JP2005194234A - Method for producing acrylonitrile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economically advantageous method for producing acrylonitrile by which a high yield of the acrylonitrile is kept over a long period of time. <P>SOLUTION: The method for producing the acrylonitrile comprises using a granular catalyst comprising ≥85 mass% particles having 20-120 μm particle diameters, ≤5 mass% particles having <20 μm particle diameters, and 25-40 mass% particles having 20-44 μm particle diameters, and during the continuance of the reaction, extracting 0.05-1 mass% particles having 20-44 μm particle diameters per day based on the whole particles having 20-44 μm particle diameters in the reactor 2 from the reactor 2 to the exterior of the reactor 2, and supplying the granular catalyst comprising ≥85 mass% particles having 20-120 μm particle diameters, ≤5 mass% particles having <20 μm particle diameters, and 41-80 mass% particles having 20-44 μm particle diameters in an amount corresponding to 0.03-1 mass% of the whole granular catalyst in the reactor 2 per day. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a process for producing acrylonitrile by vapor phase catalytic ammoxidation of propylene with molecular oxygen and ammonia.

Acrylonitrile is currently industrially synthesized by a method widely known as the “fluidized bed ammoxidation process”.
Numerous proposals have been made regarding catalysts used in the synthesis of acrylonitrile by vapor-phase catalytic ammoxidation of propylene. These mainly relate to techniques for improving so-called catalytic properties such as activity and selectivity.

  For example, Japanese Patent Publication No. 61-13701 (Patent Document 1), Japanese Patent Application Laid-Open No. 59-204163 (Patent Document 2), Japanese Patent Application Laid-Open No. 1-222850 (Patent Document 3), Japanese Patent Application Laid-Open No. 10-43595 ( Patent Document 4), Japanese Patent Application Laid-Open No. 10-156185 (Patent Document 5), US Pat. No. 5,688,739 (Patent Document 6), etc. disclose a catalyst mainly composed of molybdenum and bismuth. These mainly define the constituent elements of the catalyst for obtaining a catalyst having a high acrylonitrile yield and the composition ratio thereof, but are not mentioned to the point to be noted in industrial use.

In general, in the fluidized bed ammoxidation process, various measures are taken with respect to the particle size of the catalyst particles in order to suppress catalyst loss during the reaction and to realize a good fluidized state of the catalyst.
For example, Japanese Patent Application Laid-Open No. 52-140490 (Patent Document 7) discloses that in a method for producing a fluidized bed ammoxidation reaction catalyst mainly composed of antimony, particles having a particle size of 20 μm or less are reduced to 5% by mass or less. A method of adjusting particles having a particle size of 200 μm or more to 15% by mass or less is disclosed. Japanese Patent Application Laid-Open No. 2002-233768 (Patent Document 8) discloses that 95% by mass or more of catalyst particles having a particle diameter of 5 to 150 μm and 3 to 30 mass of catalyst particles having a particle diameter of 20 to 30 μm. The method of adjusting to% is disclosed.

In these methods, catalyst particles having a small particle diameter, especially catalyst particles having a particle diameter of 20 μm or less, are small in mass, and therefore are easily entrained by the reaction gas and scattered outside the reactor, making it difficult to be used effectively for catalytic reactions. , And catalyst particles having a large particle size, particularly catalyst particles having a particle size of 150 μm or more or 200 μm or more, are based on the knowledge that they are difficult to flow in the reactor and difficult to be used effectively for catalytic reactions because of their large mass. is there.
These methods are certainly considered to be effective when focusing on the fluidized state of the catalyst particles in the fluidized bed ammoxidation process. However, in order to continue producing the target reaction product with a higher yield over a long period of time, these methods are still insufficient, and further contrivance is desired from an industrial standpoint.

That is, usually, when the synthesis reaction of acrylonitrile by the fluidized bed ammoxidation process is continued for a long time, deterioration of the catalyst is inevitable. Therefore, industrially, a method is employed in which a part of the catalyst in the reactor is withdrawn periodically at a certain ratio, and at the same time, an equivalent amount of a new catalyst is replenished in the reactor. However, this method is effective for maintaining the acrylonitrile yield at a high level over a long period of time. However, since a considerable amount of catalyst replenishment is required, it is not preferable in terms of economy, and improvement is desired. Yes.
Japanese Patent Publication No. 61-13701 JP 59-204163 A JP-A-1-228950 JP-A-10-43595 JP-A-10-156185 US Pat. No. 5,688,739 Japanese Patent Laid-Open No. 52-140490 JP 2002-233768 A

  The present invention has been made to solve the above problems, and provides a method for producing acrylonitrile by a fluidized bed ammoxidation process capable of maintaining a high acrylonitrile yield over a long period of time in an economically advantageous manner. With the goal.

  In the fluidized bed ammoxidation process, the inventors of the present invention continuously carried out an acrylonitrile synthesis reaction for a long period of time using a particulate catalyst having a particle size distributed in the range of 20 to 120 μm. When the reaction was continued for a long time, the acrylonitrile yield gradually decreased due to catalyst deterioration. As a result of examining the catalyst after this experiment in detail for each particle diameter, it was found that the degree of deterioration differs depending on the particle diameter of the catalyst particles. That is, it has been found that the degree of deterioration is large when the particle size is small, particularly when the particle size is in the range of 20 to 44 μm.

  And the present inventors came to this invention based on this knowledge which the present inventors discovered. That is, when the reaction is continued for a long period of time, a part of the catalyst in the reactor is periodically withdrawn at a certain ratio, and at the same time, an equivalent amount of new catalyst is replenished in the reactor. If a method of selectively extracting catalyst particles having a particle diameter of 20 to 44 μm and simultaneously supplying a new catalyst with an equal amount and an equivalent particle diameter is employed, a long period of time can be achieved even if a relatively small amount of new catalyst is supplied per unit time. In the meantime, the inventors have reached an invention in which the acrylonitrile yield can be maintained at a high level.

