. The atomization of the raw material slurry can be performed by a method such as a centrifugal method, a two-fluid nozzle method, and a high-pressure nozzle method which are usually carried out industrially. Next, the obtained particles are dried, and it is preferable to use air heated by steam, an electric heater or the like as a drying heat source. The temperature at the dryer inlet is 100 to 400 ° C, preferably 150 to 300 ° C.

  In the third step, the desired catalyst is obtained by calcining the dried particles obtained in the second step. The dried particles are preferably calcined at 150 to 500 ° C., if necessary, and then at 500 to 700 ° C., preferably 520 to 700 ° C. for 1 to 20 hours. Firing can be performed using a firing furnace such as a rotary furnace, a tunnel furnace, or a muffle furnace. The average particle diameter of the catalyst is 40 to 70 μm, and 90% or more of the catalyst particles are preferably distributed in the range of 20 to 100 μm.

[2] Step of quenching butadiene-containing gas in a quenching tower The quenching tower is preferably a multistage quenching tower having two or more sections, and more preferably has three or more sections. The multistage quenching tower sprays the aqueous solution extracted in each section upward from the extraction position to cool the gas. The extracted aqueous solution is preferably sprayed after cooling. Thereby, it is preferable to make the exit gas temperature of a quenching tower into 70 degrees C or less, More preferably, it controls in the range of 0-60 degreeC, More preferably, it is controlled in the range of 5-50 degreeC.

  The pressure of the quenching tower is preferably 0.01 to 0.4 MPa / G, more preferably 0.02 to 0.3 MPa / G, and still more preferably 0.03 to 0.2 MPa / G.

  It is preferable to control the pH of the bottom extraction liquid of the quenching tower to 7-8. By adding an aqueous solution containing at least one element or compound selected from Group Ia, Group IIa and ammonia to the circulating liquid of the quenching tower, the pH of the extracted liquid can be controlled to 7-8. As a preferable form of this addition, it is mentioned that the pH of the circulating liquid in the compartment provided in the upper part of the lowermost compartment of the quenching tower is controlled to 7.2 to 9, preferably 7.5 to 8.5. It is done. In order to control the pH of the circulating liquid, an aqueous solution containing at least one element or compound selected from Group Ia, Group IIa and ammonia is added to the circulating liquid. At least one selected from sodium, potassium and ammonia is added. It is preferred to use a seed element or compound, more preferably sodium.

  Each compartment can be filled with empty towers, trays, or packing. The number and arrangement of the circulating fluid may be appropriately determined using a spray nozzle in consideration of the contact between the fluid and the gas.

[3] Step of absorbing gas containing butadiene As the absorbing solvent, a solvent having a boiling point of 100 to 210 ° C is used. Specific examples of such a solvent include octane, nonane, decane, ethylcyclohexane, octene, nonene, toluene, ethylbenzene, xylene, cumene, vinylcyclohexene, dimethylformamide, dimethylacetamide, furfural, and n-methylpyrrolidone. . Among these, it is preferable to use octane, nonane, decane, ethylcyclohexane, toluene, ethylbenzene, xylene, and trimethylbenzene. As xylene, m-xylene, o-xylene, or p-xylene can be used alone or as a mixture.

  In this step, the butadiene-containing gas obtained in step (2) is compressed, and the cooled gas is introduced into the bottom of the absorption tower and brought into countercurrent contact with the absorption solvent to cause butadiene and other carbon numbers of 4 To absorb hydrocarbons mainly composed of The gas from which butadiene and other hydrocarbons mainly composed of carbon number 4 are removed is discharged as off-gas from the top of the absorption tower. An absorption solvent containing almost no hydrocarbon such as butadiene is introduced into the top of the absorption tower. The absorption tower is operated at a pressure of 0.3 to 1.5 MPa / G, preferably 0.5 to 1.0 MPa / G, and a temperature of 5 to 60 ° C., preferably 10 to 50 ° C.

