JP2013119530A - Method for producing conjugated diene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrially advantageous method for producing conjugated diene capable of continuing operation stably by preventing contamination of fume into reaction gas drawn out from a cooling tower for cooling obtained reaction gas, in a method for producing conjugated diene such as butadiene by a catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene.SOLUTION: In this method for producing conjugated diene in which a raw material gas containing a ≥4C monoolefin and a molecular oxygen-containing gas are subjected to an oxidative dehydrogenation reaction to be carried out in the presence of a catalyst to obtain reaction gas containing corresponding conjugated diene, and the obtained reaction gas is introduced into a cooling tower 2 to be brought into contact with cooling water and cooled, a plate part 2A is formed in the cooling tower 2, and the mass ratio between a flow rate of the reaction gas introduced into the cooling tower 2 and a flow rate of the cooling water supplied into the plate part 2A of the cooling tower 2 is set at ≤0.3.

Description

  The present invention relates to a method for producing a conjugated diene, and more particularly to a method for producing a conjugated diene such as butadiene by a catalytic oxidative dehydrogenation reaction of a monoolefin having 4 or more carbon atoms such as n-butene.

  A method for producing a conjugated diene such as butadiene by subjecting a monoolefin such as n-butene to an oxidative dehydrogenation reaction in the presence of a catalyst is conventionally known.

  Further, among butadiene production by industrial catalytic oxidative dehydrogenation of n-butene, as a typical method, a mixture containing 2-butene, butane, etc. in addition to 1-butene (hereinafter, this mixture is referred to as “ BBSS] may be reacted with an oxygen-containing gas in the presence of a catalyst to obtain a reaction gas containing 1,3-butadiene, in which high purity butadiene is obtained from the reaction gas. Prior to the separation and recovery of the reaction gas, the reaction gas is supplied to a quenching tower (cooling tower) in advance and brought into contact with cooling water to cool, thereby condensing most of the water vapor in the reaction gas, and also by-products having a high boiling point. The organic acid or the like is also condensed and removed from the reaction gas.

  In the reaction gas withdrawn from the top of the quenching tower, fine solid particles of by-products exist as fumes in the quenching tower as a cause of the blockage of the process. A method of removing the fumes by introducing a reactive gas into a scrubber has been proposed (Japanese Patent Laid-Open No. 61-5030).

  On the other hand, the generation of fumes containing solid particulates is generally known to cause clogging of equipment and catalyst deterioration in chemical processes using catalytic gas phase oxidation other than butadiene production. For example, Japanese Patent Application Laid-Open No. 56-117372 discloses a method for producing methacrylic acid from a hydrocarbon such as isobutylene in order to remove such solid fine particles, and cooling by introducing a reaction gas into a methacrylic acid condenser. After that, it is described that the amount of solid fine particles having a particle size of about 1 micron mixed in the exhaust gas is reduced by adjusting the flow rate of the circulating coolant used in the methacrylic acid condensing apparatus.

JP 61-005030 A Japanese Patent Laid-Open No. 56-117372

  When the methods described in Patent Documents 1 and 2 are used, the problem of clogging due to fumes in the quenching tower for cooling the reaction gas in the production of butadiene could be avoided to some extent. However, it is not an industrially advantageous method because it requires complicated processes and large-scale equipment. In addition, Patent Document 1 describes that solid fine particles having a particle size smaller than that of solid fine particles having a particle size of about 1.0 μm (0.5 μm or less) exist in the fumes in the quenching tower. However, according to the study by the present inventors, the solid fine particles having a particle diameter of 0.5 μm or less cannot be sufficiently removed by means of conventional fume removal such as a scrubber or a filter, These accumulated in the quenching tower and the gas extraction pipe at the top of the tower, causing clogging, and there was a problem that long-term stable operation could not be performed in an industrial scale butadiene continuous production process.

  The present invention has been made in view of the above problems, and in a method for producing a conjugated diene such as butadiene by a catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene, the reaction gas obtained by the reaction is cooled by a cooling tower. An object of the present invention is to provide an industrially advantageous method for producing a conjugated diene capable of preventing fume from being mixed into a reaction gas extracted from a cooling tower and allowing stable operation during cooling. To do.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have increased the contact efficiency between the reaction gas and the cooling water in the cooling tower, whereby a solid having a particle size of 0.5 μm or less suspended in the reaction gas. Based on the idea that fine particles can be separated from gas more efficiently, a cooling tower with a specific structure is used, and the ratio of the reaction gas and cooling water supplied to the cooling tower is controlled, so that The present inventors have found a method capable of reducing solid fine particles having a particle size of 0.5 μm or less.

  The present invention has been achieved on the basis of such findings, and the following [1] to [6] are summarized.

[1] By performing an oxidative dehydrogenation reaction between a source gas containing a monoolefin having 4 or more carbon atoms and a molecular oxygen-containing gas in the presence of a catalyst, a reaction gas containing a corresponding conjugated diene is obtained and obtained. In the method for producing a conjugated diene, wherein the reaction gas is introduced into a cooling tower and brought into contact with cooling water for cooling, the step gas is formed in the cooling tower, and the reaction gas introduced into the cooling tower The mass ratio of the flow rate of this and the flow rate of the cooling water supplied to the shelf step part of this cooling tower is 0.3 or less, The manufacturing method of the conjugated diene characterized by the above-mentioned.

[2] The method for producing a conjugated diene according to [1], wherein the cooling water is supplied from two or more different supply locations in the height direction of the cooling tower and is brought into contact with the reaction gas.

[3] The ratio of the flow rate of the cooling water supplied to other than the shelf portion of the cooling tower with respect to the total flow rate of the cooling water supplied to the cooling tower is in the range of 0 to 35%. [2] The method for producing a conjugated diene according to [2].

[4] The method for producing a conjugated diene according to any one of [1] to [3], wherein the tray of the shelf in the cooling tower includes a sheave tray.

[5] The method for producing a conjugated diene according to any one of [1] to [4], wherein the catalyst is a composite oxide catalyst represented by the following general formula (1).
Mo _a Bi _b Q _c Ni _{d Re} X _f Y _g Z _h Si _i O _j (1)
(Wherein Q is cobalt (Co) and / or chromium (Cr), R is iron (Fe), aluminum (Al), gallium (Ga), zirconium (Zr), lead (Pb), niobium (Nb ), Tantalum (Ta), hafnium (Hf), and manganese (Mn), at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), zinc (Zn), cerium ( Ce) and at least one element selected from the group consisting of samarium (Sm), and Y is a group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and thallium (Tl). And at least one element selected from the group consisting of boron (B), phosphorus (P), arsenic (As), and tungsten (W). In addition, a to j represent atomic ratios of the respective elements, and when a = 12, b = 0.5 to 7, c = 0 to 10, d = 0 to 10 (provided that c + d = 1) 10), e = 0.05-3, f = 0-2, g = 0.04-2, h = 0-3, i = 5-48, and j is the oxidation of other elements It is a numerical value that satisfies the condition.)