  The method for producing acrylonitrile of the present invention is a method for producing acrylonitrile by reacting propylene with molecular oxygen and ammonia in a fluidized bed reactor containing a particulate catalyst. The ratio of particles having a diameter in the range of 20 to 120 μm is 85% by mass or more, the ratio of particles having a particle diameter of less than 20 μm is 5% by mass or less, and the ratio of particles having a diameter of 20 to 44 μm is 25 to 40%. When the reaction is continued, particles having a particle size in the range of 20 to 44 μm are collected from the particulate catalyst in the reactor for all the particles having a particle size of 20 to 44 μm in the reactor per day. An amount corresponding to 0.05 to 1% by mass is extracted from the reactor, and the proportion of particles having a particle size in the range of 20 to 120 μm is 85% by mass or more, and the proportion of particles having a particle size of less than 20 μm is 5%. quality % Of the particulate catalyst having a particle size in the range of 20 to 44 μm and a ratio of 41 to 80% by mass of 0.03 to 1% by mass of all the particulate catalysts in the reactor per day. The method is characterized in that an amount corresponding to is supplied to the reactor from outside the reactor.

Here, the extraction of the particles having a particle diameter in the range of 20 to 44 μm from the reactor may be performed continuously or may be performed once every 1 to 30 days.
Further, the replenishment of the particulate catalyst from the outside of the reactor into the reactor may be performed continuously or may be performed once every 1 to 30 days.
Moreover, it is desirable to use what has a composition represented by the following general formula (1) or the following general formula (2) as the particulate catalyst.

General formula (1):
_{Sb a Fe b C c D d} E e O f (SiO 2) g
(Wherein Sb, Fe and O represent antimony, iron and oxygen, respectively, C represents at least one element selected from the group consisting of cobalt, nickel, manganese, uranium, cerium, tin and copper; D Represents at least one element selected from the group consisting of molybdenum, vanadium and tungsten, and E represents magnesium, calcium, strontium, barium, lanthanum, titanium, zirconium, niobium, tantalum, chromium, rhenium, ruthenium, osmium, rhodium Selected from the group consisting of iridium, palladium, platinum, silver, zinc, cadmium, boron, aluminum, gallium, indium, sodium, potassium, rubidium, cesium, thallium, germanium, lead, phosphorus, arsenic, bismuth, selenium and tellurium Small Represents Kutomo one element, SiO ₂ represents silica, denotes a, b, c, d, e, f and g are atomic ratios of respective elements, and when a = 10, 1 ≦ b ≦ 20, (1 ≦ c ≦ 20, 0 ≦ d ≦ 20, 0 ≦ e ≦ 20, 10 ≦ g ≦ 200, and f is an atomic ratio of oxygen necessary to satisfy the valence of each component.)

General formula (2):
Mo _{h B i} Fe _j F _k G _l O _m (SiO ₂ ) _n
(Wherein Mo, Bi, Fe and O represent molybdenum, bismuth, iron and oxygen, respectively, F represents at least one element selected from the group consisting of sodium, potassium, rubidium, cesium and thallium; Is cobalt, nickel, copper, zinc, magnesium, calcium, strontium, barium, titanium, vanadium, chromium, manganese, tungsten, silver, aluminum, phosphorus, boron, tin, lead, gallium, germanium, arsenic, antimony, niobium, tantalum At least one selected from the group consisting of zirconium, indium, sulfur, selenium, tellurium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, holmium, erbium, thulium and ytterbium Represent elements, SiO ₂ represents silica, represents h, i, j, k, l, m and n are the atomic ratios of respective elements, and when h = 12, 0.1 ≦ i ≦ 5,0. 1 ≦ j ≦ 10, 0.01 ≦ k ≦ 3, 0 ≦ l ≦ 20, 10 ≦ n ≦ 200, and m is an atomic ratio of oxygen necessary to satisfy the valence of each component. )

  According to the method for producing acrylonitrile of the present invention, a high acrylonitrile yield can be maintained over a long period of time by an economically advantageous method.

Hereinafter, the present invention will be described in detail.
Acrylonitrile is produced by reacting propylene with molecular oxygen and ammonia in a fluidized bed reactor containing a particulate catalyst.
Specifically, for example, as shown in FIG. 1, a reactor 2 provided with a fluidized bed 1 of a particulate catalyst, a raw material gas sparger 3 for supplying propylene, molecular oxygen and ammonia into the reactor 2, It is produced by using a fluidized bed reactor which is arranged in the reactor 2 and which comprises a cyclone 4 for separating a gas containing acrylonitrile and a catalyst.

Here, the pipe-type raw material gas sparger 3 in FIG. 1 has a plurality of nozzle holes 5 opened downward from the reactor 2, and the gas 6 introduced from the nozzle holes 5 corresponds to FIG. As shown in the image diagram shown in FIG. 1, once blown out at a high speed below the reactor 2, it rises above the reactor 2.
Further, as shown in FIG. 3, the catalyst contained in the gas introduced into the cyclone 4 is separated from the gas while rotating at high speed in the cyclone 4, and returned to the fluidized bed 1 through the dipleg 7. Middle dashed line). A gas containing acrylonitrile is discharged from the reactor 2 through the discharge pipe 8.

  The catalyst used in the present invention needs to be in the form of particles, and the shape is preferably spherical. The spherical shape here indicates that it is substantially spherical, and there may be some distortion or depression. Moreover, if it is a ratio of 10 mass% or less, you may include the thing by which the spherical shape was broken into two or more, the thing by which two or more spherical shapes were stuck, etc.

Moreover, as the size, the ratio of the particles having a particle diameter of 20 to 120 μm is 85% by mass or more, the ratio of the particles having a particle diameter of less than 20 μm is 5% by mass or less, and the particle diameter is 20 to 44 μm. It is important that the proportion of particles in the range is 25-40% by weight.
Particles having a particle size of less than 20 μm are small in mass, and thus are easily entrained by the reaction gas during the reaction and scattered outside the reactor 2, resulting in so-called catalyst loss. The catalyst loss leads to a decrease in the reaction rate, that is, the propylene conversion rate. Therefore, the smaller the proportion of particles having a particle size of less than 20 μm, the better. Particles having a particle size of less than 20 μm are 5% by mass or less, preferably 3% by mass or less.

Particles having a particle size exceeding 120 μm are difficult to fluidize well in the reactor 2 because of their large mass. For this reason, if the ratio of the particles having a particle size exceeding 120 μm is too large, the fluidized state is deteriorated, which causes a decrease in the acrylonitrile yield. Therefore, the smaller the proportion of particles with a particle size exceeding 120 μm, the better. The particles having a particle size exceeding 120 μm are preferably 10% by mass or less, more preferably 5% by mass or less.
Moreover, in order to implement | achieve a favorable fluidization state, suppressing a catalyst loss, the particle | grains of the particle size of 20-120 micrometers are effective. Of these, the proportion of particles in the range of 20 to 44 μm is particularly important. Particles having a particle size in the range of 20 to 120 μm are 25 to 40% by mass, preferably 28 to 38% by mass.

