JP4401630B2 - Gas compression method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to gas compression. Specifically, alkane is present in the presence of ammonia.UnderVapor-phase catalytic oxidation reaction and unsaturated nitrile as the target productLeIn the production method, the target product is cooled and / or absorbed by water from the reaction gas.To payThe present invention relates to a method for compressing the remaining recovered gas stream.
[0002]
[Prior art]
Unsaturated nitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and unsaturated aldehydes such as acrolein and methacrolein are important raw materials for synthesis of fibers, synthetic resins, synthetic rubbers, etc. It is widely used and manufactured industrially. Conventionally, these unsaturated nitriles, unsaturated carboxylic acids or unsaturated aldehydes have been generally produced by a gas phase catalytic oxidation reaction of olefins such as propylene and isobutylene as raw materials.
On the other hand, in recent years, instead of olefins, a method for obtaining a target product directly by using a cheap alkane as a raw material and performing a gas phase catalytic oxidation reaction in the presence or absence of ammonia using a catalyst has been developed and studied. Collecting.
[0003]
For example, regarding a catalyst for obtaining acrylonitrile from propane, a Mo—Bi—P catalyst (Japanese Patent Laid-Open No. 48-16887), a Mo—Cr—Te catalyst (US Pat. No. 5,171,876), a Mo—Cr—Bi catalyst (special Kaihei 7-215925), V-Sb catalysts (Japanese Patent Publication No. 50-230616, JP-A-1-268668), Mo-V-Te catalysts (Japanese Patent No. 12608768, JP-A-10-81660), Mo- V-Sb catalysts (Japanese Patent Laid-Open No. 9-157241) and the like have been reported.
At the same time, many of these catalysts have been reported to be useful in the production of methacrylonitrile from isobutane.
Regarding catalysts for obtaining acrylic acid from propane, there are Mo-V-Te catalysts (JP-A-6-279351), Mo-V-Sb-Nb catalysts (JP-A-11-285636), etc. As catalysts for obtaining corresponding unsaturated carboxylic acids from 8 alkanes, Mo-V-Sb-Nb-based catalysts (Japanese Patent Laid-Open No. 10-45664), Mo-V-Sb-Te-based catalysts (Japanese Patent Laid-Open No. 10-36311). ) Has been reported.
[0004]
With respect to catalysts for obtaining methacrylic acid from isobutane, Mo-P-V-Cu-based catalysts (Japanese Patent Laid-Open Nos. 2-42032 and 3-20237) have been reported. However, none of these catalyst-based methods has a sufficient selectivity for the desired product, and is still not satisfactory as an industrial method.
Therefore, by utilizing the fact that when the alkane conversion rate is low, a higher selectivity can be obtained than when the alkane conversion rate is high, by suppressing the supplied alkane conversion rate to a predetermined value or less and increasing the alkane concentration, It has been proposed that unreacted alkane is recovered and recycled to the reactor while achieving both high selectivity and catalyst productivity.
[0005]
For example, US Pat. No. 4,352,755 proposes recovery by liquefying unreacted alkane, but this method is accompanied by a large amount of non-condensable gas components such as nitrogen. Alkane loss increases. At this time, if it is attempted to reduce the alkane loss to an industrially practicable range, the burden of the liquefaction cooling operation of the unreacted alkane becomes extremely large and becomes impractical. Furthermore, this method has the disadvantage that a large amount of energy is required to heat the recovered alkane to the reaction temperature.
JP-B-6-37451 and JP-A-10-81660 show a selective separator as an apparatus for separating and recovering unreacted alkane, specifically, a pressure swing adsorption apparatus (PSA). .