[6] Gas containing 1-butene, cis-2-butene, trans-2-butene or a mixture thereof obtained by dimerization of ethylene as the raw material gas, dehydrogenation or oxidative dehydrogenation of n-butane Any one of [1] to [5], which is a gas containing a large amount of hydrocarbons having 4 carbon atoms, which is obtained when fluidizing the butene fraction or heavy oil fraction produced by The manufacturing method of conjugated diene of description.

  According to the present invention, in the method for producing a conjugated diene such as butadiene by the catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene, a complicated process or large process is required for cooling the reaction gas obtained by the reaction in the cooling tower. Without requiring a large-scale facility, fumes are effectively washed and removed in the cooling tower with cooling water, and fumes into the reaction gas extracted from the cooling tower, particularly solid fine particles having a particle size of 0.5 μm or less. It is possible to prevent the contamination and continue the operation stably for a long time.

It is a systematic diagram which shows embodiment of the manufacturing method of the conjugated diene of this invention. 4 is a graph showing changes with time in gas flow rate and filter secondary side pressure in Example 1. It is a graph which shows a time-dependent change of the gas flow rate in Example 2, and a filter secondary side pressure. It is a graph which shows the time-dependent change of the gas flow rate and filter secondary side pressure in the comparative example 1. 4 is a SEM photograph of solid content captured by a filter in Comparative Example 1.

  Hereinafter, embodiments of the method for producing a conjugated diene of the present invention will be described in detail. However, the description described below is an example (representative example) of an embodiment of the present invention, and the present invention is limited to these contents. Not.

  The method for producing a conjugated diene according to the present invention is performed by supplying a raw material gas containing a monoolefin having 4 or more carbon atoms and a molecular oxygen-containing gas to a reactor and performing an oxidative dehydrogenation reaction in the presence of a catalyst. In a method for producing a conjugated diene, wherein a reaction gas containing a conjugated diene is obtained, and the reaction gas is introduced into a cooling tower and brought into contact with cooling water to be cooled, the shelf has a shelf, preferably a sheave tray. A cooling tower is used, and the mass ratio of the reaction gas supplied to the cooling tower and the cooling water supplied to the shelf of the cooling tower is controlled to 0.3 or less.

Hereinafter, the present invention will be described in detail with reference to FIG. 1 showing a system diagram of a production process in the case of producing butadiene from n-butene according to the method for producing a conjugated diene of the present invention. Not only the production of butadiene from butene (1-butene, 2-butene (cis-2-butene, trans-2-butene)), but also carbon atoms of 4 or more, preferably carbon atoms, such as pentene, methylbutene, dimethylbutene, etc. The present invention is effectively applied to the production of corresponding conjugated dienes by catalytic oxidative dehydrogenation of monoolefins of several 4-6. These monoolefins do not necessarily need to be used in an isolated form, and can be used in the form of any mixture as required. For example, when 1,3-butanediene is to be obtained as the conjugated diene as the target product, high-purity 1-butene or 2-butene can be used as a raw material, but it is produced as a by-product in the aforementioned naphtha decomposition. C ₄ is obtained by separating butadiene and i-butene from fraction (BB) n- butenes (1-butene and 2-butene) fraction as a main component (BBSS) and n- dehydrogenation or oxidative dehydration of butane A butene fraction produced by an elementary reaction can also be used. The main component as used herein refers to a component that occupies 40 vol% or more, preferably 60 vol% or more, more preferably 75 vol% or more, and particularly preferably 99 vol% or more with respect to the raw material gas. Further, the source gas may contain an arbitrary impurity as long as the effects of the present invention are not impaired. Specific examples of impurities that may be contained include saturated hydrocarbons such as propane, n-butane, i-butane, and pentane, olefins such as propylene and pentene, dienes such as 1,2-butadiene, methylacetylene, and vinyl. Examples include acetylenes such as acetylene and ethylacetylene. The amount of these impurities in the source gas is usually 60 vol% or less, preferably 40 vol% or less, more preferably 1 vol% or less. If the amount of impurities in the raw material gas is too large, the concentration of 1-butene or 2-butene, which are the main raw materials, decreases and the reaction becomes slow, and undesirable by-products tend to increase.

  In FIG. 1, 1 is a reactor, 2 is a quench tower (cooling tower), 4, 5 and 9 are coolers (heat exchangers), 6 and 10 are drain pots, and numerals 100 to 111 are pipes.

  As the reactor 1, a known reactor such as a fixed bed multitubular reactor, a fluidized bed reactor, and a plate reactor can be used. Here, a fixed bed multitubular reactor will be described as an example.

[Reaction process]
In the reaction process, n-butene as a raw material or a mixture containing n-butene such as the above-mentioned BBSS is gasified by a vaporizer (not shown), and an inert gas such as nitrogen gas, air (containing molecular oxygen) Gas) and water (water vapor) are introduced, and the mixed gas is heated to about 150 to 250 ° C. by a preheater (not shown), and then supplied to the reactor 1 filled with the catalyst through the pipe 100. The raw material, an inert gas such as nitrogen gas, air, and water (steam) may be supplied directly to the reactor 1 through separate pipes, but when the reactor 1 is a fixed bed reactor, it is mixed uniformly. The state is preferably supplied to the reactor 1. This is a merit that it is possible to prevent a situation in which a non-uniform mixed gas partially forms a squeal in the reactor or a raw material having a different composition is supplied to each tube in a multi-tube reactor. Because there is. When the reactor 1 is a fluidized bed reactor, avoiding the explosion range may be facilitated by separately supplying a combustible gas and a gas containing oxygen to the reactor.

The molecular oxygen-containing gas is usually a gas containing molecular oxygen of 10 vol% or more, preferably 15 vol% or more, more preferably 20 vol% or more, and specifically preferably air. From the viewpoint of cost required for industrially preparing the molecular oxygen-containing gas, the molecular oxygen content of the molecular oxygen-containing gas is 50 vol% or less, preferably 30 vol% or less, more preferably 21 vol%. The following is preferable. Moreover, the molecular oxygen-containing gas may contain an arbitrary impurity as long as the effects of the present invention are not impaired. Specific examples of impurities that may be included include nitrogen, argon, neon, helium, CO, CO ₂ , and water. In the case of nitrogen, the amount of these impurities in the molecular oxygen-containing gas is usually 90 vol% or less, preferably 85 vol% or less, more preferably 80 vol% or less. In the case of components other than nitrogen, it is usually 10 vol% or less, preferably 1 vol% or less. If the amount of impurities in the molecular oxygen-containing gas is too large, it tends to be difficult to supply oxygen necessary for the reaction.

  In addition, when supplying the raw material gas to the reactor 1, an inert gas such as nitrogen gas and water (water vapor) may be supplied. Examples of the inert gas include nitrogen, argon, carbon dioxide and the like, but nitrogen is preferable from an economical viewpoint. The inert gas adjusts the concentration of flammable gas such as butene and oxygen so that the reaction gas does not form squeal, so water (steam) is composed of flammable gas and oxygen in the same way as the inert gas. For reasons of adjusting the concentration and suppressing coking of the catalyst, it is preferable to supply these together with butene and a molecular oxygen-containing gas to the reactor 1 as a raw material gas.