As the absorption tower, a tower such as a packed tower or a plate tower can be used. Moreover, in order to suppress the heat_generation | fever inside an absorption tower, if a part of liquid in a tower is cooled with a cooler, absorption efficiency can be raised more.
The absorption solvent containing butadiene extracted from the bottom of the absorption tower is introduced into the step (4) of recovering butadiene.

[4] Stripping process The solution containing butadiene is preferably introduced into the middle stage of the stripping tower. The stripping tower has a pressure of 0.03 to 0.5 MPa / G, preferably 0.05 to 0.3 MPa / G, a tower top temperature of 0 to 90 ° C., and a tower bottom temperature of 100 to 190 ° C. More preferably, it is operated at 110 to 180 ° C. By setting the temperature to 100 ° C. or higher, hydrocarbons such as butadiene can be easily dissipated, and by setting the temperature to 190 ° C. or lower, generation of a polymer and tar can be prevented.

As the stripping tower, a packed tower or a plate tower can be used.
A gas containing butadiene is recovered from the top of the stripping tower, and an absorbing solvent containing almost no hydrocarbon such as butadiene is extracted from the bottom of the tower. Since the bottom liquid can be used as an absorbing solvent, it is preferably introduced at the top of the absorption tower. Since this absorbing solvent is contaminated by high boilers, tars, etc. after long-term use, it is preferable to purify the solvent continuously or intermittently. From the viewpoint of preventing contamination, it is preferable to add a polymerization inhibitor to the absorbing solvent.

[5] Step of removing water from butadiene The gas containing butadiene is compressed and liquefied and supplied to the upper part of the distillation column to separate the water, and the water is separated from the top of the column. Butadiene from which water has been removed is extracted from the bottom of the column. This distillation is operated at a pressure of 0.3 to 0.7 MPa / G, preferably 0.4 to 0.6 MPa / G, a tower top temperature of 40 to 60 ° C., and a tower bottom temperature of 45 to 65 ° C. In the dehydration step, a tower such as a packed tower or a plate tower can be used. It is preferable to add a polymerization inhibitor.

[6] Step of removing high boiling components from butadiene The butadiene extracted from the bottom of the column in the dehydration step is supplied to the middle stage of the distillation column to separate the high boiling components, and the purified butadiene is extracted from the top of the column. High boiling components such as 2-butene are extracted from the bottom of the column. This distillation is operated at a pressure of 0.3 to 0.7 MPa / G, preferably 0.4 to 0.6 MPa / G, a tower top temperature of 40 to 60 ° C., and a tower bottom temperature of 50 to 70 ° C. As the high boiling separation tower, a tower such as a packed tower or a plate tower can be used. It is preferable to add a polymerization inhibitor.

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

The n-butene conversion, butadiene selectivity and yield used to represent the reaction results are defined by the following equations.
n-butene conversion (%) = (number of moles of reacted n-butene) / (number of moles of supplied n-butene) * 100
Butadiene selectivity (%) = (number of moles of produced-butadiene) / (number of moles of reacted n-butene) * 100
Butadiene yield (%) = (produced-number of moles of butadiene) / (number of moles of n-butene supplied) * 100

The contact time is defined by the following equation.
Contact time (g · sec / cc) = W / F * 60 * 273.15 / (273.15 + T) * (P * 1000 + 101.325) /101.325
In the formula, W represents the catalyst filling amount (g), F represents the raw material mixed gas flow rate (cc / min, NTP conversion), T represents the reaction temperature (° C.), and P represents the reaction pressure (MPa).

  The analysis of the outlet oxygen was performed by gas chromatography directly connected to the reactor (GC-8A (manufactured by Shimadzu Corporation), analysis column: ZY1 (manufactured by Shinwa Kako), carrier gas: helium, column temperature: constant 75 ° C., TCD set temperature. : 80 ° C.).