[0006]
However, when PSA is applied, the adsorption capacity of the adsorbent alkane itself is not large, and one of the components such as carbon dioxide, carbon monoxide, nitrogen, and moisture contained in the gas stream other than the unreacted alkane. Therefore, a large amount of adsorbent is required, and handling on a large number of adsorbing towers is required for implementation on an industrial scale, resulting in complicated operations and economical problems. In addition, the operation is performed by adsorbing the target component alkane by pressurization and then desorbing by reducing the pressure. Since the separation efficiency is poor, the desorption gas is added to the operation to decrease the pressure during desorption. In order to increase the efficiency by reducing the partial pressure of the target component such as alkane. In this case, if an inert gas is used as the gas, even a trace amount of inert gas is brought into the reactor and accumulates in the system.
[0007]
For this reason, there is a way to obtain gas containing flammables such as alkanes exceeding the upper limit of the explosion range by desorbing using part of the air used in the reactor instead of inert gas, but in this case, inside the adsorption tower As the air passes through the adsorbent layer and desorbs, the concentration of combustibles such as alkanes in the air increases and passes between the lower and upper limits of the explosion range of combustibles. There is a difficult problem. Further, when the desorption proceeds and the amount of combustible material such as alkane that is desorbed decreases, the composition of the adsorbent layer outlet gas falls below the upper limit of the explosion range of the combustible material such as alkane.
In addition, in the method using an adsorbent, when a high-boiling substance is brought into the system and adheres to the adsorbent surface or between adsorbent particles, or when the adsorbent deteriorates, it may be difficult to regenerate and need to be replaced. There is also a problem that operation is complicated and difficult to carry out, particularly in industrial implementation.
[0008]
For example, in US Pat. No. 3,914,277, a gas containing unreacted alkane is compressed with a compressor and then absorbed with paraffin oil having 10 to 17 carbon atoms such as kerosene, heavy naphtha, light diesel oil, etc. It is proposed that the absorbed liquid is stripped with nitrogen or a mixed gas of nitrogen and oxygen and the recovered mixture of alkane and stripping gas is recycled to the reactor.
However, when the present inventors carried out this method, it was found that the compressor frequently vibrates and can be operated for only one month.
[0009]
[Problems to be solved by the invention]
The object of the present invention is to subject an alkane having 3 to 4 carbon atoms in the presence or absence of a catalyst to a gas phase catalytic oxidation reaction in the presence or absence of ammonia to produce an unsaturated nitrile or unsaturated acid anhydride as a target product. Gas compressor when absorbing unreacted alkane using an absorbing solvent while producing high selectivity and catalyst productivity at the same time in the production of product or unsaturated carboxylic acid and / or unsaturated aldehyde It is an object of the present invention to provide a method for separating and recovering a mixture mainly composed of unreacted alkane, which can be stably operated for a long period of time without causing vibrations, and is superior in industrial implementation.
[0010]
[Means for Solving the Problems]
  The inventors have cooled the target product from the reaction gas and / or absorbed water.To payAs a method of separating and recovering the mixture mainly composed of unreacted alkane from the remaining gas stream recovered, when compressing the remaining gas stream recovering the target product,Sodium hydroxide, carbonate or bicarbonateIs present in the inlet gas stream of the compressor, and then the gas stream is brought into contact with an organic solvent insoluble in water to absorb the vapor phase component mainly composed of unreacted alkane. It was found that the problem can be solved, and the present invention has been achieved. That is,
[0011]
  The present invention
1) In the presence of a catalyst,propaneThe presence of ammoniaUnderGas phase catalytic oxidation reaction to produce unsaturated nitrile as productLeCompressing the remaining gas stream recovered from the reaction gas, such as by cooling and / or water absorption, in the process of production;Sodium hydroxide, carbonate or bicarbonateIn a compressor inlet gas stream.
[0012]
2) TheSodium hydroxide, carbonate or bicarbonateIs added to the gas stream in an aqueous solution.
3) TheSodium hydroxide, carbonate or bicarbonateThe method according to 2), wherein the amount of addition is 0.01 to 10 wt% with respect to the gas flow.