  The reaction gas is subjected to a recovery step of absorbing and separating hydrocarbons mainly composed of conjugated dienes by contacting with a solvent after cooling in a cooling tower. A residual gas mainly composed of oxygen may be circulated and supplied to the reactor 1. Thereby, the raw material cost can be greatly reduced, which is industrially advantageous. In this case, the oxygen concentration in the residual gas may be outside the preferable oxygen concentration range of the molecular oxygen-containing gas. At this time, the residual gas may be brought into contact with a solvent having a boiling point higher than that of the absorbing solvent to separate the absorbing solvent contained in a trace amount, or the remaining combustible material may be removed using a known technique such as a catalytic combustion apparatus. The concentration of oxygen contained in the residual gas is measured using a known technique such as an oxygen concentration meter or gas chromatography, and the amount of molecular oxygen-containing gas newly supplied to the reactor is adjusted according to the result. It is desirable.

  Since the raw material gas supplied to the reactor 1 is a mixture of oxygen and combustible gas, each gas (butene, air, and optionally inert gas and water (water vapor) is used so as not to enter the explosion range. The composition of the reactor inlet is controlled while monitoring the flow rate with a flow meter installed in the piping that supplies)), and adjusted to the following raw material gas composition, for example.

<Raw gas composition>
n- butene: _{C 4} fraction 50～100Vol% of the total
C ₄ fractions total: 5-15 vol%
O _{2: C 4} 40~120vol% relative fraction total
N _{2: C 4} 500~1000vol% relative fraction total
H ₂ O: _{C 4} fraction 90～900Vol% of the total

  The explosion range here is a range having a composition in which a mixed gas of oxygen and combustible gas is ignited in the presence of some ignition source. It is known that if the concentration of combustible gas is lower than a certain value, it will not ignite even if an ignition source is present, and this concentration is called the lower explosion limit. It is also known that if the concentration of combustible gas is higher than a certain value, it will not ignite even if an ignition source is present, and this concentration is called the upper limit of explosion. Each value depends on the oxygen concentration. In general, the lower the oxygen concentration, the closer the values are, and the two match when the oxygen concentration reaches a certain value. The oxygen concentration at this time is called a critical oxygen concentration. If the oxygen concentration is lower than this, the mixed gas will not be ignited regardless of the concentration of the combustible gas.

  When starting the catalytic oxidative dehydrogenation reaction of the present invention, the oxygen concentration at the inlet of the reactor is limited oxygen by adjusting the amount of molecular oxygen-containing gas such as air, inert gas, and water vapor supplied to the reactor first. Start supplying flammable gas after reducing the concentration below, then increase the supply of flammable gas and molecular oxygen-containing gas such as air so that the flammable gas concentration is higher than the upper limit of explosion. It is good to go.

  In addition, even if it is outside the explosion range, it may ignite if kept for a certain period of time under a certain temperature and pressure condition. This holding time is called ignition delay time. When designing around the reactor, it is necessary to design the residence time of the raw material piping and the reaction gas piping to be less than the ignition delay time. Although the ignition delay time depends on temperature, pressure, and composition, it cannot be generally stated. However, the residence time of the mixed raw material pipe is 1000 seconds or less, the residence time of the reaction gas pipe is 10 seconds or less, or the reaction gas is 350 within 10 seconds. It is desirable to cool to below.

  The reactor 1 is filled with an after-mentioned oxidative dehydrogenation reaction catalyst, and n-butene reacts with oxygen on the catalyst to produce butadiene and water. This oxidative dehydrogenation reaction is an exothermic reaction, and the temperature rises due to the reaction. The reaction temperature is preferably adjusted to a range of 280 to 400 ° C. Therefore, the reactor 1 is appropriately cooled (for example, a heat medium (dibenzyl Heat removal by toluene, molten salt, water vapor, etc.) and the temperature of the catalyst layer is controlled to be constant.

  The pressure in the reactor 1 is not particularly limited, but the lower limit is usually 0 MPaG or more, preferably 0.02 MPaG or more, more preferably 0.05 MPaG or more. As this value increases, there is an advantage that a large amount of reaction gas can be supplied to the reactor. On the other hand, the upper limit is usually 0.5 MPaG or less, preferably 0.3 MPaG or less, more preferably 0.1 MPaG. As this value decreases, the explosion range tends to narrow.

  The residence time of the reactor 1 is not particularly limited, but the lower limit is usually 0.36 seconds or longer, preferably 0.72 seconds or longer, more preferably 1.2 seconds or longer. There is a merit that the higher the value, the higher the conversion rate. On the other hand, the upper limit is usually 7.2 seconds or less, preferably 3.6 seconds or less, and more preferably 1.8 seconds. The smaller this value, the smaller the reactor.

  The concentration of the conjugated diene such as butadiene corresponding to the monoolefin such as n-butene in the raw material gas contained in the reaction gas obtained by the catalytic oxidative dehydrogenation reaction in the reactor 1 is the monoolefin contained in the raw material gas. Although it depends on the concentration of, it is usually 1 to 15 vol%, preferably 5 to 13 vol%, more preferably 9 to 11 vol%. The greater the concentration of the conjugated diene in the reaction gas, the lower the recovery cost, and the lower the advantage, there is an advantage that side reactions such as polymerization are less likely to occur when compressed in the next step. In addition, unreacted monoolefin may also be contained in the reaction gas, and its concentration is usually 0 to 7 vol%, preferably 0 to 4 vol%, more preferably 0 to 2 vol%.

  When the composition at the inlet of the reactor 1 is above the upper explosion limit, the composition at the outlet of the reactor 1 is also usually above the upper explosion limit and there is no risk of explosion. However, there is a possibility that the concentration of hydrocarbons in the gas decreases and enters the explosion range in a subsequent recovery step in which the reaction gas is brought into contact with the absorbing solvent and hydrocarbons such as olefins and conjugated dienes are absorbed by the solvent. In order to avoid this, it is conceivable that the reaction gas is diluted with an inert gas such as nitrogen and then brought into contact with the absorbing solvent. However, the composition of the outlet of the reactor 1 or the outlet of the quench tower 2 is less than the critical oxygen concentration. It is easier to adjust the inlet conditions and reaction conditions of the reactor 1. For example, an oxygen concentration meter may be installed at the outlet of the quench tower 2, and the flow rate of air supplied to the reactor 1 or the reaction temperature may be adjusted so that the measured oxygen concentration is 8 vol% or less.

The flow rate difference between the inlet and the outlet of the reactor 1 depends on the flow rate of the raw material gas at the reactor inlet and the flow rate of the reaction gas at the reactor outlet, but the ratio of the outlet flow rate to the normal inlet flow rate is 100. It is -110 mol%, Preferably it is 102-107 mol%, More preferably, it is 103-105 mol%. The outlet flow rate increases because the number of molecules increases stoichiometrically in the reaction in which butene is oxidatively dehydrogenated to produce butadiene and water, and in the reaction in which CO and CO ₂ are produced as a side reaction. A small increase in the outlet flow rate is not preferable because the reaction does not proceed, and an excessive increase in the outlet flow rate is not preferable because CO and CO ₂ increase due to side reactions.

[Cooling process]
The reaction gas from the reactor 1 is then fed from the pipe 101 to the bottom of the quench tower (cooling tower) 2. Although not shown, a heat exchanger for cooling may be installed between the reactor 1 and the quench tower 2 to recover heat from the reaction gas.