  The acrylonitrile production method of the present invention is characterized in that particles having a particle size in the range of 20 to 44 μm are obtained from the particulate catalyst in the reactor 2 and all particles having a particle size of 20 to 44 μm in the reactor 2 per day. While the amount corresponding to 0.05 to 1% by mass is withdrawn from the reactor, the proportion of particles having a particle size of 20 to 120 μm is 85% by mass or more, and the proportion of particles having a particle size of less than 20 μm is 5% by mass or less and the proportion of particles having a particle size in the range of 20 to 44 μm is 41 to 80% by mass of 0.03 to 0.03 of all the particulate catalysts in the reactor 2 per day. The purpose is to continue the reaction of propylene with molecular oxygen and ammonia while supplying an amount corresponding to 1% by mass from outside the reactor 2 into the reactor 2.

  The amount of particles having a particle size of 20 to 44 μm extracted from the reactor 2 per day is 0.05 to 1% by mass based on the total amount of particles having a particle size of 20 to 44 μm in the total particulate catalyst in the reactor 2. Preferably, it is 0.2-0.6 mass%. If the amount extracted here is too small, the deteriorated catalyst will be accumulated in the reactor 2, leading to a decrease in the acrylonitrile yield. On the other hand, increasing the amount to be extracted is advantageous in terms of preventing a decrease in the acrylonitrile yield, but it is economically disadvantageous because the amount of catalyst to be replenished is increased accordingly. Therefore, extracting an unnecessarily large amount is not preferable from an industrial viewpoint.

When extracting particles having a particle diameter of 20 to 44 μm from the inside of the reactor 2, it is not impeded to extract particles outside the particle diameter of 20 to 44 μm. In particular, it is considered that particles having a particle size of less than 20 μm are more likely to be deteriorated than particles having a particle size of 20 to 44 μm, and therefore, it is preferable to actively extract the particles.
Further, since the particle size exceeding 44 μm is somewhat deteriorated although the degree of deterioration is small, it is preferably extracted to some extent. However, the ratio of extracting particles having a particle diameter of 44 μm, that is, the ratio of extracting all particles having a particle diameter exceeding 44 μm in the total particulate catalyst in the reactor 2 is the total amount of particles having a particle diameter of 20 to 44 μm. Do not exceed the rate of extraction from. Further, the larger the difference in proportion, that is, the smaller the proportion of particles with a particle size exceeding 44 μm, the more economically advantageous because the amount of particulate catalyst to be replenished can be reduced.

  In the present invention, the method for extracting particles having a particle size of 20 to 44 μm at a specific ratio is not particularly limited. For example, the particulate catalyst once extracted from the reactor 2 by sieving by a usual method is screened to obtain a particle size. A method of returning all or part of the particles outside the range of 20 to 44 μm back into the reactor 2 is conceivable. In addition, since a cyclone 4 for collecting the catalyst is provided in the normal reactor 2, when adjusting so as to reduce the collection efficiency, only the catalyst particles having a small particle diameter are selectively converted into the reaction gas. Accompanied and carried out of the reactor 2. Adjustment of the collection efficiency of the cyclone 4 can be easily performed by blowing air or other gas upward into the cyclone 4, and this method is operated as a method for selectively extracting particles having a particle size of 20 to 44 μm. This is an advantageous method in terms of ease.

  In the present invention, the frequency with which the particulate catalyst in the reactor 2 is withdrawn is not particularly limited, and may be withdrawn continuously all the time or once every several hours to several tens of days. Moreover, you may combine extracting continuously and extracting once every several hours-dozens of days. In order to keep the acrylonitrile yield at a constant level at all times, a continuous extraction method is advantageous. For this purpose, it is preferable to attach equipment for easily extracting a constant amount. The method of extracting the particulate catalyst by reducing the collection efficiency of the cyclone 4 installed in the reactor 2 as described above is preferable because it is simple and highly accurate as a method of continuously extracting. The method of reducing the collection efficiency of the cyclone 4 is not particularly limited, but for example, a method of blowing a gas flow such as air upward from the lower part of the cyclone 4 is preferable because of excellent controllability.

  When extracting at a frequency of once every several hours to several tens of days, the yield of acrylonitrile decreases between the extraction and the next extraction. Therefore, the interval is preferably as short as possible. However, if the interval is too short, operational difficulties occur, and therefore the frequency is preferably once every 1 to 30 days, and more preferably once every 1 to 10 days.

  In the present invention, when a part of the particulate catalyst in the reactor 2 is extracted, it is important to replenish the reactor 2 with an equivalent amount of the particulate catalyst at the same time. At that time, a new catalyst is preferable for the particulate catalyst to be replenished. However, if the catalyst is not substantially different from that of the new catalyst, that is, if the catalyst is not essentially deteriorated, it is used to some extent. It does not matter.

In the present invention, the particle size distribution of the particulate catalyst in the reactor 2 is preferable over a long period (the proportion of particles having a particle size in the range of 20 to 120 μm is 85 mass% or more and the proportion of particles having a particle size of less than 20 μm is It is important that the ratio of the particles in the range of 5 mass% or less and the particle size in the range of 20 to 44 μm is maintained at 25 to 40 mass%.
That is, in the present invention, there is a feature in selectively extracting a large amount of particles having a particle size of 20 to 44 μm. Therefore, in order to maintain the particle size distribution of the particulate catalyst in the reactor 2 in a preferable state, Naturally, it is necessary to replenish a particulate catalyst containing many particles having a particle size in the range of 20 to 44 μm.
Therefore, the proportion of particles in the range of 20 to 44 μm in the particulate catalyst to be replenished is 41 to 80% by mass, preferably 45 to 70% by mass.

  Further, the amount of the particulate catalyst to be replenished may be basically the same as the amount withdrawn, specifically 0.03 to 1% by mass of the total particulate catalyst in the reactor 2 per day. . However, since it is important to maintain the reaction rate, that is, the propylene conversion rate at a certain level, the amount of the particulate catalyst to be replenished may be increased or decreased with respect to the amount extracted depending on the situation. Absent.