4) TheSodium hydroxide, carbonate or bicarbonateThe method according to 2), wherein the amount of added is 0.05 to 5 wt% with respect to the gas flow.
5)TheThe method according to 1) to 4), wherein the unsaturated nitrile is acrylonitrile.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
  The key point of the present invention is that the remaining gas stream from which the target product is recovered from the reaction gas contains a trace amount of the target product, ie, acrylonitrile.LeIt remains without being collected. Various by-products such as various unsaturated nitriles or hydrocyanic acid, or various unsaturated acids and unsaturated aldehydes, and high-boiling substances are also included. Unsaturated nitriles, unsaturated acids, unsaturated aldehydes and hydrocyanic acid, which are the target substances and by-products, are polymerized in the process and inside the compressor until the raw material alkane reacts and becomes a reaction gas. It becomes a polymer and accumulates on the inner surface of the compressor and the moving blades and stationary blades together with high-boiling substances by-produced, and if the amount of adhesion increases, the compressor will vibrate and the compressor operation must be stopped. Disappear. The undesirable phenomenon that such a compressor vibrates is when compressing the remaining gas stream from which the target product has been recovered from the reaction gas,Sodium hydroxide, carbonate or bicarbonateCan be prevented by being present in the compressor inlet gas streamthingThe main point is to find.
[0015]
  Polymers and high-boiling substances adhere to and accumulate on the inner surface of compressors, rotor blades and stationary blades.Sodium hydroxide, carbonate or bicarbonateThe mechanism of action that prevents is unknown, but probablySodium hydroxide, carbonate or bicarbonateHowever, it will prevent the polymer and high-boiling substances adhering to the inner surface of the compressor, the moving blades and the stationary blades from losing moisture, drying and sticking, and quickly washing away.
[0016]
  The present invention will be described in detail below. In the presence of a catalyst,propaneThe ammonia presentUnderVapor-phase catalytic oxidation reaction and unsaturated nitrile as the target productLeIn the production process, the target product is cooled and / or absorbed by water from the reaction gas.To payWhen compressing the remaining recovered gas stream,Sodium hydroxide, carbonate or bicarbonateIs present in the inlet gas stream of the compressor.
[0017]
  BookThe object product of the invention is an unsaturated nitriteLeIn some cases, the unsaturated carboxylic acid and the unsaturated aldehyde may simultaneously become the target product.EyeThe product is at least one selected from acrylonitrile, acrylic acid, and acrolein.Becauseis there. The reaction gas of the present invention is a gas obtained by oxidizing or ammoxidizing the gas supplied to the reactor. The target product, unreacted alkane, by-product alkene, nitrogen, oxygen, carbon monoxide, carbon dioxide , A mixture of moisture and the like, and their ratios differ depending on reaction conditions and the like.
[0018]
  The target product is cooled and / or absorbed from the reaction gas of the present invention.To payThe remaining gas stream recovered is the cooling and / or water absorption of the target product from the gas supplied to the reactor.To payThe remaining gas flow recovered from the process includes unreacted alkanes, by-produced alkenes, nitrogen, oxygen, carbon monoxide, carbon dioxide, moisture, trace amounts of target products, by-products, and high-boiling substances. These are mixtures, and their ratios differ depending on the reaction conditions and the like.
[0019]
  As an alkaline substanceAndNaturiuOfHydroxides, carbonates or bicarbonates can be used.SolidIn the case of a body, it can be used as an aqueous solution, and even when it is liquid, it can be used as an aqueous solution.
[0020]
  Sodium hydroxide, carbonate or bicarbonateIs added in an amount of 0.01 to 10 wt%, preferably 0.05 to 5 wt% with respect to the gas flow.Sodium hydroxide, carbonate or bicarbonateCan be added using a nozzle in the immediate vicinity of the compressor inlet for compressing the gas. Moreover, you may inject | pour directly into the casing of a compressor.