  In the quench tower 2, the reaction gas is brought into contact with cooling water to cool the reaction gas. In the quench tower 2, in addition to cooling the reaction gas, water-soluble by-products such as acetic acid are removed.

  As described above, it is considered that fine solid particles having a particle size of 0.5 μm or less, which are by-products in this cooling step, are contained in the fume. As will be described later, the fine solid particles are mainly composed of terephthalic acid and isophthalic acid. These cannot be sufficiently removed with a general scrubber because the concentration of fine particles in the gas is low. The removal method using a filter is an operation such as filter replacement in an industrial-scale plant having a plant that produces conjugated dienes on the scale of thousands to tens of thousands of tons per year because the filter is clogged in a short period of time. This is not preferable from the viewpoint of equipment costs such as management and filter costs.

  As the type of the quench tower 2, known ones such as a plate tower, a packed tower, and a spray tower can be used, and several methods may be combined. However, in the present invention, at least a part of the shelf 2 A is formed. Use a cooling tower. For example, a portion near the tower bottom may be contaminated with a high boiling point compound, so that a spray may be used and the upper side of the tower may be a shelf. Since the packed bed is vulnerable to dirt, it is desirable to use it in areas that are difficult to get dirty in combination with other methods, rather than being used near the tower bottom.

  As a tray type in the shelf step portion, a known type such as a sheave type tray, a dual flow type tray, a baffle type tray can be used. Part of the tray preferably includes a sheave-type tray. Further, a plurality of types of trays may be combined, such as a baffle tray near the tower bottom and a sheave tray near the tower top.

  The actual number of shelves 2A of the quench tower 2 is usually 6 to 100, preferably 10 to 30. If there are too few shelves, there will be some demilits that cannot be cooled sufficiently or water-soluble by-products cannot be removed. There are disadvantages that expand the range. Moreover, like the quench tower 2 shown in FIG. 1, when forming an empty tower part (cooling water spray area | region) in the lower part of the shelf part 2A, the shelf part 2A is 1/1. It is preferable to set it as a 1 to 1/2 area | region, and it is preferable to make an empty tower part into a 1/4 to 1/20 area | region of the total height of the quench tower 2. FIG.

  The cooling water is supplied from the top of the quench tower 2 (pipe 102), extracted from the bottom of the tower (pipe 103), and controlled so that the level of the liquid level at the bottom of the tower is constant. ) (Pipe 106). Cooling water supplied from the top of the tower includes water condensed in the reaction gas, condensed at least part of the water extracted from the bottom of the quench tower, fresh water, water discharged in other processes, etc. Can be used. Further, at least a part of the water may be supplied to the middle stage and / or the bottom of the tower, or at least a part of the water may be extracted from the middle stage of the tower. The extracted water may be circulated to the tower (pipes 104 and 105) or sent to a wastewater treatment process (pipes 106). The temperature of the water supplied to the quench tower 2 is desirably controlled, and in particular, when the water extracted from the tower is circulated to the tower, it is desirably cooled (cooler 4). Since water extracted from the tower may contain solids, it is desirable to separate and remove the solids by a known means such as a strainer. In addition, when cooling the water extracted from the quench tower, precipitates may be generated and the cooler may become dirty, so even if two or more coolers are installed in parallel and the operation / washing is switched alternately. good.

  In the quench tower 2 shown in FIG. 1, the cooling water supplied from the top of the tower through the pipe 102 is extracted from the bottom of the tower through the pipe 103, and a part of the cooling water is sent to the waste water treatment process (not shown) through the pipe 106 by the pump 3. A part of the remaining part is circulated through the pipe 104 to the intermediate position in the height direction of the shelf part 2A of the quench tower 2, and the other part is circulated from the pipe 105 below the shelf part 2A. Yes. In this way, it is preferable to supply cooling water at two or more different locations in the height direction of the quench tower because the effect of removing fine solid particles having a particle size of 0.5 μm or less can be enhanced.

In the present invention, the reaction gas supplied to the quench tower 2 and the quench tower in order to efficiently remove minute solid particles having a particle size of 0.5 μm or less in the fumes contained in the reaction gas in the quench tower 2. The mass ratio of the flow rate of the cooling water supplied to the second shelf step 2A (hereinafter sometimes referred to as “reaction gas / shelf step cooling water flow rate ratio”) is set as follows.
Reaction gas flow rate / cooling water flow rate supplied to the shelf ≦ 0.3
Here, the cooling water supplied to the shelf step portion 2A of the quench tower 2 is the cooling water passing through the shelf step portion 2A, and if it is the shelf step portion 2A of the quench tower 2 shown in FIG. The flow rate of the cooling water that is supplied to the top of the quench tower 2 and flows down the shelf 2A from the top to the bottom, and is supplied from the pipe 104 to the intermediate position in the height direction of the shelf 2A. It becomes the total flow rate of the cooling water flow rate flowing down a part of.

  When the reaction gas / shelf cooling water flow rate ratio is more than 0.3, there is a tendency that a sufficient fine particle removal effect cannot be obtained. The smaller the reaction gas / shelf cooling water flow ratio, the better from the viewpoint of particle removal effect, but a large amount of cooling water is required to reduce the reaction gas / shelf cooling water flow ratio and the cooling water cost increases. To do. For this reason, it is preferable that the reaction gas / shelf cooling water flow rate ratio is 0.1 to 0.3, particularly 0.15 to 0.22.

  In addition, even if the cooling water that passes through the shelf 2A, if the supply position is excessively low, sufficient time for removing the fine particles is obtained due to the short time and basin of the supplied cooling water passing through the shelf 2A. The effect is not obtained. Therefore, 10% or more, for example, 15 to 100%, preferably 50 to 80% of the cooling water supplied to the shelf 2A of the quench tower 2 is preferably supplied from the top of the quench tower 2. In addition, the cooling water supplied to the intermediate position in the height direction of the shelf step portion 2A is 1/4 or more of the theoretical plate number, for example, about 1/3 to 1 / 1.3 from the upper portion of the shelf step portion 2A. It is preferable to be supplied at a height position. If this supply position is too low, the particulate removal effect will be inferior, and if it is too high, the effect of improving the particulate removal effect by supplying cooling water at a plurality of locations in the height direction of the quench tower 2 cannot be sufficiently obtained. .

  Further, in the quench tower 2 shown in FIG. 1, cooling water that is supplied to a place other than the shelf step portion 2 </ b> A and does not pass through the shelf step portion 2 </ b> A like the cooling water supplied from the pipe 105 to the lower portion of the shelf step portion 2 </ b> A. Is 0 to the total cooling water flow rate supplied to the quench tower 2 (in the quench tower 2 in FIG. 1, the total of the cooling water from the pipe 102, the cooling water from the pipe 104, and the cooling water from the pipe 105). It is preferably 35%, particularly 0 to 20%. By supplying cooling water to locations other than the shelf step portion 2A, the high boiling component is solidified and separated, so that the quench tower is prevented from being contaminated by the high boiling component. If the amount of cooling water is excessively large, the effect of removing fine particles by supplying cooling water to the shelf 2A is impaired.