  In the present invention, the frequency of replenishing the particulate catalyst in the reactor 2 is not particularly limited, and may be continuously replenished or may be replenished once every several hours to several tens of days. Good. In order to always maintain the acrylonitrile yield at a constant level, it is preferable to continuously replenish the same amount while continuously extracting the particulate catalyst. In order to replenish continuously, it is preferable to attach a facility or the like that can easily replenish a certain amount.

  Further, when replenishing once every several hours to several tens of days, the acrylonitrile yield decreases between the replenishment and the next replenishment. Therefore, the interval is preferably as short as possible. However, if the interval is too short, operational difficulties occur, and therefore the frequency is preferably once every 1 to 30 days, and more preferably once every 1 to 10 days. In order to keep the propylene conversion rate as stable as possible, it is preferable to replenish the particulate catalyst in accordance with the frequency and timing of extraction of the particulate catalyst.

The particulate catalyst in the present invention desirably has a composition represented by the following general formula (1) or general formula (2).
General formula (1):
_{Sb a Fe b C c D d} E e O f (SiO 2) g
(Wherein Sb, Fe and O represent antimony, iron and oxygen, respectively, C represents at least one element selected from the group consisting of cobalt, nickel, manganese, uranium, cerium, tin and copper, and D Represents at least one element selected from the group consisting of molybdenum, vanadium and tungsten, and E represents magnesium, calcium, strontium, barium, lanthanum, titanium, zirconium, niobium, tantalum, chromium, rhenium, ruthenium, osmium, rhodium Selected from the group consisting of iridium, palladium, platinum, silver, zinc, cadmium, boron, aluminum, gallium, indium, sodium, potassium, rubidium, cesium, thallium, germanium, lead, phosphorus, arsenic, bismuth, selenium and tellurium Small Represents Kutomo one element, SiO ₂ represents silica, denotes a, b, c, d, e, f and g are atomic ratios of respective elements, and when a = 10, 1 ≦ b ≦ 20, (1 ≦ c ≦ 20, 0 ≦ d ≦ 20, 0 ≦ e ≦ 20, 10 ≦ g ≦ 200, and f is an atomic ratio of oxygen necessary to satisfy the valence of each component.)

General formula (2):
Mo _{h B i} Fe _j F _k G _l O _m (SiO ₂ ) _n
(Wherein Mo, Bi, Fe and O represent molybdenum, bismuth, iron and oxygen, respectively, F represents at least one element selected from the group consisting of sodium, potassium, rubidium, cesium and thallium; Is cobalt, nickel, copper, zinc, magnesium, calcium, strontium, barium, titanium, vanadium, chromium, manganese, tungsten, silver, aluminum, phosphorus, boron, tin, lead, gallium, germanium, arsenic, antimony, niobium, tantalum At least one selected from the group consisting of zirconium, indium, sulfur, selenium, tellurium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, holmium, erbium, thulium and ytterbium Represent elements, SiO ₂ represents silica, represents h, i, j, k, l, m and n are the atomic ratios of respective elements, and when h = 12, 0.1 ≦ i ≦ 5,0. 1 ≦ j ≦ 10, 0.01 ≦ k ≦ 3, 0 ≦ l ≦ 20, 10 ≦ n ≦ 200, and m is an atomic ratio of oxygen necessary to satisfy the valence of each component. )

  In the present invention, as a method for preparing the particulate catalyst, an aqueous slurry containing the catalyst component is prepared, the obtained aqueous slurry is dried, and the obtained dried product is heated at a temperature in the range of 500 to 750 ° C. A method of firing is particularly preferable.

  There is no restriction | limiting in particular as a raw material used for preparation of aqueous slurry, Nitrate, carbonate, acetate, ammonium salt, an oxide, a halide, etc. of each element can be used in combination. For example, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride, etc. can be used as the molybdenum raw material. Moreover, as a silica raw material, colloidal silica is preferable and it can select from a commercially available thing suitably and can be used. About the colloidal particle size of colloidal silica, 5-80 nm is preferable and 10-40 nm is more preferable. There is no restriction | limiting in particular also about the silica content in colloidal silica, and 10-50 mass% is especially preferable. Further, a mixture of a plurality of colloidal silicas having different colloidal particle diameters and / or silica contents may be used.

The aqueous slurry may be subjected to heat treatment such as aging and concentration in the range of 70 to 105 ° C. as necessary.
Although there is no restriction | limiting in particular as a drying method of an aqueous slurry, Since a spherical form is preferable as a shape of the dried material obtained and adjustment of a particle size is comparatively easy, spray drying is especially preferable.

  Subsequently, a desired catalytically active structure is formed by calcining the obtained dried product at a temperature in the range of 500 to 750 ° C. The firing time is not particularly limited, but if it is too short, a good catalyst cannot be obtained. There is no restriction | limiting in particular also about the method of baking, A general purpose baking furnace can be used, and a rotary kiln, a fluidized baking furnace, etc. are used preferably industrially.

  The method for obtaining a particulate catalyst having a desired particle size distribution in the present invention is not particularly limited, but when the aqueous slurry is dried with a spray dryer, the concentration and viscosity of the slurry are appropriately adjusted, and spraying is performed. A certain degree of particle size adjustment is possible by adjusting the spraying conditions in drying. Furthermore, in order to make it closer to the desired particle size distribution, it is also effective to perform classification operations such as sieving the obtained dried or fired product.

  When the acrylonitrile is produced by vapor phase catalytic ammoxidation of propylene with molecular oxygen and ammonia using the particulate catalyst thus obtained, it is preferable to use a fluidized bed reactor. The concentration of propylene in the raw material gas can be varied within a wide range, 1 to 20% by volume is appropriate, and 3 to 15% by volume is particularly preferable.

  It is industrially advantageous to use air as an oxygen source when performing vapor phase ammoxidation, but if necessary, air enriched with pure oxygen can also be used. The molar ratio of propylene to oxygen in the raw material gas is preferably 1: 1.5 to 1: 3, and the molar ratio of propylene to ammonia is preferably 1: 1 to 1: 1.5. The source gas can be diluted with an inert gas, water vapor or the like. The reaction pressure is in the range of normal pressure to several atmospheres. The reaction temperature is preferably in the range of 400 to 500 ° C.