[0021]
The compressor that compresses the gas may be a centrifugal, axial flow, or rotary compressor. Moreover, in the case of a multistage compressor, it is good to add every stage.
As the organic solvent that absorbs the compressed gas stream, hydrocarbons, halogenated hydrocarbons, ketones, ethers and the like can be used, but those insoluble in water are suitable. When water is dissolved, there is a high possibility of causing an azeotrope to flow out when stripping in the stripping tower, and the absorption efficiency in the absorption tower decreases due to the dissolved water. Therefore, it is not a preferable solvent. Further, ketones, ethers and the like tend to generate peroxides, which cause radical polymerization, and are not preferable solvents when a reaction gas contains a substance that is easily polymerized. Preferred are hydrocarbons, among which aliphatic hydrocarbons having 5 to 20 carbon atoms, alicyclic hydrocarbons or aromatic hydrocarbons are more preferred. A hydrocarbon-based solvent having 4 or less carbon atoms absorbs alkane, and when the alkane is recovered by a stripping tower or the like, the amount of the organic solvent accompanying the recovered alkane is large and the operation is not easy.
[0022]
In addition, when recycling alkane or the like to the reactor, an organic solvent is entrained, which may adversely affect the reaction. On the other hand, when the number of carbons exceeds 20, the operating temperature of a conventional absorption tower becomes high viscosity and the absorption efficiency is greatly deteriorated, so that it cannot be used. Suitable solvents include, for example, hexane, heptane, octane, isooctane, decane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, eicosane, cyclohexane, toluene, xylene, ethylbenzene, butylbenzene, cymene, durene, methylnaphthalene. , Ethylnaphthalene, dimethylnaphthalene, diphenyl and the like. These can be used alone or in the form of a mixture. Moreover, when the high boiling point component accumulates in the solvent, the solvent can be extracted continuously or intermittently and purified by distillation operation.
[0023]
The absorption system in which the compressed gas stream is brought into contact with the organic solvent can be any of a known packed tower, perforated plate tower, bubble bell tower, spray tower, and the like. Although the absorption operating pressure and temperature depend on the organic solvent used, the higher the operating pressure, the smaller the amount of organic solvent required.^Five-10x10^FivePa. The lower the operating temperature, the smaller the required amount of organic solvent. However, the organic solvent is solidified, and the viscosity is increased to reduce the absorption efficiency.
[0024]
A method for obtaining a mixture mainly composed of unreacted alkane from the obtained absorbing solution can be obtained by a known method. For example, it can be obtained by a method of heating and distilling the absorbing solution, a method of stripping the absorbing solution with nitrogen, a gas mainly composed of nitrogen and oxygen, or a steam, and the like. A bell tower is used. The lower the operating pressure, the easier it is to obtain unreacted alkane, but generally 0.05 × 10^Five~ 2x10^FivePa. The higher the operating temperature, the easier it is to obtain unreacted alkane, but generally it may be the same as the absorption operating temperature.
[0025]
The mixture mainly composed of unreacted alkane refers to unreacted alkane and by-product alkene in the remaining gas stream obtained by recovering the target product from the reaction gas, and the alkene in the case where the alkane is propane. Is propylene.
The method of recycling the mixture mainly composed of unreacted alkane to the reactor is to recycle the mixture containing the separated alkane and alkene, if necessary, in a gaseous state after cooling to remove the contained water. Any method such as recycling to a reactor together with nitrogen or a stripping gas mainly composed of nitrogen and oxygen, or liquefaction and mixing with raw material alkane can be used.
[0026]
  In the present invention, an alkane is present in the presence of a catalyst.Gas phase catalytic ammoxidationHowever, it is important to maintain the reaction conditions within a predetermined range. The content of alkane in the raw material gas supplied to the reactor is 3 to 90 vol%, preferably 10 to 50 vol%, but it is preferable to increase the alkane concentration in the reaction gas as much as possible from the viewpoint of productivity.