  In addition, there is no restriction | limiting in particular about the temperature of a cooling water, A normal cooling water temperature condition is employ | adopted. Generally, the temperature of the cooling water from the top of the quench tower 2 is preferably 5 to 70 ° C., the liquid temperature at the bottom of the quench tower 2 is 50 to 90 ° C., and the temperature at the top of the tower is about 10 to 70 ° C. It is preferable to adjust so that.

  The reaction gas cooled in the quench tower 2 is extracted from the top of the quench tower 2 through the pipe 107 and further cooled in the cooler 5 as necessary. The condensed water generated by cooling may be returned to the quench tower 2, or this condensed water may be used as cooling water for the quench tower 2.

  The cooled reaction gas passes through the pipe 109, the filter 7, the pipe 110, the compressor 8, and further, if necessary, the cooler 9 and the pipe 111, and the hydrocarbon containing conjugated diene such as butadiene as a main component from the reaction gas. Although it is supplied to a recovery process (not shown) for recovering the components, at least a part of the gas may be extracted to control the top pressure of the quench tower, and when the recovery process is not operating, the entire amount is extracted. May be. The extracted gas may be stored, but industrially, it is usually incinerated with flare.

[Recovery process]
As a technique for recovering hydrocarbons from a cooled reaction gas, the reaction gas is brought into contact with a solvent such as a saturated hydrocarbon having 6 to 10 carbon atoms, an aromatic hydrocarbon having 6 to 8 carbon atoms, or an amide compound, and absorbed. The method of making it known is known.
In order to improve the absorption efficiency, it is desirable to compress the reaction gas with the compressor 8, usually 0.1 to 0.9 MPaG, preferably 0.2 to 0.6 MPaG, more preferably 0.25 to 0.35 MPaG. To be implemented. The greater the pressure, the better the absorption efficiency in the recovery process, and the smaller the advantage, the lower the construction cost.

  Depending on the type of the absorbing solvent, some of them may be hydrolyzed, and may be dehydrated by a known technique such as bringing the reaction gas into contact with a dehydrating agent such as molecular sieve, if necessary. In the case of a solvent that does not hydrolyze, it is not necessary to dehydrate the reaction gas, but if necessary, water may be separated by a method such as distillation purification or separation in the case of a water-insoluble solvent.

  The solvent that has absorbed the hydrocarbon gas is subjected to heat treatment to separate trace amounts of dissolved oxygen, nitrogen, etc., if necessary, and then distilled to separate the hydrocarbon containing conjugated diene as the main component and the solvent. . The hydrocarbon fraction containing conjugated diene as a main component obtained by distillation may be further purified as necessary, or a polymerization inhibitor may be added.

[Composite oxide catalyst]
Hereinafter, the oxidative dehydrogenation catalyst suitably used in the present invention will be described.
The oxidative dehydrogenation reaction composite oxide catalyst used in the present invention is preferably a composite oxide catalyst represented by the following general formula (1).
Mo _a Bi _b Q _c Ni _{d Re} X _f Y _g Z _h Si _i O _j (1)
(Wherein Q is cobalt (Co) and / or chromium (Cr), R is iron (Fe), aluminum (Al), gallium (Ga), zirconium (Zr), lead (Pb), niobium (Nb ), Tantalum (Ta), hafnium (Hf), and manganese (Mn), at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), zinc (Zn), cerium ( Ce) and at least one element selected from the group consisting of samarium (Sm), and Y is a group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and thallium (Tl). And at least one element selected from the group consisting of boron (B), phosphorus (P), arsenic (As), and tungsten (W). In addition, a to j represent atomic ratios of the respective elements, and when a = 12, b = 0.5 to 7, c = 0 to 10, d = 0 to 10 (provided that c + d = 1) 10), e = 0.05-3, f = 0-2, g = 0.04-2, h = 0-3, i = 5-48, and j is the oxidation of other elements It is a numerical value that satisfies the condition.)

  The composite oxide catalyst is a method for producing the composite oxide catalyst through a process in which the source compounds of the constituent elements constituting the composite oxide catalyst are integrated and heated in an aqueous system, and is selected from molybdenum compounds and R A pre-process for producing a catalyst precursor by heat-treating a raw material compound aqueous solution containing at least one selected from the group consisting of a compound, a nickel compound and a compound selected from Q and silica or a dried product obtained by drying the aqueous solution And the catalyst precursor, the molybdenum compound, and the bismuth compound are integrated with an aqueous solvent, and are dried and fired. Is preferably Co. If it is the complex oxide catalyst manufactured by such a method, conjugated dienes, such as a butadiene, can be manufactured with the high catalyst activity and a high yield.

Hereinafter, a method for producing a composite oxide catalyst suitable for the present invention will be described.
In this method for producing a composite oxide catalyst, the molybdenum used in the preceding step is molybdenum corresponding to a partial atomic ratio (a ₁ ) of the total atomic ratio (a) of molybdenum, The molybdenum used is preferably molybdenum corresponding to the remaining atomic ratio (a ₂ ) obtained by subtracting a ₁ from the total atomic ratio (a) of molybdenum. The a ₁ is preferably a value satisfying 1 <a ₁ / (c + d + e) <3. Furthermore, it is preferable that a ₂ is a value satisfying 0 <a ₂ / b <8.

  Source compounds of the above component elements include oxides, nitrates, carbonates, ammonium salts, hydroxides, carboxylates, ammonium carboxylates, ammonium halides, hydrogen acids, acetylacetonates, alkoxides of the component elements. The following are mentioned as the specific example.

Examples of Mo supply source compounds include ammonium paramolybdate, molybdenum trioxide, molybdic acid, ammonium phosphomolybdate, and phosphomolybdic acid.
Examples of Fe source compounds include ferric nitrate, ferric sulfate, ferric chloride, and ferric acetate.
Examples of the Co source compound include cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt carbonate, and cobalt acetate.
Examples of the Ni source compound include nickel nitrate, nickel sulfate, nickel chloride, nickel carbonate, nickel acetate and the like.
Examples of Si source compounds include silica, granular silica, colloidal silica, and fumed silica.

  Examples of Bi source compounds include bismuth chloride, bismuth nitrate, bismuth oxide, and bismuth subcarbonate. In addition, Bi component in which X component (one or more of Mg, Ca, Zn, Ce, and Sm) and Y component (one or more of Na, K, Rb, Cs, and Tl) are dissolved. It can also be supplied as a complex carbonate compound of the X component and the Y component.

For example, when Na is used as the Y component, a complex carbonate compound of Bi and Na can be obtained by dropping an aqueous solution of a water-soluble bismuth compound such as bismuth nitrate into an aqueous solution of sodium carbonate or sodium bicarbonate. The precipitate can be produced by washing with water and drying.
In addition, the complex carbonate compound of Bi and the X component is prepared by mixing an aqueous solution of a water-soluble compound such as bismuth nitrate and nitrate of the X component with an aqueous solution of ammonium carbonate or ammonium bicarbonate, etc. It can be produced by washing with water and drying.
When sodium carbonate or sodium bicarbonate is used instead of the above ammonium carbonate or ammonium bicarbonate, a complex carbonate compound with Bi, Na and X components can be produced.