In the method for producing acrylonitrile of the present invention described above, the proportion of particles having a particle size in the range of 20 to 120 μm is 85 mass% or more as the particulate catalyst, and the proportion of particles having a particle size of less than 20 μm is 5 mass. %, And the proportion of particles having a particle size in the range of 20 to 44 μm is 25 to 40% by mass, so that the reaction of propylene with molecular oxygen and ammonia proceeds efficiently, and acrylonitrile The yield is high.
In the method for producing acrylonitrile of the present invention, a predetermined amount of particles having a relatively large degree of deterioration in the range of 20 to 44 μm are selectively extracted out of the reactor 2 and the particle size of 20 Continue the reaction of propylene with molecular oxygen and ammonia while supplying a predetermined amount of a particulate catalyst for replenishment containing a relatively large amount of particles in the range of ˜44 μm into the reactor 2 from outside the reactor 2 Therefore, the amount of the particulate catalyst to be replenished can be reduced as compared with the case where the particles having a particle diameter of 20 to 44 μm are not selectively extracted.
Therefore, a high acrylonitrile yield can be maintained over a long period of time by an economically advantageous method.

  The fluidized bed reactor used in the method for producing acrylonitrile of the present invention is not limited to the illustrated example, and a fluid capable of reacting propylene with molecular oxygen and ammonia in the presence of a particulate catalyst. Any bed reactor can be used.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
Production of acrylonitrile by propylene ammoxidation was carried out using a fluidized bed reactor having a tower diameter of 2 inches and containing a cyclone. At this time, a mixed gas of propylene / ammonia / air / water vapor = 1 / 1.2 / 9.5 / 0.5 (molar ratio) was introduced into the reactor at a gas linear velocity of 18 cm / second, and the reaction temperature was 440. The reaction pressure was 200 KPa.

Reaction test analysis was performed by gas chromatography.
The contact time and acrylonitrile yield are defined as follows:
Acrylonitrile yield (%) = B / A × 100
Here, A represents the number of moles of propylene supplied, and B represents the number of moles of produced acrylonitrile.
The particle size distribution of the particulate catalyst was measured using a laser diffraction type particle size distribution measuring apparatus.

[Example 1]
In a mixed solution of 4956.7 parts by mass of 30% by mass colloidal silica and 3000 parts by mass of pure water, 1248.3 parts by mass of ammonium paramolybdate was dissolved (solution A).
Separately, to 1300 parts by mass of a 17% by mass nitric acid aqueous solution, 476.1 parts by mass of iron (III) nitrate, 685.2 parts by mass of nickel nitrate, 226.6 parts by mass of magnesium nitrate, 171.4 parts by mass of cobalt nitrate, 94% of chromium nitrate .3 parts by mass, 127.9 parts by mass of cerium nitrate, 142.9 parts by mass of bismuth nitrate, 5.2 parts by mass of rubidium nitrate, and 4.2 parts by mass of potassium nitrate were dissolved (Liquid B).
While the liquid A was well stirred, the liquid B was mixed there to obtain an aqueous slurry.

The obtained aqueous slurry was dried using a spray dryer to obtain a spherical dry powder. The obtained dried powder was calcined at 250 ° C. for 2 hours and then at 450 ° C. for 3 hours, and then fluidly calcined at 590 ° C. for 2 hours to obtain catalyst (1).
The composition of the obtained catalyst (1) was calculated from the raw material charge as follows.
Mo ₁₂ Bi _0.5 Fe ₂ Ce _0.5 Cr _0.4 Ni ₄ Mg _1.5 Co ₁ K _0.07 Rb _0.06 O _x (SiO ₂ ) ₄₂
(Here, x is the atomic ratio of oxygen necessary to satisfy the valence of each element.)
As a result of examining the particle size distribution of the catalyst (1), the ratio of the particle size of 20 to 120 μm is 98.5 mass%, the ratio of the particle diameter of less than 20 μm is 1.5 mass%, and the ratio of the particle diameter of 20 to 44 μm is 35. It was 7 mass%.

Further, by sieving the catalyst (1), the ratio of the particle diameter of 20 to 120 μm is 97.3% by mass, the ratio of the particle diameter of less than 20 μm is 2.7 mass%, and the ratio of the particle diameter of 20 to 44 μm is 65 The catalyst (2) was obtained by adjusting the particle size distribution to mass%.
When 2500 g of catalyst (1) was charged into the reactor and acrylonitrile synthesis reaction was carried out, the acrylonitrile yield was 82.6%.

When the reaction was continued for 7 days, 78.8 g of the catalyst was extracted from the reactor, and this was sieved by the same operation as in the preparation of the catalyst (2), so that the particle size ranged from 44 to 120 μm. 35.5 g of particles were immediately returned to the reactor.
This operation resulted in a particle size of 97.3% by mass with a particle size of 20-120 μm, 2.7% by mass with a particle size of less than 20 μm, and 65% by mass with a particle size of 20-44 μm. This is synonymous with the extraction of the catalyst having a distribution out of the 43.3 g reactor. In addition, the extraction of this amount in 7 days means that the amount of particles in the range of 20 to 44 μm in the catalyst existing in the reactor is 0.45% by mass of the range of particles per day. This corresponds to the extraction of the amount corresponding to.

Together with the extraction operation, 43.3 g of catalyst (2) was supplied into the reactor. When this replenishment amount is converted per day, it is estimated that the amount corresponds to 0.25% by mass of the total catalyst present in the reactor.
Thereafter, the reaction was continuously carried out for a total of 42 days while performing the same catalyst extraction and catalyst replenishment operation every 7 days.
As a result of analysis after removing the catalyst and replenishing the catalyst on the 42nd day, the acrylonitrile yield was 82.3%.

[Example 2]
Catalyst (1) and catalyst (2) were obtained in the same manner as in Example 1, and the reaction was started in the same manner as in Example 1.
When the reaction was continued for 14 days, 157.6 g of the catalyst was withdrawn from the reactor and sieved in the same manner as in the preparation of the catalyst (2), so that the particle size ranged from 44 to 120 μm. 71 g of particles were immediately returned to the reactor.
This operation resulted in a particle size of 97.3% by mass with a particle size of 20-120 μm, 2.7% by mass with a particle size of less than 20 μm, and 65% by mass with a particle size of 20-44 μm. This is synonymous with the extraction of the catalyst having a distribution outside the 86.6 g reactor. In addition, the extraction of this amount in 14 days means that the amount of particles in the range of 20 to 44 μm in the catalyst existing in the reactor is 0.45% by mass of the range of particles per day. This corresponds to the amount extracted from the reactor and is the same as in Example 1.