  In the method of the present invention, the operation is performed under conditions where the alkane conversion is 70% or less, preferably 60% or less. If the conversion is higher than this range, the selectivity of the target product is lowered, which is not preferable. In order to keep the alkane conversion low, the reaction conditions such as reduction of the catalyst amount, reaction temperature, contact time between the reactor supply gas and the catalyst, pressure, and reaction gas composition are controlled.
[0027]
  PropNIn the case of gas phase catalytic ammoxidation, it can be carried out under the following conditions.
  The molar ratio of oxygen supplied to the reaction to propane or isobutane is 0.1 to 6, preferably 0.5 to 4.
  The reaction temperature is 300 ° C to 500 ° C, preferably 350 ° C to 470 ° C.
  Reaction pressure is 0.5 × 10⁵~ 5x10⁵Pa, preferably 1 × 10⁵~ 3x10⁵Pa.
  The contact time is 0.1 to 10 (sec · kg / l), preferably 0.5 to 5 (sec · kg / l). In the present invention, the contact time is determined by the following equation.
  Contact time (sec · kg / l) = (W / F) × 273 / (273 + T)
here
  W = amount of packed catalyst (kg)
  F = standard state (0 ° C., 1.13 × 10⁵Raw material mixed gas flow rate at Pa) (Nl / sec)
  T = reaction temperature (° C.)
It is.
[0029]
In the present invention, as described above, the alkane conversion is controlled at 70% or less. Therefore, in order to increase the production amount of nitriles in a single stream, the alkane in the reaction gas supplied to the reactor is increased. It is advantageous to increase the concentration. In addition, since the unreacted alkane and alkene are contained in the gas after separating the target product produced at high selectivity, it is selected and separated by the method of the present invention, and supplied to the reactor. The overall yield of the desired product can be increased.
As the catalyst of the present invention, known oxidation reaction catalysts and ammoxidation reaction catalysts are used. The catalyst of the present invention is preferably a silica-supported catalyst. When the catalyst of the present invention is a silica-supported catalyst, it has high mechanical strength, and is therefore suitable for oxidation reactions and ammoxidation reactions using a fluidized bed reactor. The content of the silica support is based on the total weight of the silica-supported oxide catalyst composed of the oxide of the catalyst constituent element and the silica support.₂It is preferably 20 to 60% by weight in terms of conversion, more preferably 30 to 50% by weight.
[0030]
  In the presence of such an oxide catalyst,CarePhase contact ammoxidation reactionRuSaturated nitrile is produced.
  PropAndThe ammonia feedstock does not necessarily have to be highly pure, and industrial grade feedstock can be used.
  Air, oxygen-enriched air, or pure oxygen can be used as the supply oxygen source.
[0031]
Further, carbon dioxide gas, water vapor, nitrogen or the like may be supplied as a dilution gas.
As the reaction method, a conventional method such as a fixed bed, a fluidized bed, or a moving bed can be adopted, but a fluidized bed reactor in which reaction heat can be easily removed is preferable.
Separation of the target product from the gas flowing out of the reactor is carried out by a known method. For example, the gas flowing out from the reactor is rapidly cooled or scrubbed with water, etc., and the water-soluble compound such as the target product is dissolved and separated and recovered, and then the dissolved product is distilled and purified to recover the target product. To do.
[0032]
The present invention includes (1) a step of supplying a reaction gas comprising alkane, air or a gas containing oxygen and nitrogen, and, if necessary, a reaction gas composed of ammonia or the like to a reactor filled with a catalyst to perform a gas phase catalytic oxidation reaction. 2) a step of separating the target product from the gas flowing out from the reactor; (3) a gas phase component mainly composed of unreacted alkane after the remaining gas from which the target product has been separated is compressed and absorbed in an organic solvent. And (4) a step of recycling the separated and recovered mixture mainly composed of unreacted alkane to the reactor.