Examples of source compounds of other component elements include the following.
Examples of the source compound for K include potassium nitrate, potassium sulfate, potassium chloride, potassium carbonate, and potassium acetate.
Examples of Rb source compounds include rubidium nitrate, rubidium sulfate, rubidium chloride, rubidium carbonate, and rubidium acetate.
Examples of the Cs supply source compound include cesium nitrate, cesium sulfate, cesium chloride, cesium carbonate, and cesium acetate.
Examples of Tl source compounds include thallium nitrate, thallium chloride, thallium carbonate, and thallium acetate.

Examples of the source compound for B include borax, ammonium borate, and boric acid.
Examples of P source compounds include ammonium phosphomolybdate, ammonium phosphate, phosphoric acid, phosphorus pentoxide, and the like.
Examples of the source compound for As include dialsenooctammonium molybdate, ammonium dialseno18 tungstate, and the like.
Examples of W source compounds include ammonium paratungstate, tungsten trioxide, tungstic acid, and phosphotungstic acid.

Examples of the Mg source compound include magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium carbonate, and magnesium acetate.
Examples of the source compound for Ca include calcium nitrate, calcium sulfate, calcium chloride, calcium carbonate, and calcium acetate.
Examples of the Zn source compound include zinc nitrate, zinc sulfate, zinc chloride, zinc carbonate, and zinc acetate.
Examples of the Ce source compound include cerium nitrate, cerium sulfate, cerium chloride, cerium carbonate, and cerium acetate.
Examples of Sm source compounds include samarium nitrate, samarium sulfate, samarium chloride, samarium carbonate, and samarium acetate.
Examples of source compounds such as Cr, Al, Ga, Zr, Pb, Nb, Ta, Hf, and Mn include corresponding nitrates, chlorides, carbonates, acetates, and the like.

The raw material compound aqueous solution used in the previous step is an aqueous slurry containing at least molybdenum (corresponding to a ₁ in the total atomic ratio a), iron (R), nickel or cobalt (Q), and silica as a catalyst component, and water slurry. Or a cake.

  The raw material compound aqueous solution is prepared by integrating the source compound in an aqueous system. Here, the integration of each component element source compound in an aqueous system means that the aqueous solution or aqueous dispersion of each component element source compound is mixed or / and aged in stages. Say. (B) a method of mixing the above-mentioned source compounds in a lump, (b) a method of mixing the above-mentioned source compounds in a lump and aging, and (c) a method of mixing each of the above-mentioned source compounds. Supply of each component element is a method of stepwise mixing, (d) a method of repeatedly mixing and aging the above-mentioned source compounds stepwise, and a method of combining (b) to (d). It is included in the concept of integration of the source compound in an aqueous system. Here, aging refers to the processing of industrial raw materials or semi-finished products under specific conditions such as constant temperature for a certain period of time to obtain the required physical and chemical properties, increase or advance the prescribed reaction, etc. The fixed time is usually in the range of 10 minutes to 24 hours, and the fixed temperature is usually in the range of room temperature to the boiling point of the aqueous solution or aqueous dispersion.

  As a specific method of the above integration, for example, a solution obtained by mixing an acidic salt selected from catalyst components, and a solution obtained by mixing a basic salt selected from catalyst components, Specific examples include a method of adding a mixture of an iron compound and a nickel compound and / or a cobalt compound to an aqueous solution of a molybdenum compound while heating, and mixing silica.

  The raw material compound aqueous solution (catalyst precursor slurry) containing silica thus obtained is heated to 60 to 90 ° C. and aged.

  The aging means that the catalyst precursor slurry is stirred at a predetermined temperature for a predetermined time. This aging increases the viscosity of the slurry, reduces the sedimentation of the solid components in the slurry, and is particularly effective in suppressing the heterogeneity of components in the subsequent drying process. The catalytic activity such as the raw material conversion rate and selectivity of the product catalyst becomes better.

  60-90 degreeC is preferable and the temperature in the said ripening has more preferable 70-85 degreeC. When the aging temperature is less than 60 ° C., the aging effect is not sufficient, and good activity may not be obtained. On the other hand, when it exceeds 90 ° C., the water is often evaporated during the aging time, which is disadvantageous for industrial implementation. Further, if the temperature exceeds 100 ° C., a pressure vessel is required for the dissolution tank, and handling becomes complicated, which is extremely disadvantageous in terms of economy and operability.

  The aging time is preferably 2 to 12 hours, and preferably 3 to 8 hours. If the aging time is less than 2 hours, the activity and selectivity of the catalyst may not be sufficiently developed. On the other hand, the aging effect does not increase even if it exceeds 12 hours, which is disadvantageous for industrial implementation.

  Any method can be adopted as the stirring method, and examples thereof include a method using a stirrer having a stirring blade and a method using external circulation using a pump.

  The aged slurry is subjected to heat treatment as it is or after drying. There is no particular limitation on the drying method in the case of drying and the state of the dried product to be obtained. For example, a powdery dried product may be obtained using a normal spray dryer, slurry dryer, drum dryer, etc. Alternatively, a block-like or flake-like dried product may be obtained using a normal box-type dryer or a tunnel-type firing furnace.

  The raw material salt aqueous solution or granules or cakes obtained by drying the aqueous salt solution are heat-treated in air at a temperature of 200 to 400 ° C., preferably 250 to 350 ° C. for a short time. There are no particular limitations on the type and method of the furnace at that time, and for example, it may be heated with a dry matter fixed using a normal box-type furnace, tunnel-type furnace, etc., or a rotary kiln. It is possible to heat the dried product while flowing it.

The ignition loss of the catalyst precursor obtained after the heat treatment is preferably 0.5 to 5% by mass, and more preferably 1 to 3% by mass. By setting the ignition loss within this range, a catalyst having a high raw material conversion rate and high selectivity can be obtained. Note that the loss on ignition is a value given by the following equation as described above.
Burning loss (%) = [(W ₀ −W ₁ ) / W ₀ ] × 100
W ₀ : Mass (g) of the catalyst precursor after drying at 150 ° C. for 3 hours to remove adhering moisture
W ₁ : after further heat-treating the catalyst precursor excluding adhering moisture at 500 ° C. for 2 hours
Mass (g)

In a later step, the integration of the above procatalyst precursor and the molybdenum compound obtained in step (remaining a ₂ corresponds to minus a ₁ equivalent of the total atomic ratio a) and bismuth compounds, carried out in an aqueous solvent. At this time, it is preferable to add ammonia water. The addition of the X, Y, and Z components is also preferably performed in the subsequent step. At this time, since the bismuth source compound is bismuth which is hardly soluble or insoluble in water, the compound is preferably used in the form of a powder. These compounds as the catalyst production raw material may be particles larger than the powder, but are preferably smaller particles in view of the heating step in which thermal diffusion should be performed. Therefore, if these compounds as raw materials are not such particles, they should be pulverized before the heating step.

  Next, the obtained slurry is sufficiently stirred and then dried. The dried product thus obtained is shaped into an arbitrary shape by a method such as extrusion molding, tableting molding or support molding. Next, this is preferably subjected to a final heat treatment for about 1 to 16 hours under a temperature condition of 450 to 650 ° C. As described above, a composite oxide catalyst that is highly active and gives the target oxidative dehydrogenation reaction product in high yield can be obtained.