Together with the extraction operation, 86.6 g of catalyst (2) was supplied into the reactor. When this replenishment amount is converted per day, it is estimated that it corresponds to 0.25% by mass of the total catalyst present in the reactor, and this is the same as in Example 1.
Thereafter, the reaction was continuously carried out for a total of 42 days while the same catalyst extraction and catalyst replenishment operation as described above was performed every 14 days.
As a result of analysis after removing the catalyst and replenishing the catalyst on the 42nd day, the acrylonitrile yield was 82.1%.

[Example 3]
Catalyst (1) and catalyst (2) were obtained in the same manner as in Example 1, and the reaction was started in the same manner as in Example 1.
When the reaction was continued for 7 days, 140.1 g of the catalyst was withdrawn from the reactor and sieved by the same operation as in the preparation of the catalyst (2), and the particle size ranged from 44 to 120 μm. 63.1 g of particles were immediately returned to the reactor.
This operation resulted in a particle size of 97.3% by mass with a particle size of 20-120 μm, 2.7% by mass with a particle size of less than 20 μm, and 65% by mass with a particle size of 20-44 μm. This is equivalent to extracting 77 g of the catalyst having a distribution out of the reactor. In addition, the extraction of this amount in 7 days means that 0.8% by mass of the particles in the range per day for the particles in the range of 20 to 44 μm in the catalyst present in the reactor. This corresponds to the extraction of the amount corresponding to.

Together with the extraction operation, 77 g of catalyst (2) was supplied into the reactor. When this replenishment amount is converted per day, it is estimated that the amount corresponds to 0.44% by mass of the total catalyst present in the reactor.
Thereafter, the reaction was continuously carried out for a total of 42 days while performing the same catalyst extraction and catalyst replenishment operation every 7 days.
As a result of analysis after removing the catalyst and replenishing the catalyst on the 42nd day, the yield of acrylonitrile was 82.4%.

[Example 4]
Catalyst (1) and catalyst (2) were obtained in the same manner as in Example 1, and the reaction was started in the same manner as in Example 1.
When the reaction was continued for 7 days, 26.2 g of the catalyst was extracted from the reactor and sieved by the same operation as in the preparation of the catalyst (2), and the particle size was in the range of 44 to 120 μm. 11.8 g of particles were immediately returned to the reactor.
This operation resulted in a particle size of 97.3% by mass with a particle size of 20-120 μm, 2.7% by mass with a particle size of less than 20 μm, and 65% by mass with a particle size of 20-44 μm. This is synonymous with the extraction of the catalyst having a distribution outside the 14.4 g reactor. In addition, the extraction of this amount in 7 days means that 0.15% by mass of the particles in the range per day for the particles in the range of 20 to 44 μm in the catalyst present in the reactor. This corresponds to the extraction of the amount corresponding to.

Then, together with the extraction operation, 14.4 g of catalyst (2) was supplied into the reactor. When this replenishment amount is converted per day, it is estimated that the amount corresponds to 0.08% by mass of the total catalyst present in the reactor.
Thereafter, the reaction was continuously carried out for a total of 42 days while performing the same catalyst extraction and catalyst replenishment operation every 7 days.
As a result of analysis after removing the catalyst and replenishing the catalyst on the 42nd day, the acrylonitrile yield was 81.5%.

[Comparative Example 1]
Catalyst (1) and catalyst (2) were obtained in the same manner as in Example 1, and the reaction was started in the same manner as in Example 1.
When the reaction was continued for 7 days, 3.5 g of the catalyst was withdrawn from the reactor and sieved by the same operation as in the preparation of the catalyst (2), so that the particle size ranged from 44 to 120 μm. 1.6 g of particles were immediately returned to the reactor.
This operation resulted in a particle size of 97.3% by mass with a particle size of 20-120 μm, 2.7% by mass with a particle size of less than 20 μm, and 65% by mass with a particle size of 20-44 μm. It is synonymous with extracting 1.9 g of the catalyst having a distribution out of the reactor. In addition, the extraction of this amount in 7 days means that 0.02% by mass of the particles in the range per day for the particles in the range of 20 to 44 μm in the catalyst existing in the reactor. This corresponds to the extraction of the amount corresponding to.

Together with the extraction operation, 1.9 g of catalyst (2) was supplied into the reactor. When this replenishment amount is converted per day, it can be estimated as an amount corresponding to 0.01% by mass of the total catalyst present in the reactor.
Thereafter, the reaction was continuously carried out for a total of 42 days while performing the same catalyst extraction and catalyst replenishment operation every 7 days.
As a result of analysis after removing the catalyst and replenishing the catalyst on the 42nd day, the yield of acrylonitrile was 78.9%.

[Comparative Example 2]
The catalyst (1) was obtained in the same manner as in Example 1, and the reaction was started in the same manner as in Example 1.
When the reaction was continued for 7 days, 43.3 g of catalyst was extracted from the reactor. That is, it is the same as the catalyst (1) in which the ratio of the particle diameter of 20 to 120 μm is 98.5 mass%, the ratio of the particle diameter of less than 20 μm is 1.5 mass%, and the ratio of the particle diameter of 20 to 44 μm is 35.7 mass%. A catalyst having a particle size distribution was extracted from the 43.3 g reactor. In addition, when this amount was extracted in 7 days, 0.25% by mass of the particles in the range per day for the particles having a particle size of 20 to 44 μm in the catalyst existing in the reactor. This corresponds to the extraction of the amount corresponding to.

Together with the extraction operation, 43.3 g of the catalyst (1) was supplied into the reactor. When this replenishment amount is converted per day, it is estimated that the amount corresponds to 0.25% by mass of the total catalyst present in the reactor.
Thereafter, the reaction was continuously carried out for a total of 42 days while performing the same catalyst extraction and catalyst replenishment operation every 7 days.
As a result of analysis after removing the catalyst and replenishing the catalyst on the 42nd day, the acrylonitrile yield was 80.2%.