  For analysis of n-butene, butadiene, methacrolein, etc., gas chromatography (GC-2010 (manufactured by Shimadzu Corporation)) directly connected to the reactor, analytical column: HP-ALS (manufactured by J & W), carrier gas: helium, column temperature : After gas injection, held at 100 ° C. for 8 minutes, then heated up to 195 ° C. at 10 ° C./minute, then held at 195 ° C. for 40 minutes, TCD • FID (hydrogen flame ion detector) set temperature: 250 ° C).

Example 1
(A) Preparation of catalyst An oxide having a composition of Mo ₁₂ Bi _0.60 Fe _1.8 Ni _5.0 K _0.09 Rb _0.05 Mg _2.0 Ce _0.75 was added at 50% by weight. Supported on silica, a catalyst was prepared as follows. Takes a silica sol 1835.4g containing 30 wt% of SiO2, 16.6 wt% of 58.7g of bismuth nitrate in nitric acid 413.3g _{[Bi (NO 3) 3 · 5H} 2 O ], cerium nitrate 65.7g [Ce (NO ₃ ) ₃ · 6H ₂ O], 146.7 g of iron nitrate [Fe (NO 3) 3 · 9H ₂ O], 293.4 g of nickel nitrate [Ni (NO ₃ ) ₂ · 6H ₂ O], 103. A solution in which 5 g of magnesium nitrate [Mg (NO ₃ ) ₂ .6H ₂ O], 1.8 g of potassium nitrate [KNO ₃ ] and 1.5 g of rubidium nitrate [RbNO ₃ ] was added was added, and finally water 860. A solution in which 427.4 g of ammonium paramolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O] was dissolved in 9 g was added. The raw material mixture obtained here was sent to a co-current type spray dryer and dried at an inlet temperature of about 250 ° C. and an outlet temperature of about 140 ° C. Nebulization of the preparation liquid was performed using an atomizing apparatus equipped with a dish-shaped rotor installed in the upper center of the dryer. The obtained powder was calcined in an electric furnace at 350 ° C. for 1 hour in an air atmosphere and then calcined in an air atmosphere at 590 ° C. for 2 hours to obtain a catalyst.

(B) Butadiene production reaction 1300 g of the catalyst obtained in the catalyst preparation step was placed in a reactor made of SUS304 having a tube diameter of 3 inches and a height of 950 mm, and n-butene as a fraction having 4 carbon atoms in this reaction tube: The raw material of n-butane: isobutane: isobutene = 53.9: 37.0: 8.4: 0.7 (weight ratio) was 405.9 g / Hr, and oxygen and nitrogen were 85.4 g / Hr and 816. The reaction was carried out at a rate of 3 g / Hr, a reaction temperature T− = 360 ° C., and a reaction pressure P = 0.05 MPa. At this time, the contact time between the catalyst and the mixed gas was 2.9 (g · sec / cc).
As for the reaction results 24 hours after the start of the reaction, the conversion of n-butene was 95.5%, the selectivity of butadiene was 83.1%, and the butadiene yield was 79.4%.

(C) Rapid cooling of reaction gas The reaction gas obtained in the step (b) is a SUS304 quenching tower having a bottom having a tube diameter of 200 mm and a height of 300 mm and a quenching portion having a tube diameter of 100 mm and a height of 1000 mm at the top. Introduced in the bottom. The quenching section was a three-stage system, and the liquid extracted from the bottom of the tower was sprayed to the upper, middle and lower stages at 100, 170 and 160 L / Hr, respectively. A 10% aqueous solution of sodium hydroxide was added to the spray solution to the middle so that the bottom extract had a pH of 7.2. Moreover, the spray liquid to the upper stage was cooled and sprayed to 45 degreeC through the heat exchanger. At this time, the exhaust gas temperature from the top of the quenching tower was 50 ° C.