[0033]
As an example of a preferred embodiment of the present invention, FIG. 1 shows a conceptual diagram of a process for producing acrylonitrile from propane, which will be described below.
A gas containing propylene produced as a by-product in the reaction with propane, which is a reaction raw material that has flowed out from the top of the propane stripping tower 9, and from which unnecessary components such as moisture and organic solvents have been removed by the partial condenser 10, Is recycled through line 31. A line 11 is supplied with ammonia and supplemented propane, and a line 12 is supplied with air or oxygen-enriched air. In the reactor 1, acrylonitrile, hydrocyanic acid, propylene, carbon monoxide, carbon dioxide, moisture and the like are generated from propane. The produced reaction gas containing acrylonitrile passes through the line 13 and enters the quenching tower 2, and unreacted ammonia is neutralized with sulfuric acid and extracted from the line 14.
[0034]
  On the other hand, the gas containing unreacted propane, by-product propylene, acrylonitrile, hydrocyanic acid, carbon monoxide, carbon dioxide and the like passes through the line 15 and is led to the absorption tower 3 where the bottom of the recovery / dispersion tower 5 From the line 16, an absorbent containing mainly acrylonitrile is obtained by contacting with water which is the absorbent supplied through the lines 18 and 19. The absorption liquid mainly containing acrylonitrile is preheated by the heat exchanger 4 and then sent to the recovery / dispersion tower 5 through the line 20 and separated by distillation operation. The obtained acrylonitrile and hydrocyanic acid are shown through the line 21. Sent to an unpurified purification system. The gas containing unreacted propane and by-product propylene from the top of the absorption tower 3 passes through the line 17 and is compressed by the compressor 6. From line 22Sodium hydroxide, carbonate or bicarbonateIs added as an aqueous solution if necessary.
[0035]
The compressed gas is led to the propane absorption tower 7 through the line 23 and brought into contact with the organic solvent supplied from the line 27, and an absorption liquid mainly containing propane and propylene is obtained from the line 24. The exhaust gas passes through the line 25 and is discharged to the atmosphere after being processed by a waste gas incinerator (not shown). The absorption liquid mainly containing propane and propylene is supplied to the propane stripping tower 9 through the line 26 after being heated by the steam in the heater 8 through the line 24. Propane and propylene in the absorption liquid are stripped by water vapor supplied through a line 28 and introduced into a partial condenser 10 through a line 29, and organic solvent, moisture, a small amount of impurities, etc. are removed from the line 30 through the partial condensation. And then recycled to the reactor through line 31. The organic solvent extracted from the line 27 is recycled to the propane absorption tower 7.
[0036]
Hereinafter, the method of the present invention will be described with reference to preparation examples of catalysts and preparation examples of acrylonitrile by gas-phase catalytic ammoxidation reaction of propane. However, the present invention is not limited to these examples unless it exceeds the gist. It is not something.
The results of the propane ammoxidation reaction were evaluated based on the results of analysis of the reaction gas, using the propane conversion and acrylonitrile selectivity defined by the following equations as indicators.
Propane conversion (%) = (moles of propane reacted) / (moles of propane fed) × 100
Acrylonitrile selectivity (%) = (number of moles of acrylonitrile produced) / (number of moles of reacted propane) × 100
[0037]
(Preparation of niobium raw material liquid)
In accordance with Japanese Patent Laid-Open No. 11-253801, a niobium raw material liquid was prepared by the following method. Nb in 16.89 kg of water₂O_Five2.58 kg of niobic acid containing 80.2% by weight as oxalic acid dihydrate [H₂C₂O_Four・ 2H₂O] 9.81 kg was mixed. The molar ratio of the charged oxalic acid / niobium is 5.0, and the concentration of charged niobium is 0.53 (mol-Nb / kg-solution). This mixed solution was heated and stirred at 95 ° C. for 1 hour to obtain an aqueous solution in which niobium was dissolved. The aqueous solution was allowed to stand and ice-cooled, and then the solid was separated by suction filtration to obtain a uniform niobium-containing liquid. The niobium-containing liquid had an oxalic acid / niobium molar ratio of 2.34 according to the following analysis.