[Example 5]
Catalyst (1) and catalyst (2) were obtained in the same manner as in Example 1, and the reaction was started in the same manner as in Example 1.
When the reaction was continued for 42 days, 472.8 g of the catalyst was withdrawn from the reactor and sieved in the same manner as in the preparation of the catalyst (2), so that the particle size was in the range of 44 to 120 μm. 213.1 g of particles were immediately returned to the reactor.
This operation resulted in a particle size of 97.3% by mass with a particle size of 20-120 μm, 2.7% by mass with a particle size of less than 20 μm, and 65% by mass with a particle size of 20-44 μm. This is the same as extracting 259.7 g of the catalyst having a distribution out of the reactor. In addition, the extraction of this amount in 42 days means that 0.45 mass of particles in the range per day for the particles in the range of 20 to 44 μm in the catalyst present in the reactor. The amount corresponding to% is equivalent to that extracted from the reactor, and the amount is the same as in Example 1.

Together with the extraction operation, 259.7 g of catalyst (2) was supplied into the reactor. When this replenishment amount is converted per day, it is estimated that it corresponds to 0.25% by mass of the total catalyst present in the reactor, and this is the same as in Example 1.
As a result of analysis after removing the catalyst and replenishing the catalyst on the 42nd day, the yield of acrylonitrile was 81.3%.

[Example 6]
To 1915 parts of 20% by mass silica sol, 3.3 parts of 85% by mass phosphoric acid was added. A solution prepared by dissolving 212.5 parts of ammonium paramolybdate in 640 parts of water was added to this liquid with stirring, and the mixture was heated to 50 ° C. (solution C).
Separately, 105.2 parts of bismuth nitrate is dissolved in 105 parts of 10% by weight nitric acid, and 126.2 parts of cobalt nitrate, 62.8 parts of cerium nitrate, 87.6 parts of iron (III) nitrate, 2.9 parts of potassium nitrate are dissolved in this solution. And 312 parts of water were sequentially added and heated to 50 ° C. (solution D).

Separately, 930.5 parts of 61% by mass nitric acid was mixed with 843 parts of water, and 104.7 parts of electrolytic iron powder was added little by little to dissolve. To this solution, 324.4 parts of antimony trioxide was added and heated at 100 ° C. for 2 hours. Next, 10.2 parts of boric acid dissolved in 194 parts of water and 8.9 parts of 85% by mass phosphoric acid were added to this solution. The obtained liquid was dried, calcined at 950 ° C. for 3 hours, and further pulverized. 600 parts of water was added to 400 parts of the obtained pulverized product, and pulverized with a ball mill for 16 hours to obtain a liquid product and heated to 50 ° C. (solution E).
C and D were mixed with stirring, and then 831.1 parts of E was added to obtain a slurry.

The obtained aqueous slurry was dried using a spray dryer to obtain a spherical dry powder.
The obtained dried product was pre-calcined at 250 ° C. for 2 hours and then at 400 ° C. for 2 hours, and then calcined at 530 ° C. for 3 hours in a fluid calcination furnace to obtain a catalyst (3).
The composition of the obtained catalyst 3 was calculated from the raw material charge as follows.
Sb ₁₀ Mo _8.5 Fe ₁₀ Co ₃ Ce ₁ Bi _1.5 K _0.2 B _0.75 P _0.55 O _x (SiO ₂ ) ₄₅
(Here, x is the atomic ratio of oxygen necessary to satisfy the valences of the other components.)
As a result of examining the particle size distribution of the catalyst (3), the ratio of the particle size of 20 to 120 μm was 97.9 mass%, the ratio of the particle diameter of less than 20 μm was 2.1 mass%, and the ratio of the particle diameter of 20 to 44 μm was 32. It was 5 mass%.
Further, by sieving the catalyst (3), the ratio of the particle diameter of 20 to 120 μm is 97.7 mass%, the ratio of the particle diameter of less than 20 μm is 2.3 mass%, and the ratio of the particle diameter of 20 to 44 μm is 56. The catalyst (4) was obtained by adjusting the particle size distribution to mass%.
When 2500 g of catalyst (3) was charged into the reactor and acrylonitrile synthesis reaction was carried out, the acrylonitrile yield was 81.1%.

The reaction was continued for 35 days in a state where the cyclone collection efficiency was reduced by blowing an air flow upward from the bottom to the cyclone built in the reactor. In addition, all the catalysts that were entrained by the reaction gas and scattered outside the reactor due to the reduced cyclone collection efficiency were collected by a filter.
During the course of the reaction, 2.6 g of catalyst (4) was replenished into the reactor every day. When this replenishment amount is converted per day, it is estimated that the amount corresponds to 0.10% by mass of the total catalyst present in the reactor.

When the reaction was continued for 35 days, the total amount of catalyst scattered out of the reactor in the 35 days was 91 g, and the particle size distribution was 69% by mass with a particle size of 20 to 120 μm and a particle size of 20 μm. The ratio of less than 31% by mass and the ratio of the particle size of 20 to 44 μm was 68% by mass.
As a result, this method has a particle size distribution in which the proportion of the particle size of 20 to 120 μm is 69 mass%, the proportion of the particle size of less than 20 μm is 31 mass%, and the proportion of the particle size of 20 to 44 μm is 68 mass%. This is synonymous with the fact that 91 g of catalyst was continuously withdrawn from the reactor over 35 days. In addition, the extraction of this amount in 35 days means that the amount of particles in the range of 20 to 44 μm in the catalyst existing in the reactor is 0.22% by mass of the range of particles per day. This corresponds to the continuous extraction of the amount corresponding to.
As a result of analysis after the replenishment of the catalyst on the 35th day, the acrylonitrile yield was 80.5%.

[Comparative Example 3]
The catalyst (3) was obtained in the same manner as in Example 6, and the reaction was started in the same manner as in Example 6 without reducing the cyclone collection efficiency.
While the reaction was continued, 2.6 g of catalyst was withdrawn from the reactor every day and 2.6 g of catalyst (3) was replenished into the reactor.
That is, the catalyst having a particle size of 20 to 120 μm every day, 97.9% by mass, a particle size of less than 20 μm of 2.1% by mass, and a particle size of 20 to 44 μm of 32.5% by mass (3) The catalyst having the same particle size distribution as 2.6 g was extracted out of the reactor, and this was within the range of 20 to 44 μm in the catalyst existing in the reactor per day. This corresponds to the extraction of an amount corresponding to 0.10% by mass of the particles out of the reactor.

Further, when the catalyst replenishment amount is converted per day, it can be estimated as an amount corresponding to 0.10% by mass of the total catalyst present in the reactor.
In this way, the reaction was continuously performed for a total of 35 days while performing the operation of removing the catalyst and supplying the catalyst.
As a result of analysis after the replenishment of the catalyst on the 35th day, the acrylonitrile yield was 77.9%.