The composite oxide catalyst thus obtained is usually packed in a reactor together with an inert ball for adjusting the reaction activity to form a fixed bed.
As the inert ball, a ceramic spherical body such as alumina or zirconia is used. The inert ball is usually the same size as the composite oxide catalyst, and its particle size is about 2 to 10 mm.

Hereinafter, the present invention will be described more specifically with reference to examples.
In the following, “part” means “part by mass”.

[Reference Example 1: Preparation of composite oxide catalyst]
54 parts of ammonium paramolybdate are heated and dissolved in 250 parts of pure water. Next, 7.18 parts of ferric nitrate, 31.8 parts of cobalt nitrate, and 31.8 parts of nickel nitrate are heated and dissolved in 60 parts of pure water. These solutions are gradually mixed with good stirring. Next, 64 parts of silica is added and stirred thoroughly. This slurry is heated to 75 ° C. and aged for 5 hours. Thereafter, the slurry is heated and dried, and then subjected to heat treatment at 300 ° C. for 1 hour in an air atmosphere. The obtained granular solid of the catalyst precursor is pulverized, and 40.1 parts of ammonium paramolybdate is dispersed in a solution obtained by adding 9 parts of ammonia water to 150 parts of pure water. Next, 0.85 part of borax and 0.36 part of potassium nitrate are dissolved in 40 parts of pure water under heating and added to the slurry. Next, 58.1 parts of bismuth subcarbonate in which Na is dissolved in 0.45% is added and mixed by stirring. After the slurry was dried by heating, the obtained granular solid was compressed into tablets of 5 mm in diameter and 4 mm in height using a small molding machine, and then calcined at 500 ° C. for 4 hours to obtain a composite oxide catalyst. Got.

[Example 1]
1,3-butadiene was produced by the method shown in FIG.
The reaction tube in the reactor 1 provided with 113 reaction tubes having an inner diameter of 27 mm and a length of 3500 mm was mixed with 622 ml of the composite oxide catalyst produced in Production Example 1 and an inert ball (manufactured by Tipton Corp.) per reaction tube. 384 ml was charged.
And BBSS discharged from butadiene extraction separation process from C ₄ fraction by-produced in naphtha cracking, by supplying air and nitrogen and water vapor at a flow rate below were mixed as a raw material gas, without pre-heater (shown ) And then supplied to the reactor 1 (pipe 100). Around the reaction tube in the reactor 1, a heating medium (heating medium line not shown) of about 331 ° C. was flowed to adjust the temperature inside the reaction tube to about 344 to 390 ° C.

The flow rate of the raw material gas was as follows, and the total was 237.8 parts by mass / hr in terms of mass.
BBSS: 16.5 capacity parts / hr
Air: 88.8 parts by volume / hr
Nitrogen: 54.3 parts by volume / hr
Water vapor: 17.6 parts by volume / hr

  The reaction gas from the reactor 1 was supplied to the bottom of the quench tower 2 (pipe 101). The quench tower 2 is a tray tower having a sheave-type tray having 30 actual stages, and pure water is supplied to the top of the tower at a rate of 200 parts by mass / hr (pipe 102), and water that falls to the bottom of the tower through a downcomer. Is extracted from the bottom of the tower (pipe 103), and the liquid level gauge at the bottom of the tower (the position of 200mm above the curved portion at the bottom of the kettle is 0% liquid level, and the position of 500mm below the reaction gas inlet nozzle is the liquid level 100%. The liquid level gauge was set to 30%, and a part of water was fed to a waste water tank (not shown) (pipe 106). Also, a part of the water is circulated to the bottom of the quench tower as a pump minimum flow (not shown), the remaining water is cooled to 50 ° C. by the heat exchanger 4, and a part of the water is The water was supplied to the 16th tray (pipe 104) and contacted with the reaction gas, and the remaining water was sprayed (pipe 105) on the bottom of the tray to contact the reaction gas. The tray installation portion of the quench tower is an area of 1 / 1.4 of the total height of the quench tower, and the spray area at the bottom of the tray is an area of 1 / 7.2 of the total height of the quench tower.

  Each flow rate was slightly changed due to manual adjustment of the valve, but the average of the 16th stage feed was about 955 parts by mass / hr and the spray to the bottom of the column was about 507 parts by mass / hr. . The total amount of cooling water supplied from the pipes 102 and 104 to the sheave tray was about 1155 parts by mass / hr on average.

  The ratio of the flow rate of the reaction gas (mass / hr) supplied to the bottom of the quench tower 2 and the water (mass / hr) supplied to the sieve tray is 0.21 (= 237.8 / 1155). there were. The ratio of water sprayed to the bottom of the cooling water (including circulating water) supplied to the quench tower 2 was 31% (= {507 / (507 + 1155)} × 100).

  The reaction gas supplied to the bottom of the quench tower was cooled in contact with the water supplied from the top and the 16th stage of the tower and the water sprayed on the bottom of the tower, and then extracted from the top (pipe 107). The temperature of the water supplied to the top of the tower was 9 to 15 ° C., although fluctuations were observed due to the temperature. The liquid temperature at the bottom of the quench tower was about 67 ° C, and the top temperature was 10-23 ° C.

  The reaction gas extracted from the top of the column was further cooled by a heat exchanger 5 using cold water at 5 ° C. as a cooling medium to condense water contained in the reaction gas. The water condensed here was returned to the bottom of the quench tower (the piping for returning the condensed water to the bottom of the quench tower was not shown). A part of the reaction gas after condensing moisture was discharged into the flare through a pressure control valve that controls the pressure at the top of the quench tower to be maintained at 25 kPaG and burned.

  The remaining gas was supplied to the compressor 8 after passing through the filter 7. The gas flow rate was controlled by a flow rate control valve installed in the AC of the compressor 8 (not shown). The gas flow rate was about 88 parts by volume / hr until about 75 hours, and 109 parts by volume / hr thereafter. The filter 7 was used with 12 pole cell filters (rated filtration accuracy 0.5 μm) manufactured by Nippon Pol Co., Ltd. mounted in parallel on the filter housing for the purpose of recovering solids contained in the reaction gas. A pressure gauge was installed on the secondary side of the filter and the pressure on the secondary side of the filter was recorded. Since the pressure on the secondary side of the filter decreases when the filter is clogged with solids and the pressure loss increases, this pressure decrease was used as a measure of the amount of solids contained in the reaction gas.

The pressure on the secondary side of the filter 7 when the gas began to flow through the filter 7 was 21 kPaG, but after 371 hours it was 16.1 kPaG. When the rate of pressure decrease after increasing the gas flow rate to 109 parts by volume / hour was first-order approximated, it was -0.0068 kPa / hr. FIG. 2 shows changes in gas flow rate and pressure at this time.
Further, the amount of solid matter scattered from the quench tower during the operation period was determined from the mass difference between the filter before and after the operation and the result of collecting the solid matter adhering to the housing and measuring the mass. By dividing this by the amount of gas passed through the filter during the operation period, the solids concentration in the gas was determined and found to be less than 0.01 g / Nm ³ .
The results are shown in Table 1.