[0038]
In a crucible, 10 g of this niobium-containing solution is precisely weighed, dried at 95 ° C. overnight, and then heat treated at 600 ° C. for 1 hour.₂O_Five0.8734 g was obtained. From this result, the niobium concentration was 0.6572 (mol-Nb / kg-solution). 3 g of this niobium-containing solution was precisely weighed into a 300 ml glass beaker, 200 ml of hot water at about 80 ° C. was added, and then 10 ml of 1: 1 sulfuric acid was added. While maintaining the solution temperature on a hot stirrer at a liquid temperature of 70 ° C., under stirring, 1/4 N KMnO_FourWas titrated using. KMnO_FourThe end point was a point where the faint pale pink color continued for about 30 seconds or more. The concentration of oxalic acid was 1.539 (mol-oxalic acid / kg) as a result of calculation according to the following formula from titration.
2KMnO_Four+ 3H₂SO_Four+ 5H₂C₂O_Four→ K₂SO_Four+ 2MnSO_Four+ 10CO₂+ 8H₂O
The obtained niobium-containing liquid was used as a niobium raw material liquid (B) for catalyst preparation described below without adjusting the molar ratio of oxalic acid / niobium.
[0039]
(Preparation of catalyst)
Preparation composition formula is Mo₁V_0.31Nb_0.07Sb_0.20B_1.0Ti_0.85O_n/40.2wt%-SiO₂Was prepared as follows.
Ammonium heptamolybdate [(NH_Four)₆Mo₇O_{twenty four}・ 4H₂2.014 kg of O], ammonium metavanadate [NH_FourVO_Three414 g, antimony trioxide [Sb₂O_Three332 g of orthoboric acid [H_ThreeBO_Three708 g, titanium oxide [TiO₂] Was added at 90 ° C. for 2 hours and 30 minutes with stirring, and then cooled to about 70 ° C. to obtain a liquid mixture A. The obtained mixed liquid A was mixed with SiO.₂As a result, 7.84 kg of silica sol containing 30.6 wt% was added. In addition, H₂O₂As a result, 517 g of hydrogen peroxide containing 15 wt% was added and stirring was continued at 50 ° C. for 1 hour. Next, 1.21 kg of the niobium-containing liquid (B) was added to obtain a raw material preparation liquid. The obtained raw material mixture was supplied to a centrifugal spray dryer and dried to obtain a microspherical dry powder. The dryer inlet temperature was 210 ° C and the outlet temperature was 120 ° C. 480 g of the obtained dry powder was filled in a 3 inch diameter SUS kiln furnace and calcined at 660 ° C. for 2 hours under a nitrogen gas flow of 1.8 Nl / min to obtain a catalyst.
[0040]
[Example 1]
The gas phase catalytic oxidation reaction of propane is carried out in the presence of ammonia using the catalyst prepared by the above method, and the produced reaction gas is led to a quenching tower to separate unreacted ammonia, and then led to an absorption tower and absorbed by water. By separating acrylonitrile and the like, the following gas phase component containing unreacted propane was obtained.
That is, 7.0 mol% of propane, 1.2 mol% of oxygen, other nitrogen, carbon dioxide, carbon monoxide, and moisture were contained.