(D) Butadiene absorption step The exhaust gas obtained in the step (c) was pressurized to 0.5 MPa / G with a compressor, and the gas controlled at 50 ° C. through a heat exchanger was adjusted to a tube diameter of 2.5 inches, It was introduced into the lower stage of an absorption tower made of SUS304 having a height of 3300 mm and filled with Raschig rings of 5 mmφ * 5 mm inside. M-Xylene (boiling point: 139.1 ° C.) cooled to 10 ° C. was supplied to the upper stage of this column at 5.0 kg / Hr and brought into countercurrent contact to absorb 99.8% of butadiene. The 50 ° C. m-xylene that absorbed the butadiene was extracted from the bottom.

(E) Butadiene recovery step The m-xylene containing butadiene obtained in the step (d) was recovered from SUS304 and filled with Raschig rings with a tube diameter of 2.5 inches and a height of 3000 mm and 5 mmφ * 5 mm inside. It was introduced in the middle of the tower. The recovery tower was operated so that the pressure was 0.11 MPa / G, the bottom liquid temperature was 110 ° C., and the top gas temperature was 25 ° C. A liquefied gas containing 93.2% by weight of butadiene is extracted from the top of the column at 188 g / Hr, and m-xylene not containing butadiene is extracted from the bottom of the column at 5.0 kg / Hr, and the absorbent in the step (c). As supplied.

(F) Step of removing water The liquefied gas containing butadiene extracted from the top of the column in the step (e) is temporarily stored in a tank, and has a tube diameter of 2.5 inches having a tray of 36 stages at 597 g / Hr, It was introduced into the upper stage of a SUS304 dewatering tower having a height of 3000 mm. The dehydration tower was operated such that the pressure was 0.60 MPa / G, the bottom liquid temperature was 53 ° C., and the top gas temperature was 51 ° C. From the top of the column, water was extracted from the system at 1 g / Hr, and butadiene containing almost no water was extracted from the bottom of the column at 596 g / Hr.

(G) Step of removing high-boiling components The butadiene extracted from the bottom of the column in step (f) was introduced into the middle stage of a SUS304 dewatering column having a diameter of 2.5 inches and a height of 3300 mm having 52 trays. . The dehydration tower was operated such that the pressure was 0.60 MPa / G, the bottom liquid temperature was 61 ° C., and the top gas temperature was 52 ° C. From the top of the column, 509 g / Hr of butadiene was extracted. The purity of this butadiene was 99.3% by weight, and the amount of acetylenes in butadiene was 10 ppm by weight or less. Further, butadiene containing 41% by weight of a high boiling point component was extracted from the tower bottom at 87 g / Hr.

A simple process from a gas containing butadiene produced by an oxidative dehydrogenation reaction by supplying a molecular oxygen-containing gas to a fluidized bed reactor using n-butene as a raw material, and contacting a catalyst carrying a metal oxide on a support. Purified butadiene can be produced.

Claims (2)

The manufacturing method of butadiene which has the process of the following processes (1) to ( 6 ).
Step (1): n-butene was fed to the fluidized bed reactor feed gas and the oxygen-containing gas comprising the steps step of generating a gas containing butadiene by oxidative dehydrogenation reaction is contacted with the catalyst (2): wherein butadiene step step of cooling in quench tower a gas containing (3): the boiling point of the gas containing the cooled butadiene is absorbed in a solvent 100 to 210 ° C., Ru obtain a solution containing butadiene step
Step (4): introducing the solution containing butadiene into a stripping tower and recovering a gas containing butadiene Step ( 5 ): compressing the recovered gas containing butadiene into liquefied butadiene, step removing the liquefied butadiene emissions or et water (6): step of removing the liquefied butadiene emissions which the water has been removed or al high boiling components 2. The method according to claim 1, wherein the raw material gas is a carbon 4 fraction obtained by further removing butane from a carbon 4 fraction after removing butadiene and isobutene. 3.