[Example 2]
The same operation as in Example 1 was performed except that the operating conditions were as follows.
The flow rate of the raw material gas is as follows, and the total was 180 parts by mass / hr when converted to mass.
BBSS: 13.2 capacity parts / hr
Air: 62.0 parts by volume / hr
Nitrogen: 30.9 parts by volume / hr
Water vapor: 35.3 parts by volume / hr
-The heat medium temperature of the reactor 1 was 328 degreeC.
-The gas flow rate which flowed to the filter 7 was 85 volume part / hr. However, the operation was temporarily stopped at 285 hours, and the gas flow rate was set to about 22 parts by volume / hr only for about 20 hours after the resumption of operation (the elapsed time does not include the stopped time).
The amount of cooling water supplied to the 16th tray from the top of the quench tower was about 941 parts by mass / hr on average, and the amount of water sprayed to the bottom of the quench tower was about 508 parts by mass on average.

The total amount of cooling water supplied from the pipes 102 and 104 to the sheave tray was about 1141 parts by mass / hr on average.
The flow rate ratio between the reaction gas (mass / hr) supplied to the bottom of the quench tower and the cooling water (mass / hr) supplied to the sieve tray was 0.16.
Of the cooling water (including circulating water) supplied to the quench tower, the ratio of water sprayed to the tower bottom was 31%.

FIG. 3 shows changes in the gas flow rate passed through the filter 7 and the secondary pressure of the filter 7. Except when the gas flow rate was reduced, the pressure decrease rate was -0.0019 kPa / hr in a first order approximation.
When the filter was taken out after the gas flow was stopped, almost no solid matter adhered to the filter. Since it was slightly wet, the weight was measured after drying and it was lighter than before the operation, and the amount of attached solid matter could not be determined. It is considered that the weight loss due to drying was larger than the amount of solids deposited because the new filter slightly absorbed moisture.
The results are shown in Table 1.

[Comparative Example 1]
The reaction was performed in the same manner as in Example 1 except that the reaction conditions were as follows.
-The flow rate of the raw material gas was as follows, and the total mass was 224.7 parts by mass / hr.
BBSS: 16.5 capacity parts / hr
Air: 75.0 parts by volume / hr
Nitrogen: 41.1 parts by volume / hr
Water vapor: 44.1 parts by volume / hr
-The heat medium temperature of the reactor 1 was 344 degreeC.
-The gas flow rate which flowed to the filter was 85 volume parts / hr.
The amount of cooling water supplied to the 16th tray from the top of the quench tower was about 333 parts by mass / hr on average, and the amount of water sprayed to the bottom of the quench tower was about 996 parts by mass / hr on average.

The total amount of cooling water supplied from the pipes 102 and 104 to the sheave tray was 533 parts by mass / hr on average.
The flow rate ratio between the reaction gas (mass / hr) supplied to the bottom of the quench tower and the cooling water (mass / hr) supplied to the sieve tray was 0.42.
Of the cooling water (including circulating water) supplied to the quench tower, the ratio of water sprayed to the tower bottom was 65%.

In Comparative Example 1, the total amount of cooling water from the pipes 102, 104, and 105 used for cooling the reaction gas is about 1529 parts by mass / hr on average, which is not significantly different from Examples 1 and 2. The temperature of the water supplied to the top of the tower was 14 to 16 ° C., although fluctuation was observed due to the temperature. The liquid temperature at the bottom of the quench tower was about 75 ° C, and the top temperature was 17-25 ° C. Since the raw material steam is increased, the column bottom temperature is higher than that in Example 1, but the column top is sufficiently cooled.
FIG. 4 shows changes in the gas flow rate passed through the filter 7 and the secondary pressure of the filter 7. The secondary pressure of the filter 7 was 21.25 kPaG before operation, but rapidly decreased to 5.65 kPa · G after 61 hours. The rate of pressure decrease was −0.256 kPa / h in a first order approximation. The mass of the solid adhered to the filter and the housing was measured, and the solid concentration in the reaction gas was determined to be 0.023 g / Nm ³ .
The results are shown in Table 1.

  In addition, when the solid substance trapped by the filter was observed with SEM (JEOL JSM-6340F type FE-SEM), it was found that the particle diameter was about 0.5 μm (FIG. 5). When this solid was analyzed by IR, it was found that the main components were terephthalic acid and isophthalic acid.

DESCRIPTION OF SYMBOLS 1 Reactor 2 Quench tower 3 Pump 4 Cooler 5 Cooler 6 Drain pot 7 Filter 8 Compressor 9 Cooler 10 Drain pot

Claims (6)

A reaction gas containing a corresponding conjugated diene is obtained by performing an oxidative dehydrogenation reaction between a raw material gas containing a monoolefin having 4 or more carbon atoms and a molecular oxygen-containing gas in the presence of a catalyst. In the method for producing a conjugated diene in which gas is introduced into a cooling tower and brought into contact with cooling water for cooling,
A shelf is formed in the cooling tower,
A method for producing a conjugated diene, wherein a mass ratio between a flow rate of the reaction gas introduced into the cooling tower and a flow rate of cooling water supplied to the shelf of the cooling tower is 0.3 or less. .   The method for producing a conjugated diene according to claim 1, wherein the cooling water is supplied from two or more supply points different in the height direction of the cooling tower and is brought into contact with the reaction gas.   The ratio of the flow rate of the cooling water supplied to other than the shelf portion of the cooling tower with respect to the total flow rate of the cooling water supplied to the cooling tower is in the range of 0 to 35%. The manufacturing method of conjugated diene of description.   The method for producing a conjugated diene according to any one of claims 1 to 3, wherein the tray in the cooling tower in the cooling tower includes a sheave-type tray. 5. The method for producing a conjugated diene according to claim 1, wherein the catalyst is a composite oxide catalyst represented by the following general formula (1).
Mo _a Bi _b Q _c Ni _{d Re} X _f Y _g Z _h Si _i O _j (1)
(Wherein Q is cobalt (Co) and / or chromium (Cr), R is iron (Fe), aluminum (Al), gallium (Ga), zirconium (Zr), lead (Pb), niobium (Nb ), Tantalum (Ta), hafnium (Hf), and manganese (Mn), at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), zinc (Zn), cerium ( Ce) and at least one element selected from the group consisting of samarium (Sm), and Y is a group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and thallium (Tl). And at least one element selected from the group consisting of boron (B), phosphorus (P), arsenic (As), and tungsten (W). In addition, a to j represent atomic ratios of the respective elements, and when a = 12, b = 0.5 to 7, c = 0 to 10, d = 0 to 10 (provided that c + d = 1) 10), e = 0.05-3, f = 0-2, g = 0.04-2, h = 0-3, i = 5-48, and j is the oxidation of other elements It is a numerical value that satisfies the condition.)   The raw material gas is produced by dehydrogenation or oxidative dehydrogenation of gas containing 1-butene, cis-2-butene, trans-2-butene or a mixture thereof obtained by dimerization of ethylene, or a mixture thereof. 6. The conjugate according to any one of claims 1 to 5, wherein the butene fraction or the heavy oil fraction is a gas containing a large amount of hydrocarbons having 4 carbon atoms obtained by fluid catalytic cracking. Diene production method.

Images