[Comparative Example 4]
A catalyst (3) was obtained in the same manner as in Example 6, and the reaction was started in the same manner as in Comparative Example 3.
While the reaction was continued, 42.5 g of catalyst was withdrawn from the reactor every day and 42.5 g of catalyst (3) was replenished into the reactor.
That is, the catalyst having a particle size of 20 to 120 μm every day, 97.9% by mass, a particle size of less than 20 μm of 2.1% by mass, and a particle size of 20 to 44 μm of 32.5% by mass (3) 42.5 g of the catalyst having the same particle size distribution was extracted out of the reactor, and this was within the range of 20 to 44 μm of the particles existing in the reactor per day. This corresponds to the extraction of an amount corresponding to 1.7% by mass of the particles out of the reactor.

Further, when the catalyst replenishment amount is converted per day, it can be estimated as an amount corresponding to 1.7% by mass of the total catalyst present in the reactor.
In this way, the reaction was continuously performed for a total of 35 days while performing the operation of removing the catalyst and supplying the catalyst.
As a result of analysis after the replenishment of the catalyst on the 35th day, the acrylonitrile yield was 80.5%.
Although this result is equivalent to Example 6, it requires a very large amount of replenishment catalyst as compared with Example 6, and can be said to be a significantly disadvantageous method economically.

  As described above, according to the method for producing acrylonitrile according to the present invention, a high acrylonitrile yield can be sustained over a long period of time and economically advantageously, and its industrial value is high.

It is a schematic block diagram which shows an example of the manufacturing apparatus of acrylonitrile. It is sectional drawing which shows an example of a source gas sparger nozzle hole. It is a perspective view which shows an example of a cyclone.

Explanation of symbols

1 Fluidized bed (particulate catalyst)
2 Reactor 3 Raw material gas sparger 4 Cyclone 5 Raw material gas sparger nozzle hole 6 Raw material gas 7 Dipreg 8 Discharge pipe

Claims (7)

In a method for producing acrylonitrile by reacting propylene, molecular oxygen and ammonia in a fluidized bed reactor containing a particulate catalyst,
As the particulate catalyst, the proportion of particles having a particle size of 20 to 120 μm is 85% by mass or more, the proportion of particles having a particle size of less than 20 μm is 5% by mass or less, and the particle size is in the range of 20 to 44 μm. Using a particle ratio of 25-40% by mass,
During the reaction, from the particulate catalyst in the reactor, particles having a particle size in the range of 20 to 44 μm are added to 0.05 to 1 mass of all particles having a particle size of 20 to 44 μm in the reactor per day. %, The proportion of particles having a particle size in the range of 20 to 120 μm is 85% by mass or more, the proportion of particles having a particle size of less than 20 μm is 5% by mass or less, and A particulate catalyst having a particle ratio of 41 to 80% by mass in the range of 20 to 44 μm in diameter is equivalent to 0.03 to 1% by mass of all the particulate catalysts in the reactor per day. A method for producing acrylonitrile, wherein the reactor is replenished from outside.   2. The method for producing acrylonitrile according to claim 1, wherein particles having a particle diameter of 20 to 44 [mu] m are continuously extracted from the reactor.   2. The method for producing acrylonitrile according to claim 1, wherein particles having a particle size in the range of 20 to 44 [mu] m are extracted from the reactor at a frequency of once every 1 to 30 days.   2. The process for producing acrylonitrile according to claim 1, wherein the particulate catalyst is continuously supplied from the outside of the reactor into the reactor.   The method for producing acrylonitrile according to claim 1, wherein the particulate catalyst is replenished from outside the reactor into the reactor at a frequency of once every 1 to 30 days. The method for producing acrylonitrile according to any one of claims 1 to 5, wherein a catalyst having a composition represented by the following general formula (1) is used as the particulate catalyst.
General formula (1):
_{Sb a Fe b C c D d} E e O f (SiO 2) g
(Wherein Sb, Fe and O represent antimony, iron and oxygen, respectively, C represents at least one element selected from the group consisting of cobalt, nickel, manganese, uranium, cerium, tin and copper; D Represents at least one element selected from the group consisting of molybdenum, vanadium and tungsten, and E represents magnesium, calcium, strontium, barium, lanthanum, titanium, zirconium, niobium, tantalum, chromium, rhenium, ruthenium, osmium, rhodium Selected from the group consisting of iridium, palladium, platinum, silver, zinc, cadmium, boron, aluminum, gallium, indium, sodium, potassium, rubidium, cesium, thallium, germanium, lead, phosphorus, arsenic, bismuth, selenium and tellurium Small Represents Kutomo one element, SiO ₂ represents silica, denotes a, b, c, d, e, f and g are atomic ratios of respective elements, and when a = 10, 1 ≦ b ≦ 20, (1 ≦ c ≦ 20, 0 ≦ d ≦ 20, 0 ≦ e ≦ 20, 10 ≦ g ≦ 200, and f is an atomic ratio of oxygen necessary to satisfy the valence of each component.) The method for producing acrylonitrile according to any one of claims 1 to 5, wherein a catalyst having a composition represented by the following general formula (2) is used as the particulate catalyst.
General formula (2):
Mo _{h B i} Fe _j F _k G _l O _m (SiO ₂ ) _n
(Wherein Mo, Bi, Fe and O represent molybdenum, bismuth, iron and oxygen, respectively, F represents at least one element selected from the group consisting of sodium, potassium, rubidium, cesium and thallium; Is cobalt, nickel, copper, zinc, magnesium, calcium, strontium, barium, titanium, vanadium, chromium, manganese, tungsten, silver, aluminum, phosphorus, boron, tin, lead, gallium, germanium, arsenic, antimony, niobium, tantalum At least one selected from the group consisting of zirconium, indium, sulfur, selenium, tellurium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, holmium, erbium, thulium and ytterbium Represent elements, SiO ₂ represents silica, represents h, i, j, k, l, m and n are the atomic ratios of respective elements, and when h = 12, 0.1 ≦ i ≦ 5,0. 1 ≦ j ≦ 10, 0.01 ≦ k ≦ 3, 0 ≦ l ≦ 20, 10 ≦ n ≦ 200, and m is an atomic ratio of oxygen necessary to satisfy the valence of each component. )

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