[0041]
This gas phase component is 7 * 10 with a compressor.^FiveCompressed to Pa, 3.7 Nm^ThreeAt a flow rate of 300 mm / min, an inner diameter of 310 mm, and MelapakPlus 252. It was sent to the lower part of a propane absorption tower packed with 10 m of Y. A nozzle was provided at the inlet of the compressor, and a 3 wt% aqueous sodium hydroxide solution was injected at a flow rate of 10 kg / hr. N-paraffin was supplied at 150 l / min from the upper part of the propane absorption tower. This n-paraffin was a mixture of pentadecane, hexadecane, and heptadecane, and the contents were 85 wt%, 13 wt%, and 2 wt%, respectively. Propane absorption tower at 60 ° C, 6 * 10^FiveWhen operated at a pressure of Pa, an n-paraffin solution containing 99.6% of propane fed to the column from the bottom was obtained.
[0042]
This n-paraffin solution was filled with MelapakPlus 252. Y was charged into the upper part of the propane diffusion tower packed with 10 m, and water vapor was introduced at 6.3 kg / hr from the lower part. Propane stripping tower at a temperature of 60 ° C and 0.18 * 10^FiveWhen operated at Pa, a gas containing 99.7% of the propane supplied to the tower from the top was obtained. This gas is 4 * 10^FiveAfter pressurizing to Pa, sending to a condenser and cooling to 30 ° C. to condense the n-paraffin and moisture in the gas, the content of the n-paraffin in the gas component was analyzed. Met.
After this operation was continued for 6 months, the operation was stopped and the inside of the gas compressor, the propane absorption tower, the propane diffusion tower and the packing were checked, and no clogging or blockage was observed. During the series of operations in the stripping tower, no phenomena such as explosion or abnormal combustion were observed.
[0043]
[Reference Example 1]
  Only water was injected into the inlet of the compressor at a flow rate of 20 kg / hr, and the operation was stopped after 6 months of operation with the same catalyst, equipment and the same composition, flow rate, temperature and pressure conditions as in Example 1. However, when the inside of the gas compressor was inspected, a small amount of black-brown solid matter adhered to the outlet piping of the gas compressor, but this did not hinder the operation.
[0044]
[Comparative Example 1]
When the same catalyst, equipment as in Example 1 was used and the same composition, flow rate, temperature, and pressure conditions were used without injecting the aqueous caustic soda solution into the inlet of the compressor, the gas compressor vibrated on the 23rd day. When the inside of the gas compressor was inspected, a large amount of black-brown polymer substance adhered to the inner surface of the compressor and the rotor blade.
[0045]
【The invention's effect】
The present invention ensures high selectivity and catalyst productivity, eliminates the need to replace adsorbents when they are contaminated or deteriorated, avoids the problem of entering the explosive range of combustible materials during desorption, moisture, organic Unnecessary components such as solvents and small amounts of reaction by-products are not brought into the reactor. Loss of unreacted alkanes during purging can be reduced. A method for separating and recovering a gas phase component mainly composed of alkane can be provided.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an embodiment for producing acrylonitrile from propane as an example of an embodiment of the method of the present invention.
[Explanation of symbols]
1 reactor
2 quenching tower
3 Absorption tower
4 Heat exchanger
5 Collection / Dispersion Tower
6 Compressor
7 Propane absorption tower
8 Propane stripping tower
9 Heater
10 Reducer

Claims (5)

The presence of a catalyst, propane, in the presence of ammonia by vapor phase catalytic oxidation reaction in the method for producing an unsaturated Nitrile Le as product, cooling and / or Mizu吸yield the said purpose product from the reaction gas remaining upon compressing the gas stream, sodium hydroxide, gas compression method which is characterized in that the presence of carbonate or bicarbonate to the inlet gas stream of the compressor which is more recovered. The process of claim 1 wherein the sodium hydroxide, carbonate or bicarbonate is added to the gas stream in an aqueous solution . The method of claim 2, wherein the amount of sodium hydroxide, carbonate or bicarbonate added is 0.01 to 10 wt% with respect to the gas stream. The process according to claim 2, wherein the amount of sodium hydroxide, carbonate or bicarbonate added is 0.05 to 5 wt% with respect to the gas stream. It claims 1 to 4 method, wherein the said unsaturated nitrile is acrylonitrile.

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